Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost

[linux.git] / drivers / gpu / drm / drm_atomic_helper.c

/*
 * Copyright (C) 2014 Red Hat
 * Copyright (C) 2014 Intel Corp.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 *
 * Authors:
 * Rob Clark <[email protected]>
 * Daniel Vetter <[email protected]>
 */

#include <linux/dma-fence.h>
#include <linux/ktime.h>

#include <drm/drm_atomic.h>
#include <drm/drm_atomic_helper.h>
#include <drm/drm_atomic_uapi.h>
#include <drm/drm_blend.h>
#include <drm/drm_bridge.h>
#include <drm/drm_damage_helper.h>
#include <drm/drm_device.h>
#include <drm/drm_drv.h>
#include <drm/drm_framebuffer.h>
#include <drm/drm_gem_atomic_helper.h>
#include <drm/drm_plane_helper.h>
#include <drm/drm_print.h>
#include <drm/drm_self_refresh_helper.h>
#include <drm/drm_vblank.h>
#include <drm/drm_writeback.h>

#include "drm_crtc_helper_internal.h"
#include "drm_crtc_internal.h"

/**
 * DOC: overview
 *
 * This helper library provides implementations of check and commit functions on
 * top of the CRTC modeset helper callbacks and the plane helper callbacks. It
 * also provides convenience implementations for the atomic state handling
 * callbacks for drivers which don't need to subclass the drm core structures to
 * add their own additional internal state.
 *
 * This library also provides default implementations for the check callback in
 * drm_atomic_helper_check() and for the commit callback with
 * drm_atomic_helper_commit(). But the individual stages and callbacks are
 * exposed to allow drivers to mix and match and e.g. use the plane helpers only
 * together with a driver private modeset implementation.
 *
 * This library also provides implementations for all the legacy driver
 * interfaces on top of the atomic interface. See drm_atomic_helper_set_config(),
 * drm_atomic_helper_disable_plane(), and the various functions to implement
 * set_property callbacks. New drivers must not implement these functions
 * themselves but must use the provided helpers.
 *
 * The atomic helper uses the same function table structures as all other
 * modesetting helpers. See the documentation for &struct drm_crtc_helper_funcs,
 * struct &drm_encoder_helper_funcs and &struct drm_connector_helper_funcs. It
 * also shares the &struct drm_plane_helper_funcs function table with the plane
 * helpers.
 */
static void
drm_atomic_helper_plane_changed(struct drm_atomic_state *state,
                                struct drm_plane_state *old_plane_state,
                                struct drm_plane_state *plane_state,
                                struct drm_plane *plane)
{
        struct drm_crtc_state *crtc_state;

        if (old_plane_state->crtc) {
                crtc_state = drm_atomic_get_new_crtc_state(state,
                                                           old_plane_state->crtc);

                if (WARN_ON(!crtc_state))
                        return;

                crtc_state->planes_changed = true;
        }

        if (plane_state->crtc) {
                crtc_state = drm_atomic_get_new_crtc_state(state, plane_state->crtc);

                if (WARN_ON(!crtc_state))
                        return;

                crtc_state->planes_changed = true;
        }
}

static int handle_conflicting_encoders(struct drm_atomic_state *state,
                                       bool disable_conflicting_encoders)
{
        struct drm_connector_state *new_conn_state;
        struct drm_connector *connector;
        struct drm_connector_list_iter conn_iter;
        struct drm_encoder *encoder;
        unsigned int encoder_mask = 0;
        int i, ret = 0;

        /*
         * First loop, find all newly assigned encoders from the connectors
         * part of the state. If the same encoder is assigned to multiple
         * connectors bail out.
         */
        for_each_new_connector_in_state(state, connector, new_conn_state, i) {
                const struct drm_connector_helper_funcs *funcs = connector->helper_private;
                struct drm_encoder *new_encoder;

                if (!new_conn_state->crtc)
                        continue;

                if (funcs->atomic_best_encoder)
                        new_encoder = funcs->atomic_best_encoder(connector,
                                                                 state);
                else if (funcs->best_encoder)
                        new_encoder = funcs->best_encoder(connector);
                else
                        new_encoder = drm_connector_get_single_encoder(connector);

                if (new_encoder) {
                        if (encoder_mask & drm_encoder_mask(new_encoder)) {
                                drm_dbg_atomic(connector->dev,
                                               "[ENCODER:%d:%s] on [CONNECTOR:%d:%s] already assigned\n",
                                               new_encoder->base.id, new_encoder->name,
                                               connector->base.id, connector->name);

                                return -EINVAL;
                        }

                        encoder_mask |= drm_encoder_mask(new_encoder);
                }
        }

        if (!encoder_mask)
                return 0;

        /*
         * Second loop, iterate over all connectors not part of the state.
         *
         * If a conflicting encoder is found and disable_conflicting_encoders
         * is not set, an error is returned. Userspace can provide a solution
         * through the atomic ioctl.
         *
         * If the flag is set conflicting connectors are removed from the CRTC
         * and the CRTC is disabled if no encoder is left. This preserves
         * compatibility with the legacy set_config behavior.
         */
        drm_connector_list_iter_begin(state->dev, &conn_iter);
        drm_for_each_connector_iter(connector, &conn_iter) {
                struct drm_crtc_state *crtc_state;

                if (drm_atomic_get_new_connector_state(state, connector))
                        continue;

                encoder = connector->state->best_encoder;
                if (!encoder || !(encoder_mask & drm_encoder_mask(encoder)))
                        continue;

                if (!disable_conflicting_encoders) {
                        drm_dbg_atomic(connector->dev,
                                       "[ENCODER:%d:%s] in use on [CRTC:%d:%s] by [CONNECTOR:%d:%s]\n",
                                       encoder->base.id, encoder->name,
                                       connector->state->crtc->base.id,
                                       connector->state->crtc->name,
                                       connector->base.id, connector->name);
                        ret = -EINVAL;
                        goto out;
                }

                new_conn_state = drm_atomic_get_connector_state(state, connector);
                if (IS_ERR(new_conn_state)) {
                        ret = PTR_ERR(new_conn_state);
                        goto out;
                }

                drm_dbg_atomic(connector->dev,
                               "[ENCODER:%d:%s] in use on [CRTC:%d:%s], disabling [CONNECTOR:%d:%s]\n",
                               encoder->base.id, encoder->name,
                               new_conn_state->crtc->base.id, new_conn_state->crtc->name,
                               connector->base.id, connector->name);

                crtc_state = drm_atomic_get_new_crtc_state(state, new_conn_state->crtc);

                ret = drm_atomic_set_crtc_for_connector(new_conn_state, NULL);
                if (ret)
                        goto out;

                if (!crtc_state->connector_mask) {
                        ret = drm_atomic_set_mode_prop_for_crtc(crtc_state,
                                                                NULL);
                        if (ret < 0)
                                goto out;

                        crtc_state->active = false;
                }
        }
out:
        drm_connector_list_iter_end(&conn_iter);

        return ret;
}

static void
set_best_encoder(struct drm_atomic_state *state,
                 struct drm_connector_state *conn_state,
                 struct drm_encoder *encoder)
{
        struct drm_crtc_state *crtc_state;
        struct drm_crtc *crtc;

        if (conn_state->best_encoder) {
                /* Unset the encoder_mask in the old crtc state. */
                crtc = conn_state->connector->state->crtc;

                /* A NULL crtc is an error here because we should have
                 * duplicated a NULL best_encoder when crtc was NULL.
                 * As an exception restoring duplicated atomic state
                 * during resume is allowed, so don't warn when
                 * best_encoder is equal to encoder we intend to set.
                 */
                WARN_ON(!crtc && encoder != conn_state->best_encoder);
                if (crtc) {
                        crtc_state = drm_atomic_get_new_crtc_state(state, crtc);

                        crtc_state->encoder_mask &=
                                ~drm_encoder_mask(conn_state->best_encoder);
                }
        }

        if (encoder) {
                crtc = conn_state->crtc;
                WARN_ON(!crtc);
                if (crtc) {
                        crtc_state = drm_atomic_get_new_crtc_state(state, crtc);

                        crtc_state->encoder_mask |=
                                drm_encoder_mask(encoder);
                }
        }

        conn_state->best_encoder = encoder;
}

static void
steal_encoder(struct drm_atomic_state *state,
              struct drm_encoder *encoder)
{
        struct drm_crtc_state *crtc_state;
        struct drm_connector *connector;
        struct drm_connector_state *old_connector_state, *new_connector_state;
        int i;

        for_each_oldnew_connector_in_state(state, connector, old_connector_state, new_connector_state, i) {
                struct drm_crtc *encoder_crtc;

                if (new_connector_state->best_encoder != encoder)
                        continue;

                encoder_crtc = old_connector_state->crtc;

                drm_dbg_atomic(encoder->dev,
                               "[ENCODER:%d:%s] in use on [CRTC:%d:%s], stealing it\n",
                               encoder->base.id, encoder->name,
                               encoder_crtc->base.id, encoder_crtc->name);

                set_best_encoder(state, new_connector_state, NULL);

                crtc_state = drm_atomic_get_new_crtc_state(state, encoder_crtc);
                crtc_state->connectors_changed = true;

                return;
        }
}

static int
update_connector_routing(struct drm_atomic_state *state,
                         struct drm_connector *connector,
                         struct drm_connector_state *old_connector_state,
                         struct drm_connector_state *new_connector_state)
{
        const struct drm_connector_helper_funcs *funcs;
        struct drm_encoder *new_encoder;
        struct drm_crtc_state *crtc_state;

        drm_dbg_atomic(connector->dev, "Updating routing for [CONNECTOR:%d:%s]\n",
                       connector->base.id, connector->name);

        if (old_connector_state->crtc != new_connector_state->crtc) {
                if (old_connector_state->crtc) {
                        crtc_state = drm_atomic_get_new_crtc_state(state, old_connector_state->crtc);
                        crtc_state->connectors_changed = true;
                }

                if (new_connector_state->crtc) {
                        crtc_state = drm_atomic_get_new_crtc_state(state, new_connector_state->crtc);
                        crtc_state->connectors_changed = true;
                }
        }

        if (!new_connector_state->crtc) {
                drm_dbg_atomic(connector->dev, "Disabling [CONNECTOR:%d:%s]\n",
                                connector->base.id, connector->name);

                set_best_encoder(state, new_connector_state, NULL);

                return 0;
        }

        crtc_state = drm_atomic_get_new_crtc_state(state,
                                                   new_connector_state->crtc);
        /*
         * For compatibility with legacy users, we want to make sure that
         * we allow DPMS On->Off modesets on unregistered connectors. Modesets
         * which would result in anything else must be considered invalid, to
         * avoid turning on new displays on dead connectors.
         *
         * Since the connector can be unregistered at any point during an
         * atomic check or commit, this is racy. But that's OK: all we care
         * about is ensuring that userspace can't do anything but shut off the
         * display on a connector that was destroyed after it's been notified,
         * not before.
         *
         * Additionally, we also want to ignore connector registration when
         * we're trying to restore an atomic state during system resume since
         * there's a chance the connector may have been destroyed during the
         * process, but it's better to ignore that then cause
         * drm_atomic_helper_resume() to fail.
         */
        if (!state->duplicated && drm_connector_is_unregistered(connector) &&
            crtc_state->active) {
                drm_dbg_atomic(connector->dev,
                               "[CONNECTOR:%d:%s] is not registered\n",
                               connector->base.id, connector->name);
                return -EINVAL;
        }

        funcs = connector->helper_private;

        if (funcs->atomic_best_encoder)
                new_encoder = funcs->atomic_best_encoder(connector, state);
        else if (funcs->best_encoder)
                new_encoder = funcs->best_encoder(connector);
        else
                new_encoder = drm_connector_get_single_encoder(connector);

        if (!new_encoder) {
                drm_dbg_atomic(connector->dev,
                               "No suitable encoder found for [CONNECTOR:%d:%s]\n",
                               connector->base.id, connector->name);
                return -EINVAL;
        }

        if (!drm_encoder_crtc_ok(new_encoder, new_connector_state->crtc)) {
                drm_dbg_atomic(connector->dev,
                               "[ENCODER:%d:%s] incompatible with [CRTC:%d:%s]\n",
                               new_encoder->base.id,
                               new_encoder->name,
                               new_connector_state->crtc->base.id,
                               new_connector_state->crtc->name);
                return -EINVAL;
        }

        if (new_encoder == new_connector_state->best_encoder) {
                set_best_encoder(state, new_connector_state, new_encoder);

                drm_dbg_atomic(connector->dev,
                               "[CONNECTOR:%d:%s] keeps [ENCODER:%d:%s], now on [CRTC:%d:%s]\n",
                               connector->base.id,
                               connector->name,
                               new_encoder->base.id,
                               new_encoder->name,
                               new_connector_state->crtc->base.id,
                               new_connector_state->crtc->name);

                return 0;
        }

        steal_encoder(state, new_encoder);

        set_best_encoder(state, new_connector_state, new_encoder);

        crtc_state->connectors_changed = true;

        drm_dbg_atomic(connector->dev,
                       "[CONNECTOR:%d:%s] using [ENCODER:%d:%s] on [CRTC:%d:%s]\n",
                       connector->base.id,
                       connector->name,
                       new_encoder->base.id,
                       new_encoder->name,
                       new_connector_state->crtc->base.id,
                       new_connector_state->crtc->name);

        return 0;
}

static int
mode_fixup(struct drm_atomic_state *state)
{
        struct drm_crtc *crtc;
        struct drm_crtc_state *new_crtc_state;
        struct drm_connector *connector;
        struct drm_connector_state *new_conn_state;
        int i;
        int ret;

        for_each_new_crtc_in_state(state, crtc, new_crtc_state, i) {
                if (!new_crtc_state->mode_changed &&
                    !new_crtc_state->connectors_changed)
                        continue;

                drm_mode_copy(&new_crtc_state->adjusted_mode, &new_crtc_state->mode);
        }

        for_each_new_connector_in_state(state, connector, new_conn_state, i) {
                const struct drm_encoder_helper_funcs *funcs;
                struct drm_encoder *encoder;
                struct drm_bridge *bridge;

                WARN_ON(!!new_conn_state->best_encoder != !!new_conn_state->crtc);

                if (!new_conn_state->crtc || !new_conn_state->best_encoder)
                        continue;

                new_crtc_state =
                        drm_atomic_get_new_crtc_state(state, new_conn_state->crtc);

