xref: /linux/drivers/gpu/drm/drm_gem_atomic_helper.c (revision 4232da23d75d173195c6766729e51947b64f83cd)
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  * drm_gem_plane_helper_prepare_fb() can also be used directly as
30  * implementation of prepare_fb.
31  *
32  * .. code-block:: c
33  *
34  *	#include <drm/drm_gem_atomic_helper.h>
35  *
36  *	struct drm_plane_helper_funcs driver_plane_helper_funcs = {
37  *		...,
38  *		. prepare_fb = drm_gem_plane_helper_prepare_fb,
39  *	};
40  *
41  * A driver using a shadow buffer copies the content of the shadow buffers
42  * into the HW's framebuffer memory during an atomic update. This requires
43  * a mapping of the shadow buffer into kernel address space. The mappings
44  * cannot be established by commit-tail functions, such as atomic_update,
45  * as this would violate locking rules around dma_buf_vmap().
46  *
47  * The helpers for shadow-buffered planes establish and release mappings,
48  * and provide struct drm_shadow_plane_state, which stores the plane's mapping
49  * for commit-tail functions.
50  *
51  * Shadow-buffered planes can easily be enabled by using the provided macros
52  * %DRM_GEM_SHADOW_PLANE_FUNCS and %DRM_GEM_SHADOW_PLANE_HELPER_FUNCS.
53  * These macros set up the plane and plane-helper callbacks to point to the
54  * shadow-buffer helpers.
55  *
56  * .. code-block:: c
57  *
58  *	#include <drm/drm_gem_atomic_helper.h>
59  *
60  *	struct drm_plane_funcs driver_plane_funcs = {
61  *		...,
62  *		DRM_GEM_SHADOW_PLANE_FUNCS,
63  *	};
64  *
65  *	struct drm_plane_helper_funcs driver_plane_helper_funcs = {
66  *		...,
67  *		DRM_GEM_SHADOW_PLANE_HELPER_FUNCS,
68  *	};
69  *
70  * In the driver's atomic-update function, shadow-buffer mappings are available
71  * from the plane state. Use to_drm_shadow_plane_state() to upcast from
72  * struct drm_plane_state.
73  *
74  * .. code-block:: c
75  *
76  *	void driver_plane_atomic_update(struct drm_plane *plane,
77  *					struct drm_plane_state *old_plane_state)
78  *	{
79  *		struct drm_plane_state *plane_state = plane->state;
80  *		struct drm_shadow_plane_state *shadow_plane_state =
81  *			to_drm_shadow_plane_state(plane_state);
82  *
83  *		// access shadow buffer via shadow_plane_state->map
84  *	}
85  *
86  * A mapping address for each of the framebuffer's buffer object is stored in
87  * struct &drm_shadow_plane_state.map. The mappings are valid while the state
88  * is being used.
89  *
90  * Drivers that use struct drm_simple_display_pipe can use
91  * %DRM_GEM_SIMPLE_DISPLAY_PIPE_SHADOW_PLANE_FUNCS to initialize the rsp
92  * callbacks. Access to shadow-buffer mappings is similar to regular
93  * atomic_update.
94  *
95  * .. code-block:: c
96  *
97  *	struct drm_simple_display_pipe_funcs driver_pipe_funcs = {
98  *		...,
99  *		DRM_GEM_SIMPLE_DISPLAY_PIPE_SHADOW_PLANE_FUNCS,
100  *	};
101  *
102  *	void driver_pipe_enable(struct drm_simple_display_pipe *pipe,
103  *				struct drm_crtc_state *crtc_state,
104  *				struct drm_plane_state *plane_state)
105  *	{
106  *		struct drm_shadow_plane_state *shadow_plane_state =
107  *			to_drm_shadow_plane_state(plane_state);
108  *
109  *		// access shadow buffer via shadow_plane_state->map
110  *	}
111  */
112 
113 /*
114  * Plane Helpers
115  */
116 
117 /**
118  * drm_gem_plane_helper_prepare_fb() - Prepare a GEM backed framebuffer
119  * @plane: Plane
120  * @state: Plane state the fence will be attached to
121  *
122  * This function extracts the exclusive fence from &drm_gem_object.resv and
123  * attaches it to plane state for the atomic helper to wait on. This is
124  * necessary to correctly implement implicit synchronization for any buffers
125  * shared as a struct &dma_buf. This function can be used as the
126  * &drm_plane_helper_funcs.prepare_fb callback.
