Line data Source code
1 : /*
2 : * Header file for reservations for dma-buf and ttm
3 : *
4 : * Copyright(C) 2011 Linaro Limited. All rights reserved.
5 : * Copyright (C) 2012-2013 Canonical Ltd
6 : * Copyright (C) 2012 Texas Instruments
7 : *
8 : * Authors:
9 : * Rob Clark <robdclark@gmail.com>
10 : * Maarten Lankhorst <maarten.lankhorst@canonical.com>
11 : * Thomas Hellstrom <thellstrom-at-vmware-dot-com>
12 : *
13 : * Based on bo.c which bears the following copyright notice,
14 : * but is dual licensed:
15 : *
16 : * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
17 : * All Rights Reserved.
18 : *
19 : * Permission is hereby granted, free of charge, to any person obtaining a
20 : * copy of this software and associated documentation files (the
21 : * "Software"), to deal in the Software without restriction, including
22 : * without limitation the rights to use, copy, modify, merge, publish,
23 : * distribute, sub license, and/or sell copies of the Software, and to
24 : * permit persons to whom the Software is furnished to do so, subject to
25 : * the following conditions:
26 : *
27 : * The above copyright notice and this permission notice (including the
28 : * next paragraph) shall be included in all copies or substantial portions
29 : * of the Software.
30 : *
31 : * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
32 : * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
33 : * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
34 : * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
35 : * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
36 : * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
37 : * USE OR OTHER DEALINGS IN THE SOFTWARE.
38 : */
39 : #ifndef _LINUX_RESERVATION_H
40 : #define _LINUX_RESERVATION_H
41 :
42 : #include <linux/ww_mutex.h>
43 : #include <linux/dma-fence.h>
44 : #include <linux/slab.h>
45 : #include <linux/seqlock.h>
46 : #include <linux/rcupdate.h>
47 :
48 : extern struct ww_class reservation_ww_class;
49 :
50 : struct dma_resv_list;
51 :
52 : /**
53 : * enum dma_resv_usage - how the fences from a dma_resv obj are used
54 : *
55 : * This enum describes the different use cases for a dma_resv object and
56 : * controls which fences are returned when queried.
57 : *
58 : * An important fact is that there is the order KERNEL<WRITE<READ<BOOKKEEP and
59 : * when the dma_resv object is asked for fences for one use case the fences
60 : * for the lower use case are returned as well.
61 : *
62 : * For example when asking for WRITE fences then the KERNEL fences are returned
63 : * as well. Similar when asked for READ fences then both WRITE and KERNEL
64 : * fences are returned as well.
65 : *
66 : * Already used fences can be promoted in the sense that a fence with
67 : * DMA_RESV_USAGE_BOOKKEEP could become DMA_RESV_USAGE_READ by adding it again
68 : * with this usage. But fences can never be degraded in the sense that a fence
69 : * with DMA_RESV_USAGE_WRITE could become DMA_RESV_USAGE_READ.
70 : */
71 : enum dma_resv_usage {
72 : /**
73 : * @DMA_RESV_USAGE_KERNEL: For in kernel memory management only.
74 : *
75 : * This should only be used for things like copying or clearing memory
76 : * with a DMA hardware engine for the purpose of kernel memory
77 : * management.
78 : *
79 : * Drivers *always* must wait for those fences before accessing the
80 : * resource protected by the dma_resv object. The only exception for
81 : * that is when the resource is known to be locked down in place by
82 : * pinning it previously.
83 : */
84 : DMA_RESV_USAGE_KERNEL,
85 :
86 : /**
87 : * @DMA_RESV_USAGE_WRITE: Implicit write synchronization.
88 : *
89 : * This should only be used for userspace command submissions which add
90 : * an implicit write dependency.
91 : */
92 : DMA_RESV_USAGE_WRITE,
93 :
94 : /**
95 : * @DMA_RESV_USAGE_READ: Implicit read synchronization.
96 : *
97 : * This should only be used for userspace command submissions which add
98 : * an implicit read dependency.
99 : */
100 : DMA_RESV_USAGE_READ,
101 :
102 : /**
103 : * @DMA_RESV_USAGE_BOOKKEEP: No implicit sync.
