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Linux/include/linux/dma-fence.h

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  1 /*
  2  * Fence mechanism for dma-buf to allow for asynchronous dma access
  3  *
  4  * Copyright (C) 2012 Canonical Ltd
  5  * Copyright (C) 2012 Texas Instruments
  6  *
  7  * Authors:
  8  * Rob Clark <robdclark@gmail.com>
  9  * Maarten Lankhorst <maarten.lankhorst@canonical.com>
 10  *
 11  * This program is free software; you can redistribute it and/or modify it
 12  * under the terms of the GNU General Public License version 2 as published by
 13  * the Free Software Foundation.
 14  *
 15  * This program is distributed in the hope that it will be useful, but WITHOUT
 16  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 17  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 18  * more details.
 19  */
 20 
 21 #ifndef __LINUX_DMA_FENCE_H
 22 #define __LINUX_DMA_FENCE_H
 23 
 24 #include <linux/err.h>
 25 #include <linux/wait.h>
 26 #include <linux/list.h>
 27 #include <linux/bitops.h>
 28 #include <linux/kref.h>
 29 #include <linux/sched.h>
 30 #include <linux/printk.h>
 31 #include <linux/rcupdate.h>
 32 
 33 struct dma_fence;
 34 struct dma_fence_ops;
 35 struct dma_fence_cb;
 36 
 37 /**
 38  * struct dma_fence - software synchronization primitive
 39  * @refcount: refcount for this fence
 40  * @ops: dma_fence_ops associated with this fence
 41  * @rcu: used for releasing fence with kfree_rcu
 42  * @cb_list: list of all callbacks to call
 43  * @lock: spin_lock_irqsave used for locking
 44  * @context: execution context this fence belongs to, returned by
 45  *           dma_fence_context_alloc()
 46  * @seqno: the sequence number of this fence inside the execution context,
 47  * can be compared to decide which fence would be signaled later.
 48  * @flags: A mask of DMA_FENCE_FLAG_* defined below
 49  * @timestamp: Timestamp when the fence was signaled.
 50  * @error: Optional, only valid if < 0, must be set before calling
 51  * dma_fence_signal, indicates that the fence has completed with an error.
 52  *
 53  * the flags member must be manipulated and read using the appropriate
 54  * atomic ops (bit_*), so taking the spinlock will not be needed most
 55  * of the time.
 56  *
 57  * DMA_FENCE_FLAG_SIGNALED_BIT - fence is already signaled
 58  * DMA_FENCE_FLAG_TIMESTAMP_BIT - timestamp recorded for fence signaling
 59  * DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT - enable_signaling might have been called
 60  * DMA_FENCE_FLAG_USER_BITS - start of the unused bits, can be used by the
 61  * implementer of the fence for its own purposes. Can be used in different
 62  * ways by different fence implementers, so do not rely on this.
 63  *
 64  * Since atomic bitops are used, this is not guaranteed to be the case.
 65  * Particularly, if the bit was set, but dma_fence_signal was called right
 66  * before this bit was set, it would have been able to set the
 67  * DMA_FENCE_FLAG_SIGNALED_BIT, before enable_signaling was called.
 68  * Adding a check for DMA_FENCE_FLAG_SIGNALED_BIT after setting
 69  * DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT closes this race, and makes sure that
 70  * after dma_fence_signal was called, any enable_signaling call will have either
 71  * been completed, or never called at all.
 72  */
 73 struct dma_fence {
 74         struct kref refcount;
 75         const struct dma_fence_ops *ops;
 76         struct rcu_head rcu;
 77         struct list_head cb_list;
 78         spinlock_t *lock;
 79         u64 context;
 80         unsigned seqno;
 81         unsigned long flags;
 82         ktime_t timestamp;
 83         int error;
 84 };
 85 
 86 enum dma_fence_flag_bits {
 87         DMA_FENCE_FLAG_SIGNALED_BIT,
 88         DMA_FENCE_FLAG_TIMESTAMP_BIT,
 89         DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
 90         DMA_FENCE_FLAG_USER_BITS, /* must always be last member */
 91 };
 92 
 93 typedef void (*dma_fence_func_t)(struct dma_fence *fence,
 94                                  struct dma_fence_cb *cb);
 95 
 96 /**
 97  * struct dma_fence_cb - callback for dma_fence_add_callback
 98  * @node: used by dma_fence_add_callback to append this struct to fence::cb_list
 99  * @func: dma_fence_func_t to call
100  *
101  * This struct will be initialized by dma_fence_add_callback, additional
102  * data can be passed along by embedding dma_fence_cb in another struct.
