drivers/gpu/drm/ttm/ttm_bo_util.c

   1 /* SPDX-License-Identifier: GPL-2.0 OR MIT */
   2 /**************************************************************************
   3  *
   4  * Copyright (c) 2007-2009 VMware, Inc., Palo Alto, CA., USA
   5  * All Rights Reserved.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a
   8  * copy of this software and associated documentation files (the
   9  * "Software"), to deal in the Software without restriction, including
  10  * without limitation the rights to use, copy, modify, merge, publish,
  11  * distribute, sub license, and/or sell copies of the Software, and to
  12  * permit persons to whom the Software is furnished to do so, subject to
  13  * the following conditions:
  14  *
  15  * The above copyright notice and this permission notice (including the
  16  * next paragraph) shall be included in all copies or substantial portions
  17  * of the Software.
  18  *
  19  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  20  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21  * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
  22  * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
  23  * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  24  * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  25  * USE OR OTHER DEALINGS IN THE SOFTWARE.
  26  *
  27  **************************************************************************/
  28 /*
  29  * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
  30  */
  31
  32 #include <drm/ttm/ttm_bo_driver.h>
  33 #include <drm/ttm/ttm_placement.h>
  34 #include <drm/drm_cache.h>
  35 #include <drm/drm_vma_manager.h>
  36 #include <linux/iosys-map.h>
  37 #include <linux/io.h>
  38 #include <linux/highmem.h>
  39 #include <linux/wait.h>
  40 #include <linux/slab.h>
  41 #include <linux/vmalloc.h>
  42 #include <linux/module.h>
  43 #include <linux/dma-resv.h>
  44
  45 struct ttm_transfer_obj {
  46         struct ttm_buffer_object base;
  47         struct ttm_buffer_object *bo;
  48 };
  49
  50 int ttm_mem_io_reserve(struct ttm_device *bdev,
  51                        struct ttm_resource *mem)
  52 {
  53         if (mem->bus.offset || mem->bus.addr)
  54                 return 0;
  55
  56         mem->bus.is_iomem = false;
  57         if (!bdev->funcs->io_mem_reserve)
  58                 return 0;
  59
  60         return bdev->funcs->io_mem_reserve(bdev, mem);
  61 }
  62
  63 void ttm_mem_io_free(struct ttm_device *bdev,
  64                      struct ttm_resource *mem)
  65 {
  66         if (!mem)
  67                 return;
  68
  69         if (!mem->bus.offset && !mem->bus.addr)
  70                 return;
  71
  72         if (bdev->funcs->io_mem_free)
  73                 bdev->funcs->io_mem_free(bdev, mem);
  74
  75         mem->bus.offset = 0;
  76         mem->bus.addr = NULL;
  77 }
  78
  79 /**
  80  * ttm_move_memcpy - Helper to perform a memcpy ttm move operation.
  81  * @clear: Whether to clear rather than copy.
  82  * @num_pages: Number of pages of the operation.
  83  * @dst_iter: A struct ttm_kmap_iter representing the destination resource.
  84  * @src_iter: A struct ttm_kmap_iter representing the source resource.
  85  *
  86  * This function is intended to be able to move out async under a
  87  * dma-fence if desired.
