drivers/usb/host/ohci-q.c

   1 // SPDX-License-Identifier: GPL-1.0+
   2 /*
   3  * OHCI HCD (Host Controller Driver) for USB.
   4  *
   5  * (C) Copyright 1999 Roman Weissgaerber <weissg@vienna.at>
   6  * (C) Copyright 2000-2002 David Brownell <dbrownell@users.sourceforge.net>
   7  *
   8  * This file is licenced under the GPL.
   9  */
  10
  11 #include <linux/irq.h>
  12 #include <linux/slab.h>
  13
  14 static void urb_free_priv (struct ohci_hcd *hc, urb_priv_t *urb_priv)
  15 {
  16         int             last = urb_priv->length - 1;
  17
  18         if (last >= 0) {
  19                 int             i;
  20                 struct td       *td;
  21
  22                 for (i = 0; i <= last; i++) {
  23                         td = urb_priv->td [i];
  24                         if (td)
  25                                 td_free (hc, td);
  26                 }
  27         }
  28
  29         list_del (&urb_priv->pending);
  30         kfree (urb_priv);
  31 }
  32
  33 /*-------------------------------------------------------------------------*/
  34
  35 /*
  36  * URB goes back to driver, and isn't reissued.
  37  * It's completely gone from HC data structures.
  38  * PRECONDITION:  ohci lock held, irqs blocked.
  39  */
  40 static void
  41 finish_urb(struct ohci_hcd *ohci, struct urb *urb, int status)
  42 __releases(ohci->lock)
  43 __acquires(ohci->lock)
  44 {
  45         struct device *dev = ohci_to_hcd(ohci)->self.controller;
  46         struct usb_host_endpoint *ep = urb->ep;
  47         struct urb_priv *urb_priv;
  48
  49         // ASSERT (urb->hcpriv != 0);
  50
  51  restart:
  52         urb_free_priv (ohci, urb->hcpriv);
  53         urb->hcpriv = NULL;
  54         if (likely(status == -EINPROGRESS))
  55                 status = 0;
  56
  57         switch (usb_pipetype (urb->pipe)) {
  58         case PIPE_ISOCHRONOUS:
  59                 ohci_to_hcd(ohci)->self.bandwidth_isoc_reqs--;
  60                 if (ohci_to_hcd(ohci)->self.bandwidth_isoc_reqs == 0) {
  61                         if (quirk_amdiso(ohci))
  62                                 usb_amd_quirk_pll_enable();
  63                         if (quirk_amdprefetch(ohci))
  64                                 sb800_prefetch(dev, 0);
  65                 }
  66                 break;
  67         case PIPE_INTERRUPT:
  68                 ohci_to_hcd(ohci)->self.bandwidth_int_reqs--;
  69                 break;
  70         }
  71
  72         /* urb->complete() can reenter this HCD */
  73         usb_hcd_unlink_urb_from_ep(ohci_to_hcd(ohci), urb);
  74         spin_unlock (&ohci->lock);
  75         usb_hcd_giveback_urb(ohci_to_hcd(ohci), urb, status);
  76         spin_lock (&ohci->lock);
  77
  78         /* stop periodic dma if it's not needed */
  79         if (ohci_to_hcd(ohci)->self.bandwidth_isoc_reqs == 0
  80                         && ohci_to_hcd(ohci)->self.bandwidth_int_reqs == 0) {
  81                 ohci->hc_control &= ~(OHCI_CTRL_PLE|OHCI_CTRL_IE);
  82                 ohci_writel (ohci, ohci->hc_control, &ohci->regs->control);
  83         }
  84
  85         /*
  86          * An isochronous URB that is sumitted too late won't have any TDs
  87          * (marked by the fact that the td_cnt value is larger than the
  88          * actual number of TDs).  If the next URB on this endpoint is like
  89          * that, give it back now.
  90          */
  91         if (!list_empty(&ep->urb_list)) {
  92                 urb = list_first_entry(&ep->urb_list, struct urb, urb_list);
  93                 urb_priv = urb->hcpriv;
  94                 if (urb_priv->td_cnt > urb_priv->length) {
  95                         status = 0;
  96                         goto restart;
  97                 }
  98         }
  99 }
 100
 101
 102 /*-------------------------------------------------------------------------*
 103  * ED handling functions
 104  *-------------------------------------------------------------------------*/
 105
 106 /* search for the right schedule branch to use for a periodic ed.
 107  * does some load balancing; returns the branch, or negative errno.
 108  */
 109 static int balance (struct ohci_hcd *ohci, int interval, int load)
 110 {
 111         int     i, branch = -ENOSPC;
 112
 113         /* iso periods can be huge; iso tds specify frame numbers */
 114         if (interval > NUM_INTS)
 115                 interval = NUM_INTS;
 116
 117         /* search for the least loaded schedule branch of that period
 118          * that has enough bandwidth left unreserved.
 119          */
 120         for (i = 0; i < interval ; i++) {
 121                 if (branch < 0 || ohci->load [branch] > ohci->load [i]) {
 122                         int     j;
 123
 124                         /* usb 1.1 says 90% of one frame */
 125                         for (j = i; j < NUM_INTS; j += interval) {
 126                                 if ((ohci->load [j] + load) > 900)
 127                                         break;
 128                         }
 129                         if (j < NUM_INTS)
 130                                 continue;
 131                         branch = i;
 132                 }
 133         }
 134         return branch;
 135 }
 136
 137 /*-------------------------------------------------------------------------*/
 138
 139 /* both iso and interrupt requests have periods; this routine puts them
 140  * into the schedule tree in the apppropriate place.  most iso devices use
 141  * 1msec periods, but that's not required.
 142  */
 143 static void periodic_link (struct ohci_hcd *ohci, struct ed *ed)
 144 {
 145         unsigned        i;
 146
 147         ohci_dbg(ohci, "link %sed %p branch %d [%dus.], interval %d\n",
 148                 (ed->hwINFO & cpu_to_hc32 (ohci, ED_ISO)) ? "iso " : "",
 149                 ed, ed->branch, ed->load, ed->interval);
 150
 151         for (i = ed->branch; i < NUM_INTS; i += ed->interval) {
 152                 struct ed       **prev = &ohci->periodic [i];
 153                 __hc32          *prev_p = &ohci->hcca->int_table [i];
 154                 struct ed       *here = *prev;
 155
 156                 /* sorting each branch by period (slow before fast)
 157                  * lets us share the faster parts of the tree.
