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(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(&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(&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(&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(&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(&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(&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(&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