Merge tag 'net-5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

[linux.git] / drivers / net / ipa / gsi.c

// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2015-2018, The Linux Foundation. All rights reserved.
 * Copyright (C) 2018-2021 Linaro Ltd.
 */

#include <linux/types.h>
#include <linux/bits.h>
#include <linux/bitfield.h>
#include <linux/mutex.h>
#include <linux/completion.h>
#include <linux/io.h>
#include <linux/bug.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
#include <linux/netdevice.h>

#include "gsi.h"
#include "gsi_reg.h"
#include "gsi_private.h"
#include "gsi_trans.h"
#include "ipa_gsi.h"
#include "ipa_data.h"
#include "ipa_version.h"

/**
 * DOC: The IPA Generic Software Interface
 *
 * The generic software interface (GSI) is an integral component of the IPA,
 * providing a well-defined communication layer between the AP subsystem
 * and the IPA core.  The modem uses the GSI layer as well.
 *
 *      --------             ---------
 *      |      |             |       |
 *      |  AP  +<---.   .----+ Modem |
 *      |      +--. |   | .->+       |
 *      |      |  | |   | |  |       |
 *      --------  | |   | |  ---------
 *                v |   v |
 *              --+-+---+-+--
 *              |    GSI    |
 *              |-----------|
 *              |           |
 *              |    IPA    |
 *              |           |
 *              -------------
 *
 * In the above diagram, the AP and Modem represent "execution environments"
 * (EEs), which are independent operating environments that use the IPA for
 * data transfer.
 *
 * Each EE uses a set of unidirectional GSI "channels," which allow transfer
 * of data to or from the IPA.  A channel is implemented as a ring buffer,
 * with a DRAM-resident array of "transfer elements" (TREs) available to
 * describe transfers to or from other EEs through the IPA.  A transfer
 * element can also contain an immediate command, requesting the IPA perform
 * actions other than data transfer.
 *
 * Each TRE refers to a block of data--also located DRAM.  After writing one
 * or more TREs to a channel, the writer (either the IPA or an EE) writes a
 * doorbell register to inform the receiving side how many elements have
 * been written.
 *
 * Each channel has a GSI "event ring" associated with it.  An event ring
 * is implemented very much like a channel ring, but is always directed from
 * the IPA to an EE.  The IPA notifies an EE (such as the AP) about channel
 * events by adding an entry to the event ring associated with the channel.
 * The GSI then writes its doorbell for the event ring, causing the target
 * EE to be interrupted.  Each entry in an event ring contains a pointer
 * to the channel TRE whose completion the event represents.
 *
 * Each TRE in a channel ring has a set of flags.  One flag indicates whether
 * the completion of the transfer operation generates an entry (and possibly
 * an interrupt) in the channel's event ring.  Other flags allow transfer
 * elements to be chained together, forming a single logical transaction.
 * TRE flags are used to control whether and when interrupts are generated
 * to signal completion of channel transfers.
 *
 * Elements in channel and event rings are completed (or consumed) strictly
 * in order.  Completion of one entry implies the completion of all preceding
 * entries.  A single completion interrupt can therefore communicate the
 * completion of many transfers.
 *
 * Note that all GSI registers are little-endian, which is the assumed
 * endianness of I/O space accesses.  The accessor functions perform byte
 * swapping if needed (i.e., for a big endian CPU).
 */

/* Delay period for interrupt moderation (in 32KHz IPA internal timer ticks) */
#define GSI_EVT_RING_INT_MODT           (32 * 1) /* 1ms under 32KHz clock */

#define GSI_CMD_TIMEOUT                 50      /* milliseconds */

#define GSI_CHANNEL_STOP_RETRIES        10
#define GSI_CHANNEL_MODEM_HALT_RETRIES  10

#define GSI_MHI_EVENT_ID_START          10      /* 1st reserved event id */
#define GSI_MHI_EVENT_ID_END            16      /* Last reserved event id */

#define GSI_ISR_MAX_ITER                50      /* Detect interrupt storms */

/* An entry in an event ring */
struct gsi_event {
        __le64 xfer_ptr;
        __le16 len;
        u8 reserved1;
        u8 code;
        __le16 reserved2;
        u8 type;
        u8 chid;
};

/** gsi_channel_scratch_gpi - GPI protocol scratch register
 * @max_outstanding_tre:
 *      Defines the maximum number of TREs allowed in a single transaction
 *      on a channel (in bytes).  This determines the amount of prefetch
 *      performed by the hardware.  We configure this to equal the size of
 *      the TLV FIFO for the channel.
 * @outstanding_threshold:
 *      Defines the threshold (in bytes) determining when the sequencer
 *      should update the channel doorbell.  We configure this to equal
 *      the size of two TREs.
 */
struct gsi_channel_scratch_gpi {
        u64 reserved1;
        u16 reserved2;
        u16 max_outstanding_tre;
        u16 reserved3;
        u16 outstanding_threshold;
};

/** gsi_channel_scratch - channel scratch configuration area
 *
 * The exact interpretation of this register is protocol-specific.
 * We only use GPI channels; see struct gsi_channel_scratch_gpi, above.
 */
union gsi_channel_scratch {
        struct gsi_channel_scratch_gpi gpi;
        struct {
                u32 word1;
                u32 word2;
                u32 word3;
                u32 word4;
        } data;
};

/* Check things that can be validated at build time. */
static void gsi_validate_build(void)
{
        /* This is used as a divisor */
        BUILD_BUG_ON(!GSI_RING_ELEMENT_SIZE);

        /* Code assumes the size of channel and event ring element are
         * the same (and fixed).  Make sure the size of an event ring
         * element is what's expected.
         */
        BUILD_BUG_ON(sizeof(struct gsi_event) != GSI_RING_ELEMENT_SIZE);

        /* Hardware requires a 2^n ring size.  We ensure the number of
         * elements in an event ring is a power of 2 elsewhere; this
         * ensure the elements themselves meet the requirement.
         */
        BUILD_BUG_ON(!is_power_of_2(GSI_RING_ELEMENT_SIZE));

        /* The channel element size must fit in this field */
        BUILD_BUG_ON(GSI_RING_ELEMENT_SIZE > field_max(ELEMENT_SIZE_FMASK));

        /* The event ring element size must fit in this field */
        BUILD_BUG_ON(GSI_RING_ELEMENT_SIZE > field_max(EV_ELEMENT_SIZE_FMASK));
}

/* Return the channel id associated with a given channel */
static u32 gsi_channel_id(struct gsi_channel *channel)
{
        return channel - &channel->gsi->channel[0];
}

/* An initialized channel has a non-null GSI pointer */
static bool gsi_channel_initialized(struct gsi_channel *channel)
{
        return !!channel->gsi;
}

/* Update the GSI IRQ type register with the cached value */
static void gsi_irq_type_update(struct gsi *gsi, u32 val)
{
        gsi->type_enabled_bitmap = val;
        iowrite32(val, gsi->virt + GSI_CNTXT_TYPE_IRQ_MSK_OFFSET);
}

static void gsi_irq_type_enable(struct gsi *gsi, enum gsi_irq_type_id type_id)
{
        gsi_irq_type_update(gsi, gsi->type_enabled_bitmap | BIT(type_id));
}

static void gsi_irq_type_disable(struct gsi *gsi, enum gsi_irq_type_id type_id)
{
        gsi_irq_type_update(gsi, gsi->type_enabled_bitmap & ~BIT(type_id));
}

/* Event ring commands are performed one at a time.  Their completion
 * is signaled by the event ring control GSI interrupt type, which is
 * only enabled when we issue an event ring command.  Only the event
 * ring being operated on has this interrupt enabled.
 */
static void gsi_irq_ev_ctrl_enable(struct gsi *gsi, u32 evt_ring_id)
{
        u32 val = BIT(evt_ring_id);

        /* There's a small chance that a previous command completed
         * after the interrupt was disabled, so make sure we have no
         * pending interrupts before we enable them.
         */
        iowrite32(~0, gsi->virt + GSI_CNTXT_SRC_EV_CH_IRQ_CLR_OFFSET);

        iowrite32(val, gsi->virt + GSI_CNTXT_SRC_EV_CH_IRQ_MSK_OFFSET);
        gsi_irq_type_enable(gsi, GSI_EV_CTRL);
}

/* Disable event ring control interrupts */
static void gsi_irq_ev_ctrl_disable(struct gsi *gsi)
{
        gsi_irq_type_disable(gsi, GSI_EV_CTRL);
        iowrite32(0, gsi->virt + GSI_CNTXT_SRC_EV_CH_IRQ_MSK_OFFSET);
}

/* Channel commands are performed one at a time.  Their completion is
 * signaled by the channel control GSI interrupt type, which is only
 * enabled when we issue a channel command.  Only the channel being
 * operated on has this interrupt enabled.
 */
static void gsi_irq_ch_ctrl_enable(struct gsi *gsi, u32 channel_id)
{
        u32 val = BIT(channel_id);

        /* There's a small chance that a previous command completed
         * after the interrupt was disabled, so make sure we have no
         * pending interrupts before we enable them.
         */
        iowrite32(~0, gsi->virt + GSI_CNTXT_SRC_CH_IRQ_CLR_OFFSET);

        iowrite32(val, gsi->virt + GSI_CNTXT_SRC_CH_IRQ_MSK_OFFSET);
        gsi_irq_type_enable(gsi, GSI_CH_CTRL);
}

/* Disable channel control interrupts */
static void gsi_irq_ch_ctrl_disable(struct gsi *gsi)
{
        gsi_irq_type_disable(gsi, GSI_CH_CTRL);
        iowrite32(0, gsi->virt + GSI_CNTXT_SRC_CH_IRQ_MSK_OFFSET);
}

static void gsi_irq_ieob_enable_one(struct gsi *gsi, u32 evt_ring_id)
{
        bool enable_ieob = !gsi->ieob_enabled_bitmap;
        u32 val;

        gsi->ieob_enabled_bitmap |= BIT(evt_ring_id);
        val = gsi->ieob_enabled_bitmap;
        iowrite32(val, gsi->virt + GSI_CNTXT_SRC_IEOB_IRQ_MSK_OFFSET);

