arch/tile/kernel/pci-dma.c

   1 /*
   2  * Copyright 2010 Tilera Corporation. All Rights Reserved.
   3  *
   4  *   This program is free software; you can redistribute it and/or
   5  *   modify it under the terms of the GNU General Public License
   6  *   as published by the Free Software Foundation, version 2.
   7  *
   8  *   This program is distributed in the hope that it will be useful, but
   9  *   WITHOUT ANY WARRANTY; without even the implied warranty of
  10  *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
  11  *   NON INFRINGEMENT.  See the GNU General Public License for
  12  *   more details.
  13  */
  14
  15 #include <linux/mm.h>
  16 #include <linux/dma-mapping.h>
  17 #include <linux/swiotlb.h>
  18 #include <linux/vmalloc.h>
  19 #include <linux/export.h>
  20 #include <asm/tlbflush.h>
  21 #include <asm/homecache.h>
  22
  23 /* Generic DMA mapping functions: */
  24
  25 /*
  26  * Allocate what Linux calls "coherent" memory.  On TILEPro this is
  27  * uncached memory; on TILE-Gx it is hash-for-home memory.
  28  */
  29 #ifdef __tilepro__
  30 #define PAGE_HOME_DMA PAGE_HOME_UNCACHED
  31 #else
  32 #define PAGE_HOME_DMA PAGE_HOME_HASH
  33 #endif
  34
  35 static void *tile_dma_alloc_coherent(struct device *dev, size_t size,
  36                                      dma_addr_t *dma_handle, gfp_t gfp,
  37                                      struct dma_attrs *attrs)
  38 {
  39         u64 dma_mask = (dev && dev->coherent_dma_mask) ?
  40                 dev->coherent_dma_mask : DMA_BIT_MASK(32);
  41         int node = dev ? dev_to_node(dev) : 0;
  42         int order = get_order(size);
  43         struct page *pg;
  44         dma_addr_t addr;
  45
  46         gfp |= __GFP_ZERO;
  47
  48         /*
  49          * If the mask specifies that the memory be in the first 4 GB, then
  50          * we force the allocation to come from the DMA zone.  We also
  51          * force the node to 0 since that's the only node where the DMA
  52          * zone isn't empty.  If the mask size is smaller than 32 bits, we
  53          * may still not be able to guarantee a suitable memory address, in
  54          * which case we will return NULL.  But such devices are uncommon.
  55          */
  56         if (dma_mask <= DMA_BIT_MASK(32)) {
  57                 gfp |= GFP_DMA;
  58                 node = 0;
  59         }
  60
  61         pg = homecache_alloc_pages_node(node, gfp, order, PAGE_HOME_DMA);
  62         if (pg == NULL)
  63                 return NULL;
  64
  65         addr = page_to_phys(pg);
  66         if (addr + size > dma_mask) {
  67                 __homecache_free_pages(pg, order);
  68                 return NULL;
  69         }
  70
  71         *dma_handle = addr;
  72
  73         return page_address(pg);
  74 }
  75
  76 /*
  77  * Free memory that was allocated with tile_dma_alloc_coherent.
  78  */
  79 static void tile_dma_free_coherent(struct device *dev, size_t size,
  80                                    void *vaddr, dma_addr_t dma_handle,
  81                                    struct dma_attrs *attrs)
  82 {
  83         homecache_free_pages((unsigned long)vaddr, get_order(size));
  84 }
  85
  86 /*
  87  * The map routines "map" the specified address range for DMA
  88  * accesses.  The memory belongs to the device after this call is
  89  * issued, until it is unmapped with dma_unmap_single.
  90  *
  91  * We don't need to do any mapping, we just flush the address range
  92  * out of the cache and return a DMA address.
  93  *
  94  * The unmap routines do whatever is necessary before the processor
  95  * accesses the memory again, and must be called before the driver
  96  * touches the memory.  We can get away with a cache invalidate if we
  97  * can count on nothing having been touched.
  98  */
  99
 100 /* Set up a single page for DMA access. */
 101 static void __dma_prep_page(struct page *page, unsigned long offset,
 102                             size_t size, enum dma_data_direction direction)
 103 {
 104         /*
 105          * Flush the page from cache if necessary.
 106          * On tilegx, data is delivered to hash-for-home L3; on tilepro,
 107          * data is delivered direct to memory.
