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 : enum dma_resv_usage {
67 : /**
68 : * @DMA_RESV_USAGE_KERNEL: For in kernel memory management only.
69 : *
70 : * This should only be used for things like copying or clearing memory
71 : * with a DMA hardware engine for the purpose of kernel memory
72 : * management.
73 : *
74 : * Drivers *always* must wait for those fences before accessing the
75 : * resource protected by the dma_resv object. The only exception for
76 : * that is when the resource is known to be locked down in place by
77 : * pinning it previously.
78 : */
79 : DMA_RESV_USAGE_KERNEL,
80 :
81 : /**
82 : * @DMA_RESV_USAGE_WRITE: Implicit write synchronization.
83 : *
84 : * This should only be used for userspace command submissions which add
85 : * an implicit write dependency.
86 : */
87 : DMA_RESV_USAGE_WRITE,
88 :
89 : /**
90 : * @DMA_RESV_USAGE_READ: Implicit read synchronization.
91 : *
92 : * This should only be used for userspace command submissions which add
93 : * an implicit read dependency.
94 : */
95 : DMA_RESV_USAGE_READ,
96 :
97 : /**
98 : * @DMA_RESV_USAGE_BOOKKEEP: No implicit sync.
99 : *
100 : * This should be used by submissions which don't want to participate in
101 : * implicit synchronization.
102 : *
103 : * The most common case are preemption fences as well as page table
104 : * updates and their TLB flushes.
105 : */
106 : DMA_RESV_USAGE_BOOKKEEP
107 : };
108 :
109 : /**
110 : * dma_resv_usage_rw - helper for implicit sync
111 : * @write: true if we create a new implicit sync write
112 : *
113 : * This returns the implicit synchronization usage for write or read accesses,
114 : * see enum dma_resv_usage and &dma_buf.resv.
115 : */
116 : static inline enum dma_resv_usage dma_resv_usage_rw(bool write)
117 : {
118 : /* This looks confusing at first sight, but is indeed correct.
119 : *
120 : * The rational is that new write operations needs to wait for the
121 : * existing read and write operations to finish.
122 : * But a new read operation only needs to wait for the existing write
123 : * operations to finish.
124 : */
125 0 : return write ? DMA_RESV_USAGE_READ : DMA_RESV_USAGE_WRITE;
126 : }
127 :
128 : /**
129 : * struct dma_resv - a reservation object manages fences for a buffer
130 : *
131 : * This is a container for dma_fence objects which needs to handle multiple use
132 : * cases.
133 : *
134 : * One use is to synchronize cross-driver access to a struct dma_buf, either for
135 : * dynamic buffer management or just to handle implicit synchronization between
136 : * different users of the buffer in userspace. See &dma_buf.resv for a more
137 : * in-depth discussion.
138 : *
139 : * The other major use is to manage access and locking within a driver in a
140 : * buffer based memory manager. struct ttm_buffer_object is the canonical
141 : * example here, since this is where reservation objects originated from. But
142 : * use in drivers is spreading and some drivers also manage struct
143 : * drm_gem_object with the same scheme.
144 : */
145 : struct dma_resv {
146 : /**
147 : * @lock:
148 : *
149 : * Update side lock. Don't use directly, instead use the wrapper
150 : * functions like dma_resv_lock() and dma_resv_unlock().
151 : *
152 : * Drivers which use the reservation object to manage memory dynamically
153 : * also use this lock to protect buffer object state like placement,
154 : * allocation policies or throughout command submission.
155 : */
156 : struct ww_mutex lock;
157 :
158 : /**
159 : * @fences:
160 : *
161 : * Array of fences which where added to the dma_resv object
162 : *
163 : * A new fence is added by calling dma_resv_add_fence(). Since this
164 : * often needs to be done past the point of no return in command
165 : * submission it cannot fail, and therefore sufficient slots need to be
166 : * reserved by calling dma_resv_reserve_fences().
167 : */
168 : struct dma_resv_list __rcu *fences;
169 : };
170 :
171 : /**
172 : * struct dma_resv_iter - current position into the dma_resv fences
173 : *
174 : * Don't touch this directly in the driver, use the accessor function instead.
175 : *
176 : * IMPORTANT
177 : *
178 : * When using the lockless iterators like dma_resv_iter_next_unlocked() or
179 : * dma_resv_for_each_fence_unlocked() beware that the iterator can be restarted.
