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 48extern struct ww_class reservation_ww_class; 49 50struct dma_resv_list; 51struct seq_file; 52 53/** 54 * enum dma_resv_usage - how the fences from a dma_resv obj are used 55 * 56 * This enum describes the different use cases for a dma_resv object and 57 * controls which fences are returned when queried. 58 * 59 * An important fact is that there is the order KERNEL<WRITE<READ<BOOKKEEP and 60 * when the dma_resv object is asked for fences for one use case the fences 61 * for the lower use case are returned as well. 62 * 63 * For example when asking for WRITE fences then the KERNEL fences are returned 64 * as well. Similar when asked for READ fences then both WRITE and KERNEL 65 * fences are returned as well. 66 * 67 * Already used fences can be promoted in the sense that a fence with 68 * DMA_RESV_USAGE_BOOKKEEP could become DMA_RESV_USAGE_READ by adding it again 69 * with this usage. But fences can never be degraded in the sense that a fence 70 * with DMA_RESV_USAGE_WRITE could become DMA_RESV_USAGE_READ. 71 */ 72enum dma_resv_usage { 73 /** 74 * @DMA_RESV_USAGE_KERNEL: For in kernel memory management only. 75 * 76 * This should only be used for things like copying or clearing memory 77 * with a DMA hardware engine for the purpose of kernel memory 78 * management. 79 * 80 * Drivers *always* must wait for those fences before accessing the 81 * resource protected by the dma_resv object. The only exception for 82 * that is when the resource is known to be locked down in place by 83 * pinning it previously. 84 */ 85 DMA_RESV_USAGE_KERNEL, 86 87 /** 88 * @DMA_RESV_USAGE_WRITE: Implicit write synchronization. 89 * 90 * This should only be used for userspace command submissions which add 91 * an implicit write dependency. 92 */ 93 DMA_RESV_USAGE_WRITE, 94 95 /** 96 * @DMA_RESV_USAGE_READ: Implicit read synchronization. 97 * 98 * This should only be used for userspace command submissions which add 99 * an implicit read dependency. 100 */ 101 DMA_RESV_USAGE_READ, 102 103 /** 104 * @DMA_RESV_USAGE_BOOKKEEP: No implicit sync. 105 * 106 * This should be used by submissions which don't want to participate in 107 * any implicit synchronization. 108 * 109 * The most common case are preemption fences, page table updates, TLB 110 * flushes as well as explicit synced user submissions. 111 * 112 * Explicit synced user user submissions can be promoted to 113 * DMA_RESV_USAGE_READ or DMA_RESV_USAGE_WRITE as needed using 114 * dma_buf_import_sync_file() when implicit synchronization should 115 * become necessary after initial adding of the fence. 116 */ 117 DMA_RESV_USAGE_BOOKKEEP 118}; 119 120/** 121 * dma_resv_usage_rw - helper for implicit sync 122 * @write: true if we create a new implicit sync write 123 * 124 * This returns the implicit synchronization usage for write or read accesses, 125 * see enum dma_resv_usage and &dma_buf.resv. 126 */ 127static inline enum dma_resv_usage dma_resv_usage_rw(bool write) 128{ 129 /* This looks confusing at first sight, but is indeed correct. 130 * 131 * The rational is that new write operations needs to wait for the 132 * existing read and write operations to finish. 133 * But a new read operation only needs to wait for the existing write 134 * operations to finish. 135 */ 136 return write ? DMA_RESV_USAGE_READ : DMA_RESV_USAGE_WRITE; 137} 138 139/** 140 * struct dma_resv - a reservation object manages fences for a buffer 141 * 142 * This is a container for dma_fence objects which needs to handle multiple use 143 * cases. 144 * 145 * One use is to synchronize cross-driver access to a struct dma_buf, either for 146 * dynamic buffer management or just to handle implicit synchronization between 147 * different users of the buffer in userspace. See &dma_buf.resv for a more 148 * in-depth discussion. 149 * 150 * The other major use is to manage access and locking within a driver in a 151 * buffer based memory manager. struct ttm_buffer_object is the canonical 152 * example here, since this is where reservation objects originated from. But 153 * use in drivers is spreading and some drivers also manage struct 154 * drm_gem_object with the same scheme. 