 108          *
 109          * NOTE: If we were just doing DMA_TO_DEVICE we could optimize
 110          * this to be a "flush" not a "finv" and keep some of the
 111          * state in cache across the DMA operation, but it doesn't seem
 112          * worth creating the necessary flush_buffer_xxx() infrastructure.
 113          */
 114         int home = page_home(page);
 115         switch (home) {
 116         case PAGE_HOME_HASH:
 117 #ifdef __tilegx__
 118                 return;
 119 #endif
 120                 break;
 121         case PAGE_HOME_UNCACHED:
 122 #ifdef __tilepro__
 123                 return;
 124 #endif
 125                 break;
 126         case PAGE_HOME_IMMUTABLE:
 127                 /* Should be going to the device only. */
 128                 BUG_ON(direction == DMA_FROM_DEVICE ||
 129                        direction == DMA_BIDIRECTIONAL);
 130                 return;
 131         case PAGE_HOME_INCOHERENT:
 132                 /* Incoherent anyway, so no need to work hard here. */
 133                 return;
 134         default:
 135                 BUG_ON(home < 0 || home >= NR_CPUS);
 136                 break;
 137         }
 138         homecache_finv_page(page);
 139
 140 #ifdef DEBUG_ALIGNMENT
 141         /* Warn if the region isn't cacheline aligned. */
 142         if (offset & (L2_CACHE_BYTES - 1) || (size & (L2_CACHE_BYTES - 1)))
 143                 pr_warn("Unaligned DMA to non-hfh memory: PA %#llx/%#lx\n",
 144                         PFN_PHYS(page_to_pfn(page)) + offset, size);
 145 #endif
 146 }
 147
 148 /* Make the page ready to be read by the core. */
 149 static void __dma_complete_page(struct page *page, unsigned long offset,
 150                                 size_t size, enum dma_data_direction direction)
 151 {
 152 #ifdef __tilegx__
 153         switch (page_home(page)) {
 154         case PAGE_HOME_HASH:
 155                 /* I/O device delivered data the way the cpu wanted it. */
 156                 break;
 157         case PAGE_HOME_INCOHERENT:
 158                 /* Incoherent anyway, so no need to work hard here. */
 159                 break;
 160         case PAGE_HOME_IMMUTABLE:
 161                 /* Extra read-only copies are not a problem. */
 162                 break;
 163         default:
 164                 /* Flush the bogus hash-for-home I/O entries to memory. */
 165                 homecache_finv_map_page(page, PAGE_HOME_HASH);
 166                 break;
 167         }
 168 #endif
 169 }
 170
 171 static void __dma_prep_pa_range(dma_addr_t dma_addr, size_t size,
 172                                 enum dma_data_direction direction)
 173 {
 174         struct page *page = pfn_to_page(PFN_DOWN(dma_addr));
 175         unsigned long offset = dma_addr & (PAGE_SIZE - 1);
 176         size_t bytes = min(size, (size_t)(PAGE_SIZE - offset));
 177
 178         while (size != 0) {
 179                 __dma_prep_page(page, offset, bytes, direction);
 180                 size -= bytes;
 181                 ++page;
 182                 offset = 0;
 183                 bytes = min((size_t)PAGE_SIZE, size);
 184         }
 185 }
 186
 187 static void __dma_complete_pa_range(dma_addr_t dma_addr, size_t size,
 188                                     enum dma_data_direction direction)
 189 {
 190         struct page *page = pfn_to_page(PFN_DOWN(dma_addr));
 191         unsigned long offset = dma_addr & (PAGE_SIZE - 1);
 192         size_t bytes = min(size, (size_t)(PAGE_SIZE - offset));
 193
 194         while (size != 0) {
 195                 __dma_complete_page(page, offset, bytes, direction);
 196                 size -= bytes;
 197                 ++page;
 198                 offset = 0;
 199                 bytes = min((size_t)PAGE_SIZE, size);
 200         }
 201 }
 202
 203 static int tile_dma_map_sg(struct device *dev, struct scatterlist *sglist,
 204                            int nents, enum dma_data_direction direction,
 205                            struct dma_attrs *attrs)
 206 {
 207         struct scatterlist *sg;
 208         int i;
 209
 210         BUG_ON(!valid_dma_direction(direction));
 211
 212         WARN_ON(nents == 0 || sglist->length == 0);