103  */
104 struct dma_fence_cb {
105         struct list_head node;
106         dma_fence_func_t func;
107 };
108 
109 /**
110  * struct dma_fence_ops - operations implemented for fence
111  * @get_driver_name: returns the driver name.
112  * @get_timeline_name: return the name of the context this fence belongs to.
113  * @enable_signaling: enable software signaling of fence.
114  * @signaled: [optional] peek whether the fence is signaled, can be null.
115  * @wait: custom wait implementation, or dma_fence_default_wait.
116  * @release: [optional] called on destruction of fence, can be null
117  * @fill_driver_data: [optional] callback to fill in free-form debug info
118  * Returns amount of bytes filled, or -errno.
119  * @fence_value_str: [optional] fills in the value of the fence as a string
120  * @timeline_value_str: [optional] fills in the current value of the timeline
121  * as a string
122  *
123  * Notes on enable_signaling:
124  * For fence implementations that have the capability for hw->hw
125  * signaling, they can implement this op to enable the necessary
126  * irqs, or insert commands into cmdstream, etc.  This is called
127  * in the first wait() or add_callback() path to let the fence
128  * implementation know that there is another driver waiting on
129  * the signal (ie. hw->sw case).
130  *
131  * This function can be called called from atomic context, but not
132  * from irq context, so normal spinlocks can be used.
133  *
134  * A return value of false indicates the fence already passed,
135  * or some failure occurred that made it impossible to enable
136  * signaling. True indicates successful enabling.
137  *
138  * fence->error may be set in enable_signaling, but only when false is
139  * returned.
140  *
141  * Calling dma_fence_signal before enable_signaling is called allows
142  * for a tiny race window in which enable_signaling is called during,
143  * before, or after dma_fence_signal. To fight this, it is recommended
144  * that before enable_signaling returns true an extra reference is
145  * taken on the fence, to be released when the fence is signaled.
146  * This will mean dma_fence_signal will still be called twice, but
147  * the second time will be a noop since it was already signaled.
148  *
149  * Notes on signaled:
150  * May set fence->error if returning true.
151  *
152  * Notes on wait:
153  * Must not be NULL, set to dma_fence_default_wait for default implementation.
154  * the dma_fence_default_wait implementation should work for any fence, as long
155  * as enable_signaling works correctly.
156  *
157  * Must return -ERESTARTSYS if the wait is intr = true and the wait was
158  * interrupted, and remaining jiffies if fence has signaled, or 0 if wait
159  * timed out. Can also return other error values on custom implementations,
160  * which should be treated as if the fence is signaled. For example a hardware
161  * lockup could be reported like that.
162  *
163  * Notes on release:
164  * Can be NULL, this function allows additional commands to run on
165  * destruction of the fence. Can be called from irq context.
166  * If pointer is set to NULL, kfree will get called instead.
167  */
168 
169 struct dma_fence_ops {
170         const char * (*get_driver_name)(struct dma_fence *fence);
171         const char * (*get_timeline_name)(struct dma_fence *fence);
172         bool (*enable_signaling)(struct dma_fence *fence);
173         bool (*signaled)(struct dma_fence *fence);
174         signed long (*wait)(struct dma_fence *fence,
175                             bool intr, signed long timeout);
176         void (*release)(struct dma_fence *fence);
177 
178         int (*fill_driver_data)(struct dma_fence *fence, void *data, int size);
179         void (*fence_value_str)(struct dma_fence *fence, char *str, int size);
180         void (*timeline_value_str)(struct dma_fence *fence,
181                                    char *str, int size);
182 };
183 
184 void dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops,
185                     spinlock_t *lock, u64 context, unsigned seqno);
186 
187 void dma_fence_release(struct kref *kref);
188 void dma_fence_free(struct dma_fence *fence);
189 
190 /**
191  * dma_fence_put - decreases refcount of the fence
192  * @fence:      [in]    fence to reduce refcount of
193  */
194 static inline void dma_fence_put(struct dma_fence *fence)
195 {
196         if (fence)
197                 kref_put(&fence->refcount, dma_fence_release);
198 }
199 
200 /**
201  * dma_fence_get - increases refcount of the fence
202  * @fence:      [in]    fence to increase refcount of
203  *
204  * Returns the same fence, with refcount increased by 1.
