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 
drm_writeback_fence_get_driver_name(struct dma_fence * fence)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 *
drm_writeback_fence_get_timeline_name(struct dma_fence * fence)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 
drm_writeback_fence_enable_signaling(struct dma_fence * fence)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 };
112 
create_writeback_properties(struct drm_device * dev)113 static 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 
148 static 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  * @possible_crtcs: possible crtcs for the internal writeback encoder
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  */
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)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 				 u32 possible_crtcs)
180 {
181 	int ret = 0;
182 
183 	drm_encoder_helper_add(&wb_connector->encoder, enc_helper_funcs);
184 
185 	wb_connector->encoder.possible_crtcs = possible_crtcs;
186 
187 	ret = drm_encoder_init(dev, &wb_connector->encoder,
188 			       &drm_writeback_encoder_funcs,
189 			       DRM_MODE_ENCODER_VIRTUAL, NULL);
190 	if (ret)
191 		return ret;
192 
193 	ret = drm_writeback_connector_init_with_encoder(dev, wb_connector, &wb_connector->encoder,
194 			con_funcs, formats, n_formats);
195 
196 	if (ret)
197 		drm_encoder_cleanup(&wb_connector->encoder);
198 
199 	return ret;
200 }
201 EXPORT_SYMBOL(drm_writeback_connector_init);
202 
203 /**
204  * drm_writeback_connector_init_with_encoder - Initialize a writeback connector with
205  * a custom encoder
206  *
207  * @dev: DRM device
208  * @wb_connector: Writeback connector to initialize
209  * @enc: handle to the already initialized drm encoder
210  * @con_funcs: Connector funcs vtable
211  * @formats: Array of supported pixel formats for the writeback engine
212  * @n_formats: Length of the formats array
213  *
214  * This function creates the writeback-connector-specific properties if they
215  * have not been already created, initializes the connector as
216  * type DRM_MODE_CONNECTOR_WRITEBACK, and correctly initializes the property
217  * values.
218  *
219  * This function assumes that the drm_writeback_connector's encoder has already been
220  * created and initialized before invoking this function.
221  *
222  * In addition, this function also assumes that callers of this API will manage
223  * assigning the encoder helper functions, possible_crtcs and any other encoder
224  * specific operation.
225  *
226  * Drivers should always use this function instead of drm_connector_init() to
227  * set up writeback connectors if they want to manage themselves the lifetime of the
228  * associated encoder.
229  *
230  * Returns: 0 on success, or a negative error code
231  */
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)232 int drm_writeback_connector_init_with_encoder(struct drm_device *dev,
233 		struct drm_writeback_connector *wb_connector, struct drm_encoder *enc,
234 		const struct drm_connector_funcs *con_funcs, const u32 *formats,
235 		int n_formats)
236 {
237 	struct drm_property_blob *blob;
238 	struct drm_connector *connector = &wb_connector->base;
239 	struct drm_mode_config *config = &dev->mode_config;
240 	int ret = create_writeback_properties(dev);
241 
242 	if (ret != 0)
243 		return ret;
244 
245 	blob = drm_property_create_blob(dev, n_formats * sizeof(*formats),
246 					formats);
247 	if (IS_ERR(blob))
248 		return PTR_ERR(blob);
249 
250 
251 	connector->interlace_allowed = 0;
252 
253 	ret = drm_connector_init(dev, connector, con_funcs,
254 				 DRM_MODE_CONNECTOR_WRITEBACK);
255 	if (ret)
256 		goto connector_fail;
257 
258 	ret = drm_connector_attach_encoder(connector, enc);
259 	if (ret)
260 		goto attach_fail;
261 
262 	INIT_LIST_HEAD(&wb_connector->job_queue);
263 	spin_lock_init(&wb_connector->job_lock);
264 
265 	wb_connector->fence_context = dma_fence_context_alloc(1);
266 	spin_lock_init(&wb_connector->fence_lock);
267 	snprintf(wb_connector->timeline_name,
268 		 sizeof(wb_connector->timeline_name),
269 		 "CONNECTOR:%d-%s", connector->base.id, connector->name);
270 
271 	drm_object_attach_property(&connector->base,
272 				   config->writeback_out_fence_ptr_property, 0);
