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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_FENCE_H | |
22 | #define __LINUX_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> | |
3c3b177a | 31 | #include <linux/rcupdate.h> |
e941759c ML |
32 | |
33 | struct fence; | |
34 | struct fence_ops; | |
35 | struct fence_cb; | |
36 | ||
37 | /** | |
38 | * struct fence - software synchronization primitive | |
39 | * @refcount: refcount for this fence | |
40 | * @ops: fence_ops associated with this fence | |
3c3b177a | 41 | * @rcu: used for releasing fence with kfree_rcu |
e941759c ML |
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 | * 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 FENCE_FLAG_* defined below | |
49 | * @timestamp: Timestamp when the fence was signaled. | |
50 | * @status: Optional, only valid if < 0, must be set before calling | |
51 | * 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 | * FENCE_FLAG_SIGNALED_BIT - fence is already signaled | |
58 | * FENCE_FLAG_ENABLE_SIGNAL_BIT - enable_signaling might have been called* | |
59 | * FENCE_FLAG_USER_BITS - start of the unused bits, can be used by the | |
60 | * implementer of the fence for its own purposes. Can be used in different | |
61 | * ways by different fence implementers, so do not rely on this. | |
62 | * | |
63 | * *) Since atomic bitops are used, this is not guaranteed to be the case. | |
64 | * Particularly, if the bit was set, but fence_signal was called right | |
65 | * before this bit was set, it would have been able to set the | |
66 | * FENCE_FLAG_SIGNALED_BIT, before enable_signaling was called. | |
67 | * Adding a check for FENCE_FLAG_SIGNALED_BIT after setting | |
68 | * FENCE_FLAG_ENABLE_SIGNAL_BIT closes this race, and makes sure that | |
69 | * after fence_signal was called, any enable_signaling call will have either | |
70 | * been completed, or never called at all. | |
71 | */ | |
72 | struct fence { | |
73 | struct kref refcount; | |
74 | const struct fence_ops *ops; | |
3c3b177a | 75 | struct rcu_head rcu; |
e941759c ML |
76 | struct list_head cb_list; |
77 | spinlock_t *lock; | |
78 | unsigned context, seqno; | |
79 | unsigned long flags; | |
80 | ktime_t timestamp; | |
81 | int status; | |
82 | }; | |
83 | ||
84 | enum fence_flag_bits { | |
85 | FENCE_FLAG_SIGNALED_BIT, | |
86 | FENCE_FLAG_ENABLE_SIGNAL_BIT, | |
87 | FENCE_FLAG_USER_BITS, /* must always be last member */ | |
88 | }; | |
89 | ||
90 | typedef void (*fence_func_t)(struct fence *fence, struct fence_cb *cb); | |
91 | ||
92 | /** | |
93 | * struct fence_cb - callback for fence_add_callback | |
94 | * @node: used by fence_add_callback to append this struct to fence::cb_list | |
95 | * @func: fence_func_t to call | |
96 | * | |
97 | * This struct will be initialized by fence_add_callback, additional | |
98 | * data can be passed along by embedding fence_cb in another struct. | |
99 | */ | |
100 | struct fence_cb { | |
101 | struct list_head node; | |
102 | fence_func_t func; | |
103 | }; | |
104 | ||
105 | /** | |
106 | * struct fence_ops - operations implemented for fence | |
107 | * @get_driver_name: returns the driver name. | |
108 | * @get_timeline_name: return the name of the context this fence belongs to. | |
109 | * @enable_signaling: enable software signaling of fence. | |
110 | * @signaled: [optional] peek whether the fence is signaled, can be null. | |
111 | * @wait: custom wait implementation, or fence_default_wait. | |
112 | * @release: [optional] called on destruction of fence, can be null | |
113 | * @fill_driver_data: [optional] callback to fill in free-form debug info | |
114 | * Returns amount of bytes filled, or -errno. | |
115 | * @fence_value_str: [optional] fills in the value of the fence as a string | |
116 | * @timeline_value_str: [optional] fills in the current value of the timeline | |
117 | * as a string | |
118 | * | |
119 | * Notes on enable_signaling: | |
120 | * For fence implementations that have the capability for hw->hw | |
121 | * signaling, they can implement this op to enable the necessary | |
122 | * irqs, or insert commands into cmdstream, etc. This is called | |
123 | * in the first wait() or add_callback() path to let the fence | |
124 | * implementation know that there is another driver waiting on | |
125 | * the signal (ie. hw->sw case). | |
126 | * | |
127 | * This function can be called called from atomic context, but not | |
128 | * from irq context, so normal spinlocks can be used. | |
129 | * | |
130 | * A return value of false indicates the fence already passed, | |
f353d71f MI |
131 | * or some failure occurred that made it impossible to enable |
132 | * signaling. True indicates successful enabling. | |
