drivers/gpu/drm/i915/gem/i915_gem_pages.c

   1 /*
   2  * SPDX-License-Identifier: MIT
   3  *
   4  * Copyright © 2014-2016 Intel Corporation
   5  */
   6
   7 #include <drm/drm_cache.h>
   8
   9 #include "gt/intel_gt.h"
  10 #include "gt/intel_tlb.h"
  11
  12 #include "i915_drv.h"
  13 #include "i915_gem_object.h"
  14 #include "i915_scatterlist.h"
  15 #include "i915_gem_lmem.h"
  16 #include "i915_gem_mman.h"
  17
  18 void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
  19                                  struct sg_table *pages)
  20 {
  21         struct drm_i915_private *i915 = to_i915(obj->base.dev);
  22         unsigned long supported = RUNTIME_INFO(i915)->page_sizes;
  23         bool shrinkable;
  24         int i;
  25
  26         assert_object_held_shared(obj);
  27
  28         if (i915_gem_object_is_volatile(obj))
  29                 obj->mm.madv = I915_MADV_DONTNEED;
  30
  31         /* Make the pages coherent with the GPU (flushing any swapin). */
  32         if (obj->cache_dirty) {
  33                 WARN_ON_ONCE(IS_DGFX(i915));
  34                 obj->write_domain = 0;
  35                 if (i915_gem_object_has_struct_page(obj))
  36                         drm_clflush_sg(pages);
  37                 obj->cache_dirty = false;
  38         }
  39
  40         obj->mm.get_page.sg_pos = pages->sgl;
  41         obj->mm.get_page.sg_idx = 0;
  42         obj->mm.get_dma_page.sg_pos = pages->sgl;
  43         obj->mm.get_dma_page.sg_idx = 0;
  44
  45         obj->mm.pages = pages;
  46
  47         obj->mm.page_sizes.phys = i915_sg_dma_sizes(pages->sgl);
  48         GEM_BUG_ON(!obj->mm.page_sizes.phys);
  49
  50         /*
  51          * Calculate the supported page-sizes which fit into the given
  52          * sg_page_sizes. This will give us the page-sizes which we may be able
  53          * to use opportunistically when later inserting into the GTT. For
  54          * example if phys=2G, then in theory we should be able to use 1G, 2M,
  55          * 64K or 4K pages, although in practice this will depend on a number of
  56          * other factors.
  57          */
  58         obj->mm.page_sizes.sg = 0;
  59         for_each_set_bit(i, &supported, ilog2(I915_GTT_MAX_PAGE_SIZE) + 1) {
  60                 if (obj->mm.page_sizes.phys & ~0u << i)
  61                         obj->mm.page_sizes.sg |= BIT(i);
  62         }
  63         GEM_BUG_ON(!HAS_PAGE_SIZES(i915, obj->mm.page_sizes.sg));
  64
  65         shrinkable = i915_gem_object_is_shrinkable(obj);
  66
  67         if (i915_gem_object_is_tiled(obj) &&
  68             i915->gem_quirks & GEM_QUIRK_PIN_SWIZZLED_PAGES) {
  69                 GEM_BUG_ON(i915_gem_object_has_tiling_quirk(obj));
  70                 i915_gem_object_set_tiling_quirk(obj);
  71                 GEM_BUG_ON(!list_empty(&obj->mm.link));
  72                 atomic_inc(&obj->mm.shrink_pin);
  73                 shrinkable = false;
  74         }
  75
  76         if (shrinkable && !i915_gem_object_has_self_managed_shrink_list(obj)) {
  77                 struct list_head *list;
  78                 unsigned long flags;
  79
  80                 assert_object_held(obj);
  81                 spin_lock_irqsave(&i915->mm.obj_lock, flags);
  82
  83                 i915->mm.shrink_count++;
  84                 i915->mm.shrink_memory += obj->base.size;
  85
  86                 if (obj->mm.madv != I915_MADV_WILLNEED)
  87                         list = &i915->mm.purge_list;
  88                 else
  89                         list = &i915->mm.shrink_list;
  90                 list_add_tail(&obj->mm.link, list);
  91
  92                 atomic_set(&obj->mm.shrink_pin, 0);
  93                 spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
  94         }
  95 }
  96
  97 int ____i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
  98 {
  99         struct drm_i915_private *i915 = to_i915(obj->base.dev);
 100         int err;
 101
 102         assert_object_held_shared(obj);
 103
 104         if (unlikely(obj->mm.madv != I915_MADV_WILLNEED)) {
 105                 drm_dbg(&i915->drm,
 106                         "Attempting to obtain a purgeable object\n");
 107                 return -EFAULT;
 108         }
 109
 110         err = obj->ops->get_pages(obj);
 111         GEM_BUG_ON(!err && !i915_gem_object_has_pages(obj));
 112
 113         return err;
 114 }
 115
 116 /* Ensure that the associated pages are gathered from the backing storage
 117  * and pinned into our object. i915_gem_object_pin_pages() may be called
 118  * multiple times before they are released by a single call to
 119  * i915_gem_object_unpin_pages() - once the pages are no longer referenced
 120  * either as a result of memory pressure (reaping pages under the shrinker)
 121  * or as the object is itself released.