                /*
                 * Each encoder has at most one connector (since we always steal
                 * it away), so we won't call ->mode_fixup twice.
                 */
                encoder = new_conn_state->best_encoder;
                funcs = encoder->helper_private;

                bridge = drm_bridge_chain_get_first_bridge(encoder);
                ret = drm_atomic_bridge_chain_check(bridge,
                                                    new_crtc_state,
                                                    new_conn_state);
                if (ret) {
                        drm_dbg_atomic(encoder->dev, "Bridge atomic check failed\n");
                        return ret;
                }

                if (funcs && funcs->atomic_check) {
                        ret = funcs->atomic_check(encoder, new_crtc_state,
                                                  new_conn_state);
                        if (ret) {
                                drm_dbg_atomic(encoder->dev,
                                               "[ENCODER:%d:%s] check failed\n",
                                               encoder->base.id, encoder->name);
                                return ret;
                        }
                } else if (funcs && funcs->mode_fixup) {
                        ret = funcs->mode_fixup(encoder, &new_crtc_state->mode,
                                                &new_crtc_state->adjusted_mode);
                        if (!ret) {
                                drm_dbg_atomic(encoder->dev,
                                               "[ENCODER:%d:%s] fixup failed\n",
                                               encoder->base.id, encoder->name);
                                return -EINVAL;
                        }
                }
        }

        for_each_new_crtc_in_state(state, crtc, new_crtc_state, i) {
                const struct drm_crtc_helper_funcs *funcs;

                if (!new_crtc_state->enable)
                        continue;

                if (!new_crtc_state->mode_changed &&
                    !new_crtc_state->connectors_changed)
                        continue;

                funcs = crtc->helper_private;
                if (!funcs || !funcs->mode_fixup)
                        continue;

                ret = funcs->mode_fixup(crtc, &new_crtc_state->mode,
                                        &new_crtc_state->adjusted_mode);
                if (!ret) {
                        drm_dbg_atomic(crtc->dev, "[CRTC:%d:%s] fixup failed\n",
                                       crtc->base.id, crtc->name);
                        return -EINVAL;
                }
        }

        return 0;
}

static enum drm_mode_status mode_valid_path(struct drm_connector *connector,
                                            struct drm_encoder *encoder,
                                            struct drm_crtc *crtc,
                                            const struct drm_display_mode *mode)
{
        struct drm_bridge *bridge;
        enum drm_mode_status ret;

        ret = drm_encoder_mode_valid(encoder, mode);
        if (ret != MODE_OK) {
                drm_dbg_atomic(encoder->dev,
                               "[ENCODER:%d:%s] mode_valid() failed\n",
                               encoder->base.id, encoder->name);
                return ret;
        }

        bridge = drm_bridge_chain_get_first_bridge(encoder);
        ret = drm_bridge_chain_mode_valid(bridge, &connector->display_info,
                                          mode);
        if (ret != MODE_OK) {
                drm_dbg_atomic(encoder->dev, "[BRIDGE] mode_valid() failed\n");
                return ret;
        }

        ret = drm_crtc_mode_valid(crtc, mode);
        if (ret != MODE_OK) {
                drm_dbg_atomic(encoder->dev, "[CRTC:%d:%s] mode_valid() failed\n",
                               crtc->base.id, crtc->name);
                return ret;
        }

        return ret;
}

static int
mode_valid(struct drm_atomic_state *state)
{
        struct drm_connector_state *conn_state;
        struct drm_connector *connector;
        int i;

        for_each_new_connector_in_state(state, connector, conn_state, i) {
                struct drm_encoder *encoder = conn_state->best_encoder;
                struct drm_crtc *crtc = conn_state->crtc;
                struct drm_crtc_state *crtc_state;
                enum drm_mode_status mode_status;
                const struct drm_display_mode *mode;

                if (!crtc || !encoder)
                        continue;

                crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
                if (!crtc_state)
                        continue;
                if (!crtc_state->mode_changed && !crtc_state->connectors_changed)
                        continue;

                mode = &crtc_state->mode;

                mode_status = mode_valid_path(connector, encoder, crtc, mode);
                if (mode_status != MODE_OK)
                        return -EINVAL;
        }

        return 0;
}

/**
 * drm_atomic_helper_check_modeset - validate state object for modeset changes
 * @dev: DRM device
 * @state: the driver state object
 *
 * Check the state object to see if the requested state is physically possible.
 * This does all the CRTC and connector related computations for an atomic
 * update and adds any additional connectors needed for full modesets. It calls
 * the various per-object callbacks in the follow order:
 *
 * 1. &drm_connector_helper_funcs.atomic_best_encoder for determining the new encoder.
 * 2. &drm_connector_helper_funcs.atomic_check to validate the connector state.
 * 3. If it's determined a modeset is needed then all connectors on the affected
 *    CRTC are added and &drm_connector_helper_funcs.atomic_check is run on them.
 * 4. &drm_encoder_helper_funcs.mode_valid, &drm_bridge_funcs.mode_valid and
 *    &drm_crtc_helper_funcs.mode_valid are called on the affected components.
 * 5. &drm_bridge_funcs.mode_fixup is called on all encoder bridges.
 * 6. &drm_encoder_helper_funcs.atomic_check is called to validate any encoder state.
 *    This function is only called when the encoder will be part of a configured CRTC,
 *    it must not be used for implementing connector property validation.
 *    If this function is NULL, &drm_atomic_encoder_helper_funcs.mode_fixup is called
 *    instead.
 * 7. &drm_crtc_helper_funcs.mode_fixup is called last, to fix up the mode with CRTC constraints.
 *
 * &drm_crtc_state.mode_changed is set when the input mode is changed.
 * &drm_crtc_state.connectors_changed is set when a connector is added or
 * removed from the CRTC.  &drm_crtc_state.active_changed is set when
 * &drm_crtc_state.active changes, which is used for DPMS.
 * &drm_crtc_state.no_vblank is set from the result of drm_dev_has_vblank().
 * See also: drm_atomic_crtc_needs_modeset()
 *
 * IMPORTANT:
 *
 * Drivers which set &drm_crtc_state.mode_changed (e.g. in their
 * &drm_plane_helper_funcs.atomic_check hooks if a plane update can't be done
 * without a full modeset) _must_ call this function after that change. It is
 * permitted to call this function multiple times for the same update, e.g.
 * when the &drm_crtc_helper_funcs.atomic_check functions depend upon the
 * adjusted dotclock for fifo space allocation and watermark computation.
 *
 * RETURNS:
 * Zero for success or -errno
 */
int
drm_atomic_helper_check_modeset(struct drm_device *dev,
                                struct drm_atomic_state *state)
{
        struct drm_crtc *crtc;
        struct drm_crtc_state *old_crtc_state, *new_crtc_state;
        struct drm_connector *connector;
        struct drm_connector_state *old_connector_state, *new_connector_state;
        int i, ret;
        unsigned int connectors_mask = 0;

        for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) {
                bool has_connectors =
                        !!new_crtc_state->connector_mask;

                WARN_ON(!drm_modeset_is_locked(&crtc->mutex));

                if (!drm_mode_equal(&old_crtc_state->mode, &new_crtc_state->mode)) {
                        drm_dbg_atomic(dev, "[CRTC:%d:%s] mode changed\n",
                                       crtc->base.id, crtc->name);
                        new_crtc_state->mode_changed = true;
                }

                if (old_crtc_state->enable != new_crtc_state->enable) {
                        drm_dbg_atomic(dev, "[CRTC:%d:%s] enable changed\n",
                                       crtc->base.id, crtc->name);

                        /*
                         * For clarity this assignment is done here, but
                         * enable == 0 is only true when there are no
                         * connectors and a NULL mode.
                         *
                         * The other way around is true as well. enable != 0
                         * implies that connectors are attached and a mode is set.
                         */
                        new_crtc_state->mode_changed = true;
                        new_crtc_state->connectors_changed = true;
                }

                if (old_crtc_state->active != new_crtc_state->active) {
                        drm_dbg_atomic(dev, "[CRTC:%d:%s] active changed\n",
                                       crtc->base.id, crtc->name);
                        new_crtc_state->active_changed = true;
                }

                if (new_crtc_state->enable != has_connectors) {
                        drm_dbg_atomic(dev, "[CRTC:%d:%s] enabled/connectors mismatch\n",
                                       crtc->base.id, crtc->name);

                        return -EINVAL;
                }

                if (drm_dev_has_vblank(dev))
                        new_crtc_state->no_vblank = false;
                else
                        new_crtc_state->no_vblank = true;
        }

        ret = handle_conflicting_encoders(state, false);
        if (ret)
                return ret;

        for_each_oldnew_connector_in_state(state, connector, old_connector_state, new_connector_state, i) {
                const struct drm_connector_helper_funcs *funcs = connector->helper_private;

                WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));

                /*
                 * This only sets crtc->connectors_changed for routing changes,
                 * drivers must set crtc->connectors_changed themselves when
                 * connector properties need to be updated.
                 */
                ret = update_connector_routing(state, connector,
                                               old_connector_state,
                                               new_connector_state);
                if (ret)
                        return ret;
                if (old_connector_state->crtc) {
                        new_crtc_state = drm_atomic_get_new_crtc_state(state,
                                                                       old_connector_state->crtc);
                        if (old_connector_state->link_status !=
                            new_connector_state->link_status)
                                new_crtc_state->connectors_changed = true;

                        if (old_connector_state->max_requested_bpc !=
                            new_connector_state->max_requested_bpc)
                                new_crtc_state->connectors_changed = true;
                }

                if (funcs->atomic_check)
                        ret = funcs->atomic_check(connector, state);
                if (ret)
                        return ret;

                connectors_mask |= BIT(i);
        }

        /*
         * After all the routing has been prepared we need to add in any
         * connector which is itself unchanged, but whose CRTC changes its
         * configuration. This must be done before calling mode_fixup in case a
         * crtc only changed its mode but has the same set of connectors.
         */
        for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) {
                if (!drm_atomic_crtc_needs_modeset(new_crtc_state))
                        continue;

                drm_dbg_atomic(dev,
                               "[CRTC:%d:%s] needs all connectors, enable: %c, active: %c\n",
                               crtc->base.id, crtc->name,
                               new_crtc_state->enable ? 'y' : 'n',
                               new_crtc_state->active ? 'y' : 'n');

                ret = drm_atomic_add_affected_connectors(state, crtc);
                if (ret != 0)
                        return ret;

                ret = drm_atomic_add_affected_planes(state, crtc);
                if (ret != 0)
                        return ret;
        }

        /*
         * Iterate over all connectors again, to make sure atomic_check()
         * has been called on them when a modeset is forced.
         */
        for_each_oldnew_connector_in_state(state, connector, old_connector_state, new_connector_state, i) {
                const struct drm_connector_helper_funcs *funcs = connector->helper_private;

                if (connectors_mask & BIT(i))
                        continue;

                if (funcs->atomic_check)
                        ret = funcs->atomic_check(connector, state);
                if (ret)
                        return ret;
        }

        /*
         * Iterate over all connectors again, and add all affected bridges to
         * the state.
         */
        for_each_oldnew_connector_in_state(state, connector,
                                           old_connector_state,
                                           new_connector_state, i) {
                struct drm_encoder *encoder;

                encoder = old_connector_state->best_encoder;
                ret = drm_atomic_add_encoder_bridges(state, encoder);
                if (ret)
                        return ret;

                encoder = new_connector_state->best_encoder;
                ret = drm_atomic_add_encoder_bridges(state, encoder);
                if (ret)
                        return ret;
        }

        ret = mode_valid(state);
        if (ret)
                return ret;

        return mode_fixup(state);
}
EXPORT_SYMBOL(drm_atomic_helper_check_modeset);

/**
 * drm_atomic_helper_check_plane_state() - Check plane state for validity
 * @plane_state: plane state to check
 * @crtc_state: CRTC state to check
 * @min_scale: minimum @src:@dest scaling factor in 16.16 fixed point
 * @max_scale: maximum @src:@dest scaling factor in 16.16 fixed point
 * @can_position: is it legal to position the plane such that it
 *                doesn't cover the entire CRTC?  This will generally
 *                only be false for primary planes.
 * @can_update_disabled: can the plane be updated while the CRTC
 *                       is disabled?
 *
 * Checks that a desired plane update is valid, and updates various
 * bits of derived state (clipped coordinates etc.). Drivers that provide
 * their own plane handling rather than helper-provided implementations may
 * still wish to call this function to avoid duplication of error checking
 * code.
 *
 * RETURNS:
 * Zero if update appears valid, error code on failure
 */
int drm_atomic_helper_check_plane_state(struct drm_plane_state *plane_state,
                                        const struct drm_crtc_state *crtc_state,
                                        int min_scale,
                                        int max_scale,
                                        bool can_position,
                                        bool can_update_disabled)
{
        struct drm_framebuffer *fb = plane_state->fb;
        struct drm_rect *src = &plane_state->src;
        struct drm_rect *dst = &plane_state->dst;
        unsigned int rotation = plane_state->rotation;
        struct drm_rect clip = {};
        int hscale, vscale;

        WARN_ON(plane_state->crtc && plane_state->crtc != crtc_state->crtc);

        *src = drm_plane_state_src(plane_state);
        *dst = drm_plane_state_dest(plane_state);

        if (!fb) {
                plane_state->visible = false;
                return 0;
        }

        /* crtc should only be NULL when disabling (i.e., !fb) */
        if (WARN_ON(!plane_state->crtc)) {
                plane_state->visible = false;
                return 0;
        }

        if (!crtc_state->enable && !can_update_disabled) {
                drm_dbg_kms(plane_state->plane->dev,
                            "Cannot update plane of a disabled CRTC.\n");
                return -EINVAL;
        }

        drm_rect_rotate(src, fb->width << 16, fb->height << 16, rotation);

        /* Check scaling */
        hscale = drm_rect_calc_hscale(src, dst, min_scale, max_scale);
        vscale = drm_rect_calc_vscale(src, dst, min_scale, max_scale);
        if (hscale < 0 || vscale < 0) {
                drm_dbg_kms(plane_state->plane->dev,
                            "Invalid scaling of plane\n");
                drm_rect_debug_print("src: ", &plane_state->src, true);
                drm_rect_debug_print("dst: ", &plane_state->dst, false);
                return -ERANGE;
        }

        if (crtc_state->enable)
                drm_mode_get_hv_timing(&crtc_state->mode, &clip.x2, &clip.y2);

        plane_state->visible = drm_rect_clip_scaled(src, dst, &clip);

        drm_rect_rotate_inv(src, fb->width << 16, fb->height << 16, rotation);

        if (!plane_state->visible)
                /*
                 * Plane isn't visible; some drivers can handle this
                 * so we just return success here.  Drivers that can't
                 * (including those that use the primary plane helper's
                 * update function) will return an error from their
                 * update_plane handler.
                 */
                return 0;

        if (!can_position && !drm_rect_equals(dst, &clip)) {
                drm_dbg_kms(plane_state->plane->dev,
                            "Plane must cover entire CRTC\n");
                drm_rect_debug_print("dst: ", dst, false);
                drm_rect_debug_print("clip: ", &clip, false);
                return -EINVAL;
        }

        return 0;
}
EXPORT_SYMBOL(drm_atomic_helper_check_plane_state);

/**
 * drm_atomic_helper_check_crtc_state() - Check CRTC state for validity
 * @crtc_state: CRTC state to check
 * @can_disable_primary_planes: can the CRTC be enabled without a primary plane?
 *
 * Checks that a desired CRTC update is valid. Drivers that provide
 * their own CRTC handling rather than helper-provided implementations may
 * still wish to call this function to avoid duplication of error checking
 * code.
 *
 * Note that @can_disable_primary_planes only tests if the CRTC can be
 * enabled without a primary plane. To test if a primary plane can be updated
 * without a CRTC, use drm_atomic_helper_check_plane_state() in the plane's
 * atomic check.
 *
 * RETURNS:
 * Zero if update appears valid, error code on failure
 */
int drm_atomic_helper_check_crtc_state(struct drm_crtc_state *crtc_state,
                                       bool can_disable_primary_planes)
{
        struct drm_device *dev = crtc_state->crtc->dev;
        struct drm_atomic_state *state = crtc_state->state;

        if (!crtc_state->enable)
                return 0;

        /* needs at least one primary plane to be enabled */
        if (!can_disable_primary_planes) {
                bool has_primary_plane = false;
                struct drm_plane *plane;

                drm_for_each_plane_mask(plane, dev, crtc_state->plane_mask) {
                        struct drm_plane_state *plane_state;