 213
 214         for_each_sg(sglist, sg, nents, i) {
 215                 sg->dma_address = sg_phys(sg);
 216                 __dma_prep_pa_range(sg->dma_address, sg->length, direction);
 217 #ifdef CONFIG_NEED_SG_DMA_LENGTH
 218                 sg->dma_length = sg->length;
 219 #endif
 220         }
 221
 222         return nents;
 223 }
 224
 225 static void tile_dma_unmap_sg(struct device *dev, struct scatterlist *sglist,
 226                               int nents, enum dma_data_direction direction,
 227                               struct dma_attrs *attrs)
 228 {
 229         struct scatterlist *sg;
 230         int i;
 231
 232         BUG_ON(!valid_dma_direction(direction));
 233         for_each_sg(sglist, sg, nents, i) {
 234                 sg->dma_address = sg_phys(sg);
 235                 __dma_complete_pa_range(sg->dma_address, sg->length,
 236                                         direction);
 237         }
 238 }
 239
 240 static dma_addr_t tile_dma_map_page(struct device *dev, struct page *page,
 241                                     unsigned long offset, size_t size,
 242                                     enum dma_data_direction direction,
 243                                     struct dma_attrs *attrs)
 244 {
 245         BUG_ON(!valid_dma_direction(direction));
 246
 247         BUG_ON(offset + size > PAGE_SIZE);
 248         __dma_prep_page(page, offset, size, direction);
 249
 250         return page_to_pa(page) + offset;
 251 }
 252
 253 static void tile_dma_unmap_page(struct device *dev, dma_addr_t dma_address,
 254                                 size_t size, enum dma_data_direction direction,
 255                                 struct dma_attrs *attrs)
 256 {
 257         BUG_ON(!valid_dma_direction(direction));
 258
 259         __dma_complete_page(pfn_to_page(PFN_DOWN(dma_address)),
 260                             dma_address & (PAGE_SIZE - 1), size, direction);
 261 }
 262
 263 static void tile_dma_sync_single_for_cpu(struct device *dev,
 264                                          dma_addr_t dma_handle,
 265                                          size_t size,
 266                                          enum dma_data_direction direction)
 267 {
 268         BUG_ON(!valid_dma_direction(direction));
 269
 270         __dma_complete_pa_range(dma_handle, size, direction);
 271 }
 272
 273 static void tile_dma_sync_single_for_device(struct device *dev,
 274                                             dma_addr_t dma_handle, size_t size,
 275                                             enum dma_data_direction direction)
 276 {
 277         __dma_prep_pa_range(dma_handle, size, direction);
 278 }
 279
 280 static void tile_dma_sync_sg_for_cpu(struct device *dev,
 281                                      struct scatterlist *sglist, int nelems,
 282                                      enum dma_data_direction direction)
 283 {
 284         struct scatterlist *sg;
 285         int i;
 286
 287         BUG_ON(!valid_dma_direction(direction));
 288         WARN_ON(nelems == 0 || sglist->length == 0);
 289
 290         for_each_sg(sglist, sg, nelems, i) {
 291                 dma_sync_single_for_cpu(dev, sg->dma_address,
 292                                         sg_dma_len(sg), direction);
 293         }
 294 }
 295
 296 static void tile_dma_sync_sg_for_device(struct device *dev,
 297                                         struct scatterlist *sglist, int nelems,
 298                                         enum dma_data_direction direction)
 299 {
 300         struct scatterlist *sg;
 301         int i;
 302
 303         BUG_ON(!valid_dma_direction(direction));
 304         WARN_ON(nelems == 0 || sglist->length == 0);
 305
 306         for_each_sg(sglist, sg, nelems, i) {
 307                 dma_sync_single_for_device(dev, sg->dma_address,
 308                                            sg_dma_len(sg), direction);
 309         }
 310 }
 311
 312 static inline int
 313 tile_dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
 314 {
 315         return 0;
 316 }
 317
 318 static inline int
 319 tile_dma_supported(struct device *dev, u64 mask)
 320 {
 321         return 1;
 322 }
 323
