/*
   * Copyright (C) 2001-2004 by David Brownell
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License as published by the
   * Free Software Foundation; either version 2 of the License, or (at your
   * option) any later version.
   *
   * This program is distributed in the hope that it will be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
   * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software Foundation,
   * Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   */
  
  /* this file is part of ehci-hcd.c */
  
  /*-------------------------------------------------------------------------*/
  
  /*
   * EHCI hardware queue manipulation ... the core.  QH/QTD manipulation.
   *
   * Control, bulk, and interrupt traffic all use "qh" lists.  They list "qtd"
   * entries describing USB transactions, max 16-20kB/entry (with 4kB-aligned
   * buffers needed for the larger number).  We use one QH per endpoint, queue
   * multiple urbs (all three types) per endpoint.  URBs may need several qtds.
   *
   * ISO traffic uses "ISO TD" (itd, and sitd) records, and (along with
   * interrupts) needs careful scheduling.  Performance improvements can be
   * an ongoing challenge.  That's in "ehci-sched.c".
   *
   * USB 1.1 devices are handled (a) by "companion" OHCI or UHCI root hubs,
   * or otherwise through transaction translators (TTs) in USB 2.0 hubs using
   * (b) special fields in qh entries or (c) split iso entries.  TTs will
   * buffer low/full speed data so the host collects it at high speed.
   */
  
  /*-------------------------------------------------------------------------*/
  
  /* fill a qtd, returning how much of the buffer we were able to queue up */
  
  static int
  qtd_fill(struct ehci_hcd *ehci, struct ehci_qtd *qtd, dma_addr_t buf,
  		  size_t len, int token, int maxpacket)
  {
  	int	i, count;
  	u64	addr = buf;
  
  	/* one buffer entry per 4K ... first might be short or unaligned */
  	qtd->hw_buf[0] = cpu_to_hc32(ehci, (u32)addr);
  	qtd->hw_buf_hi[0] = cpu_to_hc32(ehci, (u32)(addr >> 32));
  	count = 0x1000 - (buf & 0x0fff);	/* rest of that page */
  	if (likely (len < count))		/* ... iff needed */
  		count = len;
  	else {
  		buf +=  0x1000;
  		buf &= ~0x0fff;
  
  		/* per-qtd limit: from 16K to 20K (best alignment) */
  		for (i = 1; count < len && i < 5; i++) {
  			addr = buf;
  			qtd->hw_buf[i] = cpu_to_hc32(ehci, (u32)addr);
  			qtd->hw_buf_hi[i] = cpu_to_hc32(ehci,
  					(u32)(addr >> 32));
  			buf += 0x1000;
  			if ((count + 0x1000) < len)
  				count += 0x1000;
  			else
  				count = len;
  		}
  
  		/* short packets may only terminate transfers */
  		if (count != len)
  			count -= (count % maxpacket);
  	}
  	qtd->hw_token = cpu_to_hc32(ehci, (count << 16) | token);
  	qtd->length = count;
  
  	return count;
  }
  
  /*-------------------------------------------------------------------------*/
  
  static inline void
  qh_update (struct ehci_hcd *ehci, struct ehci_qh *qh, struct ehci_qtd *qtd)
  {
  	struct ehci_qh_hw *hw = qh->hw;
  
  	/* writes to an active overlay are unsafe */
  	WARN_ON(qh->qh_state != QH_STATE_IDLE);
  
  	hw->hw_qtd_next = QTD_NEXT(ehci, qtd->qtd_dma);
  	hw->hw_alt_next = EHCI_LIST_END(ehci);
  
  	/* Except for control endpoints, we make hardware maintain data
  	 * toggle (like OHCI) ... here (re)initialize the toggle in the QH,
  	 * and set the pseudo-toggle in udev. Only usb_clear_halt() will
  	 * ever clear it.
  	 */
  	if (!(hw->hw_info1 & cpu_to_hc32(ehci, QH_TOGGLE_CTL))) {
  		unsigned	is_out, epnum;
  
  		is_out = qh->is_out;
  		epnum = (hc32_to_cpup(ehci, &hw->hw_info1) >> 8) & 0x0f;
  		if (unlikely(!usb_gettoggle(qh->ps.udev, epnum, is_out))) {
  			hw->hw_token &= ~cpu_to_hc32(ehci, QTD_TOGGLE);
  			usb_settoggle(qh->ps.udev, epnum, is_out, 1);
  		}
  	}
  
  	hw->hw_token &= cpu_to_hc32(ehci, QTD_TOGGLE | QTD_STS_PING);
  }
  
  /* if it weren't for a common silicon quirk (writing the dummy into the qh
   * overlay, so qh->hw_token wrongly becomes inactive/halted), only fault
   * recovery (including urb dequeue) would need software changes to a QH...
   */
  static void
  qh_refresh (struct ehci_hcd *ehci, struct ehci_qh *qh)
  {
  	struct ehci_qtd *qtd;
  
  	qtd = list_entry(qh->qtd_list.next, struct ehci_qtd, qtd_list);
  
