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