arch/arm/common/dmabounce.c

   1 /*
   2  *  arch/arm/common/dmabounce.c
   3  *
   4  *  Special dma_{map/unmap/dma_sync}_* routines for systems that have
   5  *  limited DMA windows. These functions utilize bounce buffers to
   6  *  copy data to/from buffers located outside the DMA region. This
   7  *  only works for systems in which DMA memory is at the bottom of
   8  *  RAM and the remainder of memory is at the top an the DMA memory
   9  *  can be marked as ZONE_DMA. Anything beyond that such as discontigous
  10  *  DMA windows will require custom implementations that reserve memory
  11  *  areas at early bootup.
  12  *
  13  *  Original version by Brad Parker (brad@heeltoe.com)
  14  *  Re-written by Christopher Hoover <ch@murgatroid.com>
  15  *  Made generic by Deepak Saxena <dsaxena@plexity.net>
  16  *
  17  *  Copyright (C) 2002 Hewlett Packard Company.
  18  *  Copyright (C) 2004 MontaVista Software, Inc.
  19  *
  20  *  This program is free software; you can redistribute it and/or
  21  *  modify it under the terms of the GNU General Public License
  22  *  version 2 as published by the Free Software Foundation.
  23  */
  24
  25 #include <linux/module.h>
  26 #include <linux/init.h>
  27 #include <linux/slab.h>
  28 #include <linux/device.h>
  29 #include <linux/dma-mapping.h>
  30 #include <linux/dmapool.h>
  31 #include <linux/list.h>
  32
  33 #include <asm/cacheflush.h>
  34
  35 #undef DEBUG
  36
  37 #undef STATS
  38 #ifdef STATS
  39 #define DO_STATS(X) do { X ; } while (0)
  40 #else
  41 #define DO_STATS(X) do { } while (0)
  42 #endif
  43
  44 /* ************************************************** */
  45
  46 struct safe_buffer {
  47         struct list_head node;
  48
  49         /* original request */
  50         void            *ptr;
  51         size_t          size;
  52         int             direction;
  53
  54         /* safe buffer info */
  55         struct dma_pool *pool;
  56         void            *safe;
  57         dma_addr_t      safe_dma_addr;
  58 };
  59
  60 struct dmabounce_device_info {
  61         struct list_head node;
  62
  63         struct device *dev;
  64         struct dma_pool *small_buffer_pool;
  65         struct dma_pool *large_buffer_pool;
  66         struct list_head safe_buffers;
  67         unsigned long small_buffer_size, large_buffer_size;
  68 #ifdef STATS
  69         unsigned long sbp_allocs;
  70         unsigned long lbp_allocs;
  71         unsigned long total_allocs;
  72         unsigned long map_op_count;
  73         unsigned long bounce_count;
  74 #endif
  75 };
  76
  77 static LIST_HEAD(dmabounce_devs);
  78
  79 #ifdef STATS
  80 static void print_alloc_stats(struct dmabounce_device_info *device_info)
  81 {
  82         printk(KERN_INFO
  83                 "%s: dmabounce: sbp: %lu, lbp: %lu, other: %lu, total: %lu\n",
  84                 device_info->dev->bus_id,
  85                 device_info->sbp_allocs, device_info->lbp_allocs,
  86                 device_info->total_allocs - device_info->sbp_allocs -
  87                         device_info->lbp_allocs,
  88                 device_info->total_allocs);
  89 }
  90 #endif
  91
  92 /* find the given device in the dmabounce device list */
  93 static inline struct dmabounce_device_info *
  94 find_dmabounce_dev(struct device *dev)
  95 {
  96         struct dmabounce_device_info *d;
  97
  98         list_for_each_entry(d, &dmabounce_devs, node)
  99                 if (d->dev == dev)
 100                         return d;
 101
 102         return NULL;
 103 }
 104
 105
 106 /* allocate a 'safe' buffer and keep track of it */
 107 static inline struct safe_buffer *
 108 alloc_safe_buffer(struct dmabounce_device_info *device_info, void *ptr,
 109                         size_t size, enum dma_data_direction dir)
 110 {
 111         struct safe_buffer *buf;
 112         struct dma_pool *pool;
 113         struct device *dev = device_info->dev;
 114         void *safe;
 115         dma_addr_t safe_dma_addr;
 116
 117         dev_dbg(dev, "%s(ptr=%p, size=%d, dir=%d)\n",
 118                 __func__, ptr, size, dir);
 119
