drivers/usb/host/ehci-q.c

   1 /*
   2  * Copyright (C) 2001-2004 by David Brownell
   3  *
   4  * This program is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License as published by the
   6  * Free Software Foundation; either version 2 of the License, or (at your
   7  * option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  11  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software Foundation,
  16  * Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17  */
  18
  19 /* this file is part of ehci-hcd.c */
  20
  21 /*-------------------------------------------------------------------------*/
  22
  23 /*
  24  * EHCI hardware queue manipulation ... the core.  QH/QTD manipulation.
  25  *
  26  * Control, bulk, and interrupt traffic all use "qh" lists.  They list "qtd"
  27  * entries describing USB transactions, max 16-20kB/entry (with 4kB-aligned
  28  * buffers needed for the larger number).  We use one QH per endpoint, queue
  29  * multiple urbs (all three types) per endpoint.  URBs may need several qtds.
  30  *
  31  * ISO traffic uses "ISO TD" (itd, and sitd) records, and (along with
  32  * interrupts) needs careful scheduling.  Performance improvements can be
  33  * an ongoing challenge.  That's in "ehci-sched.c".
  34  *
  35  * USB 1.1 devices are handled (a) by "companion" OHCI or UHCI root hubs,
  36  * or otherwise through transaction translators (TTs) in USB 2.0 hubs using
  37  * (b) special fields in qh entries or (c) split iso entries.  TTs will
  38  * buffer low/full speed data so the host collects it at high speed.
  39  */
  40
  41 /*-------------------------------------------------------------------------*/
  42
  43 /* fill a qtd, returning how much of the buffer we were able to queue up */
  44
  45 static int
  46 qtd_fill(struct ehci_hcd *ehci, struct ehci_qtd *qtd, dma_addr_t buf,
  47                   size_t len, int token, int maxpacket)
  48 {
  49         int     i, count;
  50         u64     addr = buf;
  51
  52         /* one buffer entry per 4K ... first might be short or unaligned */
  53         qtd->hw_buf[0] = cpu_to_hc32(ehci, (u32)addr);
  54         qtd->hw_buf_hi[0] = cpu_to_hc32(ehci, (u32)(addr >> 32));
  55         count = 0x1000 - (buf & 0x0fff);        /* rest of that page */
  56         if (likely (len < count))               /* ... iff needed */
  57                 count = len;
  58         else {
  59                 buf +=  0x1000;
  60                 buf &= ~0x0fff;
  61
  62                 /* per-qtd limit: from 16K to 20K (best alignment) */
  63                 for (i = 1; count < len && i < 5; i++) {
  64                         addr = buf;
  65                         qtd->hw_buf[i] = cpu_to_hc32(ehci, (u32)addr);
  66                         qtd->hw_buf_hi[i] = cpu_to_hc32(ehci,
  67                                         (u32)(addr >> 32));
  68                         buf += 0x1000;
  69                         if ((count + 0x1000) < len)
  70                                 count += 0x1000;
  71                         else
  72                                 count = len;
  73                 }
  74
  75                 /* short packets may only terminate transfers */
  76                 if (count != len)
  77                         count -= (count % maxpacket);
  78         }
  79         qtd->hw_token = cpu_to_hc32(ehci, (count << 16) | token);
  80         qtd->length = count;
  81
  82         return count;
  83 }
  84
  85 /*-------------------------------------------------------------------------*/
  86
  87 static inline void
  88 qh_update (struct ehci_hcd *ehci, struct ehci_qh *qh, struct ehci_qtd *qtd)
  89 {
  90         /* writes to an active overlay are unsafe */
  91         BUG_ON(qh->qh_state != QH_STATE_IDLE);
  92
  93         qh->hw_qtd_next = QTD_NEXT(ehci, qtd->qtd_dma);
  94         qh->hw_alt_next = EHCI_LIST_END(ehci);
  95
  96         /* Except for control endpoints, we make hardware maintain data
  97          * toggle (like OHCI) ... here (re)initialize the toggle in the QH,
  98          * and set the pseudo-toggle in udev. Only usb_clear_halt() will
  99          * ever clear it.
 100          */
 101         if (!(qh->hw_info1 & cpu_to_hc32(ehci, 1 << 14))) {
 102                 unsigned        is_out, epnum;
 103
 104                 is_out = !(qtd->hw_token & cpu_to_hc32(ehci, 1 << 8));
 105                 epnum = (hc32_to_cpup(ehci, &qh->hw_info1) >> 8) & 0x0f;
 106                 if (unlikely (!usb_gettoggle (qh->dev, epnum, is_out))) {
 107                         qh->hw_token &= ~cpu_to_hc32(ehci, QTD_TOGGLE);
 108                         usb_settoggle (qh->dev, epnum, is_out, 1);
 109                 }
 110         }
 111
 112         /* HC must see latest qtd and qh data before we clear ACTIVE+HALT */
 113         wmb ();
 114         qh->hw_token &= cpu_to_hc32(ehci, QTD_TOGGLE | QTD_STS_PING);
 115 }
 116
 117 /* if it weren't for a common silicon quirk (writing the dummy into the qh
 118  * overlay, so qh->hw_token wrongly becomes inactive/halted), only fault
 119  * recovery (including urb dequeue) would need software changes to a QH...
 120  */
 121 static void
 122 qh_refresh (struct ehci_hcd *ehci, struct ehci_qh *qh)
 123 {
 124         struct ehci_qtd *qtd;
 125
 126         if (list_empty (&qh->qtd_list))
 127                 qtd = qh->dummy;
 128         else {
 129                 qtd = list_entry (qh->qtd_list.next,
 130                                 struct ehci_qtd, qtd_list);
 131                 /* first qtd may already be partially processed */
 132                 if (cpu_to_hc32(ehci, qtd->qtd_dma) == qh->hw_current)
 133                         qtd = NULL;
 134         }
 135
 136         if (qtd)
 137                 qh_update (ehci, qh, qtd);
 138 }
 139
 140 /*-------------------------------------------------------------------------*/
 141
 142 static void qh_link_async(struct ehci_hcd *ehci, struct ehci_qh *qh);
 143
 144 static void ehci_clear_tt_buffer_complete(struct usb_hcd *hcd,
 145                 struct usb_host_endpoint *ep)
 146 {
 147         struct ehci_hcd         *ehci = hcd_to_ehci(hcd);
 148         struct ehci_qh          *qh = ep->hcpriv;
 149         unsigned long           flags;
 150
 151         spin_lock_irqsave(&ehci->lock, flags);
 152         qh->clearing_tt = 0;
 153         if (qh->qh_state == QH_STATE_IDLE && !list_empty(&qh->qtd_list)
 154                         && HC_IS_RUNNING(hcd->state))
 155                 qh_link_async(ehci, qh);
 156         spin_unlock_irqrestore(&ehci->lock, flags);
 157 }
 158
 159 static void ehci_clear_tt_buffer(struct ehci_hcd *ehci, struct ehci_qh *qh,
 160                 struct urb *urb, u32 token)
 161 {
 162
 163         /* If an async split transaction gets an error or is unlinked,
 164          * the TT buffer may be left in an indeterminate state.  We
 165          * have to clear the TT buffer.
