drivers/gpu/drm/drm_writeback.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * (C) COPYRIGHT 2016 ARM Limited. All rights reserved.
   4  * Author: Brian Starkey <[email protected]>
   5  *
   6  * This program is free software and is provided to you under the terms of the
   7  * GNU General Public License version 2 as published by the Free Software
   8  * Foundation, and any use by you of this program is subject to the terms
   9  * of such GNU licence.
  10  */
  11
  12 #include <linux/dma-fence.h>
  13
  14 #include <drm/drm_crtc.h>
  15 #include <drm/drm_device.h>
  16 #include <drm/drm_drv.h>
  17 #include <drm/drm_framebuffer.h>
  18 #include <drm/drm_modeset_helper_vtables.h>
  19 #include <drm/drm_property.h>
  20 #include <drm/drm_writeback.h>
  21
  22 /**
  23  * DOC: overview
  24  *
  25  * Writeback connectors are used to expose hardware which can write the output
  26  * from a CRTC to a memory buffer. They are used and act similarly to other
  27  * types of connectors, with some important differences:
  28  *
  29  * * Writeback connectors don't provide a way to output visually to the user.
  30  *
  31  * * Writeback connectors are visible to userspace only when the client sets
  32  *   DRM_CLIENT_CAP_WRITEBACK_CONNECTORS.
  33  *
  34  * * Writeback connectors don't have EDID.
  35  *
  36  * A framebuffer may only be attached to a writeback connector when the
  37  * connector is attached to a CRTC. The WRITEBACK_FB_ID property which sets the
  38  * framebuffer applies only to a single commit (see below). A framebuffer may
  39  * not be attached while the CRTC is off.
  40  *
  41  * Unlike with planes, when a writeback framebuffer is removed by userspace DRM
  42  * makes no attempt to remove it from active use by the connector. This is
  43  * because no method is provided to abort a writeback operation, and in any
  44  * case making a new commit whilst a writeback is ongoing is undefined (see
  45  * WRITEBACK_OUT_FENCE_PTR below). As soon as the current writeback is finished,
  46  * the framebuffer will automatically no longer be in active use. As it will
  47  * also have already been removed from the framebuffer list, there will be no
  48  * way for any userspace application to retrieve a reference to it in the
  49  * intervening period.
  50  *
  51  * Writeback connectors have some additional properties, which userspace
  52  * can use to query and control them:
  53  *
  54  *  "WRITEBACK_FB_ID":
  55  *      Write-only object property storing a DRM_MODE_OBJECT_FB: it stores the
  56  *      framebuffer to be written by the writeback connector. This property is
  57  *      similar to the FB_ID property on planes, but will always read as zero
  58  *      and is not preserved across commits.
  59  *      Userspace must set this property to an output buffer every time it
  60  *      wishes the buffer to get filled.
  61  *
  62  *  "WRITEBACK_PIXEL_FORMATS":
  63  *      Immutable blob property to store the supported pixel formats table. The
  64  *      data is an array of u32 DRM_FORMAT_* fourcc values.
  65  *      Userspace can use this blob to find out what pixel formats are supported
  66  *      by the connector's writeback engine.
  67  *
  68  *  "WRITEBACK_OUT_FENCE_PTR":
  69  *      Userspace can use this property to provide a pointer for the kernel to
  70  *      fill with a sync_file file descriptor, which will signal once the
  71  *      writeback is finished. The value should be the address of a 32-bit
  72  *      signed integer, cast to a u64.
  73  *      Userspace should wait for this fence to signal before making another
  74  *      commit affecting any of the same CRTCs, Planes or Connectors.
  75  *      **Failure to do so will result in undefined behaviour.**
  76  *      For this reason it is strongly recommended that all userspace
  77  *      applications making use of writeback connectors *always* retrieve an
  78  *      out-fence for the commit and use it appropriately.
  79  *      From userspace, this property will always read as zero.
