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