104 : *
105 : * This should be used by submissions which don't want to participate in
106 : * any implicit synchronization.
107 : *
108 : * The most common case are preemption fences, page table updates, TLB
109 : * flushes as well as explicit synced user submissions.
110 : *
111 : * Explicit synced user user submissions can be promoted to
112 : * DMA_RESV_USAGE_READ or DMA_RESV_USAGE_WRITE as needed using
113 : * dma_buf_import_sync_file() when implicit synchronization should
114 : * become necessary after initial adding of the fence.
115 : */
116 : DMA_RESV_USAGE_BOOKKEEP
117 : };
118 :
119 : /**
120 : * dma_resv_usage_rw - helper for implicit sync
121 : * @write: true if we create a new implicit sync write
122 : *
123 : * This returns the implicit synchronization usage for write or read accesses,
124 : * see enum dma_resv_usage and &dma_buf.resv.
125 : */
126 : static inline enum dma_resv_usage dma_resv_usage_rw(bool write)
127 : {
128 : /* This looks confusing at first sight, but is indeed correct.
129 : *
130 : * The rational is that new write operations needs to wait for the
131 : * existing read and write operations to finish.
132 : * But a new read operation only needs to wait for the existing write
133 : * operations to finish.
134 : */
135 0 : return write ? DMA_RESV_USAGE_READ : DMA_RESV_USAGE_WRITE;
136 : }
137 :
138 : /**
139 : * struct dma_resv - a reservation object manages fences for a buffer
140 : *
141 : * This is a container for dma_fence objects which needs to handle multiple use
142 : * cases.
143 : *
144 : * One use is to synchronize cross-driver access to a struct dma_buf, either for
145 : * dynamic buffer management or just to handle implicit synchronization between
146 : * different users of the buffer in userspace. See &dma_buf.resv for a more
147 : * in-depth discussion.
148 : *
149 : * The other major use is to manage access and locking within a driver in a
150 : * buffer based memory manager. struct ttm_buffer_object is the canonical
151 : * example here, since this is where reservation objects originated from. But
152 : * use in drivers is spreading and some drivers also manage struct
153 : * drm_gem_object with the same scheme.
154 : */
155 : struct dma_resv {
156 : /**
157 : * @lock:
158 : *
159 : * Update side lock. Don't use directly, instead use the wrapper
160 : * functions like dma_resv_lock() and dma_resv_unlock().
161 : *
162 : * Drivers which use the reservation object to manage memory dynamically
163 : * also use this lock to protect buffer object state like placement,
164 : * allocation policies or throughout command submission.
165 : */
166 : struct ww_mutex lock;
167 :
168 : /**
169 : * @fences:
170 : *
171 : * Array of fences which where added to the dma_resv object
172 : *
173 : * A new fence is added by calling dma_resv_add_fence(). Since this
174 : * often needs to be done past the point of no return in command
175 : * submission it cannot fail, and therefore sufficient slots need to be
176 : * reserved by calling dma_resv_reserve_fences().
177 : */
178 : struct dma_resv_list __rcu *fences;
179 : };
180 :
181 : /**
182 : * struct dma_resv_iter - current position into the dma_resv fences
183 : *
184 : * Don't touch this directly in the driver, use the accessor function instead.
185 : *
186 : * IMPORTANT
187 : *
188 : * When using the lockless iterators like dma_resv_iter_next_unlocked() or
189 : * dma_resv_for_each_fence_unlocked() beware that the iterator can be restarted.
190 : * Code which accumulates statistics or similar needs to check for this with
191 : * dma_resv_iter_is_restarted().