 120         DO_STATS ( device_info->total_allocs++ );
 121
 122         buf = kmalloc(sizeof(struct safe_buffer), GFP_ATOMIC);
 123         if (buf == NULL) {
 124                 dev_warn(dev, "%s: kmalloc failed\n", __func__);
 125                 return NULL;
 126         }
 127
 128         if (size <= device_info->small_buffer_size) {
 129                 pool = device_info->small_buffer_pool;
 130                 safe = dma_pool_alloc(pool, GFP_ATOMIC, &safe_dma_addr);
 131
 132                 DO_STATS ( device_info->sbp_allocs++ );
 133         } else if (size <= device_info->large_buffer_size) {
 134                 pool = device_info->large_buffer_pool;
 135                 safe = dma_pool_alloc(pool, GFP_ATOMIC, &safe_dma_addr);
 136
 137                 DO_STATS ( device_info->lbp_allocs++ );
 138         } else {
 139                 pool = NULL;
 140                 safe = dma_alloc_coherent(dev, size, &safe_dma_addr, GFP_ATOMIC);
 141         }
 142
 143         if (safe == NULL) {
 144                 dev_warn(device_info->dev,
 145                         "%s: could not alloc dma memory (size=%d)\n",
 146                        __func__, size);
 147                 kfree(buf);
 148                 return NULL;
 149         }
 150
 151 #ifdef STATS
 152         if (device_info->total_allocs % 1000 == 0)
 153                 print_alloc_stats(device_info);
 154 #endif
 155
 156         buf->ptr = ptr;
 157         buf->size = size;
 158         buf->direction = dir;
 159         buf->pool = pool;
 160         buf->safe = safe;
 161         buf->safe_dma_addr = safe_dma_addr;
 162
 163         list_add(&buf->node, &device_info->safe_buffers);
 164
 165         return buf;
 166 }
 167
 168 /* determine if a buffer is from our "safe" pool */
 169 static inline struct safe_buffer *
 170 find_safe_buffer(struct dmabounce_device_info *device_info, dma_addr_t safe_dma_addr)
 171 {
 172         struct safe_buffer *b;
 173
 174         list_for_each_entry(b, &device_info->safe_buffers, node)
 175                 if (b->safe_dma_addr == safe_dma_addr)
 176                         return b;
 177
 178         return NULL;
 179 }
 180
 181 static inline void
 182 free_safe_buffer(struct dmabounce_device_info *device_info, struct safe_buffer *buf)
 183 {
 184         dev_dbg(device_info->dev, "%s(buf=%p)\n", __func__, buf);
 185
 186         list_del(&buf->node);
 187
 188         if (buf->pool)
 189                 dma_pool_free(buf->pool, buf->safe, buf->safe_dma_addr);
 190         else
 191                 dma_free_coherent(device_info->dev, buf->size, buf->safe,
 192                                     buf->safe_dma_addr);
 193
 194         kfree(buf);
 195 }
 196
 197 /* ************************************************** */
 198
 199 #ifdef STATS
 200
 201 static void print_map_stats(struct dmabounce_device_info *device_info)
 202 {
 203         printk(KERN_INFO
 204                 "%s: dmabounce: map_op_count=%lu, bounce_count=%lu\n",
 205                 device_info->dev->bus_id,
 206                 device_info->map_op_count, device_info->bounce_count);
 207 }
 208 #endif
 209
 210 static inline dma_addr_t
 211 map_single(struct device *dev, void *ptr, size_t size,
 212                 enum dma_data_direction dir)
 213 {
 214         struct dmabounce_device_info *device_info = find_dmabounce_dev(dev);
 215         dma_addr_t dma_addr;
 216         int needs_bounce = 0;
 217
 218         if (device_info)
 219                 DO_STATS ( device_info->map_op_count++ );
 220
 221         dma_addr = virt_to_dma(dev, ptr);
 222
 223         if (dev->dma_mask) {
 224                 unsigned long mask = *dev->dma_mask;
 225                 unsigned long limit;
 226
 227                 limit = (mask + 1) & ~mask;
 228                 if (limit && size > limit) {
 229                         dev_err(dev, "DMA mapping too big (requested %#x "
 230                                 "mask %#Lx)\n", size, *dev->dma_mask);
 231                         return ~0;
 232                 }
 233
 234                 /*
 235                  * Figure out if we need to bounce from the DMA mask.