  88  */
  89 void ttm_move_memcpy(bool clear,
  90                      u32 num_pages,
  91                      struct ttm_kmap_iter *dst_iter,
  92                      struct ttm_kmap_iter *src_iter)
  93 {
  94         const struct ttm_kmap_iter_ops *dst_ops = dst_iter->ops;
  95         const struct ttm_kmap_iter_ops *src_ops = src_iter->ops;
  96         struct iosys_map src_map, dst_map;
  97         pgoff_t i;
  98
  99         /* Single TTM move. NOP */
 100         if (dst_ops->maps_tt && src_ops->maps_tt)
 101                 return;
 102
 103         /* Don't move nonexistent data. Clear destination instead. */
 104         if (clear) {
 105                 for (i = 0; i < num_pages; ++i) {
 106                         dst_ops->map_local(dst_iter, &dst_map, i);
 107                         if (dst_map.is_iomem)
 108                                 memset_io(dst_map.vaddr_iomem, 0, PAGE_SIZE);
 109                         else
 110                                 memset(dst_map.vaddr, 0, PAGE_SIZE);
 111                         if (dst_ops->unmap_local)
 112                                 dst_ops->unmap_local(dst_iter, &dst_map);
 113                 }
 114                 return;
 115         }
 116
 117         for (i = 0; i < num_pages; ++i) {
 118                 dst_ops->map_local(dst_iter, &dst_map, i);
 119                 src_ops->map_local(src_iter, &src_map, i);
 120
 121                 drm_memcpy_from_wc(&dst_map, &src_map, PAGE_SIZE);
 122
 123                 if (src_ops->unmap_local)
 124                         src_ops->unmap_local(src_iter, &src_map);
 125                 if (dst_ops->unmap_local)
 126                         dst_ops->unmap_local(dst_iter, &dst_map);
 127         }
 128 }
 129 EXPORT_SYMBOL(ttm_move_memcpy);
 130
 131 int ttm_bo_move_memcpy(struct ttm_buffer_object *bo,
 132                        struct ttm_operation_ctx *ctx,
 133                        struct ttm_resource *dst_mem)
 134 {
 135         struct ttm_device *bdev = bo->bdev;
 136         struct ttm_resource_manager *dst_man =
 137                 ttm_manager_type(bo->bdev, dst_mem->mem_type);
 138         struct ttm_tt *ttm = bo->ttm;
 139         struct ttm_resource *src_mem = bo->resource;
 140         struct ttm_resource_manager *src_man =
 141                 ttm_manager_type(bdev, src_mem->mem_type);
 142         union {
 143                 struct ttm_kmap_iter_tt tt;
 144                 struct ttm_kmap_iter_linear_io io;
 145         } _dst_iter, _src_iter;
 146         struct ttm_kmap_iter *dst_iter, *src_iter;
 147         bool clear;
 148         int ret = 0;
 149
 150         if (ttm && ((ttm->page_flags & TTM_TT_FLAG_SWAPPED) ||
 151                     dst_man->use_tt)) {
 152                 ret = ttm_tt_populate(bdev, ttm, ctx);
 153                 if (ret)
 154                         return ret;
 155         }
 156
 157         dst_iter = ttm_kmap_iter_linear_io_init(&_dst_iter.io, bdev, dst_mem);
 158         if (PTR_ERR(dst_iter) == -EINVAL && dst_man->use_tt)
 159                 dst_iter = ttm_kmap_iter_tt_init(&_dst_iter.tt, bo->ttm);
 160         if (IS_ERR(dst_iter))
 161                 return PTR_ERR(dst_iter);
 162
 163         src_iter = ttm_kmap_iter_linear_io_init(&_src_iter.io, bdev, src_mem);
 164         if (PTR_ERR(src_iter) == -EINVAL && src_man->use_tt)
 165                 src_iter = ttm_kmap_iter_tt_init(&_src_iter.tt, bo->ttm);
 166         if (IS_ERR(src_iter)) {
 167                 ret = PTR_ERR(src_iter);
 168                 goto out_src_iter;
 169         }
 170
 171         clear = src_iter->ops->maps_tt && (!ttm || !ttm_tt_is_populated(ttm));
 172         if (!(clear && ttm && !(ttm->page_flags & TTM_TT_FLAG_ZERO_ALLOC)))
 173                 ttm_move_memcpy(clear, dst_mem->num_pages, dst_iter, src_iter);
 174
 175         if (!src_iter->ops->maps_tt)
 176                 ttm_kmap_iter_linear_io_fini(&_src_iter.io, bdev, src_mem);
 177         ttm_bo_move_sync_cleanup(bo, dst_mem);
 178
 179 out_src_iter:
 180         if (!dst_iter->ops->maps_tt)
 181                 ttm_kmap_iter_linear_io_fini(&_dst_iter.io, bdev, dst_mem);
 182
 183         return ret;
 184 }
 185 EXPORT_SYMBOL(ttm_bo_move_memcpy);
 186
 187 static void ttm_transfered_destroy(struct ttm_buffer_object *bo)
 188 {
 189         struct ttm_transfer_obj *fbo;
 190
 191         fbo = container_of(bo, struct ttm_transfer_obj, base);
 192         dma_resv_fini(&fbo->base.base._resv);
 193         ttm_bo_put(fbo->bo);
 194         kfree(fbo);
 195 }
 196
 197 /**
 198  * ttm_buffer_object_transfer
 199  *
 200  * @bo: A pointer to a struct ttm_buffer_object.
