1 // SPDX-License-Identifier: GPL-2.0
3 * (C) COPYRIGHT 2016 ARM Limited. All rights reserved.
4 * Author: Brian Starkey <brian.starkey@arm.com>
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
12 #include <drm/drm_crtc.h>
13 #include <drm/drm_modeset_helper_vtables.h>
14 #include <drm/drm_property.h>
15 #include <drm/drm_writeback.h>
17 #include <linux/dma-fence.h>
22 * Writeback connectors are used to expose hardware which can write the output
23 * from a CRTC to a memory buffer. They are used and act similarly to other
24 * types of connectors, with some important differences:
26 * * Writeback connectors don't provide a way to output visually to the user.
28 * * Writeback connectors are visible to userspace only when the client sets
29 * DRM_CLIENT_CAP_WRITEBACK_CONNECTORS.
31 * * Writeback connectors don't have EDID.
33 * A framebuffer may only be attached to a writeback connector when the
34 * connector is attached to a CRTC. The WRITEBACK_FB_ID property which sets the
35 * framebuffer applies only to a single commit (see below). A framebuffer may
36 * not be attached while the CRTC is off.
38 * Unlike with planes, when a writeback framebuffer is removed by userspace DRM
39 * makes no attempt to remove it from active use by the connector. This is
40 * because no method is provided to abort a writeback operation, and in any
41 * case making a new commit whilst a writeback is ongoing is undefined (see
42 * WRITEBACK_OUT_FENCE_PTR below). As soon as the current writeback is finished,
43 * the framebuffer will automatically no longer be in active use. As it will
44 * also have already been removed from the framebuffer list, there will be no
45 * way for any userspace application to retrieve a reference to it in the
48 * Writeback connectors have some additional properties, which userspace
49 * can use to query and control them:
52 * Write-only object property storing a DRM_MODE_OBJECT_FB: it stores the
53 * framebuffer to be written by the writeback connector. This property is
54 * similar to the FB_ID property on planes, but will always read as zero
55 * and is not preserved across commits.
56 * Userspace must set this property to an output buffer every time it
57 * wishes the buffer to get filled.
59 * "WRITEBACK_PIXEL_FORMATS":
60 * Immutable blob property to store the supported pixel formats table. The
61 * data is an array of u32 DRM_FORMAT_* fourcc values.
62 * Userspace can use this blob to find out what pixel formats are supported
63 * by the connector's writeback engine.
65 * "WRITEBACK_OUT_FENCE_PTR":
66 * Userspace can use this property to provide a pointer for the kernel to
67 * fill with a sync_file file descriptor, which will signal once the
68 * writeback is finished. The value should be the address of a 32-bit
69 * signed integer, cast to a u64.
70 * Userspace should wait for this fence to signal before making another
71 * commit affecting any of the same CRTCs, Planes or Connectors.
72 * **Failure to do so will result in undefined behaviour.**
73 * For this reason it is strongly recommended that all userspace
74 * applications making use of writeback connectors *always* retrieve an
75 * out-fence for the commit and use it appropriately.
76 * From userspace, this property will always read as zero.
79 #define fence_to_wb_connector(x) container_of(x->lock, \
80 struct drm_writeback_connector, \
83 static const char *drm_writeback_fence_get_driver_name(struct dma_fence
*fence
)
85 struct drm_writeback_connector
*wb_connector
=
86 fence_to_wb_connector(fence
);
88 return wb_connector
->base
.dev
->driver
->name
;
92 drm_writeback_fence_get_timeline_name(struct dma_fence
*fence
)
94 struct drm_writeback_connector
*wb_connector
=
95 fence_to_wb_connector(fence
);
97 return wb_connector
->timeline_name
;
100 static bool drm_writeback_fence_enable_signaling(struct dma_fence
*fence
)
105 static const struct dma_fence_ops drm_writeback_fence_ops
= {
106 .get_driver_name
= drm_writeback_fence_get_driver_name
,
107 .get_timeline_name
= drm_writeback_fence_get_timeline_name
,
108 .enable_signaling
= drm_writeback_fence_enable_signaling
,
109 .wait
= dma_fence_default_wait
,
112 static int create_writeback_properties(struct drm_device
*dev
)
114 struct drm_property
*prop
;
116 if (!dev
->mode_config
.writeback_fb_id_property
) {
117 prop
= drm_property_create_object(dev
, DRM_MODE_PROP_ATOMIC
,
122 dev
->mode_config
.writeback_fb_id_property
= prop
;
125 if (!dev
->mode_config
.writeback_pixel_formats_property
) {
126 prop
= drm_property_create(dev
, DRM_MODE_PROP_BLOB
|
127 DRM_MODE_PROP_ATOMIC
|
128 DRM_MODE_PROP_IMMUTABLE
,
129 "WRITEBACK_PIXEL_FORMATS", 0);
132 dev
->mode_config
.writeback_pixel_formats_property
= prop
;
135 if (!dev
->mode_config
.writeback_out_fence_ptr_property
) {
136 prop
= drm_property_create_range(dev
, DRM_MODE_PROP_ATOMIC
,
137 "WRITEBACK_OUT_FENCE_PTR", 0,
141 dev
->mode_config
.writeback_out_fence_ptr_property
= prop
;
147 static const struct drm_encoder_funcs drm_writeback_encoder_funcs
= {
148 .destroy
= drm_encoder_cleanup
,
152 * drm_writeback_connector_init - Initialize a writeback connector and its properties
154 * @wb_connector: Writeback connector to initialize
155 * @con_funcs: Connector funcs vtable
156 * @enc_helper_funcs: Encoder helper funcs vtable to be used by the internal encoder
157 * @formats: Array of supported pixel formats for the writeback engine
158 * @n_formats: Length of the formats array
160 * This function creates the writeback-connector-specific properties if they
161 * have not been already created, initializes the connector as
162 * type DRM_MODE_CONNECTOR_WRITEBACK, and correctly initializes the property
163 * values. It will also create an internal encoder associated with the
164 * drm_writeback_connector and set it to use the @enc_helper_funcs vtable for
165 * the encoder helper.