  	/*
  	 * first qtd may already be partially processed.
  	 * If we come here during unlink, the QH overlay region
  	 * might have reference to the just unlinked qtd. The
  	 * qtd is updated in qh_completions(). Update the QH
  	 * overlay here.
  	 */
  	if (qh->hw->hw_token & ACTIVE_BIT(ehci))
  		qh->hw->hw_qtd_next = qtd->hw_next;
  	else
  		qh_update(ehci, qh, qtd);
  }
  
  /*-------------------------------------------------------------------------*/
  
  static void qh_link_async(struct ehci_hcd *ehci, struct ehci_qh *qh);
  
  static void ehci_clear_tt_buffer_complete(struct usb_hcd *hcd,
  		struct usb_host_endpoint *ep)
  {
  	struct ehci_hcd		*ehci = hcd_to_ehci(hcd);
  	struct ehci_qh		*qh = ep->hcpriv;
  	unsigned long		flags;
  
  	spin_lock_irqsave(&ehci->lock, flags);
  	qh->clearing_tt = 0;
  	if (qh->qh_state == QH_STATE_IDLE && !list_empty(&qh->qtd_list)
  			&& ehci->rh_state == EHCI_RH_RUNNING)
  		qh_link_async(ehci, qh);
  	spin_unlock_irqrestore(&ehci->lock, flags);
  }
  
  static void ehci_clear_tt_buffer(struct ehci_hcd *ehci, struct ehci_qh *qh,
  		struct urb *urb, u32 token)
  {
  
  	/* If an async split transaction gets an error or is unlinked,
  	 * the TT buffer may be left in an indeterminate state.  We
  	 * have to clear the TT buffer.
  	 *
  	 * Note: this routine is never called for Isochronous transfers.
  	 */
  	if (urb->dev->tt && !usb_pipeint(urb->pipe) && !qh->clearing_tt) {
  #ifdef CONFIG_DYNAMIC_DEBUG
  		struct usb_device *tt = urb->dev->tt->hub;
  		dev_dbg(&tt->dev,
  			"clear tt buffer port %d, a%d ep%d t%08x
  ",
  			urb->dev->ttport, urb->dev->devnum,
  			usb_pipeendpoint(urb->pipe), token);
  #endif /* CONFIG_DYNAMIC_DEBUG */
  		if (!ehci_is_TDI(ehci)
  				|| urb->dev->tt->hub !=
  				   ehci_to_hcd(ehci)->self.root_hub) {
  			if (usb_hub_clear_tt_buffer(urb) == 0)
  				qh->clearing_tt = 1;
  		} else {
  
  			/* REVISIT ARC-derived cores don't clear the root
  			 * hub TT buffer in this way...
  			 */
  		}
  	}
  }
  
  static int qtd_copy_status (
  	struct ehci_hcd *ehci,
  	struct urb *urb,
  	size_t length,
  	u32 token
  )
  {
  	int	status = -EINPROGRESS;
  
  	/* count IN/OUT bytes, not SETUP (even short packets) */
  	if (likely (QTD_PID (token) != 2))
  		urb->actual_length += length - QTD_LENGTH (token);
  
  	/* don't modify error codes */
  	if (unlikely(urb->unlinked))
  		return status;
  
  	/* force cleanup after short read; not always an error */
  	if (unlikely (IS_SHORT_READ (token)))
  		status = -EREMOTEIO;
  
  	/* serious "can't proceed" faults reported by the hardware */
  	if (token & QTD_STS_HALT) {
  		if (token & QTD_STS_BABBLE) {
  			/* FIXME "must" disable babbling device's port too */
  			status = -EOVERFLOW;
  		/* CERR nonzero + halt --> stall */
  		} else if (QTD_CERR(token)) {
  			status = -EPIPE;
  
