sys/i386/i386/busdma_machdep.c

   1 /*
   2  * Copyright (c) 1997, 1998 Justin T. Gibbs.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions, and the following disclaimer,
  10  *    without modification, immediately at the beginning of the file.
  11  * 2. The name of the author may not be used to endorse or promote products
  12  *    derived from this software without specific prior written permission.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  17  * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
  18  * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  24  * SUCH DAMAGE.
  25  *
  26  *      $Id: busdma_machdep.c,v 1.10 1998/10/07 03:38:14 gibbs Exp $
  27  */
  28
  29 #include <sys/param.h>
  30 #include <sys/systm.h>
  31 #include <sys/malloc.h>
  32
  33 #include <vm/vm.h>
  34 #include <vm/vm_prot.h>
  35 #include <vm/vm_page.h>
  36
  37 #include <machine/bus.h>
  38 #include <machine/md_var.h>
  39
  40 #define MAX(a,b) (((a) > (b)) ? (a) : (b))
  41 #define MIN(a,b) (((a) < (b)) ? (a) : (b))
  42 #define MAX_BPAGES 128
  43
  44 struct bus_dma_tag {
  45         bus_dma_tag_t     parent;
  46         bus_size_t        alignment;
  47         bus_size_t        boundary;
  48         bus_addr_t        lowaddr;
  49         bus_addr_t        highaddr;
  50         bus_dma_filter_t *filter;
  51         void             *filterarg;
  52         bus_size_t        maxsize;
  53         u_int             nsegments;
  54         bus_size_t        maxsegsz;
  55         int               flags;
  56         int               ref_count;
  57         int               map_count;
  58 };
  59
  60 struct bounce_page {
  61         vm_offset_t     vaddr;          /* kva of bounce buffer */
  62         bus_addr_t      busaddr;        /* Physical address */
  63         vm_offset_t     datavaddr;      /* kva of client data */
  64         bus_size_t      datacount;      /* client data count */
  65         STAILQ_ENTRY(bounce_page) links;
  66 };
  67
  68 int busdma_swi_pending;
  69
  70 static STAILQ_HEAD(bp_list, bounce_page) bounce_page_list;
  71 static int free_bpages;
  72 static int reserved_bpages;
  73 static int active_bpages;
  74 static int total_bpages;
  75 static bus_addr_t bounce_lowaddr = BUS_SPACE_MAXADDR;
  76
  77 struct bus_dmamap {
  78         struct bp_list         bpages;
  79         int                    pagesneeded;
  80         int                    pagesreserved;
  81         bus_dma_tag_t          dmat;
  82         void                  *buf;             /* unmapped buffer pointer */
  83         bus_size_t             buflen;          /* unmapped buffer length */
  84         bus_dmamap_callback_t *callback;
  85         void                  *callback_arg;
  86         STAILQ_ENTRY(bus_dmamap) links;
  87 };
  88
  89 static STAILQ_HEAD(, bus_dmamap) bounce_map_waitinglist;
  90 static STAILQ_HEAD(, bus_dmamap) bounce_map_callbacklist;
  91 static struct bus_dmamap nobounce_dmamap;
  92
  93 static int alloc_bounce_pages(bus_dma_tag_t dmat, u_int numpages);
  94 static int reserve_bounce_pages(bus_dma_tag_t dmat, bus_dmamap_t map);
  95 static vm_offset_t add_bounce_page(bus_dma_tag_t dmat, bus_dmamap_t map,
  96                                    vm_offset_t vaddr, bus_size_t size);
  97 static void free_bounce_page(bus_dma_tag_t dmat, struct bounce_page *bpage);
  98 static __inline int run_filter(bus_dma_tag_t dmat, bus_addr_t paddr);
  99
 100 static __inline int
 101 run_filter(bus_dma_tag_t dmat, bus_addr_t paddr)
 102 {
 103         int retval;
 104
 105         retval = 0;
 106         do {
 107                 if (paddr > dmat->lowaddr
 108                  && paddr <= dmat->highaddr
 109                  && (dmat->filter == NULL
 110                   || (*dmat->filter)(dmat->filterarg, paddr) != 0))
 111                         retval = 1;
 112
 113                 dmat = dmat->parent;
 114         } while (retval == 0 && dmat != NULL);
 115         return (retval);
 116 }
 117
 118 #define BUS_DMA_MIN_ALLOC_COMP BUS_DMA_BUS4
 119 /*
 120  * Allocate a device specific dma_tag.
