xref: /linux/drivers/gpu/drm/drm_gem_atomic_helper.c (revision b92dd11725a7c57f55e148c7d3ce58a86f480575)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 
3 #include <linux/dma-resv.h>
4 #include <linux/dma-fence-chain.h>
5 
6 #include <drm/drm_atomic_state_helper.h>
7 #include <drm/drm_atomic_uapi.h>
8 #include <drm/drm_framebuffer.h>
9 #include <drm/drm_gem.h>
10 #include <drm/drm_gem_atomic_helper.h>
11 #include <drm/drm_gem_framebuffer_helper.h>
12 #include <drm/drm_simple_kms_helper.h>
13 
14 #include "drm_internal.h"
15 
16 /**
17  * DOC: overview
18  *
19  * The GEM atomic helpers library implements generic atomic-commit
20  * functions for drivers that use GEM objects. Currently, it provides
21  * synchronization helpers, and plane state and framebuffer BO mappings
22  * for planes with shadow buffers.
23  *
24  * Before scanout, a plane's framebuffer needs to be synchronized with
25  * possible writers that draw into the framebuffer. All drivers should
26  * call drm_gem_plane_helper_prepare_fb() from their implementation of
27  * struct &drm_plane_helper.prepare_fb . It sets the plane's fence from
28  * the framebuffer so that the DRM core can synchronize access automatically.
29  *
30  * drm_gem_plane_helper_prepare_fb() can also be used directly as
31  * implementation of prepare_fb. For drivers based on
32  * struct drm_simple_display_pipe, drm_gem_simple_display_pipe_prepare_fb()
33  * provides equivalent functionality.
34  *
35  * .. code-block:: c
36  *
37  *	#include <drm/drm_gem_atomic_helper.h>
38  *
39  *	struct drm_plane_helper_funcs driver_plane_helper_funcs = {
40  *		...,
41  *		. prepare_fb = drm_gem_plane_helper_prepare_fb,
42  *	};
43  *
44  *	struct drm_simple_display_pipe_funcs driver_pipe_funcs = {
45  *		...,
46  *		. prepare_fb = drm_gem_simple_display_pipe_prepare_fb,
47  *	};
48  *
49  * A driver using a shadow buffer copies the content of the shadow buffers
50  * into the HW's framebuffer memory during an atomic update. This requires
51  * a mapping of the shadow buffer into kernel address space. The mappings
52  * cannot be established by commit-tail functions, such as atomic_update,
53  * as this would violate locking rules around dma_buf_vmap().
54  *
55  * The helpers for shadow-buffered planes establish and release mappings,
56  * and provide struct drm_shadow_plane_state, which stores the plane's mapping
57  * for commit-tail functions.
58  *
59  * Shadow-buffered planes can easily be enabled by using the provided macros
60  * %DRM_GEM_SHADOW_PLANE_FUNCS and %DRM_GEM_SHADOW_PLANE_HELPER_FUNCS.
61  * These macros set up the plane and plane-helper callbacks to point to the
62  * shadow-buffer helpers.
63  *
64  * .. code-block:: c
65  *
66  *	#include <drm/drm_gem_atomic_helper.h>
67  *
68  *	struct drm_plane_funcs driver_plane_funcs = {
69  *		...,
70  *		DRM_GEM_SHADOW_PLANE_FUNCS,
71  *	};
72  *
73  *	struct drm_plane_helper_funcs driver_plane_helper_funcs = {
74  *		...,
75  *		DRM_GEM_SHADOW_PLANE_HELPER_FUNCS,
76  *	};
77  *
78  * In the driver's atomic-update function, shadow-buffer mappings are available
79  * from the plane state. Use to_drm_shadow_plane_state() to upcast from
80  * struct drm_plane_state.
81  *
82  * .. code-block:: c
83  *
84  *	void driver_plane_atomic_update(struct drm_plane *plane,
85  *					struct drm_plane_state *old_plane_state)
86  *	{
87  *		struct drm_plane_state *plane_state = plane->state;
88  *		struct drm_shadow_plane_state *shadow_plane_state =
89  *			to_drm_shadow_plane_state(plane_state);
90  *
91  *		// access shadow buffer via shadow_plane_state->map
92  *	}
93  *
94  * A mapping address for each of the framebuffer's buffer object is stored in
95  * struct &drm_shadow_plane_state.map. The mappings are valid while the state
96  * is being used.