  		/* In theory, more than one of the following bits can be set
  		 * since they are sticky and the transaction is retried.
  		 * Which to test first is rather arbitrary.
  		 */
  		} else if (token & QTD_STS_MMF) {
  			/* fs/ls interrupt xfer missed the complete-split */
  			status = -EPROTO;
  		} else if (token & QTD_STS_DBE) {
  			status = (QTD_PID (token) == 1) /* IN ? */
  				? -ENOSR  /* hc couldn't read data */
  				: -ECOMM; /* hc couldn't write data */
  		} else if (token & QTD_STS_XACT) {
  			/* timeout, bad CRC, wrong PID, etc */
  			ehci_dbg(ehci, "devpath %s ep%d%s 3strikes
  ",
  				urb->dev->devpath,
  				usb_pipeendpoint(urb->pipe),
  				usb_pipein(urb->pipe) ? "in" : "out");
  			status = -EPROTO;
  		} else {	/* unknown */
  			status = -EPROTO;
  		}
  	}
  
  	return status;
  }
  
  static void
  ehci_urb_done(struct ehci_hcd *ehci, struct urb *urb, int status)
  {
  	if (usb_pipetype(urb->pipe) == PIPE_INTERRUPT) {
  		/* ... update hc-wide periodic stats */
  		ehci_to_hcd(ehci)->self.bandwidth_int_reqs--;
  	}
  
  	if (unlikely(urb->unlinked)) {
  		COUNT(ehci->stats.unlink);
  	} else {
  		/* report non-error and short read status as zero */
  		if (status == -EINPROGRESS || status == -EREMOTEIO)
  			status = 0;
  		COUNT(ehci->stats.complete);
  	}
  
  #ifdef EHCI_URB_TRACE
  	ehci_dbg (ehci,
  		"%s %s urb %p ep%d%s status %d len %d/%d
  ",
  		__func__, urb->dev->devpath, urb,
  		usb_pipeendpoint (urb->pipe),
  		usb_pipein (urb->pipe) ? "in" : "out",
  		status,
  		urb->actual_length, urb->transfer_buffer_length);
  #endif
  
  	usb_hcd_unlink_urb_from_ep(ehci_to_hcd(ehci), urb);
  	usb_hcd_giveback_urb(ehci_to_hcd(ehci), urb, status);
  }
  
  static int qh_schedule (struct ehci_hcd *ehci, struct ehci_qh *qh);
  
  /*
   * Process and free completed qtds for a qh, returning URBs to drivers.
   * Chases up to qh->hw_current.  Returns nonzero if the caller should
   * unlink qh.
   */
  static unsigned
  qh_completions (struct ehci_hcd *ehci, struct ehci_qh *qh)
  {
  	struct ehci_qtd		*last, *end = qh->dummy;
  	struct list_head	*entry, *tmp;
  	int			last_status;
  	int			stopped;
  	u8			state;
  	struct ehci_qh_hw	*hw = qh->hw;
  
  	/* completions (or tasks on other cpus) must never clobber HALT
  	 * till we've gone through and cleaned everything up, even when
  	 * they add urbs to this qh's queue or mark them for unlinking.
  	 *
  	 * NOTE:  unlinking expects to be done in queue order.
  	 *
  	 * It's a bug for qh->qh_state to be anything other than
  	 * QH_STATE_IDLE, unless our caller is scan_async() or
  	 * scan_intr().
  	 */
  	state = qh->qh_state;
  	qh->qh_state = QH_STATE_COMPLETING;
  	stopped = (state == QH_STATE_IDLE);
  
   rescan:
  	last = NULL;
  	last_status = -EINPROGRESS;
  	qh->dequeue_during_giveback = 0;
  
  	/* remove de-activated QTDs from front of queue.
  	 * after faults (including short reads), cleanup this urb
  	 * then let the queue advance.
  	 * if queue is stopped, handles unlinks.
  	 */
  	list_for_each_safe (entry, tmp, &qh->qtd_list) {
  		struct ehci_qtd	*qtd;
  		struct urb	*urb;
  		u32		token = 0;
  
  		qtd = list_entry (entry, struct ehci_qtd, qtd_list);
  		urb = qtd->urb;
  
  		/* clean up any state from previous QTD ...*/
  		if (last) {
  			if (likely (last->urb != urb)) {
  				ehci_urb_done(ehci, last->urb, last_status);
  				last_status = -EINPROGRESS;
  			}
  			ehci_qtd_free (ehci, last);
  			last = NULL;
  		}
  
  		/* ignore urbs submitted during completions we reported */
  		if (qtd == end)
  			break;
  