 166          *
 167          * Note: this routine is never called for Isochronous transfers.
 168          */
 169         if (urb->dev->tt && !usb_pipeint(urb->pipe) && !qh->clearing_tt) {
 170 #ifdef DEBUG
 171                 struct usb_device *tt = urb->dev->tt->hub;
 172                 dev_dbg(&tt->dev,
 173                         "clear tt buffer port %d, a%d ep%d t%08x\n",
 174                         urb->dev->ttport, urb->dev->devnum,
 175                         usb_pipeendpoint(urb->pipe), token);
 176 #endif /* DEBUG */
 177                 if (!ehci_is_TDI(ehci)
 178                                 || urb->dev->tt->hub !=
 179                                    ehci_to_hcd(ehci)->self.root_hub) {
 180                         if (usb_hub_clear_tt_buffer(urb) == 0)
 181                                 qh->clearing_tt = 1;
 182                 } else {
 183
 184                         /* REVISIT ARC-derived cores don't clear the root
 185                          * hub TT buffer in this way...
 186                          */
 187                 }
 188         }
 189 }
 190
 191 static int qtd_copy_status (
 192         struct ehci_hcd *ehci,
 193         struct urb *urb,
 194         size_t length,
 195         u32 token
 196 )
 197 {
 198         int     status = -EINPROGRESS;
 199
 200         /* count IN/OUT bytes, not SETUP (even short packets) */
 201         if (likely (QTD_PID (token) != 2))
 202                 urb->actual_length += length - QTD_LENGTH (token);
 203
 204         /* don't modify error codes */
 205         if (unlikely(urb->unlinked))
 206                 return status;
 207
 208         /* force cleanup after short read; not always an error */
 209         if (unlikely (IS_SHORT_READ (token)))
 210                 status = -EREMOTEIO;
 211
 212         /* serious "can't proceed" faults reported by the hardware */
 213         if (token & QTD_STS_HALT) {
 214                 if (token & QTD_STS_BABBLE) {
 215                         /* FIXME "must" disable babbling device's port too */
 216                         status = -EOVERFLOW;
 217                 /* CERR nonzero + halt --> stall */
 218                 } else if (QTD_CERR(token)) {
 219                         status = -EPIPE;
 220
 221                 /* In theory, more than one of the following bits can be set
 222                  * since they are sticky and the transaction is retried.
 223                  * Which to test first is rather arbitrary.
 224                  */
 225                 } else if (token & QTD_STS_MMF) {
 226                         /* fs/ls interrupt xfer missed the complete-split */
 227                         status = -EPROTO;
 228                 } else if (token & QTD_STS_DBE) {
 229                         status = (QTD_PID (token) == 1) /* IN ? */
 230                                 ? -ENOSR  /* hc couldn't read data */
 231                                 : -ECOMM; /* hc couldn't write data */
 232                 } else if (token & QTD_STS_XACT) {
 233                         /* timeout, bad CRC, wrong PID, etc */
 234                         ehci_dbg(ehci, "devpath %s ep%d%s 3strikes\n",
 235                                 urb->dev->devpath,
 236                                 usb_pipeendpoint(urb->pipe),
 237                                 usb_pipein(urb->pipe) ? "in" : "out");
 238                         status = -EPROTO;
 239                 } else {        /* unknown */
 240                         status = -EPROTO;
 241                 }
 242
 243                 ehci_vdbg (ehci,
 244                         "dev%d ep%d%s qtd token %08x --> status %d\n",
 245                         usb_pipedevice (urb->pipe),
 246                         usb_pipeendpoint (urb->pipe),
 247                         usb_pipein (urb->pipe) ? "in" : "out",
 248                         token, status);
 249         }
 250
 251         return status;
 252 }
 253
 254 static void
 255 ehci_urb_done(struct ehci_hcd *ehci, struct urb *urb, int status)
 256 __releases(ehci->lock)
 257 __acquires(ehci->lock)
 258 {
 259         if (likely (urb->hcpriv != NULL)) {
 260                 struct ehci_qh  *qh = (struct ehci_qh *) urb->hcpriv;
 261
 262                 /* S-mask in a QH means it's an interrupt urb */
 263                 if ((qh->hw_info2 & cpu_to_hc32(ehci, QH_SMASK)) != 0) {
 264
 265                         /* ... update hc-wide periodic stats (for usbfs) */
 266                         ehci_to_hcd(ehci)->self.bandwidth_int_reqs--;
 267                 }
 268                 qh_put (qh);
 269         }
 270
 271         if (unlikely(urb->unlinked)) {
 272                 COUNT(ehci->stats.unlink);
 273         } else {
 274                 /* report non-error and short read status as zero */
 275                 if (status == -EINPROGRESS || status == -EREMOTEIO)
 276                         status = 0;
 277                 COUNT(ehci->stats.complete);
 278         }
 279
 280 #ifdef EHCI_URB_TRACE
 281         ehci_dbg (ehci,
 282                 "%s %s urb %p ep%d%s status %d len %d/%d\n",
 283                 __func__, urb->dev->devpath, urb,
 284                 usb_pipeendpoint (urb->pipe),
 285                 usb_pipein (urb->pipe) ? "in" : "out",
 286                 status,
 287                 urb->actual_length, urb->transfer_buffer_length);
 288 #endif
 289
 290         /* complete() can reenter this HCD */
 291         usb_hcd_unlink_urb_from_ep(ehci_to_hcd(ehci), urb);
 292         spin_unlock (&ehci->lock);
 293         usb_hcd_giveback_urb(ehci_to_hcd(ehci), urb, status);
 294         spin_lock (&ehci->lock);
 295 }
 296
 297 static void start_unlink_async (struct ehci_hcd *ehci, struct ehci_qh *qh);
 298 static void unlink_async (struct ehci_hcd *ehci, struct ehci_qh *qh);
 299
 300 static void intr_deschedule (struct ehci_hcd *ehci, struct ehci_qh *qh);
 301 static int qh_schedule (struct ehci_hcd *ehci, struct ehci_qh *qh);
 302
 303 /*
 304  * Process and free completed qtds for a qh, returning URBs to drivers.