155 */ 156struct dma_resv { 157 /** 158 * @lock: 159 * 160 * Update side lock. Don't use directly, instead use the wrapper 161 * functions like dma_resv_lock() and dma_resv_unlock(). 162 * 163 * Drivers which use the reservation object to manage memory dynamically 164 * also use this lock to protect buffer object state like placement, 165 * allocation policies or throughout command submission. 166 */ 167 struct ww_mutex lock; 168 169 /** 170 * @fences: 171 * 172 * Array of fences which where added to the dma_resv object 173 * 174 * A new fence is added by calling dma_resv_add_fence(). Since this 175 * often needs to be done past the point of no return in command 176 * submission it cannot fail, and therefore sufficient slots need to be 177 * reserved by calling dma_resv_reserve_fences(). 178 */ 179 struct dma_resv_list __rcu *fences; 180}; 181 182/** 183 * struct dma_resv_iter - current position into the dma_resv fences 184 * 185 * Don't touch this directly in the driver, use the accessor function instead. 186 * 187 * IMPORTANT 188 * 189 * When using the lockless iterators like dma_resv_iter_next_unlocked() or 190 * dma_resv_for_each_fence_unlocked() beware that the iterator can be restarted. 191 * Code which accumulates statistics or similar needs to check for this with 192 * dma_resv_iter_is_restarted(). 193 */ 194struct dma_resv_iter { 195 /** @obj: The dma_resv object we iterate over */ 196 struct dma_resv *obj; 197 198 /** @usage: Return fences with this usage or lower. */ 199 enum dma_resv_usage usage; 200 201 /** @fence: the currently handled fence */ 202 struct dma_fence *fence; 203 204 /** @fence_usage: the usage of the current fence */ 205 enum dma_resv_usage fence_usage; 206 207 /** @index: index into the shared fences */ 208 unsigned int index; 209 210 /** @fences: the shared fences; private, *MUST* not dereference */ 211 struct dma_resv_list *fences; 212 213 /** @num_fences: number of fences */ 214 unsigned int num_fences; 215 216 /** @is_restarted: true if this is the first returned fence */ 217 bool is_restarted; 218}; 219 220struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor); 221struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor); 222struct dma_fence *dma_resv_iter_first(struct dma_resv_iter *cursor); 223struct dma_fence *dma_resv_iter_next(struct dma_resv_iter *cursor); 224 225/** 226 * dma_resv_iter_begin - initialize a dma_resv_iter object 227 * @cursor: The dma_resv_iter object to initialize 228 * @obj: The dma_resv object which we want to iterate over 229 * @usage: controls which fences to include, see enum dma_resv_usage. 230 */ 231static inline void dma_resv_iter_begin(struct dma_resv_iter *cursor, 232 struct dma_resv *obj, 233 enum dma_resv_usage usage) 234{ 235 cursor->obj = obj; 236 cursor->usage = usage; 237 cursor->fence = NULL; 238} 239 240/** 241 * dma_resv_iter_end - cleanup a dma_resv_iter object 242 * @cursor: the dma_resv_iter object which should be cleaned up 243 * 244 * Make sure that the reference to the fence in the cursor is properly 245 * dropped. 246 */ 247static inline void dma_resv_iter_end(struct dma_resv_iter *cursor) 248{ 249 dma_fence_put(cursor->fence); 250} 251 252/** 253 * dma_resv_iter_usage - Return the usage of the current fence 254 * @cursor: the cursor of the current position 255 * 256 * Returns the usage of the currently processed fence. 257 */ 258static inline enum dma_resv_usage 259dma_resv_iter_usage(struct dma_resv_iter *cursor) 260{ 261 return cursor->fence_usage; 262} 263 264/** 265 * dma_resv_iter_is_restarted - test if this is the first fence after a restart 266 * @cursor: the cursor with the current position 267 * 268 * Return true if this is the first fence in an iteration after a restart. 269 */ 270static inline bool dma_resv_iter_is_restarted(struct dma_resv_iter *cursor) 271{ 272 return cursor->is_restarted; 273} 274 275/** 276 * dma_resv_for_each_fence_unlocked - unlocked fence iterator 277 * @cursor: a struct dma_resv_iter pointer 278 * @fence: the current fence 279 * 280 * Iterate over the fences in a struct dma_resv object without holding the 281 * &dma_resv.lock and using RCU instead. The cursor needs to be initialized 282 * with dma_resv_iter_begin() and cleaned up with dma_resv_iter_end(). Inside 283 * the iterator a reference to the dma_fence is held and the RCU lock dropped. 