273 
274 	drm_object_attach_property(&connector->base,
275 				   config->writeback_fb_id_property, 0);
276 
277 	drm_object_attach_property(&connector->base,
278 				   config->writeback_pixel_formats_property,
279 				   blob->base.id);
280 	wb_connector->pixel_formats_blob_ptr = blob;
281 
282 	return 0;
283 
284 attach_fail:
285 	drm_connector_cleanup(connector);
286 connector_fail:
287 	drm_property_blob_put(blob);
288 	return ret;
289 }
290 EXPORT_SYMBOL(drm_writeback_connector_init_with_encoder);
291 
drm_writeback_set_fb(struct drm_connector_state * conn_state,struct drm_framebuffer * fb)292 int drm_writeback_set_fb(struct drm_connector_state *conn_state,
293 			 struct drm_framebuffer *fb)
294 {
295 	WARN_ON(conn_state->connector->connector_type != DRM_MODE_CONNECTOR_WRITEBACK);
296 
297 	if (!conn_state->writeback_job) {
298 		conn_state->writeback_job =
299 			kzalloc(sizeof(*conn_state->writeback_job), GFP_KERNEL);
300 		if (!conn_state->writeback_job)
301 			return -ENOMEM;
302 
303 		conn_state->writeback_job->connector =
304 			drm_connector_to_writeback(conn_state->connector);
305 	}
306 
307 	drm_framebuffer_assign(&conn_state->writeback_job->fb, fb);
308 	return 0;
309 }
310 
drm_writeback_prepare_job(struct drm_writeback_job * job)311 int drm_writeback_prepare_job(struct drm_writeback_job *job)
312 {
313 	struct drm_writeback_connector *connector = job->connector;
314 	const struct drm_connector_helper_funcs *funcs =
315 		connector->base.helper_private;
316 	int ret;
317 
318 	if (funcs->prepare_writeback_job) {
319 		ret = funcs->prepare_writeback_job(connector, job);
320 		if (ret < 0)
321 			return ret;
322 	}
323 
324 	job->prepared = true;
325 	return 0;
326 }
327 EXPORT_SYMBOL(drm_writeback_prepare_job);
328 
329 /**
330  * drm_writeback_queue_job - Queue a writeback job for later signalling
331  * @wb_connector: The writeback connector to queue a job on
332  * @conn_state: The connector state containing the job to queue
333  *
334  * This function adds the job contained in @conn_state to the job_queue for a
335  * writeback connector. It takes ownership of the writeback job and sets the
336  * @conn_state->writeback_job to NULL, and so no access to the job may be
337  * performed by the caller after this function returns.
338  *
339  * Drivers must ensure that for a given writeback connector, jobs are queued in
340  * exactly the same order as they will be completed by the hardware (and
341  * signaled via drm_writeback_signal_completion).
342  *
343  * For every call to drm_writeback_queue_job() there must be exactly one call to
344  * drm_writeback_signal_completion()
345  *
346  * See also: drm_writeback_signal_completion()
347  */
drm_writeback_queue_job(struct drm_writeback_connector * wb_connector,struct drm_connector_state * conn_state)348 void drm_writeback_queue_job(struct drm_writeback_connector *wb_connector,
349 			     struct drm_connector_state *conn_state)
350 {
351 	struct drm_writeback_job *job;
352 	unsigned long flags;
353 
354 	job = conn_state->writeback_job;
355 	conn_state->writeback_job = NULL;
356 
357 	spin_lock_irqsave(&wb_connector->job_lock, flags);
358 	list_add_tail(&job->list_entry, &wb_connector->job_queue);
359 	spin_unlock_irqrestore(&wb_connector->job_lock, flags);
360 }
361 EXPORT_SYMBOL(drm_writeback_queue_job);
362 
drm_writeback_cleanup_job(struct drm_writeback_job * job)363 void drm_writeback_cleanup_job(struct drm_writeback_job *job)
364 {
365 	struct drm_writeback_connector *connector = job->connector;
366 	const struct drm_connector_helper_funcs *funcs =
367 		connector->base.helper_private;
368 
369 	if (job->prepared && funcs->cleanup_writeback_job)
370 		funcs->cleanup_writeback_job(connector, job);
371 
372 	if (job->fb)
373 		drm_framebuffer_put(job->fb);
374 
375 	if (job->out_fence)
376 		dma_fence_put(job->out_fence);
377 
378 	kfree(job);
379 }
380 EXPORT_SYMBOL(drm_writeback_cleanup_job);
381 
382 /*
383  * @cleanup_work: deferred cleanup of a writeback job
384  *
385  * The job cannot be cleaned up directly in drm_writeback_signal_completion,
386  * because it may be called in interrupt context. Dropping the framebuffer
387  * reference can sleep, and so the cleanup is deferred to a workqueue.
