1 // SPDX-License-Identifier: GPL-2.0 OR MIT 2 3 #include <drm/drm_exec.h> 4 #include <drm/drm_gem.h> 5 #include <linux/dma-resv.h> 6 7 /** 8 * DOC: Overview 9 * 10 * This component mainly abstracts the retry loop necessary for locking 11 * multiple GEM objects while preparing hardware operations (e.g. command 12 * submissions, page table updates etc..). 13 * 14 * If a contention is detected while locking a GEM object the cleanup procedure 15 * unlocks all previously locked GEM objects and locks the contended one first 16 * before locking any further objects. 17 * 18 * After an object is locked fences slots can optionally be reserved on the 19 * dma_resv object inside the GEM object. 20 * 21 * A typical usage pattern should look like this:: 22 * 23 * struct drm_gem_object *obj; 24 * struct drm_exec exec; 25 * unsigned long index; 26 * int ret; 27 * 28 * drm_exec_init(&exec, DRM_EXEC_INTERRUPTIBLE_WAIT); 29 * drm_exec_until_all_locked(&exec) { 30 * ret = drm_exec_prepare_obj(&exec, boA, 1); 31 * drm_exec_retry_on_contention(&exec); 32 * if (ret) 33 * goto error; 34 * 35 * ret = drm_exec_prepare_obj(&exec, boB, 1); 36 * drm_exec_retry_on_contention(&exec); 37 * if (ret) 38 * goto error; 39 * } 40 * 41 * drm_exec_for_each_locked_object(&exec, index, obj) { 42 * dma_resv_add_fence(obj->resv, fence, DMA_RESV_USAGE_READ); 43 * ... 44 * } 45 * drm_exec_fini(&exec); 46 * 47 * See struct dma_exec for more details. 48 */ 49 50 /* Dummy value used to initially enter the retry loop */ 51 #define DRM_EXEC_DUMMY ((void *)~0) 52 53 /* Unlock all objects and drop references */ 54 static void drm_exec_unlock_all(struct drm_exec *exec) 55 { 56 struct drm_gem_object *obj; 57 unsigned long index; 58 59 drm_exec_for_each_locked_object_reverse(exec, index, obj) { 60 dma_resv_unlock(obj->resv); 61 drm_gem_object_put(obj); 62 } 63 64 drm_gem_object_put(exec->prelocked); 65 exec->prelocked = NULL; 66 } 67 68 /** 69 * drm_exec_init - initialize a drm_exec object 70 * @exec: the drm_exec object to initialize 71 * @flags: controls locking behavior, see DRM_EXEC_* defines 72 * @nr: the initial # of objects 73 * 74 * Initialize the object and make sure that we can track locked objects. 75 * 76 * If nr is non-zero then it is used as the initial objects table size. 77 * In either case, the table will grow (be re-allocated) on demand. 78 */ 79 void drm_exec_init(struct drm_exec *exec, u32 flags, unsigned nr) 80 { 81 if (!nr) 82 nr = PAGE_SIZE / sizeof(void *); 83 84 exec->flags = flags; 85 exec->objects = kvmalloc_array(nr, sizeof(void *), GFP_KERNEL); 86 87 /* If allocation here fails, just delay that till the first use */ 88 exec->max_objects = exec->objects ? nr : 0; 89 exec->num_objects = 0; 90 exec->contended = DRM_EXEC_DUMMY; 91 exec->prelocked = NULL; 92 } 93 EXPORT_SYMBOL(drm_exec_init); 94 95 /** 96 * drm_exec_fini - finalize a drm_exec object 97 * @exec: the drm_exec object to finalize 98 * 99 * Unlock all locked objects, drop the references to objects and free all memory 100 * used for tracking the state. 