 158                  * (plus maybe: put interrupt eds before iso)
 159                  */
 160                 while (here && ed != here) {
 161                         if (ed->interval > here->interval)
 162                                 break;
 163                         prev = &here->ed_next;
 164                         prev_p = &here->hwNextED;
 165                         here = *prev;
 166                 }
 167                 if (ed != here) {
 168                         ed->ed_next = here;
 169                         if (here)
 170                                 ed->hwNextED = *prev_p;
 171                         wmb ();
 172                         *prev = ed;
 173                         *prev_p = cpu_to_hc32(ohci, ed->dma);
 174                         wmb();
 175                 }
 176                 ohci->load [i] += ed->load;
 177         }
 178         ohci_to_hcd(ohci)->self.bandwidth_allocated += ed->load / ed->interval;
 179 }
 180
 181 /* link an ed into one of the HC chains */
 182
 183 static int ed_schedule (struct ohci_hcd *ohci, struct ed *ed)
 184 {
 185         int     branch;
 186
 187         ed->ed_prev = NULL;
 188         ed->ed_next = NULL;
 189         ed->hwNextED = 0;
 190         wmb ();
 191
 192         /* we care about rm_list when setting CLE/BLE in case the HC was at
 193          * work on some TD when CLE/BLE was turned off, and isn't quiesced
 194          * yet.  finish_unlinks() restarts as needed, some upcoming INTR_SF.
 195          *
 196          * control and bulk EDs are doubly linked (ed_next, ed_prev), but
 197          * periodic ones are singly linked (ed_next). that's because the
 198          * periodic schedule encodes a tree like figure 3-5 in the ohci
 199          * spec:  each qh can have several "previous" nodes, and the tree
 200          * doesn't have unused/idle descriptors.
 201          */
 202         switch (ed->type) {
 203         case PIPE_CONTROL:
 204                 if (ohci->ed_controltail == NULL) {
 205                         WARN_ON (ohci->hc_control & OHCI_CTRL_CLE);
 206                         ohci_writel (ohci, ed->dma,
 207                                         &ohci->regs->ed_controlhead);
 208                 } else {
 209                         ohci->ed_controltail->ed_next = ed;
 210                         ohci->ed_controltail->hwNextED = cpu_to_hc32 (ohci,
 211                                                                 ed->dma);
 212                 }
 213                 ed->ed_prev = ohci->ed_controltail;
 214                 if (!ohci->ed_controltail && !ohci->ed_rm_list) {
 215                         wmb();
 216                         ohci->hc_control |= OHCI_CTRL_CLE;
 217                         ohci_writel (ohci, 0, &ohci->regs->ed_controlcurrent);
 218                         ohci_writel (ohci, ohci->hc_control,
 219                                         &ohci->regs->control);
 220                 }
 221                 ohci->ed_controltail = ed;
 222                 break;
 223
 224         case PIPE_BULK:
 225                 if (ohci->ed_bulktail == NULL) {
 226                         WARN_ON (ohci->hc_control & OHCI_CTRL_BLE);
 227                         ohci_writel (ohci, ed->dma, &ohci->regs->ed_bulkhead);
 228                 } else {
 229                         ohci->ed_bulktail->ed_next = ed;
 230                         ohci->ed_bulktail->hwNextED = cpu_to_hc32 (ohci,
 231                                                                 ed->dma);
 232                 }
 233                 ed->ed_prev = ohci->ed_bulktail;
 234                 if (!ohci->ed_bulktail && !ohci->ed_rm_list) {
 235                         wmb();
 236                         ohci->hc_control |= OHCI_CTRL_BLE;
 237                         ohci_writel (ohci, 0, &ohci->regs->ed_bulkcurrent);
 238                         ohci_writel (ohci, ohci->hc_control,
 239                                         &ohci->regs->control);
 240                 }
 241                 ohci->ed_bulktail = ed;
 242                 break;
 243
 244         // case PIPE_INTERRUPT:
 245         // case PIPE_ISOCHRONOUS:
 246         default:
 247                 branch = balance (ohci, ed->interval, ed->load);
 248                 if (branch < 0) {
 249                         ohci_dbg (ohci,
 250                                 "ERR %d, interval %d msecs, load %d\n",
 251                                 branch, ed->interval, ed->load);
 252                         // FIXME if there are TDs queued, fail them!
 253                         return branch;
 254                 }
 255                 ed->branch = branch;
 256                 periodic_link (ohci, ed);
 257         }
 258
 259         /* the HC may not see the schedule updates yet, but if it does
 260          * then they'll be properly ordered.
 261          */
 262
 263         ed->state = ED_OPER;
 264         return 0;
 265 }
 266
 267 /*-------------------------------------------------------------------------*/
 268
 269 /* scan the periodic table to find and unlink this ED */
 270 static void periodic_unlink (struct ohci_hcd *ohci, struct ed *ed)
 271 {
 272         int     i;
 273
 274         for (i = ed->branch; i < NUM_INTS; i += ed->interval) {
 275                 struct ed       *temp;
 276                 struct ed       **prev = &ohci->periodic [i];
 277                 __hc32          *prev_p = &ohci->hcca->int_table [i];
 278
 279                 while (*prev && (temp = *prev) != ed) {
 280                         prev_p = &temp->hwNextED;
 281                         prev = &temp->ed_next;
 282                 }
 283                 if (*prev) {
 284                         *prev_p = ed->hwNextED;
 285                         *prev = ed->ed_next;
 286                 }
 287                 ohci->load [i] -= ed->load;
 288         }
 289         ohci_to_hcd(ohci)->self.bandwidth_allocated -= ed->load / ed->interval;
 290
 291         ohci_dbg(ohci, "unlink %sed %p branch %d [%dus.], interval %d\n",
 292                 (ed->hwINFO & cpu_to_hc32 (ohci, ED_ISO)) ? "iso " : "",
 293                 ed, ed->branch, ed->load, ed->interval);
 294 }
 295
 296 /* unlink an ed from one of the HC chains.
 297  * just the link to the ed is unlinked.
 298  * the link from the ed still points to another operational ed or 0
 299  * so the HC can eventually finish the processing of the unlinked ed
 300  * (assuming it already started that, which needn't be true).
 301  *
 302  * ED_UNLINK is a transient state: the HC may still see this ED, but soon
 303  * it won't.  ED_SKIP means the HC will finish its current transaction,
 304  * but won't start anything new.  The TD queue may still grow; device
 305  * drivers don't know about this HCD-internal state.
 306  *
 307  * When the HC can't see the ED, something changes ED_UNLINK to one of:
 308  *
 309  *  - ED_OPER: when there's any request queued, the ED gets rescheduled
 310  *    immediately.  HC should be working on them.