 122  */
 123 int __i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
 124 {
 125         int err;
 126
 127         assert_object_held(obj);
 128
 129         assert_object_held_shared(obj);
 130
 131         if (unlikely(!i915_gem_object_has_pages(obj))) {
 132                 GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
 133
 134                 err = ____i915_gem_object_get_pages(obj);
 135                 if (err)
 136                         return err;
 137
 138                 smp_mb__before_atomic();
 139         }
 140         atomic_inc(&obj->mm.pages_pin_count);
 141
 142         return 0;
 143 }
 144
 145 int i915_gem_object_pin_pages_unlocked(struct drm_i915_gem_object *obj)
 146 {
 147         struct i915_gem_ww_ctx ww;
 148         int err;
 149
 150         i915_gem_ww_ctx_init(&ww, true);
 151 retry:
 152         err = i915_gem_object_lock(obj, &ww);
 153         if (!err)
 154                 err = i915_gem_object_pin_pages(obj);
 155
 156         if (err == -EDEADLK) {
 157                 err = i915_gem_ww_ctx_backoff(&ww);
 158                 if (!err)
 159                         goto retry;
 160         }
 161         i915_gem_ww_ctx_fini(&ww);
 162         return err;
 163 }
 164
 165 /* Immediately discard the backing storage */
 166 int i915_gem_object_truncate(struct drm_i915_gem_object *obj)
 167 {
 168         if (obj->ops->truncate)
 169                 return obj->ops->truncate(obj);
 170
 171         return 0;
 172 }
 173
 174 static void __i915_gem_object_reset_page_iter(struct drm_i915_gem_object *obj)
 175 {
 176         struct radix_tree_iter iter;
 177         void __rcu **slot;
 178
 179         rcu_read_lock();
 180         radix_tree_for_each_slot(slot, &obj->mm.get_page.radix, &iter, 0)
 181                 radix_tree_delete(&obj->mm.get_page.radix, iter.index);
 182         radix_tree_for_each_slot(slot, &obj->mm.get_dma_page.radix, &iter, 0)
 183                 radix_tree_delete(&obj->mm.get_dma_page.radix, iter.index);
 184         rcu_read_unlock();
 185 }
 186
 187 static void unmap_object(struct drm_i915_gem_object *obj, void *ptr)
 188 {
 189         if (is_vmalloc_addr(ptr))
 190                 vunmap(ptr);
 191 }
 192
 193 static void flush_tlb_invalidate(struct drm_i915_gem_object *obj)
 194 {
 195         struct drm_i915_private *i915 = to_i915(obj->base.dev);
 196         struct intel_gt *gt;
 197         int id;
 198
 199         for_each_gt(gt, i915, id) {
 200                 if (!obj->mm.tlb[id])
 201                         return;
 202
 203                 intel_gt_invalidate_tlb_full(gt, obj->mm.tlb[id]);
 204                 obj->mm.tlb[id] = 0;
 205         }
 206 }
 207
 208 struct sg_table *
 209 __i915_gem_object_unset_pages(struct drm_i915_gem_object *obj)
 210 {
 211         struct sg_table *pages;
 212
 213         assert_object_held_shared(obj);
 214
 215         pages = fetch_and_zero(&obj->mm.pages);
 216         if (IS_ERR_OR_NULL(pages))
 217                 return pages;
 218
 219         if (i915_gem_object_is_volatile(obj))
 220                 obj->mm.madv = I915_MADV_WILLNEED;
 221
 222         if (!i915_gem_object_has_self_managed_shrink_list(obj))
 223                 i915_gem_object_make_unshrinkable(obj);
 224
 225         if (obj->mm.mapping) {
 226                 unmap_object(obj, page_mask_bits(obj->mm.mapping));
 227                 obj->mm.mapping = NULL;
 228         }
 229
 230         __i915_gem_object_reset_page_iter(obj);
 231         obj->mm.page_sizes.phys = obj->mm.page_sizes.sg = 0;
 232
 233         flush_tlb_invalidate(obj);
 234
 235         return pages;
 236 }
 237
 238 int __i915_gem_object_put_pages(struct drm_i915_gem_object *obj)
 239 {
 240         struct sg_table *pages;
 241
 242         if (i915_gem_object_has_pinned_pages(obj))
 243                 return -EBUSY;
 244
 245         /* May be called by shrinker from within get_pages() (on another bo) */
 246         assert_object_held_shared(obj);
 247
 248         i915_gem_object_release_mmap_offset(obj);
 249
 250         /*
 251          * ->put_pages might need to allocate memory for the bit17 swizzle
 252          * array, hence protect them from being reaped by removing them from gtt
 253          * lists early.