284 * 285 * Beware that the iterator can be restarted when the struct dma_resv for 286 * @cursor is modified. Code which accumulates statistics or similar needs to 287 * check for this with dma_resv_iter_is_restarted(). For this reason prefer the 288 * lock iterator dma_resv_for_each_fence() whenever possible. 289 */ 290#define dma_resv_for_each_fence_unlocked(cursor, fence) \ 291 for (fence = dma_resv_iter_first_unlocked(cursor); \ 292 fence; fence = dma_resv_iter_next_unlocked(cursor)) 293 294/** 295 * dma_resv_for_each_fence - fence iterator 296 * @cursor: a struct dma_resv_iter pointer 297 * @obj: a dma_resv object pointer 298 * @usage: controls which fences to return 299 * @fence: the current fence 300 * 301 * Iterate over the fences in a struct dma_resv object while holding the 302 * &dma_resv.lock. @all_fences controls if the shared fences are returned as 303 * well. The cursor initialisation is part of the iterator and the fence stays 304 * valid as long as the lock is held and so no extra reference to the fence is 305 * taken. 306 */ 307#define dma_resv_for_each_fence(cursor, obj, usage, fence) \ 308 for (dma_resv_iter_begin(cursor, obj, usage), \ 309 fence = dma_resv_iter_first(cursor); fence; \ 310 fence = dma_resv_iter_next(cursor)) 311 312#define dma_resv_held(obj) lockdep_is_held(&(obj)->lock.base) 313#define dma_resv_assert_held(obj) lockdep_assert_held(&(obj)->lock.base) 314 315#ifdef CONFIG_DEBUG_MUTEXES 316void dma_resv_reset_max_fences(struct dma_resv *obj); 317#else 318static inline void dma_resv_reset_max_fences(struct dma_resv *obj) {} 319#endif 320 321/** 322 * dma_resv_lock - lock the reservation object 323 * @obj: the reservation object 324 * @ctx: the locking context 325 * 326 * Locks the reservation object for exclusive access and modification. Note, 327 * that the lock is only against other writers, readers will run concurrently 328 * with a writer under RCU. The seqlock is used to notify readers if they 329 * overlap with a writer. 330 * 331 * As the reservation object may be locked by multiple parties in an 332 * undefined order, a #ww_acquire_ctx is passed to unwind if a cycle 333 * is detected. See ww_mutex_lock() and ww_acquire_init(). A reservation 334 * object may be locked by itself by passing NULL as @ctx. 335 * 336 * When a die situation is indicated by returning -EDEADLK all locks held by 337 * @ctx must be unlocked and then dma_resv_lock_slow() called on @obj. 338 * 339 * Unlocked by calling dma_resv_unlock(). 340 * 341 * See also dma_resv_lock_interruptible() for the interruptible variant. 342 */ 343static inline int dma_resv_lock(struct dma_resv *obj, 344 struct ww_acquire_ctx *ctx) 345{ 346 return ww_mutex_lock(&obj->lock, ctx); 347} 348 349/** 350 * dma_resv_lock_interruptible - lock the reservation object 351 * @obj: the reservation object 352 * @ctx: the locking context 353 * 354 * Locks the reservation object interruptible for exclusive access and 355 * modification. Note, that the lock is only against other writers, readers 356 * will run concurrently with a writer under RCU. The seqlock is used to 357 * notify readers if they overlap with a writer. 358 * 359 * As the reservation object may be locked by multiple parties in an 360 * undefined order, a #ww_acquire_ctx is passed to unwind if a cycle 361 * is detected. See ww_mutex_lock() and ww_acquire_init(). A reservation 362 * object may be locked by itself by passing NULL as @ctx. 363 * 364 * When a die situation is indicated by returning -EDEADLK all locks held by 365 * @ctx must be unlocked and then dma_resv_lock_slow_interruptible() called on 366 * @obj. 367 * 368 * Unlocked by calling dma_resv_unlock(). 