  		/* hardware copies qtd out of qh overlay */
  		rmb ();
  		token = hc32_to_cpu(ehci, qtd->hw_token);
  
  		/* always clean up qtds the hc de-activated */
   retry_xacterr:
  		if ((token & QTD_STS_ACTIVE) == 0) {
  
  			/* Report Data Buffer Error: non-fatal but useful */
  			if (token & QTD_STS_DBE)
  				ehci_dbg(ehci,
  					"detected DataBufferErr for urb %p ep%d%s len %d, qtd %p [qh %p]
  ",
  					urb,
  					usb_endpoint_num(&urb->ep->desc),
  					usb_endpoint_dir_in(&urb->ep->desc) ? "in" : "out",
  					urb->transfer_buffer_length,
  					qtd,
  					qh);
  
  			/* on STALL, error, and short reads this urb must
  			 * complete and all its qtds must be recycled.
  			 */
  			if ((token & QTD_STS_HALT) != 0) {
  
  				/* retry transaction errors until we
  				 * reach the software xacterr limit
  				 */
  				if ((token & QTD_STS_XACT) &&
  						QTD_CERR(token) == 0 &&
  						++qh->xacterrs < QH_XACTERR_MAX &&
  						!urb->unlinked) {
  					ehci_dbg(ehci,
  	"detected XactErr len %zu/%zu retry %d
  ",
  	qtd->length - QTD_LENGTH(token), qtd->length, qh->xacterrs);
  
  					/* reset the token in the qtd and the
  					 * qh overlay (which still contains
  					 * the qtd) so that we pick up from
  					 * where we left off
  					 */
  					token &= ~QTD_STS_HALT;
  					token |= QTD_STS_ACTIVE |
  							(EHCI_TUNE_CERR << 10);
  					qtd->hw_token = cpu_to_hc32(ehci,
  							token);
  					wmb();
  					hw->hw_token = cpu_to_hc32(ehci,
  							token);
  					goto retry_xacterr;
  				}
  				stopped = 1;
  
  			/* magic dummy for some short reads; qh won't advance.
  			 * that silicon quirk can kick in with this dummy too.
  			 *
  			 * other short reads won't stop the queue, including
  			 * control transfers (status stage handles that) or
  			 * most other single-qtd reads ... the queue stops if
  			 * URB_SHORT_NOT_OK was set so the driver submitting
  			 * the urbs could clean it up.
  			 */
  			} else if (IS_SHORT_READ (token)
  					&& !(qtd->hw_alt_next
  						& EHCI_LIST_END(ehci))) {
  				stopped = 1;
  			}
  
  		/* stop scanning when we reach qtds the hc is using */
  		} else if (likely (!stopped
  				&& ehci->rh_state >= EHCI_RH_RUNNING)) {
  			break;
  
  		/* scan the whole queue for unlinks whenever it stops */
  		} else {
  			stopped = 1;
  
  			/* cancel everything if we halt, suspend, etc */
  			if (ehci->rh_state < EHCI_RH_RUNNING)
  				last_status = -ESHUTDOWN;
  
  			/* this qtd is active; skip it unless a previous qtd
  			 * for its urb faulted, or its urb was canceled.
  			 */
  			else if (last_status == -EINPROGRESS && !urb->unlinked)
  				continue;
  
  			/*
  			 * If this was the active qtd when the qh was unlinked
  			 * and the overlay's token is active, then the overlay
  			 * hasn't been written back to the qtd yet so use its
  			 * token instead of the qtd's.  After the qtd is
  			 * processed and removed, the overlay won't be valid
  			 * any more.
  			 */
  			if (state == QH_STATE_IDLE &&
  					qh->qtd_list.next == &qtd->qtd_list &&
  					(hw->hw_token & ACTIVE_BIT(ehci))) {
  				token = hc32_to_cpu(ehci, hw->hw_token);
  				hw->hw_token &= ~ACTIVE_BIT(ehci);
  
  				/* An unlink may leave an incomplete
  				 * async transaction in the TT buffer.
  				 * We have to clear it.
  				 */
  				ehci_clear_tt_buffer(ehci, qh, urb, token);
  			}
  		}
  