e941759c ML |
133 | * |
134 | * fence->status may be set in enable_signaling, but only when false is | |
135 | * returned. | |
136 | * | |
137 | * Calling fence_signal before enable_signaling is called allows | |
138 | * for a tiny race window in which enable_signaling is called during, | |
139 | * before, or after fence_signal. To fight this, it is recommended | |
140 | * that before enable_signaling returns true an extra reference is | |
141 | * taken on the fence, to be released when the fence is signaled. | |
142 | * This will mean fence_signal will still be called twice, but | |
143 | * the second time will be a noop since it was already signaled. | |
144 | * | |
145 | * Notes on signaled: | |
146 | * May set fence->status if returning true. | |
147 | * | |
148 | * Notes on wait: | |
149 | * Must not be NULL, set to fence_default_wait for default implementation. | |
150 | * the fence_default_wait implementation should work for any fence, as long | |
151 | * as enable_signaling works correctly. | |
152 | * | |
153 | * Must return -ERESTARTSYS if the wait is intr = true and the wait was | |
154 | * interrupted, and remaining jiffies if fence has signaled, or 0 if wait | |
155 | * timed out. Can also return other error values on custom implementations, | |
156 | * which should be treated as if the fence is signaled. For example a hardware | |
157 | * lockup could be reported like that. | |
158 | * | |
159 | * Notes on release: | |
160 | * Can be NULL, this function allows additional commands to run on | |
161 | * destruction of the fence. Can be called from irq context. | |
162 | * If pointer is set to NULL, kfree will get called instead. | |
163 | */ | |
164 | ||
165 | struct fence_ops { | |
166 | const char * (*get_driver_name)(struct fence *fence); | |
167 | const char * (*get_timeline_name)(struct fence *fence); | |
168 | bool (*enable_signaling)(struct fence *fence); | |
169 | bool (*signaled)(struct fence *fence); | |
170 | signed long (*wait)(struct fence *fence, bool intr, signed long timeout); | |
171 | void (*release)(struct fence *fence); | |
172 | ||
173 | int (*fill_driver_data)(struct fence *fence, void *data, int size); | |
174 | void (*fence_value_str)(struct fence *fence, char *str, int size); | |
175 | void (*timeline_value_str)(struct fence *fence, char *str, int size); | |
176 | }; | |
177 | ||
178 | void fence_init(struct fence *fence, const struct fence_ops *ops, | |
179 | spinlock_t *lock, unsigned context, unsigned seqno); | |
180 | ||
181 | void fence_release(struct kref *kref); | |
182 | void fence_free(struct fence *fence); | |
183 | ||
184 | /** | |
185 | * fence_get - increases refcount of the fence | |
186 | * @fence: [in] fence to increase refcount of | |
187 | * | |
188 | * Returns the same fence, with refcount increased by 1. | |
189 | */ | |
190 | static inline struct fence *fence_get(struct fence *fence) | |
191 | { | |
192 | if (fence) | |
193 | kref_get(&fence->refcount); | |
194 | return fence; | |
195 | } | |
196 | ||
3c3b177a ML |
197 | /** |
198 | * fence_get_rcu - get a fence from a reservation_object_list with rcu read lock | |
199 | * @fence: [in] fence to increase refcount of | |
200 | * | |
201 | * Function returns NULL if no refcount could be obtained, or the fence. | |
202 | */ | |
203 | static inline struct fence *fence_get_rcu(struct fence *fence) | |
204 | { | |
205 | if (kref_get_unless_zero(&fence->refcount)) | |
206 | return fence; | |
207 | else | |
208 | return NULL; | |
209 | } | |
210 | ||
e941759c ML |
211 | /** |
212 | * fence_put - decreases refcount of the fence | |
213 | * @fence: [in] fence to reduce refcount of | |
214 | */ | |
215 | static inline void fence_put(struct fence *fence) | |
216 | { | |
217 | if (fence) | |
218 | kref_put(&fence->refcount, fence_release); | |
219 | } | |
220 | ||
221 | int fence_signal(struct fence *fence); | |
222 | int fence_signal_locked(struct fence *fence); | |
223 | signed long fence_default_wait(struct fence *fence, bool intr, signed long timeout); | |
224 | int fence_add_callback(struct fence *fence, struct fence_cb *cb, | |
225 | fence_func_t func); | |
226 | bool fence_remove_callback(struct fence *fence, struct fence_cb *cb); | |
227 | void fence_enable_sw_signaling(struct fence *fence); | |
228 | ||
229 | /** | |
230 | * fence_is_signaled_locked - Return an indication if the fence is signaled yet. | |
231 | * @fence: [in] the fence to check | |
232 | * | |
233 | * Returns true if the fence was already signaled, false if not. Since this | |
234 | * function doesn't enable signaling, it is not guaranteed to ever return | |
235 | * true if fence_add_callback, fence_wait or fence_enable_sw_signaling | |
