summaryrefslogtreecommitdiff
path: root/drivers/gpu/drm/drm_gem_atomic_helper.c
blob: 5d4b9cd077f7a621f01718eea37359927c8965c7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
// SPDX-License-Identifier: GPL-2.0-or-later

#include <linux/dma-resv.h>
#include <linux/dma-fence-chain.h>

#include <drm/drm_atomic_state_helper.h>
#include <drm/drm_atomic_uapi.h>
#include <drm/drm_framebuffer.h>
#include <drm/drm_gem.h>
#include <drm/drm_gem_atomic_helper.h>
#include <drm/drm_gem_framebuffer_helper.h>
#include <drm/drm_simple_kms_helper.h>

#include "drm_internal.h"

/**
 * DOC: overview
 *
 * The GEM atomic helpers library implements generic atomic-commit
 * functions for drivers that use GEM objects. Currently, it provides
 * synchronization helpers, and plane state and framebuffer BO mappings
 * for planes with shadow buffers.
 *
 * Before scanout, a plane's framebuffer needs to be synchronized with
 * possible writers that draw into the framebuffer. All drivers should
 * call drm_gem_plane_helper_prepare_fb() from their implementation of
 * struct &drm_plane_helper.prepare_fb . It sets the plane's fence from
 * the framebuffer so that the DRM core can synchronize access automatically.
 * drm_gem_plane_helper_prepare_fb() can also be used directly as
 * implementation of prepare_fb.
 *
 * .. code-block:: c
 *
 *	#include <drm/drm_gem_atomic_helper.h>
 *
 *	struct drm_plane_helper_funcs driver_plane_helper_funcs = {
 *		...,
 *		. prepare_fb = drm_gem_plane_helper_prepare_fb,
 *	};
 *
 * A driver using a shadow buffer copies the content of the shadow buffers
 * into the HW's framebuffer memory during an atomic update. This requires
 * a mapping of the shadow buffer into kernel address space. The mappings
 * cannot be established by commit-tail functions, such as atomic_update,
 * as this would violate locking rules around dma_buf_vmap().
 *
 * The helpers for shadow-buffered planes establish and release mappings,
 * and provide struct drm_shadow_plane_state, which stores the plane's mapping
 * for commit-tail functions.
 *
 * Shadow-buffered planes can easily be enabled by using the provided macros
 * %DRM_GEM_SHADOW_PLANE_FUNCS and %DRM_GEM_SHADOW_PLANE_HELPER_FUNCS.
 * These macros set up the plane and plane-helper callbacks to point to the
 * shadow-buffer helpers.
 *
 * .. code-block:: c
 *
 *	#include <drm/drm_gem_atomic_helper.h>
 *
 *	struct drm_plane_funcs driver_plane_funcs = {
 *		...,
 *		DRM_GEM_SHADOW_PLANE_FUNCS,
 *	};
 *
 *	struct drm_plane_helper_funcs driver_plane_helper_funcs = {
 *		...,
 *		DRM_GEM_SHADOW_PLANE_HELPER_FUNCS,
 *	};
 *
 * In the driver's atomic-update function, shadow-buffer mappings are available
 * from the plane state. Use to_drm_shadow_plane_state() to upcast from
 * struct drm_plane_state.
 *
 * .. code-block:: c
 *
 *	void driver_plane_atomic_update(struct drm_plane *plane,
 *					struct drm_plane_state *old_plane_state)
 *	{
 *		struct drm_plane_state *plane_state = plane->state;
 *		struct drm_shadow_plane_state *shadow_plane_state =
 *			to_drm_shadow_plane_state(plane_state);
 *
 *		// access shadow buffer via shadow_plane_state->map
 *	}
 *
 * A mapping address for each of the framebuffer's buffer object is stored in
 * struct &drm_shadow_plane_state.map. The mappings are valid while the state
 * is being used.
 *
 * Drivers that use struct drm_simple_display_pipe can use
 * %DRM_GEM_SIMPLE_DISPLAY_PIPE_SHADOW_PLANE_FUNCS to initialize the rsp
 * callbacks. Access to shadow-buffer mappings is similar to regular
 * atomic_update.
 *
 * .. code-block:: c
 *
 *	struct drm_simple_display_pipe_funcs driver_pipe_funcs = {
 *		...,
 *		DRM_GEM_SIMPLE_DISPLAY_PIPE_SHADOW_PLANE_FUNCS,
 *	};
 *
 *	void driver_pipe_enable(struct drm_simple_display_pipe *pipe,
 *				struct drm_crtc_state *crtc_state,
 *				struct drm_plane_state *plane_state)
 *	{
 *		struct drm_shadow_plane_state *shadow_plane_state =
 *			to_drm_shadow_plane_state(plane_state);
 *
 *		// access shadow buffer via shadow_plane_state->map
 *	}
 */