                        if (plane->type != DRM_PLANE_TYPE_PRIMARY)
                                continue;
                        plane_state = drm_atomic_get_plane_state(state, plane);
                        if (IS_ERR(plane_state))
                                return PTR_ERR(plane_state);
                        if (plane_state->fb && plane_state->crtc) {
                                has_primary_plane = true;
                                break;
                        }
                }
                if (!has_primary_plane) {
                        drm_dbg_kms(dev, "Cannot enable CRTC without a primary plane.\n");
                        return -EINVAL;
                }
        }

        return 0;
}
EXPORT_SYMBOL(drm_atomic_helper_check_crtc_state);

/**
 * drm_atomic_helper_check_planes - validate state object for planes changes
 * @dev: DRM device
 * @state: the driver state object
 *
 * Check the state object to see if the requested state is physically possible.
 * This does all the plane update related checks using by calling into the
 * &drm_crtc_helper_funcs.atomic_check and &drm_plane_helper_funcs.atomic_check
 * hooks provided by the driver.
 *
 * It also sets &drm_crtc_state.planes_changed to indicate that a CRTC has
 * updated planes.
 *
 * RETURNS:
 * Zero for success or -errno
 */
int
drm_atomic_helper_check_planes(struct drm_device *dev,
                               struct drm_atomic_state *state)
{
        struct drm_crtc *crtc;
        struct drm_crtc_state *new_crtc_state;
        struct drm_plane *plane;
        struct drm_plane_state *new_plane_state, *old_plane_state;
        int i, ret = 0;

        for_each_oldnew_plane_in_state(state, plane, old_plane_state, new_plane_state, i) {
                const struct drm_plane_helper_funcs *funcs;

                WARN_ON(!drm_modeset_is_locked(&plane->mutex));

                funcs = plane->helper_private;

                drm_atomic_helper_plane_changed(state, old_plane_state, new_plane_state, plane);

                drm_atomic_helper_check_plane_damage(state, new_plane_state);

                if (!funcs || !funcs->atomic_check)
                        continue;

                ret = funcs->atomic_check(plane, state);
                if (ret) {
                        drm_dbg_atomic(plane->dev,
                                       "[PLANE:%d:%s] atomic driver check failed\n",
                                       plane->base.id, plane->name);
                        return ret;
                }
        }

        for_each_new_crtc_in_state(state, crtc, new_crtc_state, i) {
                const struct drm_crtc_helper_funcs *funcs;

                funcs = crtc->helper_private;

                if (!funcs || !funcs->atomic_check)
                        continue;

                ret = funcs->atomic_check(crtc, state);
                if (ret) {
                        drm_dbg_atomic(crtc->dev,
                                       "[CRTC:%d:%s] atomic driver check failed\n",
                                       crtc->base.id, crtc->name);
                        return ret;
                }
        }

        return ret;
}
EXPORT_SYMBOL(drm_atomic_helper_check_planes);

/**
 * drm_atomic_helper_check - validate state object
 * @dev: DRM device
 * @state: the driver state object
 *
 * Check the state object to see if the requested state is physically possible.
 * Only CRTCs and planes have check callbacks, so for any additional (global)
 * checking that a driver needs it can simply wrap that around this function.
 * Drivers without such needs can directly use this as their
 * &drm_mode_config_funcs.atomic_check callback.
 *
 * This just wraps the two parts of the state checking for planes and modeset
 * state in the default order: First it calls drm_atomic_helper_check_modeset()
 * and then drm_atomic_helper_check_planes(). The assumption is that the
 * @drm_plane_helper_funcs.atomic_check and @drm_crtc_helper_funcs.atomic_check
 * functions depend upon an updated adjusted_mode.clock to e.g. properly compute
 * watermarks.
 *
 * Note that zpos normalization will add all enable planes to the state which
 * might not desired for some drivers.
 * For example enable/disable of a cursor plane which have fixed zpos value
 * would trigger all other enabled planes to be forced to the state change.
 *
 * RETURNS:
 * Zero for success or -errno
 */
int drm_atomic_helper_check(struct drm_device *dev,
                            struct drm_atomic_state *state)
{
        int ret;

        ret = drm_atomic_helper_check_modeset(dev, state);
        if (ret)
                return ret;

        if (dev->mode_config.normalize_zpos) {
                ret = drm_atomic_normalize_zpos(dev, state);
                if (ret)
                        return ret;
        }

        ret = drm_atomic_helper_check_planes(dev, state);
        if (ret)
                return ret;

        if (state->legacy_cursor_update)
                state->async_update = !drm_atomic_helper_async_check(dev, state);

        drm_self_refresh_helper_alter_state(state);

        return ret;
}
EXPORT_SYMBOL(drm_atomic_helper_check);

static bool
crtc_needs_disable(struct drm_crtc_state *old_state,
                   struct drm_crtc_state *new_state)
{
        /*
         * No new_state means the CRTC is off, so the only criteria is whether
         * it's currently active or in self refresh mode.
         */
        if (!new_state)
                return drm_atomic_crtc_effectively_active(old_state);

        /*
         * We need to disable bridge(s) and CRTC if we're transitioning out of
         * self-refresh and changing CRTCs at the same time, because the
         * bridge tracks self-refresh status via CRTC state.
         */
        if (old_state->self_refresh_active &&
            old_state->crtc != new_state->crtc)
                return true;

        /*
         * We also need to run through the crtc_funcs->disable() function if
         * the CRTC is currently on, if it's transitioning to self refresh
         * mode, or if it's in self refresh mode and needs to be fully
         * disabled.
         */
        return old_state->active ||
               (old_state->self_refresh_active && !new_state->active) ||
               new_state->self_refresh_active;
}

static void
disable_outputs(struct drm_device *dev, struct drm_atomic_state *old_state)
{
        struct drm_connector *connector;
        struct drm_connector_state *old_conn_state, *new_conn_state;
        struct drm_crtc *crtc;
        struct drm_crtc_state *old_crtc_state, *new_crtc_state;
        int i;

        for_each_oldnew_connector_in_state(old_state, connector, old_conn_state, new_conn_state, i) {
                const struct drm_encoder_helper_funcs *funcs;
                struct drm_encoder *encoder;
                struct drm_bridge *bridge;

                /*
                 * Shut down everything that's in the changeset and currently
                 * still on. So need to check the old, saved state.
                 */
                if (!old_conn_state->crtc)
                        continue;

                old_crtc_state = drm_atomic_get_old_crtc_state(old_state, old_conn_state->crtc);

                if (new_conn_state->crtc)
                        new_crtc_state = drm_atomic_get_new_crtc_state(
                                                old_state,
                                                new_conn_state->crtc);
                else
                        new_crtc_state = NULL;

                if (!crtc_needs_disable(old_crtc_state, new_crtc_state) ||
                    !drm_atomic_crtc_needs_modeset(old_conn_state->crtc->state))
                        continue;

                encoder = old_conn_state->best_encoder;

                /* We shouldn't get this far if we didn't previously have
                 * an encoder.. but WARN_ON() rather than explode.
                 */
                if (WARN_ON(!encoder))
                        continue;

                funcs = encoder->helper_private;

                drm_dbg_atomic(dev, "disabling [ENCODER:%d:%s]\n",
                               encoder->base.id, encoder->name);

                /*
                 * Each encoder has at most one connector (since we always steal
                 * it away), so we won't call disable hooks twice.
                 */
                bridge = drm_bridge_chain_get_first_bridge(encoder);
                drm_atomic_bridge_chain_disable(bridge, old_state);

                /* Right function depends upon target state. */
                if (funcs) {
                        if (funcs->atomic_disable)
                                funcs->atomic_disable(encoder, old_state);
                        else if (new_conn_state->crtc && funcs->prepare)
                                funcs->prepare(encoder);
                        else if (funcs->disable)
                                funcs->disable(encoder);
                        else if (funcs->dpms)
                                funcs->dpms(encoder, DRM_MODE_DPMS_OFF);
                }

                drm_atomic_bridge_chain_post_disable(bridge, old_state);
        }

        for_each_oldnew_crtc_in_state(old_state, crtc, old_crtc_state, new_crtc_state, i) {
                const struct drm_crtc_helper_funcs *funcs;
                int ret;

                /* Shut down everything that needs a full modeset. */
                if (!drm_atomic_crtc_needs_modeset(new_crtc_state))
                        continue;

                if (!crtc_needs_disable(old_crtc_state, new_crtc_state))
                        continue;

                funcs = crtc->helper_private;

                drm_dbg_atomic(dev, "disabling [CRTC:%d:%s]\n",
                               crtc->base.id, crtc->name);


                /* Right function depends upon target state. */
                if (new_crtc_state->enable && funcs->prepare)
                        funcs->prepare(crtc);
                else if (funcs->atomic_disable)
                        funcs->atomic_disable(crtc, old_state);
                else if (funcs->disable)
                        funcs->disable(crtc);
                else if (funcs->dpms)
                        funcs->dpms(crtc, DRM_MODE_DPMS_OFF);

                if (!drm_dev_has_vblank(dev))
                        continue;

                ret = drm_crtc_vblank_get(crtc);
                WARN_ONCE(ret != -EINVAL, "driver forgot to call drm_crtc_vblank_off()\n");
                if (ret == 0)
                        drm_crtc_vblank_put(crtc);
        }
}

/**
 * drm_atomic_helper_update_legacy_modeset_state - update legacy modeset state
 * @dev: DRM device
 * @old_state: atomic state object with old state structures
 *
 * This function updates all the various legacy modeset state pointers in
 * connectors, encoders and CRTCs.
 *
 * Drivers can use this for building their own atomic commit if they don't have
 * a pure helper-based modeset implementation.
 *
 * Since these updates are not synchronized with lockings, only code paths
 * called from &drm_mode_config_helper_funcs.atomic_commit_tail can look at the
 * legacy state filled out by this helper. Defacto this means this helper and
 * the legacy state pointers are only really useful for transitioning an
 * existing driver to the atomic world.
 */
void
drm_atomic_helper_update_legacy_modeset_state(struct drm_device *dev,
                                              struct drm_atomic_state *old_state)
{
        struct drm_connector *connector;
        struct drm_connector_state *old_conn_state, *new_conn_state;
        struct drm_crtc *crtc;
        struct drm_crtc_state *new_crtc_state;
        int i;

        /* clear out existing links and update dpms */
        for_each_oldnew_connector_in_state(old_state, connector, old_conn_state, new_conn_state, i) {
                if (connector->encoder) {
                        WARN_ON(!connector->encoder->crtc);

                        connector->encoder->crtc = NULL;
                        connector->encoder = NULL;
                }

                crtc = new_conn_state->crtc;
                if ((!crtc && old_conn_state->crtc) ||
                    (crtc && drm_atomic_crtc_needs_modeset(crtc->state))) {
                        int mode = DRM_MODE_DPMS_OFF;

                        if (crtc && crtc->state->active)
                                mode = DRM_MODE_DPMS_ON;

                        connector->dpms = mode;
                }
        }

        /* set new links */
        for_each_new_connector_in_state(old_state, connector, new_conn_state, i) {
                if (!new_conn_state->crtc)
                        continue;

                if (WARN_ON(!new_conn_state->best_encoder))
                        continue;

                connector->encoder = new_conn_state->best_encoder;
                connector->encoder->crtc = new_conn_state->crtc;
        }

        /* set legacy state in the crtc structure */
        for_each_new_crtc_in_state(old_state, crtc, new_crtc_state, i) {
                struct drm_plane *primary = crtc->primary;
                struct drm_plane_state *new_plane_state;

                crtc->mode = new_crtc_state->mode;
                crtc->enabled = new_crtc_state->enable;

                new_plane_state =
                        drm_atomic_get_new_plane_state(old_state, primary);

                if (new_plane_state && new_plane_state->crtc == crtc) {
                        crtc->x = new_plane_state->src_x >> 16;
                        crtc->y = new_plane_state->src_y >> 16;
                }
        }
}
EXPORT_SYMBOL(drm_atomic_helper_update_legacy_modeset_state);

/**
 * drm_atomic_helper_calc_timestamping_constants - update vblank timestamping constants
 * @state: atomic state object
 *
 * Updates the timestamping constants used for precise vblank timestamps
 * by calling drm_calc_timestamping_constants() for all enabled crtcs in @state.
 */
void drm_atomic_helper_calc_timestamping_constants(struct drm_atomic_state *state)
{
        struct drm_crtc_state *new_crtc_state;
        struct drm_crtc *crtc;
        int i;

        for_each_new_crtc_in_state(state, crtc, new_crtc_state, i) {
                if (new_crtc_state->enable)
                        drm_calc_timestamping_constants(crtc,
                                                        &new_crtc_state->adjusted_mode);
        }
}
EXPORT_SYMBOL(drm_atomic_helper_calc_timestamping_constants);

static void
crtc_set_mode(struct drm_device *dev, struct drm_atomic_state *old_state)
{
        struct drm_crtc *crtc;
        struct drm_crtc_state *new_crtc_state;
        struct drm_connector *connector;
        struct drm_connector_state *new_conn_state;
        int i;

        for_each_new_crtc_in_state(old_state, crtc, new_crtc_state, i) {
                const struct drm_crtc_helper_funcs *funcs;

                if (!new_crtc_state->mode_changed)
                        continue;

                funcs = crtc->helper_private;

                if (new_crtc_state->enable && funcs->mode_set_nofb) {
                        drm_dbg_atomic(dev, "modeset on [CRTC:%d:%s]\n",
                                       crtc->base.id, crtc->name);

                        funcs->mode_set_nofb(crtc);
                }
        }

        for_each_new_connector_in_state(old_state, connector, new_conn_state, i) {
                const struct drm_encoder_helper_funcs *funcs;
                struct drm_encoder *encoder;
                struct drm_display_mode *mode, *adjusted_mode;
                struct drm_bridge *bridge;

                if (!new_conn_state->best_encoder)
                        continue;

                encoder = new_conn_state->best_encoder;
                funcs = encoder->helper_private;
                new_crtc_state = new_conn_state->crtc->state;
                mode = &new_crtc_state->mode;
                adjusted_mode = &new_crtc_state->adjusted_mode;

                if (!new_crtc_state->mode_changed)
                        continue;

                drm_dbg_atomic(dev, "modeset on [ENCODER:%d:%s]\n",
                               encoder->base.id, encoder->name);

                /*
                 * Each encoder has at most one connector (since we always steal
                 * it away), so we won't call mode_set hooks twice.
                 */
                if (funcs && funcs->atomic_mode_set) {
                        funcs->atomic_mode_set(encoder, new_crtc_state,
                                               new_conn_state);
                } else if (funcs && funcs->mode_set) {
                        funcs->mode_set(encoder, mode, adjusted_mode);
                }

                bridge = drm_bridge_chain_get_first_bridge(encoder);
                drm_bridge_chain_mode_set(bridge, mode, adjusted_mode);
        }
}

