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