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 <brian.starkey@arm.com>
   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_modeset_helper_vtables.h>
  18 #include <drm/drm_property.h>
  19 #include <drm/drm_writeback.h>
  20
  21 /**
  22  * DOC: overview
  23  *
  24  * Writeback connectors are used to expose hardware which can write the output
  25  * from a CRTC to a memory buffer. They are used and act similarly to other
  26  * types of connectors, with some important differences:
  27  *
  28  * * Writeback connectors don't provide a way to output visually to the user.
  29  *
  30  * * Writeback connectors are visible to userspace only when the client sets
  31  *   DRM_CLIENT_CAP_WRITEBACK_CONNECTORS.
  32  *
  33  * * Writeback connectors don't have EDID.
  34  *
  35  * A framebuffer may only be attached to a writeback connector when the
  36  * connector is attached to a CRTC. The WRITEBACK_FB_ID property which sets the
  37  * framebuffer applies only to a single commit (see below). A framebuffer may
  38  * not be attached while the CRTC is off.
  39  *
  40  * Unlike with planes, when a writeback framebuffer is removed by userspace DRM
  41  * makes no attempt to remove it from active use by the connector. This is
  42  * because no method is provided to abort a writeback operation, and in any
  43  * case making a new commit whilst a writeback is ongoing is undefined (see
  44  * WRITEBACK_OUT_FENCE_PTR below). As soon as the current writeback is finished,
  45  * the framebuffer will automatically no longer be in active use. As it will
  46  * also have already been removed from the framebuffer list, there will be no
  47  * way for any userspace application to retrieve a reference to it in the
  48  * intervening period.
  49  *
  50  * Writeback connectors have some additional properties, which userspace
  51  * can use to query and control them:
  52  *
  53  *  "WRITEBACK_FB_ID":
  54  *      Write-only object property storing a DRM_MODE_OBJECT_FB: it stores the
  55  *      framebuffer to be written by the writeback connector. This property is
  56  *      similar to the FB_ID property on planes, but will always read as zero
  57  *      and is not preserved across commits.
  58  *      Userspace must set this property to an output buffer every time it
  59  *      wishes the buffer to get filled.
  60  *
  61  *  "WRITEBACK_PIXEL_FORMATS":
  62  *      Immutable blob property to store the supported pixel formats table. The
  63  *      data is an array of u32 DRM_FORMAT_* fourcc values.
  64  *      Userspace can use this blob to find out what pixel formats are supported
  65  *      by the connector's writeback engine.
  66  *
  67  *  "WRITEBACK_OUT_FENCE_PTR":
  68  *      Userspace can use this property to provide a pointer for the kernel to
  69  *      fill with a sync_file file descriptor, which will signal once the
  70  *      writeback is finished. The value should be the address of a 32-bit
  71  *      signed integer, cast to a u64.
  72  *      Userspace should wait for this fence to signal before making another
  73  *      commit affecting any of the same CRTCs, Planes or Connectors.
  74  *      **Failure to do so will result in undefined behaviour.**
  75  *      For this reason it is strongly recommended that all userspace
  76  *      applications making use of writeback connectors *always* retrieve an
  77  *      out-fence for the commit and use it appropriately.
  78  *      From userspace, this property will always read as zero.
  79  */
  80
  81 #define fence_to_wb_connector(x) container_of(x->lock, \
  82                                               struct drm_writeback_connector, \
  83                                               fence_lock)
  84
  85 static const char *drm_writeback_fence_get_driver_name(struct dma_fence *fence)
  86 {
  87         struct drm_writeback_connector *wb_connector =
  88                 fence_to_wb_connector(fence);
  89
  90         return wb_connector->base.dev->driver->name;
  91 }
  92
  93 static const char *
  94 drm_writeback_fence_get_timeline_name(struct dma_fence *fence)
  95 {
  96         struct drm_writeback_connector *wb_connector =
  97                 fence_to_wb_connector(fence);
  98
  99         return wb_connector->timeline_name;
 100 }
 101
 102 static bool drm_writeback_fence_enable_signaling(struct dma_fence *fence)
 103 {
 104         return true;
 105 }
 106
 107 static const struct dma_fence_ops drm_writeback_fence_ops = {
 108         .get_driver_name = drm_writeback_fence_get_driver_name,
 109         .get_timeline_name = drm_writeback_fence_get_timeline_name,
 110         .enable_signaling = drm_writeback_fence_enable_signaling,
 111 };
 112
 113 static int create_writeback_properties(struct drm_device *dev)
 114 {
 115         struct drm_property *prop;
 116
 117         if (!dev->mode_config.writeback_fb_id_property) {
 118                 prop = drm_property_create_object(dev, DRM_MODE_PROP_ATOMIC,
 119                                                   "WRITEBACK_FB_ID",