 201  * @new_obj: A pointer to a pointer to a newly created ttm_buffer_object,
 202  * holding the data of @bo with the old placement.
 203  *
 204  * This is a utility function that may be called after an accelerated move
 205  * has been scheduled. A new buffer object is created as a placeholder for
 206  * the old data while it's being copied. When that buffer object is idle,
 207  * it can be destroyed, releasing the space of the old placement.
 208  * Returns:
 209  * !0: Failure.
 210  */
 211
 212 static int ttm_buffer_object_transfer(struct ttm_buffer_object *bo,
 213                                       struct ttm_buffer_object **new_obj)
 214 {
 215         struct ttm_transfer_obj *fbo;
 216         int ret;
 217
 218         fbo = kmalloc(sizeof(*fbo), GFP_KERNEL);
 219         if (!fbo)
 220                 return -ENOMEM;
 221
 222         fbo->base = *bo;
 223
 224         /**
 225          * Fix up members that we shouldn't copy directly:
 226          * TODO: Explicit member copy would probably be better here.
 227          */
 228
 229         atomic_inc(&ttm_glob.bo_count);
 230         INIT_LIST_HEAD(&fbo->base.ddestroy);
 231         drm_vma_node_reset(&fbo->base.base.vma_node);
 232
 233         kref_init(&fbo->base.kref);
 234         fbo->base.destroy = &ttm_transfered_destroy;
 235         fbo->base.pin_count = 0;
 236         if (bo->type != ttm_bo_type_sg)
 237                 fbo->base.base.resv = &fbo->base.base._resv;
 238
 239         dma_resv_init(&fbo->base.base._resv);
 240         fbo->base.base.dev = NULL;
 241         ret = dma_resv_trylock(&fbo->base.base._resv);
 242         WARN_ON(!ret);
 243
 244         if (fbo->base.resource) {
 245                 ttm_resource_set_bo(fbo->base.resource, &fbo->base);
 246                 bo->resource = NULL;
 247                 ttm_bo_set_bulk_move(&fbo->base, NULL);
 248         } else {
 249                 fbo->base.bulk_move = NULL;
 250         }
 251
 252         ret = dma_resv_reserve_fences(&fbo->base.base._resv, 1);
 253         if (ret) {
 254                 kfree(fbo);
 255                 return ret;
 256         }
 257
 258         ttm_bo_get(bo);
 259         fbo->bo = bo;
 260
 261         ttm_bo_move_to_lru_tail_unlocked(&fbo->base);
 262
 263         *new_obj = &fbo->base;
 264         return 0;
 265 }
 266
 267 pgprot_t ttm_io_prot(struct ttm_buffer_object *bo, struct ttm_resource *res,
 268                      pgprot_t tmp)
 269 {
 270         struct ttm_resource_manager *man;
 271         enum ttm_caching caching;
 272
 273         man = ttm_manager_type(bo->bdev, res->mem_type);
 274         caching = man->use_tt ? bo->ttm->caching : res->bus.caching;
 275
 276         return ttm_prot_from_caching(caching, tmp);
 277 }
 278 EXPORT_SYMBOL(ttm_io_prot);
 279
 280 static int ttm_bo_ioremap(struct ttm_buffer_object *bo,
 281                           unsigned long offset,
 282                           unsigned long size,
 283                           struct ttm_bo_kmap_obj *map)
 284 {
 285         struct ttm_resource *mem = bo->resource;
 286
 287         if (bo->resource->bus.addr) {
 288                 map->bo_kmap_type = ttm_bo_map_premapped;
 289                 map->virtual = ((u8 *)bo->resource->bus.addr) + offset;
 290         } else {
 291                 resource_size_t res = bo->resource->bus.offset + offset;
 292
 293                 map->bo_kmap_type = ttm_bo_map_iomap;
 294                 if (mem->bus.caching == ttm_write_combined)
 295                         map->virtual = ioremap_wc(res, size);
 296 #ifdef CONFIG_X86
 297                 else if (mem->bus.caching == ttm_cached)