  		/* unless we already know the urb's status, collect qtd status
  		 * and update count of bytes transferred.  in common short read
  		 * cases with only one data qtd (including control transfers),
  		 * queue processing won't halt.  but with two or more qtds (for
  		 * example, with a 32 KB transfer), when the first qtd gets a
  		 * short read the second must be removed by hand.
  		 */
  		if (last_status == -EINPROGRESS) {
  			last_status = qtd_copy_status(ehci, urb,
  					qtd->length, token);
  			if (last_status == -EREMOTEIO
  					&& (qtd->hw_alt_next
  						& EHCI_LIST_END(ehci)))
  				last_status = -EINPROGRESS;
  
  			/* As part of low/full-speed endpoint-halt processing
  			 * we must clear the TT buffer (11.17.5).
  			 */
  			if (unlikely(last_status != -EINPROGRESS &&
  					last_status != -EREMOTEIO)) {
  				/* The TT's in some hubs malfunction when they
  				 * receive this request following a STALL (they
  				 * stop sending isochronous packets).  Since a
  				 * STALL can't leave the TT buffer in a busy
  				 * state (if you believe Figures 11-48 - 11-51
  				 * in the USB 2.0 spec), we won't clear the TT
  				 * buffer in this case.  Strictly speaking this
  				 * is a violation of the spec.
  				 */
  				if (last_status != -EPIPE)
  					ehci_clear_tt_buffer(ehci, qh, urb,
  							token);
  			}
  		}
  
  		/* if we're removing something not at the queue head,
  		 * patch the hardware queue pointer.
  		 */
  		if (stopped && qtd->qtd_list.prev != &qh->qtd_list) {
  			last = list_entry (qtd->qtd_list.prev,
  					struct ehci_qtd, qtd_list);
  			last->hw_next = qtd->hw_next;
  		}
  
  		/* remove qtd; it's recycled after possible urb completion */
  		list_del (&qtd->qtd_list);
  		last = qtd;
  
  		/* reinit the xacterr counter for the next qtd */
  		qh->xacterrs = 0;
  	}
  
  	/* last urb's completion might still need calling */
  	if (likely (last != NULL)) {
  		ehci_urb_done(ehci, last->urb, last_status);
  		ehci_qtd_free (ehci, last);
  	}
  
  	/* Do we need to rescan for URBs dequeued during a giveback? */
  	if (unlikely(qh->dequeue_during_giveback)) {
  		/* If the QH is already unlinked, do the rescan now. */
  		if (state == QH_STATE_IDLE)
  			goto rescan;
  
  		/* Otherwise the caller must unlink the QH. */
  	}
  
  	/* restore original state; caller must unlink or relink */
  	qh->qh_state = state;
  
  	/* be sure the hardware's done with the qh before refreshing
  	 * it after fault cleanup, or recovering from silicon wrongly
  	 * overlaying the dummy qtd (which reduces DMA chatter).
  	 *
  	 * We won't refresh a QH that's linked (after the HC
  	 * stopped the queue).  That avoids a race:
  	 *  - HC reads first part of QH;
  	 *  - CPU updates that first part and the token;
  	 *  - HC reads rest of that QH, including token
  	 * Result:  HC gets an inconsistent image, and then
  	 * DMAs to/from the wrong memory (corrupting it).
  	 *
  	 * That should be rare for interrupt transfers,
  	 * except maybe high bandwidth ...
  	 */
  	if (stopped != 0 || hw->hw_qtd_next == EHCI_LIST_END(ehci))
  		qh->exception = 1;
  
  	/* Let the caller know if the QH needs to be unlinked. */
  	return qh->exception;
  }
  
  /*-------------------------------------------------------------------------*/
  
  // high bandwidth multiplier, as encoded in highspeed endpoint descriptors
  #define hb_mult(wMaxPacketSize) (1 + (((wMaxPacketSize) >> 11) & 0x03))
  // ... and packet size, for any kind of endpoint descriptor
  #define max_packet(wMaxPacketSize) ((wMaxPacketSize) & 0x07ff)
  
  /*
   * reverse of qh_urb_transaction:  free a list of TDs.
   * used for cleanup after errors, before HC sees an URB's TDs.
   */
  static void qtd_list_free (
  	struct ehci_hcd		*ehci,
  	struct urb		*urb,
  	struct list_head	*qtd_list
  ) {
  	struct list_head	*entry, *temp;
  
  	list_for_each_safe (entry, temp, qtd_list) {
  		struct ehci_qtd	*qtd;
  
  		qtd = list_entry (entry, struct ehci_qtd, qtd_list);
  		list_del (&qtd->qtd_list);
  		ehci_qtd_free (ehci, qtd);
  	}
  }
  