192 : */
193 : struct dma_resv_iter {
194 : /** @obj: The dma_resv object we iterate over */
195 : struct dma_resv *obj;
196 :
197 : /** @usage: Return fences with this usage or lower. */
198 : enum dma_resv_usage usage;
199 :
200 : /** @fence: the currently handled fence */
201 : struct dma_fence *fence;
202 :
203 : /** @fence_usage: the usage of the current fence */
204 : enum dma_resv_usage fence_usage;
205 :
206 : /** @index: index into the shared fences */
207 : unsigned int index;
208 :
209 : /** @fences: the shared fences; private, *MUST* not dereference */
210 : struct dma_resv_list *fences;
211 :
212 : /** @num_fences: number of fences */
213 : unsigned int num_fences;
214 :
215 : /** @is_restarted: true if this is the first returned fence */
216 : bool is_restarted;
217 : };
218 :
219 : struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor);
220 : struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor);
221 : struct dma_fence *dma_resv_iter_first(struct dma_resv_iter *cursor);
222 : struct dma_fence *dma_resv_iter_next(struct dma_resv_iter *cursor);
223 :
224 : /**
225 : * dma_resv_iter_begin - initialize a dma_resv_iter object
226 : * @cursor: The dma_resv_iter object to initialize
227 : * @obj: The dma_resv object which we want to iterate over
228 : * @usage: controls which fences to include, see enum dma_resv_usage.
229 : */
230 : static inline void dma_resv_iter_begin(struct dma_resv_iter *cursor,
231 : struct dma_resv *obj,
232 : enum dma_resv_usage usage)
233 : {
234 0 : cursor->obj = obj;
235 0 : cursor->usage = usage;
236 0 : cursor->fence = NULL;
237 : }
238 :
239 : /**
240 : * dma_resv_iter_end - cleanup a dma_resv_iter object
241 : * @cursor: the dma_resv_iter object which should be cleaned up
242 : *
243 : * Make sure that the reference to the fence in the cursor is properly
244 : * dropped.
245 : */
246 : static inline void dma_resv_iter_end(struct dma_resv_iter *cursor)
247 : {
248 0 : dma_fence_put(cursor->fence);
249 : }
250 :
251 : /**
252 : * dma_resv_iter_usage - Return the usage of the current fence
253 : * @cursor: the cursor of the current position
254 : *
255 : * Returns the usage of the currently processed fence.
256 : */
257 : static inline enum dma_resv_usage
258 : dma_resv_iter_usage(struct dma_resv_iter *cursor)
259 : {
260 : return cursor->fence_usage;
261 : }
262 :
263 : /**
264 : * dma_resv_iter_is_restarted - test if this is the first fence after a restart
265 : * @cursor: the cursor with the current position
266 : *
267 : * Return true if this is the first fence in an iteration after a restart.
268 : */
269 : static inline bool dma_resv_iter_is_restarted(struct dma_resv_iter *cursor)
270 : {
271 : return cursor->is_restarted;
272 : }
273 :
274 : /**
275 : * dma_resv_for_each_fence_unlocked - unlocked fence iterator
276 : * @cursor: a struct dma_resv_iter pointer
277 : * @fence: the current fence
278 : *
279 : * Iterate over the fences in a struct dma_resv object without holding the
280 : * &dma_resv.lock and using RCU instead. The cursor needs to be initialized
281 : * with dma_resv_iter_begin() and cleaned up with dma_resv_iter_end(). Inside
282 : * the iterator a reference to the dma_fence is held and the RCU lock dropped.
283 : *
284 : * Beware that the iterator can be restarted when the struct dma_resv for
285 : * @cursor is modified. Code which accumulates statistics or similar needs to
286 : * check for this with dma_resv_iter_is_restarted(). For this reason prefer the
287 : * lock iterator dma_resv_for_each_fence() whenever possible.
288 : */
289 : #define dma_resv_for_each_fence_unlocked(cursor, fence) \
290 : for (fence = dma_resv_iter_first_unlocked(cursor); \
291 : fence; fence = dma_resv_iter_next_unlocked(cursor))
292 :
293 : /**
294 : * dma_resv_for_each_fence - fence iterator
295 : * @cursor: a struct dma_resv_iter pointer
296 : * @obj: a dma_resv object pointer
297 : * @usage: controls which fences to return
298 : * @fence: the current fence
299 : *
300 : * Iterate over the fences in a struct dma_resv object while holding the
301 : * &dma_resv.lock. @all_fences controls if the shared fences are returned as
302 : * well. The cursor initialisation is part of the iterator and the fence stays
303 : * valid as long as the lock is held and so no extra reference to the fence is
304 : * taken.