/*
 * Plane Helpers
 */

/**
 * drm_gem_plane_helper_prepare_fb() - Prepare a GEM backed framebuffer
 * @plane: Plane
 * @state: Plane state the fence will be attached to
 *
 * This function extracts the exclusive fence from &drm_gem_object.resv and
 * attaches it to plane state for the atomic helper to wait on. This is
 * necessary to correctly implement implicit synchronization for any buffers
 * shared as a struct &dma_buf. This function can be used as the
 * &drm_plane_helper_funcs.prepare_fb callback.
 *
 * There is no need for &drm_plane_helper_funcs.cleanup_fb hook for simple
 * GEM based framebuffer drivers which have their buffers always pinned in
 * memory.
 *
 * This function is the default implementation for GEM drivers of
 * &drm_plane_helper_funcs.prepare_fb if no callback is provided.
 */
int drm_gem_plane_helper_prepare_fb(struct drm_plane *plane,
				    struct drm_plane_state *state)
{
	struct dma_fence *fence = dma_fence_get(state->fence);
	enum dma_resv_usage usage;
	size_t i;
	int ret;

	if (!state->fb)
		return 0;

	/*
	 * Only add the kernel fences here if there is already a fence set via
	 * explicit fencing interfaces on the atomic ioctl.
	 *
	 * This way explicit fencing can be used to overrule implicit fencing,
	 * which is important to make explicit fencing use-cases work: One
	 * example is using one buffer for 2 screens with different refresh
	 * rates. Implicit fencing will clamp rendering to the refresh rate of
	 * the slower screen, whereas explicit fence allows 2 independent
	 * render and display loops on a single buffer. If a driver allows
	 * obeys both implicit and explicit fences for plane updates, then it
	 * will break all the benefits of explicit fencing.
	 */
	usage = fence ? DMA_RESV_USAGE_KERNEL : DMA_RESV_USAGE_WRITE;

	for (i = 0; i < state->fb->format->num_planes; ++i) {
		struct drm_gem_object *obj = drm_gem_fb_get_obj(state->fb, i);
		struct dma_fence *new;

		if (!obj) {
			ret = -EINVAL;
			goto error;
		}

		ret = dma_resv_get_singleton(obj->resv, usage, &new);
		if (ret)
			goto error;

		if (new && fence) {
			struct dma_fence_chain *chain = dma_fence_chain_alloc();

			if (!chain) {
				ret = -ENOMEM;
				goto error;
			}

			dma_fence_chain_init(chain, fence, new, 1);
			fence = &chain->base;

		} else if (new) {
			fence = new;
		}
	}

	dma_fence_put(state->fence);
	state->fence = fence;
	return 0;

error:
	dma_fence_put(fence);
	return ret;
}
EXPORT_SYMBOL_GPL(drm_gem_plane_helper_prepare_fb);

/*
 * Shadow-buffered Planes
 */

/**
 * __drm_gem_duplicate_shadow_plane_state - duplicates shadow-buffered plane state
 * @plane: the plane
 * @new_shadow_plane_state: the new shadow-buffered plane state
 *
 * This function duplicates shadow-buffered plane state. This is helpful for drivers
 * that subclass struct drm_shadow_plane_state.
 *
 * The function does not duplicate existing mappings of the shadow buffers.
 * Mappings are maintained during the atomic commit by the plane's prepare_fb
 * and cleanup_fb helpers. See drm_gem_prepare_shadow_fb() and drm_gem_cleanup_shadow_fb()
 * for corresponding helpers.
 */
void
__drm_gem_duplicate_shadow_plane_state(struct drm_plane *plane,
				       struct drm_shadow_plane_state *new_shadow_plane_state)
{
	__drm_atomic_helper_plane_duplicate_state(plane, &new_shadow_plane_state->base);
}
EXPORT_SYMBOL(__drm_gem_duplicate_shadow_plane_state);

/**
 * drm_gem_duplicate_shadow_plane_state - duplicates shadow-buffered plane state
 * @plane: the plane
 *
 * This function implements struct &drm_plane_funcs.atomic_duplicate_state for
 * shadow-buffered planes. It assumes the existing state to be of type
 * struct drm_shadow_plane_state and it allocates the new state to be of this
 * type.
 *
 * The function does not duplicate existing mappings of the shadow buffers.
 * Mappings are maintained during the atomic commit by the plane's prepare_fb
 * and cleanup_fb helpers. See drm_gem_prepare_shadow_fb() and drm_gem_cleanup_shadow_fb()
 * for corresponding helpers.
 *
 * Returns:
 * A pointer to a new plane state on success, or NULL otherwise.
 */
struct drm_plane_state *
drm_gem_duplicate_shadow_plane_state(struct drm_plane *plane)
{
	struct drm_plane_state *plane_state = plane->state;
	struct drm_shadow_plane_state *new_shadow_plane_state;

	if (!plane_state)
		return NULL;

	new_shadow_plane_state = kzalloc(sizeof(*new_shadow_plane_state), GFP_KERNEL);
	if (!new_shadow_plane_state)
		return NULL;
	__drm_gem_duplicate_shadow_plane_state(plane, new_shadow_plane_state);

	return &new_shadow_plane_state->base;
}
EXPORT_SYMBOL(drm_gem_duplicate_shadow_plane_state);