 305  * Chases up to qh->hw_current.  Returns number of completions called,
 306  * indicating how much "real" work we did.
 307  */
 308 static unsigned
 309 qh_completions (struct ehci_hcd *ehci, struct ehci_qh *qh)
 310 {
 311         struct ehci_qtd         *last = NULL, *end = qh->dummy;
 312         struct list_head        *entry, *tmp;
 313         int                     last_status = -EINPROGRESS;
 314         int                     stopped;
 315         unsigned                count = 0;
 316         u8                      state;
 317         __le32                  halt = HALT_BIT(ehci);
 318
 319         if (unlikely (list_empty (&qh->qtd_list)))
 320                 return count;
 321
 322         /* completions (or tasks on other cpus) must never clobber HALT
 323          * till we've gone through and cleaned everything up, even when
 324          * they add urbs to this qh's queue or mark them for unlinking.
 325          *
 326          * NOTE:  unlinking expects to be done in queue order.
 327          */
 328         state = qh->qh_state;
 329         qh->qh_state = QH_STATE_COMPLETING;
 330         stopped = (state == QH_STATE_IDLE);
 331
 332         /* remove de-activated QTDs from front of queue.
 333          * after faults (including short reads), cleanup this urb
 334          * then let the queue advance.
 335          * if queue is stopped, handles unlinks.
 336          */
 337         list_for_each_safe (entry, tmp, &qh->qtd_list) {
 338                 struct ehci_qtd *qtd;
 339                 struct urb      *urb;
 340                 u32             token = 0;
 341
 342                 qtd = list_entry (entry, struct ehci_qtd, qtd_list);
 343                 urb = qtd->urb;
 344
 345                 /* clean up any state from previous QTD ...*/
 346                 if (last) {
 347                         if (likely (last->urb != urb)) {
 348                                 ehci_urb_done(ehci, last->urb, last_status);
 349                                 count++;
 350                                 last_status = -EINPROGRESS;
 351                         }
 352                         ehci_qtd_free (ehci, last);
 353                         last = NULL;
 354                 }
 355
 356                 /* ignore urbs submitted during completions we reported */
 357                 if (qtd == end)
 358                         break;
 359
 360                 /* hardware copies qtd out of qh overlay */
 361                 rmb ();
 362                 token = hc32_to_cpu(ehci, qtd->hw_token);
 363
 364                 /* always clean up qtds the hc de-activated */
 365  retry_xacterr:
 366                 if ((token & QTD_STS_ACTIVE) == 0) {
 367
 368                         /* on STALL, error, and short reads this urb must
 369                          * complete and all its qtds must be recycled.
 370                          */
 371                         if ((token & QTD_STS_HALT) != 0) {
 372
 373                                 /* retry transaction errors until we
 374                                  * reach the software xacterr limit
 375                                  */
 376                                 if ((token & QTD_STS_XACT) &&
 377                                                 QTD_CERR(token) == 0 &&
 378                                                 ++qh->xacterrs < QH_XACTERR_MAX &&
 379                                                 !urb->unlinked) {
 380                                         ehci_dbg(ehci,
 381         "detected XactErr len %zu/%zu retry %d\n",
 382         qtd->length - QTD_LENGTH(token), qtd->length, qh->xacterrs);
 383
 384                                         /* reset the token in the qtd and the
 385                                          * qh overlay (which still contains
 386                                          * the qtd) so that we pick up from
 387                                          * where we left off
 388                                          */
 389                                         token &= ~QTD_STS_HALT;
 390                                         token |= QTD_STS_ACTIVE |
 391                                                         (EHCI_TUNE_CERR << 10);
 392                                         qtd->hw_token = cpu_to_hc32(ehci,
 393                                                         token);
 394                                         wmb();
 395                                         qh->hw_token = cpu_to_hc32(ehci, token);
 396                                         goto retry_xacterr;
 397                                 }
 398                                 stopped = 1;
 399
 400                         /* magic dummy for some short reads; qh won't advance.
 401                          * that silicon quirk can kick in with this dummy too.
 402                          *
 403                          * other short reads won't stop the queue, including
 404                          * control transfers (status stage handles that) or
 405                          * most other single-qtd reads ... the queue stops if
 406                          * URB_SHORT_NOT_OK was set so the driver submitting
 407                          * the urbs could clean it up.
 408                          */
 409                         } else if (IS_SHORT_READ (token)
 410                                         && !(qtd->hw_alt_next
 411                                                 & EHCI_LIST_END(ehci))) {
 412                                 stopped = 1;
 413                                 goto halt;
 414                         }
 415
 416                 /* stop scanning when we reach qtds the hc is using */
 417                 } else if (likely (!stopped
 418                                 && HC_IS_RUNNING (ehci_to_hcd(ehci)->state))) {
 419                         break;
 420
 421                 /* scan the whole queue for unlinks whenever it stops */
 422                 } else {
 423                         stopped = 1;
 424
 425                         /* cancel everything if we halt, suspend, etc */
 426                         if (!HC_IS_RUNNING(ehci_to_hcd(ehci)->state))
 427                                 last_status = -ESHUTDOWN;
 428
 429                         /* this qtd is active; skip it unless a previous qtd
 430                          * for its urb faulted, or its urb was canceled.
 431                          */
 432                         else if (last_status == -EINPROGRESS && !urb->unlinked)
 433                                 continue;
 434
 435                         /* qh unlinked; token in overlay may be most current */
 436                         if (state == QH_STATE_IDLE
 437                                         && cpu_to_hc32(ehci, qtd->qtd_dma)
 438                                                 == qh->hw_current) {
 439                                 token = hc32_to_cpu(ehci, qh->hw_token);
 440
 441                                 /* An unlink may leave an incomplete
 442                                  * async transaction in the TT buffer.
 443                                  * We have to clear it.
 444                                  */
 445                                 ehci_clear_tt_buffer(ehci, qh, urb, token);
 446                         }
 447
 448                         /* force halt for unlinked or blocked qh, so we'll
 449                          * patch the qh later and so that completions can't
 450                          * activate it while we "know" it's stopped.
 451                          */
 452                         if ((halt & qh->hw_token) == 0) {
 453 halt:
 454                                 qh->hw_token |= halt;
 455                                 wmb ();
 456                         }
 457                 }
 458
 459                 /* unless we already know the urb's status, collect qtd status
 460                  * and update count of bytes transferred.  in common short read
 461                  * cases with only one data qtd (including control transfers),
 462                  * queue processing won't halt.  but with two or more qtds (for
 463                  * example, with a 32 KB transfer), when the first qtd gets a
 464                  * short read the second must be removed by hand.