 298                         map->virtual = ioremap_cache(res, size);
 299 #endif
 300                 else
 301                         map->virtual = ioremap(res, size);
 302         }
 303         return (!map->virtual) ? -ENOMEM : 0;
 304 }
 305
 306 static int ttm_bo_kmap_ttm(struct ttm_buffer_object *bo,
 307                            unsigned long start_page,
 308                            unsigned long num_pages,
 309                            struct ttm_bo_kmap_obj *map)
 310 {
 311         struct ttm_resource *mem = bo->resource;
 312         struct ttm_operation_ctx ctx = {
 313                 .interruptible = false,
 314                 .no_wait_gpu = false
 315         };
 316         struct ttm_tt *ttm = bo->ttm;
 317         pgprot_t prot;
 318         int ret;
 319
 320         BUG_ON(!ttm);
 321
 322         ret = ttm_tt_populate(bo->bdev, ttm, &ctx);
 323         if (ret)
 324                 return ret;
 325
 326         if (num_pages == 1 && ttm->caching == ttm_cached) {
 327                 /*
 328                  * We're mapping a single page, and the desired
 329                  * page protection is consistent with the bo.
 330                  */
 331
 332                 map->bo_kmap_type = ttm_bo_map_kmap;
 333                 map->page = ttm->pages[start_page];
 334                 map->virtual = kmap(map->page);
 335         } else {
 336                 /*
 337                  * We need to use vmap to get the desired page protection
 338                  * or to make the buffer object look contiguous.
 339                  */
 340                 prot = ttm_io_prot(bo, mem, PAGE_KERNEL);
 341                 map->bo_kmap_type = ttm_bo_map_vmap;
 342                 map->virtual = vmap(ttm->pages + start_page, num_pages,
 343                                     0, prot);
 344         }
 345         return (!map->virtual) ? -ENOMEM : 0;
 346 }
 347
 348 int ttm_bo_kmap(struct ttm_buffer_object *bo,
 349                 unsigned long start_page, unsigned long num_pages,
 350                 struct ttm_bo_kmap_obj *map)
 351 {
 352         unsigned long offset, size;
 353         int ret;
 354
 355         map->virtual = NULL;
 356         map->bo = bo;
 357         if (num_pages > bo->resource->num_pages)
 358                 return -EINVAL;
 359         if ((start_page + num_pages) > bo->resource->num_pages)
 360                 return -EINVAL;
 361
 362         ret = ttm_mem_io_reserve(bo->bdev, bo->resource);
 363         if (ret)
 364                 return ret;
 365         if (!bo->resource->bus.is_iomem) {
 366                 return ttm_bo_kmap_ttm(bo, start_page, num_pages, map);
 367         } else {
 368                 offset = start_page << PAGE_SHIFT;
 369                 size = num_pages << PAGE_SHIFT;
 370                 return ttm_bo_ioremap(bo, offset, size, map);
 371         }
 372 }
 373 EXPORT_SYMBOL(ttm_bo_kmap);
 374
 375 void ttm_bo_kunmap(struct ttm_bo_kmap_obj *map)
 376 {
 377         if (!map->virtual)
 378                 return;
 379         switch (map->bo_kmap_type) {
 380         case ttm_bo_map_iomap:
 381                 iounmap(map->virtual);
 382                 break;
 383         case ttm_bo_map_vmap:
 384                 vunmap(map->virtual);
 385                 break;
 386         case ttm_bo_map_kmap:
 387                 kunmap(map->page);
 388                 break;
 389         case ttm_bo_map_premapped:
 390                 break;
 391         default:
 392                 BUG();
 393         }
 394         ttm_mem_io_free(map->bo->bdev, map->bo->resource);
