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  */
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
218 __drm_gem_duplicate_shadow_plane_state(struct drm_plane *plane,
219 				       struct drm_shadow_plane_state *new_shadow_plane_state)
220 {
221 	__drm_atomic_helper_plane_duplicate_state(plane, &new_shadow_plane_state->base);
222 }
223 EXPORT_SYMBOL(__drm_gem_duplicate_shadow_plane_state);
224 
225 /**
226  * drm_gem_duplicate_shadow_plane_state - duplicates shadow-buffered plane state
227  * @plane: the plane
228  *
229  * This function implements struct &drm_plane_funcs.atomic_duplicate_state for
230  * shadow-buffered planes. It assumes the existing state to be of type
231  * struct drm_shadow_plane_state and it allocates the new state to be of this
232  * type.
233  *
234  * The function does not duplicate existing mappings of the shadow buffers.
235  * Mappings are maintained during the atomic commit by the plane's prepare_fb
236  * and cleanup_fb helpers. See drm_gem_prepare_shadow_fb() and drm_gem_cleanup_shadow_fb()
237  * for corresponding helpers.
238  *
239  * Returns:
240  * A pointer to a new plane state on success, or NULL otherwise.
241  */
242 struct drm_plane_state *
243 drm_gem_duplicate_shadow_plane_state(struct drm_plane *plane)
244 {
245 	struct drm_plane_state *plane_state = plane->state;
246 	struct drm_shadow_plane_state *new_shadow_plane_state;
247 
248 	if (!plane_state)
249 		return NULL;
250 
251 	new_shadow_plane_state = kzalloc(sizeof(*new_shadow_plane_state), GFP_KERNEL);
252 	if (!new_shadow_plane_state)
253 		return NULL;
254 	__drm_gem_duplicate_shadow_plane_state(plane, new_shadow_plane_state);
255 
256 	return &new_shadow_plane_state->base;
257 }
258 EXPORT_SYMBOL(drm_gem_duplicate_shadow_plane_state);
259 
260 /**
261  * __drm_gem_destroy_shadow_plane_state - cleans up shadow-buffered plane state
262  * @shadow_plane_state: the shadow-buffered plane state
263  *
264  * This function cleans up shadow-buffered plane state. Helpful for drivers that
265  * subclass struct drm_shadow_plane_state.
266  */
267 void __drm_gem_destroy_shadow_plane_state(struct drm_shadow_plane_state *shadow_plane_state)
268 {
269 	__drm_atomic_helper_plane_destroy_state(&shadow_plane_state->base);
270 }
271 EXPORT_SYMBOL(__drm_gem_destroy_shadow_plane_state);
272 
273 /**
274  * drm_gem_destroy_shadow_plane_state - deletes shadow-buffered plane state
275  * @plane: the plane
276  * @plane_state: the plane state of type struct drm_shadow_plane_state
277  *
278  * This function implements struct &drm_plane_funcs.atomic_destroy_state
279  * for shadow-buffered planes. It expects that mappings of shadow buffers
280  * have been released already.
281  */
282 void drm_gem_destroy_shadow_plane_state(struct drm_plane *plane,
283 					struct drm_plane_state *plane_state)
284 {
285 	struct drm_shadow_plane_state *shadow_plane_state =
286 		to_drm_shadow_plane_state(plane_state);
287 
288 	__drm_gem_destroy_shadow_plane_state(shadow_plane_state);
289 	kfree(shadow_plane_state);
290 }
291 EXPORT_SYMBOL(drm_gem_destroy_shadow_plane_state);
292 
293 /**
294  * __drm_gem_reset_shadow_plane - resets a shadow-buffered plane
295  * @plane: the plane
296  * @shadow_plane_state: the shadow-buffered plane state
297  *
298  * This function resets state for shadow-buffered planes. Helpful
299  * for drivers that subclass struct drm_shadow_plane_state.
300  */
301 void __drm_gem_reset_shadow_plane(struct drm_plane *plane,
302 				  struct drm_shadow_plane_state *shadow_plane_state)
303 {
304 	__drm_atomic_helper_plane_reset(plane, &shadow_plane_state->base);
305 }
306 EXPORT_SYMBOL(__drm_gem_reset_shadow_plane);
307 
308 /**
309  * drm_gem_reset_shadow_plane - resets a shadow-buffered plane
310  * @plane: the plane
311  *
312  * This function implements struct &drm_plane_funcs.reset_plane for
313  * shadow-buffered planes. It assumes the current plane state to be
314  * of type struct drm_shadow_plane and it allocates the new state of
315  * this type.
316  */
317 void drm_gem_reset_shadow_plane(struct drm_plane *plane)
318 {
319 	struct drm_shadow_plane_state *shadow_plane_state;
320 
321 	if (plane->state) {
322 		drm_gem_destroy_shadow_plane_state(plane, plane->state);
323 		plane->state = NULL; /* must be set to NULL here */
324 	}
325 
326 	shadow_plane_state = kzalloc(sizeof(*shadow_plane_state), GFP_KERNEL);
327 	if (!shadow_plane_state)
328 		return;
329 	__drm_gem_reset_shadow_plane(plane, shadow_plane_state);
330 }
331 EXPORT_SYMBOL(drm_gem_reset_shadow_plane);
332 
333 /**
334  * drm_gem_begin_shadow_fb_access - prepares shadow framebuffers for CPU access
335  * @plane: the plane
336  * @plane_state: the plane state of type struct drm_shadow_plane_state
337  *
338  * This function implements struct &drm_plane_helper_funcs.begin_fb_access. It
339  * maps all buffer objects of the plane's framebuffer into kernel address
340  * space and stores them in struct &drm_shadow_plane_state.map. The first data
341  * bytes are available in struct &drm_shadow_plane_state.data.