 120                                                   DRM_MODE_OBJECT_FB);
 121                 if (!prop)
 122                         return -ENOMEM;
 123                 dev->mode_config.writeback_fb_id_property = prop;
 124         }
 125
 126         if (!dev->mode_config.writeback_pixel_formats_property) {
 127                 prop = drm_property_create(dev, DRM_MODE_PROP_BLOB |
 128                                            DRM_MODE_PROP_ATOMIC |
 129                                            DRM_MODE_PROP_IMMUTABLE,
 130                                            "WRITEBACK_PIXEL_FORMATS", 0);
 131                 if (!prop)
 132                         return -ENOMEM;
 133                 dev->mode_config.writeback_pixel_formats_property = prop;
 134         }
 135
 136         if (!dev->mode_config.writeback_out_fence_ptr_property) {
 137                 prop = drm_property_create_range(dev, DRM_MODE_PROP_ATOMIC,
 138                                                  "WRITEBACK_OUT_FENCE_PTR", 0,
 139                                                  U64_MAX);
 140                 if (!prop)
 141                         return -ENOMEM;
 142                 dev->mode_config.writeback_out_fence_ptr_property = prop;
 143         }
 144
 145         return 0;
 146 }
 147
 148 static const struct drm_encoder_funcs drm_writeback_encoder_funcs = {
 149         .destroy = drm_encoder_cleanup,
 150 };
 151
 152 /**
 153  * drm_writeback_connector_init - Initialize a writeback connector and its properties
 154  * @dev: DRM device
 155  * @wb_connector: Writeback connector to initialize
 156  * @con_funcs: Connector funcs vtable
 157  * @enc_helper_funcs: Encoder helper funcs vtable to be used by the internal encoder
 158  * @formats: Array of supported pixel formats for the writeback engine
 159  * @n_formats: Length of the formats array
 160  * @possible_crtcs: possible crtcs for the internal writeback encoder
 161  *
 162  * This function creates the writeback-connector-specific properties if they
 163  * have not been already created, initializes the connector as
 164  * type DRM_MODE_CONNECTOR_WRITEBACK, and correctly initializes the property
 165  * values. It will also create an internal encoder associated with the
 166  * drm_writeback_connector and set it to use the @enc_helper_funcs vtable for
 167  * the encoder helper.
 168  *
 169  * Drivers should always use this function instead of drm_connector_init() to
 170  * set up writeback connectors.
 171  *
 172  * Returns: 0 on success, or a negative error code
 173  */
 174 int drm_writeback_connector_init(struct drm_device *dev,
 175                                  struct drm_writeback_connector *wb_connector,
 176                                  const struct drm_connector_funcs *con_funcs,
 177                                  const struct drm_encoder_helper_funcs *enc_helper_funcs,
 178                                  const u32 *formats, int n_formats,
 179                                  u32 possible_crtcs)
 180 {
 181         int ret = 0;
 182
 183         drm_encoder_helper_add(&wb_connector->encoder, enc_helper_funcs);
 184
 185         wb_connector->encoder.possible_crtcs = possible_crtcs;
 186
 187         ret = drm_encoder_init(dev, &wb_connector->encoder,
 188                                &drm_writeback_encoder_funcs,
 189                                DRM_MODE_ENCODER_VIRTUAL, NULL);
 190         if (ret)
 191                 return ret;
 192
 193         ret = drm_writeback_connector_init_with_encoder(dev, wb_connector, &wb_connector->encoder,
 194                         con_funcs, formats, n_formats);
 195
 196         if (ret)
 197                 drm_encoder_cleanup(&wb_connector->encoder);
 198
 199         return ret;
 200 }
 201 EXPORT_SYMBOL(drm_writeback_connector_init);
 202
 203 /**
 204  * drm_writeback_connector_init_with_encoder - Initialize a writeback connector with
 205  * a custom encoder
 206  *
 207  * @dev: DRM device
 208  * @wb_connector: Writeback connector to initialize
 209  * @enc: handle to the already initialized drm encoder
 210  * @con_funcs: Connector funcs vtable
 211  * @formats: Array of supported pixel formats for the writeback engine
 212  * @n_formats: Length of the formats array
 213  *
 214  * This function creates the writeback-connector-specific properties if they
 215  * have not been already created, initializes the connector as
 216  * type DRM_MODE_CONNECTOR_WRITEBACK, and correctly initializes the property
 217  * values.
 218  *
 219  * This function assumes that the drm_writeback_connector's encoder has already been
 220  * created and initialized before invoking this function.
 221  *
 222  * In addition, this function also assumes that callers of this API will manage
 223  * assigning the encoder helper functions, possible_crtcs and any other encoder
 224  * specific operation.
 225  *
 226  * Drivers should always use this function instead of drm_connector_init() to
 227  * set up writeback connectors if they want to manage themselves the lifetime of the
 228  * associated encoder.