 324 static struct dma_map_ops tile_default_dma_map_ops = {
 325         .alloc = tile_dma_alloc_coherent,
 326         .free = tile_dma_free_coherent,
 327         .map_page = tile_dma_map_page,
 328         .unmap_page = tile_dma_unmap_page,
 329         .map_sg = tile_dma_map_sg,
 330         .unmap_sg = tile_dma_unmap_sg,
 331         .sync_single_for_cpu = tile_dma_sync_single_for_cpu,
 332         .sync_single_for_device = tile_dma_sync_single_for_device,
 333         .sync_sg_for_cpu = tile_dma_sync_sg_for_cpu,
 334         .sync_sg_for_device = tile_dma_sync_sg_for_device,
 335         .mapping_error = tile_dma_mapping_error,
 336         .dma_supported = tile_dma_supported
 337 };
 338
 339 struct dma_map_ops *tile_dma_map_ops = &tile_default_dma_map_ops;
 340 EXPORT_SYMBOL(tile_dma_map_ops);
 341
 342 /* Generic PCI DMA mapping functions */
 343
 344 static void *tile_pci_dma_alloc_coherent(struct device *dev, size_t size,
 345                                          dma_addr_t *dma_handle, gfp_t gfp,
 346                                          struct dma_attrs *attrs)
 347 {
 348         int node = dev_to_node(dev);
 349         int order = get_order(size);
 350         struct page *pg;
 351         dma_addr_t addr;
 352
 353         gfp |= __GFP_ZERO;
 354
 355         pg = homecache_alloc_pages_node(node, gfp, order, PAGE_HOME_DMA);
 356         if (pg == NULL)
 357                 return NULL;
 358
 359         addr = page_to_phys(pg);
 360
 361         *dma_handle = addr + get_dma_offset(dev);
 362
 363         return page_address(pg);
 364 }
 365
 366 /*
 367  * Free memory that was allocated with tile_pci_dma_alloc_coherent.
 368  */
 369 static void tile_pci_dma_free_coherent(struct device *dev, size_t size,
 370                                        void *vaddr, dma_addr_t dma_handle,
 371                                        struct dma_attrs *attrs)
 372 {
 373         homecache_free_pages((unsigned long)vaddr, get_order(size));
 374 }
 375
 376 static int tile_pci_dma_map_sg(struct device *dev, struct scatterlist *sglist,
 377                                int nents, enum dma_data_direction direction,
 378                                struct dma_attrs *attrs)
 379 {
 380         struct scatterlist *sg;
 381         int i;
 382
 383         BUG_ON(!valid_dma_direction(direction));
 384
 385         WARN_ON(nents == 0 || sglist->length == 0);
 386
 387         for_each_sg(sglist, sg, nents, i) {
 388                 sg->dma_address = sg_phys(sg);
 389                 __dma_prep_pa_range(sg->dma_address, sg->length, direction);
 390
 391                 sg->dma_address = sg->dma_address + get_dma_offset(dev);
 392 #ifdef CONFIG_NEED_SG_DMA_LENGTH
 393                 sg->dma_length = sg->length;
 394 #endif
 395         }
 396
 397         return nents;
 398 }
 399
 400 static void tile_pci_dma_unmap_sg(struct device *dev,
 401                                   struct scatterlist *sglist, int nents,
 402                                   enum dma_data_direction direction,
 403                                   struct dma_attrs *attrs)
 404 {
 405         struct scatterlist *sg;
 406         int i;
 407
 408         BUG_ON(!valid_dma_direction(direction));
 409         for_each_sg(sglist, sg, nents, i) {
 410                 sg->dma_address = sg_phys(sg);
 411                 __dma_complete_pa_range(sg->dma_address, sg->length,
 412                                         direction);
 413         }
 414 }
 415
 416 static dma_addr_t tile_pci_dma_map_page(struct device *dev, struct page *page,
 417                                         unsigned long offset, size_t size,
 418                                         enum dma_data_direction direction,
 419                                         struct dma_attrs *attrs)
 420 {
 421         BUG_ON(!valid_dma_direction(direction));
 422
 423         BUG_ON(offset + size > PAGE_SIZE);
 424         __dma_prep_page(page, offset, size, direction);
 425
 426         return page_to_pa(page) + offset + get_dma_offset(dev);
 427 }
 428
 429 static void tile_pci_dma_unmap_page(struct device *dev, dma_addr_t dma_address,
 430                                     size_t size,