97  *
98  * Drivers that use struct drm_simple_display_pipe can use
99  * %DRM_GEM_SIMPLE_DISPLAY_PIPE_SHADOW_PLANE_FUNCS to initialize the rsp
100  * callbacks. Access to shadow-buffer mappings is similar to regular
101  * atomic_update.
102  *
103  * .. code-block:: c
104  *
105  *	struct drm_simple_display_pipe_funcs driver_pipe_funcs = {
106  *		...,
107  *		DRM_GEM_SIMPLE_DISPLAY_PIPE_SHADOW_PLANE_FUNCS,
108  *	};
109  *
110  *	void driver_pipe_enable(struct drm_simple_display_pipe *pipe,
111  *				struct drm_crtc_state *crtc_state,
112  *				struct drm_plane_state *plane_state)
113  *	{
114  *		struct drm_shadow_plane_state *shadow_plane_state =
115  *			to_drm_shadow_plane_state(plane_state);
116  *
117  *		// access shadow buffer via shadow_plane_state->map
118  *	}
119  */
120 
121 /*
122  * Plane Helpers
123  */
124 
125 /**
126  * drm_gem_plane_helper_prepare_fb() - Prepare a GEM backed framebuffer
127  * @plane: Plane
128  * @state: Plane state the fence will be attached to
129  *
130  * This function extracts the exclusive fence from &drm_gem_object.resv and
131  * attaches it to plane state for the atomic helper to wait on. This is
132  * necessary to correctly implement implicit synchronization for any buffers
133  * shared as a struct &dma_buf. This function can be used as the
134  * &drm_plane_helper_funcs.prepare_fb callback.
135  *
136  * There is no need for &drm_plane_helper_funcs.cleanup_fb hook for simple
137  * GEM based framebuffer drivers which have their buffers always pinned in
138  * memory.
139  *
140  * This function is the default implementation for GEM drivers of
141  * &drm_plane_helper_funcs.prepare_fb if no callback is provided.
142  */
143 int drm_gem_plane_helper_prepare_fb(struct drm_plane *plane,
144 				    struct drm_plane_state *state)
145 {
146 	struct dma_fence *fence = dma_fence_get(state->fence);
147 	enum dma_resv_usage usage;
148 	size_t i;
149 	int ret;
150 
151 	if (!state->fb)
152 		return 0;
153 
154 	/*
155 	 * Only add the kernel fences here if there is already a fence set via
156 	 * explicit fencing interfaces on the atomic ioctl.
157 	 *
158 	 * This way explicit fencing can be used to overrule implicit fencing,
159 	 * which is important to make explicit fencing use-cases work: One
160 	 * example is using one buffer for 2 screens with different refresh
161 	 * rates. Implicit fencing will clamp rendering to the refresh rate of
162 	 * the slower screen, whereas explicit fence allows 2 independent
163 	 * render and display loops on a single buffer. If a driver allows
164 	 * obeys both implicit and explicit fences for plane updates, then it
165 	 * will break all the benefits of explicit fencing.
166 	 */
167 	usage = fence ? DMA_RESV_USAGE_KERNEL : DMA_RESV_USAGE_WRITE;
168 
169 	for (i = 0; i < state->fb->format->num_planes; ++i) {
170 		struct drm_gem_object *obj = drm_gem_fb_get_obj(state->fb, i);
171 		struct dma_fence *new;
172 
173 		if (!obj) {
174 			ret = -EINVAL;
175 			goto error;
176 		}
177 
178 		ret = dma_resv_get_singleton(obj->resv, usage, &new);
179 		if (ret)
180 			goto error;
181 
182 		if (new && fence) {
183 			struct dma_fence_chain *chain = dma_fence_chain_alloc();
184 
185 			if (!chain) {
186 				ret = -ENOMEM;
187 				goto error;
188 			}
189 
190 			dma_fence_chain_init(chain, fence, new, 1);
191 			fence = &chain->base;
192 
193 		} else if (new) {
194 			fence = new;
195 		}
196 	}
197 
198 	dma_fence_put(state->fence);
199 	state->fence = fence;
200 	return 0;
201 
202 error:
203 	dma_fence_put(fence);
204 	return ret;
205 }
206 EXPORT_SYMBOL_GPL(drm_gem_plane_helper_prepare_fb);
207 
208 /**
209  * drm_gem_simple_display_pipe_prepare_fb - prepare_fb helper for &drm_simple_display_pipe
210  * @pipe: Simple display pipe
211  * @plane_state: Plane state
212  *
213  * This function uses drm_gem_plane_helper_prepare_fb() to extract the fences
214  * from &drm_gem_object.resv and attaches them to the plane state for the atomic
215  * helper to wait on. This is necessary to correctly implement implicit
216  * synchronization for any buffers shared as a struct &dma_buf. Drivers can use
217  * this as their &drm_simple_display_pipe_funcs.prepare_fb callback.