 229  *
 230  * Returns: 0 on success, or a negative error code
 231  */
 232 int drm_writeback_connector_init_with_encoder(struct drm_device *dev,
 233                 struct drm_writeback_connector *wb_connector, struct drm_encoder *enc,
 234                 const struct drm_connector_funcs *con_funcs, const u32 *formats,
 235                 int n_formats)
 236 {
 237         struct drm_property_blob *blob;
 238         struct drm_connector *connector = &wb_connector->base;
 239         struct drm_mode_config *config = &dev->mode_config;
 240         int ret = create_writeback_properties(dev);
 241
 242         if (ret != 0)
 243                 return ret;
 244
 245         blob = drm_property_create_blob(dev, n_formats * sizeof(*formats),
 246                                         formats);
 247         if (IS_ERR(blob))
 248                 return PTR_ERR(blob);
 249
 250
 251         connector->interlace_allowed = 0;
 252
 253         ret = drm_connector_init(dev, connector, con_funcs,
 254                                  DRM_MODE_CONNECTOR_WRITEBACK);
 255         if (ret)
 256                 goto connector_fail;
 257
 258         ret = drm_connector_attach_encoder(connector, enc);
 259         if (ret)
 260                 goto attach_fail;
 261
 262         INIT_LIST_HEAD(&wb_connector->job_queue);
 263         spin_lock_init(&wb_connector->job_lock);
 264
 265         wb_connector->fence_context = dma_fence_context_alloc(1);
 266         spin_lock_init(&wb_connector->fence_lock);
 267         snprintf(wb_connector->timeline_name,
 268                  sizeof(wb_connector->timeline_name),
 269                  "CONNECTOR:%d-%s", connector->base.id, connector->name);
 270
 271         drm_object_attach_property(&connector->base,
 272                                    config->writeback_out_fence_ptr_property, 0);
 273
 274         drm_object_attach_property(&connector->base,
 275                                    config->writeback_fb_id_property, 0);
 276
 277         drm_object_attach_property(&connector->base,
 278                                    config->writeback_pixel_formats_property,
 279                                    blob->base.id);
 280         wb_connector->pixel_formats_blob_ptr = blob;
 281
 282         return 0;
 283
 284 attach_fail:
 285         drm_connector_cleanup(connector);
 286 connector_fail:
 287         drm_property_blob_put(blob);
 288         return ret;
 289 }
 290 EXPORT_SYMBOL(drm_writeback_connector_init_with_encoder);
 291
 292 int drm_writeback_set_fb(struct drm_connector_state *conn_state,
 293                          struct drm_framebuffer *fb)
 294 {
 295         WARN_ON(conn_state->connector->connector_type != DRM_MODE_CONNECTOR_WRITEBACK);
 296
 297         if (!conn_state->writeback_job) {
 298                 conn_state->writeback_job =
 299                         kzalloc(sizeof(*conn_state->writeback_job), GFP_KERNEL);
 300                 if (!conn_state->writeback_job)
 301                         return -ENOMEM;
 302
 303                 conn_state->writeback_job->connector =
 304                         drm_connector_to_writeback(conn_state->connector);
 305         }
 306
 307         drm_framebuffer_assign(&conn_state->writeback_job->fb, fb);
 308         return 0;
 309 }
 310
 311 int drm_writeback_prepare_job(struct drm_writeback_job *job)
 312 {
 313         struct drm_writeback_connector *connector = job->connector;
 314         const struct drm_connector_helper_funcs *funcs =
 315                 connector->base.helper_private;
 316         int ret;
 317
 318         if (funcs->prepare_writeback_job) {
 319                 ret = funcs->prepare_writeback_job(connector, job);
 320                 if (ret < 0)
 321                         return ret;
 322         }
 323
 324         job->prepared = true;
 325         return 0;
 326 }
 327 EXPORT_SYMBOL(drm_writeback_prepare_job);
 328
 329 /**
 330  * drm_writeback_queue_job - Queue a writeback job for later signalling
 331  * @wb_connector: The writeback connector to queue a job on
 332  * @conn_state: The connector state containing the job to queue
 333  *
 334  * This function adds the job contained in @conn_state to the job_queue for a
 335  * writeback connector. It takes ownership of the writeback job and sets the
 336  * @conn_state->writeback_job to NULL, and so no access to the job may be
 337  * performed by the caller after this function returns.
 338  *
 339  * Drivers must ensure that for a given writeback connector, jobs are queued in
 340  * exactly the same order as they will be completed by the hardware (and
 341  * signaled via drm_writeback_signal_completion).