  80  */
  81
  82 #define fence_to_wb_connector(x) container_of(x->lock, \
  83                                               struct drm_writeback_connector, \
  84                                               fence_lock)
  85
  86 static const char *drm_writeback_fence_get_driver_name(struct dma_fence *fence)
  87 {
  88         struct drm_writeback_connector *wb_connector =
  89                 fence_to_wb_connector(fence);
  90
  91         return wb_connector->base.dev->driver->name;
  92 }
  93
  94 static const char *
  95 drm_writeback_fence_get_timeline_name(struct dma_fence *fence)
  96 {
  97         struct drm_writeback_connector *wb_connector =
  98                 fence_to_wb_connector(fence);
  99
 100         return wb_connector->timeline_name;
 101 }
 102
 103 static const struct dma_fence_ops drm_writeback_fence_ops = {
 104         .get_driver_name = drm_writeback_fence_get_driver_name,
 105         .get_timeline_name = drm_writeback_fence_get_timeline_name,
 106 };
 107
 108 static int create_writeback_properties(struct drm_device *dev)
 109 {
 110         struct drm_property *prop;
 111
 112         if (!dev->mode_config.writeback_fb_id_property) {
 113                 prop = drm_property_create_object(dev, DRM_MODE_PROP_ATOMIC,
 114                                                   "WRITEBACK_FB_ID",
 115                                                   DRM_MODE_OBJECT_FB);
 116                 if (!prop)
 117                         return -ENOMEM;
 118                 dev->mode_config.writeback_fb_id_property = prop;
 119         }
 120
 121         if (!dev->mode_config.writeback_pixel_formats_property) {
 122                 prop = drm_property_create(dev, DRM_MODE_PROP_BLOB |
 123                                            DRM_MODE_PROP_ATOMIC |
 124                                            DRM_MODE_PROP_IMMUTABLE,
 125                                            "WRITEBACK_PIXEL_FORMATS", 0);
 126                 if (!prop)
 127                         return -ENOMEM;
 128                 dev->mode_config.writeback_pixel_formats_property = prop;
 129         }
 130
 131         if (!dev->mode_config.writeback_out_fence_ptr_property) {
 132                 prop = drm_property_create_range(dev, DRM_MODE_PROP_ATOMIC,
 133                                                  "WRITEBACK_OUT_FENCE_PTR", 0,
 134                                                  U64_MAX);
 135                 if (!prop)
 136                         return -ENOMEM;
 137                 dev->mode_config.writeback_out_fence_ptr_property = prop;
 138         }
 139
 140         return 0;
 141 }
 142
 143 static const struct drm_encoder_funcs drm_writeback_encoder_funcs = {
 144         .destroy = drm_encoder_cleanup,
 145 };
 146
 147 /**
 148  * drm_writeback_connector_init - Initialize a writeback connector and its properties
 149  * @dev: DRM device
 150  * @wb_connector: Writeback connector to initialize
 151  * @con_funcs: Connector funcs vtable
 152  * @enc_helper_funcs: Encoder helper funcs vtable to be used by the internal encoder
 153  * @formats: Array of supported pixel formats for the writeback engine
 154  * @n_formats: Length of the formats array
 155  * @possible_crtcs: possible crtcs for the internal writeback encoder
 156  *
 157  * This function creates the writeback-connector-specific properties if they
 158  * have not been already created, initializes the connector as
 159  * type DRM_MODE_CONNECTOR_WRITEBACK, and correctly initializes the property
 160  * values. It will also create an internal encoder associated with the
 161  * drm_writeback_connector and set it to use the @enc_helper_funcs vtable for
 162  * the encoder helper.
 163  *
 164  * Drivers should always use this function instead of drm_connector_init() to
 165  * set up writeback connectors.