/**
 * __drm_gem_destroy_shadow_plane_state - cleans up shadow-buffered plane state
 * @shadow_plane_state: the shadow-buffered plane state
 *
 * This function cleans up shadow-buffered plane state. Helpful for drivers that
 * subclass struct drm_shadow_plane_state.
 */
void __drm_gem_destroy_shadow_plane_state(struct drm_shadow_plane_state *shadow_plane_state)
{
	__drm_atomic_helper_plane_destroy_state(&shadow_plane_state->base);
}
EXPORT_SYMBOL(__drm_gem_destroy_shadow_plane_state);

/**
 * drm_gem_destroy_shadow_plane_state - deletes shadow-buffered plane state
 * @plane: the plane
 * @plane_state: the plane state of type struct drm_shadow_plane_state
 *
 * This function implements struct &drm_plane_funcs.atomic_destroy_state
 * for shadow-buffered planes. It expects that mappings of shadow buffers
 * have been released already.
 */
void drm_gem_destroy_shadow_plane_state(struct drm_plane *plane,
					struct drm_plane_state *plane_state)
{
	struct drm_shadow_plane_state *shadow_plane_state =
		to_drm_shadow_plane_state(plane_state);

	__drm_gem_destroy_shadow_plane_state(shadow_plane_state);
	kfree(shadow_plane_state);
}
EXPORT_SYMBOL(drm_gem_destroy_shadow_plane_state);

/**
 * __drm_gem_reset_shadow_plane - resets a shadow-buffered plane
 * @plane: the plane
 * @shadow_plane_state: the shadow-buffered plane state
 *
 * This function resets state for shadow-buffered planes. Helpful
 * for drivers that subclass struct drm_shadow_plane_state.
 */
void __drm_gem_reset_shadow_plane(struct drm_plane *plane,
				  struct drm_shadow_plane_state *shadow_plane_state)
{
	__drm_atomic_helper_plane_reset(plane, &shadow_plane_state->base);
}
EXPORT_SYMBOL(__drm_gem_reset_shadow_plane);

/**
 * drm_gem_reset_shadow_plane - resets a shadow-buffered plane
 * @plane: the plane
 *
 * This function implements struct &drm_plane_funcs.reset_plane for
 * shadow-buffered planes. It assumes the current plane state to be
 * of type struct drm_shadow_plane and it allocates the new state of
 * this type.
 */
void drm_gem_reset_shadow_plane(struct drm_plane *plane)
{
	struct drm_shadow_plane_state *shadow_plane_state;

	if (plane->state) {
		drm_gem_destroy_shadow_plane_state(plane, plane->state);
		plane->state = NULL; /* must be set to NULL here */
	}

	shadow_plane_state = kzalloc(sizeof(*shadow_plane_state), GFP_KERNEL);
	if (!shadow_plane_state)
		return;
	__drm_gem_reset_shadow_plane(plane, shadow_plane_state);
}
EXPORT_SYMBOL(drm_gem_reset_shadow_plane);

/**
 * drm_gem_begin_shadow_fb_access - prepares shadow framebuffers for CPU access
 * @plane: the plane
 * @plane_state: the plane state of type struct drm_shadow_plane_state
 *
 * This function implements struct &drm_plane_helper_funcs.begin_fb_access. It
 * maps all buffer objects of the plane's framebuffer into kernel address
 * space and stores them in struct &drm_shadow_plane_state.map. The first data
 * bytes are available in struct &drm_shadow_plane_state.data.
 *
 * See drm_gem_end_shadow_fb_access() for cleanup.
 *
 * Returns:
 * 0 on success, or a negative errno code otherwise.
 */
int drm_gem_begin_shadow_fb_access(struct drm_plane *plane, struct drm_plane_state *plane_state)
{
	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(plane_state);
	struct drm_framebuffer *fb = plane_state->fb;

	if (!fb)
		return 0;

	return drm_gem_fb_vmap(fb, shadow_plane_state->map, shadow_plane_state->data);
}
EXPORT_SYMBOL(drm_gem_begin_shadow_fb_access);