        /* Enable the interrupt type if this is the first channel enabled */
        if (enable_ieob)
                gsi_irq_type_enable(gsi, GSI_IEOB);
}

static void gsi_irq_ieob_disable(struct gsi *gsi, u32 event_mask)
{
        u32 val;

        gsi->ieob_enabled_bitmap &= ~event_mask;

        /* Disable the interrupt type if this was the last enabled channel */
        if (!gsi->ieob_enabled_bitmap)
                gsi_irq_type_disable(gsi, GSI_IEOB);

        val = gsi->ieob_enabled_bitmap;
        iowrite32(val, gsi->virt + GSI_CNTXT_SRC_IEOB_IRQ_MSK_OFFSET);
}

static void gsi_irq_ieob_disable_one(struct gsi *gsi, u32 evt_ring_id)
{
        gsi_irq_ieob_disable(gsi, BIT(evt_ring_id));
}

/* Enable all GSI_interrupt types */
static void gsi_irq_enable(struct gsi *gsi)
{
        u32 val;

        /* Global interrupts include hardware error reports.  Enable
         * that so we can at least report the error should it occur.
         */
        iowrite32(BIT(ERROR_INT), gsi->virt + GSI_CNTXT_GLOB_IRQ_EN_OFFSET);
        gsi_irq_type_update(gsi, gsi->type_enabled_bitmap | BIT(GSI_GLOB_EE));

        /* General GSI interrupts are reported to all EEs; if they occur
         * they are unrecoverable (without reset).  A breakpoint interrupt
         * also exists, but we don't support that.  We want to be notified
         * of errors so we can report them, even if they can't be handled.
         */
        val = BIT(BUS_ERROR);
        val |= BIT(CMD_FIFO_OVRFLOW);
        val |= BIT(MCS_STACK_OVRFLOW);
        iowrite32(val, gsi->virt + GSI_CNTXT_GSI_IRQ_EN_OFFSET);
        gsi_irq_type_update(gsi, gsi->type_enabled_bitmap | BIT(GSI_GENERAL));
}

/* Disable all GSI interrupt types */
static void gsi_irq_disable(struct gsi *gsi)
{
        gsi_irq_type_update(gsi, 0);

        /* Clear the type-specific interrupt masks set by gsi_irq_enable() */
        iowrite32(0, gsi->virt + GSI_CNTXT_GSI_IRQ_EN_OFFSET);
        iowrite32(0, gsi->virt + GSI_CNTXT_GLOB_IRQ_EN_OFFSET);
}

/* Return the virtual address associated with a ring index */
void *gsi_ring_virt(struct gsi_ring *ring, u32 index)
{
        /* Note: index *must* be used modulo the ring count here */
        return ring->virt + (index % ring->count) * GSI_RING_ELEMENT_SIZE;
}

/* Return the 32-bit DMA address associated with a ring index */
static u32 gsi_ring_addr(struct gsi_ring *ring, u32 index)
{
        return lower_32_bits(ring->addr) + index * GSI_RING_ELEMENT_SIZE;
}

/* Return the ring index of a 32-bit ring offset */
static u32 gsi_ring_index(struct gsi_ring *ring, u32 offset)
{
        return (offset - gsi_ring_addr(ring, 0)) / GSI_RING_ELEMENT_SIZE;
}

/* Issue a GSI command by writing a value to a register, then wait for
 * completion to be signaled.  Returns true if the command completes
 * or false if it times out.
 */
static bool
gsi_command(struct gsi *gsi, u32 reg, u32 val, struct completion *completion)
{
        unsigned long timeout = msecs_to_jiffies(GSI_CMD_TIMEOUT);

        reinit_completion(completion);

        iowrite32(val, gsi->virt + reg);

        return !!wait_for_completion_timeout(completion, timeout);
}

/* Return the hardware's notion of the current state of an event ring */
static enum gsi_evt_ring_state
gsi_evt_ring_state(struct gsi *gsi, u32 evt_ring_id)
{
        u32 val;

        val = ioread32(gsi->virt + GSI_EV_CH_E_CNTXT_0_OFFSET(evt_ring_id));

        return u32_get_bits(val, EV_CHSTATE_FMASK);
}

/* Issue an event ring command and wait for it to complete */
static void gsi_evt_ring_command(struct gsi *gsi, u32 evt_ring_id,
                                 enum gsi_evt_cmd_opcode opcode)
{
        struct gsi_evt_ring *evt_ring = &gsi->evt_ring[evt_ring_id];
        struct completion *completion = &evt_ring->completion;
        struct device *dev = gsi->dev;
        bool timeout;
        u32 val;

        /* Enable the completion interrupt for the command */
        gsi_irq_ev_ctrl_enable(gsi, evt_ring_id);

        val = u32_encode_bits(evt_ring_id, EV_CHID_FMASK);
        val |= u32_encode_bits(opcode, EV_OPCODE_FMASK);

        timeout = !gsi_command(gsi, GSI_EV_CH_CMD_OFFSET, val, completion);

        gsi_irq_ev_ctrl_disable(gsi);

        if (!timeout)
                return;

        dev_err(dev, "GSI command %u for event ring %u timed out, state %u\n",
                opcode, evt_ring_id, gsi_evt_ring_state(gsi, evt_ring_id));
}

/* Allocate an event ring in NOT_ALLOCATED state */
static int gsi_evt_ring_alloc_command(struct gsi *gsi, u32 evt_ring_id)
{
        enum gsi_evt_ring_state state;

        /* Get initial event ring state */
        state = gsi_evt_ring_state(gsi, evt_ring_id);
        if (state != GSI_EVT_RING_STATE_NOT_ALLOCATED) {
                dev_err(gsi->dev, "event ring %u bad state %u before alloc\n",
                        evt_ring_id, state);
                return -EINVAL;
        }

        gsi_evt_ring_command(gsi, evt_ring_id, GSI_EVT_ALLOCATE);

        /* If successful the event ring state will have changed */
        state = gsi_evt_ring_state(gsi, evt_ring_id);
        if (state == GSI_EVT_RING_STATE_ALLOCATED)
                return 0;

        dev_err(gsi->dev, "event ring %u bad state %u after alloc\n",
                evt_ring_id, state);

        return -EIO;
}

/* Reset a GSI event ring in ALLOCATED or ERROR state. */
static void gsi_evt_ring_reset_command(struct gsi *gsi, u32 evt_ring_id)
{
        enum gsi_evt_ring_state state;

        state = gsi_evt_ring_state(gsi, evt_ring_id);
        if (state != GSI_EVT_RING_STATE_ALLOCATED &&
            state != GSI_EVT_RING_STATE_ERROR) {
                dev_err(gsi->dev, "event ring %u bad state %u before reset\n",
                        evt_ring_id, state);
                return;
        }

        gsi_evt_ring_command(gsi, evt_ring_id, GSI_EVT_RESET);

        /* If successful the event ring state will have changed */
        state = gsi_evt_ring_state(gsi, evt_ring_id);
        if (state == GSI_EVT_RING_STATE_ALLOCATED)
                return;

        dev_err(gsi->dev, "event ring %u bad state %u after reset\n",
                evt_ring_id, state);
}

/* Issue a hardware de-allocation request for an allocated event ring */
static void gsi_evt_ring_de_alloc_command(struct gsi *gsi, u32 evt_ring_id)
{
        enum gsi_evt_ring_state state;

        state = gsi_evt_ring_state(gsi, evt_ring_id);
        if (state != GSI_EVT_RING_STATE_ALLOCATED) {
                dev_err(gsi->dev, "event ring %u state %u before dealloc\n",
                        evt_ring_id, state);
                return;
        }

        gsi_evt_ring_command(gsi, evt_ring_id, GSI_EVT_DE_ALLOC);

        /* If successful the event ring state will have changed */
        state = gsi_evt_ring_state(gsi, evt_ring_id);
        if (state == GSI_EVT_RING_STATE_NOT_ALLOCATED)
                return;

        dev_err(gsi->dev, "event ring %u bad state %u after dealloc\n",
                evt_ring_id, state);
}

/* Fetch the current state of a channel from hardware */
static enum gsi_channel_state gsi_channel_state(struct gsi_channel *channel)
{
        u32 channel_id = gsi_channel_id(channel);
        void __iomem *virt = channel->gsi->virt;
        u32 val;

        val = ioread32(virt + GSI_CH_C_CNTXT_0_OFFSET(channel_id));

        return u32_get_bits(val, CHSTATE_FMASK);
}

/* Issue a channel command and wait for it to complete */
static void
gsi_channel_command(struct gsi_channel *channel, enum gsi_ch_cmd_opcode opcode)
{
        struct completion *completion = &channel->completion;
        u32 channel_id = gsi_channel_id(channel);
        struct gsi *gsi = channel->gsi;
        struct device *dev = gsi->dev;
        bool timeout;
        u32 val;

        /* Enable the completion interrupt for the command */
        gsi_irq_ch_ctrl_enable(gsi, channel_id);

        val = u32_encode_bits(channel_id, CH_CHID_FMASK);
        val |= u32_encode_bits(opcode, CH_OPCODE_FMASK);
        timeout = !gsi_command(gsi, GSI_CH_CMD_OFFSET, val, completion);

        gsi_irq_ch_ctrl_disable(gsi);

        if (!timeout)
                return;

        dev_err(dev, "GSI command %u for channel %u timed out, state %u\n",
                opcode, channel_id, gsi_channel_state(channel));
}

/* Allocate GSI channel in NOT_ALLOCATED state */
static int gsi_channel_alloc_command(struct gsi *gsi, u32 channel_id)
{
        struct gsi_channel *channel = &gsi->channel[channel_id];
        struct device *dev = gsi->dev;
        enum gsi_channel_state state;

        /* Get initial channel state */
        state = gsi_channel_state(channel);
        if (state != GSI_CHANNEL_STATE_NOT_ALLOCATED) {
                dev_err(dev, "channel %u bad state %u before alloc\n",
                        channel_id, state);
                return -EINVAL;
        }

        gsi_channel_command(channel, GSI_CH_ALLOCATE);