 166  *
 167  * Returns: 0 on success, or a negative error code
 168  */
 169 int drm_writeback_connector_init(struct drm_device *dev,
 170                                  struct drm_writeback_connector *wb_connector,
 171                                  const struct drm_connector_funcs *con_funcs,
 172                                  const struct drm_encoder_helper_funcs *enc_helper_funcs,
 173                                  const u32 *formats, int n_formats,
 174                                  u32 possible_crtcs)
 175 {
 176         int ret = 0;
 177
 178         drm_encoder_helper_add(&wb_connector->encoder, enc_helper_funcs);
 179
 180         wb_connector->encoder.possible_crtcs = possible_crtcs;
 181
 182         ret = drm_encoder_init(dev, &wb_connector->encoder,
 183                                &drm_writeback_encoder_funcs,
 184                                DRM_MODE_ENCODER_VIRTUAL, NULL);
 185         if (ret)
 186                 return ret;
 187
 188         ret = drm_writeback_connector_init_with_encoder(dev, wb_connector, &wb_connector->encoder,
 189                         con_funcs, formats, n_formats);
 190
 191         if (ret)
 192                 drm_encoder_cleanup(&wb_connector->encoder);
 193
 194         return ret;
 195 }
 196 EXPORT_SYMBOL(drm_writeback_connector_init);
 197
 198 /**
 199  * drm_writeback_connector_init_with_encoder - Initialize a writeback connector with
 200  * a custom encoder
 201  *
 202  * @dev: DRM device
 203  * @wb_connector: Writeback connector to initialize
 204  * @enc: handle to the already initialized drm encoder
 205  * @con_funcs: Connector funcs vtable
 206  * @formats: Array of supported pixel formats for the writeback engine
 207  * @n_formats: Length of the formats array
 208  *
 209  * This function creates the writeback-connector-specific properties if they
 210  * have not been already created, initializes the connector as
 211  * type DRM_MODE_CONNECTOR_WRITEBACK, and correctly initializes the property
 212  * values.
 213  *
 214  * This function assumes that the drm_writeback_connector's encoder has already been
 215  * created and initialized before invoking this function.
 216  *
 217  * In addition, this function also assumes that callers of this API will manage
 218  * assigning the encoder helper functions, possible_crtcs and any other encoder
 219  * specific operation.
 220  *
 221  * Drivers should always use this function instead of drm_connector_init() to
 222  * set up writeback connectors if they want to manage themselves the lifetime of the
 223  * associated encoder.
 224  *
 225  * Returns: 0 on success, or a negative error code
 226  */
 227 int drm_writeback_connector_init_with_encoder(struct drm_device *dev,
 228                 struct drm_writeback_connector *wb_connector, struct drm_encoder *enc,
 229                 const struct drm_connector_funcs *con_funcs, const u32 *formats,
 230                 int n_formats)
 231 {
 232         struct drm_property_blob *blob;
 233         struct drm_connector *connector = &wb_connector->base;
 234         struct drm_mode_config *config = &dev->mode_config;
 235         int ret = create_writeback_properties(dev);
 236
 237         if (ret != 0)
 238                 return ret;
 239
 240         blob = drm_property_create_blob(dev, n_formats * sizeof(*formats),
 241                                         formats);
 242         if (IS_ERR(blob))
 243                 return PTR_ERR(blob);
 244
 245
 246         connector->interlace_allowed = 0;
 247
 248         ret = drm_connector_init(dev, connector, con_funcs,
 249                                  DRM_MODE_CONNECTOR_WRITEBACK);
 250         if (ret)
 251                 goto connector_fail;
 252
 253         ret = drm_connector_attach_encoder(connector, enc);
 254         if (ret)
 255                 goto attach_fail;
 256
 257         INIT_LIST_HEAD(&wb_connector->job_queue);
 258         spin_lock_init(&wb_connector->job_lock);
 259
 260         wb_connector->fence_context = dma_fence_context_alloc(1);
 261         spin_lock_init(&wb_connector->fence_lock);
 262         snprintf(wb_connector->timeline_name,
 263                  sizeof(wb_connector->timeline_name),
 264                  "CONNECTOR:%d-%s", connector->base.id, connector->name);
 265
 266         drm_object_attach_property(&connector->base,
 267                                    config->writeback_out_fence_ptr_property, 0);
 268
 269         drm_object_attach_property(&connector->base,