/**
 * drm_atomic_helper_commit_modeset_disables - modeset commit to disable outputs
 * @dev: DRM device
 * @old_state: atomic state object with old state structures
 *
 * This function shuts down all the outputs that need to be shut down and
 * prepares them (if required) with the new mode.
 *
 * For compatibility with legacy CRTC helpers this should be called before
 * drm_atomic_helper_commit_planes(), which is what the default commit function
 * does. But drivers with different needs can group the modeset commits together
 * and do the plane commits at the end. This is useful for drivers doing runtime
 * PM since planes updates then only happen when the CRTC is actually enabled.
 */
void drm_atomic_helper_commit_modeset_disables(struct drm_device *dev,
                                               struct drm_atomic_state *old_state)
{
        disable_outputs(dev, old_state);

        drm_atomic_helper_update_legacy_modeset_state(dev, old_state);
        drm_atomic_helper_calc_timestamping_constants(old_state);

        crtc_set_mode(dev, old_state);
}
EXPORT_SYMBOL(drm_atomic_helper_commit_modeset_disables);

static void drm_atomic_helper_commit_writebacks(struct drm_device *dev,
                                                struct drm_atomic_state *old_state)
{
        struct drm_connector *connector;
        struct drm_connector_state *new_conn_state;
        int i;

        for_each_new_connector_in_state(old_state, connector, new_conn_state, i) {
                const struct drm_connector_helper_funcs *funcs;

                funcs = connector->helper_private;
                if (!funcs->atomic_commit)
                        continue;

                if (new_conn_state->writeback_job && new_conn_state->writeback_job->fb) {
                        WARN_ON(connector->connector_type != DRM_MODE_CONNECTOR_WRITEBACK);
                        funcs->atomic_commit(connector, old_state);
                }
        }
}

/**
 * drm_atomic_helper_commit_modeset_enables - modeset commit to enable outputs
 * @dev: DRM device
 * @old_state: atomic state object with old state structures
 *
 * This function enables all the outputs with the new configuration which had to
 * be turned off for the update.
 *
 * For compatibility with legacy CRTC helpers this should be called after
 * drm_atomic_helper_commit_planes(), which is what the default commit function
 * does. But drivers with different needs can group the modeset commits together
 * and do the plane commits at the end. This is useful for drivers doing runtime
 * PM since planes updates then only happen when the CRTC is actually enabled.
 */
void drm_atomic_helper_commit_modeset_enables(struct drm_device *dev,
                                              struct drm_atomic_state *old_state)
{
        struct drm_crtc *crtc;
        struct drm_crtc_state *old_crtc_state;
        struct drm_crtc_state *new_crtc_state;
        struct drm_connector *connector;
        struct drm_connector_state *new_conn_state;
        int i;

        for_each_oldnew_crtc_in_state(old_state, crtc, old_crtc_state, new_crtc_state, i) {
                const struct drm_crtc_helper_funcs *funcs;

                /* Need to filter out CRTCs where only planes change. */
                if (!drm_atomic_crtc_needs_modeset(new_crtc_state))
                        continue;

                if (!new_crtc_state->active)
                        continue;

                funcs = crtc->helper_private;

                if (new_crtc_state->enable) {
                        drm_dbg_atomic(dev, "enabling [CRTC:%d:%s]\n",
                                       crtc->base.id, crtc->name);
                        if (funcs->atomic_enable)
                                funcs->atomic_enable(crtc, old_state);
                        else if (funcs->commit)
                                funcs->commit(crtc);
                }
        }

        for_each_new_connector_in_state(old_state, connector, new_conn_state, i) {
                const struct drm_encoder_helper_funcs *funcs;
                struct drm_encoder *encoder;
                struct drm_bridge *bridge;

                if (!new_conn_state->best_encoder)
                        continue;

                if (!new_conn_state->crtc->state->active ||
                    !drm_atomic_crtc_needs_modeset(new_conn_state->crtc->state))
                        continue;

                encoder = new_conn_state->best_encoder;
                funcs = encoder->helper_private;

                drm_dbg_atomic(dev, "enabling [ENCODER:%d:%s]\n",
                               encoder->base.id, encoder->name);

                /*
                 * Each encoder has at most one connector (since we always steal
                 * it away), so we won't call enable hooks twice.
                 */
                bridge = drm_bridge_chain_get_first_bridge(encoder);
                drm_atomic_bridge_chain_pre_enable(bridge, old_state);

                if (funcs) {
                        if (funcs->atomic_enable)
                                funcs->atomic_enable(encoder, old_state);
                        else if (funcs->enable)
                                funcs->enable(encoder);
                        else if (funcs->commit)
                                funcs->commit(encoder);
                }

                drm_atomic_bridge_chain_enable(bridge, old_state);
        }

        drm_atomic_helper_commit_writebacks(dev, old_state);
}
EXPORT_SYMBOL(drm_atomic_helper_commit_modeset_enables);

/**
 * drm_atomic_helper_wait_for_fences - wait for fences stashed in plane state
 * @dev: DRM device
 * @state: atomic state object with old state structures
 * @pre_swap: If true, do an interruptible wait, and @state is the new state.
 *      Otherwise @state is the old state.
 *
 * For implicit sync, driver should fish the exclusive fence out from the
 * incoming fb's and stash it in the drm_plane_state.  This is called after
 * drm_atomic_helper_swap_state() so it uses the current plane state (and
 * just uses the atomic state to find the changed planes)
 *
 * Note that @pre_swap is needed since the point where we block for fences moves
 * around depending upon whether an atomic commit is blocking or
 * non-blocking. For non-blocking commit all waiting needs to happen after
 * drm_atomic_helper_swap_state() is called, but for blocking commits we want
 * to wait **before** we do anything that can't be easily rolled back. That is
 * before we call drm_atomic_helper_swap_state().
 *
 * Returns zero if success or < 0 if dma_fence_wait() fails.
 */
int drm_atomic_helper_wait_for_fences(struct drm_device *dev,
                                      struct drm_atomic_state *state,
                                      bool pre_swap)
{
        struct drm_plane *plane;
        struct drm_plane_state *new_plane_state;
        int i, ret;

        for_each_new_plane_in_state(state, plane, new_plane_state, i) {
                if (!new_plane_state->fence)
                        continue;

                WARN_ON(!new_plane_state->fb);

                /*
                 * If waiting for fences pre-swap (ie: nonblock), userspace can
                 * still interrupt the operation. Instead of blocking until the
                 * timer expires, make the wait interruptible.
                 */
                ret = dma_fence_wait(new_plane_state->fence, pre_swap);
                if (ret)
                        return ret;

                dma_fence_put(new_plane_state->fence);
                new_plane_state->fence = NULL;
        }

        return 0;
}
EXPORT_SYMBOL(drm_atomic_helper_wait_for_fences);

/**
 * drm_atomic_helper_wait_for_vblanks - wait for vblank on CRTCs
 * @dev: DRM device
 * @old_state: atomic state object with old state structures
 *
 * Helper to, after atomic commit, wait for vblanks on all affected
 * CRTCs (ie. before cleaning up old framebuffers using
 * drm_atomic_helper_cleanup_planes()). It will only wait on CRTCs where the
 * framebuffers have actually changed to optimize for the legacy cursor and
 * plane update use-case.
 *
 * Drivers using the nonblocking commit tracking support initialized by calling
 * drm_atomic_helper_setup_commit() should look at
 * drm_atomic_helper_wait_for_flip_done() as an alternative.
 */
void
drm_atomic_helper_wait_for_vblanks(struct drm_device *dev,
                struct drm_atomic_state *old_state)
{
        struct drm_crtc *crtc;
        struct drm_crtc_state *old_crtc_state, *new_crtc_state;
        int i, ret;
        unsigned int crtc_mask = 0;

         /*
          * Legacy cursor ioctls are completely unsynced, and userspace
          * relies on that (by doing tons of cursor updates).
          */
        if (old_state->legacy_cursor_update)
                return;

        for_each_oldnew_crtc_in_state(old_state, crtc, old_crtc_state, new_crtc_state, i) {
                if (!new_crtc_state->active)
                        continue;

                ret = drm_crtc_vblank_get(crtc);
                if (ret != 0)
                        continue;

                crtc_mask |= drm_crtc_mask(crtc);
                old_state->crtcs[i].last_vblank_count = drm_crtc_vblank_count(crtc);
        }

        for_each_old_crtc_in_state(old_state, crtc, old_crtc_state, i) {
                if (!(crtc_mask & drm_crtc_mask(crtc)))
                        continue;

                ret = wait_event_timeout(dev->vblank[i].queue,
                                old_state->crtcs[i].last_vblank_count !=
                                        drm_crtc_vblank_count(crtc),
                                msecs_to_jiffies(100));

                WARN(!ret, "[CRTC:%d:%s] vblank wait timed out\n",
                     crtc->base.id, crtc->name);

                drm_crtc_vblank_put(crtc);
        }
}
EXPORT_SYMBOL(drm_atomic_helper_wait_for_vblanks);

/**
 * drm_atomic_helper_wait_for_flip_done - wait for all page flips to be done
 * @dev: DRM device
 * @old_state: atomic state object with old state structures
 *
 * Helper to, after atomic commit, wait for page flips on all affected
 * crtcs (ie. before cleaning up old framebuffers using
 * drm_atomic_helper_cleanup_planes()). Compared to
 * drm_atomic_helper_wait_for_vblanks() this waits for the completion on all
 * CRTCs, assuming that cursors-only updates are signalling their completion
 * immediately (or using a different path).
 *
 * This requires that drivers use the nonblocking commit tracking support
 * initialized using drm_atomic_helper_setup_commit().
 */
void drm_atomic_helper_wait_for_flip_done(struct drm_device *dev,
                                          struct drm_atomic_state *old_state)
{
        struct drm_crtc *crtc;
        int i;

        for (i = 0; i < dev->mode_config.num_crtc; i++) {
                struct drm_crtc_commit *commit = old_state->crtcs[i].commit;
                int ret;

                crtc = old_state->crtcs[i].ptr;

                if (!crtc || !commit)
                        continue;

                ret = wait_for_completion_timeout(&commit->flip_done, 10 * HZ);
                if (ret == 0)
                        drm_err(dev, "[CRTC:%d:%s] flip_done timed out\n",
                                crtc->base.id, crtc->name);
        }

        if (old_state->fake_commit)
                complete_all(&old_state->fake_commit->flip_done);
}
EXPORT_SYMBOL(drm_atomic_helper_wait_for_flip_done);

/**
 * drm_atomic_helper_commit_tail - commit atomic update to hardware
 * @old_state: atomic state object with old state structures
 *
 * This is the default implementation for the
 * &drm_mode_config_helper_funcs.atomic_commit_tail hook, for drivers
 * that do not support runtime_pm or do not need the CRTC to be
 * enabled to perform a commit. Otherwise, see
 * drm_atomic_helper_commit_tail_rpm().
 *
 * Note that the default ordering of how the various stages are called is to
 * match the legacy modeset helper library closest.
 */
void drm_atomic_helper_commit_tail(struct drm_atomic_state *old_state)
{
        struct drm_device *dev = old_state->dev;

        drm_atomic_helper_commit_modeset_disables(dev, old_state);

        drm_atomic_helper_commit_planes(dev, old_state, 0);

        drm_atomic_helper_commit_modeset_enables(dev, old_state);

        drm_atomic_helper_fake_vblank(old_state);

        drm_atomic_helper_commit_hw_done(old_state);

        drm_atomic_helper_wait_for_vblanks(dev, old_state);

        drm_atomic_helper_cleanup_planes(dev, old_state);
}
EXPORT_SYMBOL(drm_atomic_helper_commit_tail);

/**
 * drm_atomic_helper_commit_tail_rpm - commit atomic update to hardware
 * @old_state: new modeset state to be committed
 *
 * This is an alternative implementation for the
 * &drm_mode_config_helper_funcs.atomic_commit_tail hook, for drivers
 * that support runtime_pm or need the CRTC to be enabled to perform a
 * commit. Otherwise, one should use the default implementation
 * drm_atomic_helper_commit_tail().
 */
void drm_atomic_helper_commit_tail_rpm(struct drm_atomic_state *old_state)
{
        struct drm_device *dev = old_state->dev;

        drm_atomic_helper_commit_modeset_disables(dev, old_state);

        drm_atomic_helper_commit_modeset_enables(dev, old_state);

        drm_atomic_helper_commit_planes(dev, old_state,
                                        DRM_PLANE_COMMIT_ACTIVE_ONLY);

        drm_atomic_helper_fake_vblank(old_state);

        drm_atomic_helper_commit_hw_done(old_state);

        drm_atomic_helper_wait_for_vblanks(dev, old_state);

        drm_atomic_helper_cleanup_planes(dev, old_state);
}
EXPORT_SYMBOL(drm_atomic_helper_commit_tail_rpm);

static void commit_tail(struct drm_atomic_state *old_state)
{
        struct drm_device *dev = old_state->dev;
        const struct drm_mode_config_helper_funcs *funcs;
        struct drm_crtc_state *new_crtc_state;
        struct drm_crtc *crtc;
        ktime_t start;
        s64 commit_time_ms;
        unsigned int i, new_self_refresh_mask = 0;

        funcs = dev->mode_config.helper_private;

        /*
         * We're measuring the _entire_ commit, so the time will vary depending
         * on how many fences and objects are involved. For the purposes of self
         * refresh, this is desirable since it'll give us an idea of how
         * congested things are. This will inform our decision on how often we
         * should enter self refresh after idle.
         *
         * These times will be averaged out in the self refresh helpers to avoid
         * overreacting over one outlier frame
         */
        start = ktime_get();

        drm_atomic_helper_wait_for_fences(dev, old_state, false);

        drm_atomic_helper_wait_for_dependencies(old_state);

        /*
         * We cannot safely access new_crtc_state after
         * drm_atomic_helper_commit_hw_done() so figure out which crtc's have
         * self-refresh active beforehand:
         */
        for_each_new_crtc_in_state(old_state, crtc, new_crtc_state, i)
                if (new_crtc_state->self_refresh_active)
                        new_self_refresh_mask |= BIT(i);

        if (funcs && funcs->atomic_commit_tail)
                funcs->atomic_commit_tail(old_state);
        else
                drm_atomic_helper_commit_tail(old_state);

        commit_time_ms = ktime_ms_delta(ktime_get(), start);
        if (commit_time_ms > 0)
                drm_self_refresh_helper_update_avg_times(old_state,
                                                 (unsigned long)commit_time_ms,
                                                 new_self_refresh_mask);

        drm_atomic_helper_commit_cleanup_done(old_state);

        drm_atomic_state_put(old_state);
}

static void commit_work(struct work_struct *work)
{
        struct drm_atomic_state *state = container_of(work,
                                                      struct drm_atomic_state,
                                                      commit_work);
        commit_tail(state);
}

/**
 * drm_atomic_helper_async_check - check if state can be committed asynchronously
 * @dev: DRM device
 * @state: the driver state object
 *
 * This helper will check if it is possible to commit the state asynchronously.
 * Async commits are not supposed to swap the states like normal sync commits
 * but just do in-place changes on the current state.
 *
 * It will return 0 if the commit can happen in an asynchronous fashion or error
 * if not. Note that error just mean it can't be committed asynchronously, if it
 * fails the commit should be treated like a normal synchronous commit.
 */
int drm_atomic_helper_async_check(struct drm_device *dev,
                                   struct drm_atomic_state *state)
{
        struct drm_crtc *crtc;
        struct drm_crtc_state *crtc_state;
        struct drm_plane *plane = NULL;
        struct drm_plane_state *old_plane_state = NULL;
        struct drm_plane_state *new_plane_state = NULL;
        const struct drm_plane_helper_funcs *funcs;
        int i, n_planes = 0;

        for_each_new_crtc_in_state(state, crtc, crtc_state, i) {
                if (drm_atomic_crtc_needs_modeset(crtc_state))
                        return -EINVAL;
        }

        for_each_oldnew_plane_in_state(state, plane, old_plane_state, new_plane_state, i)
                n_planes++;

        /* FIXME: we support only single plane updates for now */
        if (n_planes != 1)
                return -EINVAL;

        if (!new_plane_state->crtc ||
            old_plane_state->crtc != new_plane_state->crtc)
                return -EINVAL;

        funcs = plane->helper_private;
        if (!funcs->atomic_async_update)
                return -EINVAL;

        if (new_plane_state->fence)
                return -EINVAL;