218  *
219  * See drm_gem_plane_helper_prepare_fb() for a discussion of implicit and
220  * explicit fencing in atomic modeset updates.
221  */
222 int drm_gem_simple_display_pipe_prepare_fb(struct drm_simple_display_pipe *pipe,
223 					   struct drm_plane_state *plane_state)
224 {
225 	return drm_gem_plane_helper_prepare_fb(&pipe->plane, plane_state);
226 }
227 EXPORT_SYMBOL(drm_gem_simple_display_pipe_prepare_fb);
228 
229 /*
230  * Shadow-buffered Planes
231  */
232 
233 /**
234  * __drm_gem_duplicate_shadow_plane_state - duplicates shadow-buffered plane state
235  * @plane: the plane
236  * @new_shadow_plane_state: the new shadow-buffered plane state
237  *
238  * This function duplicates shadow-buffered plane state. This is helpful for drivers
239  * that subclass struct drm_shadow_plane_state.
240  *
241  * The function does not duplicate existing mappings of the shadow buffers.
242  * Mappings are maintained during the atomic commit by the plane's prepare_fb
243  * and cleanup_fb helpers. See drm_gem_prepare_shadow_fb() and drm_gem_cleanup_shadow_fb()
244  * for corresponding helpers.
245  */
246 void
247 __drm_gem_duplicate_shadow_plane_state(struct drm_plane *plane,
248 				       struct drm_shadow_plane_state *new_shadow_plane_state)
249 {
250 	__drm_atomic_helper_plane_duplicate_state(plane, &new_shadow_plane_state->base);
251 }
252 EXPORT_SYMBOL(__drm_gem_duplicate_shadow_plane_state);
253 
254 /**
255  * drm_gem_duplicate_shadow_plane_state - duplicates shadow-buffered plane state
256  * @plane: the plane
257  *
258  * This function implements struct &drm_plane_funcs.atomic_duplicate_state for
259  * shadow-buffered planes. It assumes the existing state to be of type
260  * struct drm_shadow_plane_state and it allocates the new state to be of this
261  * type.
262  *
263  * The function does not duplicate existing mappings of the shadow buffers.
264  * Mappings are maintained during the atomic commit by the plane's prepare_fb
265  * and cleanup_fb helpers. See drm_gem_prepare_shadow_fb() and drm_gem_cleanup_shadow_fb()
266  * for corresponding helpers.
267  *
268  * Returns:
269  * A pointer to a new plane state on success, or NULL otherwise.
270  */
271 struct drm_plane_state *
272 drm_gem_duplicate_shadow_plane_state(struct drm_plane *plane)
273 {
274 	struct drm_plane_state *plane_state = plane->state;
275 	struct drm_shadow_plane_state *new_shadow_plane_state;
276 
277 	if (!plane_state)
278 		return NULL;
279 
280 	new_shadow_plane_state = kzalloc(sizeof(*new_shadow_plane_state), GFP_KERNEL);
281 	if (!new_shadow_plane_state)
282 		return NULL;
283 	__drm_gem_duplicate_shadow_plane_state(plane, new_shadow_plane_state);
284 
285 	return &new_shadow_plane_state->base;
286 }
287 EXPORT_SYMBOL(drm_gem_duplicate_shadow_plane_state);
288 
289 /**
290  * __drm_gem_destroy_shadow_plane_state - cleans up shadow-buffered plane state
291  * @shadow_plane_state: the shadow-buffered plane state
292  *
293  * This function cleans up shadow-buffered plane state. Helpful for drivers that
294  * subclass struct drm_shadow_plane_state.
295  */
296 void __drm_gem_destroy_shadow_plane_state(struct drm_shadow_plane_state *shadow_plane_state)
297 {
298 	__drm_atomic_helper_plane_destroy_state(&shadow_plane_state->base);
299 }
300 EXPORT_SYMBOL(__drm_gem_destroy_shadow_plane_state);
301 
302 /**
303  * drm_gem_destroy_shadow_plane_state - deletes shadow-buffered plane state
304  * @plane: the plane
305  * @plane_state: the plane state of type struct drm_shadow_plane_state
306  *
307  * This function implements struct &drm_plane_funcs.atomic_destroy_state
308  * for shadow-buffered planes. It expects that mappings of shadow buffers
309  * have been released already.