 121  */
 122 int
 123 bus_dma_tag_create(bus_dma_tag_t parent, bus_size_t alignment,
 124                    bus_size_t boundary, bus_addr_t lowaddr,
 125                    bus_addr_t highaddr, bus_dma_filter_t *filter,
 126                    void *filterarg, bus_size_t maxsize, int nsegments,
 127                    bus_size_t maxsegsz, int flags, bus_dma_tag_t *dmat)
 128 {
 129         bus_dma_tag_t newtag;
 130         int error = 0;
 131
 132         /* Return a NULL tag on failure */
 133         *dmat = NULL;
 134
 135         newtag = (bus_dma_tag_t)malloc(sizeof(*newtag), M_DEVBUF, M_NOWAIT);
 136         if (newtag == NULL)
 137                 return (ENOMEM);
 138
 139         newtag->parent = parent;
 140         newtag->boundary = boundary;
 141         newtag->lowaddr = trunc_page((vm_offset_t)lowaddr) + (PAGE_SIZE - 1);
 142         newtag->highaddr = trunc_page((vm_offset_t)highaddr) + (PAGE_SIZE - 1);
 143         newtag->filter = filter;
 144         newtag->filterarg = filterarg;
 145         newtag->maxsize = maxsize;
 146         newtag->nsegments = nsegments;
 147         newtag->maxsegsz = maxsegsz;
 148         newtag->flags = flags;
 149         newtag->ref_count = 1; /* Count ourself */
 150         newtag->map_count = 0;
 151
 152         /* Take into account any restrictions imposed by our parent tag */
 153         if (parent != NULL) {
 154                 newtag->lowaddr = MIN(parent->lowaddr, newtag->lowaddr);
 155                 newtag->highaddr = MAX(parent->highaddr, newtag->highaddr);
 156                 /*
 157                  * XXX Not really correct??? Probably need to honor boundary
 158                  *     all the way up the inheritence chain.
 159                  */
 160                 newtag->boundary = MAX(parent->boundary, newtag->boundary);
 161                 if (newtag->filter == NULL) {
 162                         /*
 163                          * Short circuit looking at our parent directly
 164                          * since we have encapsulated all of its information
 165                          */
 166                         newtag->filter = parent->filter;
 167                         newtag->filterarg = parent->filterarg;
 168                         newtag->parent = parent->parent;
 169                 }
 170                 if (newtag->parent != NULL) {
 171                         parent->ref_count++;
 172                 }
 173         }
 174
 175         if (newtag->lowaddr < ptoa(Maxmem) && (flags & BUS_DMA_ALLOCNOW) != 0) {
 176                 /* Must bounce */
 177
 178                 if (lowaddr > bounce_lowaddr) {
 179                         /*
 180                          * Go through the pool and kill any pages
 181                          * that don't reside below lowaddr.
 182                          */
 183                         panic("bus_dma_tag_create: page reallocation "
 184                               "not implemented");
 185                 }
 186                 if (ptoa(total_bpages) < maxsize) {
 187                         int pages;
 188
 189                         pages = atop(maxsize) - total_bpages;
 190
 191                         /* Add pages to our bounce pool */
 192                         if (alloc_bounce_pages(newtag, pages) < pages)
 193                                 error = ENOMEM;
 194                 }
 195                 /* Performed initial allocation */
 196                 newtag->flags |= BUS_DMA_MIN_ALLOC_COMP;
 197         }
 198
 199         if (error != 0) {
 200                 free(newtag, M_DEVBUF);
 201         } else {
 202                 *dmat = newtag;
 203         }
 204         return (error);
 205 }
 206
 207 int
 208 bus_dma_tag_destroy(bus_dma_tag_t dmat)
 209 {
 210         if (dmat != NULL) {
 211
 212                 if (dmat->map_count != 0)
 213                         return (EBUSY);
 214
 215                 while (dmat != NULL) {
 216                         bus_dma_tag_t parent;
 217
 218                         parent = dmat->parent;
 219                         dmat->ref_count--;
 220                         if (dmat->ref_count == 0) {
 221                                 free(dmat, M_DEVBUF);
 222                                 /*
 223                                  * Last reference count, so
 224                                  * release our reference
 225                                  * count on our parent.
