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_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 bool drm_writeback_fence_enable_signaling(struct dma_fence *fence)
 104 {
 105         return true;
 106 }
 107
 108 static const struct dma_fence_ops drm_writeback_fence_ops = {
 109         .get_driver_name = drm_writeback_fence_get_driver_name,
 110         .get_timeline_name = drm_writeback_fence_get_timeline_name,
 111         .enable_signaling = drm_writeback_fence_enable_signaling,
 112 };
 113
 114 static int create_writeback_properties(struct drm_device *dev)
 115 {
 116         struct drm_property *prop;
 117
 118         if (!dev->mode_config.writeback_fb_id_property) {
 119                 prop = drm_property_create_object(dev, DRM_MODE_PROP_ATOMIC,
 120                                                   "WRITEBACK_FB_ID",
 121                                                   DRM_MODE_OBJECT_FB);
 122                 if (!prop)
 123                         return -ENOMEM;
 124                 dev->mode_config.writeback_fb_id_property = prop;
 125         }
 126
 127         if (!dev->mode_config.writeback_pixel_formats_property) {
 128                 prop = drm_property_create(dev, DRM_MODE_PROP_BLOB |
 129                                            DRM_MODE_PROP_ATOMIC |
 130                                            DRM_MODE_PROP_IMMUTABLE,
 131                                            "WRITEBACK_PIXEL_FORMATS", 0);
 132                 if (!prop)
 133                         return -ENOMEM;
 134                 dev->mode_config.writeback_pixel_formats_property = prop;
 135         }
 136
 137         if (!dev->mode_config.writeback_out_fence_ptr_property) {
 138                 prop = drm_property_create_range(dev, DRM_MODE_PROP_ATOMIC,
 139                                                  "WRITEBACK_OUT_FENCE_PTR", 0,
 140                                                  U64_MAX);
 141                 if (!prop)
 142                         return -ENOMEM;
 143                 dev->mode_config.writeback_out_fence_ptr_property = prop;
 144         }
 145
 146         return 0;
 147 }
 148
 149 static const struct drm_encoder_funcs drm_writeback_encoder_funcs = {
 150         .destroy = drm_encoder_cleanup,
 151 };
 152
 153 /**
 154  * drm_writeback_connector_init - Initialize a writeback connector and its properties
 155  * @dev: DRM device
 156  * @wb_connector: Writeback connector to initialize
 157  * @con_funcs: Connector funcs vtable
 158  * @enc_helper_funcs: Encoder helper funcs vtable to be used by the internal encoder
 159  * @formats: Array of supported pixel formats for the writeback engine
 160  * @n_formats: Length of the formats array
 161  * @possible_crtcs: possible crtcs for the internal writeback encoder
 162  *
 163  * This function creates the writeback-connector-specific properties if they
 164  * have not been already created, initializes the connector as
 165  * type DRM_MODE_CONNECTOR_WRITEBACK, and correctly initializes the property
 166  * values. It will also create an internal encoder associated with the
 167  * drm_writeback_connector and set it to use the @enc_helper_funcs vtable for
 168  * the encoder helper.
 169  *
 170  * Drivers should always use this function instead of drm_connector_init() to
 171  * set up writeback connectors.
 172  *
 173  * Returns: 0 on success, or a negative error code
 174  */
 175 int drm_writeback_connector_init(struct drm_device *dev,
 176                                  struct drm_writeback_connector *wb_connector,
 177                                  const struct drm_connector_funcs *con_funcs,
 178                                  const struct drm_encoder_helper_funcs *enc_helper_funcs,
 179                                  const u32 *formats, int n_formats,
 180                                  u32 possible_crtcs)
 181 {
 182         int ret = 0;
 183
 184         drm_encoder_helper_add(&wb_connector->encoder, enc_helper_funcs);
 185
 186         wb_connector->encoder.possible_crtcs = possible_crtcs;
 187
 188         ret = drm_encoder_init(dev, &wb_connector->encoder,
 189                                &drm_writeback_encoder_funcs,
 190                                DRM_MODE_ENCODER_VIRTUAL, NULL);
 191         if (ret)
 192                 return ret;
 193
 194         ret = drm_writeback_connector_init_with_encoder(dev, wb_connector, &wb_connector->encoder,
 195                         con_funcs, formats, n_formats);
 196
 197         if (ret)
 198                 drm_encoder_cleanup(&wb_connector->encoder);
 199
 200         return ret;
 201 }
 202 EXPORT_SYMBOL(drm_writeback_connector_init);
 203
 204 /**
 205  * drm_writeback_connector_init_with_encoder - Initialize a writeback connector with
 206  * a custom encoder
 207  *
 208  * @dev: DRM device
 209  * @wb_connector: Writeback connector to initialize
 210  * @enc: handle to the already initialized drm encoder
 211  * @con_funcs: Connector funcs vtable
 212  * @formats: Array of supported pixel formats for the writeback engine
 213  * @n_formats: Length of the formats array
 214  *
 215  * This function creates the writeback-connector-specific properties if they
 216  * have not been already created, initializes the connector as
 217  * type DRM_MODE_CONNECTOR_WRITEBACK, and correctly initializes the property
 218  * values.
