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_framebuffer.h>
18 #include <drm/drm_modeset_helper_vtables.h>
19 #include <drm/drm_property.h>
20 #include <drm/drm_writeback.h>
21 
22 /**
23  * DOC: overview
24  *
25  * Writeback connectors are used to expose hardware which can write the output
26  * from a CRTC to a memory buffer. They are used and act similarly to other
27  * types of connectors, with some important differences:
28  *
29  * * Writeback connectors don't provide a way to output visually to the user.
30  *
31  * * Writeback connectors are visible to userspace only when the client sets
32  *   DRM_CLIENT_CAP_WRITEBACK_CONNECTORS.
33  *
34  * * Writeback connectors don't have EDID.
35  *
36  * A framebuffer may only be attached to a writeback connector when the
37  * connector is attached to a CRTC. The WRITEBACK_FB_ID property which sets the
38  * framebuffer applies only to a single commit (see below). A framebuffer may
39  * not be attached while the CRTC is off.
40  *
41  * Unlike with planes, when a writeback framebuffer is removed by userspace DRM
42  * makes no attempt to remove it from active use by the connector. This is
43  * because no method is provided to abort a writeback operation, and in any
44  * case making a new commit whilst a writeback is ongoing is undefined (see
45  * WRITEBACK_OUT_FENCE_PTR below). As soon as the current writeback is finished,
46  * the framebuffer will automatically no longer be in active use. As it will
47  * also have already been removed from the framebuffer list, there will be no
48  * way for any userspace application to retrieve a reference to it in the
49  * intervening period.
50  *
51  * Writeback connectors have some additional properties, which userspace
52  * can use to query and control them:
53  *
54  *  "WRITEBACK_FB_ID":
55  *	Write-only object property storing a DRM_MODE_OBJECT_FB: it stores the
56  *	framebuffer to be written by the writeback connector. This property is
57  *	similar to the FB_ID property on planes, but will always read as zero
58  *	and is not preserved across commits.
59  *	Userspace must set this property to an output buffer every time it
60  *	wishes the buffer to get filled.
61  *
62  *  "WRITEBACK_PIXEL_FORMATS":
63  *	Immutable blob property to store the supported pixel formats table. The
64  *	data is an array of u32 DRM_FORMAT_* fourcc values.
65  *	Userspace can use this blob to find out what pixel formats are supported
66  *	by the connector's writeback engine.
67  *
68  *  "WRITEBACK_OUT_FENCE_PTR":
69  *	Userspace can use this property to provide a pointer for the kernel to
70  *	fill with a sync_file file descriptor, which will signal once the
71  *	writeback is finished. The value should be the address of a 32-bit
72  *	signed integer, cast to a u64.
73  *	Userspace should wait for this fence to signal before making another
74  *	commit affecting any of the same CRTCs, Planes or Connectors.
75  *	**Failure to do so will result in undefined behaviour.**
76  *	For this reason it is strongly recommended that all userspace
77  *	applications making use of writeback connectors *always* retrieve an
78  *	out-fence for the commit and use it appropriately.
79  *	From userspace, this property will always read as zero.
80  */
81 
82 #define fence_to_wb_connector(x) container_of(x->lock, \
83 					      struct drm_writeback_connector, \
84 					      fence_lock)
85 
drm_writeback_fence_get_driver_name(struct dma_fence * fence)86 static const char *drm_writeback_fence_get_driver_name(struct dma_fence *fence)
87 {
88 	struct drm_writeback_connector *wb_connector =
89 		fence_to_wb_connector(fence);
90 
91 	return wb_connector->base.dev->driver->name;
92 }
93 
94 static const char *
drm_writeback_fence_get_timeline_name(struct dma_fence * fence)95 drm_writeback_fence_get_timeline_name(struct dma_fence *fence)
96 {
97 	struct drm_writeback_connector *wb_connector =
98 		fence_to_wb_connector(fence);
99 
100 	return wb_connector->timeline_name;
101 }
102 
drm_writeback_fence_enable_signaling(struct dma_fence * fence)103 static bool drm_writeback_fence_enable_signaling(struct dma_fence *fence)
104 {
105 	return true;
106 }
107 
108 static const struct dma_fence_ops drm_writeback_fence_ops = {
109 	.get_driver_name = drm_writeback_fence_get_driver_name,
110 	.get_timeline_name = drm_writeback_fence_get_timeline_name,
111 	.enable_signaling = drm_writeback_fence_enable_signaling,
112 };
113 
create_writeback_properties(struct drm_device * dev)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  * @possible_crtcs: possible crtcs for the internal writeback encoder
162  *
163  * This function creates the writeback-connector-specific properties if they
164  * have not been already created, initializes the connector as
165  * type DRM_MODE_CONNECTOR_WRITEBACK, and correctly initializes the property
166  * values. It will also create an internal encoder associated with the
167  * drm_writeback_connector and set it to use the @enc_helper_funcs vtable for
168  * the encoder helper.