  /*
   * create a list of filled qtds for this URB; won't link into qh.
   */
  static struct list_head *
  qh_urb_transaction (
  	struct ehci_hcd		*ehci,
  	struct urb		*urb,
  	struct list_head	*head,
  	gfp_t			flags
  ) {
  	struct ehci_qtd		*qtd, *qtd_prev;
  	dma_addr_t		buf;
  	int			len, this_sg_len, maxpacket;
  	int			is_input;
  	u32			token;
  	int			i;
  	struct scatterlist	*sg;
  
  	/*
  	 * URBs map to sequences of QTDs:  one logical transaction
  	 */
  	qtd = ehci_qtd_alloc (ehci, flags);
  	if (unlikely (!qtd))
  		return NULL;
  	list_add_tail (&qtd->qtd_list, head);
  	qtd->urb = urb;
  
  	token = QTD_STS_ACTIVE;
  	token |= (EHCI_TUNE_CERR << 10);
  	/* for split transactions, SplitXState initialized to zero */
  
  	len = urb->transfer_buffer_length;
  	is_input = usb_pipein (urb->pipe);
  	if (usb_pipecontrol (urb->pipe)) {
  		/* SETUP pid */
  		qtd_fill(ehci, qtd, urb->setup_dma,
  				sizeof (struct usb_ctrlrequest),
  				token | (2 /* "setup" */ << 8), 8);
  
  		/* ... and always at least one more pid */
  		token ^= QTD_TOGGLE;
  		qtd_prev = qtd;
  		qtd = ehci_qtd_alloc (ehci, flags);
  		if (unlikely (!qtd))
  			goto cleanup;
  		qtd->urb = urb;
  		qtd_prev->hw_next = QTD_NEXT(ehci, qtd->qtd_dma);
  		list_add_tail (&qtd->qtd_list, head);
  
  		/* for zero length DATA stages, STATUS is always IN */
  		if (len == 0)
  			token |= (1 /* "in" */ << 8);
  	}
  
  	/*
  	 * data transfer stage:  buffer setup
  	 */
  	i = urb->num_mapped_sgs;
  	if (len > 0 && i > 0) {
  		sg = urb->sg;
  		buf = sg_dma_address(sg);
  
  		/* urb->transfer_buffer_length may be smaller than the
  		 * size of the scatterlist (or vice versa)
  		 */
  		this_sg_len = min_t(int, sg_dma_len(sg), len);
  	} else {
  		sg = NULL;
  		buf = urb->transfer_dma;
  		this_sg_len = len;
  	}
  
  	if (is_input)
  		token |= (1 /* "in" */ << 8);
  	/* else it's already initted to "out" pid (0 << 8) */
  
  	maxpacket = max_packet(usb_maxpacket(urb->dev, urb->pipe, !is_input));
  
  	/*
  	 * buffer gets wrapped in one or more qtds;
  	 * last one may be "short" (including zero len)
  	 * and may serve as a control status ack
  	 */
  	for (;;) {
  		int this_qtd_len;
  
  		this_qtd_len = qtd_fill(ehci, qtd, buf, this_sg_len, token,
  				maxpacket);
  		this_sg_len -= this_qtd_len;
  		len -= this_qtd_len;
  		buf += this_qtd_len;
  
  		/*
  		 * short reads advance to a "magic" dummy instead of the next
  		 * qtd ... that forces the queue to stop, for manual cleanup.
  		 * (this will usually be overridden later.)
  		 */
  		if (is_input)
  			qtd->hw_alt_next = ehci->async->hw->hw_alt_next;
  
  		/* qh makes control packets use qtd toggle; maybe switch it */
  		if ((maxpacket & (this_qtd_len + (maxpacket - 1))) == 0)
  			token ^= QTD_TOGGLE;
  
  		if (likely(this_sg_len <= 0)) {
  			if (--i <= 0 || len <= 0)
  				break;
  			sg = sg_next(sg);
  			buf = sg_dma_address(sg);
  			this_sg_len = min_t(int, sg_dma_len(sg), len);
  		}
  
  		qtd_prev = qtd;
  		qtd = ehci_qtd_alloc (ehci, flags);
  		if (unlikely (!qtd))
  			goto cleanup;
  		qtd->urb = urb;
  		qtd_prev->hw_next = QTD_NEXT(ehci, qtd->qtd_dma);
  		list_add_tail (&qtd->qtd_list, head);
  	}
  