 431                                     enum dma_data_direction direction,
 432                                     struct dma_attrs *attrs)
 433 {
 434         BUG_ON(!valid_dma_direction(direction));
 435
 436         dma_address -= get_dma_offset(dev);
 437
 438         __dma_complete_page(pfn_to_page(PFN_DOWN(dma_address)),
 439                             dma_address & (PAGE_SIZE - 1), size, direction);
 440 }
 441
 442 static void tile_pci_dma_sync_single_for_cpu(struct device *dev,
 443                                              dma_addr_t dma_handle,
 444                                              size_t size,
 445                                              enum dma_data_direction direction)
 446 {
 447         BUG_ON(!valid_dma_direction(direction));
 448
 449         dma_handle -= get_dma_offset(dev);
 450
 451         __dma_complete_pa_range(dma_handle, size, direction);
 452 }
 453
 454 static void tile_pci_dma_sync_single_for_device(struct device *dev,
 455                                                 dma_addr_t dma_handle,
 456                                                 size_t size,
 457                                                 enum dma_data_direction
 458                                                 direction)
 459 {
 460         dma_handle -= get_dma_offset(dev);
 461
 462         __dma_prep_pa_range(dma_handle, size, direction);
 463 }
 464
 465 static void tile_pci_dma_sync_sg_for_cpu(struct device *dev,
 466                                          struct scatterlist *sglist,
 467                                          int nelems,
 468                                          enum dma_data_direction direction)
 469 {
 470         struct scatterlist *sg;
 471         int i;
 472
 473         BUG_ON(!valid_dma_direction(direction));
 474         WARN_ON(nelems == 0 || sglist->length == 0);
 475
 476         for_each_sg(sglist, sg, nelems, i) {
 477                 dma_sync_single_for_cpu(dev, sg->dma_address,
 478                                         sg_dma_len(sg), direction);
 479         }
 480 }
 481
 482 static void tile_pci_dma_sync_sg_for_device(struct device *dev,
 483                                             struct scatterlist *sglist,
 484                                             int nelems,
 485                                             enum dma_data_direction direction)
 486 {
 487         struct scatterlist *sg;
 488         int i;
 489
 490         BUG_ON(!valid_dma_direction(direction));
 491         WARN_ON(nelems == 0 || sglist->length == 0);
 492
 493         for_each_sg(sglist, sg, nelems, i) {
 494                 dma_sync_single_for_device(dev, sg->dma_address,
 495                                            sg_dma_len(sg), direction);
 496         }
 497 }
 498
 499 static inline int
 500 tile_pci_dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
 501 {
 502         return 0;
 503 }
 504
 505 static inline int
 506 tile_pci_dma_supported(struct device *dev, u64 mask)
 507 {
 508         return 1;
 509 }
 510
 511 static struct dma_map_ops tile_pci_default_dma_map_ops = {
 512         .alloc = tile_pci_dma_alloc_coherent,
 513         .free = tile_pci_dma_free_coherent,
 514         .map_page = tile_pci_dma_map_page,
 515         .unmap_page = tile_pci_dma_unmap_page,
 516         .map_sg = tile_pci_dma_map_sg,
 517         .unmap_sg = tile_pci_dma_unmap_sg,
 518         .sync_single_for_cpu = tile_pci_dma_sync_single_for_cpu,
 519         .sync_single_for_device = tile_pci_dma_sync_single_for_device,
 520         .sync_sg_for_cpu = tile_pci_dma_sync_sg_for_cpu,
 521         .sync_sg_for_device = tile_pci_dma_sync_sg_for_device,
 522         .mapping_error = tile_pci_dma_mapping_error,
 523         .dma_supported = tile_pci_dma_supported
 524 };
 525
 526 struct dma_map_ops *gx_pci_dma_map_ops = &tile_pci_default_dma_map_ops;
 527 EXPORT_SYMBOL(gx_pci_dma_map_ops);
 528
 529 /* PCI DMA mapping functions for legacy PCI devices */
 530
 531 #ifdef CONFIG_SWIOTLB
 532 static void *tile_swiotlb_alloc_coherent(struct device *dev, size_t size,
 533                                          dma_addr_t *dma_handle, gfp_t gfp,
 534                                          struct dma_attrs *attrs)
 535 {