 342  *
 343  * For every call to drm_writeback_queue_job() there must be exactly one call to
 344  * drm_writeback_signal_completion()
 345  *
 346  * See also: drm_writeback_signal_completion()
 347  */
 348 void drm_writeback_queue_job(struct drm_writeback_connector *wb_connector,
 349                              struct drm_connector_state *conn_state)
 350 {
 351         struct drm_writeback_job *job;
 352         unsigned long flags;
 353
 354         job = conn_state->writeback_job;
 355         conn_state->writeback_job = NULL;
 356
 357         spin_lock_irqsave(&wb_connector->job_lock, flags);
 358         list_add_tail(&job->list_entry, &wb_connector->job_queue);
 359         spin_unlock_irqrestore(&wb_connector->job_lock, flags);
 360 }
 361 EXPORT_SYMBOL(drm_writeback_queue_job);
 362
 363 void drm_writeback_cleanup_job(struct drm_writeback_job *job)
 364 {
 365         struct drm_writeback_connector *connector = job->connector;
 366         const struct drm_connector_helper_funcs *funcs =
 367                 connector->base.helper_private;
 368
 369         if (job->prepared && funcs->cleanup_writeback_job)
 370                 funcs->cleanup_writeback_job(connector, job);
 371
 372         if (job->fb)
 373                 drm_framebuffer_put(job->fb);
 374
 375         if (job->out_fence)
 376                 dma_fence_put(job->out_fence);
 377
 378         kfree(job);
 379 }
 380 EXPORT_SYMBOL(drm_writeback_cleanup_job);
 381
 382 /*
 383  * @cleanup_work: deferred cleanup of a writeback job
 384  *
 385  * The job cannot be cleaned up directly in drm_writeback_signal_completion,
 386  * because it may be called in interrupt context. Dropping the framebuffer
 387  * reference can sleep, and so the cleanup is deferred to a workqueue.
 388  */
 389 static void cleanup_work(struct work_struct *work)
 390 {
 391         struct drm_writeback_job *job = container_of(work,
 392                                                      struct drm_writeback_job,
 393                                                      cleanup_work);
 394
 395         drm_writeback_cleanup_job(job);
 396 }
 397
 398 /**
 399  * drm_writeback_signal_completion - Signal the completion of a writeback job
 400  * @wb_connector: The writeback connector whose job is complete
 401  * @status: Status code to set in the writeback out_fence (0 for success)
 402  *
 403  * Drivers should call this to signal the completion of a previously queued
 404  * writeback job. It should be called as soon as possible after the hardware
 405  * has finished writing, and may be called from interrupt context.
 406  * It is the driver's responsibility to ensure that for a given connector, the
 407  * hardware completes writeback jobs in the same order as they are queued.
 408  *
 409  * Unless the driver is holding its own reference to the framebuffer, it must
 410  * not be accessed after calling this function.
 411  *
 412  * See also: drm_writeback_queue_job()
 413  */
 414 void
 415 drm_writeback_signal_completion(struct drm_writeback_connector *wb_connector,
 416                                 int status)
 417 {
 418         unsigned long flags;
 419         struct drm_writeback_job *job;
 420         struct dma_fence *out_fence;
 421
 422         spin_lock_irqsave(&wb_connector->job_lock, flags);
 423         job = list_first_entry_or_null(&wb_connector->job_queue,
 424                                        struct drm_writeback_job,
 425                                        list_entry);
 426         if (job)
 427                 list_del(&job->list_entry);
 428
 429         spin_unlock_irqrestore(&wb_connector->job_lock, flags);
 430
 431         if (WARN_ON(!job))
 432                 return;
 433
 434         out_fence = job->out_fence;
 435         if (out_fence) {
 436                 if (status)
 437                         dma_fence_set_error(out_fence, status);
 438                 dma_fence_signal(out_fence);
 439                 dma_fence_put(out_fence);
 440                 job->out_fence = NULL;
 441         }
 442
 443         INIT_WORK(&job->cleanup_work, cleanup_work);
 444         queue_work(system_long_wq, &job->cleanup_work);
 445 }
 446 EXPORT_SYMBOL(drm_writeback_signal_completion);
 447
 448 struct dma_fence *
 449 drm_writeback_get_out_fence(struct drm_writeback_connector *wb_connector)
 450 {
 451         struct dma_fence *fence;
 452
 453         if (WARN_ON(wb_connector->base.connector_type !=
 454                     DRM_MODE_CONNECTOR_WRITEBACK))
 455                 return NULL;
 456
 457         fence = kzalloc(sizeof(*fence), GFP_KERNEL);
 458         if (!fence)
 459                 return NULL;
 460
 461         dma_fence_init(fence, &drm_writeback_fence_ops,
 462                        &wb_connector->fence_lock, wb_connector->fence_context,
 463                        ++wb_connector->fence_seqno);
 464
 465         return fence;
 466 }
 467 EXPORT_SYMBOL(drm_writeback_get_out_fence);