 226                                  */
 227                                 dmat = parent;
 228                         } else
 229                                 dmat = NULL;
 230                 }
 231         }
 232         return (0);
 233 }
 234
 235 /*
 236  * Allocate a handle for mapping from kva/uva/physical
 237  * address space into bus device space.
 238  */
 239 int
 240 bus_dmamap_create(bus_dma_tag_t dmat, int flags, bus_dmamap_t *mapp)
 241 {
 242         int error;
 243
 244         error = 0;
 245
 246         if (dmat->lowaddr < ptoa(Maxmem)) {
 247                 /* Must bounce */
 248                 int maxpages;
 249
 250                 *mapp = (bus_dmamap_t)malloc(sizeof(**mapp), M_DEVBUF,
 251                                              M_NOWAIT);
 252                 if (*mapp == NULL) {
 253                         return (ENOMEM);
 254                 } else {
 255                         /* Initialize the new map */
 256                         bzero(*mapp, sizeof(**mapp));
 257                         STAILQ_INIT(&((*mapp)->bpages));
 258                 }
 259                 /*
 260                  * Attempt to add pages to our pool on a per-instance
 261                  * basis up to a sane limit.
 262                  */
 263                 maxpages = MIN(MAX_BPAGES, Maxmem - atop(dmat->lowaddr));
 264                 if ((dmat->flags & BUS_DMA_MIN_ALLOC_COMP) == 0
 265                  || (dmat->map_count > 0
 266                   && total_bpages < maxpages)) {
 267                         int pages;
 268
 269                         if (dmat->lowaddr > bounce_lowaddr) {
 270                                 /*
 271                                  * Go through the pool and kill any pages
 272                                  * that don't reside below lowaddr.
 273                                  */
 274                                 panic("bus_dmamap_create: page reallocation "
 275                                       "not implemented");
 276                         }
 277                         pages = atop(dmat->maxsize);
 278                         pages = MIN(maxpages - total_bpages, pages);
 279                         error = alloc_bounce_pages(dmat, pages);
 280
 281                         if ((dmat->flags & BUS_DMA_MIN_ALLOC_COMP) == 0) {
 282                                 if (error == 0)
 283                                         dmat->flags |= BUS_DMA_MIN_ALLOC_COMP;
 284                         } else {
 285                                 error = 0;
 286                         }
 287                 }
 288         } else {
 289                 *mapp = NULL;
 290         }
 291         if (error == 0)
 292                 dmat->map_count++;
 293         return (error);
 294 }
 295
 296 /*
 297  * Destroy a handle for mapping from kva/uva/physical
 298  * address space into bus device space.
 299  */
 300 int
 301 bus_dmamap_destroy(bus_dma_tag_t dmat, bus_dmamap_t map)
 302 {
 303         if (map != NULL) {
 304                 if (STAILQ_FIRST(&map->bpages) != NULL)
 305                         return (EBUSY);
 306                 free(map, M_DEVBUF);
 307         }
 308         dmat->map_count--;
 309         return (0);
 310 }
 311
 312
 313 /*
 314  * Allocate a piece of memory that can be efficiently mapped into
 315  * bus device space based on the constraints lited in the dma tag.
 316  * A dmamap to for use with dmamap_load is also allocated.
 317  */
 318 int
 319 bus_dmamem_alloc(bus_dma_tag_t dmat, void** vaddr, int flags,
 320                  bus_dmamap_t *mapp)
 321 {
 322         /* If we succeed, no mapping/bouncing will be required */
 323         *mapp = NULL;
 324
 325         if ((dmat->maxsize <= PAGE_SIZE) && dmat->lowaddr >= ptoa(Maxmem)) {
 326                 *vaddr = malloc(dmat->maxsize, M_DEVBUF,
 327                                 (flags & BUS_DMA_NOWAIT) ? M_NOWAIT : M_WAITOK);
 328         } else {
 329                 /*
 330                  * XXX Use Contigmalloc until it is merged into this facility
 331                  *     and handles multi-seg allocations.  Nobody is doing
 332                  *     multi-seg allocations yet though.
