drivers/gpu/drm/drm_mm.c

   1 /**************************************************************************
   2  *
   3  * Copyright 2006 Tungsten Graphics, Inc., Bismarck, ND., USA.
   4  * All Rights Reserved.
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a
   7  * copy of this software and associated documentation files (the
   8  * "Software"), to deal in the Software without restriction, including
   9  * without limitation the rights to use, copy, modify, merge, publish,
  10  * distribute, sub license, and/or sell copies of the Software, and to
  11  * permit persons to whom the Software is furnished to do so, subject to
  12  * the following conditions:
  13  *
  14  * The above copyright notice and this permission notice (including the
  15  * next paragraph) shall be included in all copies or substantial portions
  16  * of the Software.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  19  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  20  * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
  21  * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
  22  * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  23  * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  24  * USE OR OTHER DEALINGS IN THE SOFTWARE.
  25  *
  26  *
  27  **************************************************************************/
  28
  29 /*
  30  * Generic simple memory manager implementation. Intended to be used as a base
  31  * class implementation for more advanced memory managers.
  32  *
  33  * Note that the algorithm used is quite simple and there might be substantial
  34  * performance gains if a smarter free list is implemented. Currently it is just an
  35  * unordered stack of free regions. This could easily be improved if an RB-tree
  36  * is used instead. At least if we expect heavy fragmentation.
  37  *
  38  * Aligned allocations can also see improvement.
  39  *
  40  * Authors:
  41  * Thomas Hellström <thomas-at-tungstengraphics-dot-com>
  42  */
  43
  44 #include <drm/drmP.h>
  45 #include <drm/drm_mm.h>
  46 #include <linux/slab.h>
  47 #include <linux/seq_file.h>
  48 #include <linux/export.h>
  49 #include <linux/interval_tree_generic.h>
  50
  51 /**
  52  * DOC: Overview
  53  *
  54  * drm_mm provides a simple range allocator. The drivers are free to use the
  55  * resource allocator from the linux core if it suits them, the upside of drm_mm
  56  * is that it's in the DRM core. Which means that it's easier to extend for
  57  * some of the crazier special purpose needs of gpus.
  58  *
  59  * The main data struct is &drm_mm, allocations are tracked in &drm_mm_node.
  60  * Drivers are free to embed either of them into their own suitable
  61  * datastructures. drm_mm itself will not do any allocations of its own, so if
  62  * drivers choose not to embed nodes they need to still allocate them
  63  * themselves.
  64  *
  65  * The range allocator also supports reservation of preallocated blocks. This is
  66  * useful for taking over initial mode setting configurations from the firmware,
  67  * where an object needs to be created which exactly matches the firmware's
  68  * scanout target. As long as the range is still free it can be inserted anytime
  69  * after the allocator is initialized, which helps with avoiding looped
  70  * depencies in the driver load sequence.
  71  *
  72  * drm_mm maintains a stack of most recently freed holes, which of all
  73  * simplistic datastructures seems to be a fairly decent approach to clustering
  74  * allocations and avoiding too much fragmentation. This means free space
  75  * searches are O(num_holes). Given that all the fancy features drm_mm supports
  76  * something better would be fairly complex and since gfx thrashing is a fairly
  77  * steep cliff not a real concern. Removing a node again is O(1).
  78  *
  79  * drm_mm supports a few features: Alignment and range restrictions can be
  80  * supplied. Further more every &drm_mm_node has a color value (which is just an
  81  * opaqua unsigned long) which in conjunction with a driver callback can be used
  82  * to implement sophisticated placement restrictions. The i915 DRM driver uses
  83  * this to implement guard pages between incompatible caching domains in the
  84  * graphics TT.
  85  *
  86  * Two behaviors are supported for searching and allocating: bottom-up and top-down.
  87  * The default is bottom-up. Top-down allocation can be used if the memory area
  88  * has different restrictions, or just to reduce fragmentation.
  89  *
  90  * Finally iteration helpers to walk all nodes and all holes are provided as are
  91  * some basic allocator dumpers for debugging.
