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| 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(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 | + * |
| 73 | + * Initialize the object and make sure that we can track locked objects. |
| 74 | + */ |
| 75 | +void drm_exec_init(struct drm_exec *exec, uint32_t flags) |
| 76 | +{ |
| 77 | + exec->flags = flags; |
| 78 | + exec->objects = kmalloc(PAGE_SIZE, GFP_KERNEL); |
| 79 | + |
| 80 | + /* If allocation here fails, just delay that till the first use */ |
| 81 | + exec->max_objects = exec->objects ? PAGE_SIZE / sizeof(void *) : 0; |
| 82 | + exec->num_objects = 0; |
| 83 | + exec->contended = DRM_EXEC_DUMMY; |
| 84 | + exec->prelocked = NULL; |
| 85 | +} |
| 86 | +EXPORT_SYMBOL(drm_exec_init); |
| 87 | + |
| 88 | +/** |
| 89 | + * drm_exec_fini - finalize a drm_exec object |
| 90 | + * @exec: the drm_exec object to finalize |
| 91 | + * |
| 92 | + * Unlock all locked objects, drop the references to objects and free all memory |
| 93 | + * used for tracking the state. |
| 94 | + */ |
| 95 | +void drm_exec_fini(struct drm_exec *exec) |
| 96 | +{ |
| 97 | + drm_exec_unlock_all(exec); |
| 98 | + kvfree(exec->objects); |
| 99 | + if (exec->contended != DRM_EXEC_DUMMY) { |
| 100 | + drm_gem_object_put(exec->contended); |
| 101 | + ww_acquire_fini(&exec->ticket); |
| 102 | + } |
| 103 | +} |
| 104 | +EXPORT_SYMBOL(drm_exec_fini); |
| 105 | + |
| 106 | +/** |
| 107 | + * drm_exec_cleanup - cleanup when contention is detected |
| 108 | + * @exec: the drm_exec object to cleanup |
| 109 | + * |
| 110 | + * Cleanup the current state and return true if we should stay inside the retry |
| 111 | + * loop, false if there wasn't any contention detected and we can keep the |
| 112 | + * objects locked. |
| 113 | + */ |
| 114 | +bool drm_exec_cleanup(struct drm_exec *exec) |
| 115 | +{ |
| 116 | + if (likely(!exec->contended)) { |
| 117 | + ww_acquire_done(&exec->ticket); |
| 118 | + return false; |
| 119 | + } |
| 120 | + |
| 121 | + if (likely(exec->contended == DRM_EXEC_DUMMY)) { |
| 122 | + exec->contended = NULL; |
| 123 | + ww_acquire_init(&exec->ticket, &reservation_ww_class); |
| 124 | + return true; |
| 125 | + } |
| 126 | + |
| 127 | + drm_exec_unlock_all(exec); |
| 128 | + exec->num_objects = 0; |
| 129 | + return true; |
| 130 | +} |
| 131 | +EXPORT_SYMBOL(drm_exec_cleanup); |
| 132 | + |
| 133 | +/* Track the locked object in the array */ |
| 134 | +static int drm_exec_obj_locked(struct drm_exec *exec, |
| 135 | + struct drm_gem_object *obj) |
| 136 | +{ |
| 137 | + if (unlikely(exec->num_objects == exec->max_objects)) { |
| 138 | + size_t size = exec->max_objects * sizeof(void *); |
| 139 | + void *tmp; |
| 140 | + |
| 141 | + tmp = kvrealloc(exec->objects, size, size + PAGE_SIZE, |
| 142 | + GFP_KERNEL); |
| 143 | + if (!tmp) |
| 144 | + return -ENOMEM; |
| 145 | + |
| 146 | + exec->objects = tmp; |
| 147 | + exec->max_objects += PAGE_SIZE / sizeof(void *); |
| 148 | + } |
| 149 | + drm_gem_object_get(obj); |
| 150 | + exec->objects[exec->num_objects++] = obj; |
| 151 | + |
| 152 | + return 0; |
| 153 | +} |
| 154 | + |
| 155 | +/* Make sure the contended object is locked first */ |