        /*
         * Don't do an async update if there is an outstanding commit modifying
         * the plane.  This prevents our async update's changes from getting
         * overridden by a previous synchronous update's state.
         */
        if (old_plane_state->commit &&
            !try_wait_for_completion(&old_plane_state->commit->hw_done)) {
                drm_dbg_atomic(dev,
                               "[PLANE:%d:%s] inflight previous commit preventing async commit\n",
                               plane->base.id, plane->name);
                return -EBUSY;
        }

        return funcs->atomic_async_check(plane, state);
}
EXPORT_SYMBOL(drm_atomic_helper_async_check);

/**
 * drm_atomic_helper_async_commit - commit state asynchronously
 * @dev: DRM device
 * @state: the driver state object
 *
 * This function commits a state asynchronously, i.e., not vblank
 * synchronized. It should be used on a state only when
 * drm_atomic_async_check() succeeds. Async commits are not supposed to swap
 * the states like normal sync commits, but just do in-place changes on the
 * current state.
 *
 * TODO: Implement full swap instead of doing in-place changes.
 */
void drm_atomic_helper_async_commit(struct drm_device *dev,
                                    struct drm_atomic_state *state)
{
        struct drm_plane *plane;
        struct drm_plane_state *plane_state;
        const struct drm_plane_helper_funcs *funcs;
        int i;

        for_each_new_plane_in_state(state, plane, plane_state, i) {
                struct drm_framebuffer *new_fb = plane_state->fb;
                struct drm_framebuffer *old_fb = plane->state->fb;

                funcs = plane->helper_private;
                funcs->atomic_async_update(plane, state);

                /*
                 * ->atomic_async_update() is supposed to update the
                 * plane->state in-place, make sure at least common
                 * properties have been properly updated.
                 */
                WARN_ON_ONCE(plane->state->fb != new_fb);
                WARN_ON_ONCE(plane->state->crtc_x != plane_state->crtc_x);
                WARN_ON_ONCE(plane->state->crtc_y != plane_state->crtc_y);
                WARN_ON_ONCE(plane->state->src_x != plane_state->src_x);
                WARN_ON_ONCE(plane->state->src_y != plane_state->src_y);

                /*
                 * Make sure the FBs have been swapped so that cleanups in the
                 * new_state performs a cleanup in the old FB.
                 */
                WARN_ON_ONCE(plane_state->fb != old_fb);
        }
}
EXPORT_SYMBOL(drm_atomic_helper_async_commit);

/**
 * drm_atomic_helper_commit - commit validated state object
 * @dev: DRM device
 * @state: the driver state object
 * @nonblock: whether nonblocking behavior is requested.
 *
 * This function commits a with drm_atomic_helper_check() pre-validated state
 * object. This can still fail when e.g. the framebuffer reservation fails. This
 * function implements nonblocking commits, using
 * drm_atomic_helper_setup_commit() and related functions.
 *
 * Committing the actual hardware state is done through the
 * &drm_mode_config_helper_funcs.atomic_commit_tail callback, or its default
 * implementation drm_atomic_helper_commit_tail().
 *
 * RETURNS:
 * Zero for success or -errno.
 */
int drm_atomic_helper_commit(struct drm_device *dev,
                             struct drm_atomic_state *state,
                             bool nonblock)
{
        int ret;

        if (state->async_update) {
                ret = drm_atomic_helper_prepare_planes(dev, state);
                if (ret)
                        return ret;

                drm_atomic_helper_async_commit(dev, state);
                drm_atomic_helper_cleanup_planes(dev, state);

                return 0;
        }

        ret = drm_atomic_helper_setup_commit(state, nonblock);
        if (ret)
                return ret;

        INIT_WORK(&state->commit_work, commit_work);

        ret = drm_atomic_helper_prepare_planes(dev, state);
        if (ret)
                return ret;

        if (!nonblock) {
                ret = drm_atomic_helper_wait_for_fences(dev, state, true);
                if (ret)
                        goto err;
        }

        /*
         * This is the point of no return - everything below never fails except
         * when the hw goes bonghits. Which means we can commit the new state on
         * the software side now.
         */

        ret = drm_atomic_helper_swap_state(state, true);
        if (ret)
                goto err;

        /*
         * Everything below can be run asynchronously without the need to grab
         * any modeset locks at all under one condition: It must be guaranteed
         * that the asynchronous work has either been cancelled (if the driver
         * supports it, which at least requires that the framebuffers get
         * cleaned up with drm_atomic_helper_cleanup_planes()) or completed
         * before the new state gets committed on the software side with
         * drm_atomic_helper_swap_state().
         *
         * This scheme allows new atomic state updates to be prepared and
         * checked in parallel to the asynchronous completion of the previous
         * update. Which is important since compositors need to figure out the
         * composition of the next frame right after having submitted the
         * current layout.
         *
         * NOTE: Commit work has multiple phases, first hardware commit, then
         * cleanup. We want them to overlap, hence need system_unbound_wq to
         * make sure work items don't artificially stall on each another.
         */

        drm_atomic_state_get(state);
        if (nonblock)
                queue_work(system_unbound_wq, &state->commit_work);
        else
                commit_tail(state);

        return 0;

err:
        drm_atomic_helper_cleanup_planes(dev, state);
        return ret;
}
EXPORT_SYMBOL(drm_atomic_helper_commit);

/**
 * DOC: implementing nonblocking commit
 *
 * Nonblocking atomic commits should use struct &drm_crtc_commit to sequence
 * different operations against each another. Locks, especially struct
 * &drm_modeset_lock, should not be held in worker threads or any other
 * asynchronous context used to commit the hardware state.
 *
 * drm_atomic_helper_commit() implements the recommended sequence for
 * nonblocking commits, using drm_atomic_helper_setup_commit() internally:
 *
 * 1. Run drm_atomic_helper_prepare_planes(). Since this can fail and we
 * need to propagate out of memory/VRAM errors to userspace, it must be called
 * synchronously.
 *
 * 2. Synchronize with any outstanding nonblocking commit worker threads which
 * might be affected by the new state update. This is handled by
 * drm_atomic_helper_setup_commit().
 *
 * Asynchronous workers need to have sufficient parallelism to be able to run
 * different atomic commits on different CRTCs in parallel. The simplest way to
 * achieve this is by running them on the &system_unbound_wq work queue. Note
 * that drivers are not required to split up atomic commits and run an
 * individual commit in parallel - userspace is supposed to do that if it cares.
 * But it might be beneficial to do that for modesets, since those necessarily
 * must be done as one global operation, and enabling or disabling a CRTC can
 * take a long time. But even that is not required.
 *
 * IMPORTANT: A &drm_atomic_state update for multiple CRTCs is sequenced
 * against all CRTCs therein. Therefore for atomic state updates which only flip
 * planes the driver must not get the struct &drm_crtc_state of unrelated CRTCs
 * in its atomic check code: This would prevent committing of atomic updates to
 * multiple CRTCs in parallel. In general, adding additional state structures
 * should be avoided as much as possible, because this reduces parallelism in
 * (nonblocking) commits, both due to locking and due to commit sequencing
 * requirements.
 *
 * 3. The software state is updated synchronously with
 * drm_atomic_helper_swap_state(). Doing this under the protection of all modeset
 * locks means concurrent callers never see inconsistent state. Note that commit
 * workers do not hold any locks; their access is only coordinated through
 * ordering. If workers would access state only through the pointers in the
 * free-standing state objects (currently not the case for any driver) then even
 * multiple pending commits could be in-flight at the same time.
 *
 * 4. Schedule a work item to do all subsequent steps, using the split-out
 * commit helpers: a) pre-plane commit b) plane commit c) post-plane commit and
 * then cleaning up the framebuffers after the old framebuffer is no longer
 * being displayed. The scheduled work should synchronize against other workers
 * using the &drm_crtc_commit infrastructure as needed. See
 * drm_atomic_helper_setup_commit() for more details.
 */

static int stall_checks(struct drm_crtc *crtc, bool nonblock)
{
        struct drm_crtc_commit *commit, *stall_commit = NULL;
        bool completed = true;
        int i;
        long ret = 0;

        spin_lock(&crtc->commit_lock);
        i = 0;
        list_for_each_entry(commit, &crtc->commit_list, commit_entry) {
                if (i == 0) {
                        completed = try_wait_for_completion(&commit->flip_done);
                        /*
                         * Userspace is not allowed to get ahead of the previous
                         * commit with nonblocking ones.
                         */
                        if (!completed && nonblock) {
                                spin_unlock(&crtc->commit_lock);
                                drm_dbg_atomic(crtc->dev,
                                               "[CRTC:%d:%s] busy with a previous commit\n",
                                               crtc->base.id, crtc->name);

                                return -EBUSY;
                        }
                } else if (i == 1) {
                        stall_commit = drm_crtc_commit_get(commit);
                        break;
                }

                i++;
        }
        spin_unlock(&crtc->commit_lock);

        if (!stall_commit)
                return 0;

        /* We don't want to let commits get ahead of cleanup work too much,
         * stalling on 2nd previous commit means triple-buffer won't ever stall.
         */
        ret = wait_for_completion_interruptible_timeout(&stall_commit->cleanup_done,
                                                        10*HZ);
        if (ret == 0)
                drm_err(crtc->dev, "[CRTC:%d:%s] cleanup_done timed out\n",
                        crtc->base.id, crtc->name);

        drm_crtc_commit_put(stall_commit);

        return ret < 0 ? ret : 0;
}

static void release_crtc_commit(struct completion *completion)
{
        struct drm_crtc_commit *commit = container_of(completion,
                                                      typeof(*commit),
                                                      flip_done);

        drm_crtc_commit_put(commit);
}

static void init_commit(struct drm_crtc_commit *commit, struct drm_crtc *crtc)
{
        init_completion(&commit->flip_done);
        init_completion(&commit->hw_done);
        init_completion(&commit->cleanup_done);
        INIT_LIST_HEAD(&commit->commit_entry);
        kref_init(&commit->ref);
        commit->crtc = crtc;
}

static struct drm_crtc_commit *
crtc_or_fake_commit(struct drm_atomic_state *state, struct drm_crtc *crtc)
{
        if (crtc) {
                struct drm_crtc_state *new_crtc_state;

                new_crtc_state = drm_atomic_get_new_crtc_state(state, crtc);

                return new_crtc_state->commit;
        }

        if (!state->fake_commit) {
                state->fake_commit = kzalloc(sizeof(*state->fake_commit), GFP_KERNEL);
                if (!state->fake_commit)
                        return NULL;

                init_commit(state->fake_commit, NULL);
        }

        return state->fake_commit;
}

/**
 * drm_atomic_helper_setup_commit - setup possibly nonblocking commit
 * @state: new modeset state to be committed
 * @nonblock: whether nonblocking behavior is requested.
 *
 * This function prepares @state to be used by the atomic helper's support for
 * nonblocking commits. Drivers using the nonblocking commit infrastructure
 * should always call this function from their
 * &drm_mode_config_funcs.atomic_commit hook.
 *
 * Drivers that need to extend the commit setup to private objects can use the
 * &drm_mode_config_helper_funcs.atomic_commit_setup hook.
 *
 * To be able to use this support drivers need to use a few more helper
 * functions. drm_atomic_helper_wait_for_dependencies() must be called before
 * actually committing the hardware state, and for nonblocking commits this call
 * must be placed in the async worker. See also drm_atomic_helper_swap_state()
 * and its stall parameter, for when a driver's commit hooks look at the
 * &drm_crtc.state, &drm_plane.state or &drm_connector.state pointer directly.
 *
 * Completion of the hardware commit step must be signalled using
 * drm_atomic_helper_commit_hw_done(). After this step the driver is not allowed
 * to read or change any permanent software or hardware modeset state. The only
 * exception is state protected by other means than &drm_modeset_lock locks.
 * Only the free standing @state with pointers to the old state structures can
 * be inspected, e.g. to clean up old buffers using
 * drm_atomic_helper_cleanup_planes().
 *
 * At the very end, before cleaning up @state drivers must call
 * drm_atomic_helper_commit_cleanup_done().
 *
 * This is all implemented by in drm_atomic_helper_commit(), giving drivers a
 * complete and easy-to-use default implementation of the atomic_commit() hook.
 *
 * The tracking of asynchronously executed and still pending commits is done
 * using the core structure &drm_crtc_commit.
 *
 * By default there's no need to clean up resources allocated by this function
 * explicitly: drm_atomic_state_default_clear() will take care of that
 * automatically.
 *
 * Returns:
 *
 * 0 on success. -EBUSY when userspace schedules nonblocking commits too fast,
 * -ENOMEM on allocation failures and -EINTR when a signal is pending.
 */
int drm_atomic_helper_setup_commit(struct drm_atomic_state *state,
                                   bool nonblock)
{
        struct drm_crtc *crtc;
        struct drm_crtc_state *old_crtc_state, *new_crtc_state;
        struct drm_connector *conn;
        struct drm_connector_state *old_conn_state, *new_conn_state;
        struct drm_plane *plane;
        struct drm_plane_state *old_plane_state, *new_plane_state;
        struct drm_crtc_commit *commit;
        const struct drm_mode_config_helper_funcs *funcs;
        int i, ret;

        funcs = state->dev->mode_config.helper_private;

        for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) {
                commit = kzalloc(sizeof(*commit), GFP_KERNEL);
                if (!commit)
                        return -ENOMEM;

                init_commit(commit, crtc);

                new_crtc_state->commit = commit;

                ret = stall_checks(crtc, nonblock);
                if (ret)
                        return ret;

                /*
                 * Drivers only send out events when at least either current or
                 * new CRTC state is active. Complete right away if everything
                 * stays off.
                 */
                if (!old_crtc_state->active && !new_crtc_state->active) {
                        complete_all(&commit->flip_done);
                        continue;
                }

                /* Legacy cursor updates are fully unsynced. */
                if (state->legacy_cursor_update) {
                        complete_all(&commit->flip_done);
                        continue;
                }

                if (!new_crtc_state->event) {
                        commit->event = kzalloc(sizeof(*commit->event),
                                                GFP_KERNEL);
                        if (!commit->event)
                                return -ENOMEM;

                        new_crtc_state->event = commit->event;
                }

                new_crtc_state->event->base.completion = &commit->flip_done;
                new_crtc_state->event->base.completion_release = release_crtc_commit;
                drm_crtc_commit_get(commit);

                commit->abort_completion = true;

                state->crtcs[i].commit = commit;
                drm_crtc_commit_get(commit);
        }

        for_each_oldnew_connector_in_state(state, conn, old_conn_state, new_conn_state, i) {
                /*
                 * Userspace is not allowed to get ahead of the previous
                 * commit with nonblocking ones.
                 */
                if (nonblock && old_conn_state->commit &&
                    !try_wait_for_completion(&old_conn_state->commit->flip_done)) {
                        drm_dbg_atomic(conn->dev,
                                       "[CONNECTOR:%d:%s] busy with a previous commit\n",
                                       conn->base.id, conn->name);