127  *
128  * There is no need for &drm_plane_helper_funcs.cleanup_fb hook for simple
129  * GEM based framebuffer drivers which have their buffers always pinned in
130  * memory.
131  *
132  * This function is the default implementation for GEM drivers of
133  * &drm_plane_helper_funcs.prepare_fb if no callback is provided.
134  */
drm_gem_plane_helper_prepare_fb(struct drm_plane * plane,struct drm_plane_state * state)135 int drm_gem_plane_helper_prepare_fb(struct drm_plane *plane,
136 				    struct drm_plane_state *state)
137 {
138 	struct dma_fence *fence = dma_fence_get(state->fence);
139 	enum dma_resv_usage usage;
140 	size_t i;
141 	int ret;
142 
143 	if (!state->fb)
144 		return 0;
145 
146 	/*
147 	 * Only add the kernel fences here if there is already a fence set via
148 	 * explicit fencing interfaces on the atomic ioctl.
149 	 *
150 	 * This way explicit fencing can be used to overrule implicit fencing,
151 	 * which is important to make explicit fencing use-cases work: One
152 	 * example is using one buffer for 2 screens with different refresh
153 	 * rates. Implicit fencing will clamp rendering to the refresh rate of
154 	 * the slower screen, whereas explicit fence allows 2 independent
155 	 * render and display loops on a single buffer. If a driver allows
156 	 * obeys both implicit and explicit fences for plane updates, then it
157 	 * will break all the benefits of explicit fencing.
158 	 */
159 	usage = fence ? DMA_RESV_USAGE_KERNEL : DMA_RESV_USAGE_WRITE;
160 
161 	for (i = 0; i < state->fb->format->num_planes; ++i) {
162 		struct drm_gem_object *obj = drm_gem_fb_get_obj(state->fb, i);
163 		struct dma_fence *new;
164 
165 		if (!obj) {
166 			ret = -EINVAL;
167 			goto error;
168 		}
169 
170 		ret = dma_resv_get_singleton(obj->resv, usage, &new);
171 		if (ret)
172 			goto error;
173 
174 		if (new && fence) {
175 			struct dma_fence_chain *chain = dma_fence_chain_alloc();
176 
177 			if (!chain) {
178 				ret = -ENOMEM;
179 				goto error;
180 			}
181 
182 			dma_fence_chain_init(chain, fence, new, 1);
183 			fence = &chain->base;
184 
185 		} else if (new) {
186 			fence = new;
187 		}
188 	}
189 
190 	dma_fence_put(state->fence);
191 	state->fence = fence;
192 	return 0;
193 
194 error:
195 	dma_fence_put(fence);
196 	return ret;
197 }
198 EXPORT_SYMBOL_GPL(drm_gem_plane_helper_prepare_fb);
199 
200 /*
201  * Shadow-buffered Planes
202  */
203 
204 /**
205  * __drm_gem_duplicate_shadow_plane_state - duplicates shadow-buffered plane state
206  * @plane: the plane
207  * @new_shadow_plane_state: the new shadow-buffered plane state
208  *
209  * This function duplicates shadow-buffered plane state. This is helpful for drivers
210  * that subclass struct drm_shadow_plane_state.
211  *
212  * The function does not duplicate existing mappings of the shadow buffers.
213  * Mappings are maintained during the atomic commit by the plane's prepare_fb
214  * and cleanup_fb helpers. See drm_gem_prepare_shadow_fb() and drm_gem_cleanup_shadow_fb()
215  * for corresponding helpers.