 254          */
 255         pages = __i915_gem_object_unset_pages(obj);
 256
 257         /*
 258          * XXX Temporary hijinx to avoid updating all backends to handle
 259          * NULL pages. In the future, when we have more asynchronous
 260          * get_pages backends we should be better able to handle the
 261          * cancellation of the async task in a more uniform manner.
 262          */
 263         if (!IS_ERR_OR_NULL(pages))
 264                 obj->ops->put_pages(obj, pages);
 265
 266         return 0;
 267 }
 268
 269 /* The 'mapping' part of i915_gem_object_pin_map() below */
 270 static void *i915_gem_object_map_page(struct drm_i915_gem_object *obj,
 271                                       enum i915_map_type type)
 272 {
 273         unsigned long n_pages = obj->base.size >> PAGE_SHIFT, i;
 274         struct page *stack[32], **pages = stack, *page;
 275         struct sgt_iter iter;
 276         pgprot_t pgprot;
 277         void *vaddr;
 278
 279         switch (type) {
 280         default:
 281                 MISSING_CASE(type);
 282                 fallthrough;    /* to use PAGE_KERNEL anyway */
 283         case I915_MAP_WB:
 284                 /*
 285                  * On 32b, highmem using a finite set of indirect PTE (i.e.
 286                  * vmap) to provide virtual mappings of the high pages.
 287                  * As these are finite, map_new_virtual() must wait for some
 288                  * other kmap() to finish when it runs out. If we map a large
 289                  * number of objects, there is no method for it to tell us
 290                  * to release the mappings, and we deadlock.
 291                  *
 292                  * However, if we make an explicit vmap of the page, that
 293                  * uses a larger vmalloc arena, and also has the ability
 294                  * to tell us to release unwanted mappings. Most importantly,
 295                  * it will fail and propagate an error instead of waiting
 296                  * forever.
 297                  *
 298                  * So if the page is beyond the 32b boundary, make an explicit
 299                  * vmap.