                        return -EBUSY;
                }

                /* Always track connectors explicitly for e.g. link retraining. */
                commit = crtc_or_fake_commit(state, new_conn_state->crtc ?: old_conn_state->crtc);
                if (!commit)
                        return -ENOMEM;

                new_conn_state->commit = drm_crtc_commit_get(commit);
        }

        for_each_oldnew_plane_in_state(state, plane, old_plane_state, new_plane_state, i) {
                /*
                 * Userspace is not allowed to get ahead of the previous
                 * commit with nonblocking ones.
                 */
                if (nonblock && old_plane_state->commit &&
                    !try_wait_for_completion(&old_plane_state->commit->flip_done)) {
                        drm_dbg_atomic(plane->dev,
                                       "[PLANE:%d:%s] busy with a previous commit\n",
                                       plane->base.id, plane->name);

                        return -EBUSY;
                }

                /* Always track planes explicitly for async pageflip support. */
                commit = crtc_or_fake_commit(state, new_plane_state->crtc ?: old_plane_state->crtc);
                if (!commit)
                        return -ENOMEM;

                new_plane_state->commit = drm_crtc_commit_get(commit);
        }

        if (funcs && funcs->atomic_commit_setup)
                return funcs->atomic_commit_setup(state);

        return 0;
}
EXPORT_SYMBOL(drm_atomic_helper_setup_commit);

/**
 * drm_atomic_helper_wait_for_dependencies - wait for required preceeding commits
 * @old_state: atomic state object with old state structures
 *
 * This function waits for all preceeding commits that touch the same CRTC as
 * @old_state to both be committed to the hardware (as signalled by
 * drm_atomic_helper_commit_hw_done()) and executed by the hardware (as signalled
 * by calling drm_crtc_send_vblank_event() on the &drm_crtc_state.event).
 *
 * This is part of the atomic helper support for nonblocking commits, see
 * drm_atomic_helper_setup_commit() for an overview.
 */
void drm_atomic_helper_wait_for_dependencies(struct drm_atomic_state *old_state)
{
        struct drm_crtc *crtc;
        struct drm_crtc_state *old_crtc_state;
        struct drm_plane *plane;
        struct drm_plane_state *old_plane_state;
        struct drm_connector *conn;
        struct drm_connector_state *old_conn_state;
        int i;
        long ret;

        for_each_old_crtc_in_state(old_state, crtc, old_crtc_state, i) {
                ret = drm_crtc_commit_wait(old_crtc_state->commit);
                if (ret)
                        drm_err(crtc->dev,
                                "[CRTC:%d:%s] commit wait timed out\n",
                                crtc->base.id, crtc->name);
        }

        for_each_old_connector_in_state(old_state, conn, old_conn_state, i) {
                ret = drm_crtc_commit_wait(old_conn_state->commit);
                if (ret)
                        drm_err(conn->dev,
                                "[CONNECTOR:%d:%s] commit wait timed out\n",
                                conn->base.id, conn->name);
        }

        for_each_old_plane_in_state(old_state, plane, old_plane_state, i) {
                ret = drm_crtc_commit_wait(old_plane_state->commit);
                if (ret)
                        drm_err(plane->dev,
                                "[PLANE:%d:%s] commit wait timed out\n",
                                plane->base.id, plane->name);
        }
}
EXPORT_SYMBOL(drm_atomic_helper_wait_for_dependencies);

/**
 * drm_atomic_helper_fake_vblank - fake VBLANK events if needed
 * @old_state: atomic state object with old state structures
 *
 * This function walks all CRTCs and fakes VBLANK events on those with
 * &drm_crtc_state.no_vblank set to true and &drm_crtc_state.event != NULL.
 * The primary use of this function is writeback connectors working in oneshot
 * mode and faking VBLANK events. In this case they only fake the VBLANK event
 * when a job is queued, and any change to the pipeline that does not touch the
 * connector is leading to timeouts when calling
 * drm_atomic_helper_wait_for_vblanks() or
 * drm_atomic_helper_wait_for_flip_done(). In addition to writeback
 * connectors, this function can also fake VBLANK events for CRTCs without
 * VBLANK interrupt.
 *
 * This is part of the atomic helper support for nonblocking commits, see
 * drm_atomic_helper_setup_commit() for an overview.
 */
void drm_atomic_helper_fake_vblank(struct drm_atomic_state *old_state)
{
        struct drm_crtc_state *new_crtc_state;
        struct drm_crtc *crtc;
        int i;

        for_each_new_crtc_in_state(old_state, crtc, new_crtc_state, i) {
                unsigned long flags;

                if (!new_crtc_state->no_vblank)
                        continue;

                spin_lock_irqsave(&old_state->dev->event_lock, flags);
                if (new_crtc_state->event) {
                        drm_crtc_send_vblank_event(crtc,
                                                   new_crtc_state->event);
                        new_crtc_state->event = NULL;
                }
                spin_unlock_irqrestore(&old_state->dev->event_lock, flags);
        }
}
EXPORT_SYMBOL(drm_atomic_helper_fake_vblank);

/**
 * drm_atomic_helper_commit_hw_done - setup possible nonblocking commit
 * @old_state: atomic state object with old state structures
 *
 * This function is used to signal completion of the hardware commit step. After
 * this step the driver is not allowed to read or change any permanent software
 * or hardware modeset state. The only exception is state protected by other
 * means than &drm_modeset_lock locks.
 *
 * Drivers should try to postpone any expensive or delayed cleanup work after
 * this function is called.
 *
 * This is part of the atomic helper support for nonblocking commits, see
 * drm_atomic_helper_setup_commit() for an overview.
 */
void drm_atomic_helper_commit_hw_done(struct drm_atomic_state *old_state)
{
        struct drm_crtc *crtc;
        struct drm_crtc_state *old_crtc_state, *new_crtc_state;
        struct drm_crtc_commit *commit;
        int i;

        for_each_oldnew_crtc_in_state(old_state, crtc, old_crtc_state, new_crtc_state, i) {
                commit = new_crtc_state->commit;
                if (!commit)
                        continue;

                /*
                 * copy new_crtc_state->commit to old_crtc_state->commit,
                 * it's unsafe to touch new_crtc_state after hw_done,
                 * but we still need to do so in cleanup_done().
                 */
                if (old_crtc_state->commit)
                        drm_crtc_commit_put(old_crtc_state->commit);

                old_crtc_state->commit = drm_crtc_commit_get(commit);

                /* backend must have consumed any event by now */
                WARN_ON(new_crtc_state->event);
                complete_all(&commit->hw_done);
        }

        if (old_state->fake_commit) {
                complete_all(&old_state->fake_commit->hw_done);
                complete_all(&old_state->fake_commit->flip_done);
        }
}
EXPORT_SYMBOL(drm_atomic_helper_commit_hw_done);

/**
 * drm_atomic_helper_commit_cleanup_done - signal completion of commit
 * @old_state: atomic state object with old state structures
 *
 * This signals completion of the atomic update @old_state, including any
 * cleanup work. If used, it must be called right before calling
 * drm_atomic_state_put().
 *
 * This is part of the atomic helper support for nonblocking commits, see
 * drm_atomic_helper_setup_commit() for an overview.
 */
void drm_atomic_helper_commit_cleanup_done(struct drm_atomic_state *old_state)
{
        struct drm_crtc *crtc;
        struct drm_crtc_state *old_crtc_state;
        struct drm_crtc_commit *commit;
        int i;

        for_each_old_crtc_in_state(old_state, crtc, old_crtc_state, i) {
                commit = old_crtc_state->commit;
                if (WARN_ON(!commit))
                        continue;

                complete_all(&commit->cleanup_done);
                WARN_ON(!try_wait_for_completion(&commit->hw_done));

                spin_lock(&crtc->commit_lock);
                list_del(&commit->commit_entry);
                spin_unlock(&crtc->commit_lock);
        }

        if (old_state->fake_commit) {
                complete_all(&old_state->fake_commit->cleanup_done);
                WARN_ON(!try_wait_for_completion(&old_state->fake_commit->hw_done));
        }
}
EXPORT_SYMBOL(drm_atomic_helper_commit_cleanup_done);

/**
 * drm_atomic_helper_prepare_planes - prepare plane resources before commit
 * @dev: DRM device
 * @state: atomic state object with new state structures
 *
 * This function prepares plane state, specifically framebuffers, for the new
 * configuration, by calling &drm_plane_helper_funcs.prepare_fb. If any failure
 * is encountered this function will call &drm_plane_helper_funcs.cleanup_fb on
 * any already successfully prepared framebuffer.
 *
 * Returns:
 * 0 on success, negative error code on failure.
 */
int drm_atomic_helper_prepare_planes(struct drm_device *dev,
                                     struct drm_atomic_state *state)
{
        struct drm_connector *connector;
        struct drm_connector_state *new_conn_state;
        struct drm_plane *plane;
        struct drm_plane_state *new_plane_state;
        int ret, i, j;

        for_each_new_connector_in_state(state, connector, new_conn_state, i) {
                if (!new_conn_state->writeback_job)
                        continue;

                ret = drm_writeback_prepare_job(new_conn_state->writeback_job);
                if (ret < 0)
                        return ret;
        }

        for_each_new_plane_in_state(state, plane, new_plane_state, i) {
                const struct drm_plane_helper_funcs *funcs;

                funcs = plane->helper_private;

                if (funcs->prepare_fb) {
                        ret = funcs->prepare_fb(plane, new_plane_state);
                        if (ret)
                                goto fail;
                } else {
                        WARN_ON_ONCE(funcs->cleanup_fb);

                        if (!drm_core_check_feature(dev, DRIVER_GEM))
                                continue;

                        ret = drm_gem_plane_helper_prepare_fb(plane, new_plane_state);
                        if (ret)
                                goto fail;
                }
        }

        return 0;

fail:
        for_each_new_plane_in_state(state, plane, new_plane_state, j) {
                const struct drm_plane_helper_funcs *funcs;

                if (j >= i)
                        continue;

                funcs = plane->helper_private;

                if (funcs->cleanup_fb)
                        funcs->cleanup_fb(plane, new_plane_state);
        }

        return ret;
}
EXPORT_SYMBOL(drm_atomic_helper_prepare_planes);

static bool plane_crtc_active(const struct drm_plane_state *state)
{
        return state->crtc && state->crtc->state->active;
}

/**
 * drm_atomic_helper_commit_planes - commit plane state
 * @dev: DRM device
 * @old_state: atomic state object with old state structures
 * @flags: flags for committing plane state
 *
 * This function commits the new plane state using the plane and atomic helper
 * functions for planes and CRTCs. It assumes that the atomic state has already
 * been pushed into the relevant object state pointers, since this step can no
 * longer fail.
 *
 * It still requires the global state object @old_state to know which planes and
 * crtcs need to be updated though.
 *
 * Note that this function does all plane updates across all CRTCs in one step.
 * If the hardware can't support this approach look at
 * drm_atomic_helper_commit_planes_on_crtc() instead.
 *
 * Plane parameters can be updated by applications while the associated CRTC is
 * disabled. The DRM/KMS core will store the parameters in the plane state,
 * which will be available to the driver when the CRTC is turned on. As a result
 * most drivers don't need to be immediately notified of plane updates for a
 * disabled CRTC.
 *
 * Unless otherwise needed, drivers are advised to set the ACTIVE_ONLY flag in
 * @flags in order not to receive plane update notifications related to a
 * disabled CRTC. This avoids the need to manually ignore plane updates in
 * driver code when the driver and/or hardware can't or just don't need to deal
 * with updates on disabled CRTCs, for example when supporting runtime PM.
 *
 * Drivers may set the NO_DISABLE_AFTER_MODESET flag in @flags if the relevant
 * display controllers require to disable a CRTC's planes when the CRTC is
 * disabled. This function would skip the &drm_plane_helper_funcs.atomic_disable
 * call for a plane if the CRTC of the old plane state needs a modesetting
 * operation. Of course, the drivers need to disable the planes in their CRTC
 * disable callbacks since no one else would do that.
 *
 * The drm_atomic_helper_commit() default implementation doesn't set the
 * ACTIVE_ONLY flag to most closely match the behaviour of the legacy helpers.
 * This should not be copied blindly by drivers.
 */
void drm_atomic_helper_commit_planes(struct drm_device *dev,
                                     struct drm_atomic_state *old_state,
                                     uint32_t flags)
{
        struct drm_crtc *crtc;
        struct drm_crtc_state *old_crtc_state, *new_crtc_state;
        struct drm_plane *plane;
        struct drm_plane_state *old_plane_state, *new_plane_state;
        int i;
        bool active_only = flags & DRM_PLANE_COMMIT_ACTIVE_ONLY;
        bool no_disable = flags & DRM_PLANE_COMMIT_NO_DISABLE_AFTER_MODESET;

        for_each_oldnew_crtc_in_state(old_state, crtc, old_crtc_state, new_crtc_state, i) {
                const struct drm_crtc_helper_funcs *funcs;

                funcs = crtc->helper_private;

                if (!funcs || !funcs->atomic_begin)
                        continue;

                if (active_only && !new_crtc_state->active)
                        continue;

                funcs->atomic_begin(crtc, old_state);
        }

        for_each_oldnew_plane_in_state(old_state, plane, old_plane_state, new_plane_state, i) {
                const struct drm_plane_helper_funcs *funcs;
                bool disabling;

                funcs = plane->helper_private;

                if (!funcs)
                        continue;

                disabling = drm_atomic_plane_disabling(old_plane_state,
                                                       new_plane_state);

                if (active_only) {
                        /*
                         * Skip planes related to inactive CRTCs. If the plane
                         * is enabled use the state of the current CRTC. If the
                         * plane is being disabled use the state of the old
                         * CRTC to avoid skipping planes being disabled on an
                         * active CRTC.
                         */
                        if (!disabling && !plane_crtc_active(new_plane_state))
                                continue;
                        if (disabling && !plane_crtc_active(old_plane_state))
                                continue;
                }

                /*
                 * Special-case disabling the plane if drivers support it.
                 */
                if (disabling && funcs->atomic_disable) {
                        struct drm_crtc_state *crtc_state;

                        crtc_state = old_plane_state->crtc->state;

                        if (drm_atomic_crtc_needs_modeset(crtc_state) &&
                            no_disable)
                                continue;

                        funcs->atomic_disable(plane, old_state);
                } else if (new_plane_state->crtc || disabling) {
                        funcs->atomic_update(plane, old_state);
                }
        }

        for_each_oldnew_crtc_in_state(old_state, crtc, old_crtc_state, new_crtc_state, i) {
                const struct drm_crtc_helper_funcs *funcs;

                funcs = crtc->helper_private;

                if (!funcs || !funcs->atomic_flush)
                        continue;

                if (active_only && !new_crtc_state->active)
                        continue;

                funcs->atomic_flush(crtc, old_state);
        }
}
EXPORT_SYMBOL(drm_atomic_helper_commit_planes);

/**
 * drm_atomic_helper_commit_planes_on_crtc - commit plane state for a CRTC
 * @old_crtc_state: atomic state object with the old CRTC state
 *
 * This function commits the new plane state using the plane and atomic helper
 * functions for planes on the specific CRTC. It assumes that the atomic state
 * has already been pushed into the relevant object state pointers, since this
 * step can no longer fail.
 *
 * This function is useful when plane updates should be done CRTC-by-CRTC
 * instead of one global step like drm_atomic_helper_commit_planes() does.
 *
 * This function can only be savely used when planes are not allowed to move
 * between different CRTCs because this function doesn't handle inter-CRTC
 * dependencies. Callers need to ensure that either no such dependencies exist,
 * resolve them through ordering of commit calls or through some other means.
 */
void
drm_atomic_helper_commit_planes_on_crtc(struct drm_crtc_state *old_crtc_state)
{
        const struct drm_crtc_helper_funcs *crtc_funcs;
        struct drm_crtc *crtc = old_crtc_state->crtc;
        struct drm_atomic_state *old_state = old_crtc_state->state;
        struct drm_crtc_state *new_crtc_state =
                drm_atomic_get_new_crtc_state(old_state, crtc);
        struct drm_plane *plane;
        unsigned int plane_mask;

        plane_mask = old_crtc_state->plane_mask;
        plane_mask |= new_crtc_state->plane_mask;

        crtc_funcs = crtc->helper_private;
        if (crtc_funcs && crtc_funcs->atomic_begin)
                crtc_funcs->atomic_begin(crtc, old_state);

        drm_for_each_plane_mask(plane, crtc->dev, plane_mask) {
                struct drm_plane_state *old_plane_state =
                        drm_atomic_get_old_plane_state(old_state, plane);
                struct drm_plane_state *new_plane_state =
                        drm_atomic_get_new_plane_state(old_state, plane);
                const struct drm_plane_helper_funcs *plane_funcs;

                plane_funcs = plane->helper_private;

                if (!old_plane_state || !plane_funcs)
                        continue;