342  *
343  * See drm_gem_end_shadow_fb_access() for cleanup.
344  *
345  * Returns:
346  * 0 on success, or a negative errno code otherwise.
347  */
348 int drm_gem_begin_shadow_fb_access(struct drm_plane *plane, struct drm_plane_state *plane_state)
349 {
350 	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(plane_state);
351 	struct drm_framebuffer *fb = plane_state->fb;
352 
353 	if (!fb)
354 		return 0;
355 
356 	return drm_gem_fb_vmap(fb, shadow_plane_state->map, shadow_plane_state->data);
357 }
358 EXPORT_SYMBOL(drm_gem_begin_shadow_fb_access);
359 
360 /**
361  * drm_gem_end_shadow_fb_access - releases shadow framebuffers from CPU access
362  * @plane: the plane
363  * @plane_state: the plane state of type struct drm_shadow_plane_state
364  *
365  * This function implements struct &drm_plane_helper_funcs.end_fb_access. It
366  * undoes all effects of drm_gem_begin_shadow_fb_access() in reverse order.
367  *
368  * See drm_gem_begin_shadow_fb_access() for more information.
369  */
370 void drm_gem_end_shadow_fb_access(struct drm_plane *plane, struct drm_plane_state *plane_state)
371 {
372 	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(plane_state);
373 	struct drm_framebuffer *fb = plane_state->fb;
374 
375 	if (!fb)
376 		return;
377 
378 	drm_gem_fb_vunmap(fb, shadow_plane_state->map);
379 }
380 EXPORT_SYMBOL(drm_gem_end_shadow_fb_access);
381 
382 /**
383  * drm_gem_simple_kms_begin_shadow_fb_access - prepares shadow framebuffers for CPU access
384  * @pipe: the simple display pipe
385  * @plane_state: the plane state of type struct drm_shadow_plane_state
386  *
387  * This function implements struct drm_simple_display_funcs.begin_fb_access.
388  *
389  * See drm_gem_begin_shadow_fb_access() for details and
390  * drm_gem_simple_kms_cleanup_shadow_fb() for cleanup.
391  *
392  * Returns:
393  * 0 on success, or a negative errno code otherwise.
394  */
395 int drm_gem_simple_kms_begin_shadow_fb_access(struct drm_simple_display_pipe *pipe,
396 					      struct drm_plane_state *plane_state)
397 {
398 	return drm_gem_begin_shadow_fb_access(&pipe->plane, plane_state);
399 }
400 EXPORT_SYMBOL(drm_gem_simple_kms_begin_shadow_fb_access);
401 
402 /**
403  * drm_gem_simple_kms_end_shadow_fb_access - releases shadow framebuffers from CPU access
404  * @pipe: the simple display pipe
405  * @plane_state: the plane state of type struct drm_shadow_plane_state
406  *
407  * This function implements struct drm_simple_display_funcs.end_fb_access.
408  * It undoes all effects of drm_gem_simple_kms_begin_shadow_fb_access() in
409  * reverse order.
410  *
411  * See drm_gem_simple_kms_begin_shadow_fb_access().
412  */
413 void drm_gem_simple_kms_end_shadow_fb_access(struct drm_simple_display_pipe *pipe,
414 					     struct drm_plane_state *plane_state)
415 {
416 	drm_gem_end_shadow_fb_access(&pipe->plane, plane_state);
417 }
418 EXPORT_SYMBOL(drm_gem_simple_kms_end_shadow_fb_access);
419 
420 /**
421  * drm_gem_simple_kms_reset_shadow_plane - resets a shadow-buffered plane
422  * @pipe: the simple display pipe
423  *
424  * This function implements struct drm_simple_display_funcs.reset_plane
425  * for shadow-buffered planes.
426  */
427 void drm_gem_simple_kms_reset_shadow_plane(struct drm_simple_display_pipe *pipe)
428 {
429 	drm_gem_reset_shadow_plane(&pipe->plane);
430 }
431 EXPORT_SYMBOL(drm_gem_simple_kms_reset_shadow_plane);
432 
433 /**
434  * drm_gem_simple_kms_duplicate_shadow_plane_state - duplicates shadow-buffered plane state
435  * @pipe: the simple display pipe
436  *
437  * This function implements struct drm_simple_display_funcs.duplicate_plane_state
438  * for shadow-buffered planes. It does not duplicate existing mappings of the shadow
439  * buffers. Mappings are maintained during the atomic commit by the plane's prepare_fb
440  * and cleanup_fb helpers.
441  *
442  * Returns:
443  * A pointer to a new plane state on success, or NULL otherwise.
444  */
445 struct drm_plane_state *
446 drm_gem_simple_kms_duplicate_shadow_plane_state(struct drm_simple_display_pipe *pipe)
447 {
448 	return drm_gem_duplicate_shadow_plane_state(&pipe->plane);
449 }
450 EXPORT_SYMBOL(drm_gem_simple_kms_duplicate_shadow_plane_state);
451 
452 /**
453  * drm_gem_simple_kms_destroy_shadow_plane_state - resets shadow-buffered plane state
454  * @pipe: the simple display pipe
455  * @plane_state: the plane state of type struct drm_shadow_plane_state
456  *
457  * This function implements struct drm_simple_display_funcs.destroy_plane_state
458  * for shadow-buffered planes. It expects that mappings of shadow buffers
459  * have been released already.
460  */
461 void drm_gem_simple_kms_destroy_shadow_plane_state(struct drm_simple_display_pipe *pipe,
462 						   struct drm_plane_state *plane_state)
463 {
464 	drm_gem_destroy_shadow_plane_state(&pipe->plane, plane_state);
465 }
466 EXPORT_SYMBOL(drm_gem_simple_kms_destroy_shadow_plane_state);
467