 333                  */
 334                 *vaddr = contigmalloc(dmat->maxsize, M_DEVBUF,
 335                                       (flags & BUS_DMA_NOWAIT)
 336                                       ? M_NOWAIT : M_WAITOK,
 337                                       0ul, dmat->lowaddr, 1ul, dmat->boundary);
 338         }
 339         if (*vaddr == NULL)
 340                 return (ENOMEM);
 341         return (0);
 342 }
 343
 344 /*
 345  * Free a piece of memory and it's allociated dmamap, that was allocated
 346  * via bus_dmamem_alloc.
 347  */
 348 void
 349 bus_dmamem_free(bus_dma_tag_t dmat, void *vaddr, bus_dmamap_t map)
 350 {
 351         /*
 352          * dmamem does not need to be bounced, so the map should be
 353          * NULL
 354          */
 355         if (map != &nobounce_dmamap)
 356                 panic("bus_dmamem_free: Invalid map freed\n");
 357         /* XXX There is no "contigfree" and "free" doesn't work */
 358         if ((dmat->maxsize <= PAGE_SIZE) && dmat->lowaddr >= ptoa(Maxmem))
 359                 free(vaddr, M_DEVBUF);
 360 }
 361
 362 #define BUS_DMAMAP_NSEGS ((BUS_SPACE_MAXSIZE / PAGE_SIZE) + 1)
 363
 364 /*
 365  * Map the buffer buf into bus space using the dmamap map.
 366  */
 367 int
 368 bus_dmamap_load(bus_dma_tag_t dmat, bus_dmamap_t map, void *buf,
 369                 bus_size_t buflen, bus_dmamap_callback_t *callback,
 370                 void *callback_arg, int flags)
 371 {
 372         vm_offset_t             vaddr;
 373         vm_offset_t             paddr;
 374 #ifdef __GNUC__
 375         bus_dma_segment_t       dm_segments[dmat->nsegments];
 376 #else
 377         bus_dma_segment_t       dm_segments[BUS_DMAMAP_NSEGS];
 378 #endif
 379         bus_dma_segment_t      *sg;
 380         int                     seg;
 381         int                     error;
 382
 383         if (map == NULL)
 384                 map = &nobounce_dmamap;
 385
 386         error = 0;
 387         /*
 388          * If we are being called during a callback, pagesneeded will
 389          * be non-zero, so we can avoid doing the work twice.
 390          */
 391         if (dmat->lowaddr < ptoa(Maxmem) && map->pagesneeded == 0) {
 392                 vm_offset_t     vendaddr;
 393
 394                 /*
 395                  * Count the number of bounce pages
 396                  * needed in order to complete this transfer
 397                  */
 398                 vaddr = trunc_page((vm_offset_t)buf);
 399                 vendaddr = (vm_offset_t)buf + buflen;
 400
 401                 while (vaddr < vendaddr) {
 402                         paddr = pmap_kextract(vaddr);
 403                         if (run_filter(dmat, paddr) != 0) {
 404
 405                                 map->pagesneeded++;
 406                         }
 407                         vaddr += PAGE_SIZE;
 408                 }
 409         }
 410
 411         /* Reserve Necessary Bounce Pages */
 412         if (map->pagesneeded != 0) {
 413                 int s;
 414
 415                 s = splhigh();
 416                 if (reserve_bounce_pages(dmat, map) != 0) {
 417
 418                         /* Queue us for resources */
 419                         map->dmat = dmat;
 420                         map->buf = buf;
 421                         map->buflen = buflen;
 422                         map->callback = callback;
 423                         map->callback_arg = callback_arg;
 424
 425                         STAILQ_INSERT_TAIL(&bounce_map_waitinglist, map, links);
 426                         splx(s);
 427
 428                         return (EINPROGRESS);
 429                 }
 430                 splx(s);
 431         }
 432
 433         vaddr = (vm_offset_t)buf;
 434         sg = &dm_segments[0];
 435         seg = 1;
 436         sg->ds_len = 0;
 437
 438         do {
 439                 bus_size_t      size;
 440                 vm_offset_t     nextpaddr;      /* GCC warning expected */
 441
 442                 paddr = pmap_kextract(vaddr);
