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 enum dma_resv_usage { 67 /** 68 * @DMA_RESV_USAGE_KERNEL: For in kernel memory management only. 69 * 70 * This should only be used for things like copying or clearing memory 71 * with a DMA hardware engine for the purpose of kernel memory 72 * management. 73 * 74 * Drivers *always* must wait for those fences before accessing the 75 * resource protected by the dma_resv object. The only exception for 76 * that is when the resource is known to be locked down in place by 77 * pinning it previously. 78 */ 79 DMA_RESV_USAGE_KERNEL, 80 81 /** 82 * @DMA_RESV_USAGE_WRITE: Implicit write synchronization. 83 * 84 * This should only be used for userspace command submissions which add 85 * an implicit write dependency. 86 */ 87 DMA_RESV_USAGE_WRITE, 88 89 /** 90 * @DMA_RESV_USAGE_READ: Implicit read synchronization. 91 * 92 * This should only be used for userspace command submissions which add 93 * an implicit read dependency. 94 */ 95 DMA_RESV_USAGE_READ, 96 97 /** 98 * @DMA_RESV_USAGE_BOOKKEEP: No implicit sync. 99 * 100 * This should be used by submissions which don't want to participate in 101 * implicit synchronization. 102 * 103 * The most common case are preemption fences as well as page table 104 * updates and their TLB flushes. 105 */ 106 DMA_RESV_USAGE_BOOKKEEP 107 }; 108 109 /** 110 * dma_resv_usage_rw - helper for implicit sync 111 * @write: true if we create a new implicit sync write 112 * 113 * This returns the implicit synchronization usage for write or read accesses, 114 * see enum dma_resv_usage and &dma_buf.resv. 115 */ 116 static inline enum dma_resv_usage dma_resv_usage_rw(bool write) 117 { 118 /* This looks confusing at first sight, but is indeed correct. 119 * 120 * The rational is that new write operations needs to wait for the 121 * existing read and write operations to finish. 122 * But a new read operation only needs to wait for the existing write 123 * operations to finish. 124 */ 125 return write ? DMA_RESV_USAGE_READ : DMA_RESV_USAGE_WRITE; 126 } 127 128 /** 129 * struct dma_resv - a reservation object manages fences for a buffer 130 * 131 * This is a container for dma_fence objects which needs to handle multiple use 132 * cases. 133 * 134 * One use is to synchronize cross-driver access to a struct dma_buf, either for 135 * dynamic buffer management or just to handle implicit synchronization between 136 * different users of the buffer in userspace. See &dma_buf.resv for a more 137 * in-depth discussion. 138 * 139 * The other major use is to manage access and locking within a driver in a 140 * buffer based memory manager. struct ttm_buffer_object is the canonical 141 * example here, since this is where reservation objects originated from. But 142 * use in drivers is spreading and some drivers also manage struct 143 * drm_gem_object with the same scheme. 144 */ 145 struct dma_resv { 146 /** 147 * @lock: 148 * 149 * Update side lock. Don't use directly, instead use the wrapper 150 * functions like dma_resv_lock() and dma_resv_unlock(). 151 * 152 * Drivers which use the reservation object to manage memory dynamically 153 * also use this lock to protect buffer object state like placement, 154 * allocation policies or throughout command submission. 155 */ 156 struct ww_mutex lock; 157 158 /** 159 * @fences: 160 * 161 * Array of fences which where added to the dma_resv object 162 * 163 * A new fence is added by calling dma_resv_add_fence(). Since this 164 * often needs to be done past the point of no return in command 165 * submission it cannot fail, and therefore sufficient slots need to be 166 * reserved by calling dma_resv_reserve_fences(). 167 */ 168 struct dma_resv_list __rcu *fences; 169 }; 170 171 /** 172 * struct dma_resv_iter - current position into the dma_resv fences 173 * 174 * Don't touch this directly in the driver, use the accessor function instead. 