 236                  */
 237                 needs_bounce = (dma_addr | (dma_addr + size - 1)) & ~mask;
 238         }
 239
 240         if (device_info && (needs_bounce || dma_needs_bounce(dev, dma_addr, size))) {
 241                 struct safe_buffer *buf;
 242
 243                 buf = alloc_safe_buffer(device_info, ptr, size, dir);
 244                 if (buf == 0) {
 245                         dev_err(dev, "%s: unable to map unsafe buffer %p!\n",
 246                                __func__, ptr);
 247                         return 0;
 248                 }
 249
 250                 dev_dbg(dev,
 251                         "%s: unsafe buffer %p (phy=%p) mapped to %p (phy=%p)\n",
 252                         __func__, buf->ptr, (void *) virt_to_dma(dev, buf->ptr),
 253                         buf->safe, (void *) buf->safe_dma_addr);
 254
 255                 if ((dir == DMA_TO_DEVICE) ||
 256                     (dir == DMA_BIDIRECTIONAL)) {
 257                         dev_dbg(dev, "%s: copy unsafe %p to safe %p, size %d\n",
 258                                 __func__, ptr, buf->safe, size);
 259                         memcpy(buf->safe, ptr, size);
 260                 }
 261                 consistent_sync(buf->safe, size, dir);
 262
 263                 dma_addr = buf->safe_dma_addr;
 264         } else {
 265                 consistent_sync(ptr, size, dir);
 266         }
 267
 268         return dma_addr;
 269 }
 270
 271 static inline void
 272 unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
 273                 enum dma_data_direction dir)
 274 {
 275         struct dmabounce_device_info *device_info = find_dmabounce_dev(dev);
 276         struct safe_buffer *buf = NULL;
 277
 278         /*
 279          * Trying to unmap an invalid mapping
 280          */
 281         if (dma_addr == ~0) {
 282                 dev_err(dev, "Trying to unmap invalid mapping\n");
 283                 return;
 284         }
 285
 286         if (device_info)
 287                 buf = find_safe_buffer(device_info, dma_addr);
 288
 289         if (buf) {
 290                 BUG_ON(buf->size != size);
 291
 292                 dev_dbg(dev,
 293                         "%s: unsafe buffer %p (phy=%p) mapped to %p (phy=%p)\n",
 294                         __func__, buf->ptr, (void *) virt_to_dma(dev, buf->ptr),
 295                         buf->safe, (void *) buf->safe_dma_addr);
 296
 297                 DO_STATS ( device_info->bounce_count++ );
 298
 299                 if (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL) {
 300                         unsigned long ptr;
 301
 302                         dev_dbg(dev,
 303                                 "%s: copy back safe %p to unsafe %p size %d\n",
 304                                 __func__, buf->safe, buf->ptr, size);
 305                         memcpy(buf->ptr, buf->safe, size);
 306
 307                         /*
 308                          * DMA buffers must have the same cache properties
 309                          * as if they were really used for DMA - which means
 310                          * data must be written back to RAM.  Note that
 311                          * we don't use dmac_flush_range() here for the
 312                          * bidirectional case because we know the cache
 313                          * lines will be coherent with the data written.