 443                 size = PAGE_SIZE - (paddr & PAGE_MASK);
 444                 if (size > buflen)
 445                         size = buflen;
 446
 447                 if (map->pagesneeded != 0
 448                  && run_filter(dmat, paddr)) {
 449                         paddr = add_bounce_page(dmat, map, vaddr, size);
 450                 }
 451
 452                 if (sg->ds_len == 0) {
 453                         sg->ds_addr = paddr;
 454                         sg->ds_len = size;
 455                 } else if (paddr == nextpaddr) {
 456                         sg->ds_len += size;
 457                 } else {
 458                         /* Go to the next segment */
 459                         sg++;
 460                         seg++;
 461                         if (seg > dmat->nsegments)
 462                                 break;
 463                         sg->ds_addr = paddr;
 464                         sg->ds_len = size;
 465                 }
 466                 vaddr += size;
 467                 nextpaddr = paddr + size;
 468                 buflen -= size;
 469         } while (buflen > 0);
 470
 471         if (buflen != 0) {
 472                 printf("bus_dmamap_load: Too many segs! buf_len = 0x%lx\n",
 473                        (u_long)buflen);
 474                 error = EFBIG;
 475         }
 476
 477         (*callback)(callback_arg, dm_segments, seg, error);
 478
 479         return (0);
 480 }
 481
 482 /*
 483  * Release the mapping held by map.
 484  */
 485 void
 486 _bus_dmamap_unload(bus_dma_tag_t dmat, bus_dmamap_t map)
 487 {
 488         struct bounce_page *bpage;
 489
 490         while ((bpage = STAILQ_FIRST(&map->bpages)) != NULL) {
 491                 STAILQ_REMOVE_HEAD(&map->bpages, links);
 492                 free_bounce_page(dmat, bpage);
 493         }
 494 }
 495
 496 void
 497 _bus_dmamap_sync(bus_dma_tag_t dmat, bus_dmamap_t map, bus_dmasync_op_t op)
 498 {
 499         struct bounce_page *bpage;
 500
 501         if ((bpage = STAILQ_FIRST(&map->bpages)) != NULL) {
 502
 503                 /*
 504                  * Handle data bouncing.  We might also
 505                  * want to add support for invalidating
 506                  * the caches on broken hardware
 507                  */
 508                 switch (op) {
 509                 case BUS_DMASYNC_PREWRITE:
 510                         while (bpage != NULL) {
 511                                 bcopy((void *)bpage->datavaddr,
 512                                       (void *)bpage->vaddr,
 513                                       bpage->datacount);
 514                                 bpage = STAILQ_NEXT(bpage, links);
 515                         }
 516                         break;
 517
 518                 case BUS_DMASYNC_POSTREAD:
 519                         while (bpage != NULL) {
 520                                 bcopy((void *)bpage->vaddr,
 521                                       (void *)bpage->datavaddr,
 522                                       bpage->datacount);
 523                                 bpage = STAILQ_NEXT(bpage, links);
 524                         }
 525                         break;
 526                 case BUS_DMASYNC_PREREAD:
 527                 case BUS_DMASYNC_POSTWRITE:
 528                         /* No-ops */
 529                         break;
 530                 }
 531         }
 532 }
 533
 534 static int
 535 alloc_bounce_pages(bus_dma_tag_t dmat, u_int numpages)
 536 {
 537         int count;
 538
 539         count = 0;
 540         if (total_bpages == 0) {
 541                 STAILQ_INIT(&bounce_page_list);
 542                 STAILQ_INIT(&bounce_map_waitinglist);
 543                 STAILQ_INIT(&bounce_map_callbacklist);
 544         }
 545
 546         while (numpages > 0) {
 547                 struct bounce_page *bpage;
 548                 int s;
 549
 550                 bpage = (struct bounce_page *)malloc(sizeof(*bpage), M_DEVBUF,