  	/*
  	 * unless the caller requires manual cleanup after short reads,
  	 * have the alt_next mechanism keep the queue running after the
  	 * last data qtd (the only one, for control and most other cases).
  	 */
  	if (likely ((urb->transfer_flags & URB_SHORT_NOT_OK) == 0
  				|| usb_pipecontrol (urb->pipe)))
  		qtd->hw_alt_next = EHCI_LIST_END(ehci);
  
  	/*
  	 * control requests may need a terminating data "status" ack;
  	 * other OUT ones may need a terminating short packet
  	 * (zero length).
  	 */
  	if (likely (urb->transfer_buffer_length != 0)) {
  		int	one_more = 0;
  
  		if (usb_pipecontrol (urb->pipe)) {
  			one_more = 1;
  			token ^= 0x0100;	/* "in" <--> "out"  */
  			token |= QTD_TOGGLE;	/* force DATA1 */
  		} else if (usb_pipeout(urb->pipe)
  				&& (urb->transfer_flags & URB_ZERO_PACKET)
  				&& !(urb->transfer_buffer_length % maxpacket)) {
  			one_more = 1;
  		}
  		if (one_more) {
  			qtd_prev = qtd;
  			qtd = ehci_qtd_alloc (ehci, flags);
  			if (unlikely (!qtd))
  				goto cleanup;
  			qtd->urb = urb;
  			qtd_prev->hw_next = QTD_NEXT(ehci, qtd->qtd_dma);
  			list_add_tail (&qtd->qtd_list, head);
  
  			/* never any data in such packets */
  			qtd_fill(ehci, qtd, 0, 0, token, 0);
  		}
  	}
  
  	/* by default, enable interrupt on urb completion */
  	if (likely (!(urb->transfer_flags & URB_NO_INTERRUPT)))
  		qtd->hw_token |= cpu_to_hc32(ehci, QTD_IOC);
  	return head;
  
  cleanup:
  	qtd_list_free (ehci, urb, head);
  	return NULL;
  }
  
  /*-------------------------------------------------------------------------*/
  
  // Would be best to create all qh's from config descriptors,
  // when each interface/altsetting is established.  Unlink
  // any previous qh and cancel its urbs first; endpoints are
  // implicitly reset then (data toggle too).
  // That'd mean updating how usbcore talks to HCDs. (2.7?)
  
  
  /*
   * Each QH holds a qtd list; a QH is used for everything except iso.
   *
   * For interrupt urbs, the scheduler must set the microframe scheduling
   * mask(s) each time the QH gets scheduled.  For highspeed, that's
   * just one microframe in the s-mask.  For split interrupt transactions
   * there are additional complications: c-mask, maybe FSTNs.
   */
  static struct ehci_qh *
  qh_make (
  	struct ehci_hcd		*ehci,
  	struct urb		*urb,
  	gfp_t			flags
  ) {
  	struct ehci_qh		*qh = ehci_qh_alloc (ehci, flags);
  	u32			info1 = 0, info2 = 0;
  	int			is_input, type;
  	int			maxp = 0;
  	struct usb_tt		*tt = urb->dev->tt;
  	struct ehci_qh_hw	*hw;
  
  	if (!qh)
  		return qh;
  
  	/*
  	 * init endpoint/device data for this QH
  	 */
  	info1 |= usb_pipeendpoint (urb->pipe) << 8;
  	info1 |= usb_pipedevice (urb->pipe) << 0;
  
  	is_input = usb_pipein (urb->pipe);
  	type = usb_pipetype (urb->pipe);
  	maxp = usb_maxpacket (urb->dev, urb->pipe, !is_input);
  
  	/* 1024 byte maxpacket is a hardware ceiling.  High bandwidth
  	 * acts like up to 3KB, but is built from smaller packets.
  	 */
  	if (max_packet(maxp) > 1024) {
  		ehci_dbg(ehci, "bogus qh maxpacket %d
  ", max_packet(maxp));
  		goto done;
  	}
  