205  */
206 static inline struct dma_fence *dma_fence_get(struct dma_fence *fence)
207 {
208         if (fence)
209                 kref_get(&fence->refcount);
210         return fence;
211 }
212 
213 /**
214  * dma_fence_get_rcu - get a fence from a reservation_object_list with
215  *                     rcu read lock
216  * @fence:      [in]    fence to increase refcount of
217  *
218  * Function returns NULL if no refcount could be obtained, or the fence.
219  */
220 static inline struct dma_fence *dma_fence_get_rcu(struct dma_fence *fence)
221 {
222         if (kref_get_unless_zero(&fence->refcount))
223                 return fence;
224         else
225                 return NULL;
226 }
227 
228 /**
229  * dma_fence_get_rcu_safe  - acquire a reference to an RCU tracked fence
230  * @fencep:     [in]    pointer to fence to increase refcount of
231  *
232  * Function returns NULL if no refcount could be obtained, or the fence.
233  * This function handles acquiring a reference to a fence that may be
234  * reallocated within the RCU grace period (such as with SLAB_TYPESAFE_BY_RCU),
235  * so long as the caller is using RCU on the pointer to the fence.
236  *
237  * An alternative mechanism is to employ a seqlock to protect a bunch of
238  * fences, such as used by struct reservation_object. When using a seqlock,
239  * the seqlock must be taken before and checked after a reference to the
240  * fence is acquired (as shown here).
241  *
242  * The caller is required to hold the RCU read lock.
243  */
244 static inline struct dma_fence *
245 dma_fence_get_rcu_safe(struct dma_fence * __rcu *fencep)
246 {
247         do {
248                 struct dma_fence *fence;
249 
250                 fence = rcu_dereference(*fencep);
251                 if (!fence || !dma_fence_get_rcu(fence))
252                         return NULL;
253 
254                 /* The atomic_inc_not_zero() inside dma_fence_get_rcu()
255                  * provides a full memory barrier upon success (such as now).
256                  * This is paired with the write barrier from assigning
257                  * to the __rcu protected fence pointer so that if that
258                  * pointer still matches the current fence, we know we
259                  * have successfully acquire a reference to it. If it no
260                  * longer matches, we are holding a reference to some other
261                  * reallocated pointer. This is possible if the allocator
262                  * is using a freelist like SLAB_TYPESAFE_BY_RCU where the
263                  * fence remains valid for the RCU grace period, but it
264                  * may be reallocated. When using such allocators, we are
265                  * responsible for ensuring the reference we get is to
266                  * the right fence, as below.
267                  */
268                 if (fence == rcu_access_pointer(*fencep))
269                         return rcu_pointer_handoff(fence);
270 
271                 dma_fence_put(fence);
272         } while (1);
273 }
274 
275 int dma_fence_signal(struct dma_fence *fence);
276 int dma_fence_signal_locked(struct dma_fence *fence);
277 signed long dma_fence_default_wait(struct dma_fence *fence,
278                                    bool intr, signed long timeout);
279 int dma_fence_add_callback(struct dma_fence *fence,
280                            struct dma_fence_cb *cb,
281                            dma_fence_func_t func);
282 bool dma_fence_remove_callback(struct dma_fence *fence,
283                                struct dma_fence_cb *cb);
284 void dma_fence_enable_sw_signaling(struct dma_fence *fence);
285 
286 /**
287  * dma_fence_is_signaled_locked - Return an indication if the fence
288  *                                is signaled yet.