167 * Drivers should always use this function instead of drm_connector_init() to
168 * set up writeback connectors.
170 * Returns: 0 on success, or a negative error code
172 int drm_writeback_connector_init(struct drm_device
*dev
,
173 struct drm_writeback_connector
*wb_connector
,
174 const struct drm_connector_funcs
*con_funcs
,
175 const struct drm_encoder_helper_funcs
*enc_helper_funcs
,
176 const u32
*formats
, int n_formats
)
178 struct drm_property_blob
*blob
;
179 struct drm_connector
*connector
= &wb_connector
->base
;
180 struct drm_mode_config
*config
= &dev
->mode_config
;
181 int ret
= create_writeback_properties(dev
);
186 blob
= drm_property_create_blob(dev
, n_formats
* sizeof(*formats
),
189 return PTR_ERR(blob
);
191 drm_encoder_helper_add(&wb_connector
->encoder
, enc_helper_funcs
);
192 ret
= drm_encoder_init(dev
, &wb_connector
->encoder
,
193 &drm_writeback_encoder_funcs
,
194 DRM_MODE_ENCODER_VIRTUAL
, NULL
);
198 connector
->interlace_allowed
= 0;
200 ret
= drm_connector_init(dev
, connector
, con_funcs
,
201 DRM_MODE_CONNECTOR_WRITEBACK
);
205 ret
= drm_connector_attach_encoder(connector
,
206 &wb_connector
->encoder
);
210 INIT_LIST_HEAD(&wb_connector
->job_queue
);
211 spin_lock_init(&wb_connector
->job_lock
);
213 wb_connector
->fence_context
= dma_fence_context_alloc(1);
214 spin_lock_init(&wb_connector
->fence_lock
);
215 snprintf(wb_connector
->timeline_name
,
216 sizeof(wb_connector
->timeline_name
),
217 "CONNECTOR:%d-%s", connector
->base
.id
, connector
->name
);
219 drm_object_attach_property(&connector
->base
,
220 config
->writeback_out_fence_ptr_property
, 0);
222 drm_object_attach_property(&connector
->base
,
223 config
->writeback_fb_id_property
, 0);
225 drm_object_attach_property(&connector
->base
,
226 config
->writeback_pixel_formats_property
,
228 wb_connector
->pixel_formats_blob_ptr
= blob
;
233 drm_connector_cleanup(connector
);
235 drm_encoder_cleanup(&wb_connector
->encoder
);
237 drm_property_blob_put(blob
);
240 EXPORT_SYMBOL(drm_writeback_connector_init
);
242 int drm_writeback_set_fb(struct drm_connector_state
*conn_state
,
243 struct drm_framebuffer
*fb
)
245 WARN_ON(conn_state
->connector
->connector_type
!= DRM_MODE_CONNECTOR_WRITEBACK
);
247 if (!conn_state
->writeback_job
) {
248 conn_state
->writeback_job
=
249 kzalloc(sizeof(*conn_state
->writeback_job
), GFP_KERNEL
);
250 if (!conn_state
->writeback_job
)
253 conn_state
->writeback_job
->connector
=
254 drm_connector_to_writeback(conn_state
->connector
);
257 drm_framebuffer_assign(&conn_state
->writeback_job
->fb
, fb
);
261 int drm_writeback_prepare_job(struct drm_writeback_job
*job
)
263 struct drm_writeback_connector
*connector
= job
->connector
;
264 const struct drm_connector_helper_funcs
*funcs
=
265 connector
->base
.helper_private
;
268 if (funcs
->prepare_writeback_job
) {
269 ret
= funcs
->prepare_writeback_job(connector
, job
);
274 job
->prepared
= true;
277 EXPORT_SYMBOL(drm_writeback_prepare_job
);
280 * drm_writeback_queue_job - Queue a writeback job for later signalling
281 * @wb_connector: The writeback connector to queue a job on
282 * @conn_state: The connector state containing the job to queue
284 * This function adds the job contained in @conn_state to the job_queue for a
285 * writeback connector. It takes ownership of the writeback job and sets the
286 * @conn_state->writeback_job to NULL, and so no access to the job may be
287 * performed by the caller after this function returns.
