xref: /linux/include/linux/dma-fence.h (revision 3a07362fab1653d3aca31a9155c8cc776138fd02)
1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3  * Fence mechanism for dma-buf to allow for asynchronous dma access
4  *
5  * Copyright (C) 2012 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  */
12 
13 #ifndef __LINUX_DMA_FENCE_H
14 #define __LINUX_DMA_FENCE_H
15 
16 #include <linux/err.h>
17 #include <linux/wait.h>
18 #include <linux/list.h>
19 #include <linux/bitops.h>
20 #include <linux/kref.h>
21 #include <linux/sched.h>
22 #include <linux/printk.h>
23 #include <linux/rcupdate.h>
24 #include <linux/timekeeping.h>
25 
26 struct dma_fence;
27 struct dma_fence_ops;
28 struct dma_fence_cb;
29 
30 /**
31  * struct dma_fence - software synchronization primitive
32  * @refcount: refcount for this fence
33  * @ops: dma_fence_ops associated with this fence
34  * @rcu: used for releasing fence with kfree_rcu
35  * @cb_list: list of all callbacks to call
36  * @lock: spin_lock_irqsave used for locking
37  * @context: execution context this fence belongs to, returned by
38  *           dma_fence_context_alloc()
39  * @seqno: the sequence number of this fence inside the execution context,
40  * can be compared to decide which fence would be signaled later.
41  * @flags: A mask of DMA_FENCE_FLAG_* defined below
42  * @timestamp: Timestamp when the fence was signaled.
43  * @error: Optional, only valid if < 0, must be set before calling
44  * dma_fence_signal, indicates that the fence has completed with an error.
45  *
46  * the flags member must be manipulated and read using the appropriate
47  * atomic ops (bit_*), so taking the spinlock will not be needed most
48  * of the time.
49  *
50  * DMA_FENCE_FLAG_SIGNALED_BIT - fence is already signaled
51  * DMA_FENCE_FLAG_TIMESTAMP_BIT - timestamp recorded for fence signaling
52  * DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT - enable_signaling might have been called
53  * DMA_FENCE_FLAG_USER_BITS - start of the unused bits, can be used by the
54  * implementer of the fence for its own purposes. Can be used in different
55  * ways by different fence implementers, so do not rely on this.
56  *
57  * Since atomic bitops are used, this is not guaranteed to be the case.
58  * Particularly, if the bit was set, but dma_fence_signal was called right
59  * before this bit was set, it would have been able to set the
60  * DMA_FENCE_FLAG_SIGNALED_BIT, before enable_signaling was called.
61  * Adding a check for DMA_FENCE_FLAG_SIGNALED_BIT after setting
62  * DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT closes this race, and makes sure that
63  * after dma_fence_signal was called, any enable_signaling call will have either
64  * been completed, or never called at all.
65  */
66 struct dma_fence {
67 	spinlock_t *lock;
68 	const struct dma_fence_ops *ops;
69 	/*
70 	 * We clear the callback list on kref_put so that by the time we
71 	 * release the fence it is unused. No one should be adding to the
72 	 * cb_list that they don't themselves hold a reference for.
73 	 *
74 	 * The lifetime of the timestamp is similarly tied to both the
75 	 * rcu freelist and the cb_list. The timestamp is only set upon
76 	 * signaling while simultaneously notifying the cb_list. Ergo, we
77 	 * only use either the cb_list of timestamp. Upon destruction,
78 	 * neither are accessible, and so we can use the rcu. This means
79 	 * that the cb_list is *only* valid until the signal bit is set,
80 	 * and to read either you *must* hold a reference to the fence,
81 	 * and not just the rcu_read_lock.
82 	 *
83 	 * Listed in chronological order.