 536         gfp |= GFP_DMA;
 537         return swiotlb_alloc_coherent(dev, size, dma_handle, gfp);
 538 }
 539
 540 static void tile_swiotlb_free_coherent(struct device *dev, size_t size,
 541                                        void *vaddr, dma_addr_t dma_addr,
 542                                        struct dma_attrs *attrs)
 543 {
 544         swiotlb_free_coherent(dev, size, vaddr, dma_addr);
 545 }
 546
 547 static struct dma_map_ops pci_swiotlb_dma_ops = {
 548         .alloc = tile_swiotlb_alloc_coherent,
 549         .free = tile_swiotlb_free_coherent,
 550         .map_page = swiotlb_map_page,
 551         .unmap_page = swiotlb_unmap_page,
 552         .map_sg = swiotlb_map_sg_attrs,
 553         .unmap_sg = swiotlb_unmap_sg_attrs,
 554         .sync_single_for_cpu = swiotlb_sync_single_for_cpu,
 555         .sync_single_for_device = swiotlb_sync_single_for_device,
 556         .sync_sg_for_cpu = swiotlb_sync_sg_for_cpu,
 557         .sync_sg_for_device = swiotlb_sync_sg_for_device,
 558         .dma_supported = swiotlb_dma_supported,
 559         .mapping_error = swiotlb_dma_mapping_error,
 560 };
 561
 562 static struct dma_map_ops pci_hybrid_dma_ops = {
 563         .alloc = tile_swiotlb_alloc_coherent,
 564         .free = tile_swiotlb_free_coherent,
 565         .map_page = tile_pci_dma_map_page,
 566         .unmap_page = tile_pci_dma_unmap_page,
 567         .map_sg = tile_pci_dma_map_sg,
 568         .unmap_sg = tile_pci_dma_unmap_sg,
 569         .sync_single_for_cpu = tile_pci_dma_sync_single_for_cpu,
 570         .sync_single_for_device = tile_pci_dma_sync_single_for_device,
 571         .sync_sg_for_cpu = tile_pci_dma_sync_sg_for_cpu,
 572         .sync_sg_for_device = tile_pci_dma_sync_sg_for_device,
 573         .mapping_error = tile_pci_dma_mapping_error,
 574         .dma_supported = tile_pci_dma_supported
 575 };
 576
 577 struct dma_map_ops *gx_legacy_pci_dma_map_ops = &pci_swiotlb_dma_ops;
 578 struct dma_map_ops *gx_hybrid_pci_dma_map_ops = &pci_hybrid_dma_ops;
 579 #else
 580 struct dma_map_ops *gx_legacy_pci_dma_map_ops;
 581 struct dma_map_ops *gx_hybrid_pci_dma_map_ops;
 582 #endif
 583 EXPORT_SYMBOL(gx_legacy_pci_dma_map_ops);
 584 EXPORT_SYMBOL(gx_hybrid_pci_dma_map_ops);
 585
 586 #ifdef CONFIG_ARCH_HAS_DMA_SET_COHERENT_MASK
 587 int dma_set_coherent_mask(struct device *dev, u64 mask)
 588 {
 589         struct dma_map_ops *dma_ops = get_dma_ops(dev);
 590
 591         /*
 592          * For PCI devices with 64-bit DMA addressing capability, promote
 593          * the dma_ops to full capability for both streams and consistent
 594          * memory access. For 32-bit capable devices, limit the consistent
 595          * memory DMA range to max_direct_dma_addr.
 596          */
 597         if (dma_ops == gx_pci_dma_map_ops ||
 598             dma_ops == gx_hybrid_pci_dma_map_ops ||
 599             dma_ops == gx_legacy_pci_dma_map_ops) {
 600                 if (mask == DMA_BIT_MASK(64))
 601                         set_dma_ops(dev, gx_pci_dma_map_ops);
 602                 else if (mask > dev->archdata.max_direct_dma_addr)
 603                         mask = dev->archdata.max_direct_dma_addr;
 604         }
 605
 606         if (!dma_supported(dev, mask))
 607                 return -EIO;
 608         dev->coherent_dma_mask = mask;
 609         return 0;
 610 }
 611 EXPORT_SYMBOL(dma_set_coherent_mask);
 612 #endif
 613
 614 #ifdef ARCH_HAS_DMA_GET_REQUIRED_MASK
 615 /*
 616  * The generic dma_get_required_mask() uses the highest physical address
 617  * (max_pfn) to provide the hint to the PCI drivers regarding 32-bit or
 618  * 64-bit DMA configuration. Since TILEGx has I/O TLB/MMU, allowing the
 619  * DMAs to use the full 64-bit PCI address space and not limited by
 620  * the physical memory space, we always let the PCI devices use
 621  * 64-bit DMA if they have that capability, by returning the 64-bit
 622  * DMA mask here. The device driver has the option to use 32-bit DMA if
 623  * the device is not capable of 64-bit DMA.
 624  */
 625 u64 dma_get_required_mask(struct device *dev)
 626 {
 627         return DMA_BIT_MASK(64);
 628 }
 629 EXPORT_SYMBOL_GPL(dma_get_required_mask);
 630 #endif