 300                  */
 301                 if (n_pages == 1 && !PageHighMem(sg_page(obj->mm.pages->sgl)))
 302                         return page_address(sg_page(obj->mm.pages->sgl));
 303                 pgprot = PAGE_KERNEL;
 304                 break;
 305         case I915_MAP_WC:
 306                 pgprot = pgprot_writecombine(PAGE_KERNEL_IO);
 307                 break;
 308         }
 309
 310         if (n_pages > ARRAY_SIZE(stack)) {
 311                 /* Too big for stack -- allocate temporary array instead */
 312                 pages = kvmalloc_array(n_pages, sizeof(*pages), GFP_KERNEL);
 313                 if (!pages)
 314                         return ERR_PTR(-ENOMEM);
 315         }
 316
 317         i = 0;
 318         for_each_sgt_page(page, iter, obj->mm.pages)
 319                 pages[i++] = page;
 320         vaddr = vmap(pages, n_pages, 0, pgprot);
 321         if (pages != stack)
 322                 kvfree(pages);
 323
 324         return vaddr ?: ERR_PTR(-ENOMEM);
 325 }
 326
 327 static void *i915_gem_object_map_pfn(struct drm_i915_gem_object *obj,
 328                                      enum i915_map_type type)
 329 {
 330         resource_size_t iomap = obj->mm.region->iomap.base -
 331                 obj->mm.region->region.start;
 332         unsigned long n_pfn = obj->base.size >> PAGE_SHIFT;
 333         unsigned long stack[32], *pfns = stack, i;
 334         struct sgt_iter iter;
 335         dma_addr_t addr;
 336         void *vaddr;
 337
 338         GEM_BUG_ON(type != I915_MAP_WC);
 339
 340         if (n_pfn > ARRAY_SIZE(stack)) {
 341                 /* Too big for stack -- allocate temporary array instead */
 342                 pfns = kvmalloc_array(n_pfn, sizeof(*pfns), GFP_KERNEL);
 343                 if (!pfns)
 344                         return ERR_PTR(-ENOMEM);
 345         }
 346
 347         i = 0;
 348         for_each_sgt_daddr(addr, iter, obj->mm.pages)
 349                 pfns[i++] = (iomap + addr) >> PAGE_SHIFT;
 350         vaddr = vmap_pfn(pfns, n_pfn, pgprot_writecombine(PAGE_KERNEL_IO));
 351         if (pfns != stack)
 352                 kvfree(pfns);
 353
 354         return vaddr ?: ERR_PTR(-ENOMEM);
 355 }
 356
 357 /* get, pin, and map the pages of the object into kernel space */
 358 void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj,
 359                               enum i915_map_type type)
 360 {
 361         enum i915_map_type has_type;
 362         bool pinned;
 363         void *ptr;
 364         int err;
 365
 366         if (!i915_gem_object_has_struct_page(obj) &&
 367             !i915_gem_object_has_iomem(obj))
 368                 return ERR_PTR(-ENXIO);
 369
 370         if (WARN_ON_ONCE(obj->flags & I915_BO_ALLOC_GPU_ONLY))
 371                 return ERR_PTR(-EINVAL);
 372
 373         assert_object_held(obj);
 374
 375         pinned = !(type & I915_MAP_OVERRIDE);
 376         type &= ~I915_MAP_OVERRIDE;
 377
 378         if (!atomic_inc_not_zero(&obj->mm.pages_pin_count)) {
 379                 if (unlikely(!i915_gem_object_has_pages(obj))) {
 380                         GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
 381
 382                         err = ____i915_gem_object_get_pages(obj);
 383                         if (err)
 384                                 return ERR_PTR(err);
 385
 386                         smp_mb__before_atomic();
 387                 }
 388                 atomic_inc(&obj->mm.pages_pin_count);
 389                 pinned = false;
 390         }
 391         GEM_BUG_ON(!i915_gem_object_has_pages(obj));
 392
 393         /*
 394          * For discrete our CPU mappings needs to be consistent in order to
 395          * function correctly on !x86. When mapping things through TTM, we use
 396          * the same rules to determine the caching type.
 397          *
 398          * The caching rules, starting from DG1:
 399          *
 400          *      - If the object can be placed in device local-memory, then the
 401          *        pages should be allocated and mapped as write-combined only.
 402          *
 403          *      - Everything else is always allocated and mapped as write-back,
 404          *        with the guarantee that everything is also coherent with the
 405          *        GPU.
 406          *
 407          * Internal users of lmem are already expected to get this right, so no
 408          * fudging needed there.