 270                                    config->writeback_fb_id_property, 0);
 271
 272         drm_object_attach_property(&connector->base,
 273                                    config->writeback_pixel_formats_property,
 274                                    blob->base.id);
 275         wb_connector->pixel_formats_blob_ptr = blob;
 276
 277         return 0;
 278
 279 attach_fail:
 280         drm_connector_cleanup(connector);
 281 connector_fail:
 282         drm_property_blob_put(blob);
 283         return ret;
 284 }
 285 EXPORT_SYMBOL(drm_writeback_connector_init_with_encoder);
 286
 287 int drm_writeback_set_fb(struct drm_connector_state *conn_state,
 288                          struct drm_framebuffer *fb)
 289 {
 290         WARN_ON(conn_state->connector->connector_type != DRM_MODE_CONNECTOR_WRITEBACK);
 291
 292         if (!conn_state->writeback_job) {
 293                 conn_state->writeback_job =
 294                         kzalloc(sizeof(*conn_state->writeback_job), GFP_KERNEL);
 295                 if (!conn_state->writeback_job)
 296                         return -ENOMEM;
 297
 298                 conn_state->writeback_job->connector =
 299                         drm_connector_to_writeback(conn_state->connector);
 300         }
 301
 302         drm_framebuffer_assign(&conn_state->writeback_job->fb, fb);
 303         return 0;
 304 }
 305
 306 int drm_writeback_prepare_job(struct drm_writeback_job *job)
 307 {
 308         struct drm_writeback_connector *connector = job->connector;
 309         const struct drm_connector_helper_funcs *funcs =
 310                 connector->base.helper_private;
 311         int ret;
 312
 313         if (funcs->prepare_writeback_job) {
 314                 ret = funcs->prepare_writeback_job(connector, job);
 315                 if (ret < 0)
 316                         return ret;
 317         }
 318
 319         job->prepared = true;
 320         return 0;
 321 }
 322 EXPORT_SYMBOL(drm_writeback_prepare_job);
 323
 324 /**
 325  * drm_writeback_queue_job - Queue a writeback job for later signalling
 326  * @wb_connector: The writeback connector to queue a job on
 327  * @conn_state: The connector state containing the job to queue
 328  *
 329  * This function adds the job contained in @conn_state to the job_queue for a
 330  * writeback connector. It takes ownership of the writeback job and sets the
 331  * @conn_state->writeback_job to NULL, and so no access to the job may be
 332  * performed by the caller after this function returns.
 333  *
 334  * Drivers must ensure that for a given writeback connector, jobs are queued in
 335  * exactly the same order as they will be completed by the hardware (and
 336  * signaled via drm_writeback_signal_completion).
 337  *
 338  * For every call to drm_writeback_queue_job() there must be exactly one call to
 339  * drm_writeback_signal_completion()
 340  *
 341  * See also: drm_writeback_signal_completion()
 342  */
 343 void drm_writeback_queue_job(struct drm_writeback_connector *wb_connector,
 344                              struct drm_connector_state *conn_state)
 345 {
 346         struct drm_writeback_job *job;
 347         unsigned long flags;
 348
 349         job = conn_state->writeback_job;
 350         conn_state->writeback_job = NULL;
 351
 352         spin_lock_irqsave(&wb_connector->job_lock, flags);
 353         list_add_tail(&job->list_entry, &wb_connector->job_queue);
 354         spin_unlock_irqrestore(&wb_connector->job_lock, flags);
 355 }
 356 EXPORT_SYMBOL(drm_writeback_queue_job);
 357
 358 void drm_writeback_cleanup_job(struct drm_writeback_job *job)
 359 {
 360         struct drm_writeback_connector *connector = job->connector;
 361         const struct drm_connector_helper_funcs *funcs =
 362                 connector->base.helper_private;
 363
 364         if (job->prepared && funcs->cleanup_writeback_job)
 365                 funcs->cleanup_writeback_job(connector, job);
 366
 367         if (job->fb)
 368                 drm_framebuffer_put(job->fb);
 369
 370         if (job->out_fence)
 371                 dma_fence_put(job->out_fence);
 372
 373         kfree(job);
 374 }
 375 EXPORT_SYMBOL(drm_writeback_cleanup_job);
 376
 377 /*
 378  * @cleanup_work: deferred cleanup of a writeback job
 379  *
 380  * The job cannot be cleaned up directly in drm_writeback_signal_completion,
 381  * because it may be called in interrupt context. Dropping the framebuffer
 382  * reference can sleep, and so the cleanup is deferred to a workqueue.
