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  *
 161  * This function creates the writeback-connector-specific properties if they
 162  * have not been already created, initializes the connector as
 163  * type DRM_MODE_CONNECTOR_WRITEBACK, and correctly initializes the property
 164  * values. It will also create an internal encoder associated with the
 165  * drm_writeback_connector and set it to use the @enc_helper_funcs vtable for
 166  * the encoder helper.
 167  *
 168  * Drivers should always use this function instead of drm_connector_init() to
 169  * set up writeback connectors.
 170  *
 171  * Returns: 0 on success, or a negative error code
 172  */
 173 int drm_writeback_connector_init(struct drm_device *dev,
 174                                  struct drm_writeback_connector *wb_connector,
 175                                  const struct drm_connector_funcs *con_funcs,
 176                                  const struct drm_encoder_helper_funcs *enc_helper_funcs,
 177                                  const u32 *formats, int n_formats)
 178 {
 179         struct drm_property_blob *blob;
 180         struct drm_connector *connector = &wb_connector->base;
 181         struct drm_mode_config *config = &dev->mode_config;
 182         int ret = create_writeback_properties(dev);
 183
 184         if (ret != 0)
 185                 return ret;
 186
 187         blob = drm_property_create_blob(dev, n_formats * sizeof(*formats),
 188                                         formats);
 189         if (IS_ERR(blob))
 190                 return PTR_ERR(blob);
 191
 192         drm_encoder_helper_add(&wb_connector->encoder, enc_helper_funcs);
 193         ret = drm_encoder_init(dev, &wb_connector->encoder,
 194                                &drm_writeback_encoder_funcs,
 195                                DRM_MODE_ENCODER_VIRTUAL, NULL);
 196         if (ret)
 197                 goto fail;
 198
 199         connector->interlace_allowed = 0;
 200
 201         ret = drm_connector_init(dev, connector, con_funcs,
 202                                  DRM_MODE_CONNECTOR_WRITEBACK);
 203         if (ret)
 204                 goto connector_fail;
 205
 206         ret = drm_connector_attach_encoder(connector,
 207                                                 &wb_connector->encoder);
 208         if (ret)
 209                 goto attach_fail;
 210
 211         INIT_LIST_HEAD(&wb_connector->job_queue);
 212         spin_lock_init(&wb_connector->job_lock);
 213
 214         wb_connector->fence_context = dma_fence_context_alloc(1);
 215         spin_lock_init(&wb_connector->fence_lock);
 216         snprintf(wb_connector->timeline_name,
 217                  sizeof(wb_connector->timeline_name),
 218                  "CONNECTOR:%d-%s", connector->base.id, connector->name);
 219
 220         drm_object_attach_property(&connector->base,
 221                                    config->writeback_out_fence_ptr_property, 0);
 222
 223         drm_object_attach_property(&connector->base,
 224                                    config->writeback_fb_id_property, 0);
 225
 226         drm_object_attach_property(&connector->base,
 227                                    config->writeback_pixel_formats_property,
 228                                    blob->base.id);
 229         wb_connector->pixel_formats_blob_ptr = blob;
 230
 231         return 0;
 232
 233 attach_fail:
 234         drm_connector_cleanup(connector);
 235 connector_fail:
 236         drm_encoder_cleanup(&wb_connector->encoder);
 237 fail:
 238         drm_property_blob_put(blob);
 239         return ret;
 240 }
 241 EXPORT_SYMBOL(drm_writeback_connector_init);
 242
 243 int drm_writeback_set_fb(struct drm_connector_state *conn_state,
 244                          struct drm_framebuffer *fb)
 245 {
 246         WARN_ON(conn_state->connector->connector_type != DRM_MODE_CONNECTOR_WRITEBACK);
 247
 248         if (!conn_state->writeback_job) {
 249                 conn_state->writeback_job =
 250                         kzalloc(sizeof(*conn_state->writeback_job), GFP_KERNEL);
 251                 if (!conn_state->writeback_job)
 252                         return -ENOMEM;
 253
 254                 conn_state->writeback_job->connector =
 255                         drm_connector_to_writeback(conn_state->connector);
 256         }
 257
 258         drm_framebuffer_assign(&conn_state->writeback_job->fb, fb);
 259         return 0;
 260 }
 261
 262 int drm_writeback_prepare_job(struct drm_writeback_job *job)
 263 {
 264         struct drm_writeback_connector *connector = job->connector;
 265         const struct drm_connector_helper_funcs *funcs =
 266                 connector->base.helper_private;
 267         int ret;
 268
 269         if (funcs->prepare_writeback_job) {
 270                 ret = funcs->prepare_writeback_job(connector, job);
 271                 if (ret < 0)
 272                         return ret;
 273         }
 274
 275         job->prepared = true;
 276         return 0;
 277 }
 278 EXPORT_SYMBOL(drm_writeback_prepare_job);
 279
 280 /**
 281  * drm_writeback_queue_job - Queue a writeback job for later signalling
 282  * @wb_connector: The writeback connector to queue a job on
 283  * @conn_state: The connector state containing the job to queue
 284  *
 285  * This function adds the job contained in @conn_state to the job_queue for a
 286  * writeback connector. It takes ownership of the writeback job and sets the
 287  * @conn_state->writeback_job to NULL, and so no access to the job may be
 288  * performed by the caller after this function returns.