 465                  */
 466                 if (last_status == -EINPROGRESS) {
 467                         last_status = qtd_copy_status(ehci, urb,
 468                                         qtd->length, token);
 469                         if (last_status == -EREMOTEIO
 470                                         && (qtd->hw_alt_next
 471                                                 & EHCI_LIST_END(ehci)))
 472                                 last_status = -EINPROGRESS;
 473
 474                         /* As part of low/full-speed endpoint-halt processing
 475                          * we must clear the TT buffer (11.17.5).
 476                          */
 477                         if (unlikely(last_status != -EINPROGRESS &&
 478                                         last_status != -EREMOTEIO))
 479                                 ehci_clear_tt_buffer(ehci, qh, urb, token);
 480                 }
 481
 482                 /* if we're removing something not at the queue head,
 483                  * patch the hardware queue pointer.
 484                  */
 485                 if (stopped && qtd->qtd_list.prev != &qh->qtd_list) {
 486                         last = list_entry (qtd->qtd_list.prev,
 487                                         struct ehci_qtd, qtd_list);
 488                         last->hw_next = qtd->hw_next;
 489                 }
 490
 491                 /* remove qtd; it's recycled after possible urb completion */
 492                 list_del (&qtd->qtd_list);
 493                 last = qtd;
 494
 495                 /* reinit the xacterr counter for the next qtd */
 496                 qh->xacterrs = 0;
 497         }
 498
 499         /* last urb's completion might still need calling */
 500         if (likely (last != NULL)) {
 501                 ehci_urb_done(ehci, last->urb, last_status);
 502                 count++;
 503                 ehci_qtd_free (ehci, last);
 504         }
 505
 506         /* restore original state; caller must unlink or relink */
 507         qh->qh_state = state;
 508
 509         /* be sure the hardware's done with the qh before refreshing
 510          * it after fault cleanup, or recovering from silicon wrongly
 511          * overlaying the dummy qtd (which reduces DMA chatter).
 512          */
 513         if (stopped != 0 || qh->hw_qtd_next == EHCI_LIST_END(ehci)) {
 514                 switch (state) {
 515                 case QH_STATE_IDLE:
 516                         qh_refresh(ehci, qh);
 517                         break;
 518                 case QH_STATE_LINKED:
 519                         /* We won't refresh a QH that's linked (after the HC
 520                          * stopped the queue).  That avoids a race:
 521                          *  - HC reads first part of QH;
 522                          *  - CPU updates that first part and the token;
 523                          *  - HC reads rest of that QH, including token
 524                          * Result:  HC gets an inconsistent image, and then
 525                          * DMAs to/from the wrong memory (corrupting it).
 526                          *
 527                          * That should be rare for interrupt transfers,
 528                          * except maybe high bandwidth ...
 529                          */
 530                         if ((cpu_to_hc32(ehci, QH_SMASK)
 531                                         & qh->hw_info2) != 0) {
 532                                 intr_deschedule (ehci, qh);
 533                                 (void) qh_schedule (ehci, qh);
 534                         } else
 535                                 unlink_async (ehci, qh);
 536                         break;
 537                 /* otherwise, unlink already started */
 538                 }
 539         }
 540
 541         return count;
 542 }
 543
 544 /*-------------------------------------------------------------------------*/
 545
 546 // high bandwidth multiplier, as encoded in highspeed endpoint descriptors
 547 #define hb_mult(wMaxPacketSize) (1 + (((wMaxPacketSize) >> 11) & 0x03))
 548 // ... and packet size, for any kind of endpoint descriptor
 549 #define max_packet(wMaxPacketSize) ((wMaxPacketSize) & 0x07ff)
 550
 551 /*
 552  * reverse of qh_urb_transaction:  free a list of TDs.
 553  * used for cleanup after errors, before HC sees an URB's TDs.
 554  */
 555 static void qtd_list_free (
 556         struct ehci_hcd         *ehci,
 557         struct urb              *urb,
 558         struct list_head        *qtd_list
 559 ) {
 560         struct list_head        *entry, *temp;
 561
 562         list_for_each_safe (entry, temp, qtd_list) {
 563                 struct ehci_qtd *qtd;
 564
 565                 qtd = list_entry (entry, struct ehci_qtd, qtd_list);
 566                 list_del (&qtd->qtd_list);
 567                 ehci_qtd_free (ehci, qtd);
 568         }
 569 }
 570
 571 /*
 572  * create a list of filled qtds for this URB; won't link into qh.
 573  */
 574 static struct list_head *
 575 qh_urb_transaction (
 576         struct ehci_hcd         *ehci,
 577         struct urb              *urb,
 578         struct list_head        *head,
 579         gfp_t                   flags
 580 ) {
 581         struct ehci_qtd         *qtd, *qtd_prev;
 582         dma_addr_t              buf;
 583         int                     len, maxpacket;
 584         int                     is_input;
 585         u32                     token;
 586
 587         /*
 588          * URBs map to sequences of QTDs:  one logical transaction
 589          */
 590         qtd = ehci_qtd_alloc (ehci, flags);
 591         if (unlikely (!qtd))
 592                 return NULL;
 593         list_add_tail (&qtd->qtd_list, head);
 594         qtd->urb = urb;
 595
 596         token = QTD_STS_ACTIVE;
 597         token |= (EHCI_TUNE_CERR << 10);
 598         /* for split transactions, SplitXState initialized to zero */
 599
 600         len = urb->transfer_buffer_length;
 601         is_input = usb_pipein (urb->pipe);
 602         if (usb_pipecontrol (urb->pipe)) {
 603                 /* SETUP pid */
 604                 qtd_fill(ehci, qtd, urb->setup_dma,
 605                                 sizeof (struct usb_ctrlrequest),
 606                                 token | (2 /* "setup" */ << 8), 8);
 607
 608                 /* ... and always at least one more pid */
 609                 token ^= QTD_TOGGLE;
 610                 qtd_prev = qtd;
 611                 qtd = ehci_qtd_alloc (ehci, flags);
 612                 if (unlikely (!qtd))
 613                         goto cleanup;
 614                 qtd->urb = urb;
 615                 qtd_prev->hw_next = QTD_NEXT(ehci, qtd->qtd_dma);
 616                 list_add_tail (&qtd->qtd_list, head);
 617
 618                 /* for zero length DATA stages, STATUS is always IN */
 619                 if (len == 0)
 620                         token |= (1 /* "in" */ << 8);
 621         }
 622
 623         /*
 624          * data transfer stage:  buffer setup
 625          */
 626         buf = urb->transfer_dma;
 627
 628         if (is_input)
 629                 token |= (1 /* "in" */ << 8);
 630         /* else it's already initted to "out" pid (0 << 8) */
 631
 632         maxpacket = max_packet(usb_maxpacket(urb->dev, urb->pipe, !is_input));
 633
 634         /*
 635          * buffer gets wrapped in one or more qtds;
 636          * last one may be "short" (including zero len)
 637          * and may serve as a control status ack
 638          */
 639         for (;;) {
 640                 int this_qtd_len;
 641
 642                 this_qtd_len = qtd_fill(ehci, qtd, buf, len, token, maxpacket);
 643                 len -= this_qtd_len;
 644                 buf += this_qtd_len;
 645
 646                 /*
 647                  * short reads advance to a "magic" dummy instead of the next
 648                  * qtd ... that forces the queue to stop, for manual cleanup.