                WARN_ON(new_plane_state->crtc &&
                        new_plane_state->crtc != crtc);

                if (drm_atomic_plane_disabling(old_plane_state, new_plane_state) &&
                    plane_funcs->atomic_disable)
                        plane_funcs->atomic_disable(plane, old_state);
                else if (new_plane_state->crtc ||
                         drm_atomic_plane_disabling(old_plane_state, new_plane_state))
                        plane_funcs->atomic_update(plane, old_state);
        }

        if (crtc_funcs && crtc_funcs->atomic_flush)
                crtc_funcs->atomic_flush(crtc, old_state);
}
EXPORT_SYMBOL(drm_atomic_helper_commit_planes_on_crtc);

/**
 * drm_atomic_helper_disable_planes_on_crtc - helper to disable CRTC's planes
 * @old_crtc_state: atomic state object with the old CRTC state
 * @atomic: if set, synchronize with CRTC's atomic_begin/flush hooks
 *
 * Disables all planes associated with the given CRTC. This can be
 * used for instance in the CRTC helper atomic_disable callback to disable
 * all planes.
 *
 * If the atomic-parameter is set the function calls the CRTC's
 * atomic_begin hook before and atomic_flush hook after disabling the
 * planes.
 *
 * It is a bug to call this function without having implemented the
 * &drm_plane_helper_funcs.atomic_disable plane hook.
 */
void
drm_atomic_helper_disable_planes_on_crtc(struct drm_crtc_state *old_crtc_state,
                                         bool atomic)
{
        struct drm_crtc *crtc = old_crtc_state->crtc;
        const struct drm_crtc_helper_funcs *crtc_funcs =
                crtc->helper_private;
        struct drm_plane *plane;

        if (atomic && crtc_funcs && crtc_funcs->atomic_begin)
                crtc_funcs->atomic_begin(crtc, NULL);

        drm_atomic_crtc_state_for_each_plane(plane, old_crtc_state) {
                const struct drm_plane_helper_funcs *plane_funcs =
                        plane->helper_private;

                if (!plane_funcs)
                        continue;

                WARN_ON(!plane_funcs->atomic_disable);
                if (plane_funcs->atomic_disable)
                        plane_funcs->atomic_disable(plane, NULL);
        }

        if (atomic && crtc_funcs && crtc_funcs->atomic_flush)
                crtc_funcs->atomic_flush(crtc, NULL);
}
EXPORT_SYMBOL(drm_atomic_helper_disable_planes_on_crtc);

/**
 * drm_atomic_helper_cleanup_planes - cleanup plane resources after commit
 * @dev: DRM device
 * @old_state: atomic state object with old state structures
 *
 * This function cleans up plane state, specifically framebuffers, from the old
 * configuration. Hence the old configuration must be perserved in @old_state to
 * be able to call this function.
 *
 * This function must also be called on the new state when the atomic update
 * fails at any point after calling drm_atomic_helper_prepare_planes().
 */
void drm_atomic_helper_cleanup_planes(struct drm_device *dev,
                                      struct drm_atomic_state *old_state)
{
        struct drm_plane *plane;
        struct drm_plane_state *old_plane_state, *new_plane_state;
        int i;

        for_each_oldnew_plane_in_state(old_state, plane, old_plane_state, new_plane_state, i) {
                const struct drm_plane_helper_funcs *funcs;
                struct drm_plane_state *plane_state;

                /*
                 * This might be called before swapping when commit is aborted,
                 * in which case we have to cleanup the new state.
                 */
                if (old_plane_state == plane->state)
                        plane_state = new_plane_state;
                else
                        plane_state = old_plane_state;

                funcs = plane->helper_private;

                if (funcs->cleanup_fb)
                        funcs->cleanup_fb(plane, plane_state);
        }
}
EXPORT_SYMBOL(drm_atomic_helper_cleanup_planes);

/**
 * drm_atomic_helper_swap_state - store atomic state into current sw state
 * @state: atomic state
 * @stall: stall for preceding commits
 *
 * This function stores the atomic state into the current state pointers in all
 * driver objects. It should be called after all failing steps have been done
 * and succeeded, but before the actual hardware state is committed.
 *
 * For cleanup and error recovery the current state for all changed objects will
 * be swapped into @state.
 *
 * With that sequence it fits perfectly into the plane prepare/cleanup sequence:
 *
 * 1. Call drm_atomic_helper_prepare_planes() with the staged atomic state.
 *
 * 2. Do any other steps that might fail.
 *
 * 3. Put the staged state into the current state pointers with this function.
 *
 * 4. Actually commit the hardware state.
 *
 * 5. Call drm_atomic_helper_cleanup_planes() with @state, which since step 3
 * contains the old state. Also do any other cleanup required with that state.
 *
 * @stall must be set when nonblocking commits for this driver directly access
 * the &drm_plane.state, &drm_crtc.state or &drm_connector.state pointer. With
 * the current atomic helpers this is almost always the case, since the helpers
 * don't pass the right state structures to the callbacks.
 *
 * Returns:
 *
 * Returns 0 on success. Can return -ERESTARTSYS when @stall is true and the
 * waiting for the previous commits has been interrupted.
 */
int drm_atomic_helper_swap_state(struct drm_atomic_state *state,
                                  bool stall)
{
        int i, ret;
        struct drm_connector *connector;
        struct drm_connector_state *old_conn_state, *new_conn_state;
        struct drm_crtc *crtc;
        struct drm_crtc_state *old_crtc_state, *new_crtc_state;
        struct drm_plane *plane;
        struct drm_plane_state *old_plane_state, *new_plane_state;
        struct drm_crtc_commit *commit;
        struct drm_private_obj *obj;
        struct drm_private_state *old_obj_state, *new_obj_state;

        if (stall) {
                /*
                 * We have to stall for hw_done here before
                 * drm_atomic_helper_wait_for_dependencies() because flip
                 * depth > 1 is not yet supported by all drivers. As long as
                 * obj->state is directly dereferenced anywhere in the drivers
                 * atomic_commit_tail function, then it's unsafe to swap state
                 * before drm_atomic_helper_commit_hw_done() is called.
                 */

                for_each_old_crtc_in_state(state, crtc, old_crtc_state, i) {
                        commit = old_crtc_state->commit;

                        if (!commit)
                                continue;

                        ret = wait_for_completion_interruptible(&commit->hw_done);
                        if (ret)
                                return ret;
                }

                for_each_old_connector_in_state(state, connector, old_conn_state, i) {
                        commit = old_conn_state->commit;

                        if (!commit)
                                continue;

                        ret = wait_for_completion_interruptible(&commit->hw_done);
                        if (ret)
                                return ret;
                }

                for_each_old_plane_in_state(state, plane, old_plane_state, i) {
                        commit = old_plane_state->commit;

                        if (!commit)
                                continue;

                        ret = wait_for_completion_interruptible(&commit->hw_done);
                        if (ret)
                                return ret;
                }
        }

        for_each_oldnew_connector_in_state(state, connector, old_conn_state, new_conn_state, i) {
                WARN_ON(connector->state != old_conn_state);

                old_conn_state->state = state;
                new_conn_state->state = NULL;

                state->connectors[i].state = old_conn_state;
                connector->state = new_conn_state;
        }

        for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) {
                WARN_ON(crtc->state != old_crtc_state);

                old_crtc_state->state = state;
                new_crtc_state->state = NULL;

                state->crtcs[i].state = old_crtc_state;
                crtc->state = new_crtc_state;

                if (new_crtc_state->commit) {
                        spin_lock(&crtc->commit_lock);
                        list_add(&new_crtc_state->commit->commit_entry,
                                 &crtc->commit_list);
                        spin_unlock(&crtc->commit_lock);

                        new_crtc_state->commit->event = NULL;
                }
        }

        for_each_oldnew_plane_in_state(state, plane, old_plane_state, new_plane_state, i) {
                WARN_ON(plane->state != old_plane_state);

                old_plane_state->state = state;
                new_plane_state->state = NULL;

                state->planes[i].state = old_plane_state;
                plane->state = new_plane_state;
        }

        for_each_oldnew_private_obj_in_state(state, obj, old_obj_state, new_obj_state, i) {
                WARN_ON(obj->state != old_obj_state);

                old_obj_state->state = state;
                new_obj_state->state = NULL;

                state->private_objs[i].state = old_obj_state;
                obj->state = new_obj_state;
        }

        return 0;
}
EXPORT_SYMBOL(drm_atomic_helper_swap_state);

/**
 * drm_atomic_helper_update_plane - Helper for primary plane update using atomic
 * @plane: plane object to update
 * @crtc: owning CRTC of owning plane
 * @fb: framebuffer to flip onto plane
 * @crtc_x: x offset of primary plane on @crtc
 * @crtc_y: y offset of primary plane on @crtc
 * @crtc_w: width of primary plane rectangle on @crtc
 * @crtc_h: height of primary plane rectangle on @crtc
 * @src_x: x offset of @fb for panning
 * @src_y: y offset of @fb for panning
 * @src_w: width of source rectangle in @fb
 * @src_h: height of source rectangle in @fb
 * @ctx: lock acquire context
 *
 * Provides a default plane update handler using the atomic driver interface.
 *
 * RETURNS:
 * Zero on success, error code on failure
 */
int drm_atomic_helper_update_plane(struct drm_plane *plane,
                                   struct drm_crtc *crtc,
                                   struct drm_framebuffer *fb,
                                   int crtc_x, int crtc_y,
                                   unsigned int crtc_w, unsigned int crtc_h,
                                   uint32_t src_x, uint32_t src_y,
                                   uint32_t src_w, uint32_t src_h,
                                   struct drm_modeset_acquire_ctx *ctx)
{
        struct drm_atomic_state *state;
        struct drm_plane_state *plane_state;
        int ret = 0;

        state = drm_atomic_state_alloc(plane->dev);
        if (!state)
                return -ENOMEM;

        state->acquire_ctx = ctx;
        plane_state = drm_atomic_get_plane_state(state, plane);
        if (IS_ERR(plane_state)) {
                ret = PTR_ERR(plane_state);
                goto fail;
        }

        ret = drm_atomic_set_crtc_for_plane(plane_state, crtc);
        if (ret != 0)
                goto fail;
        drm_atomic_set_fb_for_plane(plane_state, fb);
        plane_state->crtc_x = crtc_x;
        plane_state->crtc_y = crtc_y;
        plane_state->crtc_w = crtc_w;
        plane_state->crtc_h = crtc_h;
        plane_state->src_x = src_x;
        plane_state->src_y = src_y;
        plane_state->src_w = src_w;
        plane_state->src_h = src_h;

        if (plane == crtc->cursor)
                state->legacy_cursor_update = true;

        ret = drm_atomic_commit(state);
fail:
        drm_atomic_state_put(state);
        return ret;
}
EXPORT_SYMBOL(drm_atomic_helper_update_plane);

/**
 * drm_atomic_helper_disable_plane - Helper for primary plane disable using * atomic
 * @plane: plane to disable
 * @ctx: lock acquire context
 *
 * Provides a default plane disable handler using the atomic driver interface.
 *
 * RETURNS:
 * Zero on success, error code on failure
 */
int drm_atomic_helper_disable_plane(struct drm_plane *plane,
                                    struct drm_modeset_acquire_ctx *ctx)
{
        struct drm_atomic_state *state;
        struct drm_plane_state *plane_state;
        int ret = 0;

        state = drm_atomic_state_alloc(plane->dev);
        if (!state)
                return -ENOMEM;

        state->acquire_ctx = ctx;
        plane_state = drm_atomic_get_plane_state(state, plane);
        if (IS_ERR(plane_state)) {
                ret = PTR_ERR(plane_state);
                goto fail;
        }

        if (plane_state->crtc && plane_state->crtc->cursor == plane)
                plane_state->state->legacy_cursor_update = true;

        ret = __drm_atomic_helper_disable_plane(plane, plane_state);
        if (ret != 0)
                goto fail;

        ret = drm_atomic_commit(state);
fail:
        drm_atomic_state_put(state);
        return ret;
}
EXPORT_SYMBOL(drm_atomic_helper_disable_plane);

/**
 * drm_atomic_helper_set_config - set a new config from userspace
 * @set: mode set configuration
 * @ctx: lock acquisition context
 *
 * Provides a default CRTC set_config handler using the atomic driver interface.
 *
 * NOTE: For backwards compatibility with old userspace this automatically
 * resets the "link-status" property to GOOD, to force any link
 * re-training. The SETCRTC ioctl does not define whether an update does
 * need a full modeset or just a plane update, hence we're allowed to do
 * that. See also drm_connector_set_link_status_property().
 *
 * Returns:
 * Returns 0 on success, negative errno numbers on failure.
 */
int drm_atomic_helper_set_config(struct drm_mode_set *set,
                                 struct drm_modeset_acquire_ctx *ctx)
{
        struct drm_atomic_state *state;
        struct drm_crtc *crtc = set->crtc;
        int ret = 0;

        state = drm_atomic_state_alloc(crtc->dev);
        if (!state)
                return -ENOMEM;

        state->acquire_ctx = ctx;
        ret = __drm_atomic_helper_set_config(set, state);
        if (ret != 0)
                goto fail;

        ret = handle_conflicting_encoders(state, true);
        if (ret)
                goto fail;

        ret = drm_atomic_commit(state);

fail:
        drm_atomic_state_put(state);
        return ret;
}
EXPORT_SYMBOL(drm_atomic_helper_set_config);