84 	 */
85 	union {
86 		struct list_head cb_list;
87 		/* @cb_list replaced by @timestamp on dma_fence_signal() */
88 		ktime_t timestamp;
89 		/* @timestamp replaced by @rcu on dma_fence_release() */
90 		struct rcu_head rcu;
91 	};
92 	u64 context;
93 	u64 seqno;
94 	unsigned long flags;
95 	struct kref refcount;
96 	int error;
97 };
98 
99 enum dma_fence_flag_bits {
100 	DMA_FENCE_FLAG_SIGNALED_BIT,
101 	DMA_FENCE_FLAG_TIMESTAMP_BIT,
102 	DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
103 	DMA_FENCE_FLAG_USER_BITS, /* must always be last member */
104 };
105 
106 typedef void (*dma_fence_func_t)(struct dma_fence *fence,
107 				 struct dma_fence_cb *cb);
108 
109 /**
110  * struct dma_fence_cb - callback for dma_fence_add_callback()
111  * @node: used by dma_fence_add_callback() to append this struct to fence::cb_list
112  * @func: dma_fence_func_t to call
113  *
114  * This struct will be initialized by dma_fence_add_callback(), additional
115  * data can be passed along by embedding dma_fence_cb in another struct.
116  */
117 struct dma_fence_cb {
118 	struct list_head node;
119 	dma_fence_func_t func;
120 };
121 
122 /**
123  * struct dma_fence_ops - operations implemented for fence
124  *
125  */
126 struct dma_fence_ops {
127 	/**
128 	 * @use_64bit_seqno:
129 	 *
130 	 * True if this dma_fence implementation uses 64bit seqno, false
131 	 * otherwise.
132 	 */
133 	bool use_64bit_seqno;
134 
135 	/**
136 	 * @get_driver_name:
137 	 *
138 	 * Returns the driver name. This is a callback to allow drivers to
139 	 * compute the name at runtime, without having it to store permanently
140 	 * for each fence, or build a cache of some sort.
141 	 *
142 	 * This callback is mandatory.
143 	 */
144 	const char * (*get_driver_name)(struct dma_fence *fence);
145 
146 	/**
147 	 * @get_timeline_name:
148 	 *
149 	 * Return the name of the context this fence belongs to. This is a
150 	 * callback to allow drivers to compute the name at runtime, without
151 	 * having it to store permanently for each fence, or build a cache of
152 	 * some sort.
153 	 *
154 	 * This callback is mandatory.
155 	 */
156 	const char * (*get_timeline_name)(struct dma_fence *fence);
157 
158 	/**
159 	 * @enable_signaling:
160 	 *
161 	 * Enable software signaling of fence.
162 	 *
163 	 * For fence implementations that have the capability for hw->hw
164 	 * signaling, they can implement this op to enable the necessary
165 	 * interrupts, or insert commands into cmdstream, etc, to avoid these
166 	 * costly operations for the common case where only hw->hw
167 	 * synchronization is required.  This is called in the first
168 	 * dma_fence_wait() or dma_fence_add_callback() path to let the fence
169 	 * implementation know that there is another driver waiting on the
170 	 * signal (ie. hw->sw case).
171 	 *
172 	 * This function can be called from atomic context, but not
173 	 * from irq context, so normal spinlocks can be used.
174 	 *
175 	 * A return value of false indicates the fence already passed,
176 	 * or some failure occurred that made it impossible to enable
177 	 * signaling. True indicates successful enabling.
178 	 *
179 	 * &dma_fence.error may be set in enable_signaling, but only when false
180 	 * is returned.
181 	 *
182 	 * Since many implementations can call dma_fence_signal() even when before
183 	 * @enable_signaling has been called there's a race window, where the
184 	 * dma_fence_signal() might result in the final fence reference being
185 	 * released and its memory freed. To avoid this, implementations of this
186 	 * callback should grab their own reference using dma_fence_get(), to be
187 	 * released when the fence is signalled (through e.g. the interrupt
188 	 * handler).
189 	 *
190 	 * This callback is optional. If this callback is not present, then the
191 	 * driver must always have signaling enabled.