  92  */
  93
  94 static struct drm_mm_node *drm_mm_search_free_generic(const struct drm_mm *mm,
  95                                                 u64 size,
  96                                                 unsigned alignment,
  97                                                 unsigned long color,
  98                                                 enum drm_mm_search_flags flags);
  99 static struct drm_mm_node *drm_mm_search_free_in_range_generic(const struct drm_mm *mm,
 100                                                 u64 size,
 101                                                 unsigned alignment,
 102                                                 unsigned long color,
 103                                                 u64 start,
 104                                                 u64 end,
 105                                                 enum drm_mm_search_flags flags);
 106
 107 #define START(node) ((node)->start)
 108 #define LAST(node)  ((node)->start + (node)->size - 1)
 109
 110 INTERVAL_TREE_DEFINE(struct drm_mm_node, rb,
 111                      u64, __subtree_last,
 112                      START, LAST, static inline, drm_mm_interval_tree)
 113
 114 struct drm_mm_node *
 115 drm_mm_interval_first(struct drm_mm *mm, u64 start, u64 last)
 116 {
 117         return drm_mm_interval_tree_iter_first(&mm->interval_tree,
 118                                                start, last);
 119 }
 120 EXPORT_SYMBOL(drm_mm_interval_first);
 121
 122 struct drm_mm_node *
 123 drm_mm_interval_next(struct drm_mm_node *node, u64 start, u64 last)
 124 {
 125         return drm_mm_interval_tree_iter_next(node, start, last);
 126 }
 127 EXPORT_SYMBOL(drm_mm_interval_next);
 128
 129 static void drm_mm_interval_tree_add_node(struct drm_mm_node *hole_node,
 130                                           struct drm_mm_node *node)
 131 {
 132         struct drm_mm *mm = hole_node->mm;
 133         struct rb_node **link, *rb;
 134         struct drm_mm_node *parent;
 135
 136         node->__subtree_last = LAST(node);
 137
 138         if (hole_node->allocated) {
 139                 rb = &hole_node->rb;
 140                 while (rb) {
 141                         parent = rb_entry(rb, struct drm_mm_node, rb);
 142                         if (parent->__subtree_last >= node->__subtree_last)
 143                                 break;
 144
 145                         parent->__subtree_last = node->__subtree_last;
 146                         rb = rb_parent(rb);
 147                 }
 148
 149                 rb = &hole_node->rb;
 150                 link = &hole_node->rb.rb_right;
 151         } else {
 152                 rb = NULL;
 153                 link = &mm->interval_tree.rb_node;
 154         }
 155
 156         while (*link) {
 157                 rb = *link;
 158                 parent = rb_entry(rb, struct drm_mm_node, rb);
 159                 if (parent->__subtree_last < node->__subtree_last)
 160                         parent->__subtree_last = node->__subtree_last;
 161                 if (node->start < parent->start)
 162                         link = &parent->rb.rb_left;
 163                 else
 164                         link = &parent->rb.rb_right;
 165         }
 166
 167         rb_link_node(&node->rb, rb, link);
 168         rb_insert_augmented(&node->rb,
 169                             &mm->interval_tree,
 170                             &drm_mm_interval_tree_augment);
 171 }
 172
 173 static void drm_mm_insert_helper(struct drm_mm_node *hole_node,
 174                                  struct drm_mm_node *node,
 175                                  u64 size, unsigned alignment,
 176                                  unsigned long color,
 177                                  enum drm_mm_allocator_flags flags)
 178 {
 179         struct drm_mm *mm = hole_node->mm;
 180         u64 hole_start = drm_mm_hole_node_start(hole_node);
 181         u64 hole_end = drm_mm_hole_node_end(hole_node);
 182         u64 adj_start = hole_start;
 183         u64 adj_end = hole_end;
 184
 185         BUG_ON(node->allocated);
 186
 187         if (mm->color_adjust)
 188                 mm->color_adjust(hole_node, color, &adj_start, &adj_end);
 189
 190         if (flags & DRM_MM_CREATE_TOP)
 191                 adj_start = adj_end - size;
 192
 193         if (alignment) {
 194                 u64 tmp = adj_start;
 195                 unsigned rem;
 196
 197                 rem = do_div(tmp, alignment);
 198                 if (rem) {
 199                         if (flags & DRM_MM_CREATE_TOP)
 200                                 adj_start -= rem;
 201                         else
 202                                 adj_start += alignment - rem;
 203                 }
 204         }
 205
 206         BUG_ON(adj_start < hole_start);
 207         BUG_ON(adj_end > hole_end);
 208
 209         if (adj_start == hole_start) {
 210                 hole_node->hole_follows = 0;
 211                 list_del(&hole_node->hole_stack);
 212         }
 213
 214         node->start = adj_start;
 215         node->size = size;
 216         node->mm = mm;
 217         node->color = color;
 218         node->allocated = 1;
 219
 220         list_add(&node->node_list, &hole_node->node_list);
 221
 222         drm_mm_interval_tree_add_node(hole_node, node);
 223
 224         BUG_ON(node->start + node->size > adj_end);
 225
 226         node->hole_follows = 0;
 227         if (__drm_mm_hole_node_start(node) < hole_end) {
 228                 list_add(&node->hole_stack, &mm->hole_stack);
 229                 node->hole_follows = 1;
 230         }
 231 }
 232
 233 /**
 234  * drm_mm_reserve_node - insert an pre-initialized node
 235  * @mm: drm_mm allocator to insert @node into
 236  * @node: drm_mm_node to insert
 237  *
 238  * This functions inserts an already set-up drm_mm_node into the allocator,
 239  * meaning that start, size and color must be set by the caller. This is useful
 240  * to initialize the allocator with preallocated objects which must be set-up
 241  * before the range allocator can be set-up, e.g. when taking over a firmware
 242  * framebuffer.