 219  *
 220  * This function assumes that the drm_writeback_connector's encoder has already been
 221  * created and initialized before invoking this function.
 222  *
 223  * In addition, this function also assumes that callers of this API will manage
 224  * assigning the encoder helper functions, possible_crtcs and any other encoder
 225  * specific operation.
 226  *
 227  * Drivers should always use this function instead of drm_connector_init() to
 228  * set up writeback connectors if they want to manage themselves the lifetime of the
 229  * associated encoder.
 230  *
 231  * Returns: 0 on success, or a negative error code
 232  */
 233 int drm_writeback_connector_init_with_encoder(struct drm_device *dev,
 234                 struct drm_writeback_connector *wb_connector, struct drm_encoder *enc,
 235                 const struct drm_connector_funcs *con_funcs, const u32 *formats,
 236                 int n_formats)
 237 {
 238         struct drm_property_blob *blob;
 239         struct drm_connector *connector = &wb_connector->base;
 240         struct drm_mode_config *config = &dev->mode_config;
 241         int ret = create_writeback_properties(dev);
 242
 243         if (ret != 0)
 244                 return ret;
 245
 246         blob = drm_property_create_blob(dev, n_formats * sizeof(*formats),
 247                                         formats);
 248         if (IS_ERR(blob))
 249                 return PTR_ERR(blob);
 250
 251
 252         connector->interlace_allowed = 0;
 253
 254         ret = drm_connector_init(dev, connector, con_funcs,
 255                                  DRM_MODE_CONNECTOR_WRITEBACK);
 256         if (ret)
 257                 goto connector_fail;
 258
 259         ret = drm_connector_attach_encoder(connector, enc);
 260         if (ret)
 261                 goto attach_fail;
 262
 263         INIT_LIST_HEAD(&wb_connector->job_queue);
 264         spin_lock_init(&wb_connector->job_lock);
 265
 266         wb_connector->fence_context = dma_fence_context_alloc(1);
 267         spin_lock_init(&wb_connector->fence_lock);
 268         snprintf(wb_connector->timeline_name,
 269                  sizeof(wb_connector->timeline_name),
 270                  "CONNECTOR:%d-%s", connector->base.id, connector->name);
 271
 272         drm_object_attach_property(&connector->base,
 273                                    config->writeback_out_fence_ptr_property, 0);
 274
 275         drm_object_attach_property(&connector->base,
 276                                    config->writeback_fb_id_property, 0);
 277
 278         drm_object_attach_property(&connector->base,
 279                                    config->writeback_pixel_formats_property,
 280                                    blob->base.id);
 281         wb_connector->pixel_formats_blob_ptr = blob;
 282
 283         return 0;
 284
 285 attach_fail:
 286         drm_connector_cleanup(connector);
 287 connector_fail:
 288         drm_property_blob_put(blob);
 289         return ret;
 290 }
 291 EXPORT_SYMBOL(drm_writeback_connector_init_with_encoder);
 292
 293 int drm_writeback_set_fb(struct drm_connector_state *conn_state,
 294                          struct drm_framebuffer *fb)
 295 {
 296         WARN_ON(conn_state->connector->connector_type != DRM_MODE_CONNECTOR_WRITEBACK);
 297
 298         if (!conn_state->writeback_job) {
 299                 conn_state->writeback_job =
 300                         kzalloc(sizeof(*conn_state->writeback_job), GFP_KERNEL);
 301                 if (!conn_state->writeback_job)
 302                         return -ENOMEM;
 303
 304                 conn_state->writeback_job->connector =
 305                         drm_connector_to_writeback(conn_state->connector);
 306         }
 307
 308         drm_framebuffer_assign(&conn_state->writeback_job->fb, fb);
 309         return 0;
 310 }
 311
 312 int drm_writeback_prepare_job(struct drm_writeback_job *job)
 313 {
 314         struct drm_writeback_connector *connector = job->connector;
 315         const struct drm_connector_helper_funcs *funcs =
 316                 connector->base.helper_private;
 317         int ret;
 318
 319         if (funcs->prepare_writeback_job) {
 320                 ret = funcs->prepare_writeback_job(connector, job);
 321                 if (ret < 0)
 322                         return ret;
 323         }
 324
 325         job->prepared = true;
 326         return 0;
 327 }
 328 EXPORT_SYMBOL(drm_writeback_prepare_job);
 329
 330 /**
 331  * drm_writeback_queue_job - Queue a writeback job for later signalling
 332  * @wb_connector: The writeback connector to queue a job on
 333  * @conn_state: The connector state containing the job to queue
 334  *
 335  * This function adds the job contained in @conn_state to the job_queue for a
 336  * writeback connector. It takes ownership of the writeback job and sets the
 337  * @conn_state->writeback_job to NULL, and so no access to the job may be
 338  * performed by the caller after this function returns.
 339  *
 340  * Drivers must ensure that for a given writeback connector, jobs are queued in
 341  * exactly the same order as they will be completed by the hardware (and
 342  * signaled via drm_writeback_signal_completion).