| 156 | +static int drm_exec_lock_contended(struct drm_exec *exec) |
| 157 | +{ |
| 158 | + struct drm_gem_object *obj = exec->contended; |
| 159 | + int ret; |
| 160 | + |
| 161 | + if (likely(!obj)) |
| 162 | + return 0; |
| 163 | + |
| 164 | + /* Always cleanup the contention so that error handling can kick in */ |
| 165 | + exec->contended = NULL; |
| 166 | + if (exec->flags & DRM_EXEC_INTERRUPTIBLE_WAIT) { |
| 167 | + ret = dma_resv_lock_slow_interruptible(obj->resv, |
| 168 | + &exec->ticket); |
| 169 | + if (unlikely(ret)) |
| 170 | + goto error_dropref; |
| 171 | + } else { |
| 172 | + dma_resv_lock_slow(obj->resv, &exec->ticket); |
| 173 | + } |
| 174 | + |
| 175 | + ret = drm_exec_obj_locked(exec, obj); |
| 176 | + if (unlikely(ret)) |
| 177 | + goto error_unlock; |
| 178 | + |
| 179 | + exec->prelocked = obj; |
| 180 | + return 0; |
| 181 | + |
| 182 | +error_unlock: |
| 183 | + dma_resv_unlock(obj->resv); |
| 184 | + |
| 185 | +error_dropref: |
| 186 | + drm_gem_object_put(obj); |
| 187 | + return ret; |
| 188 | +} |
| 189 | + |
| 190 | +/** |
| 191 | + * drm_exec_lock_obj - lock a GEM object for use |
| 192 | + * @exec: the drm_exec object with the state |
| 193 | + * @obj: the GEM object to lock |
| 194 | + * |
| 195 | + * Lock a GEM object for use and grab a reference to it. |
| 196 | + * |
| 197 | + * Returns: -EDEADLK if a contention is detected, -EALREADY when object is |
| 198 | + * already locked (can be suppressed by setting the DRM_EXEC_IGNORE_DUPLICATES |
| 199 | + * flag), -ENOMEM when memory allocation failed and zero for success. |
| 200 | + */ |
| 201 | +int drm_exec_lock_obj(struct drm_exec *exec, struct drm_gem_object *obj) |
| 202 | +{ |
| 203 | + int ret; |
| 204 | + |
| 205 | + ret = drm_exec_lock_contended(exec); |
| 206 | + if (unlikely(ret)) |
| 207 | + return ret; |
| 208 | + |
| 209 | + if (exec->prelocked == obj) { |
| 210 | + drm_gem_object_put(exec->prelocked); |
| 211 | + exec->prelocked = NULL; |
| 212 | + return 0; |
| 213 | + } |
| 214 | + |
| 215 | + if (exec->flags & DRM_EXEC_INTERRUPTIBLE_WAIT) |
| 216 | + ret = dma_resv_lock_interruptible(obj->resv, &exec->ticket); |
| 217 | + else |
| 218 | + ret = dma_resv_lock(obj->resv, &exec->ticket); |
| 219 | + |
| 220 | + if (unlikely(ret == -EDEADLK)) { |
| 221 | + drm_gem_object_get(obj); |
| 222 | + exec->contended = obj; |
| 223 | + return -EDEADLK; |
| 224 | + } |
| 225 | + |
| 226 | + if (unlikely(ret == -EALREADY) && |
| 227 | + exec->flags & DRM_EXEC_IGNORE_DUPLICATES) |
| 228 | + return 0; |
| 229 | + |
| 230 | + if (unlikely(ret)) |
| 231 | + return ret; |
| 232 | + |
| 233 | + ret = drm_exec_obj_locked(exec, obj); |
| 234 | + if (ret) |
| 235 | + goto error_unlock; |
| 236 | + |
| 237 | + return 0; |
| 238 | + |
| 239 | +error_unlock: |
| 240 | + dma_resv_unlock(obj->resv); |
| 241 | + return ret; |
| 242 | +} |
| 243 | +EXPORT_SYMBOL(drm_exec_lock_obj); |
| 244 | + |
| 245 | +/** |
| 246 | + * drm_exec_unlock_obj - unlock a GEM object in this exec context |
| 247 | + * @exec: the drm_exec object with the state |
| 248 | + * @obj: the GEM object to unlock |
| 249 | + * |
| 250 | + * Unlock the GEM object and remove it from the collection of locked objects. |