289  * @fence:      [in]    the fence to check
290  *
291  * Returns true if the fence was already signaled, false if not. Since this
292  * function doesn't enable signaling, it is not guaranteed to ever return
293  * true if dma_fence_add_callback, dma_fence_wait or
294  * dma_fence_enable_sw_signaling haven't been called before.
295  *
296  * This function requires fence->lock to be held.
297  */
298 static inline bool
299 dma_fence_is_signaled_locked(struct dma_fence *fence)
300 {
301         if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
302                 return true;
303 
304         if (fence->ops->signaled && fence->ops->signaled(fence)) {
305                 dma_fence_signal_locked(fence);
306                 return true;
307         }
308 
309         return false;
310 }
311 
312 /**
313  * dma_fence_is_signaled - Return an indication if the fence is signaled yet.
314  * @fence:      [in]    the fence to check
315  *
316  * Returns true if the fence was already signaled, false if not. Since this
317  * function doesn't enable signaling, it is not guaranteed to ever return
318  * true if dma_fence_add_callback, dma_fence_wait or
319  * dma_fence_enable_sw_signaling haven't been called before.
320  *
321  * It's recommended for seqno fences to call dma_fence_signal when the
322  * operation is complete, it makes it possible to prevent issues from
323  * wraparound between time of issue and time of use by checking the return
324  * value of this function before calling hardware-specific wait instructions.
325  */
326 static inline bool
327 dma_fence_is_signaled(struct dma_fence *fence)
328 {
329         if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
330                 return true;
331 
332         if (fence->ops->signaled && fence->ops->signaled(fence)) {
333                 dma_fence_signal(fence);
334                 return true;
335         }
336 
337         return false;
338 }
339 
340 /**
341  * __dma_fence_is_later - return if f1 is chronologically later than f2
342  * @f1: [in]    the first fence's seqno
343  * @f2: [in]    the second fence's seqno from the same context
344  *
345  * Returns true if f1 is chronologically later than f2. Both fences must be
346  * from the same context, since a seqno is not common across contexts.
347  */
348 static inline bool __dma_fence_is_later(u32 f1, u32 f2)
349 {
350         return (int)(f1 - f2) > 0;
351 }
352 
353 /**
354  * dma_fence_is_later - return if f1 is chronologically later than f2
355  * @f1: [in]    the first fence from the same context
356  * @f2: [in]    the second fence from the same context
357  *
358  * Returns true if f1 is chronologically later than f2. Both fences must be
359  * from the same context, since a seqno is not re-used across contexts.
360  */
361 static inline bool dma_fence_is_later(struct dma_fence *f1,
362                                       struct dma_fence *f2)
363 {
364         if (WARN_ON(f1->context != f2->context))
365                 return false;
366 
367         return __dma_fence_is_later(f1->seqno, f2->seqno);
368 }
369 
370 /**
371  * dma_fence_later - return the chronologically later fence
372  * @f1: [in]    the first fence from the same context
373  * @f2: [in]    the second fence from the same context
374  *
375  * Returns NULL if both fences are signaled, otherwise the fence that would be
376  * signaled last. Both fences must be from the same context, since a seqno is
377  * not re-used across contexts.
378  */
379 static inline struct dma_fence *dma_fence_later(struct dma_fence *f1,
380                                                 struct dma_fence *f2)
381 {
382         if (WARN_ON(f1->context != f2->context))
383                 return NULL;
384 
385         /*
386          * Can't check just DMA_FENCE_FLAG_SIGNALED_BIT here, it may never
387          * have been set if enable_signaling wasn't called, and enabling that
388          * here is overkill.
389          */
390         if (dma_fence_is_later(f1, f2))
391                 return dma_fence_is_signaled(f1) ? NULL : f1;
392         else
393                 return dma_fence_is_signaled(f2) ? NULL : f2;
394 }
395 
396 /**
397  * dma_fence_get_status_locked - returns the status upon completion
398  * @fence: [in] the dma_fence to query
399  *
400  * Drivers can supply an optional error status condition before they signal
401  * the fence (to indicate whether the fence was completed due to an error
402  * rather than success). The value of the status condition is only valid
403  * if the fence has been signaled, dma_fence_get_status_locked() first checks
404  * the signal state before reporting the error status.