192 	 */
193 	bool (*enable_signaling)(struct dma_fence *fence);
194 
195 	/**
196 	 * @signaled:
197 	 *
198 	 * Peek whether the fence is signaled, as a fastpath optimization for
199 	 * e.g. dma_fence_wait() or dma_fence_add_callback(). Note that this
200 	 * callback does not need to make any guarantees beyond that a fence
201 	 * once indicates as signalled must always return true from this
202 	 * callback. This callback may return false even if the fence has
203 	 * completed already, in this case information hasn't propogated throug
204 	 * the system yet. See also dma_fence_is_signaled().
205 	 *
206 	 * May set &dma_fence.error if returning true.
207 	 *
208 	 * This callback is optional.
209 	 */
210 	bool (*signaled)(struct dma_fence *fence);
211 
212 	/**
213 	 * @wait:
214 	 *
215 	 * Custom wait implementation, defaults to dma_fence_default_wait() if
216 	 * not set.
217 	 *
218 	 * Deprecated and should not be used by new implementations. Only used
219 	 * by existing implementations which need special handling for their
220 	 * hardware reset procedure.
221 	 *
222 	 * Must return -ERESTARTSYS if the wait is intr = true and the wait was
223 	 * interrupted, and remaining jiffies if fence has signaled, or 0 if wait
224 	 * timed out. Can also return other error values on custom implementations,
225 	 * which should be treated as if the fence is signaled. For example a hardware
226 	 * lockup could be reported like that.
227 	 */
228 	signed long (*wait)(struct dma_fence *fence,
229 			    bool intr, signed long timeout);
230 
231 	/**
232 	 * @release:
233 	 *
234 	 * Called on destruction of fence to release additional resources.
235 	 * Can be called from irq context.  This callback is optional. If it is
236 	 * NULL, then dma_fence_free() is instead called as the default
237 	 * implementation.
238 	 */
239 	void (*release)(struct dma_fence *fence);
240 
241 	/**
242 	 * @fence_value_str:
243 	 *
244 	 * Callback to fill in free-form debug info specific to this fence, like
245 	 * the sequence number.
246 	 *
247 	 * This callback is optional.
248 	 */
249 	void (*fence_value_str)(struct dma_fence *fence, char *str, int size);
250 
251 	/**
252 	 * @timeline_value_str:
253 	 *
254 	 * Fills in the current value of the timeline as a string, like the
255 	 * sequence number. Note that the specific fence passed to this function
256 	 * should not matter, drivers should only use it to look up the
257 	 * corresponding timeline structures.
258 	 */
259 	void (*timeline_value_str)(struct dma_fence *fence,
260 				   char *str, int size);
261 
262 	/**
263 	 * @set_deadline:
264 	 *
265 	 * Callback to allow a fence waiter to inform the fence signaler of
266 	 * an upcoming deadline, such as vblank, by which point the waiter
267 	 * would prefer the fence to be signaled by.  This is intended to
268 	 * give feedback to the fence signaler to aid in power management
269 	 * decisions, such as boosting GPU frequency.
270 	 *
271 	 * This is called without &dma_fence.lock held, it can be called
272 	 * multiple times and from any context.  Locking is up to the callee
273 	 * if it has some state to manage.  If multiple deadlines are set,
274 	 * the expectation is to track the soonest one.  If the deadline is
275 	 * before the current time, it should be interpreted as an immediate
276 	 * deadline.
277 	 *
278 	 * This callback is optional.
279 	 */
280 	void (*set_deadline)(struct dma_fence *fence, ktime_t deadline);
281 };
282 
283 void dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops,
284 		    spinlock_t *lock, u64 context, u64 seqno);
285 
286 void dma_fence_release(struct kref *kref);
287 void dma_fence_free(struct dma_fence *fence);
288 void dma_fence_describe(struct dma_fence *fence, struct seq_file *seq);
289 
290 /**
291  * dma_fence_put - decreases refcount of the fence
292  * @fence: fence to reduce refcount of
293  */
dma_fence_put(struct dma_fence * fence)294 static inline void dma_fence_put(struct dma_fence *fence)
295 {
296 	if (fence)
297 		kref_put(&fence->refcount, dma_fence_release);
298 }
299 
300 /**
301  * dma_fence_get - increases refcount of the fence
302  * @fence: fence to increase refcount of
303  *
304  * Returns the same fence, with refcount increased by 1.