        /* If successful the channel state will have changed */
        state = gsi_channel_state(channel);
        if (state == GSI_CHANNEL_STATE_ALLOCATED)
                return 0;

        dev_err(dev, "channel %u bad state %u after alloc\n",
                channel_id, state);

        return -EIO;
}

/* Start an ALLOCATED channel */
static int gsi_channel_start_command(struct gsi_channel *channel)
{
        struct device *dev = channel->gsi->dev;
        enum gsi_channel_state state;

        state = gsi_channel_state(channel);
        if (state != GSI_CHANNEL_STATE_ALLOCATED &&
            state != GSI_CHANNEL_STATE_STOPPED) {
                dev_err(dev, "channel %u bad state %u before start\n",
                        gsi_channel_id(channel), state);
                return -EINVAL;
        }

        gsi_channel_command(channel, GSI_CH_START);

        /* If successful the channel state will have changed */
        state = gsi_channel_state(channel);
        if (state == GSI_CHANNEL_STATE_STARTED)
                return 0;

        dev_err(dev, "channel %u bad state %u after start\n",
                gsi_channel_id(channel), state);

        return -EIO;
}

/* Stop a GSI channel in STARTED state */
static int gsi_channel_stop_command(struct gsi_channel *channel)
{
        struct device *dev = channel->gsi->dev;
        enum gsi_channel_state state;

        state = gsi_channel_state(channel);

        /* Channel could have entered STOPPED state since last call
         * if it timed out.  If so, we're done.
         */
        if (state == GSI_CHANNEL_STATE_STOPPED)
                return 0;

        if (state != GSI_CHANNEL_STATE_STARTED &&
            state != GSI_CHANNEL_STATE_STOP_IN_PROC) {
                dev_err(dev, "channel %u bad state %u before stop\n",
                        gsi_channel_id(channel), state);
                return -EINVAL;
        }

        gsi_channel_command(channel, GSI_CH_STOP);

        /* If successful the channel state will have changed */
        state = gsi_channel_state(channel);
        if (state == GSI_CHANNEL_STATE_STOPPED)
                return 0;

        /* We may have to try again if stop is in progress */
        if (state == GSI_CHANNEL_STATE_STOP_IN_PROC)
                return -EAGAIN;

        dev_err(dev, "channel %u bad state %u after stop\n",
                gsi_channel_id(channel), state);

        return -EIO;
}

/* Reset a GSI channel in ALLOCATED or ERROR state. */
static void gsi_channel_reset_command(struct gsi_channel *channel)
{
        struct device *dev = channel->gsi->dev;
        enum gsi_channel_state state;

        /* A short delay is required before a RESET command */
        usleep_range(USEC_PER_MSEC, 2 * USEC_PER_MSEC);

        state = gsi_channel_state(channel);
        if (state != GSI_CHANNEL_STATE_STOPPED &&
            state != GSI_CHANNEL_STATE_ERROR) {
                /* No need to reset a channel already in ALLOCATED state */
                if (state != GSI_CHANNEL_STATE_ALLOCATED)
                        dev_err(dev, "channel %u bad state %u before reset\n",
                                gsi_channel_id(channel), state);
                return;
        }

        gsi_channel_command(channel, GSI_CH_RESET);

        /* If successful the channel state will have changed */
        state = gsi_channel_state(channel);
        if (state != GSI_CHANNEL_STATE_ALLOCATED)
                dev_err(dev, "channel %u bad state %u after reset\n",
                        gsi_channel_id(channel), state);
}

/* Deallocate an ALLOCATED GSI channel */
static void gsi_channel_de_alloc_command(struct gsi *gsi, u32 channel_id)
{
        struct gsi_channel *channel = &gsi->channel[channel_id];
        struct device *dev = gsi->dev;
        enum gsi_channel_state state;

        state = gsi_channel_state(channel);
        if (state != GSI_CHANNEL_STATE_ALLOCATED) {
                dev_err(dev, "channel %u bad state %u before dealloc\n",
                        channel_id, state);
                return;
        }

        gsi_channel_command(channel, GSI_CH_DE_ALLOC);

        /* If successful the channel state will have changed */
        state = gsi_channel_state(channel);

        if (state != GSI_CHANNEL_STATE_NOT_ALLOCATED)
                dev_err(dev, "channel %u bad state %u after dealloc\n",
                        channel_id, state);
}

/* Ring an event ring doorbell, reporting the last entry processed by the AP.
 * The index argument (modulo the ring count) is the first unfilled entry, so
 * we supply one less than that with the doorbell.  Update the event ring
 * index field with the value provided.
 */
static void gsi_evt_ring_doorbell(struct gsi *gsi, u32 evt_ring_id, u32 index)
{
        struct gsi_ring *ring = &gsi->evt_ring[evt_ring_id].ring;
        u32 val;

        ring->index = index;    /* Next unused entry */

        /* Note: index *must* be used modulo the ring count here */
        val = gsi_ring_addr(ring, (index - 1) % ring->count);
        iowrite32(val, gsi->virt + GSI_EV_CH_E_DOORBELL_0_OFFSET(evt_ring_id));
}

/* Program an event ring for use */
static void gsi_evt_ring_program(struct gsi *gsi, u32 evt_ring_id)
{
        struct gsi_evt_ring *evt_ring = &gsi->evt_ring[evt_ring_id];
        size_t size = evt_ring->ring.count * GSI_RING_ELEMENT_SIZE;
        u32 val;

        /* We program all event rings as GPI type/protocol */
        val = u32_encode_bits(GSI_CHANNEL_TYPE_GPI, EV_CHTYPE_FMASK);
        val |= EV_INTYPE_FMASK;
        val |= u32_encode_bits(GSI_RING_ELEMENT_SIZE, EV_ELEMENT_SIZE_FMASK);
        iowrite32(val, gsi->virt + GSI_EV_CH_E_CNTXT_0_OFFSET(evt_ring_id));

        val = ev_r_length_encoded(gsi->version, size);
        iowrite32(val, gsi->virt + GSI_EV_CH_E_CNTXT_1_OFFSET(evt_ring_id));

        /* The context 2 and 3 registers store the low-order and
         * high-order 32 bits of the address of the event ring,
         * respectively.
         */
        val = lower_32_bits(evt_ring->ring.addr);
        iowrite32(val, gsi->virt + GSI_EV_CH_E_CNTXT_2_OFFSET(evt_ring_id));
        val = upper_32_bits(evt_ring->ring.addr);
        iowrite32(val, gsi->virt + GSI_EV_CH_E_CNTXT_3_OFFSET(evt_ring_id));

        /* Enable interrupt moderation by setting the moderation delay */
        val = u32_encode_bits(GSI_EVT_RING_INT_MODT, MODT_FMASK);
        val |= u32_encode_bits(1, MODC_FMASK);  /* comes from channel */
        iowrite32(val, gsi->virt + GSI_EV_CH_E_CNTXT_8_OFFSET(evt_ring_id));

        /* No MSI write data, and MSI address high and low address is 0 */
        iowrite32(0, gsi->virt + GSI_EV_CH_E_CNTXT_9_OFFSET(evt_ring_id));
        iowrite32(0, gsi->virt + GSI_EV_CH_E_CNTXT_10_OFFSET(evt_ring_id));
        iowrite32(0, gsi->virt + GSI_EV_CH_E_CNTXT_11_OFFSET(evt_ring_id));

        /* We don't need to get event read pointer updates */
        iowrite32(0, gsi->virt + GSI_EV_CH_E_CNTXT_12_OFFSET(evt_ring_id));
        iowrite32(0, gsi->virt + GSI_EV_CH_E_CNTXT_13_OFFSET(evt_ring_id));

        /* Finally, tell the hardware we've completed event 0 (arbitrary) */
        gsi_evt_ring_doorbell(gsi, evt_ring_id, 0);
}

/* Find the transaction whose completion indicates a channel is quiesced */
static struct gsi_trans *gsi_channel_trans_last(struct gsi_channel *channel)
{
        struct gsi_trans_info *trans_info = &channel->trans_info;
        const struct list_head *list;
        struct gsi_trans *trans;

        spin_lock_bh(&trans_info->spinlock);

        /* There is a small chance a TX transaction got allocated just
         * before we disabled transmits, so check for that.
         */
        if (channel->toward_ipa) {
                list = &trans_info->alloc;
                if (!list_empty(list))
                        goto done;
                list = &trans_info->pending;
                if (!list_empty(list))
                        goto done;
        }

        /* Otherwise (TX or RX) we want to wait for anything that
         * has completed, or has been polled but not released yet.
         */
        list = &trans_info->complete;
        if (!list_empty(list))
                goto done;
        list = &trans_info->polled;
        if (list_empty(list))
                list = NULL;
done:
        trans = list ? list_last_entry(list, struct gsi_trans, links) : NULL;

        /* Caller will wait for this, so take a reference */
        if (trans)
                refcount_inc(&trans->refcount);

        spin_unlock_bh(&trans_info->spinlock);

        return trans;
}

/* Wait for transaction activity on a channel to complete */
static void gsi_channel_trans_quiesce(struct gsi_channel *channel)
{
        struct gsi_trans *trans;

        /* Get the last transaction, and wait for it to complete */
        trans = gsi_channel_trans_last(channel);
        if (trans) {
                wait_for_completion(&trans->completion);
                gsi_trans_free(trans);
        }
}

/* Program a channel for use; there is no gsi_channel_deprogram() */
static void gsi_channel_program(struct gsi_channel *channel, bool doorbell)
{
        size_t size = channel->tre_ring.count * GSI_RING_ELEMENT_SIZE;
        u32 channel_id = gsi_channel_id(channel);
        union gsi_channel_scratch scr = { };
        struct gsi_channel_scratch_gpi *gpi;
        struct gsi *gsi = channel->gsi;
        u32 wrr_weight = 0;
        u32 val;

        /* Arbitrarily pick TRE 0 as the first channel element to use */
        channel->tre_ring.index = 0;

        /* We program all channels as GPI type/protocol */
        val = chtype_protocol_encoded(gsi->version, GSI_CHANNEL_TYPE_GPI);
        if (channel->toward_ipa)
                val |= CHTYPE_DIR_FMASK;
        val |= u32_encode_bits(channel->evt_ring_id, ERINDEX_FMASK);
        val |= u32_encode_bits(GSI_RING_ELEMENT_SIZE, ELEMENT_SIZE_FMASK);
        iowrite32(val, gsi->virt + GSI_CH_C_CNTXT_0_OFFSET(channel_id));

        val = r_length_encoded(gsi->version, size);
        iowrite32(val, gsi->virt + GSI_CH_C_CNTXT_1_OFFSET(channel_id));