 243  *
 244  * Returns:
 245  * 0 on success, -ENOSPC if there's no hole where @node is.
 246  */
 247 int drm_mm_reserve_node(struct drm_mm *mm, struct drm_mm_node *node)
 248 {
 249         u64 end = node->start + node->size;
 250         struct drm_mm_node *hole;
 251         u64 hole_start, hole_end;
 252
 253         if (WARN_ON(node->size == 0))
 254                 return -EINVAL;
 255
 256         end = node->start + node->size;
 257
 258         /* Find the relevant hole to add our node to */
 259         hole = drm_mm_interval_tree_iter_first(&mm->interval_tree,
 260                                                node->start, ~(u64)0);
 261         if (hole) {
 262                 if (hole->start < end)
 263                         return -ENOSPC;
 264         } else {
 265                 hole = list_entry(&mm->head_node.node_list,
 266                                   typeof(*hole), node_list);
 267         }
 268
 269         hole = list_last_entry(&hole->node_list, typeof(*hole), node_list);
 270         if (!hole->hole_follows)
 271                 return -ENOSPC;
 272
 273         hole_start = __drm_mm_hole_node_start(hole);
 274         hole_end = __drm_mm_hole_node_end(hole);
 275         if (hole_start > node->start || hole_end < end)
 276                 return -ENOSPC;
 277
 278         node->mm = mm;
 279         node->allocated = 1;
 280
 281         list_add(&node->node_list, &hole->node_list);
 282
 283         drm_mm_interval_tree_add_node(hole, node);
 284
 285         if (node->start == hole_start) {
 286                 hole->hole_follows = 0;
 287                 list_del(&hole->hole_stack);
 288         }
 289
 290         node->hole_follows = 0;
 291         if (end != hole_end) {
 292                 list_add(&node->hole_stack, &mm->hole_stack);
 293                 node->hole_follows = 1;
 294         }
 295
 296         return 0;
 297 }
 298 EXPORT_SYMBOL(drm_mm_reserve_node);
 299
 300 /**
 301  * drm_mm_insert_node_generic - search for space and insert @node
 302  * @mm: drm_mm to allocate from
 303  * @node: preallocate node to insert
 304  * @size: size of the allocation
 305  * @alignment: alignment of the allocation
 306  * @color: opaque tag value to use for this node
 307  * @sflags: flags to fine-tune the allocation search
 308  * @aflags: flags to fine-tune the allocation behavior
 309  *
 310  * The preallocated node must be cleared to 0.
 311  *
 312  * Returns:
 313  * 0 on success, -ENOSPC if there's no suitable hole.
 314  */
 315 int drm_mm_insert_node_generic(struct drm_mm *mm, struct drm_mm_node *node,
 316                                u64 size, unsigned alignment,
 317                                unsigned long color,
 318                                enum drm_mm_search_flags sflags,
 319                                enum drm_mm_allocator_flags aflags)
 320 {
 321         struct drm_mm_node *hole_node;
 322
 323         if (WARN_ON(size == 0))
 324                 return -EINVAL;
 325
 326         hole_node = drm_mm_search_free_generic(mm, size, alignment,
 327                                                color, sflags);
 328         if (!hole_node)
 329                 return -ENOSPC;
 330
 331         drm_mm_insert_helper(hole_node, node, size, alignment, color, aflags);
 332         return 0;
 333 }
 334 EXPORT_SYMBOL(drm_mm_insert_node_generic);
 335
 336 static void drm_mm_insert_helper_range(struct drm_mm_node *hole_node,
 337                                        struct drm_mm_node *node,
 338                                        u64 size, unsigned alignment,
 339                                        unsigned long color,
 340                                        u64 start, u64 end,
 341                                        enum drm_mm_allocator_flags flags)
 342 {
 343         struct drm_mm *mm = hole_node->mm;
 344         u64 hole_start = drm_mm_hole_node_start(hole_node);
 345         u64 hole_end = drm_mm_hole_node_end(hole_node);
 346         u64 adj_start = hole_start;
 347         u64 adj_end = hole_end;