305  */
dma_fence_get(struct dma_fence * fence)306 static inline struct dma_fence *dma_fence_get(struct dma_fence *fence)
307 {
308 	if (fence)
309 		kref_get(&fence->refcount);
310 	return fence;
311 }
312 
313 /**
314  * dma_fence_get_rcu - get a fence from a dma_resv_list with
315  *                     rcu read lock
316  * @fence: fence to increase refcount of
317  *
318  * Function returns NULL if no refcount could be obtained, or the fence.
319  */
dma_fence_get_rcu(struct dma_fence * fence)320 static inline struct dma_fence *dma_fence_get_rcu(struct dma_fence *fence)
321 {
322 	if (kref_get_unless_zero(&fence->refcount))
323 		return fence;
324 	else
325 		return NULL;
326 }
327 
328 /**
329  * dma_fence_get_rcu_safe  - acquire a reference to an RCU tracked fence
330  * @fencep: pointer to fence to increase refcount of
331  *
332  * Function returns NULL if no refcount could be obtained, or the fence.
333  * This function handles acquiring a reference to a fence that may be
334  * reallocated within the RCU grace period (such as with SLAB_TYPESAFE_BY_RCU),
335  * so long as the caller is using RCU on the pointer to the fence.
336  *
337  * An alternative mechanism is to employ a seqlock to protect a bunch of
338  * fences, such as used by struct dma_resv. When using a seqlock,
339  * the seqlock must be taken before and checked after a reference to the
340  * fence is acquired (as shown here).
341  *
342  * The caller is required to hold the RCU read lock.
343  */
344 static inline struct dma_fence *
dma_fence_get_rcu_safe(struct dma_fence __rcu ** fencep)345 dma_fence_get_rcu_safe(struct dma_fence __rcu **fencep)
346 {
347 	do {
348 		struct dma_fence *fence;
349 
350 		fence = rcu_dereference(*fencep);
351 		if (!fence)
352 			return NULL;
353 
354 		if (!dma_fence_get_rcu(fence))
355 			continue;
356 
357 		/* The atomic_inc_not_zero() inside dma_fence_get_rcu()
358 		 * provides a full memory barrier upon success (such as now).
359 		 * This is paired with the write barrier from assigning
360 		 * to the __rcu protected fence pointer so that if that
361 		 * pointer still matches the current fence, we know we
362 		 * have successfully acquire a reference to it. If it no
363 		 * longer matches, we are holding a reference to some other
364 		 * reallocated pointer. This is possible if the allocator
365 		 * is using a freelist like SLAB_TYPESAFE_BY_RCU where the
366 		 * fence remains valid for the RCU grace period, but it
367 		 * may be reallocated. When using such allocators, we are
368 		 * responsible for ensuring the reference we get is to
369 		 * the right fence, as below.
370 		 */
371 		if (fence == rcu_access_pointer(*fencep))
372 			return rcu_pointer_handoff(fence);
373 
374 		dma_fence_put(fence);
375 	} while (1);
376 }
377 
378 #ifdef CONFIG_LOCKDEP
379 bool dma_fence_begin_signalling(void);
380 void dma_fence_end_signalling(bool cookie);
381 void __dma_fence_might_wait(void);
382 #else
dma_fence_begin_signalling(void)383 static inline bool dma_fence_begin_signalling(void)
384 {
385 	return true;
386 }
dma_fence_end_signalling(bool cookie)387 static inline void dma_fence_end_signalling(bool cookie) {}
__dma_fence_might_wait(void)388 static inline void __dma_fence_might_wait(void) {}
389 #endif
390 
391 int dma_fence_signal(struct dma_fence *fence);
392 int dma_fence_signal_locked(struct dma_fence *fence);
393 int dma_fence_signal_timestamp(struct dma_fence *fence, ktime_t timestamp);
394 int dma_fence_signal_timestamp_locked(struct dma_fence *fence,
395 				      ktime_t timestamp);
396 signed long dma_fence_default_wait(struct dma_fence *fence,
397 				   bool intr, signed long timeout);
398 int dma_fence_add_callback(struct dma_fence *fence,
399 			   struct dma_fence_cb *cb,
400 			   dma_fence_func_t func);
401 bool dma_fence_remove_callback(struct dma_fence *fence,
402 			       struct dma_fence_cb *cb);
403 void dma_fence_enable_sw_signaling(struct dma_fence *fence);
404 
405 /**
406  * dma_fence_is_signaled_locked - Return an indication if the fence
407  *                                is signaled yet.