 314                          */
 315                         ptr = (unsigned long)buf->ptr;
 316                         dmac_clean_range(ptr, ptr + size);
 317                 }
 318                 free_safe_buffer(device_info, buf);
 319         }
 320 }
 321
 322 static inline void
 323 sync_single(struct device *dev, dma_addr_t dma_addr, size_t size,
 324                 enum dma_data_direction dir)
 325 {
 326         struct dmabounce_device_info *device_info = find_dmabounce_dev(dev);
 327         struct safe_buffer *buf = NULL;
 328
 329         if (device_info)
 330                 buf = find_safe_buffer(device_info, dma_addr);
 331
 332         if (buf) {
 333                 /*
 334                  * Both of these checks from original code need to be
 335                  * commented out b/c some drivers rely on the following:
 336                  *
 337                  * 1) Drivers may map a large chunk of memory into DMA space
 338                  *    but only sync a small portion of it. Good example is
 339                  *    allocating a large buffer, mapping it, and then
 340                  *    breaking it up into small descriptors. No point
 341                  *    in syncing the whole buffer if you only have to
 342                  *    touch one descriptor.
 343                  *
 344                  * 2) Buffers that are mapped as DMA_BIDIRECTIONAL are
 345                  *    usually only synced in one dir at a time.
 346                  *
 347                  * See drivers/net/eepro100.c for examples of both cases.
 348                  *
 349                  * -ds
 350                  *
 351                  * BUG_ON(buf->size != size);
 352                  * BUG_ON(buf->direction != dir);
 353                  */
 354
 355                 dev_dbg(dev,
 356                         "%s: unsafe buffer %p (phy=%p) mapped to %p (phy=%p)\n",
 357                         __func__, buf->ptr, (void *) virt_to_dma(dev, buf->ptr),
 358                         buf->safe, (void *) buf->safe_dma_addr);
 359
 360                 DO_STATS ( device_info->bounce_count++ );
 361
 362                 switch (dir) {
 363                 case DMA_FROM_DEVICE:
 364                         dev_dbg(dev,
 365                                 "%s: copy back safe %p to unsafe %p size %d\n",
 366                                 __func__, buf->safe, buf->ptr, size);
 367                         memcpy(buf->ptr, buf->safe, size);
 368                         break;
 369                 case DMA_TO_DEVICE:
 370                         dev_dbg(dev,
 371                                 "%s: copy out unsafe %p to safe %p, size %d\n",
 372                                 __func__,buf->ptr, buf->safe, size);
 373                         memcpy(buf->safe, buf->ptr, size);
 374                         break;
 375                 case DMA_BIDIRECTIONAL:
 376                         BUG();  /* is this allowed?  what does it mean? */
 377                 default:
 378                         BUG();
 379                 }
 380                 consistent_sync(buf->safe, size, dir);
 381         } else {
 382                 consistent_sync(dma_to_virt(dev, dma_addr), size, dir);
 383         }
 384 }
 385
 386 /* ************************************************** */
 387
 388 /*
 389  * see if a buffer address is in an 'unsafe' range.  if it is
 390  * allocate a 'safe' buffer and copy the unsafe buffer into it.
 391  * substitute the safe buffer for the unsafe one.
 392  * (basically move the buffer from an unsafe area to a safe one)
 393  */
 394 dma_addr_t
 395 dma_map_single(struct device *dev, void *ptr, size_t size,
 396                 enum dma_data_direction dir)
 397 {
 398         unsigned long flags;
 399         dma_addr_t dma_addr;
 400
 401         dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
 402                 __func__, ptr, size, dir);
 403
 404         BUG_ON(dir == DMA_NONE);
 405
 406         local_irq_save(flags);
 407
 408         dma_addr = map_single(dev, ptr, size, dir);
 409
 410         local_irq_restore(flags);
 411
 412         return dma_addr;
 413 }
 414
 415 /*
 416  * see if a mapped address was really a "safe" buffer and if so, copy
 417  * the data from the safe buffer back to the unsafe buffer and free up
 418  * the safe buffer.  (basically return things back to the way they
 419  * should be)
 420  */
 421
 422 void
 423 dma_unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
