drm_gem_atomic_helper.c

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