 649                  * (this will usually be overridden later.)
 650                  */
 651                 if (is_input)
 652                         qtd->hw_alt_next = ehci->async->hw_alt_next;
 653
 654                 /* qh makes control packets use qtd toggle; maybe switch it */
 655                 if ((maxpacket & (this_qtd_len + (maxpacket - 1))) == 0)
 656                         token ^= QTD_TOGGLE;
 657
 658                 if (likely (len <= 0))
 659                         break;
 660
 661                 qtd_prev = qtd;
 662                 qtd = ehci_qtd_alloc (ehci, flags);
 663                 if (unlikely (!qtd))
 664                         goto cleanup;
 665                 qtd->urb = urb;
 666                 qtd_prev->hw_next = QTD_NEXT(ehci, qtd->qtd_dma);
 667                 list_add_tail (&qtd->qtd_list, head);
 668         }
 669
 670         /*
 671          * unless the caller requires manual cleanup after short reads,
 672          * have the alt_next mechanism keep the queue running after the
 673          * last data qtd (the only one, for control and most other cases).
 674          */
 675         if (likely ((urb->transfer_flags & URB_SHORT_NOT_OK) == 0
 676                                 || usb_pipecontrol (urb->pipe)))
 677                 qtd->hw_alt_next = EHCI_LIST_END(ehci);
 678
 679         /*
 680          * control requests may need a terminating data "status" ack;
 681          * bulk ones may need a terminating short packet (zero length).
 682          */
 683         if (likely (urb->transfer_buffer_length != 0)) {
 684                 int     one_more = 0;
 685
 686                 if (usb_pipecontrol (urb->pipe)) {
 687                         one_more = 1;
 688                         token ^= 0x0100;        /* "in" <--> "out"  */
 689                         token |= QTD_TOGGLE;    /* force DATA1 */
 690                 } else if (usb_pipebulk (urb->pipe)
 691                                 && (urb->transfer_flags & URB_ZERO_PACKET)
 692                                 && !(urb->transfer_buffer_length % maxpacket)) {
 693                         one_more = 1;
 694                 }
 695                 if (one_more) {
 696                         qtd_prev = qtd;
 697                         qtd = ehci_qtd_alloc (ehci, flags);
 698                         if (unlikely (!qtd))
 699                                 goto cleanup;
 700                         qtd->urb = urb;
 701                         qtd_prev->hw_next = QTD_NEXT(ehci, qtd->qtd_dma);
 702                         list_add_tail (&qtd->qtd_list, head);
 703
 704                         /* never any data in such packets */
 705                         qtd_fill(ehci, qtd, 0, 0, token, 0);
 706                 }
 707         }
 708
 709         /* by default, enable interrupt on urb completion */
 710         if (likely (!(urb->transfer_flags & URB_NO_INTERRUPT)))
 711                 qtd->hw_token |= cpu_to_hc32(ehci, QTD_IOC);
 712         return head;
 713
 714 cleanup:
 715         qtd_list_free (ehci, urb, head);
 716         return NULL;
 717 }
 718
 719 /*-------------------------------------------------------------------------*/
 720
 721 // Would be best to create all qh's from config descriptors,
 722 // when each interface/altsetting is established.  Unlink
 723 // any previous qh and cancel its urbs first; endpoints are
 724 // implicitly reset then (data toggle too).
 725 // That'd mean updating how usbcore talks to HCDs. (2.7?)
 726
 727
 728 /*
 729  * Each QH holds a qtd list; a QH is used for everything except iso.
 730  *
 731  * For interrupt urbs, the scheduler must set the microframe scheduling
 732  * mask(s) each time the QH gets scheduled.  For highspeed, that's
 733  * just one microframe in the s-mask.  For split interrupt transactions
 734  * there are additional complications: c-mask, maybe FSTNs.
 735  */
 736 static struct ehci_qh *
 737 qh_make (
 738         struct ehci_hcd         *ehci,
 739         struct urb              *urb,
 740         gfp_t                   flags
 741 ) {
 742         struct ehci_qh          *qh = ehci_qh_alloc (ehci, flags);
 743         u32                     info1 = 0, info2 = 0;
 744         int                     is_input, type;
 745         int                     maxp = 0;
 746         struct usb_tt           *tt = urb->dev->tt;
 747
 748         if (!qh)
 749                 return qh;
 750
 751         /*
 752          * init endpoint/device data for this QH
 753          */
 754         info1 |= usb_pipeendpoint (urb->pipe) << 8;
 755         info1 |= usb_pipedevice (urb->pipe) << 0;
 756
 757         is_input = usb_pipein (urb->pipe);
 758         type = usb_pipetype (urb->pipe);
 759         maxp = usb_maxpacket (urb->dev, urb->pipe, !is_input);
 760
 761         /* 1024 byte maxpacket is a hardware ceiling.  High bandwidth
 762          * acts like up to 3KB, but is built from smaller packets.
 763          */
 764         if (max_packet(maxp) > 1024) {
 765                 ehci_dbg(ehci, "bogus qh maxpacket %d\n", max_packet(maxp));
 766                 goto done;
 767         }
 768
 769         /* Compute interrupt scheduling parameters just once, and save.
 770          * - allowing for high bandwidth, how many nsec/uframe are used?
 771          * - split transactions need a second CSPLIT uframe; same question
 772          * - splits also need a schedule gap (for full/low speed I/O)
 773          * - qh has a polling interval
 774          *
 775          * For control/bulk requests, the HC or TT handles these.