        /* The context 2 and 3 registers store the low-order and
         * high-order 32 bits of the address of the channel ring,
         * respectively.
         */
        val = lower_32_bits(channel->tre_ring.addr);
        iowrite32(val, gsi->virt + GSI_CH_C_CNTXT_2_OFFSET(channel_id));
        val = upper_32_bits(channel->tre_ring.addr);
        iowrite32(val, gsi->virt + GSI_CH_C_CNTXT_3_OFFSET(channel_id));

        /* Command channel gets low weighted round-robin priority */
        if (channel->command)
                wrr_weight = field_max(WRR_WEIGHT_FMASK);
        val = u32_encode_bits(wrr_weight, WRR_WEIGHT_FMASK);

        /* Max prefetch is 1 segment (do not set MAX_PREFETCH_FMASK) */

        /* No need to use the doorbell engine starting at IPA v4.0 */
        if (gsi->version < IPA_VERSION_4_0 && doorbell)
                val |= USE_DB_ENG_FMASK;

        /* v4.0 introduces an escape buffer for prefetch.  We use it
         * on all but the AP command channel.
         */
        if (gsi->version >= IPA_VERSION_4_0 && !channel->command) {
                /* If not otherwise set, prefetch buffers are used */
                if (gsi->version < IPA_VERSION_4_5)
                        val |= USE_ESCAPE_BUF_ONLY_FMASK;
                else
                        val |= u32_encode_bits(GSI_ESCAPE_BUF_ONLY,
                                               PREFETCH_MODE_FMASK);
        }
        /* All channels set DB_IN_BYTES */
        if (gsi->version >= IPA_VERSION_4_9)
                val |= DB_IN_BYTES;

        iowrite32(val, gsi->virt + GSI_CH_C_QOS_OFFSET(channel_id));

        /* Now update the scratch registers for GPI protocol */
        gpi = &scr.gpi;
        gpi->max_outstanding_tre = gsi_channel_trans_tre_max(gsi, channel_id) *
                                        GSI_RING_ELEMENT_SIZE;
        gpi->outstanding_threshold = 2 * GSI_RING_ELEMENT_SIZE;

        val = scr.data.word1;
        iowrite32(val, gsi->virt + GSI_CH_C_SCRATCH_0_OFFSET(channel_id));

        val = scr.data.word2;
        iowrite32(val, gsi->virt + GSI_CH_C_SCRATCH_1_OFFSET(channel_id));

        val = scr.data.word3;
        iowrite32(val, gsi->virt + GSI_CH_C_SCRATCH_2_OFFSET(channel_id));

        /* We must preserve the upper 16 bits of the last scratch register.
         * The next sequence assumes those bits remain unchanged between the
         * read and the write.
         */
        val = ioread32(gsi->virt + GSI_CH_C_SCRATCH_3_OFFSET(channel_id));
        val = (scr.data.word4 & GENMASK(31, 16)) | (val & GENMASK(15, 0));
        iowrite32(val, gsi->virt + GSI_CH_C_SCRATCH_3_OFFSET(channel_id));

        /* All done! */
}

static int __gsi_channel_start(struct gsi_channel *channel, bool resume)
{
        struct gsi *gsi = channel->gsi;
        int ret;

        /* Prior to IPA v4.0 suspend/resume is not implemented by GSI */
        if (resume && gsi->version < IPA_VERSION_4_0)
                return 0;

        mutex_lock(&gsi->mutex);

        ret = gsi_channel_start_command(channel);

        mutex_unlock(&gsi->mutex);

        return ret;
}

/* Start an allocated GSI channel */
int gsi_channel_start(struct gsi *gsi, u32 channel_id)
{
        struct gsi_channel *channel = &gsi->channel[channel_id];
        int ret;

        /* Enable NAPI and the completion interrupt */
        napi_enable(&channel->napi);
        gsi_irq_ieob_enable_one(gsi, channel->evt_ring_id);

        ret = __gsi_channel_start(channel, false);
        if (ret) {
                gsi_irq_ieob_disable_one(gsi, channel->evt_ring_id);
                napi_disable(&channel->napi);
        }

        return ret;
}

static int gsi_channel_stop_retry(struct gsi_channel *channel)
{
        u32 retries = GSI_CHANNEL_STOP_RETRIES;
        int ret;

        do {
                ret = gsi_channel_stop_command(channel);
                if (ret != -EAGAIN)
                        break;
                usleep_range(3 * USEC_PER_MSEC, 5 * USEC_PER_MSEC);
        } while (retries--);

        return ret;
}

static int __gsi_channel_stop(struct gsi_channel *channel, bool suspend)
{
        struct gsi *gsi = channel->gsi;
        int ret;

        /* Wait for any underway transactions to complete before stopping. */
        gsi_channel_trans_quiesce(channel);

        /* Prior to IPA v4.0 suspend/resume is not implemented by GSI */
        if (suspend && gsi->version < IPA_VERSION_4_0)
                return 0;

        mutex_lock(&gsi->mutex);

        ret = gsi_channel_stop_retry(channel);

        mutex_unlock(&gsi->mutex);

        return ret;
}

/* Stop a started channel */
int gsi_channel_stop(struct gsi *gsi, u32 channel_id)
{
        struct gsi_channel *channel = &gsi->channel[channel_id];
        int ret;

        ret = __gsi_channel_stop(channel, false);
        if (ret)
                return ret;

        /* Disable the completion interrupt and NAPI if successful */
        gsi_irq_ieob_disable_one(gsi, channel->evt_ring_id);
        napi_disable(&channel->napi);

        return 0;
}

/* Reset and reconfigure a channel, (possibly) enabling the doorbell engine */
void gsi_channel_reset(struct gsi *gsi, u32 channel_id, bool doorbell)
{
        struct gsi_channel *channel = &gsi->channel[channel_id];

        mutex_lock(&gsi->mutex);

        gsi_channel_reset_command(channel);
        /* Due to a hardware quirk we may need to reset RX channels twice. */
        if (gsi->version < IPA_VERSION_4_0 && !channel->toward_ipa)
                gsi_channel_reset_command(channel);

        gsi_channel_program(channel, doorbell);
        gsi_channel_trans_cancel_pending(channel);

        mutex_unlock(&gsi->mutex);
}

/* Stop a started channel for suspend */
int gsi_channel_suspend(struct gsi *gsi, u32 channel_id)
{
        struct gsi_channel *channel = &gsi->channel[channel_id];
        int ret;

        ret = __gsi_channel_stop(channel, true);
        if (ret)
                return ret;

        /* Ensure NAPI polling has finished. */
        napi_synchronize(&channel->napi);

        return 0;
}

/* Resume a suspended channel (starting if stopped) */
int gsi_channel_resume(struct gsi *gsi, u32 channel_id)
{
        struct gsi_channel *channel = &gsi->channel[channel_id];

        return __gsi_channel_start(channel, true);
}

/* Prevent all GSI interrupts while suspended */
void gsi_suspend(struct gsi *gsi)
{
        disable_irq(gsi->irq);
}

/* Allow all GSI interrupts again when resuming */
void gsi_resume(struct gsi *gsi)
{
        enable_irq(gsi->irq);
}

/**
 * gsi_channel_tx_queued() - Report queued TX transfers for a channel
 * @channel:    Channel for which to report
 *
 * Report to the network stack the number of bytes and transactions that
 * have been queued to hardware since last call.  This and the next function
 * supply information used by the network stack for throttling.
 *
 * For each channel we track the number of transactions used and bytes of
 * data those transactions represent.  We also track what those values are
 * each time this function is called.  Subtracting the two tells us
 * the number of bytes and transactions that have been added between
 * successive calls.
 *
 * Calling this each time we ring the channel doorbell allows us to
 * provide accurate information to the network stack about how much
 * work we've given the hardware at any point in time.
 */
void gsi_channel_tx_queued(struct gsi_channel *channel)
{
        u32 trans_count;
        u32 byte_count;

        byte_count = channel->byte_count - channel->queued_byte_count;
        trans_count = channel->trans_count - channel->queued_trans_count;
        channel->queued_byte_count = channel->byte_count;
        channel->queued_trans_count = channel->trans_count;

        ipa_gsi_channel_tx_queued(channel->gsi, gsi_channel_id(channel),
                                  trans_count, byte_count);
}

/**
 * gsi_channel_tx_update() - Report completed TX transfers
 * @channel:    Channel that has completed transmitting packets
 * @trans:      Last transation known to be complete
 *
 * Compute the number of transactions and bytes that have been transferred
 * over a TX channel since the given transaction was committed.  Report this
 * information to the network stack.
 *
 * At the time a transaction is committed, we record its channel's
 * committed transaction and byte counts *in the transaction*.
 * Completions are signaled by the hardware with an interrupt, and
 * we can determine the latest completed transaction at that time.
 *
 * The difference between the byte/transaction count recorded in
 * the transaction and the count last time we recorded a completion
 * tells us exactly how much data has been transferred between
 * completions.
 *
 * Calling this each time we learn of a newly-completed transaction
 * allows us to provide accurate information to the network stack
 * about how much work has been completed by the hardware at a given
 * point in time.
 */
static void
gsi_channel_tx_update(struct gsi_channel *channel, struct gsi_trans *trans)
{
        u64 byte_count = trans->byte_count + trans->len;
        u64 trans_count = trans->trans_count + 1;

        byte_count -= channel->compl_byte_count;
        channel->compl_byte_count += byte_count;
        trans_count -= channel->compl_trans_count;
        channel->compl_trans_count += trans_count;

        ipa_gsi_channel_tx_completed(channel->gsi, gsi_channel_id(channel),
                                     trans_count, byte_count);
}