| 251 | + * Should only be used to unlock the most recently locked objects. It's not time |
| 252 | + * efficient to unlock objects locked long ago. |
| 253 | + */ |
| 254 | +void drm_exec_unlock_obj(struct drm_exec *exec, struct drm_gem_object *obj) |
| 255 | +{ |
| 256 | + unsigned int i; |
| 257 | + |
| 258 | + for (i = exec->num_objects; i--;) { |
| 259 | + if (exec->objects[i] == obj) { |
| 260 | + dma_resv_unlock(obj->resv); |
| 261 | + for (++i; i < exec->num_objects; ++i) |
| 262 | + exec->objects[i - 1] = exec->objects[i]; |
| 263 | + --exec->num_objects; |
| 264 | + drm_gem_object_put(obj); |
| 265 | + return; |
| 266 | + } |
| 267 | + |
| 268 | + } |
| 269 | +} |
| 270 | +EXPORT_SYMBOL(drm_exec_unlock_obj); |
| 271 | + |
| 272 | +/** |
| 273 | + * drm_exec_prepare_obj - prepare a GEM object for use |
| 274 | + * @exec: the drm_exec object with the state |
| 275 | + * @obj: the GEM object to prepare |
| 276 | + * @num_fences: how many fences to reserve |
| 277 | + * |
| 278 | + * Prepare a GEM object for use by locking it and reserving fence slots. |
| 279 | + * |
| 280 | + * Returns: -EDEADLK if a contention is detected, -EALREADY when object is |
| 281 | + * already locked, -ENOMEM when memory allocation failed and zero for success. |
| 282 | + */ |
| 283 | +int drm_exec_prepare_obj(struct drm_exec *exec, struct drm_gem_object *obj, |
| 284 | + unsigned int num_fences) |
| 285 | +{ |
| 286 | + int ret; |
| 287 | + |
| 288 | + ret = drm_exec_lock_obj(exec, obj); |
| 289 | + if (ret) |
| 290 | + return ret; |
| 291 | + |
| 292 | + ret = dma_resv_reserve_fences(obj->resv, num_fences); |
| 293 | + if (ret) { |
| 294 | + drm_exec_unlock_obj(exec, obj); |
| 295 | + return ret; |
| 296 | + } |
| 297 | + |
| 298 | + return 0; |
| 299 | +} |
| 300 | +EXPORT_SYMBOL(drm_exec_prepare_obj); |
| 301 | + |
| 302 | +/** |
| 303 | + * drm_exec_prepare_array - helper to prepare an array of objects |
| 304 | + * @exec: the drm_exec object with the state |
| 305 | + * @objects: array of GEM object to prepare |
| 306 | + * @num_objects: number of GEM objects in the array |
| 307 | + * @num_fences: number of fences to reserve on each GEM object |
| 308 | + * |
| 309 | + * Prepares all GEM objects in an array, aborts on first error. |
| 310 | + * Reserves @num_fences on each GEM object after locking it. |
| 311 | + * |
| 312 | + * Returns: -EDEADLOCK on contention, -EALREADY when object is already locked, |
| 313 | + * -ENOMEM when memory allocation failed and zero for success. |
| 314 | + */ |
| 315 | +int drm_exec_prepare_array(struct drm_exec *exec, |
| 316 | + struct drm_gem_object **objects, |
| 317 | + unsigned int num_objects, |
| 318 | + unsigned int num_fences) |
| 319 | +{ |
| 320 | + int ret; |
| 321 | + |
| 322 | + for (unsigned int i = 0; i < num_objects; ++i) { |
| 323 | + ret = drm_exec_prepare_obj(exec, objects[i], num_fences); |
| 324 | + if (unlikely(ret)) |
| 325 | + return ret; |
| 326 | + } |
| 327 | + |
| 328 | + return 0; |
| 329 | +} |
| 330 | +EXPORT_SYMBOL(drm_exec_prepare_array); |
| 331 | + |
| 332 | +MODULE_DESCRIPTION("DRM execution context"); |
| 333 | +MODULE_LICENSE("Dual MIT/GPL"); |
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