 348
 349         BUG_ON(!hole_node->hole_follows || node->allocated);
 350
 351         if (adj_start < start)
 352                 adj_start = start;
 353         if (adj_end > end)
 354                 adj_end = end;
 355
 356         if (mm->color_adjust)
 357                 mm->color_adjust(hole_node, color, &adj_start, &adj_end);
 358
 359         if (flags & DRM_MM_CREATE_TOP)
 360                 adj_start = adj_end - size;
 361
 362         if (alignment) {
 363                 u64 tmp = adj_start;
 364                 unsigned rem;
 365
 366                 rem = do_div(tmp, alignment);
 367                 if (rem) {
 368                         if (flags & DRM_MM_CREATE_TOP)
 369                                 adj_start -= rem;
 370                         else
 371                                 adj_start += alignment - rem;
 372                 }
 373         }
 374
 375         if (adj_start == hole_start) {
 376                 hole_node->hole_follows = 0;
 377                 list_del(&hole_node->hole_stack);
 378         }
 379
 380         node->start = adj_start;
 381         node->size = size;
 382         node->mm = mm;
 383         node->color = color;
 384         node->allocated = 1;
 385
 386         list_add(&node->node_list, &hole_node->node_list);
 387
 388         drm_mm_interval_tree_add_node(hole_node, node);
 389
 390         BUG_ON(node->start < start);
 391         BUG_ON(node->start < adj_start);
 392         BUG_ON(node->start + node->size > adj_end);
 393         BUG_ON(node->start + node->size > end);
 394
 395         node->hole_follows = 0;
 396         if (__drm_mm_hole_node_start(node) < hole_end) {
 397                 list_add(&node->hole_stack, &mm->hole_stack);
 398                 node->hole_follows = 1;
 399         }
 400 }
 401
 402 /**
 403  * drm_mm_insert_node_in_range_generic - ranged search for space and insert @node
 404  * @mm: drm_mm to allocate from
 405  * @node: preallocate node to insert
 406  * @size: size of the allocation
 407  * @alignment: alignment of the allocation
 408  * @color: opaque tag value to use for this node
 409  * @start: start of the allowed range for this node
 410  * @end: end of the allowed range for this node
 411  * @sflags: flags to fine-tune the allocation search
 412  * @aflags: flags to fine-tune the allocation behavior
 413  *
 414  * The preallocated node must be cleared to 0.
 415  *
 416  * Returns:
 417  * 0 on success, -ENOSPC if there's no suitable hole.
 418  */
 419 int drm_mm_insert_node_in_range_generic(struct drm_mm *mm, struct drm_mm_node *node,
 420                                         u64 size, unsigned alignment,
 421                                         unsigned long color,
 422                                         u64 start, u64 end,
 423                                         enum drm_mm_search_flags sflags,
 424                                         enum drm_mm_allocator_flags aflags)
 425 {
 426         struct drm_mm_node *hole_node;
 427
 428         if (WARN_ON(size == 0))
 429                 return -EINVAL;
 430
 431         hole_node = drm_mm_search_free_in_range_generic(mm,
 432                                                         size, alignment, color,
 433                                                         start, end, sflags);
 434         if (!hole_node)
 435                 return -ENOSPC;
 436
 437         drm_mm_insert_helper_range(hole_node, node,
 438                                    size, alignment, color,
 439                                    start, end, aflags);
 440         return 0;
 441 }
 442 EXPORT_SYMBOL(drm_mm_insert_node_in_range_generic);
 443
 444 /**
 445  * drm_mm_remove_node - Remove a memory node from the allocator.
 446  * @node: drm_mm_node to remove
 447  *
 448  * This just removes a node from its drm_mm allocator. The node does not need to
 449  * be cleared again before it can be re-inserted into this or any other drm_mm
 450  * allocator. It is a bug to call this function on a un-allocated node.