 311  *
 312  *  - ED_IDLE: when there's no TD queue or the HC isn't running.
 313  *
 314  * When finish_unlinks() runs later, after SOF interrupt, it will often
 315  * complete one or more URB unlinks before making that state change.
 316  */
 317 static void ed_deschedule (struct ohci_hcd *ohci, struct ed *ed)
 318 {
 319         ed->hwINFO |= cpu_to_hc32 (ohci, ED_SKIP);
 320         wmb ();
 321         ed->state = ED_UNLINK;
 322
 323         /* To deschedule something from the control or bulk list, just
 324          * clear CLE/BLE and wait.  There's no safe way to scrub out list
 325          * head/current registers until later, and "later" isn't very
 326          * tightly specified.  Figure 6-5 and Section 6.4.2.2 show how
 327          * the HC is reading the ED queues (while we modify them).
 328          *
 329          * For now, ed_schedule() is "later".  It might be good paranoia
 330          * to scrub those registers in finish_unlinks(), in case of bugs
 331          * that make the HC try to use them.
 332          */
 333         switch (ed->type) {
 334         case PIPE_CONTROL:
 335                 /* remove ED from the HC's list: */
 336                 if (ed->ed_prev == NULL) {
 337                         if (!ed->hwNextED) {
 338                                 ohci->hc_control &= ~OHCI_CTRL_CLE;
 339                                 ohci_writel (ohci, ohci->hc_control,
 340                                                 &ohci->regs->control);
 341                                 // a ohci_readl() later syncs CLE with the HC
 342                         } else
 343                                 ohci_writel (ohci,
 344                                         hc32_to_cpup (ohci, &ed->hwNextED),
 345                                         &ohci->regs->ed_controlhead);
 346                 } else {
 347                         ed->ed_prev->ed_next = ed->ed_next;
 348                         ed->ed_prev->hwNextED = ed->hwNextED;
 349                 }
 350                 /* remove ED from the HCD's list: */
 351                 if (ohci->ed_controltail == ed) {
 352                         ohci->ed_controltail = ed->ed_prev;
 353                         if (ohci->ed_controltail)
 354                                 ohci->ed_controltail->ed_next = NULL;
 355                 } else if (ed->ed_next) {
 356                         ed->ed_next->ed_prev = ed->ed_prev;
 357                 }
 358                 break;
 359
 360         case PIPE_BULK:
 361                 /* remove ED from the HC's list: */
 362                 if (ed->ed_prev == NULL) {
 363                         if (!ed->hwNextED) {
 364                                 ohci->hc_control &= ~OHCI_CTRL_BLE;
 365                                 ohci_writel (ohci, ohci->hc_control,
 366                                                 &ohci->regs->control);
 367                                 // a ohci_readl() later syncs BLE with the HC
 368                         } else
 369                                 ohci_writel (ohci,
 370                                         hc32_to_cpup (ohci, &ed->hwNextED),
 371                                         &ohci->regs->ed_bulkhead);
 372                 } else {
 373                         ed->ed_prev->ed_next = ed->ed_next;
 374                         ed->ed_prev->hwNextED = ed->hwNextED;
 375                 }
 376                 /* remove ED from the HCD's list: */
 377                 if (ohci->ed_bulktail == ed) {
 378                         ohci->ed_bulktail = ed->ed_prev;
 379                         if (ohci->ed_bulktail)
 380                                 ohci->ed_bulktail->ed_next = NULL;
 381                 } else if (ed->ed_next) {
 382                         ed->ed_next->ed_prev = ed->ed_prev;
 383                 }
 384                 break;
 385
 386         // case PIPE_INTERRUPT:
 387         // case PIPE_ISOCHRONOUS:
 388         default:
 389                 periodic_unlink (ohci, ed);
 390                 break;
 391         }
 392 }
 393
 394
 395 /*-------------------------------------------------------------------------*/
 396
 397 /* get and maybe (re)init an endpoint. init _should_ be done only as part
 398  * of enumeration, usb_set_configuration() or usb_set_interface().
 399  */
 400 static struct ed *ed_get (
 401         struct ohci_hcd         *ohci,
 402         struct usb_host_endpoint *ep,
 403         struct usb_device       *udev,
 404         unsigned int            pipe,
 405         int                     interval
 406 ) {
 407         struct ed               *ed;
 408         unsigned long           flags;
 409
 410         spin_lock_irqsave (&ohci->lock, flags);
 411
 412         ed = ep->hcpriv;
 413         if (!ed) {
 414                 struct td       *td;
 415                 int             is_out;
 416                 u32             info;
 417
 418                 ed = ed_alloc (ohci, GFP_ATOMIC);
 419                 if (!ed) {
 420                         /* out of memory */
 421                         goto done;
 422                 }
 423
 424                 /* dummy td; end of td list for ed */
 425                 td = td_alloc (ohci, GFP_ATOMIC);
 426                 if (!td) {
 427                         /* out of memory */
 428                         ed_free (ohci, ed);
 429                         ed = NULL;
 430                         goto done;
 431                 }
 432                 ed->dummy = td;
 433                 ed->hwTailP = cpu_to_hc32 (ohci, td->td_dma);
 434                 ed->hwHeadP = ed->hwTailP;      /* ED_C, ED_H zeroed */
 435                 ed->state = ED_IDLE;
 436
 437                 is_out = !(ep->desc.bEndpointAddress & USB_DIR_IN);
 438
 439                 /* FIXME usbcore changes dev->devnum before SET_ADDRESS
 440                  * succeeds ... otherwise we wouldn't need "pipe".
 441                  */
 442                 info = usb_pipedevice (pipe);
 443                 ed->type = usb_pipetype(pipe);
 444
 445                 info |= (ep->desc.bEndpointAddress & ~USB_DIR_IN) << 7;
 446                 info |= usb_endpoint_maxp(&ep->desc) << 16;
 447                 if (udev->speed == USB_SPEED_LOW)
 448                         info |= ED_LOWSPEED;
 449                 /* only control transfers store pids in tds */
 450                 if (ed->type != PIPE_CONTROL) {
 451                         info |= is_out ? ED_OUT : ED_IN;
 452                         if (ed->type != PIPE_BULK) {
 453                                 /* periodic transfers... */
 454                                 if (ed->type == PIPE_ISOCHRONOUS)
 455                                         info |= ED_ISO;
 456                                 else if (interval > 32) /* iso can be bigger */
 457                                         interval = 32;
 458                                 ed->interval = interval;
 459                                 ed->load = usb_calc_bus_time (
 460                                         udev->speed, !is_out,
 461                                         ed->type == PIPE_ISOCHRONOUS,
 462                                         usb_endpoint_maxp(&ep->desc))
 463                                                 / 1000;
 464                         }
 465                 }
 466                 ed->hwINFO = cpu_to_hc32(ohci, info);
 467
 468                 ep->hcpriv = ed;
 469         }
 470
 471 done:
 472         spin_unlock_irqrestore (&ohci->lock, flags);
 473         return ed;
 474 }
 475
 476 /*-------------------------------------------------------------------------*/
 477
 478 /* request unlinking of an endpoint from an operational HC.