175 * 176 * IMPORTANT 177 * 178 * When using the lockless iterators like dma_resv_iter_next_unlocked() or 179 * dma_resv_for_each_fence_unlocked() beware that the iterator can be restarted. 180 * Code which accumulates statistics or similar needs to check for this with 181 * dma_resv_iter_is_restarted(). 182 */ 183 struct dma_resv_iter { 184 /** @obj: The dma_resv object we iterate over */ 185 struct dma_resv *obj; 186 187 /** @usage: Return fences with this usage or lower. */ 188 enum dma_resv_usage usage; 189 190 /** @fence: the currently handled fence */ 191 struct dma_fence *fence; 192 193 /** @fence_usage: the usage of the current fence */ 194 enum dma_resv_usage fence_usage; 195 196 /** @index: index into the shared fences */ 197 unsigned int index; 198 199 /** @fences: the shared fences; private, *MUST* not dereference */ 200 struct dma_resv_list *fences; 201 202 /** @num_fences: number of fences */ 203 unsigned int num_fences; 204 205 /** @is_restarted: true if this is the first returned fence */ 206 bool is_restarted; 207 }; 208 209 struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor); 210 struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor); 211 struct dma_fence *dma_resv_iter_first(struct dma_resv_iter *cursor); 212 struct dma_fence *dma_resv_iter_next(struct dma_resv_iter *cursor); 213 214 /** 215 * dma_resv_iter_begin - initialize a dma_resv_iter object 216 * @cursor: The dma_resv_iter object to initialize 217 * @obj: The dma_resv object which we want to iterate over 218 * @usage: controls which fences to include, see enum dma_resv_usage. 219 */ 220 static inline void dma_resv_iter_begin(struct dma_resv_iter *cursor, 221 struct dma_resv *obj, 222 enum dma_resv_usage usage) 223 { 224 cursor->obj = obj; 225 cursor->usage = usage; 226 cursor->fence = NULL; 227 } 228 229 /** 230 * dma_resv_iter_end - cleanup a dma_resv_iter object 231 * @cursor: the dma_resv_iter object which should be cleaned up 232 * 233 * Make sure that the reference to the fence in the cursor is properly 234 * dropped. 235 */ 236 static inline void dma_resv_iter_end(struct dma_resv_iter *cursor) 237 { 238 dma_fence_put(cursor->fence); 239 } 240 241 /** 242 * dma_resv_iter_usage - Return the usage of the current fence 243 * @cursor: the cursor of the current position 244 * 245 * Returns the usage of the currently processed fence. 246 */ 247 static inline enum dma_resv_usage 248 dma_resv_iter_usage(struct dma_resv_iter *cursor) 249 { 250 return cursor->fence_usage; 251 } 252 253 /** 254 * dma_resv_iter_is_restarted - test if this is the first fence after a restart 255 * @cursor: the cursor with the current position 256 * 257 * Return true if this is the first fence in an iteration after a restart. 258 */ 259 static inline bool dma_resv_iter_is_restarted(struct dma_resv_iter *cursor) 260 { 261 return cursor->is_restarted; 262 } 263 264 /** 265 * dma_resv_for_each_fence_unlocked - unlocked fence iterator 266 * @cursor: a struct dma_resv_iter pointer 267 * @fence: the current fence 268 * 269 * Iterate over the fences in a struct dma_resv object without holding the 270 * &dma_resv.lock and using RCU instead. The cursor needs to be initialized 271 * with dma_resv_iter_begin() and cleaned up with dma_resv_iter_end(). Inside 272 * the iterator a reference to the dma_fence is held and the RCU lock dropped. 273 * 274 * Beware that the iterator can be restarted when the struct dma_resv for 275 * @cursor is modified. Code which accumulates statistics or similar needs to 276 * check for this with dma_resv_iter_is_restarted(). For this reason prefer the 277 * lock iterator dma_resv_for_each_fence() whenever possible. 