169  *
170  * Drivers should always use this function instead of drm_connector_init() to
171  * set up writeback connectors.
172  *
173  * Returns: 0 on success, or a negative error code
174  */
drm_writeback_connector_init(struct drm_device * dev,struct drm_writeback_connector * wb_connector,const struct drm_connector_funcs * con_funcs,const struct drm_encoder_helper_funcs * enc_helper_funcs,const u32 * formats,int n_formats,u32 possible_crtcs)175 int drm_writeback_connector_init(struct drm_device *dev,
176 				 struct drm_writeback_connector *wb_connector,
177 				 const struct drm_connector_funcs *con_funcs,
178 				 const struct drm_encoder_helper_funcs *enc_helper_funcs,
179 				 const u32 *formats, int n_formats,
180 				 u32 possible_crtcs)
181 {
182 	int ret = 0;
183 
184 	drm_encoder_helper_add(&wb_connector->encoder, enc_helper_funcs);
185 
186 	wb_connector->encoder.possible_crtcs = possible_crtcs;
187 
188 	ret = drm_encoder_init(dev, &wb_connector->encoder,
189 			       &drm_writeback_encoder_funcs,
190 			       DRM_MODE_ENCODER_VIRTUAL, NULL);
191 	if (ret)
192 		return ret;
193 
194 	ret = drm_writeback_connector_init_with_encoder(dev, wb_connector, &wb_connector->encoder,
195 			con_funcs, formats, n_formats);
196 
197 	if (ret)
198 		drm_encoder_cleanup(&wb_connector->encoder);
199 
200 	return ret;
201 }
202 EXPORT_SYMBOL(drm_writeback_connector_init);
203 
204 /**
205  * drm_writeback_connector_init_with_encoder - Initialize a writeback connector with
206  * a custom encoder
207  *
208  * @dev: DRM device
209  * @wb_connector: Writeback connector to initialize
210  * @enc: handle to the already initialized drm encoder
211  * @con_funcs: Connector funcs vtable
212  * @formats: Array of supported pixel formats for the writeback engine
213  * @n_formats: Length of the formats array
214  *
215  * This function creates the writeback-connector-specific properties if they
216  * have not been already created, initializes the connector as
217  * type DRM_MODE_CONNECTOR_WRITEBACK, and correctly initializes the property
218  * values.
219  *
220  * This function assumes that the drm_writeback_connector's encoder has already been
221  * created and initialized before invoking this function.
222  *
223  * In addition, this function also assumes that callers of this API will manage
224  * assigning the encoder helper functions, possible_crtcs and any other encoder
225  * specific operation.
226  *
227  * Drivers should always use this function instead of drm_connector_init() to
228  * set up writeback connectors if they want to manage themselves the lifetime of the
229  * associated encoder.