 479  * put the ep on the rm_list
 480  * real work is done at the next start frame (SF) hardware interrupt
 481  * caller guarantees HCD is running, so hardware access is safe,
 482  * and that ed->state is ED_OPER
 483  */
 484 static void start_ed_unlink (struct ohci_hcd *ohci, struct ed *ed)
 485 {
 486         ed->hwINFO |= cpu_to_hc32 (ohci, ED_DEQUEUE);
 487         ed_deschedule (ohci, ed);
 488
 489         /* rm_list is just singly linked, for simplicity */
 490         ed->ed_next = ohci->ed_rm_list;
 491         ed->ed_prev = NULL;
 492         ohci->ed_rm_list = ed;
 493
 494         /* enable SOF interrupt */
 495         ohci_writel (ohci, OHCI_INTR_SF, &ohci->regs->intrstatus);
 496         ohci_writel (ohci, OHCI_INTR_SF, &ohci->regs->intrenable);
 497         // flush those writes, and get latest HCCA contents
 498         (void) ohci_readl (ohci, &ohci->regs->control);
 499
 500         /* SF interrupt might get delayed; record the frame counter value that
 501          * indicates when the HC isn't looking at it, so concurrent unlinks
 502          * behave.  frame_no wraps every 2^16 msec, and changes right before
 503          * SF is triggered.
 504          */
 505         ed->tick = ohci_frame_no(ohci) + 1;
 506
 507 }
 508
 509 /*-------------------------------------------------------------------------*
 510  * TD handling functions
 511  *-------------------------------------------------------------------------*/
 512
 513 /* enqueue next TD for this URB (OHCI spec 5.2.8.2) */
 514
 515 static void
 516 td_fill (struct ohci_hcd *ohci, u32 info,
 517         dma_addr_t data, int len,
 518         struct urb *urb, int index)
 519 {
 520         struct td               *td, *td_pt;
 521         struct urb_priv         *urb_priv = urb->hcpriv;
 522         int                     is_iso = info & TD_ISO;
 523         int                     hash;
 524
 525         // ASSERT (index < urb_priv->length);
 526
 527         /* aim for only one interrupt per urb.  mostly applies to control
 528          * and iso; other urbs rarely need more than one TD per urb.
 529          * this way, only final tds (or ones with an error) cause IRQs.
 530          * at least immediately; use DI=6 in case any control request is
 531          * tempted to die part way through.  (and to force the hc to flush
 532          * its donelist soonish, even on unlink paths.)
 533          *
 534          * NOTE: could delay interrupts even for the last TD, and get fewer
 535          * interrupts ... increasing per-urb latency by sharing interrupts.
 536          * Drivers that queue bulk urbs may request that behavior.
 537          */
 538         if (index != (urb_priv->length - 1)
 539                         || (urb->transfer_flags & URB_NO_INTERRUPT))
 540                 info |= TD_DI_SET (6);
 541
 542         /* use this td as the next dummy */
 543         td_pt = urb_priv->td [index];
 544
 545         /* fill the old dummy TD */
 546         td = urb_priv->td [index] = urb_priv->ed->dummy;
 547         urb_priv->ed->dummy = td_pt;
 548
 549         td->ed = urb_priv->ed;
 550         td->next_dl_td = NULL;
 551         td->index = index;
 552         td->urb = urb;
 553         td->data_dma = data;
 554         if (!len)
 555                 data = 0;
 556
 557         td->hwINFO = cpu_to_hc32 (ohci, info);
 558         if (is_iso) {
 559                 td->hwCBP = cpu_to_hc32 (ohci, data & 0xFFFFF000);
 560                 *ohci_hwPSWp(ohci, td, 0) = cpu_to_hc16 (ohci,
 561                                                 (data & 0x0FFF) | 0xE000);
 562         } else {
 563                 td->hwCBP = cpu_to_hc32 (ohci, data);
 564         }
 565         if (data)
 566                 td->hwBE = cpu_to_hc32 (ohci, data + len - 1);
 567         else
 568                 td->hwBE = 0;
 569         td->hwNextTD = cpu_to_hc32 (ohci, td_pt->td_dma);
 570
 571         /* append to queue */
 572         list_add_tail (&td->td_list, &td->ed->td_list);
 573
 574         /* hash it for later reverse mapping */
 575         hash = TD_HASH_FUNC (td->td_dma);
 576         td->td_hash = ohci->td_hash [hash];
 577         ohci->td_hash [hash] = td;
 578
 579         /* HC might read the TD (or cachelines) right away ... */
 580         wmb ();
 581         td->ed->hwTailP = td->hwNextTD;
 582 }
 583
 584 /*-------------------------------------------------------------------------*/
 585
 586 /* Prepare all TDs of a transfer, and queue them onto the ED.
 587  * Caller guarantees HC is active.
 588  * Usually the ED is already on the schedule, so TDs might be
 589  * processed as soon as they're queued.
 590  */
 591 static void td_submit_urb (
 592         struct ohci_hcd *ohci,
 593         struct urb      *urb
 594 ) {
 595         struct urb_priv *urb_priv = urb->hcpriv;
 596         struct device *dev = ohci_to_hcd(ohci)->self.controller;
 597         dma_addr_t      data;
 598         int             data_len = urb->transfer_buffer_length;
 599         int             cnt = 0;
 600         u32             info = 0;
 601         int             is_out = usb_pipeout (urb->pipe);
 602         int             periodic = 0;
 603         int             i, this_sg_len, n;
 604         struct scatterlist      *sg;
 605
 606         /* OHCI handles the bulk/interrupt data toggles itself.  We just
 607          * use the device toggle bits for resetting, and rely on the fact
 608          * that resetting toggle is meaningless if the endpoint is active.