 776          */
 777         if (type == PIPE_INTERRUPT) {
 778                 qh->usecs = NS_TO_US(usb_calc_bus_time(USB_SPEED_HIGH,
 779                                 is_input, 0,
 780                                 hb_mult(maxp) * max_packet(maxp)));
 781                 qh->start = NO_FRAME;
 782
 783                 if (urb->dev->speed == USB_SPEED_HIGH) {
 784                         qh->c_usecs = 0;
 785                         qh->gap_uf = 0;
 786
 787                         qh->period = urb->interval >> 3;
 788                         if (qh->period == 0 && urb->interval != 1) {
 789                                 /* NOTE interval 2 or 4 uframes could work.
 790                                  * But interval 1 scheduling is simpler, and
 791                                  * includes high bandwidth.
 792                                  */
 793                                 dbg ("intr period %d uframes, NYET!",
 794                                                 urb->interval);
 795                                 goto done;
 796                         }
 797                 } else {
 798                         int             think_time;
 799
 800                         /* gap is f(FS/LS transfer times) */
 801                         qh->gap_uf = 1 + usb_calc_bus_time (urb->dev->speed,
 802                                         is_input, 0, maxp) / (125 * 1000);
 803
 804                         /* FIXME this just approximates SPLIT/CSPLIT times */
 805                         if (is_input) {         // SPLIT, gap, CSPLIT+DATA
 806                                 qh->c_usecs = qh->usecs + HS_USECS (0);
 807                                 qh->usecs = HS_USECS (1);
 808                         } else {                // SPLIT+DATA, gap, CSPLIT
 809                                 qh->usecs += HS_USECS (1);
 810                                 qh->c_usecs = HS_USECS (0);
 811                         }
 812
 813                         think_time = tt ? tt->think_time : 0;
 814                         qh->tt_usecs = NS_TO_US (think_time +
 815                                         usb_calc_bus_time (urb->dev->speed,
 816                                         is_input, 0, max_packet (maxp)));
 817                         qh->period = urb->interval;
 818                 }
 819         }
 820
 821         /* support for tt scheduling, and access to toggles */
 822         qh->dev = urb->dev;
 823
 824         /* using TT? */
 825         switch (urb->dev->speed) {
 826         case USB_SPEED_LOW:
 827                 info1 |= (1 << 12);     /* EPS "low" */
 828                 /* FALL THROUGH */
 829
 830         case USB_SPEED_FULL:
 831                 /* EPS 0 means "full" */
 832                 if (type != PIPE_INTERRUPT)
 833                         info1 |= (EHCI_TUNE_RL_TT << 28);
 834                 if (type == PIPE_CONTROL) {
 835                         info1 |= (1 << 27);     /* for TT */
 836                         info1 |= 1 << 14;       /* toggle from qtd */
 837                 }
 838                 info1 |= maxp << 16;
 839
 840                 info2 |= (EHCI_TUNE_MULT_TT << 30);
 841
 842                 /* Some Freescale processors have an erratum in which the
 843                  * port number in the queue head was 0..N-1 instead of 1..N.
 844                  */
 845                 if (ehci_has_fsl_portno_bug(ehci))
 846                         info2 |= (urb->dev->ttport-1) << 23;
 847                 else
 848                         info2 |= urb->dev->ttport << 23;
 849
 850                 /* set the address of the TT; for TDI's integrated
 851                  * root hub tt, leave it zeroed.
 852                  */
 853                 if (tt && tt->hub != ehci_to_hcd(ehci)->self.root_hub)
 854                         info2 |= tt->hub->devnum << 16;
 855
 856                 /* NOTE:  if (PIPE_INTERRUPT) { scheduler sets c-mask } */
 857
 858                 break;
 859
 860         case USB_SPEED_HIGH:            /* no TT involved */
 861                 info1 |= (2 << 12);     /* EPS "high" */
 862                 if (type == PIPE_CONTROL) {
 863                         info1 |= (EHCI_TUNE_RL_HS << 28);
 864                         info1 |= 64 << 16;      /* usb2 fixed maxpacket */
 865                         info1 |= 1 << 14;       /* toggle from qtd */
 866                         info2 |= (EHCI_TUNE_MULT_HS << 30);
 867                 } else if (type == PIPE_BULK) {
 868                         info1 |= (EHCI_TUNE_RL_HS << 28);
 869                         /* The USB spec says that high speed bulk endpoints
 870                          * always use 512 byte maxpacket.  But some device
 871                          * vendors decided to ignore that, and MSFT is happy
 872                          * to help them do so.  So now people expect to use
 873                          * such nonconformant devices with Linux too; sigh.
 874                          */
 875                         info1 |= max_packet(maxp) << 16;
 876                         info2 |= (EHCI_TUNE_MULT_HS << 30);
 877                 } else {                /* PIPE_INTERRUPT */
 878                         info1 |= max_packet (maxp) << 16;
 879                         info2 |= hb_mult (maxp) << 30;
 880                 }
 881                 break;
 882         default:
 883                 dbg ("bogus dev %p speed %d", urb->dev, urb->dev->speed);
 884 done:
 885                 qh_put (qh);
 886                 return NULL;
 887         }
 888
 889         /* NOTE:  if (PIPE_INTERRUPT) { scheduler sets s-mask } */
 890
 891         /* init as live, toggle clear, advance to dummy */
 892         qh->qh_state = QH_STATE_IDLE;
 893         qh->hw_info1 = cpu_to_hc32(ehci, info1);
 894         qh->hw_info2 = cpu_to_hc32(ehci, info2);
 895         usb_settoggle (urb->dev, usb_pipeendpoint (urb->pipe), !is_input, 1);
 896         qh_refresh (ehci, qh);
 897         return qh;
 898 }
 899
 900 /*-------------------------------------------------------------------------*/
 901
 902 /* move qh (and its qtds) onto async queue; maybe enable queue.  */
 903
 904 static void qh_link_async (struct ehci_hcd *ehci, struct ehci_qh *qh)
 905 {
 906         __hc32          dma = QH_NEXT(ehci, qh->qh_dma);
 907         struct ehci_qh  *head;
 908
 909         /* Don't link a QH if there's a Clear-TT-Buffer pending */
 910         if (unlikely(qh->clearing_tt))
 911                 return;
 912
 913         /* (re)start the async schedule? */
 914         head = ehci->async;
 915         timer_action_done (ehci, TIMER_ASYNC_OFF);
 916         if (!head->qh_next.qh) {
 917                 u32     cmd = ehci_readl(ehci, &ehci->regs->command);
 918
 919                 if (!(cmd & CMD_ASE)) {
 920                         /* in case a clear of CMD_ASE didn't take yet */
 921                         (void)handshake(ehci, &ehci->regs->status,
 922                                         STS_ASS, 0, 150);
 923                         cmd |= CMD_ASE | CMD_RUN;
 924                         ehci_writel(ehci, cmd, &ehci->regs->command);
 925                         ehci_to_hcd(ehci)->state = HC_STATE_RUNNING;
 926                         /* posted write need not be known to HC yet ... */
 927                 }
 928         }
 929
 930         /* clear halt and/or toggle; and maybe recover from silicon quirk */
 931         if (qh->qh_state == QH_STATE_IDLE)
 932                 qh_refresh (ehci, qh);
 933
 934         /* splice right after start */
 935         qh->qh_next = head->qh_next;
 936         qh->hw_next = head->hw_next;
 937         wmb ();
 938
 939         head->qh_next.qh = qh;
 940         head->hw_next = dma;
 941
 942         qh_get(qh);
 943         qh->xacterrs = 0;
 944         qh->qh_state = QH_STATE_LINKED;
 945         /* qtd completions reported later by interrupt */
 946 }
 947
 948 /*-------------------------------------------------------------------------*/
 949
 950 /*
 951  * For control/bulk/interrupt, return QH with these TDs appended.