101 */ 102 void drm_exec_fini(struct drm_exec *exec) 103 { 104 drm_exec_unlock_all(exec); 105 kvfree(exec->objects); 106 if (exec->contended != DRM_EXEC_DUMMY) { 107 drm_gem_object_put(exec->contended); 108 ww_acquire_fini(&exec->ticket); 109 } 110 } 111 EXPORT_SYMBOL(drm_exec_fini); 112 113 /** 114 * drm_exec_cleanup - cleanup when contention is detected 115 * @exec: the drm_exec object to cleanup 116 * 117 * Cleanup the current state and return true if we should stay inside the retry 118 * loop, false if there wasn't any contention detected and we can keep the 119 * objects locked. 120 */ 121 bool drm_exec_cleanup(struct drm_exec *exec) 122 { 123 if (likely(!exec->contended)) { 124 ww_acquire_done(&exec->ticket); 125 return false; 126 } 127 128 if (likely(exec->contended == DRM_EXEC_DUMMY)) { 129 exec->contended = NULL; 130 ww_acquire_init(&exec->ticket, &reservation_ww_class); 131 return true; 132 } 133 134 drm_exec_unlock_all(exec); 135 exec->num_objects = 0; 136 return true; 137 } 138 EXPORT_SYMBOL(drm_exec_cleanup); 139 140 /* Track the locked object in the array */ 141 static int drm_exec_obj_locked(struct drm_exec *exec, 142 struct drm_gem_object *obj) 143 { 144 if (unlikely(exec->num_objects == exec->max_objects)) { 145 size_t size = exec->max_objects * sizeof(void *); 146 void *tmp; 147 148 tmp = kvrealloc(exec->objects, size, size + PAGE_SIZE, 149 GFP_KERNEL); 150 if (!tmp) 151 return -ENOMEM; 152 153 exec->objects = tmp; 154 exec->max_objects += PAGE_SIZE / sizeof(void *); 155 } 156 drm_gem_object_get(obj); 157 exec->objects[exec->num_objects++] = obj; 158 159 return 0; 160 } 161 162 /* Make sure the contended object is locked first */ 163 static int drm_exec_lock_contended(struct drm_exec *exec) 164 { 165 struct drm_gem_object *obj = exec->contended; 166 int ret; 167 168 if (likely(!obj)) 169 return 0; 170 171 /* Always cleanup the contention so that error handling can kick in */ 172 exec->contended = NULL; 173 if (exec->flags & DRM_EXEC_INTERRUPTIBLE_WAIT) { 174 ret = dma_resv_lock_slow_interruptible(obj->resv, 175 &exec->ticket); 176 if (unlikely(ret)) 177 goto error_dropref; 178 } else { 179 dma_resv_lock_slow(obj->resv, &exec->ticket); 180 } 181 182 ret = drm_exec_obj_locked(exec, obj); 183 if (unlikely(ret)) 184 goto error_unlock; 185 186 exec->prelocked = obj; 187 return 0; 188 189 error_unlock: 190 dma_resv_unlock(obj->resv); 191 192 error_dropref: 193 drm_gem_object_put(obj); 194 return ret; 195 } 196 197 /** 198 * drm_exec_lock_obj - lock a GEM object for use 199 * @exec: the drm_exec object with the state 200 * @obj: the GEM object to lock 201 * 202 * Lock a GEM object for use and grab a reference to it. 203 * 204 * Returns: -EDEADLK if a contention is detected, -EALREADY when object is 205 * already locked (can be suppressed by setting the DRM_EXEC_IGNORE_DUPLICATES 206 * flag), -ENOMEM when memory allocation failed and zero for success. 207 */ 208 int drm_exec_lock_obj(struct drm_exec *exec, struct drm_gem_object *obj) 209 { 210 int ret; 211 212 ret = drm_exec_lock_contended(exec); 213 if (unlikely(ret)) 214 return ret; 215 216 if (exec->prelocked == obj) { 217 drm_gem_object_put(exec->prelocked); 218 exec->prelocked = NULL; 219 return 0; 220 } 221 222 if (exec->flags & DRM_EXEC_INTERRUPTIBLE_WAIT) 223 ret = dma_resv_lock_interruptible(obj->resv, &exec->ticket); 224 else 225 ret = dma_resv_lock(obj->resv, &exec->ticket); 226 227 if (unlikely(ret == -EDEADLK)) { 228 drm_gem_object_get(obj); 229 exec->contended = obj; 230 return -EDEADLK; 231 } 232 233 if (unlikely(ret == -EALREADY) && 234 exec->flags & DRM_EXEC_IGNORE_DUPLICATES) 235 return 0; 236 237 if (unlikely(ret)) 238 return ret; 239 240 ret = drm_exec_obj_locked(exec, obj); 241 if (ret) 242 goto error_unlock; 243 244 return 0; 245 246 error_unlock: 247 dma_resv_unlock(obj->resv); 248 return ret; 249 } 250 EXPORT_SYMBOL(drm_exec_lock_obj); 251 252 /** 253 * drm_exec_unlock_obj - unlock a GEM object in this exec context 254 * @exec: the drm_exec object with the state 255 * @obj: the GEM object to unlock 256 * 257 * Unlock the GEM object and remove it from the collection of locked objects. 258 * Should only be used to unlock the most recently locked objects. It's not time 259 * efficient to unlock objects locked long ago. 260 */ 261 void drm_exec_unlock_obj(struct drm_exec *exec, struct drm_gem_object *obj) 262 { 263 unsigned int i; 264 265 for (i = exec->num_objects; i--;) { 266 if (exec->objects[i] == obj) { 267 dma_resv_unlock(obj->resv); 268 for (++i; i < exec->num_objects; ++i) 269 exec->objects[i - 1] = exec->objects[i]; 270 --exec->num_objects; 271 drm_gem_object_put(obj); 272 return; 273 } 274 275 } 276 } 277 EXPORT_SYMBOL(drm_exec_unlock_obj); 278 279 /** 280 * drm_exec_prepare_obj - prepare a GEM object for use 281 * @exec: the drm_exec object with the state 282 * @obj: the GEM object to prepare 283 * @num_fences: how many fences to reserve 284 * 285 * Prepare a GEM object for use by locking it and reserving fence slots. 286 * 287 * Returns: -EDEADLK if a contention is detected, -EALREADY when object is 288 * already locked, -ENOMEM when memory allocation failed and zero for success. 289 */ 290 int drm_exec_prepare_obj(struct drm_exec *exec, struct drm_gem_object *obj, 291 unsigned int num_fences) 292 { 293 int ret; 294 295 ret = drm_exec_lock_obj(exec, obj); 296 if (ret) 297 return ret; 298 299 ret = dma_resv_reserve_fences(obj->resv, num_fences); 300 if (ret) { 301 drm_exec_unlock_obj(exec, obj); 302 return ret; 303 } 304 305 return 0; 306 } 307 EXPORT_SYMBOL(drm_exec_prepare_obj); 308 309 /** 310 * drm_exec_prepare_array - helper to prepare an array of objects 311 * @exec: the drm_exec object with the state 312 * @objects: array of GEM object to prepare 313 * @num_objects: number of GEM objects in the array 314 * @num_fences: number of fences to reserve on each GEM object 315 * 316 * Prepares all GEM objects in an array, aborts on first error. 317 * Reserves @num_fences on each GEM object after locking it. 318 * 319 * Returns: -EDEADLOCK on contention, -EALREADY when object is already locked, 320 * -ENOMEM when memory allocation failed and zero for success. 321 */ 322 int drm_exec_prepare_array(struct drm_exec *exec, 323 struct drm_gem_object **objects, 324 unsigned int num_objects, 325 unsigned int num_fences) 326 { 327 int ret; 328 329 for (unsigned int i = 0; i < num_objects; ++i) { 330 ret = drm_exec_prepare_obj(exec, objects[i], num_fences); 331 if (unlikely(ret)) 332 return ret; 333 } 334 335 return 0; 336 } 337 EXPORT_SYMBOL(drm_exec_prepare_array); 338 339 MODULE_DESCRIPTION("DRM execution context"); 340 MODULE_LICENSE("Dual MIT/GPL"); 341