408  * @fence: the fence to check
409  *
410  * Returns true if the fence was already signaled, false if not. Since this
411  * function doesn't enable signaling, it is not guaranteed to ever return
412  * true if dma_fence_add_callback(), dma_fence_wait() or
413  * dma_fence_enable_sw_signaling() haven't been called before.
414  *
415  * This function requires &dma_fence.lock to be held.
416  *
417  * See also dma_fence_is_signaled().
418  */
419 static inline bool
dma_fence_is_signaled_locked(struct dma_fence * fence)420 dma_fence_is_signaled_locked(struct dma_fence *fence)
421 {
422 	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
423 		return true;
424 
425 	if (fence->ops->signaled && fence->ops->signaled(fence)) {
426 		dma_fence_signal_locked(fence);
427 		return true;
428 	}
429 
430 	return false;
431 }
432 
433 /**
434  * dma_fence_is_signaled - Return an indication if the fence is signaled yet.
435  * @fence: the fence to check
436  *
437  * Returns true if the fence was already signaled, false if not. Since this
438  * function doesn't enable signaling, it is not guaranteed to ever return
439  * true if dma_fence_add_callback(), dma_fence_wait() or
440  * dma_fence_enable_sw_signaling() haven't been called before.
441  *
442  * It's recommended for seqno fences to call dma_fence_signal when the
443  * operation is complete, it makes it possible to prevent issues from
444  * wraparound between time of issue and time of use by checking the return
445  * value of this function before calling hardware-specific wait instructions.
446  *
447  * See also dma_fence_is_signaled_locked().
448  */
449 static inline bool
dma_fence_is_signaled(struct dma_fence * fence)450 dma_fence_is_signaled(struct dma_fence *fence)
451 {
452 	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
453 		return true;
454 
455 	if (fence->ops->signaled && fence->ops->signaled(fence)) {
456 		dma_fence_signal(fence);
457 		return true;
458 	}
459 
460 	return false;
461 }
462 
463 /**
464  * __dma_fence_is_later - return if f1 is chronologically later than f2
465  * @f1: the first fence's seqno
466  * @f2: the second fence's seqno from the same context
467  * @ops: dma_fence_ops associated with the seqno
468  *
469  * Returns true if f1 is chronologically later than f2. Both fences must be
470  * from the same context, since a seqno is not common across contexts.
471  */
__dma_fence_is_later(u64 f1,u64 f2,const struct dma_fence_ops * ops)472 static inline bool __dma_fence_is_later(u64 f1, u64 f2,
473 					const struct dma_fence_ops *ops)
474 {
475 	/* This is for backward compatibility with drivers which can only handle
476 	 * 32bit sequence numbers. Use a 64bit compare when the driver says to
477 	 * do so.
478 	 */
479 	if (ops->use_64bit_seqno)
480 		return f1 > f2;
481 
482 	return (int)(lower_32_bits(f1) - lower_32_bits(f2)) > 0;
483 }
484 
485 /**
486  * dma_fence_is_later - return if f1 is chronologically later than f2
487  * @f1: the first fence from the same context
488  * @f2: the second fence from the same context
489  *
490  * Returns true if f1 is chronologically later than f2. Both fences must be
491  * from the same context, since a seqno is not re-used across contexts.
