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
48extern struct ww_class reservation_ww_class;
49
50struct 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 */
71enum 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 cases are preemption fences, page table updates, TLB
109 * flushes as well as explicitly synced user submissions.
110 *
111 * Explicitly synced 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 */
126static 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 */
155struct 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 */
193struct 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
219struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor);
220struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor);
221struct dma_fence *dma_resv_iter_first(struct dma_resv_iter *cursor);
222struct 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 */
230static 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 */
246static 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 */
257static inline enum dma_resv_usage
258dma_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 */
269static 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
315void dma_resv_reset_max_fences(struct dma_resv *obj);
316#else
317static 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 */
342static 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 */
369static 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 */
386static 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 */
402static 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 */
422static 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 */
433static 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 */
450static 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 */
461static 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
467void dma_resv_init(struct dma_resv *obj);
468void dma_resv_fini(struct dma_resv *obj);
469int dma_resv_reserve_fences(struct dma_resv *obj, unsigned int num_fences);
470void dma_resv_add_fence(struct dma_resv *obj, struct dma_fence *fence,
471 enum dma_resv_usage usage);
472void dma_resv_replace_fences(struct dma_resv *obj, uint64_t context,
473 struct dma_fence *fence,
474 enum dma_resv_usage usage);
475int dma_resv_get_fences(struct dma_resv *obj, enum dma_resv_usage usage,
476 unsigned int *num_fences, struct dma_fence ***fences);
477int dma_resv_get_singleton(struct dma_resv *obj, enum dma_resv_usage usage,
478 struct dma_fence **fence);
479int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src);
480long dma_resv_wait_timeout(struct dma_resv *obj, enum dma_resv_usage usage,
481 bool intr, unsigned long timeout);
482void dma_resv_set_deadline(struct dma_resv *obj, enum dma_resv_usage usage,
483 ktime_t deadline);
484bool dma_resv_test_signaled(struct dma_resv *obj, enum dma_resv_usage usage);
485void dma_resv_describe(struct dma_resv *obj, struct seq_file *seq);
486
487#endif /* _LINUX_RESERVATION_H */
488

source code of linux/include/linux/dma-resv.h