 451  */
 452 void drm_mm_remove_node(struct drm_mm_node *node)
 453 {
 454         struct drm_mm *mm = node->mm;
 455         struct drm_mm_node *prev_node;
 456
 457         if (WARN_ON(!node->allocated))
 458                 return;
 459
 460         BUG_ON(node->scanned_block || node->scanned_prev_free
 461                                    || node->scanned_next_free);
 462
 463         prev_node =
 464             list_entry(node->node_list.prev, struct drm_mm_node, node_list);
 465
 466         if (node->hole_follows) {
 467                 BUG_ON(__drm_mm_hole_node_start(node) ==
 468                        __drm_mm_hole_node_end(node));
 469                 list_del(&node->hole_stack);
 470         } else
 471                 BUG_ON(__drm_mm_hole_node_start(node) !=
 472                        __drm_mm_hole_node_end(node));
 473
 474
 475         if (!prev_node->hole_follows) {
 476                 prev_node->hole_follows = 1;
 477                 list_add(&prev_node->hole_stack, &mm->hole_stack);
 478         } else
 479                 list_move(&prev_node->hole_stack, &mm->hole_stack);
 480
 481         drm_mm_interval_tree_remove(node, &mm->interval_tree);
 482         list_del(&node->node_list);
 483         node->allocated = 0;
 484 }
 485 EXPORT_SYMBOL(drm_mm_remove_node);
 486
 487 static int check_free_hole(u64 start, u64 end, u64 size, unsigned alignment)
 488 {
 489         if (end - start < size)
 490                 return 0;
 491
 492         if (alignment) {
 493                 u64 tmp = start;
 494                 unsigned rem;
 495
 496                 rem = do_div(tmp, alignment);
 497                 if (rem)
 498                         start += alignment - rem;
 499         }
 500
 501         return end >= start + size;
 502 }
 503
 504 static struct drm_mm_node *drm_mm_search_free_generic(const struct drm_mm *mm,
 505                                                       u64 size,
 506                                                       unsigned alignment,
 507                                                       unsigned long color,
 508                                                       enum drm_mm_search_flags flags)
 509 {
 510         struct drm_mm_node *entry;
 511         struct drm_mm_node *best;
 512         u64 adj_start;
 513         u64 adj_end;
 514         u64 best_size;
 515
 516         BUG_ON(mm->scanned_blocks);
 517
 518         best = NULL;
 519         best_size = ~0UL;
 520
 521         __drm_mm_for_each_hole(entry, mm, adj_start, adj_end,
 522                                flags & DRM_MM_SEARCH_BELOW) {
 523                 u64 hole_size = adj_end - adj_start;
 524
 525                 if (mm->color_adjust) {
 526                         mm->color_adjust(entry, color, &adj_start, &adj_end);
 527                         if (adj_end <= adj_start)
 528                                 continue;
 529                 }
 530
 531                 if (!check_free_hole(adj_start, adj_end, size, alignment))
 532                         continue;
 533
 534                 if (!(flags & DRM_MM_SEARCH_BEST))
 535                         return entry;
 536
 537                 if (hole_size < best_size) {
 538                         best = entry;
 539                         best_size = hole_size;
 540                 }
 541         }
 542
 543         return best;
 544 }
 545
 546 static struct drm_mm_node *drm_mm_search_free_in_range_generic(const struct drm_mm *mm,
 547                                                         u64 size,
 548                                                         unsigned alignment,
 549                                                         unsigned long color,
 550                                                         u64 start,
 551                                                         u64 end,
 552                                                         enum drm_mm_search_flags flags)
 553 {
 554         struct drm_mm_node *entry;
 555         struct drm_mm_node *best;
 556         u64 adj_start;
 557         u64 adj_end;
 558         u64 best_size;
 559
 560         BUG_ON(mm->scanned_blocks);
 561
 562         best = NULL;
 563         best_size = ~0UL;
 564
 565         __drm_mm_for_each_hole(entry, mm, adj_start, adj_end,
 566                                flags & DRM_MM_SEARCH_BELOW) {
 567                 u64 hole_size = adj_end - adj_start;
 568
 569                 if (adj_start < start)
 570                         adj_start = start;
 571                 if (adj_end > end)
 572                         adj_end = end;
 573
 574                 if (mm->color_adjust) {
 575                         mm->color_adjust(entry, color, &adj_start, &adj_end);
 576                         if (adj_end <= adj_start)
 577                                 continue;
 578                 }
 579
 580                 if (!check_free_hole(adj_start, adj_end, size, alignment))
 581                         continue;
 582
 583                 if (!(flags & DRM_MM_SEARCH_BEST))
 584                         return entry;
 585
 586                 if (hole_size < best_size) {
 587                         best = entry;
 588                         best_size = hole_size;
 589                 }
 590         }
 591
 592         return best;
 593 }
 594
 595 /**
 596  * drm_mm_replace_node - move an allocation from @old to @new
 597  * @old: drm_mm_node to remove from the allocator
 598  * @new: drm_mm_node which should inherit @old's allocation
 599  *
 600  * This is useful for when drivers embed the drm_mm_node structure and hence
 601  * can't move allocations by reassigning pointers. It's a combination of remove
 602  * and insert with the guarantee that the allocation start will match.