 609          */
 610         if (!usb_gettoggle (urb->dev, usb_pipeendpoint (urb->pipe), is_out)) {
 611                 usb_settoggle (urb->dev, usb_pipeendpoint (urb->pipe),
 612                         is_out, 1);
 613                 urb_priv->ed->hwHeadP &= ~cpu_to_hc32 (ohci, ED_C);
 614         }
 615
 616         list_add (&urb_priv->pending, &ohci->pending);
 617
 618         i = urb->num_mapped_sgs;
 619         if (data_len > 0 && i > 0) {
 620                 sg = urb->sg;
 621                 data = sg_dma_address(sg);
 622
 623                 /*
 624                  * urb->transfer_buffer_length may be smaller than the
 625                  * size of the scatterlist (or vice versa)
 626                  */
 627                 this_sg_len = min_t(int, sg_dma_len(sg), data_len);
 628         } else {
 629                 sg = NULL;
 630                 if (data_len)
 631                         data = urb->transfer_dma;
 632                 else
 633                         data = 0;
 634                 this_sg_len = data_len;
 635         }
 636
 637         /* NOTE:  TD_CC is set so we can tell which TDs the HC processed by
 638          * using TD_CC_GET, as well as by seeing them on the done list.
 639          * (CC = NotAccessed ... 0x0F, or 0x0E in PSWs for ISO.)
 640          */
 641         switch (urb_priv->ed->type) {
 642
 643         /* Bulk and interrupt are identical except for where in the schedule
 644          * their EDs live.
 645          */
 646         case PIPE_INTERRUPT:
 647                 /* ... and periodic urbs have extra accounting */
 648                 periodic = ohci_to_hcd(ohci)->self.bandwidth_int_reqs++ == 0
 649                         && ohci_to_hcd(ohci)->self.bandwidth_isoc_reqs == 0;
 650                 fallthrough;
 651         case PIPE_BULK:
 652                 info = is_out
 653                         ? TD_T_TOGGLE | TD_CC | TD_DP_OUT
 654                         : TD_T_TOGGLE | TD_CC | TD_DP_IN;
 655                 /* TDs _could_ transfer up to 8K each */
 656                 for (;;) {
 657                         n = min(this_sg_len, 4096);
 658
 659                         /* maybe avoid ED halt on final TD short read */
 660                         if (n >= data_len || (i == 1 && n >= this_sg_len)) {
 661                                 if (!(urb->transfer_flags & URB_SHORT_NOT_OK))
 662                                         info |= TD_R;
 663                         }
 664                         td_fill(ohci, info, data, n, urb, cnt);
 665                         this_sg_len -= n;
 666                         data_len -= n;
 667                         data += n;
 668                         cnt++;
 669
 670                         if (this_sg_len <= 0) {
 671                                 if (--i <= 0 || data_len <= 0)
 672                                         break;
 673                                 sg = sg_next(sg);
 674                                 data = sg_dma_address(sg);
 675                                 this_sg_len = min_t(int, sg_dma_len(sg),
 676                                                 data_len);
 677                         }
 678                 }
 679                 if ((urb->transfer_flags & URB_ZERO_PACKET)
 680                                 && cnt < urb_priv->length) {
 681                         td_fill (ohci, info, 0, 0, urb, cnt);
 682                         cnt++;
 683                 }
 684                 /* maybe kickstart bulk list */
 685                 if (urb_priv->ed->type == PIPE_BULK) {
 686                         wmb ();
 687                         ohci_writel (ohci, OHCI_BLF, &ohci->regs->cmdstatus);
 688                 }
 689                 break;
 690
 691         /* control manages DATA0/DATA1 toggle per-request; SETUP resets it,
 692          * any DATA phase works normally, and the STATUS ack is special.
 693          */
 694         case PIPE_CONTROL:
 695                 info = TD_CC | TD_DP_SETUP | TD_T_DATA0;
 696                 td_fill (ohci, info, urb->setup_dma, 8, urb, cnt++);
 697                 if (data_len > 0) {
 698                         info = TD_CC | TD_R | TD_T_DATA1;
 699                         info |= is_out ? TD_DP_OUT : TD_DP_IN;
 700                         /* NOTE:  mishandles transfers >8K, some >4K */
 701                         td_fill (ohci, info, data, data_len, urb, cnt++);
 702                 }
 703                 info = (is_out || data_len == 0)
 704                         ? TD_CC | TD_DP_IN | TD_T_DATA1
 705                         : TD_CC | TD_DP_OUT | TD_T_DATA1;
 706                 td_fill (ohci, info, data, 0, urb, cnt++);
 707                 /* maybe kickstart control list */
 708                 wmb ();
 709                 ohci_writel (ohci, OHCI_CLF, &ohci->regs->cmdstatus);
 710                 break;
 711
 712         /* ISO has no retransmit, so no toggle; and it uses special TDs.
 713          * Each TD could handle multiple consecutive frames (interval 1);
 714          * we could often reduce the number of TDs here.
 715          */
 716         case PIPE_ISOCHRONOUS:
 717                 for (cnt = urb_priv->td_cnt; cnt < urb->number_of_packets;
 718                                 cnt++) {
 719                         int     frame = urb->start_frame;
 720
 721                         // FIXME scheduling should handle frame counter
 722                         // roll-around ... exotic case (and OHCI has
 723                         // a 2^16 iso range, vs other HCs max of 2^10)
 724                         frame += cnt * urb->interval;
 725                         frame &= 0xffff;
 726                         td_fill (ohci, TD_CC | TD_ISO | frame,
 727                                 data + urb->iso_frame_desc [cnt].offset,
 728                                 urb->iso_frame_desc [cnt].length, urb, cnt);
 729                 }
 730                 if (ohci_to_hcd(ohci)->self.bandwidth_isoc_reqs == 0) {
 731                         if (quirk_amdiso(ohci))
 732                                 usb_amd_quirk_pll_disable();
 733                         if (quirk_amdprefetch(ohci))
 734                                 sb800_prefetch(dev, 1);
 735                 }
 736                 periodic = ohci_to_hcd(ohci)->self.bandwidth_isoc_reqs++ == 0
 737                         && ohci_to_hcd(ohci)->self.bandwidth_int_reqs == 0;
 738                 break;
 739         }
 740
 741         /* start periodic dma if needed */
 742         if (periodic) {
 743                 wmb ();
 744                 ohci->hc_control |= OHCI_CTRL_PLE|OHCI_CTRL_IE;
 745                 ohci_writel (ohci, ohci->hc_control, &ohci->regs->control);
 746         }
 747
 748         // ASSERT (urb_priv->length == cnt);
 749 }
 750
 751 /*-------------------------------------------------------------------------*
 752  * Done List handling functions
 753  *-------------------------------------------------------------------------*/
 754
 755 /* calculate transfer length/status and update the urb */
 756 static int td_done(struct ohci_hcd *ohci, struct urb *urb, struct td *td)
 757 {
 758         u32     tdINFO = hc32_to_cpup (ohci, &td->hwINFO);
 759         int     cc = 0;
 760         int     status = -EINPROGRESS;
 761
 762         list_del (&td->td_list);
 763
 764         /* ISO ... drivers see per-TD length/status */
 765         if (tdINFO & TD_ISO) {
 766                 u16     tdPSW = ohci_hwPSW(ohci, td, 0);
 767                 int     dlen = 0;
 768
 769                 /* NOTE:  assumes FC in tdINFO == 0, and that
 770                  * only the first of 0..MAXPSW psws is used.