405  *
406  * Returns 0 if the fence has not yet been signaled, 1 if the fence has
407  * been signaled without an error condition, or a negative error code
408  * if the fence has been completed in err.
409  */
410 static inline int dma_fence_get_status_locked(struct dma_fence *fence)
411 {
412         if (dma_fence_is_signaled_locked(fence))
413                 return fence->error ?: 1;
414         else
415                 return 0;
416 }
417 
418 int dma_fence_get_status(struct dma_fence *fence);
419 
420 /**
421  * dma_fence_set_error - flag an error condition on the fence
422  * @fence: [in] the dma_fence
423  * @error: [in] the error to store
424  *
425  * Drivers can supply an optional error status condition before they signal
426  * the fence, to indicate that the fence was completed due to an error
427  * rather than success. This must be set before signaling (so that the value
428  * is visible before any waiters on the signal callback are woken). This
429  * helper exists to help catching erroneous setting of #dma_fence.error.
430  */
431 static inline void dma_fence_set_error(struct dma_fence *fence,
432                                        int error)
433 {
434         WARN_ON(test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags));
435         WARN_ON(error >= 0 || error < -MAX_ERRNO);
436 
437         fence->error = error;
438 }
439 
440 signed long dma_fence_wait_timeout(struct dma_fence *,
441                                    bool intr, signed long timeout);
442 signed long dma_fence_wait_any_timeout(struct dma_fence **fences,
443                                        uint32_t count,
444                                        bool intr, signed long timeout,
445                                        uint32_t *idx);
446 
447 /**
448  * dma_fence_wait - sleep until the fence gets signaled
449  * @fence:      [in]    the fence to wait on
450  * @intr:       [in]    if true, do an interruptible wait
451  *
452  * This function will return -ERESTARTSYS if interrupted by a signal,
453  * or 0 if the fence was signaled. Other error values may be
454  * returned on custom implementations.
455  *
456  * Performs a synchronous wait on this fence. It is assumed the caller
457  * directly or indirectly holds a reference to the fence, otherwise the
458  * fence might be freed before return, resulting in undefined behavior.
459  */
460 static inline signed long dma_fence_wait(struct dma_fence *fence, bool intr)
461 {
462         signed long ret;
463 
464         /* Since dma_fence_wait_timeout cannot timeout with
465          * MAX_SCHEDULE_TIMEOUT, only valid return values are
466          * -ERESTARTSYS and MAX_SCHEDULE_TIMEOUT.
467          */
468         ret = dma_fence_wait_timeout(fence, intr, MAX_SCHEDULE_TIMEOUT);
469 
470         return ret < 0 ? ret : 0;
471 }
472 
473 u64 dma_fence_context_alloc(unsigned num);
474 
475 #define DMA_FENCE_TRACE(f, fmt, args...) \
476         do {                                                            \
477                 struct dma_fence *__ff = (f);                           \
478                 if (IS_ENABLED(CONFIG_DMA_FENCE_TRACE))                 \
479                         pr_info("f %llu#%u: " fmt,                      \
480                                 __ff->context, __ff->seqno, ##args);    \
481         } while (0)
482 
483 #define DMA_FENCE_WARN(f, fmt, args...) \
484         do {                                                            \
485                 struct dma_fence *__ff = (f);                           \
486                 pr_warn("f %llu#%u: " fmt, __ff->context, __ff->seqno,  \
487                          ##args);                                       \
488         } while (0)
489 
490 #define DMA_FENCE_ERR(f, fmt, args...) \
491         do {                                                            \
492                 struct dma_fence *__ff = (f);                           \
493                 pr_err("f %llu#%u: " fmt, __ff->context, __ff->seqno,   \
494                         ##args);                                        \
495         } while (0)
496 
497 #endif /* __LINUX_DMA_FENCE_H */
498 

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