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