 771                  */
 772
 773                 cc = (tdPSW >> 12) & 0xF;
 774                 if (tdINFO & TD_CC)     /* hc didn't touch? */
 775                         return status;
 776
 777                 if (usb_pipeout (urb->pipe))
 778                         dlen = urb->iso_frame_desc [td->index].length;
 779                 else {
 780                         /* short reads are always OK for ISO */
 781                         if (cc == TD_DATAUNDERRUN)
 782                                 cc = TD_CC_NOERROR;
 783                         dlen = tdPSW & 0x3ff;
 784                 }
 785                 urb->actual_length += dlen;
 786                 urb->iso_frame_desc [td->index].actual_length = dlen;
 787                 urb->iso_frame_desc [td->index].status = cc_to_error [cc];
 788
 789                 if (cc != TD_CC_NOERROR)
 790                         ohci_dbg(ohci,
 791                                 "urb %p iso td %p (%d) len %d cc %d\n",
 792                                 urb, td, 1 + td->index, dlen, cc);
 793
 794         /* BULK, INT, CONTROL ... drivers see aggregate length/status,
 795          * except that "setup" bytes aren't counted and "short" transfers
 796          * might not be reported as errors.
 797          */
 798         } else {
 799                 int     type = usb_pipetype (urb->pipe);
 800                 u32     tdBE = hc32_to_cpup (ohci, &td->hwBE);
 801
 802                 cc = TD_CC_GET (tdINFO);
 803
 804                 /* update packet status if needed (short is normally ok) */
 805                 if (cc == TD_DATAUNDERRUN
 806                                 && !(urb->transfer_flags & URB_SHORT_NOT_OK))
 807                         cc = TD_CC_NOERROR;
 808                 if (cc != TD_CC_NOERROR && cc < 0x0E)
 809                         status = cc_to_error[cc];
 810
 811                 /* count all non-empty packets except control SETUP packet */
 812                 if ((type != PIPE_CONTROL || td->index != 0) && tdBE != 0) {
 813                         if (td->hwCBP == 0)
 814                                 urb->actual_length += tdBE - td->data_dma + 1;
 815                         else
 816                                 urb->actual_length +=
 817                                           hc32_to_cpup (ohci, &td->hwCBP)
 818                                         - td->data_dma;
 819                 }
 820
 821                 if (cc != TD_CC_NOERROR && cc < 0x0E)
 822                         ohci_dbg(ohci,
 823                                 "urb %p td %p (%d) cc %d, len=%d/%d\n",
 824                                 urb, td, 1 + td->index, cc,
 825                                 urb->actual_length,
 826                                 urb->transfer_buffer_length);
 827         }
 828         return status;
 829 }
 830
 831 /*-------------------------------------------------------------------------*/
 832
 833 static void ed_halted(struct ohci_hcd *ohci, struct td *td, int cc)
 834 {
 835         struct urb              *urb = td->urb;
 836         urb_priv_t              *urb_priv = urb->hcpriv;
 837         struct ed               *ed = td->ed;
 838         struct list_head        *tmp = td->td_list.next;
 839         __hc32                  toggle = ed->hwHeadP & cpu_to_hc32 (ohci, ED_C);
 840
 841         /* clear ed halt; this is the td that caused it, but keep it inactive
 842          * until its urb->complete() has a chance to clean up.
 843          */
 844         ed->hwINFO |= cpu_to_hc32 (ohci, ED_SKIP);
 845         wmb ();
 846         ed->hwHeadP &= ~cpu_to_hc32 (ohci, ED_H);
 847
 848         /* Get rid of all later tds from this urb.  We don't have
 849          * to be careful: no errors and nothing was transferred.
 850          * Also patch the ed so it looks as if those tds completed normally.
 851          */
 852         while (tmp != &ed->td_list) {
 853                 struct td       *next;
 854
 855                 next = list_entry (tmp, struct td, td_list);
 856                 tmp = next->td_list.next;
 857
 858                 if (next->urb != urb)
 859                         break;
 860
 861                 /* NOTE: if multi-td control DATA segments get supported,
 862                  * this urb had one of them, this td wasn't the last td
 863                  * in that segment (TD_R clear), this ed halted because
 864                  * of a short read, _and_ URB_SHORT_NOT_OK is clear ...
 865                  * then we need to leave the control STATUS packet queued
 866                  * and clear ED_SKIP.
 867                  */
 868
 869                 list_del(&next->td_list);
 870                 urb_priv->td_cnt++;
 871                 ed->hwHeadP = next->hwNextTD | toggle;
 872         }
 873
 874         /* help for troubleshooting:  report anything that
 875          * looks odd ... that doesn't include protocol stalls
 876          * (or maybe some other things)
 877          */
 878         switch (cc) {
 879         case TD_DATAUNDERRUN:
 880                 if ((urb->transfer_flags & URB_SHORT_NOT_OK) == 0)
 881                         break;
 882                 fallthrough;
 883         case TD_CC_STALL:
 884                 if (usb_pipecontrol (urb->pipe))
 885                         break;
 886                 fallthrough;
 887         default:
 888                 ohci_dbg (ohci,
 889                         "urb %p path %s ep%d%s %08x cc %d --> status %d\n",
 890                         urb, urb->dev->devpath,
 891                         usb_pipeendpoint (urb->pipe),
 892                         usb_pipein (urb->pipe) ? "in" : "out",
 893                         hc32_to_cpu (ohci, td->hwINFO),
 894                         cc, cc_to_error [cc]);
 895         }
 896 }
 897
 898 /* Add a TD to the done list */
 899 static void add_to_done_list(struct ohci_hcd *ohci, struct td *td)
 900 {
 901         struct td       *td2, *td_prev;
 902         struct ed       *ed;
 903
 904         if (td->next_dl_td)
 905                 return;         /* Already on the list */
 906
 907         /* Add all the TDs going back until we reach one that's on the list */
 908         ed = td->ed;
 909         td2 = td_prev = td;
 910         list_for_each_entry_continue_reverse(td2, &ed->td_list, td_list) {
 911                 if (td2->next_dl_td)
 912                         break;
 913                 td2->next_dl_td = td_prev;
 914                 td_prev = td2;
 915         }
 916
 917         if (ohci->dl_end)
 918                 ohci->dl_end->next_dl_td = td_prev;
 919         else
 920                 ohci->dl_start = td_prev;
 921
 922         /*
 923          * Make td->next_dl_td point to td itself, to mark the fact
 924          * that td is on the done list.