236 | * haven't been called before. | |
237 | * | |
238 | * This function requires fence->lock to be held. | |
239 | */ | |
240 | static inline bool | |
241 | fence_is_signaled_locked(struct fence *fence) | |
242 | { | |
243 | if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags)) | |
244 | return true; | |
245 | ||
246 | if (fence->ops->signaled && fence->ops->signaled(fence)) { | |
247 | fence_signal_locked(fence); | |
248 | return true; | |
249 | } | |
250 | ||
251 | return false; | |
252 | } | |
253 | ||
254 | /** | |
255 | * fence_is_signaled - Return an indication if the fence is signaled yet. | |
256 | * @fence: [in] the fence to check | |
257 | * | |
258 | * Returns true if the fence was already signaled, false if not. Since this | |
259 | * function doesn't enable signaling, it is not guaranteed to ever return | |
260 | * true if fence_add_callback, fence_wait or fence_enable_sw_signaling | |
261 | * haven't been called before. | |
262 | * | |
263 | * It's recommended for seqno fences to call fence_signal when the | |
264 | * operation is complete, it makes it possible to prevent issues from | |
265 | * wraparound between time of issue and time of use by checking the return | |
266 | * value of this function before calling hardware-specific wait instructions. | |
267 | */ | |
268 | static inline bool | |
269 | fence_is_signaled(struct fence *fence) | |
270 | { | |
271 | if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags)) | |
272 | return true; | |
273 | ||
274 | if (fence->ops->signaled && fence->ops->signaled(fence)) { | |
275 | fence_signal(fence); | |
276 | return true; | |
277 | } | |
278 | ||
279 | return false; | |
280 | } | |
281 | ||
282 | /** | |
283 | * fence_later - return the chronologically later fence | |
284 | * @f1: [in] the first fence from the same context | |
285 | * @f2: [in] the second fence from the same context | |
286 | * | |
287 | * Returns NULL if both fences are signaled, otherwise the fence that would be | |
288 | * signaled last. Both fences must be from the same context, since a seqno is | |
289 | * not re-used across contexts. | |
290 | */ | |
291 | static inline struct fence *fence_later(struct fence *f1, struct fence *f2) | |
292 | { | |
293 | if (WARN_ON(f1->context != f2->context)) | |
294 | return NULL; | |
295 | ||
296 | /* | |
297 | * can't check just FENCE_FLAG_SIGNALED_BIT here, it may never have been | |
298 | * set if enable_signaling wasn't called, and enabling that here is | |
299 | * overkill. | |
300 | */ | |
301 | if (f2->seqno - f1->seqno <= INT_MAX) | |
302 | return fence_is_signaled(f2) ? NULL : f2; | |
303 | else | |
304 | return fence_is_signaled(f1) ? NULL : f1; | |
305 | } | |
306 | ||
307 | signed long fence_wait_timeout(struct fence *, bool intr, signed long timeout); | |
308 | ||
309 | ||
310 | /** | |
311 | * fence_wait - sleep until the fence gets signaled | |
312 | * @fence: [in] the fence to wait on | |
313 | * @intr: [in] if true, do an interruptible wait | |
314 | * | |
315 | * This function will return -ERESTARTSYS if interrupted by a signal, | |
316 | * or 0 if the fence was signaled. Other error values may be | |
317 | * returned on custom implementations. | |
318 | * | |
319 | * Performs a synchronous wait on this fence. It is assumed the caller | |
320 | * directly or indirectly holds a reference to the fence, otherwise the | |
321 | * fence might be freed before return, resulting in undefined behavior. | |
322 | */ | |
323 | static inline signed long fence_wait(struct fence *fence, bool intr) | |
324 | { | |
325 | signed long ret; | |
326 | ||
327 | /* Since fence_wait_timeout cannot timeout with | |
328 | * MAX_SCHEDULE_TIMEOUT, only valid return values are | |
329 | * -ERESTARTSYS and MAX_SCHEDULE_TIMEOUT. | |
330 | */ | |
331 | ret = fence_wait_timeout(fence, intr, MAX_SCHEDULE_TIMEOUT); | |
332 | ||
333 | return ret < 0 ? ret : 0; | |
334 | } | |
335 | ||
336 | unsigned fence_context_alloc(unsigned num); | |
337 | ||
338 | #define FENCE_TRACE(f, fmt, args...) \ | |
339 | do { \ | |
340 | struct fence *__ff = (f); \ | |
341 | if (config_enabled(CONFIG_FENCE_TRACE)) \ | |
342 | pr_info("f %u#%u: " fmt, \ | |
343 | __ff->context, __ff->seqno, ##args); \ | |
344 | } while (0) | |
345 | ||
346 | #define FENCE_WARN(f, fmt, args...) \ | |
347 | do { \ | |
348 | struct fence *__ff = (f); \ | |
349 | pr_warn("f %u#%u: " fmt, __ff->context, __ff->seqno, \ | |
350 | ##args); \ | |
351 | } while (0) | |
352 | ||
353 | #define FENCE_ERR(f, fmt, args...) \ | |
354 | do { \ | |
355 | struct fence *__ff = (f); \ | |
356 | pr_err("f %u#%u: " fmt, __ff->context, __ff->seqno, \ | |
357 | ##args); \ | |
358 | } while (0) | |
359 | ||
360 | #endif /* __LINUX_FENCE_H */ |