/* Channel control interrupt handler */
static void gsi_isr_chan_ctrl(struct gsi *gsi)
{
        u32 channel_mask;

        channel_mask = ioread32(gsi->virt + GSI_CNTXT_SRC_CH_IRQ_OFFSET);
        iowrite32(channel_mask, gsi->virt + GSI_CNTXT_SRC_CH_IRQ_CLR_OFFSET);

        while (channel_mask) {
                u32 channel_id = __ffs(channel_mask);
                struct gsi_channel *channel;

                channel_mask ^= BIT(channel_id);

                channel = &gsi->channel[channel_id];

                complete(&channel->completion);
        }
}

/* Event ring control interrupt handler */
static void gsi_isr_evt_ctrl(struct gsi *gsi)
{
        u32 event_mask;

        event_mask = ioread32(gsi->virt + GSI_CNTXT_SRC_EV_CH_IRQ_OFFSET);
        iowrite32(event_mask, gsi->virt + GSI_CNTXT_SRC_EV_CH_IRQ_CLR_OFFSET);

        while (event_mask) {
                u32 evt_ring_id = __ffs(event_mask);
                struct gsi_evt_ring *evt_ring;

                event_mask ^= BIT(evt_ring_id);

                evt_ring = &gsi->evt_ring[evt_ring_id];

                complete(&evt_ring->completion);
        }
}

/* Global channel error interrupt handler */
static void
gsi_isr_glob_chan_err(struct gsi *gsi, u32 err_ee, u32 channel_id, u32 code)
{
        if (code == GSI_OUT_OF_RESOURCES) {
                dev_err(gsi->dev, "channel %u out of resources\n", channel_id);
                complete(&gsi->channel[channel_id].completion);
                return;
        }

        /* Report, but otherwise ignore all other error codes */
        dev_err(gsi->dev, "channel %u global error ee 0x%08x code 0x%08x\n",
                channel_id, err_ee, code);
}

/* Global event error interrupt handler */
static void
gsi_isr_glob_evt_err(struct gsi *gsi, u32 err_ee, u32 evt_ring_id, u32 code)
{
        if (code == GSI_OUT_OF_RESOURCES) {
                struct gsi_evt_ring *evt_ring = &gsi->evt_ring[evt_ring_id];
                u32 channel_id = gsi_channel_id(evt_ring->channel);

                complete(&evt_ring->completion);
                dev_err(gsi->dev, "evt_ring for channel %u out of resources\n",
                        channel_id);
                return;
        }

        /* Report, but otherwise ignore all other error codes */
        dev_err(gsi->dev, "event ring %u global error ee %u code 0x%08x\n",
                evt_ring_id, err_ee, code);
}

/* Global error interrupt handler */
static void gsi_isr_glob_err(struct gsi *gsi)
{
        enum gsi_err_type type;
        enum gsi_err_code code;
        u32 which;
        u32 val;
        u32 ee;

        /* Get the logged error, then reinitialize the log */
        val = ioread32(gsi->virt + GSI_ERROR_LOG_OFFSET);
        iowrite32(0, gsi->virt + GSI_ERROR_LOG_OFFSET);
        iowrite32(~0, gsi->virt + GSI_ERROR_LOG_CLR_OFFSET);

        ee = u32_get_bits(val, ERR_EE_FMASK);
        type = u32_get_bits(val, ERR_TYPE_FMASK);
        which = u32_get_bits(val, ERR_VIRT_IDX_FMASK);
        code = u32_get_bits(val, ERR_CODE_FMASK);

        if (type == GSI_ERR_TYPE_CHAN)
                gsi_isr_glob_chan_err(gsi, ee, which, code);
        else if (type == GSI_ERR_TYPE_EVT)
                gsi_isr_glob_evt_err(gsi, ee, which, code);
        else    /* type GSI_ERR_TYPE_GLOB should be fatal */
                dev_err(gsi->dev, "unexpected global error 0x%08x\n", type);
}

/* Generic EE interrupt handler */
static void gsi_isr_gp_int1(struct gsi *gsi)
{
        u32 result;
        u32 val;

        /* This interrupt is used to handle completions of the two GENERIC
         * GSI commands.  We use these to allocate and halt channels on
         * the modem's behalf due to a hardware quirk on IPA v4.2.  Once
         * allocated, the modem "owns" these channels, and as a result we
         * have no way of knowing the channel's state at any given time.
         *
         * It is recommended that we halt the modem channels we allocated
         * when shutting down, but it's possible the channel isn't running
         * at the time we issue the HALT command.  We'll get an error in
         * that case, but it's harmless (the channel is already halted).
         *
         * For this reason, we silently ignore a CHANNEL_NOT_RUNNING error
         * if we receive it.
         */
        val = ioread32(gsi->virt + GSI_CNTXT_SCRATCH_0_OFFSET);
        result = u32_get_bits(val, GENERIC_EE_RESULT_FMASK);

        switch (result) {
        case GENERIC_EE_SUCCESS:
        case GENERIC_EE_CHANNEL_NOT_RUNNING:
                gsi->result = 0;
                break;

        case GENERIC_EE_RETRY:
                gsi->result = -EAGAIN;
                break;

        default:
                dev_err(gsi->dev, "global INT1 generic result %u\n", result);
                gsi->result = -EIO;
                break;
        }

        complete(&gsi->completion);
}

/* Inter-EE interrupt handler */
static void gsi_isr_glob_ee(struct gsi *gsi)
{
        u32 val;

        val = ioread32(gsi->virt + GSI_CNTXT_GLOB_IRQ_STTS_OFFSET);

        if (val & BIT(ERROR_INT))
                gsi_isr_glob_err(gsi);

        iowrite32(val, gsi->virt + GSI_CNTXT_GLOB_IRQ_CLR_OFFSET);

        val &= ~BIT(ERROR_INT);

        if (val & BIT(GP_INT1)) {
                val ^= BIT(GP_INT1);
                gsi_isr_gp_int1(gsi);
        }

        if (val)
                dev_err(gsi->dev, "unexpected global interrupt 0x%08x\n", val);
}

/* I/O completion interrupt event */
static void gsi_isr_ieob(struct gsi *gsi)
{
        u32 event_mask;

        event_mask = ioread32(gsi->virt + GSI_CNTXT_SRC_IEOB_IRQ_OFFSET);
        gsi_irq_ieob_disable(gsi, event_mask);
        iowrite32(event_mask, gsi->virt + GSI_CNTXT_SRC_IEOB_IRQ_CLR_OFFSET);

        while (event_mask) {
                u32 evt_ring_id = __ffs(event_mask);

                event_mask ^= BIT(evt_ring_id);

                napi_schedule(&gsi->evt_ring[evt_ring_id].channel->napi);
        }
}

/* General event interrupts represent serious problems, so report them */
static void gsi_isr_general(struct gsi *gsi)
{
        struct device *dev = gsi->dev;
        u32 val;

        val = ioread32(gsi->virt + GSI_CNTXT_GSI_IRQ_STTS_OFFSET);
        iowrite32(val, gsi->virt + GSI_CNTXT_GSI_IRQ_CLR_OFFSET);

        dev_err(dev, "unexpected general interrupt 0x%08x\n", val);
}

/**
 * gsi_isr() - Top level GSI interrupt service routine
 * @irq:        Interrupt number (ignored)
 * @dev_id:     GSI pointer supplied to request_irq()
 *
 * This is the main handler function registered for the GSI IRQ. Each type
 * of interrupt has a separate handler function that is called from here.
 */
static irqreturn_t gsi_isr(int irq, void *dev_id)
{
        struct gsi *gsi = dev_id;
        u32 intr_mask;
        u32 cnt = 0;

        /* enum gsi_irq_type_id defines GSI interrupt types */
        while ((intr_mask = ioread32(gsi->virt + GSI_CNTXT_TYPE_IRQ_OFFSET))) {
                /* intr_mask contains bitmask of pending GSI interrupts */
                do {
                        u32 gsi_intr = BIT(__ffs(intr_mask));

                        intr_mask ^= gsi_intr;

                        switch (gsi_intr) {
                        case BIT(GSI_CH_CTRL):
                                gsi_isr_chan_ctrl(gsi);
                                break;
                        case BIT(GSI_EV_CTRL):
                                gsi_isr_evt_ctrl(gsi);
                                break;
                        case BIT(GSI_GLOB_EE):
                                gsi_isr_glob_ee(gsi);
                                break;
                        case BIT(GSI_IEOB):
                                gsi_isr_ieob(gsi);
                                break;
                        case BIT(GSI_GENERAL):
                                gsi_isr_general(gsi);
                                break;
                        default:
                                dev_err(gsi->dev,
                                        "unrecognized interrupt type 0x%08x\n",
                                        gsi_intr);
                                break;
                        }
                } while (intr_mask);

                if (++cnt > GSI_ISR_MAX_ITER) {
                        dev_err(gsi->dev, "interrupt flood\n");
                        break;
                }
        }

        return IRQ_HANDLED;
}

/* Init function for GSI IRQ lookup; there is no gsi_irq_exit() */
static int gsi_irq_init(struct gsi *gsi, struct platform_device *pdev)
{
        int ret;

        ret = platform_get_irq_byname(pdev, "gsi");
        if (ret <= 0)
                return ret ? : -EINVAL;

        gsi->irq = ret;

        return 0;
}

/* Return the transaction associated with a transfer completion event */
static struct gsi_trans *gsi_event_trans(struct gsi_channel *channel,
                                         struct gsi_event *event)
{
        u32 tre_offset;
        u32 tre_index;

        /* Event xfer_ptr records the TRE it's associated with */
        tre_offset = lower_32_bits(le64_to_cpu(event->xfer_ptr));
        tre_index = gsi_ring_index(&channel->tre_ring, tre_offset);

        return gsi_channel_trans_mapped(channel, tre_index);
}

/**
 * gsi_evt_ring_rx_update() - Record lengths of received data
 * @evt_ring:   Event ring associated with channel that received packets
 * @index:      Event index in ring reported by hardware
 *
 * Events for RX channels contain the actual number of bytes received into
 * the buffer.  Every event has a transaction associated with it, and here
 * we update transactions to record their actual received lengths.
 *
 * This function is called whenever we learn that the GSI hardware has filled
 * new events since the last time we checked.  The ring's index field tells
 * the first entry in need of processing.  The index provided is the
 * first *unfilled* event in the ring (following the last filled one).
 *
 * Events are sequential within the event ring, and transactions are
 * sequential within the transaction pool.
 *
 * Note that @index always refers to an element *within* the event ring.
 */
static void gsi_evt_ring_rx_update(struct gsi_evt_ring *evt_ring, u32 index)
{
        struct gsi_channel *channel = evt_ring->channel;
        struct gsi_ring *ring = &evt_ring->ring;
        struct gsi_trans_info *trans_info;
        struct gsi_event *event_done;
        struct gsi_event *event;
        struct gsi_trans *trans;
        u32 byte_count = 0;
        u32 old_index;
        u32 event_avail;

        trans_info = &channel->trans_info;