289 * Drivers must ensure that for a given writeback connector, jobs are queued in
290 * exactly the same order as they will be completed by the hardware (and
291 * signaled via drm_writeback_signal_completion).
293 * For every call to drm_writeback_queue_job() there must be exactly one call to
294 * drm_writeback_signal_completion()
296 * See also: drm_writeback_signal_completion()
298 void drm_writeback_queue_job(struct drm_writeback_connector
*wb_connector
,
299 struct drm_connector_state
*conn_state
)
301 struct drm_writeback_job
*job
;
304 job
= conn_state
->writeback_job
;
305 conn_state
->writeback_job
= NULL
;
307 spin_lock_irqsave(&wb_connector
->job_lock
, flags
);
308 list_add_tail(&job
->list_entry
, &wb_connector
->job_queue
);
309 spin_unlock_irqrestore(&wb_connector
->job_lock
, flags
);
311 EXPORT_SYMBOL(drm_writeback_queue_job
);
313 void drm_writeback_cleanup_job(struct drm_writeback_job
*job
)
315 struct drm_writeback_connector
*connector
= job
->connector
;
316 const struct drm_connector_helper_funcs
*funcs
=
317 connector
->base
.helper_private
;
319 if (job
->prepared
&& funcs
->cleanup_writeback_job
)
320 funcs
->cleanup_writeback_job(connector
, job
);
323 drm_framebuffer_put(job
->fb
);
327 EXPORT_SYMBOL(drm_writeback_cleanup_job
);
330 * @cleanup_work: deferred cleanup of a writeback job
332 * The job cannot be cleaned up directly in drm_writeback_signal_completion,
333 * because it may be called in interrupt context. Dropping the framebuffer
334 * reference can sleep, and so the cleanup is deferred to a workqueue.
336 static void cleanup_work(struct work_struct
*work
)
338 struct drm_writeback_job
*job
= container_of(work
,
339 struct drm_writeback_job
,
342 drm_writeback_cleanup_job(job
);
346 * drm_writeback_signal_completion - Signal the completion of a writeback job
347 * @wb_connector: The writeback connector whose job is complete
348 * @status: Status code to set in the writeback out_fence (0 for success)
350 * Drivers should call this to signal the completion of a previously queued
351 * writeback job. It should be called as soon as possible after the hardware
352 * has finished writing, and may be called from interrupt context.
353 * It is the driver's responsibility to ensure that for a given connector, the
354 * hardware completes writeback jobs in the same order as they are queued.
356 * Unless the driver is holding its own reference to the framebuffer, it must
357 * not be accessed after calling this function.
359 * See also: drm_writeback_queue_job()
362 drm_writeback_signal_completion(struct drm_writeback_connector
*wb_connector
,
366 struct drm_writeback_job
*job
;
368 spin_lock_irqsave(&wb_connector
->job_lock
, flags
);
369 job
= list_first_entry_or_null(&wb_connector
->job_queue
,
370 struct drm_writeback_job
,
373 list_del(&job
->list_entry
);
374 if (job
->out_fence
) {
376 dma_fence_set_error(job
->out_fence
, status
);
377 dma_fence_signal(job
->out_fence
);
378 dma_fence_put(job
->out_fence
);
381 spin_unlock_irqrestore(&wb_connector
->job_lock
, flags
);
386 INIT_WORK(&job
->cleanup_work
, cleanup_work
);
387 queue_work(system_long_wq
, &job
->cleanup_work
);
389 EXPORT_SYMBOL(drm_writeback_signal_completion
);
392 drm_writeback_get_out_fence(struct drm_writeback_connector
*wb_connector
)
394 struct dma_fence
*fence
;
396 if (WARN_ON(wb_connector
->base
.connector_type
!=
397 DRM_MODE_CONNECTOR_WRITEBACK
))
400 fence
= kzalloc(sizeof(*fence
), GFP_KERNEL
);
404 dma_fence_init(fence
, &drm_writeback_fence_ops
,
405 &wb_connector
->fence_lock
, wb_connector
->fence_context
,
406 ++wb_connector
->fence_seqno
);
410 EXPORT_SYMBOL(drm_writeback_get_out_fence
);