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 */
135int 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
194error:
195	dma_fence_put(fence);
196	return ret;
197}
198EXPORT_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 */
217void
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(&shadow_plane_state->fmtcnv_state,
228				   &new_shadow_plane_state->fmtcnv_state);
229}
230EXPORT_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 */
249struct drm_plane_state *
250drm_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}
265EXPORT_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 */
274void __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}
279EXPORT_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 */
290void 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}
299EXPORT_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 */
309void __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}
315EXPORT_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 */
326void 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}
340EXPORT_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 */
357int 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}
367EXPORT_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 */
379void 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}
389EXPORT_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 */
404int 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}
409EXPORT_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 */
422void 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}
427EXPORT_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 */
436void drm_gem_simple_kms_reset_shadow_plane(struct drm_simple_display_pipe *pipe)
437{
438	drm_gem_reset_shadow_plane(&pipe->plane);
439}
440EXPORT_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 */
454struct drm_plane_state *
455drm_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}
459EXPORT_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 */
470void 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}
475EXPORT_SYMBOL(drm_gem_simple_kms_destroy_shadow_plane_state);