 289  *
 290  * Drivers must ensure that for a given writeback connector, jobs are queued in
 291  * exactly the same order as they will be completed by the hardware (and
 292  * signaled via drm_writeback_signal_completion).
 293  *
 294  * For every call to drm_writeback_queue_job() there must be exactly one call to
 295  * drm_writeback_signal_completion()
 296  *
 297  * See also: drm_writeback_signal_completion()
 298  */
 299 void drm_writeback_queue_job(struct drm_writeback_connector *wb_connector,
 300                              struct drm_connector_state *conn_state)
 301 {
 302         struct drm_writeback_job *job;
 303         unsigned long flags;
 304
 305         job = conn_state->writeback_job;
 306         conn_state->writeback_job = NULL;
 307
 308         spin_lock_irqsave(&wb_connector->job_lock, flags);
 309         list_add_tail(&job->list_entry, &wb_connector->job_queue);
 310         spin_unlock_irqrestore(&wb_connector->job_lock, flags);
 311 }
 312 EXPORT_SYMBOL(drm_writeback_queue_job);
 313
 314 void drm_writeback_cleanup_job(struct drm_writeback_job *job)
 315 {
 316         struct drm_writeback_connector *connector = job->connector;
 317         const struct drm_connector_helper_funcs *funcs =
 318                 connector->base.helper_private;
 319
 320         if (job->prepared && funcs->cleanup_writeback_job)
 321                 funcs->cleanup_writeback_job(connector, job);
 322
 323         if (job->fb)
 324                 drm_framebuffer_put(job->fb);
 325
 326         if (job->out_fence)
 327                 dma_fence_put(job->out_fence);
 328
 329         kfree(job);
 330 }
 331 EXPORT_SYMBOL(drm_writeback_cleanup_job);
 332
 333 /*
 334  * @cleanup_work: deferred cleanup of a writeback job
 335  *
 336  * The job cannot be cleaned up directly in drm_writeback_signal_completion,
 337  * because it may be called in interrupt context. Dropping the framebuffer
 338  * reference can sleep, and so the cleanup is deferred to a workqueue.
 339  */
 340 static void cleanup_work(struct work_struct *work)
 341 {
 342         struct drm_writeback_job *job = container_of(work,
 343                                                      struct drm_writeback_job,
 344                                                      cleanup_work);
 345
 346         drm_writeback_cleanup_job(job);
 347 }
 348
 349 /**
 350  * drm_writeback_signal_completion - Signal the completion of a writeback job
 351  * @wb_connector: The writeback connector whose job is complete
 352  * @status: Status code to set in the writeback out_fence (0 for success)
 353  *
 354  * Drivers should call this to signal the completion of a previously queued
 355  * writeback job. It should be called as soon as possible after the hardware
 356  * has finished writing, and may be called from interrupt context.
 357  * It is the driver's responsibility to ensure that for a given connector, the
 358  * hardware completes writeback jobs in the same order as they are queued.
 359  *
 360  * Unless the driver is holding its own reference to the framebuffer, it must
 361  * not be accessed after calling this function.
 362  *
 363  * See also: drm_writeback_queue_job()
 364  */
 365 void
 366 drm_writeback_signal_completion(struct drm_writeback_connector *wb_connector,
 367                                 int status)
 368 {
 369         unsigned long flags;
 370         struct drm_writeback_job *job;
 371         struct dma_fence *out_fence;
 372
 373         spin_lock_irqsave(&wb_connector->job_lock, flags);
 374         job = list_first_entry_or_null(&wb_connector->job_queue,
 375                                        struct drm_writeback_job,
 376                                        list_entry);
 377         if (job)
 378                 list_del(&job->list_entry);
 379
 380         spin_unlock_irqrestore(&wb_connector->job_lock, flags);
 381
 382         if (WARN_ON(!job))
 383                 return;
 384
 385         out_fence = job->out_fence;
 386         if (out_fence) {
 387                 if (status)
 388                         dma_fence_set_error(out_fence, status);
 389                 dma_fence_signal(out_fence);
 390                 dma_fence_put(out_fence);
 391                 job->out_fence = NULL;
 392         }
 393
 394         INIT_WORK(&job->cleanup_work, cleanup_work);
 395         queue_work(system_long_wq, &job->cleanup_work);
 396 }
 397 EXPORT_SYMBOL(drm_writeback_signal_completion);
 398
 399 struct dma_fence *
 400 drm_writeback_get_out_fence(struct drm_writeback_connector *wb_connector)
 401 {
 402         struct dma_fence *fence;
 403
 404         if (WARN_ON(wb_connector->base.connector_type !=
 405                     DRM_MODE_CONNECTOR_WRITEBACK))
 406                 return NULL;
 407
 408         fence = kzalloc(sizeof(*fence), GFP_KERNEL);
 409         if (!fence)
 410                 return NULL;
 411
 412         dma_fence_init(fence, &drm_writeback_fence_ops,
 413                        &wb_connector->fence_lock, wb_connector->fence_context,
 414                        ++wb_connector->fence_seqno);
 415
 416         return fence;
 417 }
 418 EXPORT_SYMBOL(drm_writeback_get_out_fence);