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};
112
113static 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
148static 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 */
173int 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
233attach_fail:
234	drm_connector_cleanup(connector);
235connector_fail:
236	drm_encoder_cleanup(&wb_connector->encoder);
237fail:
238	drm_property_blob_put(blob);
239	return ret;
240}
241EXPORT_SYMBOL(drm_writeback_connector_init);
242
243int 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
262int 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}
278EXPORT_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 */
299void 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}
312EXPORT_SYMBOL(drm_writeback_queue_job);
313
314void 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}
331EXPORT_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 */
340static 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 */
365void
366drm_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}
397EXPORT_SYMBOL(drm_writeback_signal_completion);
398
399struct dma_fence *
400drm_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}
418EXPORT_SYMBOL(drm_writeback_get_out_fence);