305 : */
306 : #define dma_resv_for_each_fence(cursor, obj, usage, fence) \
307 : for (dma_resv_iter_begin(cursor, obj, usage), \
308 : fence = dma_resv_iter_first(cursor); fence; \
309 : fence = dma_resv_iter_next(cursor))
310 :
311 : #define dma_resv_held(obj) lockdep_is_held(&(obj)->lock.base)
312 : #define dma_resv_assert_held(obj) lockdep_assert_held(&(obj)->lock.base)
313 :
314 : #ifdef CONFIG_DEBUG_MUTEXES
315 : void dma_resv_reset_max_fences(struct dma_resv *obj);
316 : #else
317 : static inline void dma_resv_reset_max_fences(struct dma_resv *obj) {}
318 : #endif
319 :
320 : /**
321 : * dma_resv_lock - lock the reservation object
322 : * @obj: the reservation object
323 : * @ctx: the locking context
324 : *
325 : * Locks the reservation object for exclusive access and modification. Note,
326 : * that the lock is only against other writers, readers will run concurrently
327 : * with a writer under RCU. The seqlock is used to notify readers if they
328 : * overlap with a writer.
329 : *
330 : * As the reservation object may be locked by multiple parties in an
331 : * undefined order, a #ww_acquire_ctx is passed to unwind if a cycle
332 : * is detected. See ww_mutex_lock() and ww_acquire_init(). A reservation
333 : * object may be locked by itself by passing NULL as @ctx.
334 : *
335 : * When a die situation is indicated by returning -EDEADLK all locks held by
336 : * @ctx must be unlocked and then dma_resv_lock_slow() called on @obj.
337 : *
338 : * Unlocked by calling dma_resv_unlock().
339 : *
340 : * See also dma_resv_lock_interruptible() for the interruptible variant.
341 : */
342 : static inline int dma_resv_lock(struct dma_resv *obj,
343 : struct ww_acquire_ctx *ctx)
344 : {
345 0 : return ww_mutex_lock(&obj->lock, ctx);
346 : }
347 :
348 : /**
349 : * dma_resv_lock_interruptible - lock the reservation object
350 : * @obj: the reservation object
351 : * @ctx: the locking context
352 : *
353 : * Locks the reservation object interruptible for exclusive access and
354 : * modification. Note, that the lock is only against other writers, readers
355 : * will run concurrently with a writer under RCU. The seqlock is used to
356 : * notify readers if they overlap with a writer.
357 : *
358 : * As the reservation object may be locked by multiple parties in an
359 : * undefined order, a #ww_acquire_ctx is passed to unwind if a cycle
360 : * is detected. See ww_mutex_lock() and ww_acquire_init(). A reservation
361 : * object may be locked by itself by passing NULL as @ctx.
362 : *
363 : * When a die situation is indicated by returning -EDEADLK all locks held by
364 : * @ctx must be unlocked and then dma_resv_lock_slow_interruptible() called on
365 : * @obj.
366 : *
367 : * Unlocked by calling dma_resv_unlock().
368 : */
369 : static inline int dma_resv_lock_interruptible(struct dma_resv *obj,
370 : struct ww_acquire_ctx *ctx)
371 : {
372 0 : return ww_mutex_lock_interruptible(&obj->lock, ctx);
373 : }
374 :
375 : /**
376 : * dma_resv_lock_slow - slowpath lock the reservation object
377 : * @obj: the reservation object
378 : * @ctx: the locking context
379 : *
380 : * Acquires the reservation object after a die case. This function
381 : * will sleep until the lock becomes available. See dma_resv_lock() as
382 : * well.
383 : *
384 : * See also dma_resv_lock_slow_interruptible() for the interruptible variant.
385 : */
386 : static inline void dma_resv_lock_slow(struct dma_resv *obj,
387 : struct ww_acquire_ctx *ctx)
388 : {
389 : ww_mutex_lock_slow(&obj->lock, ctx);
390 : }
391 :
392 : /**
393 : * dma_resv_lock_slow_interruptible - slowpath lock the reservation
394 : * object, interruptible
395 : * @obj: the reservation object
396 : * @ctx: the locking context
397 : *
398 : * Acquires the reservation object interruptible after a die case. This function
399 : * will sleep until the lock becomes available. See
400 : * dma_resv_lock_interruptible() as well.