 343  *
 344  * For every call to drm_writeback_queue_job() there must be exactly one call to
 345  * drm_writeback_signal_completion()
 346  *
 347  * See also: drm_writeback_signal_completion()
 348  */
 349 void drm_writeback_queue_job(struct drm_writeback_connector *wb_connector,
 350                              struct drm_connector_state *conn_state)
 351 {
 352         struct drm_writeback_job *job;
 353         unsigned long flags;
 354
 355         job = conn_state->writeback_job;
 356         conn_state->writeback_job = NULL;
 357
 358         spin_lock_irqsave(&wb_connector->job_lock, flags);
 359         list_add_tail(&job->list_entry, &wb_connector->job_queue);
 360         spin_unlock_irqrestore(&wb_connector->job_lock, flags);
 361 }
 362 EXPORT_SYMBOL(drm_writeback_queue_job);
 363
 364 void drm_writeback_cleanup_job(struct drm_writeback_job *job)
 365 {
 366         struct drm_writeback_connector *connector = job->connector;
 367         const struct drm_connector_helper_funcs *funcs =
 368                 connector->base.helper_private;
 369
 370         if (job->prepared && funcs->cleanup_writeback_job)
 371                 funcs->cleanup_writeback_job(connector, job);
 372
 373         if (job->fb)
 374                 drm_framebuffer_put(job->fb);
 375
 376         if (job->out_fence)
 377                 dma_fence_put(job->out_fence);
 378
 379         kfree(job);
 380 }
 381 EXPORT_SYMBOL(drm_writeback_cleanup_job);
 382
 383 /*
 384  * @cleanup_work: deferred cleanup of a writeback job
 385  *
 386  * The job cannot be cleaned up directly in drm_writeback_signal_completion,
 387  * because it may be called in interrupt context. Dropping the framebuffer
 388  * reference can sleep, and so the cleanup is deferred to a workqueue.
 389  */
 390 static void cleanup_work(struct work_struct *work)
 391 {
 392         struct drm_writeback_job *job = container_of(work,
 393                                                      struct drm_writeback_job,
 394                                                      cleanup_work);
 395
 396         drm_writeback_cleanup_job(job);
 397 }
 398
 399 /**
 400  * drm_writeback_signal_completion - Signal the completion of a writeback job
 401  * @wb_connector: The writeback connector whose job is complete
 402  * @status: Status code to set in the writeback out_fence (0 for success)
 403  *
 404  * Drivers should call this to signal the completion of a previously queued
 405  * writeback job. It should be called as soon as possible after the hardware
 406  * has finished writing, and may be called from interrupt context.
 407  * It is the driver's responsibility to ensure that for a given connector, the
 408  * hardware completes writeback jobs in the same order as they are queued.
 409  *
 410  * Unless the driver is holding its own reference to the framebuffer, it must
 411  * not be accessed after calling this function.
 412  *
 413  * See also: drm_writeback_queue_job()
 414  */
 415 void
 416 drm_writeback_signal_completion(struct drm_writeback_connector *wb_connector,
 417                                 int status)
 418 {
 419         unsigned long flags;
 420         struct drm_writeback_job *job;
 421         struct dma_fence *out_fence;
 422
 423         spin_lock_irqsave(&wb_connector->job_lock, flags);
 424         job = list_first_entry_or_null(&wb_connector->job_queue,
 425                                        struct drm_writeback_job,
 426                                        list_entry);
 427         if (job)
 428                 list_del(&job->list_entry);
 429
 430         spin_unlock_irqrestore(&wb_connector->job_lock, flags);
 431
 432         if (WARN_ON(!job))
 433                 return;
 434
 435         out_fence = job->out_fence;
 436         if (out_fence) {
 437                 if (status)
 438                         dma_fence_set_error(out_fence, status);
 439                 dma_fence_signal(out_fence);
 440                 dma_fence_put(out_fence);
 441                 job->out_fence = NULL;
 442         }
 443
 444         INIT_WORK(&job->cleanup_work, cleanup_work);
 445         queue_work(system_long_wq, &job->cleanup_work);
 446 }
 447 EXPORT_SYMBOL(drm_writeback_signal_completion);
 448
 449 struct dma_fence *
 450 drm_writeback_get_out_fence(struct drm_writeback_connector *wb_connector)
 451 {
 452         struct dma_fence *fence;
 453
 454         if (WARN_ON(wb_connector->base.connector_type !=
 455                     DRM_MODE_CONNECTOR_WRITEBACK))
 456                 return NULL;
 457
 458         fence = kzalloc(sizeof(*fence), GFP_KERNEL);
 459         if (!fence)
 460                 return NULL;
 461
 462         dma_fence_init(fence, &drm_writeback_fence_ops,
 463                        &wb_connector->fence_lock, wb_connector->fence_context,
 464                        ++wb_connector->fence_seqno);
 465
 466         return fence;
 467 }
 468 EXPORT_SYMBOL(drm_writeback_get_out_fence);