 383  */
 384 static void cleanup_work(struct work_struct *work)
 385 {
 386         struct drm_writeback_job *job = container_of(work,
 387                                                      struct drm_writeback_job,
 388                                                      cleanup_work);
 389
 390         drm_writeback_cleanup_job(job);
 391 }
 392
 393 /**
 394  * drm_writeback_signal_completion - Signal the completion of a writeback job
 395  * @wb_connector: The writeback connector whose job is complete
 396  * @status: Status code to set in the writeback out_fence (0 for success)
 397  *
 398  * Drivers should call this to signal the completion of a previously queued
 399  * writeback job. It should be called as soon as possible after the hardware
 400  * has finished writing, and may be called from interrupt context.
 401  * It is the driver's responsibility to ensure that for a given connector, the
 402  * hardware completes writeback jobs in the same order as they are queued.
 403  *
 404  * Unless the driver is holding its own reference to the framebuffer, it must
 405  * not be accessed after calling this function.
 406  *
 407  * See also: drm_writeback_queue_job()
 408  */
 409 void
 410 drm_writeback_signal_completion(struct drm_writeback_connector *wb_connector,
 411                                 int status)
 412 {
 413         unsigned long flags;
 414         struct drm_writeback_job *job;
 415         struct dma_fence *out_fence;
 416
 417         spin_lock_irqsave(&wb_connector->job_lock, flags);
 418         job = list_first_entry_or_null(&wb_connector->job_queue,
 419                                        struct drm_writeback_job,
 420                                        list_entry);
 421         if (job)
 422                 list_del(&job->list_entry);
 423
 424         spin_unlock_irqrestore(&wb_connector->job_lock, flags);
 425
 426         if (WARN_ON(!job))
 427                 return;
 428
 429         out_fence = job->out_fence;
 430         if (out_fence) {
 431                 if (status)
 432                         dma_fence_set_error(out_fence, status);
 433                 dma_fence_signal(out_fence);
 434                 dma_fence_put(out_fence);
 435                 job->out_fence = NULL;
 436         }
 437
 438         INIT_WORK(&job->cleanup_work, cleanup_work);
 439         queue_work(system_long_wq, &job->cleanup_work);
 440 }
 441 EXPORT_SYMBOL(drm_writeback_signal_completion);
 442
 443 struct dma_fence *
 444 drm_writeback_get_out_fence(struct drm_writeback_connector *wb_connector)
 445 {
 446         struct dma_fence *fence;
 447
 448         if (WARN_ON(wb_connector->base.connector_type !=
 449                     DRM_MODE_CONNECTOR_WRITEBACK))
 450                 return NULL;
 451
 452         fence = kzalloc(sizeof(*fence), GFP_KERNEL);
 453         if (!fence)
 454                 return NULL;
 455
 456         dma_fence_init(fence, &drm_writeback_fence_ops,
 457                        &wb_connector->fence_lock, wb_connector->fence_context,
 458                        ++wb_connector->fence_seqno);
 459
 460         return fence;
 461 }
 462 EXPORT_SYMBOL(drm_writeback_get_out_fence);