278 */ 279 #define dma_resv_for_each_fence_unlocked(cursor, fence) \ 280 for (fence = dma_resv_iter_first_unlocked(cursor); \ 281 fence; fence = dma_resv_iter_next_unlocked(cursor)) 282 283 /** 284 * dma_resv_for_each_fence - fence iterator 285 * @cursor: a struct dma_resv_iter pointer 286 * @obj: a dma_resv object pointer 287 * @usage: controls which fences to return 288 * @fence: the current fence 289 * 290 * Iterate over the fences in a struct dma_resv object while holding the 291 * &dma_resv.lock. @all_fences controls if the shared fences are returned as 292 * well. The cursor initialisation is part of the iterator and the fence stays 293 * valid as long as the lock is held and so no extra reference to the fence is 294 * taken. 295 */ 296 #define dma_resv_for_each_fence(cursor, obj, usage, fence) \ 297 for (dma_resv_iter_begin(cursor, obj, usage), \ 298 fence = dma_resv_iter_first(cursor); fence; \ 299 fence = dma_resv_iter_next(cursor)) 300 301 #define dma_resv_held(obj) lockdep_is_held(&(obj)->lock.base) 302 #define dma_resv_assert_held(obj) lockdep_assert_held(&(obj)->lock.base) 303 304 #ifdef CONFIG_DEBUG_MUTEXES 305 void dma_resv_reset_max_fences(struct dma_resv *obj); 306 #else 307 static inline void dma_resv_reset_max_fences(struct dma_resv *obj) {} 308 #endif 309 310 /** 311 * dma_resv_lock - lock the reservation object 312 * @obj: the reservation object 313 * @ctx: the locking context 314 * 315 * Locks the reservation object for exclusive access and modification. Note, 316 * that the lock is only against other writers, readers will run concurrently 317 * with a writer under RCU. The seqlock is used to notify readers if they 318 * overlap with a writer. 319 * 320 * As the reservation object may be locked by multiple parties in an 321 * undefined order, a #ww_acquire_ctx is passed to unwind if a cycle 322 * is detected. See ww_mutex_lock() and ww_acquire_init(). A reservation 323 * object may be locked by itself by passing NULL as @ctx. 324 * 325 * When a die situation is indicated by returning -EDEADLK all locks held by 326 * @ctx must be unlocked and then dma_resv_lock_slow() called on @obj. 327 * 328 * Unlocked by calling dma_resv_unlock(). 329 * 330 * See also dma_resv_lock_interruptible() for the interruptible variant. 331 */ 332 static inline int dma_resv_lock(struct dma_resv *obj, 333 struct ww_acquire_ctx *ctx) 334 { 335 return ww_mutex_lock(&obj->lock, ctx); 336 } 337 338 /** 339 * dma_resv_lock_interruptible - lock the reservation object 340 * @obj: the reservation object 341 * @ctx: the locking context 342 * 343 * Locks the reservation object interruptible for exclusive access and 344 * modification. Note, that the lock is only against other writers, readers 345 * will run concurrently with a writer under RCU. The seqlock is used to 346 * notify readers if they overlap with a writer. 347 * 348 * As the reservation object may be locked by multiple parties in an 349 * undefined order, a #ww_acquire_ctx is passed to unwind if a cycle 350 * is detected. See ww_mutex_lock() and ww_acquire_init(). A reservation 351 * object may be locked by itself by passing NULL as @ctx. 352 * 353 * When a die situation is indicated by returning -EDEADLK all locks held by 354 * @ctx must be unlocked and then dma_resv_lock_slow_interruptible() called on 355 * @obj. 356 * 357 * Unlocked by calling dma_resv_unlock(). 358 */ 359 static inline int dma_resv_lock_interruptible(struct dma_resv *obj, 360 struct ww_acquire_ctx *ctx) 361 { 362 return ww_mutex_lock_interruptible(&obj->lock, ctx); 363 } 364 365 /** 366 * dma_resv_lock_slow - slowpath lock the reservation object 367 * @obj: the reservation object 368 * @ctx: the locking context 369 * 370 * Acquires the reservation object after a die case. This function 371 * will sleep until the lock becomes available. See dma_resv_lock() as 372 * well. 373 * 374 * See also dma_resv_lock_slow_interruptible() for the interruptible variant. 