 409          */
 410         if (i915_gem_object_placement_possible(obj, INTEL_MEMORY_LOCAL)) {
 411                 if (type != I915_MAP_WC && !obj->mm.n_placements) {
 412                         ptr = ERR_PTR(-ENODEV);
 413                         goto err_unpin;
 414                 }
 415
 416                 type = I915_MAP_WC;
 417         } else if (IS_DGFX(to_i915(obj->base.dev))) {
 418                 type = I915_MAP_WB;
 419         }
 420
 421         ptr = page_unpack_bits(obj->mm.mapping, &has_type);
 422         if (ptr && has_type != type) {
 423                 if (pinned) {
 424                         ptr = ERR_PTR(-EBUSY);
 425                         goto err_unpin;
 426                 }
 427
 428                 unmap_object(obj, ptr);
 429
 430                 ptr = obj->mm.mapping = NULL;
 431         }
 432
 433         if (!ptr) {
 434                 err = i915_gem_object_wait_moving_fence(obj, true);
 435                 if (err) {
 436                         ptr = ERR_PTR(err);
 437                         goto err_unpin;
 438                 }
 439
 440                 if (GEM_WARN_ON(type == I915_MAP_WC && !pat_enabled()))
 441                         ptr = ERR_PTR(-ENODEV);
 442                 else if (i915_gem_object_has_struct_page(obj))
 443                         ptr = i915_gem_object_map_page(obj, type);
 444                 else
 445                         ptr = i915_gem_object_map_pfn(obj, type);
 446                 if (IS_ERR(ptr))
 447                         goto err_unpin;
 448
 449                 obj->mm.mapping = page_pack_bits(ptr, type);
 450         }
 451
 452         return ptr;
 453
 454 err_unpin:
 455         atomic_dec(&obj->mm.pages_pin_count);
 456         return ptr;
 457 }
 458
 459 void *i915_gem_object_pin_map_unlocked(struct drm_i915_gem_object *obj,
 460                                        enum i915_map_type type)
 461 {
 462         void *ret;
 463
 464         i915_gem_object_lock(obj, NULL);
 465         ret = i915_gem_object_pin_map(obj, type);
 466         i915_gem_object_unlock(obj);
 467
 468         return ret;
 469 }
 470
 471 void __i915_gem_object_flush_map(struct drm_i915_gem_object *obj,
 472                                  unsigned long offset,
 473                                  unsigned long size)
 474 {
 475         enum i915_map_type has_type;
 476         void *ptr;
 477
 478         GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));
 479         GEM_BUG_ON(range_overflows_t(typeof(obj->base.size),
 480                                      offset, size, obj->base.size));
 481
 482         wmb(); /* let all previous writes be visible to coherent partners */
 483         obj->mm.dirty = true;
 484
 485         if (obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_WRITE)
 486                 return;
 487
 488         ptr = page_unpack_bits(obj->mm.mapping, &has_type);
 489         if (has_type == I915_MAP_WC)
 490                 return;
 491
 492         drm_clflush_virt_range(ptr + offset, size);
 493         if (size == obj->base.size) {
 494                 obj->write_domain &= ~I915_GEM_DOMAIN_CPU;
 495                 obj->cache_dirty = false;
 496         }
 497 }
 498
 499 void __i915_gem_object_release_map(struct drm_i915_gem_object *obj)
 500 {
 501         GEM_BUG_ON(!obj->mm.mapping);
 502
 503         /*
 504          * We allow removing the mapping from underneath pinned pages!
 505          *
 506          * Furthermore, since this is an unsafe operation reserved only
 507          * for construction time manipulation, we ignore locking prudence.
 508          */
 509         unmap_object(obj, page_mask_bits(fetch_and_zero(&obj->mm.mapping)));
 510
 511         i915_gem_object_unpin_map(obj);
 512 }
 513
 514 struct scatterlist *
 515 __i915_gem_object_page_iter_get_sg(struct drm_i915_gem_object *obj,
 516                                    struct i915_gem_object_page_iter *iter,
 517                                    pgoff_t n,
 518                                    unsigned int *offset)
 519
 520 {
 521         const bool dma = iter == &obj->mm.get_dma_page ||
 522                          iter == &obj->ttm.get_io_page;
 523         unsigned int idx, count;
 524         struct scatterlist *sg;
 525
 526         might_sleep();
 527         GEM_BUG_ON(n >= obj->base.size >> PAGE_SHIFT);
 528         if (!i915_gem_object_has_pinned_pages(obj))
 529                 assert_object_held(obj);
 530
 531         /* As we iterate forward through the sg, we record each entry in a
 532          * radixtree for quick repeated (backwards) lookups. If we have seen
 533          * this index previously, we will have an entry for it.
 534          *
 535          * Initial lookup is O(N), but this is amortized to O(1) for
 536          * sequential page access (where each new request is consecutive
 537          * to the previous one). Repeated lookups are O(lg(obj->base.size)),
 538          * i.e. O(1) with a large constant!
 539          */
 540         if (n < READ_ONCE(iter->sg_idx))
 541                 goto lookup;
 542
 543         mutex_lock(&iter->lock);
 544
 545         /* We prefer to reuse the last sg so that repeated lookup of this
 546          * (or the subsequent) sg are fast - comparing against the last
 547          * sg is faster than going through the radixtree.