 952  * Allocates and initializes the QH if necessary.
 953  * Returns null if it can't allocate a QH it needs to.
 954  * If the QH has TDs (urbs) already, that's great.
 955  */
 956 static struct ehci_qh *qh_append_tds (
 957         struct ehci_hcd         *ehci,
 958         struct urb              *urb,
 959         struct list_head        *qtd_list,
 960         int                     epnum,
 961         void                    **ptr
 962 )
 963 {
 964         struct ehci_qh          *qh = NULL;
 965         __hc32                  qh_addr_mask = cpu_to_hc32(ehci, 0x7f);
 966
 967         qh = (struct ehci_qh *) *ptr;
 968         if (unlikely (qh == NULL)) {
 969                 /* can't sleep here, we have ehci->lock... */
 970                 qh = qh_make (ehci, urb, GFP_ATOMIC);
 971                 *ptr = qh;
 972         }
 973         if (likely (qh != NULL)) {
 974                 struct ehci_qtd *qtd;
 975
 976                 if (unlikely (list_empty (qtd_list)))
 977                         qtd = NULL;
 978                 else
 979                         qtd = list_entry (qtd_list->next, struct ehci_qtd,
 980                                         qtd_list);
 981
 982                 /* control qh may need patching ... */
 983                 if (unlikely (epnum == 0)) {
 984
 985                         /* usb_reset_device() briefly reverts to address 0 */
 986                         if (usb_pipedevice (urb->pipe) == 0)
 987                                 qh->hw_info1 &= ~qh_addr_mask;
 988                 }
 989
 990                 /* just one way to queue requests: swap with the dummy qtd.
 991                  * only hc or qh_refresh() ever modify the overlay.
 992                  */
 993                 if (likely (qtd != NULL)) {
 994                         struct ehci_qtd         *dummy;
 995                         dma_addr_t              dma;
 996                         __hc32                  token;
 997
 998                         /* to avoid racing the HC, use the dummy td instead of
 999                          * the first td of our list (becomes new dummy).  both
1000                          * tds stay deactivated until we're done, when the
1001                          * HC is allowed to fetch the old dummy (4.10.2).
1002                          */
1003                         token = qtd->hw_token;
1004                         qtd->hw_token = HALT_BIT(ehci);
1005                         wmb ();
1006                         dummy = qh->dummy;
1007
1008                         dma = dummy->qtd_dma;
1009                         *dummy = *qtd;
1010                         dummy->qtd_dma = dma;
1011
1012                         list_del (&qtd->qtd_list);
1013                         list_add (&dummy->qtd_list, qtd_list);
1014                         list_splice_tail(qtd_list, &qh->qtd_list);
1015
1016                         ehci_qtd_init(ehci, qtd, qtd->qtd_dma);
1017                         qh->dummy = qtd;
1018
1019                         /* hc must see the new dummy at list end */
1020                         dma = qtd->qtd_dma;
1021                         qtd = list_entry (qh->qtd_list.prev,
1022                                         struct ehci_qtd, qtd_list);
1023                         qtd->hw_next = QTD_NEXT(ehci, dma);
1024
1025                         /* let the hc process these next qtds */
1026                         wmb ();
1027                         dummy->hw_token = token;
1028
1029                         urb->hcpriv = qh_get (qh);
1030                 }
1031         }
1032         return qh;
1033 }
1034
1035 /*-------------------------------------------------------------------------*/
1036
1037 static int
1038 submit_async (
1039         struct ehci_hcd         *ehci,
1040         struct urb              *urb,
1041         struct list_head        *qtd_list,
1042         gfp_t                   mem_flags
1043 ) {
1044         struct ehci_qtd         *qtd;
1045         int                     epnum;
1046         unsigned long           flags;
1047         struct ehci_qh          *qh = NULL;
1048         int                     rc;
1049
1050         qtd = list_entry (qtd_list->next, struct ehci_qtd, qtd_list);
1051         epnum = urb->ep->desc.bEndpointAddress;
1052
1053 #ifdef EHCI_URB_TRACE
1054         ehci_dbg (ehci,
1055                 "%s %s urb %p ep%d%s len %d, qtd %p [qh %p]\n",
1056                 __func__, urb->dev->devpath, urb,
1057                 epnum & 0x0f, (epnum & USB_DIR_IN) ? "in" : "out",
1058                 urb->transfer_buffer_length,
1059                 qtd, urb->ep->hcpriv);
1060 #endif
1061
1062         spin_lock_irqsave (&ehci->lock, flags);
1063         if (unlikely(!test_bit(HCD_FLAG_HW_ACCESSIBLE,
1064                                &ehci_to_hcd(ehci)->flags))) {
1065                 rc = -ESHUTDOWN;
1066                 goto done;
1067         }
1068         rc = usb_hcd_link_urb_to_ep(ehci_to_hcd(ehci), urb);
1069         if (unlikely(rc))
1070                 goto done;
1071
1072         qh = qh_append_tds(ehci, urb, qtd_list, epnum, &urb->ep->hcpriv);
1073         if (unlikely(qh == NULL)) {
1074                 usb_hcd_unlink_urb_from_ep(ehci_to_hcd(ehci), urb);
1075                 rc = -ENOMEM;
1076                 goto done;
1077         }
1078
1079         /* Control/bulk operations through TTs don't need scheduling,
1080          * the HC and TT handle it when the TT has a buffer ready.