 603  */
 604 void drm_mm_replace_node(struct drm_mm_node *old, struct drm_mm_node *new)
 605 {
 606         list_replace(&old->node_list, &new->node_list);
 607         list_replace(&old->hole_stack, &new->hole_stack);
 608         rb_replace_node(&old->rb, &new->rb, &old->mm->interval_tree);
 609         new->hole_follows = old->hole_follows;
 610         new->mm = old->mm;
 611         new->start = old->start;
 612         new->size = old->size;
 613         new->color = old->color;
 614         new->__subtree_last = old->__subtree_last;
 615
 616         old->allocated = 0;
 617         new->allocated = 1;
 618 }
 619 EXPORT_SYMBOL(drm_mm_replace_node);
 620
 621 /**
 622  * DOC: lru scan roaster
 623  *
 624  * Very often GPUs need to have continuous allocations for a given object. When
 625  * evicting objects to make space for a new one it is therefore not most
 626  * efficient when we simply start to select all objects from the tail of an LRU
 627  * until there's a suitable hole: Especially for big objects or nodes that
 628  * otherwise have special allocation constraints there's a good chance we evict
 629  * lots of (smaller) objects unecessarily.
 630  *
 631  * The DRM range allocator supports this use-case through the scanning
 632  * interfaces. First a scan operation needs to be initialized with
 633  * drm_mm_init_scan() or drm_mm_init_scan_with_range(). The the driver adds
 634  * objects to the roaster (probably by walking an LRU list, but this can be
 635  * freely implemented) until a suitable hole is found or there's no further
 636  * evitable object.
 637  *
 638  * The the driver must walk through all objects again in exactly the reverse
 639  * order to restore the allocator state. Note that while the allocator is used
 640  * in the scan mode no other operation is allowed.
 641  *
 642  * Finally the driver evicts all objects selected in the scan. Adding and
 643  * removing an object is O(1), and since freeing a node is also O(1) the overall
 644  * complexity is O(scanned_objects). So like the free stack which needs to be
 645  * walked before a scan operation even begins this is linear in the number of
 646  * objects. It doesn't seem to hurt badly.
 647  */
 648
 649 /**
 650  * drm_mm_init_scan - initialize lru scanning
 651  * @mm: drm_mm to scan
 652  * @size: size of the allocation
 653  * @alignment: alignment of the allocation
 654  * @color: opaque tag value to use for the allocation
 655  *
 656  * This simply sets up the scanning routines with the parameters for the desired
 657  * hole. Note that there's no need to specify allocation flags, since they only
 658  * change the place a node is allocated from within a suitable hole.
 659  *
 660  * Warning:
 661  * As long as the scan list is non-empty, no other operations than
 662  * adding/removing nodes to/from the scan list are allowed.
 663  */
 664 void drm_mm_init_scan(struct drm_mm *mm,
 665                       u64 size,
 666                       unsigned alignment,
 667                       unsigned long color)
 668 {
 669         mm->scan_color = color;
 670         mm->scan_alignment = alignment;
 671         mm->scan_size = size;
 672         mm->scanned_blocks = 0;
 673         mm->scan_hit_start = 0;
 674         mm->scan_hit_end = 0;
 675         mm->scan_check_range = 0;
 676         mm->prev_scanned_node = NULL;
 677 }
 678 EXPORT_SYMBOL(drm_mm_init_scan);
 679
 680 /**
 681  * drm_mm_init_scan - initialize range-restricted lru scanning
 682  * @mm: drm_mm to scan
 683  * @size: size of the allocation
 684  * @alignment: alignment of the allocation
 685  * @color: opaque tag value to use for the allocation
 686  * @start: start of the allowed range for the allocation
 687  * @end: end of the allowed range for the allocation
 688  *
 689  * This simply sets up the scanning routines with the parameters for the desired
 690  * hole. Note that there's no need to specify allocation flags, since they only
 691  * change the place a node is allocated from within a suitable hole.
 692  *
 693  * Warning:
 694  * As long as the scan list is non-empty, no other operations than
 695  * adding/removing nodes to/from the scan list are allowed.
 696  */
 697 void drm_mm_init_scan_with_range(struct drm_mm *mm,
 698                                  u64 size,
 699                                  unsigned alignment,
 700                                  unsigned long color,
 701                                  u64 start,
 702                                  u64 end)
 703 {
 704         mm->scan_color = color;
 705         mm->scan_alignment = alignment;
 706         mm->scan_size = size;
 707         mm->scanned_blocks = 0;
 708         mm->scan_hit_start = 0;
 709         mm->scan_hit_end = 0;
 710         mm->scan_start = start;
 711         mm->scan_end = end;
 712         mm->scan_check_range = 1;
 713         mm->prev_scanned_node = NULL;
 714 }
 715 EXPORT_SYMBOL(drm_mm_init_scan_with_range);
 716
 717 /**
 718  * drm_mm_scan_add_block - add a node to the scan list
 719  * @node: drm_mm_node to add
 720  *
 721  * Add a node to the scan list that might be freed to make space for the desired
 722  * hole.