 395         map->virtual = NULL;
 396         map->page = NULL;
 397 }
 398 EXPORT_SYMBOL(ttm_bo_kunmap);
 399
 400 int ttm_bo_vmap(struct ttm_buffer_object *bo, struct iosys_map *map)
 401 {
 402         struct ttm_resource *mem = bo->resource;
 403         int ret;
 404
 405         ret = ttm_mem_io_reserve(bo->bdev, mem);
 406         if (ret)
 407                 return ret;
 408
 409         if (mem->bus.is_iomem) {
 410                 void __iomem *vaddr_iomem;
 411
 412                 if (mem->bus.addr)
 413                         vaddr_iomem = (void __iomem *)mem->bus.addr;
 414                 else if (mem->bus.caching == ttm_write_combined)
 415                         vaddr_iomem = ioremap_wc(mem->bus.offset,
 416                                                  bo->base.size);
 417 #ifdef CONFIG_X86
 418                 else if (mem->bus.caching == ttm_cached)
 419                         vaddr_iomem = ioremap_cache(mem->bus.offset,
 420                                                   bo->base.size);
 421 #endif
 422                 else
 423                         vaddr_iomem = ioremap(mem->bus.offset, bo->base.size);
 424
 425                 if (!vaddr_iomem)
 426                         return -ENOMEM;
 427
 428                 iosys_map_set_vaddr_iomem(map, vaddr_iomem);
 429
 430         } else {
 431                 struct ttm_operation_ctx ctx = {
 432                         .interruptible = false,
 433                         .no_wait_gpu = false
 434                 };
 435                 struct ttm_tt *ttm = bo->ttm;
 436                 pgprot_t prot;
 437                 void *vaddr;
 438
 439                 ret = ttm_tt_populate(bo->bdev, ttm, &ctx);
 440                 if (ret)
 441                         return ret;
 442
 443                 /*
 444                  * We need to use vmap to get the desired page protection
 445                  * or to make the buffer object look contiguous.
 446                  */
 447                 prot = ttm_io_prot(bo, mem, PAGE_KERNEL);
 448                 vaddr = vmap(ttm->pages, ttm->num_pages, 0, prot);
 449                 if (!vaddr)
 450                         return -ENOMEM;
 451
 452                 iosys_map_set_vaddr(map, vaddr);
 453         }
 454
 455         return 0;
 456 }
 457 EXPORT_SYMBOL(ttm_bo_vmap);
 458
 459 void ttm_bo_vunmap(struct ttm_buffer_object *bo, struct iosys_map *map)
 460 {
 461         struct ttm_resource *mem = bo->resource;
 462
 463         if (iosys_map_is_null(map))
 464                 return;
 465
 466         if (!map->is_iomem)
 467                 vunmap(map->vaddr);
 468         else if (!mem->bus.addr)
 469                 iounmap(map->vaddr_iomem);
 470         iosys_map_clear(map);
 471
 472         ttm_mem_io_free(bo->bdev, bo->resource);
 473 }
 474 EXPORT_SYMBOL(ttm_bo_vunmap);
 475
 476 static int ttm_bo_wait_free_node(struct ttm_buffer_object *bo,
 477                                  bool dst_use_tt)
 478 {
 479         int ret;
 480         ret = ttm_bo_wait(bo, false, false);
 481         if (ret)
 482                 return ret;
 483
 484         if (!dst_use_tt)
 485                 ttm_bo_tt_destroy(bo);
 486         ttm_resource_free(bo, &bo->resource);
 487         return 0;
 488 }
 489
 490 static int ttm_bo_move_to_ghost(struct ttm_buffer_object *bo,
 491                                 struct dma_fence *fence,
 492                                 bool dst_use_tt)
 493 {
 494         struct ttm_buffer_object *ghost_obj;
 495         int ret;
 496
 497         /**
 498          * This should help pipeline ordinary buffer moves.