/**
 * drm_atomic_helper_disable_all - disable all currently active outputs
 * @dev: DRM device
 * @ctx: lock acquisition context
 *
 * Loops through all connectors, finding those that aren't turned off and then
 * turns them off by setting their DPMS mode to OFF and deactivating the CRTC
 * that they are connected to.
 *
 * This is used for example in suspend/resume to disable all currently active
 * functions when suspending. If you just want to shut down everything at e.g.
 * driver unload, look at drm_atomic_helper_shutdown().
 *
 * Note that if callers haven't already acquired all modeset locks this might
 * return -EDEADLK, which must be handled by calling drm_modeset_backoff().
 *
 * Returns:
 * 0 on success or a negative error code on failure.
 *
 * See also:
 * drm_atomic_helper_suspend(), drm_atomic_helper_resume() and
 * drm_atomic_helper_shutdown().
 */
int drm_atomic_helper_disable_all(struct drm_device *dev,
                                  struct drm_modeset_acquire_ctx *ctx)
{
        struct drm_atomic_state *state;
        struct drm_connector_state *conn_state;
        struct drm_connector *conn;
        struct drm_plane_state *plane_state;
        struct drm_plane *plane;
        struct drm_crtc_state *crtc_state;
        struct drm_crtc *crtc;
        int ret, i;

        state = drm_atomic_state_alloc(dev);
        if (!state)
                return -ENOMEM;

        state->acquire_ctx = ctx;

        drm_for_each_crtc(crtc, dev) {
                crtc_state = drm_atomic_get_crtc_state(state, crtc);
                if (IS_ERR(crtc_state)) {
                        ret = PTR_ERR(crtc_state);
                        goto free;
                }

                crtc_state->active = false;

                ret = drm_atomic_set_mode_prop_for_crtc(crtc_state, NULL);
                if (ret < 0)
                        goto free;

                ret = drm_atomic_add_affected_planes(state, crtc);
                if (ret < 0)
                        goto free;

                ret = drm_atomic_add_affected_connectors(state, crtc);
                if (ret < 0)
                        goto free;
        }

        for_each_new_connector_in_state(state, conn, conn_state, i) {
                ret = drm_atomic_set_crtc_for_connector(conn_state, NULL);
                if (ret < 0)
                        goto free;
        }

        for_each_new_plane_in_state(state, plane, plane_state, i) {
                ret = drm_atomic_set_crtc_for_plane(plane_state, NULL);
                if (ret < 0)
                        goto free;

                drm_atomic_set_fb_for_plane(plane_state, NULL);
        }

        ret = drm_atomic_commit(state);
free:
        drm_atomic_state_put(state);
        return ret;
}
EXPORT_SYMBOL(drm_atomic_helper_disable_all);

/**
 * drm_atomic_helper_shutdown - shutdown all CRTC
 * @dev: DRM device
 *
 * This shuts down all CRTC, which is useful for driver unloading. Shutdown on
 * suspend should instead be handled with drm_atomic_helper_suspend(), since
 * that also takes a snapshot of the modeset state to be restored on resume.
 *
 * This is just a convenience wrapper around drm_atomic_helper_disable_all(),
 * and it is the atomic version of drm_crtc_force_disable_all().
 */
void drm_atomic_helper_shutdown(struct drm_device *dev)
{
        struct drm_modeset_acquire_ctx ctx;
        int ret;

        DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, 0, ret);

        ret = drm_atomic_helper_disable_all(dev, &ctx);
        if (ret)
                drm_err(dev,
                        "Disabling all crtc's during unload failed with %i\n",
                        ret);

        DRM_MODESET_LOCK_ALL_END(dev, ctx, ret);
}
EXPORT_SYMBOL(drm_atomic_helper_shutdown);

/**
 * drm_atomic_helper_duplicate_state - duplicate an atomic state object
 * @dev: DRM device
 * @ctx: lock acquisition context
 *
 * Makes a copy of the current atomic state by looping over all objects and
 * duplicating their respective states. This is used for example by suspend/
 * resume support code to save the state prior to suspend such that it can
 * be restored upon resume.
 *
 * Note that this treats atomic state as persistent between save and restore.
 * Drivers must make sure that this is possible and won't result in confusion
 * or erroneous behaviour.
 *
 * Note that if callers haven't already acquired all modeset locks this might
 * return -EDEADLK, which must be handled by calling drm_modeset_backoff().
 *
 * Returns:
 * A pointer to the copy of the atomic state object on success or an
 * ERR_PTR()-encoded error code on failure.
 *
 * See also:
 * drm_atomic_helper_suspend(), drm_atomic_helper_resume()
 */
struct drm_atomic_state *
drm_atomic_helper_duplicate_state(struct drm_device *dev,
                                  struct drm_modeset_acquire_ctx *ctx)
{
        struct drm_atomic_state *state;
        struct drm_connector *conn;
        struct drm_connector_list_iter conn_iter;
        struct drm_plane *plane;
        struct drm_crtc *crtc;
        int err = 0;

        state = drm_atomic_state_alloc(dev);
        if (!state)
                return ERR_PTR(-ENOMEM);

        state->acquire_ctx = ctx;
        state->duplicated = true;

        drm_for_each_crtc(crtc, dev) {
                struct drm_crtc_state *crtc_state;

                crtc_state = drm_atomic_get_crtc_state(state, crtc);
                if (IS_ERR(crtc_state)) {
                        err = PTR_ERR(crtc_state);
                        goto free;
                }
        }

        drm_for_each_plane(plane, dev) {
                struct drm_plane_state *plane_state;

                plane_state = drm_atomic_get_plane_state(state, plane);
                if (IS_ERR(plane_state)) {
                        err = PTR_ERR(plane_state);
                        goto free;
                }
        }

        drm_connector_list_iter_begin(dev, &conn_iter);
        drm_for_each_connector_iter(conn, &conn_iter) {
                struct drm_connector_state *conn_state;

                conn_state = drm_atomic_get_connector_state(state, conn);
                if (IS_ERR(conn_state)) {
                        err = PTR_ERR(conn_state);
                        drm_connector_list_iter_end(&conn_iter);
                        goto free;
                }
        }
        drm_connector_list_iter_end(&conn_iter);

        /* clear the acquire context so that it isn't accidentally reused */
        state->acquire_ctx = NULL;

free:
        if (err < 0) {
                drm_atomic_state_put(state);
                state = ERR_PTR(err);
        }

        return state;
}
EXPORT_SYMBOL(drm_atomic_helper_duplicate_state);

/**
 * drm_atomic_helper_suspend - subsystem-level suspend helper
 * @dev: DRM device
 *
 * Duplicates the current atomic state, disables all active outputs and then
 * returns a pointer to the original atomic state to the caller. Drivers can
 * pass this pointer to the drm_atomic_helper_resume() helper upon resume to
 * restore the output configuration that was active at the time the system
 * entered suspend.
 *
 * Note that it is potentially unsafe to use this. The atomic state object
 * returned by this function is assumed to be persistent. Drivers must ensure
 * that this holds true. Before calling this function, drivers must make sure
 * to suspend fbdev emulation so that nothing can be using the device.
 *
 * Returns:
 * A pointer to a copy of the state before suspend on success or an ERR_PTR()-
 * encoded error code on failure. Drivers should store the returned atomic
 * state object and pass it to the drm_atomic_helper_resume() helper upon
 * resume.
 *
 * See also:
 * drm_atomic_helper_duplicate_state(), drm_atomic_helper_disable_all(),
 * drm_atomic_helper_resume(), drm_atomic_helper_commit_duplicated_state()
 */
struct drm_atomic_state *drm_atomic_helper_suspend(struct drm_device *dev)
{
        struct drm_modeset_acquire_ctx ctx;
        struct drm_atomic_state *state;
        int err;

        /* This can never be returned, but it makes the compiler happy */
        state = ERR_PTR(-EINVAL);

        DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, 0, err);

        state = drm_atomic_helper_duplicate_state(dev, &ctx);
        if (IS_ERR(state))
                goto unlock;

        err = drm_atomic_helper_disable_all(dev, &ctx);
        if (err < 0) {
                drm_atomic_state_put(state);
                state = ERR_PTR(err);
                goto unlock;
        }

unlock:
        DRM_MODESET_LOCK_ALL_END(dev, ctx, err);
        if (err)
                return ERR_PTR(err);

        return state;
}
EXPORT_SYMBOL(drm_atomic_helper_suspend);

/**
 * drm_atomic_helper_commit_duplicated_state - commit duplicated state
 * @state: duplicated atomic state to commit
 * @ctx: pointer to acquire_ctx to use for commit.
 *
 * The state returned by drm_atomic_helper_duplicate_state() and
 * drm_atomic_helper_suspend() is partially invalid, and needs to
 * be fixed up before commit.
 *
 * Returns:
 * 0 on success or a negative error code on failure.
 *
 * See also:
 * drm_atomic_helper_suspend()
 */
int drm_atomic_helper_commit_duplicated_state(struct drm_atomic_state *state,
                                              struct drm_modeset_acquire_ctx *ctx)
{
        int i, ret;
        struct drm_plane *plane;
        struct drm_plane_state *new_plane_state;
        struct drm_connector *connector;
        struct drm_connector_state *new_conn_state;
        struct drm_crtc *crtc;
        struct drm_crtc_state *new_crtc_state;

        state->acquire_ctx = ctx;

        for_each_new_plane_in_state(state, plane, new_plane_state, i)
                state->planes[i].old_state = plane->state;

        for_each_new_crtc_in_state(state, crtc, new_crtc_state, i)
                state->crtcs[i].old_state = crtc->state;

        for_each_new_connector_in_state(state, connector, new_conn_state, i)
                state->connectors[i].old_state = connector->state;

        ret = drm_atomic_commit(state);

        state->acquire_ctx = NULL;

        return ret;
}
EXPORT_SYMBOL(drm_atomic_helper_commit_duplicated_state);

/**
 * drm_atomic_helper_resume - subsystem-level resume helper
 * @dev: DRM device
 * @state: atomic state to resume to
 *
 * Calls drm_mode_config_reset() to synchronize hardware and software states,
 * grabs all modeset locks and commits the atomic state object. This can be
 * used in conjunction with the drm_atomic_helper_suspend() helper to
 * implement suspend/resume for drivers that support atomic mode-setting.
 *
 * Returns:
 * 0 on success or a negative error code on failure.
 *
 * See also:
 * drm_atomic_helper_suspend()
 */
int drm_atomic_helper_resume(struct drm_device *dev,
                             struct drm_atomic_state *state)
{
        struct drm_modeset_acquire_ctx ctx;
        int err;

        drm_mode_config_reset(dev);

        DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, 0, err);

        err = drm_atomic_helper_commit_duplicated_state(state, &ctx);

        DRM_MODESET_LOCK_ALL_END(dev, ctx, err);
        drm_atomic_state_put(state);

        return err;
}
EXPORT_SYMBOL(drm_atomic_helper_resume);

static int page_flip_common(struct drm_atomic_state *state,
                            struct drm_crtc *crtc,
                            struct drm_framebuffer *fb,
                            struct drm_pending_vblank_event *event,
                            uint32_t flags)
{
        struct drm_plane *plane = crtc->primary;
        struct drm_plane_state *plane_state;
        struct drm_crtc_state *crtc_state;
        int ret = 0;

        crtc_state = drm_atomic_get_crtc_state(state, crtc);
        if (IS_ERR(crtc_state))
                return PTR_ERR(crtc_state);

        crtc_state->event = event;
        crtc_state->async_flip = flags & DRM_MODE_PAGE_FLIP_ASYNC;

        plane_state = drm_atomic_get_plane_state(state, plane);
        if (IS_ERR(plane_state))
                return PTR_ERR(plane_state);

        ret = drm_atomic_set_crtc_for_plane(plane_state, crtc);
        if (ret != 0)
                return ret;
        drm_atomic_set_fb_for_plane(plane_state, fb);

        /* Make sure we don't accidentally do a full modeset. */
        state->allow_modeset = false;
        if (!crtc_state->active) {
                drm_dbg_atomic(crtc->dev,
                               "[CRTC:%d:%s] disabled, rejecting legacy flip\n",
                               crtc->base.id, crtc->name);
                return -EINVAL;
        }

        return ret;
}

/**
 * drm_atomic_helper_page_flip - execute a legacy page flip
 * @crtc: DRM CRTC
 * @fb: DRM framebuffer
 * @event: optional DRM event to signal upon completion
 * @flags: flip flags for non-vblank sync'ed updates
 * @ctx: lock acquisition context
 *
 * Provides a default &drm_crtc_funcs.page_flip implementation
 * using the atomic driver interface.
 *
 * Returns:
 * Returns 0 on success, negative errno numbers on failure.
 *
 * See also:
 * drm_atomic_helper_page_flip_target()
 */
int drm_atomic_helper_page_flip(struct drm_crtc *crtc,
                                struct drm_framebuffer *fb,
                                struct drm_pending_vblank_event *event,
                                uint32_t flags,
                                struct drm_modeset_acquire_ctx *ctx)
{
        struct drm_plane *plane = crtc->primary;
        struct drm_atomic_state *state;
        int ret = 0;

        state = drm_atomic_state_alloc(plane->dev);
        if (!state)
                return -ENOMEM;

        state->acquire_ctx = ctx;

        ret = page_flip_common(state, crtc, fb, event, flags);
        if (ret != 0)
                goto fail;

        ret = drm_atomic_nonblocking_commit(state);
fail:
        drm_atomic_state_put(state);
        return ret;
}
EXPORT_SYMBOL(drm_atomic_helper_page_flip);

/**
 * drm_atomic_helper_page_flip_target - do page flip on target vblank period.
 * @crtc: DRM CRTC
 * @fb: DRM framebuffer
 * @event: optional DRM event to signal upon completion
 * @flags: flip flags for non-vblank sync'ed updates
 * @target: specifying the target vblank period when the flip to take effect
 * @ctx: lock acquisition context
 *
 * Provides a default &drm_crtc_funcs.page_flip_target implementation.
 * Similar to drm_atomic_helper_page_flip() with extra parameter to specify
 * target vblank period to flip.
 *
 * Returns:
 * Returns 0 on success, negative errno numbers on failure.
 */
int drm_atomic_helper_page_flip_target(struct drm_crtc *crtc,
                                       struct drm_framebuffer *fb,
                                       struct drm_pending_vblank_event *event,
                                       uint32_t flags,
                                       uint32_t target,
                                       struct drm_modeset_acquire_ctx *ctx)
{
        struct drm_plane *plane = crtc->primary;
        struct drm_atomic_state *state;
        struct drm_crtc_state *crtc_state;
        int ret = 0;

        state = drm_atomic_state_alloc(plane->dev);
        if (!state)
                return -ENOMEM;

        state->acquire_ctx = ctx;

        ret = page_flip_common(state, crtc, fb, event, flags);
        if (ret != 0)
                goto fail;

        crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
        if (WARN_ON(!crtc_state)) {
                ret = -EINVAL;
                goto fail;
        }
        crtc_state->target_vblank = target;

        ret = drm_atomic_nonblocking_commit(state);
fail:
        drm_atomic_state_put(state);
        return ret;
}
EXPORT_SYMBOL(drm_atomic_helper_page_flip_target);

/**
 * drm_atomic_helper_bridge_propagate_bus_fmt() - Propagate output format to
 *                                                the input end of a bridge
 * @bridge: bridge control structure
 * @bridge_state: new bridge state
 * @crtc_state: new CRTC state
 * @conn_state: new connector state
 * @output_fmt: tested output bus format
 * @num_input_fmts: will contain the size of the returned array
 *
 * This helper is a pluggable implementation of the
 * &drm_bridge_funcs.atomic_get_input_bus_fmts operation for bridges that don't
 * modify the bus configuration between their input and their output. It
 * returns an array of input formats with a single element set to @output_fmt.
 *
 * RETURNS:
 * a valid format array of size @num_input_fmts, or NULL if the allocation
 * failed
 */
u32 *
drm_atomic_helper_bridge_propagate_bus_fmt(struct drm_bridge *bridge,
                                        struct drm_bridge_state *bridge_state,
                                        struct drm_crtc_state *crtc_state,
                                        struct drm_connector_state *conn_state,
                                        u32 output_fmt,
                                        unsigned int *num_input_fmts)
{
        u32 *input_fmts;

        input_fmts = kzalloc(sizeof(*input_fmts), GFP_KERNEL);
        if (!input_fmts) {
                *num_input_fmts = 0;
                return NULL;
        }

        *num_input_fmts = 1;
        input_fmts[0] = output_fmt;
        return input_fmts;
}
EXPORT_SYMBOL(drm_atomic_helper_bridge_propagate_bus_fmt);