 723  *
 724  * Returns:
 725  * True if a hole has been found, false otherwise.
 726  */
 727 bool drm_mm_scan_add_block(struct drm_mm_node *node)
 728 {
 729         struct drm_mm *mm = node->mm;
 730         struct drm_mm_node *prev_node;
 731         u64 hole_start, hole_end;
 732         u64 adj_start, adj_end;
 733
 734         mm->scanned_blocks++;
 735
 736         BUG_ON(node->scanned_block);
 737         node->scanned_block = 1;
 738
 739         prev_node = list_entry(node->node_list.prev, struct drm_mm_node,
 740                                node_list);
 741
 742         node->scanned_preceeds_hole = prev_node->hole_follows;
 743         prev_node->hole_follows = 1;
 744         list_del(&node->node_list);
 745         node->node_list.prev = &prev_node->node_list;
 746         node->node_list.next = &mm->prev_scanned_node->node_list;
 747         mm->prev_scanned_node = node;
 748
 749         adj_start = hole_start = drm_mm_hole_node_start(prev_node);
 750         adj_end = hole_end = drm_mm_hole_node_end(prev_node);
 751
 752         if (mm->scan_check_range) {
 753                 if (adj_start < mm->scan_start)
 754                         adj_start = mm->scan_start;
 755                 if (adj_end > mm->scan_end)
 756                         adj_end = mm->scan_end;
 757         }
 758
 759         if (mm->color_adjust)
 760                 mm->color_adjust(prev_node, mm->scan_color,
 761                                  &adj_start, &adj_end);
 762
 763         if (check_free_hole(adj_start, adj_end,
 764                             mm->scan_size, mm->scan_alignment)) {
 765                 mm->scan_hit_start = hole_start;
 766                 mm->scan_hit_end = hole_end;
 767                 return true;
 768         }
 769
 770         return false;
 771 }
 772 EXPORT_SYMBOL(drm_mm_scan_add_block);
 773
 774 /**
 775  * drm_mm_scan_remove_block - remove a node from the scan list
 776  * @node: drm_mm_node to remove
 777  *
 778  * Nodes _must_ be removed in the exact same order from the scan list as they
 779  * have been added, otherwise the internal state of the memory manager will be
 780  * corrupted.
 781  *
 782  * When the scan list is empty, the selected memory nodes can be freed. An
 783  * immediately following drm_mm_search_free with !DRM_MM_SEARCH_BEST will then
 784  * return the just freed block (because its at the top of the free_stack list).
 785  *
 786  * Returns:
 787  * True if this block should be evicted, false otherwise. Will always
 788  * return false when no hole has been found.
 789  */
 790 bool drm_mm_scan_remove_block(struct drm_mm_node *node)
 791 {
 792         struct drm_mm *mm = node->mm;
 793         struct drm_mm_node *prev_node;
 794
 795         mm->scanned_blocks--;
 796
 797         BUG_ON(!node->scanned_block);
 798         node->scanned_block = 0;
 799
 800         prev_node = list_entry(node->node_list.prev, struct drm_mm_node,
 801                                node_list);
 802
 803         prev_node->hole_follows = node->scanned_preceeds_hole;
 804         list_add(&node->node_list, &prev_node->node_list);
 805
 806          return (drm_mm_hole_node_end(node) > mm->scan_hit_start &&
 807                  node->start < mm->scan_hit_end);
 808 }
 809 EXPORT_SYMBOL(drm_mm_scan_remove_block);
 810
 811 /**
 812  * drm_mm_clean - checks whether an allocator is clean
 813  * @mm: drm_mm allocator to check
 814  *
 815  * Returns:
 816  * True if the allocator is completely free, false if there's still a node
 817  * allocated in it.
 818  */
 819 bool drm_mm_clean(struct drm_mm * mm)
 820 {
 821         struct list_head *head = &mm->head_node.node_list;
 822
 823         return (head->next->next == head);
 824 }
 825 EXPORT_SYMBOL(drm_mm_clean);
 826
 827 /**
 828  * drm_mm_init - initialize a drm-mm allocator
 829  * @mm: the drm_mm structure to initialize
 830  * @start: start of the range managed by @mm
 831  * @size: end of the range managed by @mm
 832  *
 833  * Note that @mm must be cleared to 0 before calling this function.