230  *
231  * Returns: 0 on success, or a negative error code
232  */
drm_writeback_connector_init_with_encoder(struct drm_device * dev,struct drm_writeback_connector * wb_connector,struct drm_encoder * enc,const struct drm_connector_funcs * con_funcs,const u32 * formats,int n_formats)233 int drm_writeback_connector_init_with_encoder(struct drm_device *dev,
234 		struct drm_writeback_connector *wb_connector, struct drm_encoder *enc,
235 		const struct drm_connector_funcs *con_funcs, const u32 *formats,
236 		int n_formats)
237 {
238 	struct drm_property_blob *blob;
239 	struct drm_connector *connector = &wb_connector->base;
240 	struct drm_mode_config *config = &dev->mode_config;
241 	int ret = create_writeback_properties(dev);
242 
243 	if (ret != 0)
244 		return ret;
245 
246 	blob = drm_property_create_blob(dev, n_formats * sizeof(*formats),
247 					formats);
248 	if (IS_ERR(blob))
249 		return PTR_ERR(blob);
250 
251 
252 	connector->interlace_allowed = 0;
253 
254 	ret = drm_connector_init(dev, connector, con_funcs,
255 				 DRM_MODE_CONNECTOR_WRITEBACK);
256 	if (ret)
257 		goto connector_fail;
258 
259 	ret = drm_connector_attach_encoder(connector, enc);
260 	if (ret)
261 		goto attach_fail;
262 
263 	INIT_LIST_HEAD(&wb_connector->job_queue);
264 	spin_lock_init(&wb_connector->job_lock);
265 
266 	wb_connector->fence_context = dma_fence_context_alloc(1);
267 	spin_lock_init(&wb_connector->fence_lock);
268 	snprintf(wb_connector->timeline_name,
269 		 sizeof(wb_connector->timeline_name),
270 		 "CONNECTOR:%d-%s", connector->base.id, connector->name);
271 
272 	drm_object_attach_property(&connector->base,
273 				   config->writeback_out_fence_ptr_property, 0);
274 
275 	drm_object_attach_property(&connector->base,
276 				   config->writeback_fb_id_property, 0);
277 
278 	drm_object_attach_property(&connector->base,
279 				   config->writeback_pixel_formats_property,
280 				   blob->base.id);
281 	wb_connector->pixel_formats_blob_ptr = blob;
282 
283 	return 0;
284 
285 attach_fail:
286 	drm_connector_cleanup(connector);
287 connector_fail:
288 	drm_property_blob_put(blob);
289 	return ret;
290 }
291 EXPORT_SYMBOL(drm_writeback_connector_init_with_encoder);
292 
drm_writeback_set_fb(struct drm_connector_state * conn_state,struct drm_framebuffer * fb)293 int drm_writeback_set_fb(struct drm_connector_state *conn_state,
294 			 struct drm_framebuffer *fb)
295 {
296 	WARN_ON(conn_state->connector->connector_type != DRM_MODE_CONNECTOR_WRITEBACK);
297 
298 	if (!conn_state->writeback_job) {
299 		conn_state->writeback_job =
300 			kzalloc(sizeof(*conn_state->writeback_job), GFP_KERNEL);
301 		if (!conn_state->writeback_job)
302 			return -ENOMEM;
303 
304 		conn_state->writeback_job->connector =
305 			drm_connector_to_writeback(conn_state->connector);
306 	}
307 
308 	drm_framebuffer_assign(&conn_state->writeback_job->fb, fb);
309 	return 0;
310 }
311 
drm_writeback_prepare_job(struct drm_writeback_job * job)312 int drm_writeback_prepare_job(struct drm_writeback_job *job)
313 {
314 	struct drm_writeback_connector *connector = job->connector;
315 	const struct drm_connector_helper_funcs *funcs =
316 		connector->base.helper_private;
317 	int ret;
318 
319 	if (funcs->prepare_writeback_job) {
320 		ret = funcs->prepare_writeback_job(connector, job);
321 		if (ret < 0)
322 			return ret;
323 	}
324 
325 	job->prepared = true;
326 	return 0;
327 }
328 EXPORT_SYMBOL(drm_writeback_prepare_job);
329 
330 /**
331  * drm_writeback_queue_job - Queue a writeback job for later signalling
332  * @wb_connector: The writeback connector to queue a job on
333  * @conn_state: The connector state containing the job to queue
334  *
335  * This function adds the job contained in @conn_state to the job_queue for a
336  * writeback connector. It takes ownership of the writeback job and sets the
337  * @conn_state->writeback_job to NULL, and so no access to the job may be
338  * performed by the caller after this function returns.
339  *
340  * Drivers must ensure that for a given writeback connector, jobs are queued in
341  * exactly the same order as they will be completed by the hardware (and
342  * signaled via drm_writeback_signal_completion).