 499          *
 500          * Hang old buffer memory on a new buffer object,
 501          * and leave it to be released when the GPU
 502          * operation has completed.
 503          */
 504
 505         ret = ttm_buffer_object_transfer(bo, &ghost_obj);
 506         if (ret)
 507                 return ret;
 508
 509         dma_resv_add_fence(&ghost_obj->base._resv, fence,
 510                            DMA_RESV_USAGE_KERNEL);
 511
 512         /**
 513          * If we're not moving to fixed memory, the TTM object
 514          * needs to stay alive. Otherwhise hang it on the ghost
 515          * bo to be unbound and destroyed.
 516          */
 517
 518         if (dst_use_tt)
 519                 ghost_obj->ttm = NULL;
 520         else
 521                 bo->ttm = NULL;
 522
 523         dma_resv_unlock(&ghost_obj->base._resv);
 524         ttm_bo_put(ghost_obj);
 525         return 0;
 526 }
 527
 528 static void ttm_bo_move_pipeline_evict(struct ttm_buffer_object *bo,
 529                                        struct dma_fence *fence)
 530 {
 531         struct ttm_device *bdev = bo->bdev;
 532         struct ttm_resource_manager *from;
 533
 534         from = ttm_manager_type(bdev, bo->resource->mem_type);
 535
 536         /**
 537          * BO doesn't have a TTM we need to bind/unbind. Just remember
 538          * this eviction and free up the allocation
 539          */
 540         spin_lock(&from->move_lock);
 541         if (!from->move || dma_fence_is_later(fence, from->move)) {
 542                 dma_fence_put(from->move);
 543                 from->move = dma_fence_get(fence);
 544         }
 545         spin_unlock(&from->move_lock);
 546
 547         ttm_resource_free(bo, &bo->resource);
 548 }
 549
 550 int ttm_bo_move_accel_cleanup(struct ttm_buffer_object *bo,
 551                               struct dma_fence *fence,
 552                               bool evict,
 553                               bool pipeline,
 554                               struct ttm_resource *new_mem)
 555 {
 556         struct ttm_device *bdev = bo->bdev;
 557         struct ttm_resource_manager *from = ttm_manager_type(bdev, bo->resource->mem_type);
 558         struct ttm_resource_manager *man = ttm_manager_type(bdev, new_mem->mem_type);
 559         int ret = 0;
 560
 561         dma_resv_add_fence(bo->base.resv, fence, DMA_RESV_USAGE_KERNEL);
 562         if (!evict)
 563                 ret = ttm_bo_move_to_ghost(bo, fence, man->use_tt);
 564         else if (!from->use_tt && pipeline)
 565                 ttm_bo_move_pipeline_evict(bo, fence);
 566         else
 567                 ret = ttm_bo_wait_free_node(bo, man->use_tt);
 568
 569         if (ret)
 570                 return ret;
 571
 572         ttm_bo_assign_mem(bo, new_mem);
 573
 574         return 0;
 575 }
 576 EXPORT_SYMBOL(ttm_bo_move_accel_cleanup);
 577
 578 void ttm_bo_move_sync_cleanup(struct ttm_buffer_object *bo,
 579                               struct ttm_resource *new_mem)
 580 {
 581         struct ttm_device *bdev = bo->bdev;
 582         struct ttm_resource_manager *man = ttm_manager_type(bdev, new_mem->mem_type);
 583         int ret;
 584
 585         ret = ttm_bo_wait_free_node(bo, man->use_tt);
 586         if (WARN_ON(ret))
 587                 return;
 588
 589         ttm_bo_assign_mem(bo, new_mem);
 590 }
 591 EXPORT_SYMBOL(ttm_bo_move_sync_cleanup);
 592
 593 /**
 594  * ttm_bo_pipeline_gutting - purge the contents of a bo
 595  * @bo: The buffer object
 596  *
 597  * Purge the contents of a bo, async if the bo is not idle.