180 : * Code which accumulates statistics or similar needs to check for this with
181 : * dma_resv_iter_is_restarted().
182 : */
183 : struct dma_resv_iter {
184 : /** @obj: The dma_resv object we iterate over */
185 : struct dma_resv *obj;
186 :
187 : /** @usage: Return fences with this usage or lower. */
188 : enum dma_resv_usage usage;
189 :
190 : /** @fence: the currently handled fence */
191 : struct dma_fence *fence;
192 :
193 : /** @fence_usage: the usage of the current fence */
194 : enum dma_resv_usage fence_usage;
195 :
196 : /** @index: index into the shared fences */
197 : unsigned int index;
198 :
199 : /** @fences: the shared fences; private, *MUST* not dereference */
200 : struct dma_resv_list *fences;
201 :
202 : /** @num_fences: number of fences */
203 : unsigned int num_fences;
204 :
205 : /** @is_restarted: true if this is the first returned fence */
206 : bool is_restarted;
207 : };
208 :
209 : struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor);
210 : struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor);
211 : struct dma_fence *dma_resv_iter_first(struct dma_resv_iter *cursor);
212 : struct dma_fence *dma_resv_iter_next(struct dma_resv_iter *cursor);
213 :
214 : /**
215 : * dma_resv_iter_begin - initialize a dma_resv_iter object
216 : * @cursor: The dma_resv_iter object to initialize
217 : * @obj: The dma_resv object which we want to iterate over
218 : * @usage: controls which fences to include, see enum dma_resv_usage.
219 : */
220 : static inline void dma_resv_iter_begin(struct dma_resv_iter *cursor,
221 : struct dma_resv *obj,
222 : enum dma_resv_usage usage)
223 : {
224 0 : cursor->obj = obj;
225 0 : cursor->usage = usage;
226 0 : cursor->fence = NULL;
227 : }
228 :
229 : /**
230 : * dma_resv_iter_end - cleanup a dma_resv_iter object
231 : * @cursor: the dma_resv_iter object which should be cleaned up
232 : *
233 : * Make sure that the reference to the fence in the cursor is properly
234 : * dropped.
235 : */
236 : static inline void dma_resv_iter_end(struct dma_resv_iter *cursor)
237 : {
238 0 : dma_fence_put(cursor->fence);
239 : }
240 :
241 : /**
242 : * dma_resv_iter_usage - Return the usage of the current fence
243 : * @cursor: the cursor of the current position
244 : *
245 : * Returns the usage of the currently processed fence.
246 : */
247 : static inline enum dma_resv_usage
248 : dma_resv_iter_usage(struct dma_resv_iter *cursor)
249 : {
250 : return cursor->fence_usage;
251 : }
252 :
253 : /**
254 : * dma_resv_iter_is_restarted - test if this is the first fence after a restart
255 : * @cursor: the cursor with the current position
256 : *
257 : * Return true if this is the first fence in an iteration after a restart.
258 : */
259 : static inline bool dma_resv_iter_is_restarted(struct dma_resv_iter *cursor)
260 : {
261 : return cursor->is_restarted;
262 : }
263 :
264 : /**
265 : * dma_resv_for_each_fence_unlocked - unlocked fence iterator
266 : * @cursor: a struct dma_resv_iter pointer
267 : * @fence: the current fence
268 : *
269 : * Iterate over the fences in a struct dma_resv object without holding the
270 : * &dma_resv.lock and using RCU instead. The cursor needs to be initialized
271 : * with dma_resv_iter_begin() and cleaned up with dma_resv_iter_end(). Inside
272 : * the iterator a reference to the dma_fence is held and the RCU lock dropped.
273 : *
274 : * Beware that the iterator can be restarted when the struct dma_resv for
275 : * @cursor is modified. Code which accumulates statistics or similar needs to
276 : * check for this with dma_resv_iter_is_restarted(). For this reason prefer the
277 : * lock iterator dma_resv_for_each_fence() whenever possible.