310  */
311 void drm_gem_destroy_shadow_plane_state(struct drm_plane *plane,
312 					struct drm_plane_state *plane_state)
313 {
314 	struct drm_shadow_plane_state *shadow_plane_state =
315 		to_drm_shadow_plane_state(plane_state);
316 
317 	__drm_gem_destroy_shadow_plane_state(shadow_plane_state);
318 	kfree(shadow_plane_state);
319 }
320 EXPORT_SYMBOL(drm_gem_destroy_shadow_plane_state);
321 
322 /**
323  * __drm_gem_reset_shadow_plane - resets a shadow-buffered plane
324  * @plane: the plane
325  * @shadow_plane_state: the shadow-buffered plane state
326  *
327  * This function resets state for shadow-buffered planes. Helpful
328  * for drivers that subclass struct drm_shadow_plane_state.
329  */
330 void __drm_gem_reset_shadow_plane(struct drm_plane *plane,
331 				  struct drm_shadow_plane_state *shadow_plane_state)
332 {
333 	__drm_atomic_helper_plane_reset(plane, &shadow_plane_state->base);
334 }
335 EXPORT_SYMBOL(__drm_gem_reset_shadow_plane);
336 
337 /**
338  * drm_gem_reset_shadow_plane - resets a shadow-buffered plane
339  * @plane: the plane
340  *
341  * This function implements struct &drm_plane_funcs.reset_plane for
342  * shadow-buffered planes. It assumes the current plane state to be
343  * of type struct drm_shadow_plane and it allocates the new state of
344  * this type.
345  */
346 void drm_gem_reset_shadow_plane(struct drm_plane *plane)
347 {
348 	struct drm_shadow_plane_state *shadow_plane_state;
349 
350 	if (plane->state) {
351 		drm_gem_destroy_shadow_plane_state(plane, plane->state);
352 		plane->state = NULL; /* must be set to NULL here */
353 	}
354 
355 	shadow_plane_state = kzalloc(sizeof(*shadow_plane_state), GFP_KERNEL);
356 	if (!shadow_plane_state)
357 		return;
358 	__drm_gem_reset_shadow_plane(plane, shadow_plane_state);
359 }
360 EXPORT_SYMBOL(drm_gem_reset_shadow_plane);
361 
362 /**
363  * drm_gem_prepare_shadow_fb - prepares shadow framebuffers
364  * @plane: the plane
365  * @plane_state: the plane state of type struct drm_shadow_plane_state
366  *
367  * This function implements struct &drm_plane_helper_funcs.prepare_fb. It
368  * maps all buffer objects of the plane's framebuffer into kernel address
369  * space and stores them in &struct drm_shadow_plane_state.map. The
370  * framebuffer will be synchronized as part of the atomic commit.
371  *
372  * See drm_gem_cleanup_shadow_fb() for cleanup.
373  *
374  * Returns:
375  * 0 on success, or a negative errno code otherwise.
376  */
377 int drm_gem_prepare_shadow_fb(struct drm_plane *plane, struct drm_plane_state *plane_state)
378 {
379 	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(plane_state);
380 	struct drm_framebuffer *fb = plane_state->fb;
381 	int ret;
382 
383 	if (!fb)
384 		return 0;
385 
386 	ret = drm_gem_plane_helper_prepare_fb(plane, plane_state);
387 	if (ret)
388 		return ret;
389 
390 	return drm_gem_fb_vmap(fb, shadow_plane_state->map, shadow_plane_state->data);
391 }
392 EXPORT_SYMBOL(drm_gem_prepare_shadow_fb);
393 
394 /**
395  * drm_gem_cleanup_shadow_fb - releases shadow framebuffers
396  * @plane: the plane
397  * @plane_state: the plane state of type struct drm_shadow_plane_state
398  *
399  * This function implements struct &drm_plane_helper_funcs.cleanup_fb.
400  * This function unmaps all buffer objects of the plane's framebuffer.
401  *
402  * See drm_gem_prepare_shadow_fb() for more information.