216  */
217 void
__drm_gem_duplicate_shadow_plane_state(struct drm_plane * plane,struct drm_shadow_plane_state * new_shadow_plane_state)218 __drm_gem_duplicate_shadow_plane_state(struct drm_plane *plane,
219 				       struct drm_shadow_plane_state *new_shadow_plane_state)
220 {
221 	struct drm_plane_state *plane_state = plane->state;
222 	struct drm_shadow_plane_state *shadow_plane_state =
223 		to_drm_shadow_plane_state(plane_state);
224 
225 	__drm_atomic_helper_plane_duplicate_state(plane, &new_shadow_plane_state->base);
226 
227 	drm_format_conv_state_copy(&new_shadow_plane_state->fmtcnv_state,
228 				   &shadow_plane_state->fmtcnv_state);
229 }
230 EXPORT_SYMBOL(__drm_gem_duplicate_shadow_plane_state);
231 
232 /**
233  * drm_gem_duplicate_shadow_plane_state - duplicates shadow-buffered plane state
234  * @plane: the plane
235  *
236  * This function implements struct &drm_plane_funcs.atomic_duplicate_state for
237  * shadow-buffered planes. It assumes the existing state to be of type
238  * struct drm_shadow_plane_state and it allocates the new state to be of this
239  * type.
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  * Returns:
247  * A pointer to a new plane state on success, or NULL otherwise.
248  */
249 struct drm_plane_state *
drm_gem_duplicate_shadow_plane_state(struct drm_plane * plane)250 drm_gem_duplicate_shadow_plane_state(struct drm_plane *plane)
251 {
252 	struct drm_plane_state *plane_state = plane->state;
253 	struct drm_shadow_plane_state *new_shadow_plane_state;
254 
255 	if (!plane_state)
256 		return NULL;
257 
258 	new_shadow_plane_state = kzalloc(sizeof(*new_shadow_plane_state), GFP_KERNEL);
259 	if (!new_shadow_plane_state)
260 		return NULL;
261 	__drm_gem_duplicate_shadow_plane_state(plane, new_shadow_plane_state);
262 
263 	return &new_shadow_plane_state->base;
264 }
265 EXPORT_SYMBOL(drm_gem_duplicate_shadow_plane_state);
266 
267 /**
268  * __drm_gem_destroy_shadow_plane_state - cleans up shadow-buffered plane state
269  * @shadow_plane_state: the shadow-buffered plane state
270  *
271  * This function cleans up shadow-buffered plane state. Helpful for drivers that
272  * subclass struct drm_shadow_plane_state.
273  */
__drm_gem_destroy_shadow_plane_state(struct drm_shadow_plane_state * shadow_plane_state)274 void __drm_gem_destroy_shadow_plane_state(struct drm_shadow_plane_state *shadow_plane_state)
275 {
276 	drm_format_conv_state_release(&shadow_plane_state->fmtcnv_state);
277 	__drm_atomic_helper_plane_destroy_state(&shadow_plane_state->base);
278 }
279 EXPORT_SYMBOL(__drm_gem_destroy_shadow_plane_state);
280 
281 /**
282  * drm_gem_destroy_shadow_plane_state - deletes shadow-buffered plane state
283  * @plane: the plane
284  * @plane_state: the plane state of type struct drm_shadow_plane_state
285  *
286  * This function implements struct &drm_plane_funcs.atomic_destroy_state
287  * for shadow-buffered planes. It expects that mappings of shadow buffers
288  * have been released already.
289  */
drm_gem_destroy_shadow_plane_state(struct drm_plane * plane,struct drm_plane_state * plane_state)290 void drm_gem_destroy_shadow_plane_state(struct drm_plane *plane,
291 					struct drm_plane_state *plane_state)
292 {
293 	struct drm_shadow_plane_state *shadow_plane_state =
294 		to_drm_shadow_plane_state(plane_state);
295 
296 	__drm_gem_destroy_shadow_plane_state(shadow_plane_state);
297 	kfree(shadow_plane_state);
298 }
299 EXPORT_SYMBOL(drm_gem_destroy_shadow_plane_state);
300 
301 /**
302  * __drm_gem_reset_shadow_plane - resets a shadow-buffered plane
303  * @plane: the plane
304  * @shadow_plane_state: the shadow-buffered plane state
305  *
306  * This function resets state for shadow-buffered planes. Helpful
307  * for drivers that subclass struct drm_shadow_plane_state.