 424                         enum dma_data_direction dir)
 425 {
 426         unsigned long flags;
 427
 428         dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
 429                 __func__, (void *) dma_addr, size, dir);
 430
 431         BUG_ON(dir == DMA_NONE);
 432
 433         local_irq_save(flags);
 434
 435         unmap_single(dev, dma_addr, size, dir);
 436
 437         local_irq_restore(flags);
 438 }
 439
 440 int
 441 dma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
 442                 enum dma_data_direction dir)
 443 {
 444         unsigned long flags;
 445         int i;
 446
 447         dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
 448                 __func__, sg, nents, dir);
 449
 450         BUG_ON(dir == DMA_NONE);
 451
 452         local_irq_save(flags);
 453
 454         for (i = 0; i < nents; i++, sg++) {
 455                 struct page *page = sg->page;
 456                 unsigned int offset = sg->offset;
 457                 unsigned int length = sg->length;
 458                 void *ptr = page_address(page) + offset;
 459
 460                 sg->dma_address =
 461                         map_single(dev, ptr, length, dir);
 462         }
 463
 464         local_irq_restore(flags);
 465
 466         return nents;
 467 }
 468
 469 void
 470 dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
 471                 enum dma_data_direction dir)
 472 {
 473         unsigned long flags;
 474         int i;
 475
 476         dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
 477                 __func__, sg, nents, dir);
 478
 479         BUG_ON(dir == DMA_NONE);
 480
 481         local_irq_save(flags);
 482
 483         for (i = 0; i < nents; i++, sg++) {
 484                 dma_addr_t dma_addr = sg->dma_address;
 485                 unsigned int length = sg->length;
 486
 487                 unmap_single(dev, dma_addr, length, dir);
 488         }
 489
 490         local_irq_restore(flags);
 491 }
 492
 493 void
 494 dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_addr, size_t size,
 495                                 enum dma_data_direction dir)
 496 {
 497         unsigned long flags;
 498
 499         dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
 500                 __func__, (void *) dma_addr, size, dir);
 501
 502         local_irq_save(flags);
 503
 504         sync_single(dev, dma_addr, size, dir);
 505
 506         local_irq_restore(flags);
 507 }
 508
 509 void
 510 dma_sync_single_for_device(struct device *dev, dma_addr_t dma_addr, size_t size,
 511                                 enum dma_data_direction dir)
 512 {
 513         unsigned long flags;
 514
 515         dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
 516                 __func__, (void *) dma_addr, size, dir);
 517
 518         local_irq_save(flags);
 519
 520         sync_single(dev, dma_addr, size, dir);
 521
 522         local_irq_restore(flags);
 523 }
 524
 525 void
 526 dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg, int nents,
 527                         enum dma_data_direction dir)
 528 {
 529         unsigned long flags;
 530         int i;
 531
 532         dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
 533                 __func__, sg, nents, dir);
 534
 535         BUG_ON(dir == DMA_NONE);
 536
 537         local_irq_save(flags);
 538
 539         for (i = 0; i < nents; i++, sg++) {
 540                 dma_addr_t dma_addr = sg->dma_address;
 541                 unsigned int length = sg->length;
 542
 543                 sync_single(dev, dma_addr, length, dir);
 544         }
 545
 546         local_irq_restore(flags);
 547 }
 548
 549 void
 550 dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg, int nents,
 551                         enum dma_data_direction dir)
 552 {
 553         unsigned long flags;
 554         int i;
 555
 556         dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
 557                 __func__, sg, nents, dir);
 558
 559         BUG_ON(dir == DMA_NONE);
 560
 561         local_irq_save(flags);
 562
 563         for (i = 0; i < nents; i++, sg++) {
 564                 dma_addr_t dma_addr = sg->dma_address;
 565                 unsigned int length = sg->length;
 566
 567                 sync_single(dev, dma_addr, length, dir);
 568         }
 569
 570         local_irq_restore(flags);
 571 }
 572
 573 int
 574 dmabounce_register_dev(struct device *dev, unsigned long small_buffer_size,