343  *
344  * For every call to drm_writeback_queue_job() there must be exactly one call to
345  * drm_writeback_signal_completion()
346  *
347  * See also: drm_writeback_signal_completion()
348  */
drm_writeback_queue_job(struct drm_writeback_connector * wb_connector,struct drm_connector_state * conn_state)349 void drm_writeback_queue_job(struct drm_writeback_connector *wb_connector,
350 			     struct drm_connector_state *conn_state)
351 {
352 	struct drm_writeback_job *job;
353 	unsigned long flags;
354 
355 	job = conn_state->writeback_job;
356 	conn_state->writeback_job = NULL;
357 
358 	spin_lock_irqsave(&wb_connector->job_lock, flags);
359 	list_add_tail(&job->list_entry, &wb_connector->job_queue);
360 	spin_unlock_irqrestore(&wb_connector->job_lock, flags);
361 }
362 EXPORT_SYMBOL(drm_writeback_queue_job);
363 
drm_writeback_cleanup_job(struct drm_writeback_job * job)364 void drm_writeback_cleanup_job(struct drm_writeback_job *job)
365 {
366 	struct drm_writeback_connector *connector = job->connector;
367 	const struct drm_connector_helper_funcs *funcs =
368 		connector->base.helper_private;
369 
370 	if (job->prepared && funcs->cleanup_writeback_job)
371 		funcs->cleanup_writeback_job(connector, job);
372 
373 	if (job->fb)
374 		drm_framebuffer_put(job->fb);
375 
376 	if (job->out_fence)
377 		dma_fence_put(job->out_fence);
378 
379 	kfree(job);
380 }
381 EXPORT_SYMBOL(drm_writeback_cleanup_job);
382 
383 /*
384  * @cleanup_work: deferred cleanup of a writeback job
385  *
386  * The job cannot be cleaned up directly in drm_writeback_signal_completion,
387  * because it may be called in interrupt context. Dropping the framebuffer
388  * reference can sleep, and so the cleanup is deferred to a workqueue.
389  */
cleanup_work(struct work_struct * work)390 static void cleanup_work(struct work_struct *work)
391 {
392 	struct drm_writeback_job *job = container_of(work,
393 						     struct drm_writeback_job,
394 						     cleanup_work);
395 
396 	drm_writeback_cleanup_job(job);
397 }
398 
399 /**
400  * drm_writeback_signal_completion - Signal the completion of a writeback job
401  * @wb_connector: The writeback connector whose job is complete
402  * @status: Status code to set in the writeback out_fence (0 for success)
403  *
404  * Drivers should call this to signal the completion of a previously queued
405  * writeback job. It should be called as soon as possible after the hardware
406  * has finished writing, and may be called from interrupt context.
407  * It is the driver's responsibility to ensure that for a given connector, the
408  * hardware completes writeback jobs in the same order as they are queued.
409  *
410  * Unless the driver is holding its own reference to the framebuffer, it must
411  * not be accessed after calling this function.
412  *
413  * See also: drm_writeback_queue_job()
414  */
415 void
drm_writeback_signal_completion(struct drm_writeback_connector * wb_connector,int status)416 drm_writeback_signal_completion(struct drm_writeback_connector *wb_connector,
417 				int status)
418 {
419 	unsigned long flags;
420 	struct drm_writeback_job *job;
421 	struct dma_fence *out_fence;
422 
423 	spin_lock_irqsave(&wb_connector->job_lock, flags);
424 	job = list_first_entry_or_null(&wb_connector->job_queue,
425 				       struct drm_writeback_job,
426 				       list_entry);
427 	if (job)
428 		list_del(&job->list_entry);
429 
430 	spin_unlock_irqrestore(&wb_connector->job_lock, flags);
431 
432 	if (WARN_ON(!job))
433 		return;
434 
435 	out_fence = job->out_fence;
436 	if (out_fence) {
437 		if (status)
438 			dma_fence_set_error(out_fence, status);
439 		dma_fence_signal(out_fence);
440 		dma_fence_put(out_fence);
441 		job->out_fence = NULL;
442 	}
443 
444 	INIT_WORK(&job->cleanup_work, cleanup_work);
445 	queue_work(system_long_wq, &job->cleanup_work);
446 }
447 EXPORT_SYMBOL(drm_writeback_signal_completion);
448 
449 struct dma_fence *
drm_writeback_get_out_fence(struct drm_writeback_connector * wb_connector)450 drm_writeback_get_out_fence(struct drm_writeback_connector *wb_connector)
451 {
452 	struct dma_fence *fence;
453 
454 	if (WARN_ON(wb_connector->base.connector_type !=
455 		    DRM_MODE_CONNECTOR_WRITEBACK))
456 		return NULL;
457 
458 	fence = kzalloc(sizeof(*fence), GFP_KERNEL);
459 	if (!fence)
460 		return NULL;
461 
462 	dma_fence_init(fence, &drm_writeback_fence_ops,
463 		       &wb_connector->fence_lock, wb_connector->fence_context,
464 		       ++wb_connector->fence_seqno);
465 
466 	return fence;
467 }
468 EXPORT_SYMBOL(drm_writeback_get_out_fence);
469