        /* We'll start with the oldest un-processed event.  RX channels
         * replenish receive buffers in single-TRE transactions, so we
         * can just map that event to its transaction.  Transactions
         * associated with completion events are consecutive.
         */
        old_index = ring->index;
        event = gsi_ring_virt(ring, old_index);
        trans = gsi_event_trans(channel, event);

        /* Compute the number of events to process before we wrap,
         * and determine when we'll be done processing events.
         */
        event_avail = ring->count - old_index % ring->count;
        event_done = gsi_ring_virt(ring, index);
        do {
                trans->len = __le16_to_cpu(event->len);
                byte_count += trans->len;

                /* Move on to the next event and transaction */
                if (--event_avail)
                        event++;
                else
                        event = gsi_ring_virt(ring, 0);
                trans = gsi_trans_pool_next(&trans_info->pool, trans);
        } while (event != event_done);

        /* We record RX bytes when they are received */
        channel->byte_count += byte_count;
        channel->trans_count++;
}

/* Initialize a ring, including allocating DMA memory for its entries */
static int gsi_ring_alloc(struct gsi *gsi, struct gsi_ring *ring, u32 count)
{
        u32 size = count * GSI_RING_ELEMENT_SIZE;
        struct device *dev = gsi->dev;
        dma_addr_t addr;

        /* Hardware requires a 2^n ring size, with alignment equal to size.
         * The DMA address returned by dma_alloc_coherent() is guaranteed to
         * be a power-of-2 number of pages, which satisfies the requirement.
         */
        ring->virt = dma_alloc_coherent(dev, size, &addr, GFP_KERNEL);
        if (!ring->virt)
                return -ENOMEM;

        ring->addr = addr;
        ring->count = count;

        return 0;
}

/* Free a previously-allocated ring */
static void gsi_ring_free(struct gsi *gsi, struct gsi_ring *ring)
{
        size_t size = ring->count * GSI_RING_ELEMENT_SIZE;

        dma_free_coherent(gsi->dev, size, ring->virt, ring->addr);
}

/* Allocate an available event ring id */
static int gsi_evt_ring_id_alloc(struct gsi *gsi)
{
        u32 evt_ring_id;

        if (gsi->event_bitmap == ~0U) {
                dev_err(gsi->dev, "event rings exhausted\n");
                return -ENOSPC;
        }

        evt_ring_id = ffz(gsi->event_bitmap);
        gsi->event_bitmap |= BIT(evt_ring_id);

        return (int)evt_ring_id;
}

/* Free a previously-allocated event ring id */
static void gsi_evt_ring_id_free(struct gsi *gsi, u32 evt_ring_id)
{
        gsi->event_bitmap &= ~BIT(evt_ring_id);
}

/* Ring a channel doorbell, reporting the first un-filled entry */
void gsi_channel_doorbell(struct gsi_channel *channel)
{
        struct gsi_ring *tre_ring = &channel->tre_ring;
        u32 channel_id = gsi_channel_id(channel);
        struct gsi *gsi = channel->gsi;
        u32 val;

        /* Note: index *must* be used modulo the ring count here */
        val = gsi_ring_addr(tre_ring, tre_ring->index % tre_ring->count);
        iowrite32(val, gsi->virt + GSI_CH_C_DOORBELL_0_OFFSET(channel_id));
}

/* Consult hardware, move any newly completed transactions to completed list */
static struct gsi_trans *gsi_channel_update(struct gsi_channel *channel)
{
        u32 evt_ring_id = channel->evt_ring_id;
        struct gsi *gsi = channel->gsi;
        struct gsi_evt_ring *evt_ring;
        struct gsi_trans *trans;
        struct gsi_ring *ring;
        u32 offset;
        u32 index;

        evt_ring = &gsi->evt_ring[evt_ring_id];
        ring = &evt_ring->ring;

        /* See if there's anything new to process; if not, we're done.  Note
         * that index always refers to an entry *within* the event ring.
         */
        offset = GSI_EV_CH_E_CNTXT_4_OFFSET(evt_ring_id);
        index = gsi_ring_index(ring, ioread32(gsi->virt + offset));
        if (index == ring->index % ring->count)
                return NULL;

        /* Get the transaction for the latest completed event.  Take a
         * reference to keep it from completing before we give the events
         * for this and previous transactions back to the hardware.
         */
        trans = gsi_event_trans(channel, gsi_ring_virt(ring, index - 1));
        refcount_inc(&trans->refcount);

        /* For RX channels, update each completed transaction with the number
         * of bytes that were actually received.  For TX channels, report
         * the number of transactions and bytes this completion represents
         * up the network stack.
         */
        if (channel->toward_ipa)
                gsi_channel_tx_update(channel, trans);
        else
                gsi_evt_ring_rx_update(evt_ring, index);

        gsi_trans_move_complete(trans);

        /* Tell the hardware we've handled these events */
        gsi_evt_ring_doorbell(channel->gsi, channel->evt_ring_id, index);

        gsi_trans_free(trans);

        return gsi_channel_trans_complete(channel);
}

/**
 * gsi_channel_poll_one() - Return a single completed transaction on a channel
 * @channel:    Channel to be polled
 *
 * Return:      Transaction pointer, or null if none are available
 *
 * This function returns the first entry on a channel's completed transaction
 * list.  If that list is empty, the hardware is consulted to determine
 * whether any new transactions have completed.  If so, they're moved to the
 * completed list and the new first entry is returned.  If there are no more
 * completed transactions, a null pointer is returned.
 */
static struct gsi_trans *gsi_channel_poll_one(struct gsi_channel *channel)
{
        struct gsi_trans *trans;

        /* Get the first transaction from the completed list */
        trans = gsi_channel_trans_complete(channel);
        if (!trans)     /* List is empty; see if there's more to do */
                trans = gsi_channel_update(channel);

        if (trans)
                gsi_trans_move_polled(trans);

        return trans;
}

/**
 * gsi_channel_poll() - NAPI poll function for a channel
 * @napi:       NAPI structure for the channel
 * @budget:     Budget supplied by NAPI core
 *
 * Return:      Number of items polled (<= budget)
 *
 * Single transactions completed by hardware are polled until either
 * the budget is exhausted, or there are no more.  Each transaction
 * polled is passed to gsi_trans_complete(), to perform remaining
 * completion processing and retire/free the transaction.
 */
static int gsi_channel_poll(struct napi_struct *napi, int budget)
{
        struct gsi_channel *channel;
        int count;

        channel = container_of(napi, struct gsi_channel, napi);
        for (count = 0; count < budget; count++) {
                struct gsi_trans *trans;

                trans = gsi_channel_poll_one(channel);
                if (!trans)
                        break;
                gsi_trans_complete(trans);
        }

        if (count < budget && napi_complete(napi))
                gsi_irq_ieob_enable_one(channel->gsi, channel->evt_ring_id);

        return count;
}

/* The event bitmap represents which event ids are available for allocation.
 * Set bits are not available, clear bits can be used.  This function
 * initializes the map so all events supported by the hardware are available,
 * then precludes any reserved events from being allocated.
 */
static u32 gsi_event_bitmap_init(u32 evt_ring_max)
{
        u32 event_bitmap = GENMASK(BITS_PER_LONG - 1, evt_ring_max);

        event_bitmap |= GENMASK(GSI_MHI_EVENT_ID_END, GSI_MHI_EVENT_ID_START);

        return event_bitmap;
}

/* Setup function for a single channel */
static int gsi_channel_setup_one(struct gsi *gsi, u32 channel_id)
{
        struct gsi_channel *channel = &gsi->channel[channel_id];
        u32 evt_ring_id = channel->evt_ring_id;
        int ret;

        if (!gsi_channel_initialized(channel))
                return 0;

        ret = gsi_evt_ring_alloc_command(gsi, evt_ring_id);
        if (ret)
                return ret;

        gsi_evt_ring_program(gsi, evt_ring_id);

        ret = gsi_channel_alloc_command(gsi, channel_id);
        if (ret)
                goto err_evt_ring_de_alloc;

        gsi_channel_program(channel, true);

        if (channel->toward_ipa)
                netif_tx_napi_add(&gsi->dummy_dev, &channel->napi,
                                  gsi_channel_poll, NAPI_POLL_WEIGHT);
        else
                netif_napi_add(&gsi->dummy_dev, &channel->napi,
                               gsi_channel_poll, NAPI_POLL_WEIGHT);

        return 0;

err_evt_ring_de_alloc:
        /* We've done nothing with the event ring yet so don't reset */
        gsi_evt_ring_de_alloc_command(gsi, evt_ring_id);

        return ret;
}

/* Inverse of gsi_channel_setup_one() */
static void gsi_channel_teardown_one(struct gsi *gsi, u32 channel_id)
{
        struct gsi_channel *channel = &gsi->channel[channel_id];
        u32 evt_ring_id = channel->evt_ring_id;

        if (!gsi_channel_initialized(channel))
                return;

        netif_napi_del(&channel->napi);

        gsi_channel_de_alloc_command(gsi, channel_id);
        gsi_evt_ring_reset_command(gsi, evt_ring_id);
        gsi_evt_ring_de_alloc_command(gsi, evt_ring_id);
}

static int gsi_generic_command(struct gsi *gsi, u32 channel_id,
                               enum gsi_generic_cmd_opcode opcode)
{
        struct completion *completion = &gsi->completion;
        bool timeout;
        u32 val;

        /* The error global interrupt type is always enabled (until we
         * teardown), so we won't change that.  A generic EE command
         * completes with a GSI global interrupt of type GP_INT1.  We
         * only perform one generic command at a time (to allocate or
         * halt a modem channel) and only from this function.  So we
         * enable the GP_INT1 IRQ type here while we're expecting it.
         */
        val = BIT(ERROR_INT) | BIT(GP_INT1);
        iowrite32(val, gsi->virt + GSI_CNTXT_GLOB_IRQ_EN_OFFSET);

        /* First zero the result code field */
        val = ioread32(gsi->virt + GSI_CNTXT_SCRATCH_0_OFFSET);
        val &= ~GENERIC_EE_RESULT_FMASK;
        iowrite32(val, gsi->virt + GSI_CNTXT_SCRATCH_0_OFFSET);