401 : */
402 : static inline int dma_resv_lock_slow_interruptible(struct dma_resv *obj,
403 : struct ww_acquire_ctx *ctx)
404 : {
405 0 : return ww_mutex_lock_slow_interruptible(&obj->lock, ctx);
406 : }
407 :
408 : /**
409 : * dma_resv_trylock - trylock the reservation object
410 : * @obj: the reservation object
411 : *
412 : * Tries to lock the reservation object for exclusive access and modification.
413 : * Note, that the lock is only against other writers, readers will run
414 : * concurrently with a writer under RCU. The seqlock is used to notify readers
415 : * if they overlap with a writer.
416 : *
417 : * Also note that since no context is provided, no deadlock protection is
418 : * possible, which is also not needed for a trylock.
419 : *
420 : * Returns true if the lock was acquired, false otherwise.
421 : */
422 : static inline bool __must_check dma_resv_trylock(struct dma_resv *obj)
423 : {
424 0 : return ww_mutex_trylock(&obj->lock, NULL);
425 : }
426 :
427 : /**
428 : * dma_resv_is_locked - is the reservation object locked
429 : * @obj: the reservation object
430 : *
431 : * Returns true if the mutex is locked, false if unlocked.
432 : */
433 : static inline bool dma_resv_is_locked(struct dma_resv *obj)
434 : {
435 : return ww_mutex_is_locked(&obj->lock);
436 : }
437 :
438 : /**
439 : * dma_resv_locking_ctx - returns the context used to lock the object
440 : * @obj: the reservation object
441 : *
442 : * Returns the context used to lock a reservation object or NULL if no context
443 : * was used or the object is not locked at all.
444 : *
445 : * WARNING: This interface is pretty horrible, but TTM needs it because it
446 : * doesn't pass the struct ww_acquire_ctx around in some very long callchains.
447 : * Everyone else just uses it to check whether they're holding a reservation or
448 : * not.
449 : */
450 : static inline struct ww_acquire_ctx *dma_resv_locking_ctx(struct dma_resv *obj)
451 : {
452 : return READ_ONCE(obj->lock.ctx);
453 : }
454 :
455 : /**
456 : * dma_resv_unlock - unlock the reservation object
457 : * @obj: the reservation object
458 : *
459 : * Unlocks the reservation object following exclusive access.
460 : */
461 : static inline void dma_resv_unlock(struct dma_resv *obj)
462 : {
463 0 : dma_resv_reset_max_fences(obj);
464 0 : ww_mutex_unlock(&obj->lock);
465 : }
466 :
467 : void dma_resv_init(struct dma_resv *obj);
468 : void dma_resv_fini(struct dma_resv *obj);
469 : int dma_resv_reserve_fences(struct dma_resv *obj, unsigned int num_fences);
470 : void dma_resv_add_fence(struct dma_resv *obj, struct dma_fence *fence,
471 : enum dma_resv_usage usage);
472 : void dma_resv_replace_fences(struct dma_resv *obj, uint64_t context,
473 : struct dma_fence *fence,
474 : enum dma_resv_usage usage);
475 : int dma_resv_get_fences(struct dma_resv *obj, enum dma_resv_usage usage,
476 : unsigned int *num_fences, struct dma_fence ***fences);
477 : int dma_resv_get_singleton(struct dma_resv *obj, enum dma_resv_usage usage,
478 : struct dma_fence **fence);
479 : int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src);
480 : long dma_resv_wait_timeout(struct dma_resv *obj, enum dma_resv_usage usage,
481 : bool intr, unsigned long timeout);
482 : bool dma_resv_test_signaled(struct dma_resv *obj, enum dma_resv_usage usage);
483 : void dma_resv_describe(struct dma_resv *obj, struct seq_file *seq);
484 :
485 : #endif /* _LINUX_RESERVATION_H */
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