308  */
__drm_gem_reset_shadow_plane(struct drm_plane * plane,struct drm_shadow_plane_state * shadow_plane_state)309 void __drm_gem_reset_shadow_plane(struct drm_plane *plane,
310 				  struct drm_shadow_plane_state *shadow_plane_state)
311 {
312 	__drm_atomic_helper_plane_reset(plane, &shadow_plane_state->base);
313 	drm_format_conv_state_init(&shadow_plane_state->fmtcnv_state);
314 }
315 EXPORT_SYMBOL(__drm_gem_reset_shadow_plane);
316 
317 /**
318  * drm_gem_reset_shadow_plane - resets a shadow-buffered plane
319  * @plane: the plane
320  *
321  * This function implements struct &drm_plane_funcs.reset_plane for
322  * shadow-buffered planes. It assumes the current plane state to be
323  * of type struct drm_shadow_plane and it allocates the new state of
324  * this type.
325  */
drm_gem_reset_shadow_plane(struct drm_plane * plane)326 void drm_gem_reset_shadow_plane(struct drm_plane *plane)
327 {
328 	struct drm_shadow_plane_state *shadow_plane_state;
329 
330 	if (plane->state) {
331 		drm_gem_destroy_shadow_plane_state(plane, plane->state);
332 		plane->state = NULL; /* must be set to NULL here */
333 	}
334 
335 	shadow_plane_state = kzalloc(sizeof(*shadow_plane_state), GFP_KERNEL);
336 	if (!shadow_plane_state)
337 		return;
338 	__drm_gem_reset_shadow_plane(plane, shadow_plane_state);
339 }
340 EXPORT_SYMBOL(drm_gem_reset_shadow_plane);
341 
342 /**
343  * drm_gem_begin_shadow_fb_access - prepares shadow framebuffers for CPU access
344  * @plane: the plane
345  * @plane_state: the plane state of type struct drm_shadow_plane_state
346  *
347  * This function implements struct &drm_plane_helper_funcs.begin_fb_access. It
348  * maps all buffer objects of the plane's framebuffer into kernel address
349  * space and stores them in struct &drm_shadow_plane_state.map. The first data
350  * bytes are available in struct &drm_shadow_plane_state.data.
351  *
352  * See drm_gem_end_shadow_fb_access() for cleanup.
353  *
354  * Returns:
355  * 0 on success, or a negative errno code otherwise.
356  */
drm_gem_begin_shadow_fb_access(struct drm_plane * plane,struct drm_plane_state * plane_state)357 int drm_gem_begin_shadow_fb_access(struct drm_plane *plane, struct drm_plane_state *plane_state)
358 {
359 	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(plane_state);
360 	struct drm_framebuffer *fb = plane_state->fb;
361 
362 	if (!fb)
363 		return 0;
364 
365 	return drm_gem_fb_vmap(fb, shadow_plane_state->map, shadow_plane_state->data);
366 }
367 EXPORT_SYMBOL(drm_gem_begin_shadow_fb_access);
368 
369 /**
370  * drm_gem_end_shadow_fb_access - releases shadow framebuffers from CPU access
371  * @plane: the plane
372  * @plane_state: the plane state of type struct drm_shadow_plane_state
373  *
374  * This function implements struct &drm_plane_helper_funcs.end_fb_access. It
375  * undoes all effects of drm_gem_begin_shadow_fb_access() in reverse order.
376  *
377  * See drm_gem_begin_shadow_fb_access() for more information.
378  */
drm_gem_end_shadow_fb_access(struct drm_plane * plane,struct drm_plane_state * plane_state)379 void drm_gem_end_shadow_fb_access(struct drm_plane *plane, struct drm_plane_state *plane_state)
380 {
381 	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(plane_state);
382 	struct drm_framebuffer *fb = plane_state->fb;
383 
384 	if (!fb)
385 		return;
386 
387 	drm_gem_fb_vunmap(fb, shadow_plane_state->map);
388 }
389 EXPORT_SYMBOL(drm_gem_end_shadow_fb_access);
390 
391 /**
392  * drm_gem_simple_kms_begin_shadow_fb_access - prepares shadow framebuffers for CPU access
393  * @pipe: the simple display pipe
394  * @plane_state: the plane state of type struct drm_shadow_plane_state
395  *
396  * This function implements struct drm_simple_display_funcs.begin_fb_access.
397  *
398  * See drm_gem_begin_shadow_fb_access() for details and
399  * drm_gem_simple_kms_cleanup_shadow_fb() for cleanup.
400  *
401  * Returns:
402  * 0 on success, or a negative errno code otherwise.