375 */ 376 static inline void dma_resv_lock_slow(struct dma_resv *obj, 377 struct ww_acquire_ctx *ctx) 378 { 379 ww_mutex_lock_slow(&obj->lock, ctx); 380 } 381 382 /** 383 * dma_resv_lock_slow_interruptible - slowpath lock the reservation 384 * object, interruptible 385 * @obj: the reservation object 386 * @ctx: the locking context 387 * 388 * Acquires the reservation object interruptible after a die case. This function 389 * will sleep until the lock becomes available. See 390 * dma_resv_lock_interruptible() as well. 391 */ 392 static inline int dma_resv_lock_slow_interruptible(struct dma_resv *obj, 393 struct ww_acquire_ctx *ctx) 394 { 395 return ww_mutex_lock_slow_interruptible(&obj->lock, ctx); 396 } 397 398 /** 399 * dma_resv_trylock - trylock the reservation object 400 * @obj: the reservation object 401 * 402 * Tries to lock the reservation object for exclusive access and modification. 403 * Note, that the lock is only against other writers, readers will run 404 * concurrently with a writer under RCU. The seqlock is used to notify readers 405 * if they overlap with a writer. 406 * 407 * Also note that since no context is provided, no deadlock protection is 408 * possible, which is also not needed for a trylock. 409 * 410 * Returns true if the lock was acquired, false otherwise. 411 */ 412 static inline bool __must_check dma_resv_trylock(struct dma_resv *obj) 413 { 414 return ww_mutex_trylock(&obj->lock, NULL); 415 } 416 417 /** 418 * dma_resv_is_locked - is the reservation object locked 419 * @obj: the reservation object 420 * 421 * Returns true if the mutex is locked, false if unlocked. 422 */ 423 static inline bool dma_resv_is_locked(struct dma_resv *obj) 424 { 425 return ww_mutex_is_locked(&obj->lock); 426 } 427 428 /** 429 * dma_resv_locking_ctx - returns the context used to lock the object 430 * @obj: the reservation object 431 * 432 * Returns the context used to lock a reservation object or NULL if no context 433 * was used or the object is not locked at all. 434 * 435 * WARNING: This interface is pretty horrible, but TTM needs it because it 436 * doesn't pass the struct ww_acquire_ctx around in some very long callchains. 437 * Everyone else just uses it to check whether they're holding a reservation or 438 * not. 439 */ 440 static inline struct ww_acquire_ctx *dma_resv_locking_ctx(struct dma_resv *obj) 441 { 442 return READ_ONCE(obj->lock.ctx); 443 } 444 445 /** 446 * dma_resv_unlock - unlock the reservation object 447 * @obj: the reservation object 448 * 449 * Unlocks the reservation object following exclusive access. 450 */ 451 static inline void dma_resv_unlock(struct dma_resv *obj) 452 { 453 dma_resv_reset_max_fences(obj); 454 ww_mutex_unlock(&obj->lock); 455 } 456 457 void dma_resv_init(struct dma_resv *obj); 458 void dma_resv_fini(struct dma_resv *obj); 459 int dma_resv_reserve_fences(struct dma_resv *obj, unsigned int num_fences); 460 void dma_resv_add_fence(struct dma_resv *obj, struct dma_fence *fence, 461 enum dma_resv_usage usage); 462 void dma_resv_replace_fences(struct dma_resv *obj, uint64_t context, 463 struct dma_fence *fence, 464 enum dma_resv_usage usage); 465 int dma_resv_get_fences(struct dma_resv *obj, enum dma_resv_usage usage, 466 unsigned int *num_fences, struct dma_fence ***fences); 467 int dma_resv_get_singleton(struct dma_resv *obj, enum dma_resv_usage usage, 468 struct dma_fence **fence); 469 int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src); 470 long dma_resv_wait_timeout(struct dma_resv *obj, enum dma_resv_usage usage, 471 bool intr, unsigned long timeout); 472 bool dma_resv_test_signaled(struct dma_resv *obj, enum dma_resv_usage usage); 473 void dma_resv_describe(struct dma_resv *obj, struct seq_file *seq); 474 475 #endif /* _LINUX_RESERVATION_H */ 476