492  */
dma_fence_is_later(struct dma_fence * f1,struct dma_fence * f2)493 static inline bool dma_fence_is_later(struct dma_fence *f1,
494 				      struct dma_fence *f2)
495 {
496 	if (WARN_ON(f1->context != f2->context))
497 		return false;
498 
499 	return __dma_fence_is_later(f1->seqno, f2->seqno, f1->ops);
500 }
501 
502 /**
503  * dma_fence_is_later_or_same - return true if f1 is later or same as f2
504  * @f1: the first fence from the same context
505  * @f2: the second fence from the same context
506  *
507  * Returns true if f1 is chronologically later than f2 or the same fence. Both
508  * fences must be from the same context, since a seqno is not re-used across
509  * contexts.
510  */
dma_fence_is_later_or_same(struct dma_fence * f1,struct dma_fence * f2)511 static inline bool dma_fence_is_later_or_same(struct dma_fence *f1,
512 					      struct dma_fence *f2)
513 {
514 	return f1 == f2 || dma_fence_is_later(f1, f2);
515 }
516 
517 /**
518  * dma_fence_later - return the chronologically later fence
519  * @f1:	the first fence from the same context
520  * @f2:	the second fence from the same context
521  *
522  * Returns NULL if both fences are signaled, otherwise the fence that would be
523  * signaled last. Both fences must be from the same context, since a seqno is
524  * not re-used across contexts.
525  */
dma_fence_later(struct dma_fence * f1,struct dma_fence * f2)526 static inline struct dma_fence *dma_fence_later(struct dma_fence *f1,
527 						struct dma_fence *f2)
528 {
529 	if (WARN_ON(f1->context != f2->context))
530 		return NULL;
531 
532 	/*
533 	 * Can't check just DMA_FENCE_FLAG_SIGNALED_BIT here, it may never
534 	 * have been set if enable_signaling wasn't called, and enabling that
535 	 * here is overkill.
536 	 */
537 	if (dma_fence_is_later(f1, f2))
538 		return dma_fence_is_signaled(f1) ? NULL : f1;
539 	else
540 		return dma_fence_is_signaled(f2) ? NULL : f2;
541 }
542 
543 /**
544  * dma_fence_get_status_locked - returns the status upon completion
545  * @fence: the dma_fence to query
546  *
547  * Drivers can supply an optional error status condition before they signal
548  * the fence (to indicate whether the fence was completed due to an error
549  * rather than success). The value of the status condition is only valid
550  * if the fence has been signaled, dma_fence_get_status_locked() first checks
551  * the signal state before reporting the error status.
552  *
553  * Returns 0 if the fence has not yet been signaled, 1 if the fence has
554  * been signaled without an error condition, or a negative error code
555  * if the fence has been completed in err.
556  */
dma_fence_get_status_locked(struct dma_fence * fence)557 static inline int dma_fence_get_status_locked(struct dma_fence *fence)
558 {
559 	if (dma_fence_is_signaled_locked(fence))
560 		return fence->error ?: 1;
561 	else
562 		return 0;
563 }
564 
565 int dma_fence_get_status(struct dma_fence *fence);
566 
567 /**
568  * dma_fence_set_error - flag an error condition on the fence
569  * @fence: the dma_fence
570  * @error: the error to store
571  *
572  * Drivers can supply an optional error status condition before they signal
573  * the fence, to indicate that the fence was completed due to an error
574  * rather than success. This must be set before signaling (so that the value
575  * is visible before any waiters on the signal callback are woken). This
576  * helper exists to help catching erroneous setting of #dma_fence.error.
577  */
dma_fence_set_error(struct dma_fence * fence,int error)578 static inline void dma_fence_set_error(struct dma_fence *fence,
579 				       int error)
580 {
581 	WARN_ON(test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags));
582 	WARN_ON(error >= 0 || error < -MAX_ERRNO);
583 
584 	fence->error = error;
585 }
586 
587 /**
588  * dma_fence_timestamp - helper to get the completion timestamp of a fence
589  * @fence: fence to get the timestamp from.