1081          */
1082         if (likely (qh->qh_state == QH_STATE_IDLE))
1083                 qh_link_async(ehci, qh);
1084  done:
1085         spin_unlock_irqrestore (&ehci->lock, flags);
1086         if (unlikely (qh == NULL))
1087                 qtd_list_free (ehci, urb, qtd_list);
1088         return rc;
1089 }
1090
1091 /*-------------------------------------------------------------------------*/
1092
1093 /* the async qh for the qtds being reclaimed are now unlinked from the HC */
1094
1095 static void end_unlink_async (struct ehci_hcd *ehci)
1096 {
1097         struct ehci_qh          *qh = ehci->reclaim;
1098         struct ehci_qh          *next;
1099
1100         iaa_watchdog_done(ehci);
1101
1102         // qh->hw_next = cpu_to_hc32(qh->qh_dma);
1103         qh->qh_state = QH_STATE_IDLE;
1104         qh->qh_next.qh = NULL;
1105         qh_put (qh);                    // refcount from reclaim
1106
1107         /* other unlink(s) may be pending (in QH_STATE_UNLINK_WAIT) */
1108         next = qh->reclaim;
1109         ehci->reclaim = next;
1110         qh->reclaim = NULL;
1111
1112         qh_completions (ehci, qh);
1113
1114         if (!list_empty (&qh->qtd_list)
1115                         && HC_IS_RUNNING (ehci_to_hcd(ehci)->state))
1116                 qh_link_async (ehci, qh);
1117         else {
1118                 /* it's not free to turn the async schedule on/off; leave it
1119                  * active but idle for a while once it empties.
1120                  */
1121                 if (HC_IS_RUNNING (ehci_to_hcd(ehci)->state)
1122                                 && ehci->async->qh_next.qh == NULL)
1123                         timer_action (ehci, TIMER_ASYNC_OFF);
1124         }
1125         qh_put(qh);                     /* refcount from async list */
1126
1127         if (next) {
1128                 ehci->reclaim = NULL;
1129                 start_unlink_async (ehci, next);
1130         }
1131 }
1132
1133 /* makes sure the async qh will become idle */
1134 /* caller must own ehci->lock */
1135
1136 static void start_unlink_async (struct ehci_hcd *ehci, struct ehci_qh *qh)
1137 {
1138         int             cmd = ehci_readl(ehci, &ehci->regs->command);
1139         struct ehci_qh  *prev;
1140
1141 #ifdef DEBUG
1142         assert_spin_locked(&ehci->lock);
1143         if (ehci->reclaim
1144                         || (qh->qh_state != QH_STATE_LINKED
1145                                 && qh->qh_state != QH_STATE_UNLINK_WAIT)
1146                         )
1147                 BUG ();
1148 #endif
1149
1150         /* stop async schedule right now? */
1151         if (unlikely (qh == ehci->async)) {
1152                 /* can't get here without STS_ASS set */
1153                 if (ehci_to_hcd(ehci)->state != HC_STATE_HALT
1154                                 && !ehci->reclaim) {
1155                         /* ... and CMD_IAAD clear */
1156                         ehci_writel(ehci, cmd & ~CMD_ASE,
1157                                     &ehci->regs->command);
1158                         wmb ();
1159                         // handshake later, if we need to
1160                         timer_action_done (ehci, TIMER_ASYNC_OFF);
1161                 }
1162                 return;
1163         }
1164
1165         qh->qh_state = QH_STATE_UNLINK;
1166         ehci->reclaim = qh = qh_get (qh);
1167
1168         prev = ehci->async;
1169         while (prev->qh_next.qh != qh)
1170                 prev = prev->qh_next.qh;
1171
1172         prev->hw_next = qh->hw_next;
1173         prev->qh_next = qh->qh_next;
1174         wmb ();
1175
1176         /* If the controller isn't running, we don't have to wait for it */
1177         if (unlikely(!HC_IS_RUNNING(ehci_to_hcd(ehci)->state))) {
1178                 /* if (unlikely (qh->reclaim != 0))
1179                  *      this will recurse, probably not much
1180                  */
1181                 end_unlink_async (ehci);
1182                 return;
1183         }
1184
1185         cmd |= CMD_IAAD;
1186         ehci_writel(ehci, cmd, &ehci->regs->command);
1187         (void)ehci_readl(ehci, &ehci->regs->command);
1188         iaa_watchdog_start(ehci);
1189 }
1190
1191 /*-------------------------------------------------------------------------*/
1192
1193 static void scan_async (struct ehci_hcd *ehci)
1194 {
1195         struct ehci_qh          *qh;
1196         enum ehci_timer_action  action = TIMER_IO_WATCHDOG;
1197
1198         ehci->stamp = ehci_readl(ehci, &ehci->regs->frame_index);
1199         timer_action_done (ehci, TIMER_ASYNC_SHRINK);
1200 rescan:
1201         qh = ehci->async->qh_next.qh;
1202         if (likely (qh != NULL)) {
1203                 do {
1204                         /* clean any finished work for this qh */
1205                         if (!list_empty (&qh->qtd_list)
1206                                         && qh->stamp != ehci->stamp) {
1207                                 int temp;
1208
1209                                 /* unlinks could happen here; completion
1210                                  * reporting drops the lock.  rescan using
1211                                  * the latest schedule, but don't rescan
1212                                  * qhs we already finished (no looping).
1213                                  */
1214                                 qh = qh_get (qh);
1215                                 qh->stamp = ehci->stamp;
1216                                 temp = qh_completions (ehci, qh);
1217                                 qh_put (qh);
1218                                 if (temp != 0) {
1219                                         goto rescan;
1220                                 }
1221                         }
1222
1223                         /* unlink idle entries, reducing DMA usage as well
1224                          * as HCD schedule-scanning costs.  delay for any qh
1225                          * we just scanned, there's a not-unusual case that it
1226                          * doesn't stay idle for long.
1227                          * (plus, avoids some kind of re-activation race.)
1228                          */
1229                         if (list_empty(&qh->qtd_list)
1230                                         && qh->qh_state == QH_STATE_LINKED) {
1231                                 if (!ehci->reclaim
1232                                         && ((ehci->stamp - qh->stamp) & 0x1fff)
1233                                                 >= (EHCI_SHRINK_FRAMES * 8))
1234                                         start_unlink_async(ehci, qh);
1235                                 else
1236                                         action = TIMER_ASYNC_SHRINK;
1237                         }
1238
1239                         qh = qh->qh_next.qh;
1240                 } while (qh);
1241         }
1242         if (action == TIMER_ASYNC_SHRINK)
1243                 timer_action (ehci, TIMER_ASYNC_SHRINK);
1244 }