 925          */
 926         ohci->dl_end = td->next_dl_td = td;
 927
 928         /* Did we just add the latest pending TD? */
 929         td2 = ed->pending_td;
 930         if (td2 && td2->next_dl_td)
 931                 ed->pending_td = NULL;
 932 }
 933
 934 /* Get the entries on the hardware done queue and put them on our list */
 935 static void update_done_list(struct ohci_hcd *ohci)
 936 {
 937         u32             td_dma;
 938         struct td       *td = NULL;
 939
 940         td_dma = hc32_to_cpup (ohci, &ohci->hcca->done_head);
 941         ohci->hcca->done_head = 0;
 942         wmb();
 943
 944         /* get TD from hc's singly linked list, and
 945          * add to ours.  ed->td_list changes later.
 946          */
 947         while (td_dma) {
 948                 int             cc;
 949
 950                 td = dma_to_td (ohci, td_dma);
 951                 if (!td) {
 952                         ohci_err (ohci, "bad entry %8x\n", td_dma);
 953                         break;
 954                 }
 955
 956                 td->hwINFO |= cpu_to_hc32 (ohci, TD_DONE);
 957                 cc = TD_CC_GET (hc32_to_cpup (ohci, &td->hwINFO));
 958
 959                 /* Non-iso endpoints can halt on error; un-halt,
 960                  * and dequeue any other TDs from this urb.
 961                  * No other TD could have caused the halt.
 962                  */
 963                 if (cc != TD_CC_NOERROR
 964                                 && (td->ed->hwHeadP & cpu_to_hc32 (ohci, ED_H)))
 965                         ed_halted(ohci, td, cc);
 966
 967                 td_dma = hc32_to_cpup (ohci, &td->hwNextTD);
 968                 add_to_done_list(ohci, td);
 969         }
 970 }
 971
 972 /*-------------------------------------------------------------------------*/
 973
 974 /* there are some urbs/eds to unlink; called in_irq(), with HCD locked */
 975 static void finish_unlinks(struct ohci_hcd *ohci)
 976 {
 977         unsigned        tick = ohci_frame_no(ohci);
 978         struct ed       *ed, **last;
 979
 980 rescan_all:
 981         for (last = &ohci->ed_rm_list, ed = *last; ed != NULL; ed = *last) {
 982                 struct list_head        *entry, *tmp;
 983                 int                     completed, modified;
 984                 __hc32                  *prev;
 985
 986                 /* only take off EDs that the HC isn't using, accounting for
 987                  * frame counter wraps and EDs with partially retired TDs
 988                  */
 989                 if (likely(ohci->rh_state == OHCI_RH_RUNNING) &&
 990                                 tick_before(tick, ed->tick)) {
 991 skip_ed:
 992                         last = &ed->ed_next;
 993                         continue;
 994                 }
 995                 if (!list_empty(&ed->td_list)) {
 996                         struct td       *td;
 997                         u32             head;
 998
 999                         td = list_first_entry(&ed->td_list, struct td, td_list);
1000
1001                         /* INTR_WDH may need to clean up first */
1002                         head = hc32_to_cpu(ohci, ed->hwHeadP) & TD_MASK;
1003                         if (td->td_dma != head &&
1004                                         ohci->rh_state == OHCI_RH_RUNNING)
1005                                 goto skip_ed;
1006
1007                         /* Don't mess up anything already on the done list */
1008                         if (td->next_dl_td)
1009                                 goto skip_ed;
1010                 }
1011
1012                 /* ED's now officially unlinked, hc doesn't see */
1013                 ed->hwHeadP &= ~cpu_to_hc32(ohci, ED_H);
1014                 ed->hwNextED = 0;
1015                 wmb();
1016                 ed->hwINFO &= ~cpu_to_hc32(ohci, ED_SKIP | ED_DEQUEUE);
1017
1018                 /* reentrancy:  if we drop the schedule lock, someone might
1019                  * have modified this list.  normally it's just prepending
1020                  * entries (which we'd ignore), but paranoia won't hurt.
1021                  */
1022                 *last = ed->ed_next;
1023                 ed->ed_next = NULL;
1024                 modified = 0;
1025
1026                 /* unlink urbs as requested, but rescan the list after
1027                  * we call a completion since it might have unlinked
1028                  * another (earlier) urb
1029                  *
1030                  * When we get here, the HC doesn't see this ed.  But it
1031                  * must not be rescheduled until all completed URBs have
1032                  * been given back to the driver.
1033                  */
1034 rescan_this:
1035                 completed = 0;
1036                 prev = &ed->hwHeadP;
1037                 list_for_each_safe (entry, tmp, &ed->td_list) {
1038                         struct td       *td;
1039                         struct urb      *urb;
1040                         urb_priv_t      *urb_priv;
1041                         __hc32          savebits;
1042                         u32             tdINFO;
1043
1044                         td = list_entry (entry, struct td, td_list);
1045                         urb = td->urb;
1046                         urb_priv = td->urb->hcpriv;
1047
1048                         if (!urb->unlinked) {
1049                                 prev = &td->hwNextTD;
1050                                 continue;
1051                         }
1052
1053                         /* patch pointer hc uses */
1054                         savebits = *prev & ~cpu_to_hc32 (ohci, TD_MASK);
1055                         *prev = td->hwNextTD | savebits;
1056
1057                         /* If this was unlinked, the TD may not have been
1058                          * retired ... so manually save the data toggle.
1059                          * The controller ignores the value we save for
1060                          * control and ISO endpoints.