278 : */
279 : #define dma_resv_for_each_fence_unlocked(cursor, fence) \
280 : for (fence = dma_resv_iter_first_unlocked(cursor); \
281 : fence; fence = dma_resv_iter_next_unlocked(cursor))
282 :
283 : /**
284 : * dma_resv_for_each_fence - fence iterator
285 : * @cursor: a struct dma_resv_iter pointer
286 : * @obj: a dma_resv object pointer
287 : * @usage: controls which fences to return
288 : * @fence: the current fence
289 : *
290 : * Iterate over the fences in a struct dma_resv object while holding the
291 : * &dma_resv.lock. @all_fences controls if the shared fences are returned as
292 : * well. The cursor initialisation is part of the iterator and the fence stays
293 : * valid as long as the lock is held and so no extra reference to the fence is
294 : * taken.
295 : */
296 : #define dma_resv_for_each_fence(cursor, obj, usage, fence) \
297 : for (dma_resv_iter_begin(cursor, obj, usage), \
298 : fence = dma_resv_iter_first(cursor); fence; \
299 : fence = dma_resv_iter_next(cursor))
300 :
301 : #define dma_resv_held(obj) lockdep_is_held(&(obj)->lock.base)
302 : #define dma_resv_assert_held(obj) lockdep_assert_held(&(obj)->lock.base)
303 :
304 : #ifdef CONFIG_DEBUG_MUTEXES
305 : void dma_resv_reset_max_fences(struct dma_resv *obj);
306 : #else
307 : static inline void dma_resv_reset_max_fences(struct dma_resv *obj) {}
308 : #endif
309 :
310 : /**
311 : * dma_resv_lock - lock the reservation object
312 : * @obj: the reservation object
313 : * @ctx: the locking context
314 : *
315 : * Locks the reservation object for exclusive access and modification. Note,
316 : * that the lock is only against other writers, readers will run concurrently
317 : * with a writer under RCU. The seqlock is used to notify readers if they
318 : * overlap with a writer.
319 : *
320 : * As the reservation object may be locked by multiple parties in an
321 : * undefined order, a #ww_acquire_ctx is passed to unwind if a cycle
322 : * is detected. See ww_mutex_lock() and ww_acquire_init(). A reservation
323 : * object may be locked by itself by passing NULL as @ctx.
324 : *
325 : * When a die situation is indicated by returning -EDEADLK all locks held by
326 : * @ctx must be unlocked and then dma_resv_lock_slow() called on @obj.
327 : *
328 : * Unlocked by calling dma_resv_unlock().
329 : *
330 : * See also dma_resv_lock_interruptible() for the interruptible variant.
331 : */
332 : static inline int dma_resv_lock(struct dma_resv *obj,
333 : struct ww_acquire_ctx *ctx)
334 : {
335 0 : return ww_mutex_lock(&obj->lock, ctx);
336 : }
337 :
338 : /**
339 : * dma_resv_lock_interruptible - lock the reservation object
340 : * @obj: the reservation object
341 : * @ctx: the locking context
342 : *
343 : * Locks the reservation object interruptible for exclusive access and
344 : * modification. Note, that the lock is only against other writers, readers
345 : * will run concurrently with a writer under RCU. The seqlock is used to
346 : * notify readers if they overlap with a writer.
347 : *
348 : * As the reservation object may be locked by multiple parties in an
349 : * undefined order, a #ww_acquire_ctx is passed to unwind if a cycle
350 : * is detected. See ww_mutex_lock() and ww_acquire_init(). A reservation
351 : * object may be locked by itself by passing NULL as @ctx.
352 : *
353 : * When a die situation is indicated by returning -EDEADLK all locks held by
354 : * @ctx must be unlocked and then dma_resv_lock_slow_interruptible() called on
355 : * @obj.
356 : *
357 : * Unlocked by calling dma_resv_unlock().
358 : */
359 : static inline int dma_resv_lock_interruptible(struct dma_resv *obj,
360 : struct ww_acquire_ctx *ctx)
361 : {
362 0 : return ww_mutex_lock_interruptible(&obj->lock, ctx);
363 : }
364 :
365 : /**
366 : * dma_resv_lock_slow - slowpath lock the reservation object
367 : * @obj: the reservation object
368 : * @ctx: the locking context
369 : *
370 : * Acquires the reservation object after a die case. This function
371 : * will sleep until the lock becomes available. See dma_resv_lock() as
372 : * well.
373 : *
374 : * See also dma_resv_lock_slow_interruptible() for the interruptible variant.