369 */ 370static inline int dma_resv_lock_interruptible(struct dma_resv *obj, 371 struct ww_acquire_ctx *ctx) 372{ 373 return ww_mutex_lock_interruptible(&obj->lock, ctx); 374} 375 376/** 377 * dma_resv_lock_slow - slowpath lock the reservation object 378 * @obj: the reservation object 379 * @ctx: the locking context 380 * 381 * Acquires the reservation object after a die case. This function 382 * will sleep until the lock becomes available. See dma_resv_lock() as 383 * well. 384 * 385 * See also dma_resv_lock_slow_interruptible() for the interruptible variant. 386 */ 387static inline void dma_resv_lock_slow(struct dma_resv *obj, 388 struct ww_acquire_ctx *ctx) 389{ 390 ww_mutex_lock_slow(&obj->lock, ctx); 391} 392 393/** 394 * dma_resv_lock_slow_interruptible - slowpath lock the reservation 395 * object, interruptible 396 * @obj: the reservation object 397 * @ctx: the locking context 398 * 399 * Acquires the reservation object interruptible after a die case. This function 400 * will sleep until the lock becomes available. See 401 * dma_resv_lock_interruptible() as well. 402 */ 403static inline int dma_resv_lock_slow_interruptible(struct dma_resv *obj, 404 struct ww_acquire_ctx *ctx) 405{ 406 return ww_mutex_lock_slow_interruptible(&obj->lock, ctx); 407} 408 409/** 410 * dma_resv_trylock - trylock the reservation object 411 * @obj: the reservation object 412 * 413 * Tries to lock the reservation object for exclusive access and modification. 414 * Note, that the lock is only against other writers, readers will run 415 * concurrently with a writer under RCU. The seqlock is used to notify readers 416 * if they overlap with a writer. 417 * 418 * Also note that since no context is provided, no deadlock protection is 419 * possible, which is also not needed for a trylock. 420 * 421 * Returns true if the lock was acquired, false otherwise. 422 */ 423static inline bool __must_check dma_resv_trylock(struct dma_resv *obj) 424{ 425 return ww_mutex_trylock(&obj->lock, NULL); 426} 427 428/** 429 * dma_resv_is_locked - is the reservation object locked 430 * @obj: the reservation object 431 * 432 * Returns true if the mutex is locked, false if unlocked. 433 */ 434static inline bool dma_resv_is_locked(struct dma_resv *obj) 435{ 436 return ww_mutex_is_locked(&obj->lock); 437} 438 439/** 440 * dma_resv_locking_ctx - returns the context used to lock the object 441 * @obj: the reservation object 442 * 443 * Returns the context used to lock a reservation object or NULL if no context 444 * was used or the object is not locked at all. 445 * 446 * WARNING: This interface is pretty horrible, but TTM needs it because it 447 * doesn't pass the struct ww_acquire_ctx around in some very long callchains. 448 * Everyone else just uses it to check whether they're holding a reservation or 449 * not. 450 */ 451static inline struct ww_acquire_ctx *dma_resv_locking_ctx(struct dma_resv *obj) 452{ 453 return READ_ONCE(obj->lock.ctx); 454} 455 456/** 457 * dma_resv_unlock - unlock the reservation object 458 * @obj: the reservation object 459 * 460 * Unlocks the reservation object following exclusive access. 461 */ 462static inline void dma_resv_unlock(struct dma_resv *obj) 463{ 464 dma_resv_reset_max_fences(obj); 465 ww_mutex_unlock(&obj->lock); 466} 467 468void dma_resv_init(struct dma_resv *obj); 469void dma_resv_fini(struct dma_resv *obj); 470int dma_resv_reserve_fences(struct dma_resv *obj, unsigned int num_fences); 471void dma_resv_add_fence(struct dma_resv *obj, struct dma_fence *fence, 472 enum dma_resv_usage usage); 473void dma_resv_replace_fences(struct dma_resv *obj, uint64_t context, 474 struct dma_fence *fence, 475 enum dma_resv_usage usage); 476int dma_resv_get_fences(struct dma_resv *obj, enum dma_resv_usage usage, 477 unsigned int *num_fences, struct dma_fence ***fences); 478int dma_resv_get_singleton(struct dma_resv *obj, enum dma_resv_usage usage, 479 struct dma_fence **fence); 480int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src); 481long dma_resv_wait_timeout(struct dma_resv *obj, enum dma_resv_usage usage, 482 bool intr, unsigned long timeout); 483bool dma_resv_test_signaled(struct dma_resv *obj, enum dma_resv_usage usage); 484void dma_resv_describe(struct dma_resv *obj, struct seq_file *seq); 485 486#endif /* _LINUX_RESERVATION_H */ 487