 834  */
 835 void drm_mm_init(struct drm_mm * mm, u64 start, u64 size)
 836 {
 837         INIT_LIST_HEAD(&mm->hole_stack);
 838         mm->scanned_blocks = 0;
 839
 840         /* Clever trick to avoid a special case in the free hole tracking. */
 841         INIT_LIST_HEAD(&mm->head_node.node_list);
 842         mm->head_node.hole_follows = 1;
 843         mm->head_node.scanned_block = 0;
 844         mm->head_node.scanned_prev_free = 0;
 845         mm->head_node.scanned_next_free = 0;
 846         mm->head_node.mm = mm;
 847         mm->head_node.start = start + size;
 848         mm->head_node.size = start - mm->head_node.start;
 849         list_add_tail(&mm->head_node.hole_stack, &mm->hole_stack);
 850
 851         mm->interval_tree = RB_ROOT;
 852
 853         mm->color_adjust = NULL;
 854 }
 855 EXPORT_SYMBOL(drm_mm_init);
 856
 857 /**
 858  * drm_mm_takedown - clean up a drm_mm allocator
 859  * @mm: drm_mm allocator to clean up
 860  *
 861  * Note that it is a bug to call this function on an allocator which is not
 862  * clean.
 863  */
 864 void drm_mm_takedown(struct drm_mm * mm)
 865 {
 866         WARN(!list_empty(&mm->head_node.node_list),
 867              "Memory manager not clean during takedown.\n");
 868 }
 869 EXPORT_SYMBOL(drm_mm_takedown);
 870
 871 static u64 drm_mm_debug_hole(struct drm_mm_node *entry,
 872                                      const char *prefix)
 873 {
 874         u64 hole_start, hole_end, hole_size;
 875
 876         if (entry->hole_follows) {
 877                 hole_start = drm_mm_hole_node_start(entry);
 878                 hole_end = drm_mm_hole_node_end(entry);
 879                 hole_size = hole_end - hole_start;
 880                 pr_debug("%s %#llx-%#llx: %llu: free\n", prefix, hole_start,
 881                          hole_end, hole_size);
 882                 return hole_size;
 883         }
 884
 885         return 0;
 886 }
 887
 888 /**
 889  * drm_mm_debug_table - dump allocator state to dmesg
 890  * @mm: drm_mm allocator to dump
 891  * @prefix: prefix to use for dumping to dmesg
 892  */
 893 void drm_mm_debug_table(struct drm_mm *mm, const char *prefix)
 894 {
 895         struct drm_mm_node *entry;
 896         u64 total_used = 0, total_free = 0, total = 0;
 897
 898         total_free += drm_mm_debug_hole(&mm->head_node, prefix);
 899
 900         drm_mm_for_each_node(entry, mm) {
 901                 pr_debug("%s %#llx-%#llx: %llu: used\n", prefix, entry->start,
 902                          entry->start + entry->size, entry->size);
 903                 total_used += entry->size;
 904                 total_free += drm_mm_debug_hole(entry, prefix);
 905         }
 906         total = total_free + total_used;
 907
 908         pr_debug("%s total: %llu, used %llu free %llu\n", prefix, total,
 909                  total_used, total_free);
 910 }
 911 EXPORT_SYMBOL(drm_mm_debug_table);
 912
 913 #if defined(CONFIG_DEBUG_FS)
 914 static u64 drm_mm_dump_hole(struct seq_file *m, struct drm_mm_node *entry)
 915 {
 916         u64 hole_start, hole_end, hole_size;
 917
 918         if (entry->hole_follows) {
 919                 hole_start = drm_mm_hole_node_start(entry);
 920                 hole_end = drm_mm_hole_node_end(entry);
 921                 hole_size = hole_end - hole_start;
 922                 seq_printf(m, "%#018llx-%#018llx: %llu: free\n", hole_start,
 923                            hole_end, hole_size);
 924                 return hole_size;
 925         }
 926
 927         return 0;
 928 }
 929
 930 /**
 931  * drm_mm_dump_table - dump allocator state to a seq_file
 932  * @m: seq_file to dump to
 933  * @mm: drm_mm allocator to dump
 934  */
 935 int drm_mm_dump_table(struct seq_file *m, struct drm_mm *mm)
 936 {
 937         struct drm_mm_node *entry;
 938         u64 total_used = 0, total_free = 0, total = 0;
 939
 940         total_free += drm_mm_dump_hole(m, &mm->head_node);
 941
 942         drm_mm_for_each_node(entry, mm) {
 943                 seq_printf(m, "%#018llx-%#018llx: %llu: used\n", entry->start,
 944                            entry->start + entry->size, entry->size);
 945                 total_used += entry->size;
 946                 total_free += drm_mm_dump_hole(m, entry);
 947         }
 948         total = total_free + total_used;
 949
 950         seq_printf(m, "total: %llu, used %llu free %llu\n", total,
 951                    total_used, total_free);
 952         return 0;
 953 }
 954 EXPORT_SYMBOL(drm_mm_dump_table);
 955 #endif