 551                                                      M_NOWAIT);
 552
 553                 if (bpage == NULL)
 554                         break;
 555                 bzero(bpage, sizeof(*bpage));
 556                 bpage->vaddr = (vm_offset_t)contigmalloc(PAGE_SIZE, M_DEVBUF,
 557                                                          M_NOWAIT, 0ul,
 558                                                          dmat->lowaddr,
 559                                                          PAGE_SIZE,
 560                                                          0);
 561                 if (bpage->vaddr == NULL) {
 562                         free(bpage, M_DEVBUF);
 563                         break;
 564                 }
 565                 bpage->busaddr = pmap_kextract(bpage->vaddr);
 566                 s = splhigh();
 567                 STAILQ_INSERT_TAIL(&bounce_page_list, bpage, links);
 568                 total_bpages++;
 569                 free_bpages++;
 570                 splx(s);
 571                 count++;
 572                 numpages--;
 573         }
 574         return (count);
 575 }
 576
 577 static int
 578 reserve_bounce_pages(bus_dma_tag_t dmat, bus_dmamap_t map)
 579 {
 580         int pages;
 581
 582         pages = MIN(free_bpages, map->pagesneeded - map->pagesreserved);
 583         free_bpages -= pages;
 584         reserved_bpages += pages;
 585         map->pagesreserved += pages;
 586         pages = map->pagesneeded - map->pagesreserved;
 587
 588         return (pages);
 589 }
 590
 591 static vm_offset_t
 592 add_bounce_page(bus_dma_tag_t dmat, bus_dmamap_t map, vm_offset_t vaddr,
 593                 bus_size_t size)
 594 {
 595         int s;
 596         struct bounce_page *bpage;
 597
 598         if (map->pagesneeded == 0)
 599                 panic("add_bounce_page: map doesn't need any pages");
 600         map->pagesneeded--;
 601
 602         if (map->pagesreserved == 0)
 603                 panic("add_bounce_page: map doesn't need any pages");
 604         map->pagesreserved--;
 605
 606         s = splhigh();
 607         bpage = STAILQ_FIRST(&bounce_page_list);
 608         if (bpage == NULL)
 609                 panic("add_bounce_page: free page list is empty");
 610
 611         STAILQ_REMOVE_HEAD(&bounce_page_list, links);
 612         reserved_bpages--;
 613         active_bpages++;
 614         splx(s);
 615
 616         bpage->datavaddr = vaddr;
 617         bpage->datacount = size;
 618         STAILQ_INSERT_TAIL(&(map->bpages), bpage, links);
 619         return (bpage->busaddr);
 620 }
 621
 622 static void
 623 free_bounce_page(bus_dma_tag_t dmat, struct bounce_page *bpage)
 624 {
 625         int s;
 626         struct bus_dmamap *map;
 627
 628         bpage->datavaddr = 0;
 629         bpage->datacount = 0;
 630
 631         s = splhigh();
 632         STAILQ_INSERT_HEAD(&bounce_page_list, bpage, links);
 633         free_bpages++;
 634         active_bpages--;
 635         if ((map = STAILQ_FIRST(&bounce_map_waitinglist)) != NULL) {
 636                 if (reserve_bounce_pages(map->dmat, map) == 0) {
 637                         STAILQ_REMOVE_HEAD(&bounce_map_waitinglist, links);
 638                         STAILQ_INSERT_TAIL(&bounce_map_callbacklist,
 639                                            map, links);
 640                         busdma_swi_pending = 1;
 641                         setsoftvm();
 642                 }
 643         }
 644         splx(s);
 645 }
 646
 647 void
 648 busdma_swi()
 649 {
 650         int s;
 651         struct bus_dmamap *map;
 652
 653         s = splhigh();
 654         while ((map = STAILQ_FIRST(&bounce_map_callbacklist)) != NULL) {
 655                 STAILQ_REMOVE_HEAD(&bounce_map_callbacklist, links);
 656                 splx(s);
 657                 bus_dmamap_load(map->dmat, map, map->buf, map->buflen,
 658                                 map->callback, map->callback_arg, /*flags*/0);
 659                 s = splhigh();
 660         }
 661         splx(s);
 662 }