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 | 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 | cursor->obj = obj; |
235 | cursor->usage = usage; |
236 | 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 | dma_fence_put(fence: 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 | return ww_mutex_lock(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 | return ww_mutex_lock_interruptible(lock: &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(lock: &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 | return ww_mutex_lock_slow_interruptible(lock: &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 | return ww_mutex_trylock(lock: &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(lock: &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 | dma_resv_reset_max_fences(obj); |
464 | ww_mutex_unlock(lock: &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 | void dma_resv_set_deadline(struct dma_resv *obj, enum dma_resv_usage usage, |
483 | ktime_t deadline); |
484 | bool dma_resv_test_signaled(struct dma_resv *obj, enum dma_resv_usage usage); |
485 | void dma_resv_describe(struct dma_resv *obj, struct seq_file *seq); |
486 | |
487 | #endif /* _LINUX_RESERVATION_H */ |
488 | |