        /* Now issue the command */
        val = u32_encode_bits(opcode, GENERIC_OPCODE_FMASK);
        val |= u32_encode_bits(channel_id, GENERIC_CHID_FMASK);
        val |= u32_encode_bits(GSI_EE_MODEM, GENERIC_EE_FMASK);

        timeout = !gsi_command(gsi, GSI_GENERIC_CMD_OFFSET, val, completion);

        /* Disable the GP_INT1 IRQ type again */
        iowrite32(BIT(ERROR_INT), gsi->virt + GSI_CNTXT_GLOB_IRQ_EN_OFFSET);

        if (!timeout)
                return gsi->result;

        dev_err(gsi->dev, "GSI generic command %u to channel %u timed out\n",
                opcode, channel_id);

        return -ETIMEDOUT;
}

static int gsi_modem_channel_alloc(struct gsi *gsi, u32 channel_id)
{
        return gsi_generic_command(gsi, channel_id,
                                   GSI_GENERIC_ALLOCATE_CHANNEL);
}

static void gsi_modem_channel_halt(struct gsi *gsi, u32 channel_id)
{
        u32 retries = GSI_CHANNEL_MODEM_HALT_RETRIES;
        int ret;

        do
                ret = gsi_generic_command(gsi, channel_id,
                                          GSI_GENERIC_HALT_CHANNEL);
        while (ret == -EAGAIN && retries--);

        if (ret)
                dev_err(gsi->dev, "error %d halting modem channel %u\n",
                        ret, channel_id);
}

/* Setup function for channels */
static int gsi_channel_setup(struct gsi *gsi)
{
        u32 channel_id = 0;
        u32 mask;
        int ret;

        gsi_irq_enable(gsi);

        mutex_lock(&gsi->mutex);

        do {
                ret = gsi_channel_setup_one(gsi, channel_id);
                if (ret)
                        goto err_unwind;
        } while (++channel_id < gsi->channel_count);

        /* Make sure no channels were defined that hardware does not support */
        while (channel_id < GSI_CHANNEL_COUNT_MAX) {
                struct gsi_channel *channel = &gsi->channel[channel_id++];

                if (!gsi_channel_initialized(channel))
                        continue;

                ret = -EINVAL;
                dev_err(gsi->dev, "channel %u not supported by hardware\n",
                        channel_id - 1);
                channel_id = gsi->channel_count;
                goto err_unwind;
        }

        /* Allocate modem channels if necessary */
        mask = gsi->modem_channel_bitmap;
        while (mask) {
                u32 modem_channel_id = __ffs(mask);

                ret = gsi_modem_channel_alloc(gsi, modem_channel_id);
                if (ret)
                        goto err_unwind_modem;

                /* Clear bit from mask only after success (for unwind) */
                mask ^= BIT(modem_channel_id);
        }

        mutex_unlock(&gsi->mutex);

        return 0;

err_unwind_modem:
        /* Compute which modem channels need to be deallocated */
        mask ^= gsi->modem_channel_bitmap;
        while (mask) {
                channel_id = __fls(mask);

                mask ^= BIT(channel_id);

                gsi_modem_channel_halt(gsi, channel_id);
        }

err_unwind:
        while (channel_id--)
                gsi_channel_teardown_one(gsi, channel_id);

        mutex_unlock(&gsi->mutex);

        gsi_irq_disable(gsi);

        return ret;
}

/* Inverse of gsi_channel_setup() */
static void gsi_channel_teardown(struct gsi *gsi)
{
        u32 mask = gsi->modem_channel_bitmap;
        u32 channel_id;

        mutex_lock(&gsi->mutex);

        while (mask) {
                channel_id = __fls(mask);

                mask ^= BIT(channel_id);

                gsi_modem_channel_halt(gsi, channel_id);
        }

        channel_id = gsi->channel_count - 1;
        do
                gsi_channel_teardown_one(gsi, channel_id);
        while (channel_id--);

        mutex_unlock(&gsi->mutex);

        gsi_irq_disable(gsi);
}

/* Turn off all GSI interrupts initially */
static int gsi_irq_setup(struct gsi *gsi)
{
        int ret;

        /* Writing 1 indicates IRQ interrupts; 0 would be MSI */
        iowrite32(1, gsi->virt + GSI_CNTXT_INTSET_OFFSET);

        /* Disable all interrupt types */
        gsi_irq_type_update(gsi, 0);

        /* Clear all type-specific interrupt masks */
        iowrite32(0, gsi->virt + GSI_CNTXT_SRC_CH_IRQ_MSK_OFFSET);
        iowrite32(0, gsi->virt + GSI_CNTXT_SRC_EV_CH_IRQ_MSK_OFFSET);
        iowrite32(0, gsi->virt + GSI_CNTXT_GLOB_IRQ_EN_OFFSET);
        iowrite32(0, gsi->virt + GSI_CNTXT_SRC_IEOB_IRQ_MSK_OFFSET);

        /* The inter-EE interrupts are not supported for IPA v3.0-v3.1 */
        if (gsi->version > IPA_VERSION_3_1) {
                u32 offset;

                /* These registers are in the non-adjusted address range */
                offset = GSI_INTER_EE_SRC_CH_IRQ_MSK_OFFSET;
                iowrite32(0, gsi->virt_raw + offset);
                offset = GSI_INTER_EE_SRC_EV_CH_IRQ_MSK_OFFSET;
                iowrite32(0, gsi->virt_raw + offset);
        }

        iowrite32(0, gsi->virt + GSI_CNTXT_GSI_IRQ_EN_OFFSET);

        ret = request_irq(gsi->irq, gsi_isr, 0, "gsi", gsi);
        if (ret)
                dev_err(gsi->dev, "error %d requesting \"gsi\" IRQ\n", ret);

        return ret;
}

static void gsi_irq_teardown(struct gsi *gsi)
{
        free_irq(gsi->irq, gsi);
}

/* Get # supported channel and event rings; there is no gsi_ring_teardown() */
static int gsi_ring_setup(struct gsi *gsi)
{
        struct device *dev = gsi->dev;
        u32 count;
        u32 val;

        if (gsi->version < IPA_VERSION_3_5_1) {
                /* No HW_PARAM_2 register prior to IPA v3.5.1, assume the max */
                gsi->channel_count = GSI_CHANNEL_COUNT_MAX;
                gsi->evt_ring_count = GSI_EVT_RING_COUNT_MAX;

                return 0;
        }

        val = ioread32(gsi->virt + GSI_GSI_HW_PARAM_2_OFFSET);

        count = u32_get_bits(val, NUM_CH_PER_EE_FMASK);
        if (!count) {
                dev_err(dev, "GSI reports zero channels supported\n");
                return -EINVAL;
        }
        if (count > GSI_CHANNEL_COUNT_MAX) {
                dev_warn(dev, "limiting to %u channels; hardware supports %u\n",
                         GSI_CHANNEL_COUNT_MAX, count);
                count = GSI_CHANNEL_COUNT_MAX;
        }
        gsi->channel_count = count;

        count = u32_get_bits(val, NUM_EV_PER_EE_FMASK);
        if (!count) {
                dev_err(dev, "GSI reports zero event rings supported\n");
                return -EINVAL;
        }
        if (count > GSI_EVT_RING_COUNT_MAX) {
                dev_warn(dev,
                         "limiting to %u event rings; hardware supports %u\n",
                         GSI_EVT_RING_COUNT_MAX, count);
                count = GSI_EVT_RING_COUNT_MAX;
        }
        gsi->evt_ring_count = count;

        return 0;
}

/* Setup function for GSI.  GSI firmware must be loaded and initialized */
int gsi_setup(struct gsi *gsi)
{
        u32 val;
        int ret;

        /* Here is where we first touch the GSI hardware */
        val = ioread32(gsi->virt + GSI_GSI_STATUS_OFFSET);
        if (!(val & ENABLED_FMASK)) {
                dev_err(gsi->dev, "GSI has not been enabled\n");
                return -EIO;
        }

        ret = gsi_irq_setup(gsi);
        if (ret)
                return ret;

        ret = gsi_ring_setup(gsi);      /* No matching teardown required */
        if (ret)
                goto err_irq_teardown;

        /* Initialize the error log */
        iowrite32(0, gsi->virt + GSI_ERROR_LOG_OFFSET);

        ret = gsi_channel_setup(gsi);
        if (ret)
                goto err_irq_teardown;

        return 0;

err_irq_teardown:
        gsi_irq_teardown(gsi);

        return ret;
}

/* Inverse of gsi_setup() */
void gsi_teardown(struct gsi *gsi)
{
        gsi_channel_teardown(gsi);
        gsi_irq_teardown(gsi);
}

/* Initialize a channel's event ring */
static int gsi_channel_evt_ring_init(struct gsi_channel *channel)
{
        struct gsi *gsi = channel->gsi;
        struct gsi_evt_ring *evt_ring;
        int ret;

        ret = gsi_evt_ring_id_alloc(gsi);
        if (ret < 0)
                return ret;
        channel->evt_ring_id = ret;

        evt_ring = &gsi->evt_ring[channel->evt_ring_id];
        evt_ring->channel = channel;

        ret = gsi_ring_alloc(gsi, &evt_ring->ring, channel->event_count);
        if (!ret)
                return 0;       /* Success! */

        dev_err(gsi->dev, "error %d allocating channel %u event ring\n",
                ret, gsi_channel_id(channel));

        gsi_evt_ring_id_free(gsi, channel->evt_ring_id);

        return ret;
}

/* Inverse of gsi_channel_evt_ring_init() */
static void gsi_channel_evt_ring_exit(struct gsi_channel *channel)
{
        u32 evt_ring_id = channel->evt_ring_id;
        struct gsi *gsi = channel->gsi;
        struct gsi_evt_ring *evt_ring;

        evt_ring = &gsi->evt_ring[evt_ring_id];
        gsi_ring_free(gsi, &evt_ring->ring);
        gsi_evt_ring_id_free(gsi, evt_ring_id);
}