 548          */
 549
 550         sg = iter->sg_pos;
 551         idx = iter->sg_idx;
 552         count = dma ? __sg_dma_page_count(sg) : __sg_page_count(sg);
 553
 554         while (idx + count <= n) {
 555                 void *entry;
 556                 unsigned long i;
 557                 int ret;
 558
 559                 /* If we cannot allocate and insert this entry, or the
 560                  * individual pages from this range, cancel updating the
 561                  * sg_idx so that on this lookup we are forced to linearly
 562                  * scan onwards, but on future lookups we will try the
 563                  * insertion again (in which case we need to be careful of
 564                  * the error return reporting that we have already inserted
 565                  * this index).
 566                  */
 567                 ret = radix_tree_insert(&iter->radix, idx, sg);
 568                 if (ret && ret != -EEXIST)
 569                         goto scan;
 570
 571                 entry = xa_mk_value(idx);
 572                 for (i = 1; i < count; i++) {
 573                         ret = radix_tree_insert(&iter->radix, idx + i, entry);
 574                         if (ret && ret != -EEXIST)
 575                                 goto scan;
 576                 }
 577
 578                 idx += count;
 579                 sg = ____sg_next(sg);
 580                 count = dma ? __sg_dma_page_count(sg) : __sg_page_count(sg);
 581         }
 582
 583 scan:
 584         iter->sg_pos = sg;
 585         iter->sg_idx = idx;
 586
 587         mutex_unlock(&iter->lock);
 588
 589         if (unlikely(n < idx)) /* insertion completed by another thread */
 590                 goto lookup;
 591
 592         /* In case we failed to insert the entry into the radixtree, we need
 593          * to look beyond the current sg.
 594          */
 595         while (idx + count <= n) {
 596                 idx += count;
 597                 sg = ____sg_next(sg);
 598                 count = dma ? __sg_dma_page_count(sg) : __sg_page_count(sg);
 599         }
 600
 601         *offset = n - idx;
 602         return sg;
 603
 604 lookup:
 605         rcu_read_lock();
 606
 607         sg = radix_tree_lookup(&iter->radix, n);
 608         GEM_BUG_ON(!sg);
 609
 610         /* If this index is in the middle of multi-page sg entry,
 611          * the radix tree will contain a value entry that points
 612          * to the start of that range. We will return the pointer to
 613          * the base page and the offset of this page within the
 614          * sg entry's range.
 615          */
 616         *offset = 0;
 617         if (unlikely(xa_is_value(sg))) {
 618                 unsigned long base = xa_to_value(sg);
 619
 620                 sg = radix_tree_lookup(&iter->radix, base);
 621                 GEM_BUG_ON(!sg);
 622
 623                 *offset = n - base;
 624         }
 625
 626         rcu_read_unlock();
 627
 628         return sg;
 629 }
 630
 631 struct page *
 632 __i915_gem_object_get_page(struct drm_i915_gem_object *obj, pgoff_t n)
 633 {
 634         struct scatterlist *sg;
 635         unsigned int offset;
 636
 637         GEM_BUG_ON(!i915_gem_object_has_struct_page(obj));
 638
 639         sg = i915_gem_object_get_sg(obj, n, &offset);
 640         return nth_page(sg_page(sg), offset);
 641 }
 642
 643 /* Like i915_gem_object_get_page(), but mark the returned page dirty */
 644 struct page *
 645 __i915_gem_object_get_dirty_page(struct drm_i915_gem_object *obj, pgoff_t n)
 646 {
 647         struct page *page;
 648
 649         page = i915_gem_object_get_page(obj, n);
 650         if (!obj->mm.dirty)
 651                 set_page_dirty(page);
 652
 653         return page;
 654 }
 655
 656 dma_addr_t
 657 __i915_gem_object_get_dma_address_len(struct drm_i915_gem_object *obj,
 658                                       pgoff_t n, unsigned int *len)
 659 {
 660         struct scatterlist *sg;
 661         unsigned int offset;
 662
 663         sg = i915_gem_object_get_sg_dma(obj, n, &offset);
 664
 665         if (len)
 666                 *len = sg_dma_len(sg) - (offset << PAGE_SHIFT);
 667
 668         return sg_dma_address(sg) + (offset << PAGE_SHIFT);
 669 }
 670
 671 dma_addr_t
 672 __i915_gem_object_get_dma_address(struct drm_i915_gem_object *obj, pgoff_t n)
 673 {
 674         return i915_gem_object_get_dma_address_len(obj, n, NULL);
 675 }