375 : */
376 : static inline void dma_resv_lock_slow(struct dma_resv *obj,
377 : struct ww_acquire_ctx *ctx)
378 : {
379 0 : ww_mutex_lock_slow(&obj->lock, ctx);
380 : }
381 :
382 : /**
383 : * dma_resv_lock_slow_interruptible - slowpath lock the reservation
384 : * object, interruptible
385 : * @obj: the reservation object
386 : * @ctx: the locking context
387 : *
388 : * Acquires the reservation object interruptible after a die case. This function
389 : * will sleep until the lock becomes available. See
390 : * dma_resv_lock_interruptible() as well.
391 : */
392 : static inline int dma_resv_lock_slow_interruptible(struct dma_resv *obj,
393 : struct ww_acquire_ctx *ctx)
394 : {
395 0 : return ww_mutex_lock_slow_interruptible(&obj->lock, ctx);
396 : }
397 :
398 : /**
399 : * dma_resv_trylock - trylock the reservation object
400 : * @obj: the reservation object
401 : *
402 : * Tries to lock the reservation object for exclusive access and modification.
403 : * Note, that the lock is only against other writers, readers will run
404 : * concurrently with a writer under RCU. The seqlock is used to notify readers
405 : * if they overlap with a writer.
406 : *
407 : * Also note that since no context is provided, no deadlock protection is
408 : * possible, which is also not needed for a trylock.
409 : *
410 : * Returns true if the lock was acquired, false otherwise.
411 : */
412 : static inline bool __must_check dma_resv_trylock(struct dma_resv *obj)
413 : {
414 0 : return ww_mutex_trylock(&obj->lock, NULL);
415 : }
416 :
417 : /**
418 : * dma_resv_is_locked - is the reservation object locked
419 : * @obj: the reservation object
420 : *
421 : * Returns true if the mutex is locked, false if unlocked.
422 : */
423 : static inline bool dma_resv_is_locked(struct dma_resv *obj)
424 : {
425 0 : return ww_mutex_is_locked(&obj->lock);
426 : }
427 :
428 : /**
429 : * dma_resv_locking_ctx - returns the context used to lock the object
430 : * @obj: the reservation object
431 : *
432 : * Returns the context used to lock a reservation object or NULL if no context
433 : * was used or the object is not locked at all.
434 : *
435 : * WARNING: This interface is pretty horrible, but TTM needs it because it
436 : * doesn't pass the struct ww_acquire_ctx around in some very long callchains.
437 : * Everyone else just uses it to check whether they're holding a reservation or
438 : * not.
439 : */
440 : static inline struct ww_acquire_ctx *dma_resv_locking_ctx(struct dma_resv *obj)
441 : {
442 0 : return READ_ONCE(obj->lock.ctx);
443 : }
444 :
445 : /**
446 : * dma_resv_unlock - unlock the reservation object
447 : * @obj: the reservation object
448 : *
449 : * Unlocks the reservation object following exclusive access.
450 : */
451 : static inline void dma_resv_unlock(struct dma_resv *obj)
452 : {
453 0 : dma_resv_reset_max_fences(obj);
454 0 : ww_mutex_unlock(&obj->lock);
455 : }
456 :
457 : void dma_resv_init(struct dma_resv *obj);
458 : void dma_resv_fini(struct dma_resv *obj);
459 : int dma_resv_reserve_fences(struct dma_resv *obj, unsigned int num_fences);
460 : void dma_resv_add_fence(struct dma_resv *obj, struct dma_fence *fence,
461 : enum dma_resv_usage usage);
462 : void dma_resv_replace_fences(struct dma_resv *obj, uint64_t context,
463 : struct dma_fence *fence,
464 : enum dma_resv_usage usage);
465 : int dma_resv_get_fences(struct dma_resv *obj, enum dma_resv_usage usage,
466 : unsigned int *num_fences, struct dma_fence ***fences);
467 : int dma_resv_get_singleton(struct dma_resv *obj, enum dma_resv_usage usage,
468 : struct dma_fence **fence);
469 : int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src);
470 : long dma_resv_wait_timeout(struct dma_resv *obj, enum dma_resv_usage usage,
471 : bool intr, unsigned long timeout);
472 : bool dma_resv_test_signaled(struct dma_resv *obj, enum dma_resv_usage usage);
473 : void dma_resv_describe(struct dma_resv *obj, struct seq_file *seq);
474 :
475 : #endif /* _LINUX_RESERVATION_H */
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