590  *
591  * After a fence is signaled the timestamp is updated with the signaling time,
592  * but setting the timestamp can race with tasks waiting for the signaling. This
593  * helper busy waits for the correct timestamp to appear.
594  */
dma_fence_timestamp(struct dma_fence * fence)595 static inline ktime_t dma_fence_timestamp(struct dma_fence *fence)
596 {
597 	if (WARN_ON(!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)))
598 		return ktime_get();
599 
600 	while (!test_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags))
601 		cpu_relax();
602 
603 	return fence->timestamp;
604 }
605 
606 signed long dma_fence_wait_timeout(struct dma_fence *,
607 				   bool intr, signed long timeout);
608 signed long dma_fence_wait_any_timeout(struct dma_fence **fences,
609 				       uint32_t count,
610 				       bool intr, signed long timeout,
611 				       uint32_t *idx);
612 
613 /**
614  * dma_fence_wait - sleep until the fence gets signaled
615  * @fence: the fence to wait on
616  * @intr: if true, do an interruptible wait
617  *
618  * This function will return -ERESTARTSYS if interrupted by a signal,
619  * or 0 if the fence was signaled. Other error values may be
620  * returned on custom implementations.
621  *
622  * Performs a synchronous wait on this fence. It is assumed the caller
623  * directly or indirectly holds a reference to the fence, otherwise the
624  * fence might be freed before return, resulting in undefined behavior.
625  *
626  * See also dma_fence_wait_timeout() and dma_fence_wait_any_timeout().
627  */
dma_fence_wait(struct dma_fence * fence,bool intr)628 static inline signed long dma_fence_wait(struct dma_fence *fence, bool intr)
629 {
630 	signed long ret;
631 
632 	/* Since dma_fence_wait_timeout cannot timeout with
633 	 * MAX_SCHEDULE_TIMEOUT, only valid return values are
634 	 * -ERESTARTSYS and MAX_SCHEDULE_TIMEOUT.
635 	 */
636 	ret = dma_fence_wait_timeout(fence, intr, MAX_SCHEDULE_TIMEOUT);
637 
638 	return ret < 0 ? ret : 0;
639 }
640 
641 void dma_fence_set_deadline(struct dma_fence *fence, ktime_t deadline);
642 
643 struct dma_fence *dma_fence_get_stub(void);
644 struct dma_fence *dma_fence_allocate_private_stub(ktime_t timestamp);
645 u64 dma_fence_context_alloc(unsigned num);
646 
647 extern const struct dma_fence_ops dma_fence_array_ops;
648 extern const struct dma_fence_ops dma_fence_chain_ops;
649 
650 /**
651  * dma_fence_is_array - check if a fence is from the array subclass
652  * @fence: the fence to test
653  *
654  * Return true if it is a dma_fence_array and false otherwise.
655  */
dma_fence_is_array(struct dma_fence * fence)656 static inline bool dma_fence_is_array(struct dma_fence *fence)
657 {
658 	return fence->ops == &dma_fence_array_ops;
659 }
660 
661 /**
662  * dma_fence_is_chain - check if a fence is from the chain subclass
663  * @fence: the fence to test
664  *
665  * Return true if it is a dma_fence_chain and false otherwise.
666  */
dma_fence_is_chain(struct dma_fence * fence)667 static inline bool dma_fence_is_chain(struct dma_fence *fence)
668 {
669 	return fence->ops == &dma_fence_chain_ops;
670 }
671 
672 /**
673  * dma_fence_is_container - check if a fence is a container for other fences
674  * @fence: the fence to test
675  *
676  * Return true if this fence is a container for other fences, false otherwise.
677  * This is important since we can't build up large fence structure or otherwise
678  * we run into recursion during operation on those fences.
679  */
dma_fence_is_container(struct dma_fence * fence)680 static inline bool dma_fence_is_container(struct dma_fence *fence)
681 {
682 	return dma_fence_is_array(fence) || dma_fence_is_chain(fence);
683 }
684 
685 #endif /* __LINUX_DMA_FENCE_H */
686