 575                         unsigned long large_buffer_size)
 576 {
 577         struct dmabounce_device_info *device_info;
 578
 579         device_info = kmalloc(sizeof(struct dmabounce_device_info), GFP_ATOMIC);
 580         if (!device_info) {
 581                 printk(KERN_ERR
 582                         "Could not allocated dmabounce_device_info for %s",
 583                         dev->bus_id);
 584                 return -ENOMEM;
 585         }
 586
 587         device_info->small_buffer_pool =
 588                 dma_pool_create("small_dmabounce_pool",
 589                                 dev,
 590                                 small_buffer_size,
 591                                 0 /* byte alignment */,
 592                                 0 /* no page-crossing issues */);
 593         if (!device_info->small_buffer_pool) {
 594                 printk(KERN_ERR
 595                         "dmabounce: could not allocate small DMA pool for %s\n",
 596                         dev->bus_id);
 597                 kfree(device_info);
 598                 return -ENOMEM;
 599         }
 600
 601         if (large_buffer_size) {
 602                 device_info->large_buffer_pool =
 603                         dma_pool_create("large_dmabounce_pool",
 604                                         dev,
 605                                         large_buffer_size,
 606                                         0 /* byte alignment */,
 607                                         0 /* no page-crossing issues */);
 608                 if (!device_info->large_buffer_pool) {
 609                 printk(KERN_ERR
 610                         "dmabounce: could not allocate large DMA pool for %s\n",
 611                         dev->bus_id);
 612                         dma_pool_destroy(device_info->small_buffer_pool);
 613
 614                         return -ENOMEM;
 615                 }
 616         }
 617
 618         device_info->dev = dev;
 619         device_info->small_buffer_size = small_buffer_size;
 620         device_info->large_buffer_size = large_buffer_size;
 621         INIT_LIST_HEAD(&device_info->safe_buffers);
 622
 623 #ifdef STATS
 624         device_info->sbp_allocs = 0;
 625         device_info->lbp_allocs = 0;
 626         device_info->total_allocs = 0;
 627         device_info->map_op_count = 0;
 628         device_info->bounce_count = 0;
 629 #endif
 630
 631         list_add(&device_info->node, &dmabounce_devs);
 632
 633         printk(KERN_INFO "dmabounce: registered device %s on %s bus\n",
 634                 dev->bus_id, dev->bus->name);
 635
 636         return 0;
 637 }
 638
 639 void
 640 dmabounce_unregister_dev(struct device *dev)
 641 {
 642         struct dmabounce_device_info *device_info = find_dmabounce_dev(dev);
 643
 644         if (!device_info) {
 645                 printk(KERN_WARNING
 646                         "%s: Never registered with dmabounce but attempting" \
 647                         "to unregister!\n", dev->bus_id);
 648                 return;
 649         }
 650
 651         if (!list_empty(&device_info->safe_buffers)) {
 652                 printk(KERN_ERR
 653                         "%s: Removing from dmabounce with pending buffers!\n",
 654                         dev->bus_id);
 655                 BUG();
 656         }
 657
 658         if (device_info->small_buffer_pool)
 659                 dma_pool_destroy(device_info->small_buffer_pool);
 660         if (device_info->large_buffer_pool)
 661                 dma_pool_destroy(device_info->large_buffer_pool);
 662
 663 #ifdef STATS
 664         print_alloc_stats(device_info);
 665         print_map_stats(device_info);
 666 #endif
 667
 668         list_del(&device_info->node);
 669
 670         kfree(device_info);
 671
 672         printk(KERN_INFO "dmabounce: device %s on %s bus unregistered\n",
 673                 dev->bus_id, dev->bus->name);
 674 }
 675
 676
 677 EXPORT_SYMBOL(dma_map_single);
 678 EXPORT_SYMBOL(dma_unmap_single);
 679 EXPORT_SYMBOL(dma_map_sg);
 680 EXPORT_SYMBOL(dma_unmap_sg);
 681 EXPORT_SYMBOL(dma_sync_single);
 682 EXPORT_SYMBOL(dma_sync_sg);
 683 EXPORT_SYMBOL(dmabounce_register_dev);
 684 EXPORT_SYMBOL(dmabounce_unregister_dev);
 685
 686 MODULE_AUTHOR("Christopher Hoover <ch@hpl.hp.com>, Deepak Saxena <dsaxena@plexity.net>");
 687 MODULE_DESCRIPTION("Special dma_{map/unmap/dma_sync}_* routines for systems with limited DMA windows");
 688 MODULE_LICENSE("GPL");