/**
 * drm_gem_end_shadow_fb_access - releases shadow framebuffers from CPU access
 * @plane: the plane
 * @plane_state: the plane state of type struct drm_shadow_plane_state
 *
 * This function implements struct &drm_plane_helper_funcs.end_fb_access. It
 * undoes all effects of drm_gem_begin_shadow_fb_access() in reverse order.
 *
 * See drm_gem_begin_shadow_fb_access() for more information.
 */
void drm_gem_end_shadow_fb_access(struct drm_plane *plane, struct drm_plane_state *plane_state)
{
	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(plane_state);
	struct drm_framebuffer *fb = plane_state->fb;

	if (!fb)
		return;

	drm_gem_fb_vunmap(fb, shadow_plane_state->map);
}
EXPORT_SYMBOL(drm_gem_end_shadow_fb_access);

/**
 * drm_gem_simple_kms_begin_shadow_fb_access - prepares shadow framebuffers for CPU access
 * @pipe: the simple display pipe
 * @plane_state: the plane state of type struct drm_shadow_plane_state
 *
 * This function implements struct drm_simple_display_funcs.begin_fb_access.
 *
 * See drm_gem_begin_shadow_fb_access() for details and
 * drm_gem_simple_kms_cleanup_shadow_fb() for cleanup.
 *
 * Returns:
 * 0 on success, or a negative errno code otherwise.
 */
int drm_gem_simple_kms_begin_shadow_fb_access(struct drm_simple_display_pipe *pipe,
					      struct drm_plane_state *plane_state)
{
	return drm_gem_begin_shadow_fb_access(&pipe->plane, plane_state);
}
EXPORT_SYMBOL(drm_gem_simple_kms_begin_shadow_fb_access);

/**
 * drm_gem_simple_kms_end_shadow_fb_access - releases shadow framebuffers from CPU access
 * @pipe: the simple display pipe
 * @plane_state: the plane state of type struct drm_shadow_plane_state
 *
 * This function implements struct drm_simple_display_funcs.end_fb_access.
 * It undoes all effects of drm_gem_simple_kms_begin_shadow_fb_access() in
 * reverse order.
 *
 * See drm_gem_simple_kms_begin_shadow_fb_access().
 */
void drm_gem_simple_kms_end_shadow_fb_access(struct drm_simple_display_pipe *pipe,
					     struct drm_plane_state *plane_state)
{
	drm_gem_end_shadow_fb_access(&pipe->plane, plane_state);
}
EXPORT_SYMBOL(drm_gem_simple_kms_end_shadow_fb_access);

/**
 * drm_gem_simple_kms_reset_shadow_plane - resets a shadow-buffered plane
 * @pipe: the simple display pipe
 *
 * This function implements struct drm_simple_display_funcs.reset_plane
 * for shadow-buffered planes.
 */
void drm_gem_simple_kms_reset_shadow_plane(struct drm_simple_display_pipe *pipe)
{
	drm_gem_reset_shadow_plane(&pipe->plane);
}
EXPORT_SYMBOL(drm_gem_simple_kms_reset_shadow_plane);

/**
 * drm_gem_simple_kms_duplicate_shadow_plane_state - duplicates shadow-buffered plane state
 * @pipe: the simple display pipe
 *
 * This function implements struct drm_simple_display_funcs.duplicate_plane_state
 * for shadow-buffered planes. It does not duplicate existing mappings of the shadow
 * buffers. Mappings are maintained during the atomic commit by the plane's prepare_fb
 * and cleanup_fb helpers.
 *
 * Returns:
 * A pointer to a new plane state on success, or NULL otherwise.
 */
struct drm_plane_state *
drm_gem_simple_kms_duplicate_shadow_plane_state(struct drm_simple_display_pipe *pipe)
{
	return drm_gem_duplicate_shadow_plane_state(&pipe->plane);
}
EXPORT_SYMBOL(drm_gem_simple_kms_duplicate_shadow_plane_state);

/**
 * drm_gem_simple_kms_destroy_shadow_plane_state - resets shadow-buffered plane state
 * @pipe: the simple display pipe
 * @plane_state: the plane state of type struct drm_shadow_plane_state
 *
 * This function implements struct drm_simple_display_funcs.destroy_plane_state
 * for shadow-buffered planes. It expects that mappings of shadow buffers
 * have been released already.
 */
void drm_gem_simple_kms_destroy_shadow_plane_state(struct drm_simple_display_pipe *pipe,
						   struct drm_plane_state *plane_state)
{
	drm_gem_destroy_shadow_plane_state(&pipe->plane, plane_state);
}
EXPORT_SYMBOL(drm_gem_simple_kms_destroy_shadow_plane_state);