 598  * After a successful call, the bo is left unpopulated in
 599  * system placement. The function may wait uninterruptible
 600  * for idle on OOM.
 601  *
 602  * Return: 0 if successful, negative error code on failure.
 603  */
 604 int ttm_bo_pipeline_gutting(struct ttm_buffer_object *bo)
 605 {
 606         static const struct ttm_place sys_mem = { .mem_type = TTM_PL_SYSTEM };
 607         struct ttm_buffer_object *ghost;
 608         struct ttm_resource *sys_res;
 609         struct ttm_tt *ttm;
 610         int ret;
 611
 612         ret = ttm_resource_alloc(bo, &sys_mem, &sys_res);
 613         if (ret)
 614                 return ret;
 615
 616         /* If already idle, no need for ghost object dance. */
 617         ret = ttm_bo_wait(bo, false, true);
 618         if (ret != -EBUSY) {
 619                 if (!bo->ttm) {
 620                         /* See comment below about clearing. */
 621                         ret = ttm_tt_create(bo, true);
 622                         if (ret)
 623                                 goto error_free_sys_mem;
 624                 } else {
 625                         ttm_tt_unpopulate(bo->bdev, bo->ttm);
 626                         if (bo->type == ttm_bo_type_device)
 627                                 ttm_tt_mark_for_clear(bo->ttm);
 628                 }
 629                 ttm_resource_free(bo, &bo->resource);
 630                 ttm_bo_assign_mem(bo, sys_res);
 631                 return 0;
 632         }
 633
 634         /*
 635          * We need an unpopulated ttm_tt after giving our current one,
 636          * if any, to the ghost object. And we can't afford to fail
 637          * creating one *after* the operation. If the bo subsequently gets
 638          * resurrected, make sure it's cleared (if ttm_bo_type_device)
 639          * to avoid leaking sensitive information to user-space.
 640          */
 641
 642         ttm = bo->ttm;
 643         bo->ttm = NULL;
 644         ret = ttm_tt_create(bo, true);
 645         swap(bo->ttm, ttm);
 646         if (ret)
 647                 goto error_free_sys_mem;
 648
 649         ret = ttm_buffer_object_transfer(bo, &ghost);
 650         if (ret)
 651                 goto error_destroy_tt;
 652
 653         ret = dma_resv_copy_fences(&ghost->base._resv, bo->base.resv);
 654         /* Last resort, wait for the BO to be idle when we are OOM */
 655         if (ret)
 656                 ttm_bo_wait(bo, false, false);
 657
 658         dma_resv_unlock(&ghost->base._resv);
 659         ttm_bo_put(ghost);
 660         bo->ttm = ttm;
 661         ttm_bo_assign_mem(bo, sys_res);
 662         return 0;
 663
 664 error_destroy_tt:
 665         ttm_tt_destroy(bo->bdev, ttm);
 666
 667 error_free_sys_mem:
 668         ttm_resource_free(bo, &sys_res);
 669         return ret;
 670 }