403  */
drm_gem_simple_kms_begin_shadow_fb_access(struct drm_simple_display_pipe * pipe,struct drm_plane_state * plane_state)404 int drm_gem_simple_kms_begin_shadow_fb_access(struct drm_simple_display_pipe *pipe,
405 					      struct drm_plane_state *plane_state)
406 {
407 	return drm_gem_begin_shadow_fb_access(&pipe->plane, plane_state);
408 }
409 EXPORT_SYMBOL(drm_gem_simple_kms_begin_shadow_fb_access);
410 
411 /**
412  * drm_gem_simple_kms_end_shadow_fb_access - releases shadow framebuffers from CPU access
413  * @pipe: the simple display pipe
414  * @plane_state: the plane state of type struct drm_shadow_plane_state
415  *
416  * This function implements struct drm_simple_display_funcs.end_fb_access.
417  * It undoes all effects of drm_gem_simple_kms_begin_shadow_fb_access() in
418  * reverse order.
419  *
420  * See drm_gem_simple_kms_begin_shadow_fb_access().
421  */
drm_gem_simple_kms_end_shadow_fb_access(struct drm_simple_display_pipe * pipe,struct drm_plane_state * plane_state)422 void drm_gem_simple_kms_end_shadow_fb_access(struct drm_simple_display_pipe *pipe,
423 					     struct drm_plane_state *plane_state)
424 {
425 	drm_gem_end_shadow_fb_access(&pipe->plane, plane_state);
426 }
427 EXPORT_SYMBOL(drm_gem_simple_kms_end_shadow_fb_access);
428 
429 /**
430  * drm_gem_simple_kms_reset_shadow_plane - resets a shadow-buffered plane
431  * @pipe: the simple display pipe
432  *
433  * This function implements struct drm_simple_display_funcs.reset_plane
434  * for shadow-buffered planes.
435  */
drm_gem_simple_kms_reset_shadow_plane(struct drm_simple_display_pipe * pipe)436 void drm_gem_simple_kms_reset_shadow_plane(struct drm_simple_display_pipe *pipe)
437 {
438 	drm_gem_reset_shadow_plane(&pipe->plane);
439 }
440 EXPORT_SYMBOL(drm_gem_simple_kms_reset_shadow_plane);
441 
442 /**
443  * drm_gem_simple_kms_duplicate_shadow_plane_state - duplicates shadow-buffered plane state
444  * @pipe: the simple display pipe
445  *
446  * This function implements struct drm_simple_display_funcs.duplicate_plane_state
447  * for shadow-buffered planes. It does not duplicate existing mappings of the shadow
448  * buffers. Mappings are maintained during the atomic commit by the plane's prepare_fb
449  * and cleanup_fb helpers.
450  *
451  * Returns:
452  * A pointer to a new plane state on success, or NULL otherwise.
453  */
454 struct drm_plane_state *
drm_gem_simple_kms_duplicate_shadow_plane_state(struct drm_simple_display_pipe * pipe)455 drm_gem_simple_kms_duplicate_shadow_plane_state(struct drm_simple_display_pipe *pipe)
456 {
457 	return drm_gem_duplicate_shadow_plane_state(&pipe->plane);
458 }
459 EXPORT_SYMBOL(drm_gem_simple_kms_duplicate_shadow_plane_state);
460 
461 /**
462  * drm_gem_simple_kms_destroy_shadow_plane_state - resets shadow-buffered plane state
463  * @pipe: the simple display pipe
464  * @plane_state: the plane state of type struct drm_shadow_plane_state
465  *
466  * This function implements struct drm_simple_display_funcs.destroy_plane_state
467  * for shadow-buffered planes. It expects that mappings of shadow buffers
468  * have been released already.
469  */
drm_gem_simple_kms_destroy_shadow_plane_state(struct drm_simple_display_pipe * pipe,struct drm_plane_state * plane_state)470 void drm_gem_simple_kms_destroy_shadow_plane_state(struct drm_simple_display_pipe *pipe,
471 						   struct drm_plane_state *plane_state)
472 {
473 	drm_gem_destroy_shadow_plane_state(&pipe->plane, plane_state);
474 }
475 EXPORT_SYMBOL(drm_gem_simple_kms_destroy_shadow_plane_state);
476