388  */
cleanup_work(struct work_struct * work)389 static void cleanup_work(struct work_struct *work)
390 {
391 	struct drm_writeback_job *job = container_of(work,
392 						     struct drm_writeback_job,
393 						     cleanup_work);
394 
395 	drm_writeback_cleanup_job(job);
396 }
397 
398 /**
399  * drm_writeback_signal_completion - Signal the completion of a writeback job
400  * @wb_connector: The writeback connector whose job is complete
401  * @status: Status code to set in the writeback out_fence (0 for success)
402  *
403  * Drivers should call this to signal the completion of a previously queued
404  * writeback job. It should be called as soon as possible after the hardware
405  * has finished writing, and may be called from interrupt context.
406  * It is the driver's responsibility to ensure that for a given connector, the
407  * hardware completes writeback jobs in the same order as they are queued.
408  *
409  * Unless the driver is holding its own reference to the framebuffer, it must
410  * not be accessed after calling this function.
411  *
412  * See also: drm_writeback_queue_job()
413  */
414 void
drm_writeback_signal_completion(struct drm_writeback_connector * wb_connector,int status)415 drm_writeback_signal_completion(struct drm_writeback_connector *wb_connector,
416 				int status)
417 {
418 	unsigned long flags;
419 	struct drm_writeback_job *job;
420 	struct dma_fence *out_fence;
421 
422 	spin_lock_irqsave(&wb_connector->job_lock, flags);
423 	job = list_first_entry_or_null(&wb_connector->job_queue,
424 				       struct drm_writeback_job,
425 				       list_entry);
426 	if (job)
427 		list_del(&job->list_entry);
428 
429 	spin_unlock_irqrestore(&wb_connector->job_lock, flags);
430 
431 	if (WARN_ON(!job))
432 		return;
433 
434 	out_fence = job->out_fence;
435 	if (out_fence) {
436 		if (status)
437 			dma_fence_set_error(out_fence, status);
438 		dma_fence_signal(out_fence);
439 		dma_fence_put(out_fence);
440 		job->out_fence = NULL;
441 	}
442 
443 	INIT_WORK(&job->cleanup_work, cleanup_work);
444 	queue_work(system_long_wq, &job->cleanup_work);
445 }
446 EXPORT_SYMBOL(drm_writeback_signal_completion);
447 
448 struct dma_fence *
drm_writeback_get_out_fence(struct drm_writeback_connector * wb_connector)449 drm_writeback_get_out_fence(struct drm_writeback_connector *wb_connector)
450 {
451 	struct dma_fence *fence;
452 
453 	if (WARN_ON(wb_connector->base.connector_type !=
454 		    DRM_MODE_CONNECTOR_WRITEBACK))
455 		return NULL;
456 
457 	fence = kzalloc(sizeof(*fence), GFP_KERNEL);
458 	if (!fence)
459 		return NULL;
460 
461 	dma_fence_init(fence, &drm_writeback_fence_ops,
462 		       &wb_connector->fence_lock, wb_connector->fence_context,
463 		       ++wb_connector->fence_seqno);
464 
465 	return fence;
466 }
467 EXPORT_SYMBOL(drm_writeback_get_out_fence);
468