/* Init function for event rings; there is no gsi_evt_ring_exit() */
static void gsi_evt_ring_init(struct gsi *gsi)
{
        u32 evt_ring_id = 0;

        gsi->event_bitmap = gsi_event_bitmap_init(GSI_EVT_RING_COUNT_MAX);
        gsi->ieob_enabled_bitmap = 0;
        do
                init_completion(&gsi->evt_ring[evt_ring_id].completion);
        while (++evt_ring_id < GSI_EVT_RING_COUNT_MAX);
}

static bool gsi_channel_data_valid(struct gsi *gsi,
                                   const struct ipa_gsi_endpoint_data *data)
{
        u32 channel_id = data->channel_id;
        struct device *dev = gsi->dev;

        /* Make sure channel ids are in the range driver supports */
        if (channel_id >= GSI_CHANNEL_COUNT_MAX) {
                dev_err(dev, "bad channel id %u; must be less than %u\n",
                        channel_id, GSI_CHANNEL_COUNT_MAX);
                return false;
        }

        if (data->ee_id != GSI_EE_AP && data->ee_id != GSI_EE_MODEM) {
                dev_err(dev, "bad EE id %u; not AP or modem\n", data->ee_id);
                return false;
        }

        if (!data->channel.tlv_count ||
            data->channel.tlv_count > GSI_TLV_MAX) {
                dev_err(dev, "channel %u bad tlv_count %u; must be 1..%u\n",
                        channel_id, data->channel.tlv_count, GSI_TLV_MAX);
                return false;
        }

        /* We have to allow at least one maximally-sized transaction to
         * be outstanding (which would use tlv_count TREs).  Given how
         * gsi_channel_tre_max() is computed, tre_count has to be almost
         * twice the TLV FIFO size to satisfy this requirement.
         */
        if (data->channel.tre_count < 2 * data->channel.tlv_count - 1) {
                dev_err(dev, "channel %u TLV count %u exceeds TRE count %u\n",
                        channel_id, data->channel.tlv_count,
                        data->channel.tre_count);
                return false;
        }

        if (!is_power_of_2(data->channel.tre_count)) {
                dev_err(dev, "channel %u bad tre_count %u; not power of 2\n",
                        channel_id, data->channel.tre_count);
                return false;
        }

        if (!is_power_of_2(data->channel.event_count)) {
                dev_err(dev, "channel %u bad event_count %u; not power of 2\n",
                        channel_id, data->channel.event_count);
                return false;
        }

        return true;
}

/* Init function for a single channel */
static int gsi_channel_init_one(struct gsi *gsi,
                                const struct ipa_gsi_endpoint_data *data,
                                bool command)
{
        struct gsi_channel *channel;
        u32 tre_count;
        int ret;

        if (!gsi_channel_data_valid(gsi, data))
                return -EINVAL;

        /* Worst case we need an event for every outstanding TRE */
        if (data->channel.tre_count > data->channel.event_count) {
                tre_count = data->channel.event_count;
                dev_warn(gsi->dev, "channel %u limited to %u TREs\n",
                         data->channel_id, tre_count);
        } else {
                tre_count = data->channel.tre_count;
        }

        channel = &gsi->channel[data->channel_id];
        memset(channel, 0, sizeof(*channel));

        channel->gsi = gsi;
        channel->toward_ipa = data->toward_ipa;
        channel->command = command;
        channel->tlv_count = data->channel.tlv_count;
        channel->tre_count = tre_count;
        channel->event_count = data->channel.event_count;
        init_completion(&channel->completion);

        ret = gsi_channel_evt_ring_init(channel);
        if (ret)
                goto err_clear_gsi;

        ret = gsi_ring_alloc(gsi, &channel->tre_ring, data->channel.tre_count);
        if (ret) {
                dev_err(gsi->dev, "error %d allocating channel %u ring\n",
                        ret, data->channel_id);
                goto err_channel_evt_ring_exit;
        }

        ret = gsi_channel_trans_init(gsi, data->channel_id);
        if (ret)
                goto err_ring_free;

        if (command) {
                u32 tre_max = gsi_channel_tre_max(gsi, data->channel_id);

                ret = ipa_cmd_pool_init(channel, tre_max);
        }
        if (!ret)
                return 0;       /* Success! */

        gsi_channel_trans_exit(channel);
err_ring_free:
        gsi_ring_free(gsi, &channel->tre_ring);
err_channel_evt_ring_exit:
        gsi_channel_evt_ring_exit(channel);
err_clear_gsi:
        channel->gsi = NULL;    /* Mark it not (fully) initialized */

        return ret;
}

/* Inverse of gsi_channel_init_one() */
static void gsi_channel_exit_one(struct gsi_channel *channel)
{
        if (!gsi_channel_initialized(channel))
                return;

        if (channel->command)
                ipa_cmd_pool_exit(channel);
        gsi_channel_trans_exit(channel);
        gsi_ring_free(channel->gsi, &channel->tre_ring);
        gsi_channel_evt_ring_exit(channel);
}

/* Init function for channels */
static int gsi_channel_init(struct gsi *gsi, u32 count,
                            const struct ipa_gsi_endpoint_data *data)
{
        bool modem_alloc;
        int ret = 0;
        u32 i;

        /* IPA v4.2 requires the AP to allocate channels for the modem */
        modem_alloc = gsi->version == IPA_VERSION_4_2;

        gsi_evt_ring_init(gsi);                 /* No matching exit required */

        /* The endpoint data array is indexed by endpoint name */
        for (i = 0; i < count; i++) {
                bool command = i == IPA_ENDPOINT_AP_COMMAND_TX;

                if (ipa_gsi_endpoint_data_empty(&data[i]))
                        continue;       /* Skip over empty slots */

                /* Mark modem channels to be allocated (hardware workaround) */
                if (data[i].ee_id == GSI_EE_MODEM) {
                        if (modem_alloc)
                                gsi->modem_channel_bitmap |=
                                                BIT(data[i].channel_id);
                        continue;
                }

                ret = gsi_channel_init_one(gsi, &data[i], command);
                if (ret)
                        goto err_unwind;
        }

        return ret;

err_unwind:
        while (i--) {
                if (ipa_gsi_endpoint_data_empty(&data[i]))
                        continue;
                if (modem_alloc && data[i].ee_id == GSI_EE_MODEM) {
                        gsi->modem_channel_bitmap &= ~BIT(data[i].channel_id);
                        continue;
                }
                gsi_channel_exit_one(&gsi->channel[data->channel_id]);
        }

        return ret;
}

/* Inverse of gsi_channel_init() */
static void gsi_channel_exit(struct gsi *gsi)
{
        u32 channel_id = GSI_CHANNEL_COUNT_MAX - 1;

        do
                gsi_channel_exit_one(&gsi->channel[channel_id]);
        while (channel_id--);
        gsi->modem_channel_bitmap = 0;
}

/* Init function for GSI.  GSI hardware does not need to be "ready" */
int gsi_init(struct gsi *gsi, struct platform_device *pdev,
             enum ipa_version version, u32 count,
             const struct ipa_gsi_endpoint_data *data)
{
        struct device *dev = &pdev->dev;
        struct resource *res;
        resource_size_t size;
        u32 adjust;
        int ret;

        gsi_validate_build();

        gsi->dev = dev;
        gsi->version = version;

        /* GSI uses NAPI on all channels.  Create a dummy network device
         * for the channel NAPI contexts to be associated with.
         */
        init_dummy_netdev(&gsi->dummy_dev);

        /* Get GSI memory range and map it */
        res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "gsi");
        if (!res) {
                dev_err(dev, "DT error getting \"gsi\" memory property\n");
                return -ENODEV;
        }

        size = resource_size(res);
        if (res->start > U32_MAX || size > U32_MAX - res->start) {
                dev_err(dev, "DT memory resource \"gsi\" out of range\n");
                return -EINVAL;
        }

        /* Make sure we can make our pointer adjustment if necessary */
        adjust = gsi->version < IPA_VERSION_4_5 ? 0 : GSI_EE_REG_ADJUST;
        if (res->start < adjust) {
                dev_err(dev, "DT memory resource \"gsi\" too low (< %u)\n",
                        adjust);
                return -EINVAL;
        }

        gsi->virt_raw = ioremap(res->start, size);
        if (!gsi->virt_raw) {
                dev_err(dev, "unable to remap \"gsi\" memory\n");
                return -ENOMEM;
        }
        /* Most registers are accessed using an adjusted register range */
        gsi->virt = gsi->virt_raw - adjust;

        init_completion(&gsi->completion);

        ret = gsi_irq_init(gsi, pdev);  /* No matching exit required */
        if (ret)
                goto err_iounmap;

        ret = gsi_channel_init(gsi, count, data);
        if (ret)
                goto err_iounmap;

        mutex_init(&gsi->mutex);

        return 0;

err_iounmap:
        iounmap(gsi->virt_raw);

        return ret;
}

/* Inverse of gsi_init() */
void gsi_exit(struct gsi *gsi)
{
        mutex_destroy(&gsi->mutex);
        gsi_channel_exit(gsi);
        iounmap(gsi->virt_raw);
}

/* The maximum number of outstanding TREs on a channel.  This limits
 * a channel's maximum number of transactions outstanding (worst case
 * is one TRE per transaction).
 *
 * The absolute limit is the number of TREs in the channel's TRE ring,
 * and in theory we should be able use all of them.  But in practice,
 * doing that led to the hardware reporting exhaustion of event ring
 * slots for writing completion information.  So the hardware limit
 * would be (tre_count - 1).
 *
 * We reduce it a bit further though.  Transaction resource pools are
 * sized to be a little larger than this maximum, to allow resource
 * allocations to always be contiguous.  The number of entries in a
 * TRE ring buffer is a power of 2, and the extra resources in a pool
 * tends to nearly double the memory allocated for it.  Reducing the
 * maximum number of outstanding TREs allows the number of entries in
 * a pool to avoid crossing that power-of-2 boundary, and this can
 * substantially reduce pool memory requirements.  The number we
 * reduce it by matches the number added in gsi_trans_pool_init().
 */
u32 gsi_channel_tre_max(struct gsi *gsi, u32 channel_id)
{
        struct gsi_channel *channel = &gsi->channel[channel_id];

        /* Hardware limit is channel->tre_count - 1 */
        return channel->tre_count - (channel->tlv_count - 1);
}

/* Returns the maximum number of TREs in a single transaction for a channel */
u32 gsi_channel_trans_tre_max(struct gsi *gsi, u32 channel_id)
{
        struct gsi_channel *channel = &gsi->channel[channel_id];

        return channel->tlv_count;
}