1061                          */
1062                         tdINFO = hc32_to_cpup(ohci, &td->hwINFO);
1063                         if ((tdINFO & TD_T) == TD_T_DATA0)
1064                                 ed->hwHeadP &= ~cpu_to_hc32(ohci, ED_C);
1065                         else if ((tdINFO & TD_T) == TD_T_DATA1)
1066                                 ed->hwHeadP |= cpu_to_hc32(ohci, ED_C);
1067
1068                         /* HC may have partly processed this TD */
1069                         td_done (ohci, urb, td);
1070                         urb_priv->td_cnt++;
1071
1072                         /* if URB is done, clean up */
1073                         if (urb_priv->td_cnt >= urb_priv->length) {
1074                                 modified = completed = 1;
1075                                 finish_urb(ohci, urb, 0);
1076                         }
1077                 }
1078                 if (completed && !list_empty (&ed->td_list))
1079                         goto rescan_this;
1080
1081                 /*
1082                  * If no TDs are queued, ED is now idle.
1083                  * Otherwise, if the HC is running, reschedule.
1084                  * If the HC isn't running, add ED back to the
1085                  * start of the list for later processing.
1086                  */
1087                 if (list_empty(&ed->td_list)) {
1088                         ed->state = ED_IDLE;
1089                         list_del(&ed->in_use_list);
1090                 } else if (ohci->rh_state == OHCI_RH_RUNNING) {
1091                         ed_schedule(ohci, ed);
1092                 } else {
1093                         ed->ed_next = ohci->ed_rm_list;
1094                         ohci->ed_rm_list = ed;
1095                         /* Don't loop on the same ED */
1096                         if (last == &ohci->ed_rm_list)
1097                                 last = &ed->ed_next;
1098                 }
1099
1100                 if (modified)
1101                         goto rescan_all;
1102         }
1103
1104         /* maybe reenable control and bulk lists */
1105         if (ohci->rh_state == OHCI_RH_RUNNING && !ohci->ed_rm_list) {
1106                 u32     command = 0, control = 0;
1107
1108                 if (ohci->ed_controltail) {
1109                         command |= OHCI_CLF;
1110                         if (quirk_zfmicro(ohci))
1111                                 mdelay(1);
1112                         if (!(ohci->hc_control & OHCI_CTRL_CLE)) {
1113                                 control |= OHCI_CTRL_CLE;
1114                                 ohci_writel (ohci, 0,
1115                                         &ohci->regs->ed_controlcurrent);
1116                         }
1117                 }
1118                 if (ohci->ed_bulktail) {
1119                         command |= OHCI_BLF;
1120                         if (quirk_zfmicro(ohci))
1121                                 mdelay(1);
1122                         if (!(ohci->hc_control & OHCI_CTRL_BLE)) {
1123                                 control |= OHCI_CTRL_BLE;
1124                                 ohci_writel (ohci, 0,
1125                                         &ohci->regs->ed_bulkcurrent);
1126                         }
1127                 }
1128
1129                 /* CLE/BLE to enable, CLF/BLF to (maybe) kickstart */
1130                 if (control) {
1131                         ohci->hc_control |= control;
1132                         if (quirk_zfmicro(ohci))
1133                                 mdelay(1);
1134                         ohci_writel (ohci, ohci->hc_control,
1135                                         &ohci->regs->control);
1136                 }
1137                 if (command) {
1138                         if (quirk_zfmicro(ohci))
1139                                 mdelay(1);
1140                         ohci_writel (ohci, command, &ohci->regs->cmdstatus);
1141                 }
1142         }
1143 }
1144
1145
1146
1147 /*-------------------------------------------------------------------------*/
1148
1149 /* Take back a TD from the host controller */
1150 static void takeback_td(struct ohci_hcd *ohci, struct td *td)
1151 {
1152         struct urb      *urb = td->urb;
1153         urb_priv_t      *urb_priv = urb->hcpriv;
1154         struct ed       *ed = td->ed;
1155         int             status;
1156
1157         /* update URB's length and status from TD */
1158         status = td_done(ohci, urb, td);
1159         urb_priv->td_cnt++;
1160
1161         /* If all this urb's TDs are done, call complete() */
1162         if (urb_priv->td_cnt >= urb_priv->length)
1163                 finish_urb(ohci, urb, status);
1164
1165         /* clean schedule:  unlink EDs that are no longer busy */
1166         if (list_empty(&ed->td_list)) {
1167                 if (ed->state == ED_OPER)
1168                         start_ed_unlink(ohci, ed);
1169
1170         /* ... reenabling halted EDs only after fault cleanup */
1171         } else if ((ed->hwINFO & cpu_to_hc32(ohci, ED_SKIP | ED_DEQUEUE))
1172                         == cpu_to_hc32(ohci, ED_SKIP)) {
1173                 td = list_entry(ed->td_list.next, struct td, td_list);
1174                 if (!(td->hwINFO & cpu_to_hc32(ohci, TD_DONE))) {
1175                         ed->hwINFO &= ~cpu_to_hc32(ohci, ED_SKIP);
1176                         /* ... hc may need waking-up */
1177                         switch (ed->type) {
1178                         case PIPE_CONTROL:
1179                                 ohci_writel(ohci, OHCI_CLF,
1180                                                 &ohci->regs->cmdstatus);
1181                                 break;
1182                         case PIPE_BULK:
1183                                 ohci_writel(ohci, OHCI_BLF,
1184                                                 &ohci->regs->cmdstatus);
1185                                 break;
1186                         }
1187                 }
1188         }
1189 }
1190
1191 /*
1192  * Process normal completions (error or success) and clean the schedules.
1193  *
1194  * This is the main path for handing urbs back to drivers.  The only other
1195  * normal path is finish_unlinks(), which unlinks URBs using ed_rm_list,
1196  * instead of scanning the (re-reversed) donelist as this does.
1197  */
1198 static void process_done_list(struct ohci_hcd *ohci)
1199 {
1200         struct td       *td;
1201
1202         while (ohci->dl_start) {
1203                 td = ohci->dl_start;
1204                 if (td == ohci->dl_end)
1205                         ohci->dl_start = ohci->dl_end = NULL;
1206                 else
1207                         ohci->dl_start = td->next_dl_td;
1208
1209                 takeback_td(ohci, td);
1210         }
1211 }
1212
1213 /*
1214  * TD takeback and URB giveback must be single-threaded.
1215  * This routine takes care of it all.
1216  */
1217 static void ohci_work(struct ohci_hcd *ohci)
1218 {
1219         if (ohci->working) {
1220                 ohci->restart_work = 1;
1221                 return;
1222         }
1223         ohci->working = 1;
1224
1225  restart:
1226         process_done_list(ohci);
1227         if (ohci->ed_rm_list)
1228                 finish_unlinks(ohci);
1229
1230         if (ohci->restart_work) {
1231                 ohci->restart_work = 0;
1232                 goto restart;
1233         }
1234         ohci->working = 0;
1235 }