403  */
404 void drm_gem_cleanup_shadow_fb(struct drm_plane *plane, struct drm_plane_state *plane_state)
405 {
406 	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(plane_state);
407 	struct drm_framebuffer *fb = plane_state->fb;
408 
409 	if (!fb)
410 		return;
411 
412 	drm_gem_fb_vunmap(fb, shadow_plane_state->map);
413 }
414 EXPORT_SYMBOL(drm_gem_cleanup_shadow_fb);
415 
416 /**
417  * drm_gem_simple_kms_prepare_shadow_fb - prepares shadow framebuffers
418  * @pipe: the simple display pipe
419  * @plane_state: the plane state of type struct drm_shadow_plane_state
420  *
421  * This function implements struct drm_simple_display_funcs.prepare_fb. It
422  * maps all buffer objects of the plane's framebuffer into kernel address
423  * space and stores them in struct drm_shadow_plane_state.map. The
424  * framebuffer will be synchronized as part of the atomic commit.
425  *
426  * See drm_gem_simple_kms_cleanup_shadow_fb() for cleanup.
427  *
428  * Returns:
429  * 0 on success, or a negative errno code otherwise.
430  */
431 int drm_gem_simple_kms_prepare_shadow_fb(struct drm_simple_display_pipe *pipe,
432 					 struct drm_plane_state *plane_state)
433 {
434 	return drm_gem_prepare_shadow_fb(&pipe->plane, plane_state);
435 }
436 EXPORT_SYMBOL(drm_gem_simple_kms_prepare_shadow_fb);
437 
438 /**
439  * drm_gem_simple_kms_cleanup_shadow_fb - releases shadow framebuffers
440  * @pipe: the simple display pipe
441  * @plane_state: the plane state of type struct drm_shadow_plane_state
442  *
443  * This function implements struct drm_simple_display_funcs.cleanup_fb.
444  * This function unmaps all buffer objects of the plane's framebuffer.
445  *
446  * See drm_gem_simple_kms_prepare_shadow_fb().
447  */
448 void drm_gem_simple_kms_cleanup_shadow_fb(struct drm_simple_display_pipe *pipe,
449 					  struct drm_plane_state *plane_state)
450 {
451 	drm_gem_cleanup_shadow_fb(&pipe->plane, plane_state);
452 }
453 EXPORT_SYMBOL(drm_gem_simple_kms_cleanup_shadow_fb);
454 
455 /**
456  * drm_gem_simple_kms_reset_shadow_plane - resets a shadow-buffered plane
457  * @pipe: the simple display pipe
458  *
459  * This function implements struct drm_simple_display_funcs.reset_plane
460  * for shadow-buffered planes.
461  */
462 void drm_gem_simple_kms_reset_shadow_plane(struct drm_simple_display_pipe *pipe)
463 {
464 	drm_gem_reset_shadow_plane(&pipe->plane);
465 }
466 EXPORT_SYMBOL(drm_gem_simple_kms_reset_shadow_plane);
467 
468 /**
469  * drm_gem_simple_kms_duplicate_shadow_plane_state - duplicates shadow-buffered plane state
470  * @pipe: the simple display pipe
471  *
472  * This function implements struct drm_simple_display_funcs.duplicate_plane_state
473  * for shadow-buffered planes. It does not duplicate existing mappings of the shadow
474  * buffers. Mappings are maintained during the atomic commit by the plane's prepare_fb
475  * and cleanup_fb helpers.
476  *
477  * Returns:
478  * A pointer to a new plane state on success, or NULL otherwise.
479  */
480 struct drm_plane_state *
481 drm_gem_simple_kms_duplicate_shadow_plane_state(struct drm_simple_display_pipe *pipe)
482 {
483 	return drm_gem_duplicate_shadow_plane_state(&pipe->plane);
484 }
485 EXPORT_SYMBOL(drm_gem_simple_kms_duplicate_shadow_plane_state);
486 
487 /**
488  * drm_gem_simple_kms_destroy_shadow_plane_state - resets shadow-buffered plane state
489  * @pipe: the simple display pipe
490  * @plane_state: the plane state of type struct drm_shadow_plane_state
491  *
492  * This function implements struct drm_simple_display_funcs.destroy_plane_state
493  * for shadow-buffered planes. It expects that mappings of shadow buffers
494  * have been released already.
495  */
496 void drm_gem_simple_kms_destroy_shadow_plane_state(struct drm_simple_display_pipe *pipe,
497 						   struct drm_plane_state *plane_state)
498 {
499 	drm_gem_destroy_shadow_plane_state(&pipe->plane, plane_state);
500 }
501 EXPORT_SYMBOL(drm_gem_simple_kms_destroy_shadow_plane_state);
502