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
 85static 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
 93static const char *
 94drm_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
102static bool drm_writeback_fence_enable_signaling(struct dma_fence *fence)
103{
104	return true;
105}
106
107static 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
114static 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
149static 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 */
174int 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
234attach_fail:
235	drm_connector_cleanup(connector);
236connector_fail:
237	drm_encoder_cleanup(&wb_connector->encoder);
238fail:
239	drm_property_blob_put(blob);
240	return ret;
241}
242EXPORT_SYMBOL(drm_writeback_connector_init);
243
244int 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
263int 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}
279EXPORT_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 */
300void 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}
313EXPORT_SYMBOL(drm_writeback_queue_job);
314
315void 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}
332EXPORT_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 */
341static 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 */
366void
367drm_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}
398EXPORT_SYMBOL(drm_writeback_signal_completion);
399
400struct dma_fence *
401drm_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}
419EXPORT_SYMBOL(drm_writeback_get_out_fence);