  	/* Compute interrupt scheduling parameters just once, and save.
  	 * - allowing for high bandwidth, how many nsec/uframe are used?
  	 * - split transactions need a second CSPLIT uframe; same question
  	 * - splits also need a schedule gap (for full/low speed I/O)
  	 * - qh has a polling interval
  	 *
  	 * For control/bulk requests, the HC or TT handles these.
  	 */
  	if (type == PIPE_INTERRUPT) {
  		unsigned	tmp;
  
  		qh->ps.usecs = NS_TO_US(usb_calc_bus_time(USB_SPEED_HIGH,
  				is_input, 0,
  				hb_mult(maxp) * max_packet(maxp)));
  		qh->ps.phase = NO_FRAME;
  
  		if (urb->dev->speed == USB_SPEED_HIGH) {
  			qh->ps.c_usecs = 0;
  			qh->gap_uf = 0;
  
  			if (urb->interval > 1 && urb->interval < 8) {
  				/* NOTE interval 2 or 4 uframes could work.
  				 * But interval 1 scheduling is simpler, and
  				 * includes high bandwidth.
  				 */
  				urb->interval = 1;
  			} else if (urb->interval > ehci->periodic_size << 3) {
  				urb->interval = ehci->periodic_size << 3;
  			}
  			qh->ps.period = urb->interval >> 3;
  
  			/* period for bandwidth allocation */
  			tmp = min_t(unsigned, EHCI_BANDWIDTH_SIZE,
  					1 << (urb->ep->desc.bInterval - 1));
  
  			/* Allow urb->interval to override */
  			qh->ps.bw_uperiod = min_t(unsigned, tmp, urb->interval);
  			qh->ps.bw_period = qh->ps.bw_uperiod >> 3;
  		} else {
  			int		think_time;
  
  			/* gap is f(FS/LS transfer times) */
  			qh->gap_uf = 1 + usb_calc_bus_time (urb->dev->speed,
  					is_input, 0, maxp) / (125 * 1000);
  
  			/* FIXME this just approximates SPLIT/CSPLIT times */
  			if (is_input) {		// SPLIT, gap, CSPLIT+DATA
  				qh->ps.c_usecs = qh->ps.usecs + HS_USECS(0);
  				qh->ps.usecs = HS_USECS(1);
  			} else {		// SPLIT+DATA, gap, CSPLIT
  				qh->ps.usecs += HS_USECS(1);
  				qh->ps.c_usecs = HS_USECS(0);
  			}
  
  			think_time = tt ? tt->think_time : 0;
  			qh->ps.tt_usecs = NS_TO_US(think_time +
  					usb_calc_bus_time (urb->dev->speed,
  					is_input, 0, max_packet (maxp)));
  			if (urb->interval > ehci->periodic_size)
  				urb->interval = ehci->periodic_size;
  			qh->ps.period = urb->interval;
  
  			/* period for bandwidth allocation */
  			tmp = min_t(unsigned, EHCI_BANDWIDTH_FRAMES,
  					urb->ep->desc.bInterval);
  			tmp = rounddown_pow_of_two(tmp);
  
  			/* Allow urb->interval to override */
  			qh->ps.bw_period = min_t(unsigned, tmp, urb->interval);
  			qh->ps.bw_uperiod = qh->ps.bw_period << 3;
  		}
  	}
  
  	/* support for tt scheduling, and access to toggles */
  	qh->ps.udev = urb->dev;
  	qh->ps.ep = urb->ep;
  
  	/* using TT? */
  	switch (urb->dev->speed) {
  	case USB_SPEED_LOW:
  		info1 |= QH_LOW_SPEED;
  		/* FALL THROUGH */
  
  	case USB_SPEED_FULL:
  		/* EPS 0 means "full" */
  		if (type != PIPE_INTERRUPT)
  			info1 |= (EHCI_TUNE_RL_TT << 28);
  		if (type == PIPE_CONTROL) {
  			info1 |= QH_CONTROL_EP;		/* for TT */
  			info1 |= QH_TOGGLE_CTL;		/* toggle from qtd */
  		}
  		info1 |= maxp << 16;
  
  		info2 |= (EHCI_TUNE_MULT_TT << 30);
  
  		/* Some Freescale processors have an erratum in which the
  		 * port number in the queue head was 0..N-1 instead of 1..N.
  		 */
  		if (ehci_has_fsl_portno_bug(ehci))
  			info2 |= (urb->dev->ttport-1) << 23;
  		else
  			info2 |= urb->dev->ttport << 23;
  
  		/* set the address of the TT; for TDI's integrated
  		 * root hub tt, leave it zeroed.
  		 */
  		if (tt && tt->hub != ehci_to_hcd(ehci)->self.root_hub)
  			info2 |= tt->hub->devnum << 16;
  
  		/* NOTE:  if (PIPE_INTERRUPT) { scheduler sets c-mask } */
  
  		break;
  
  	case USB_SPEED_HIGH:		/* no TT involved */
  		info1 |= QH_HIGH_SPEED;
  		if (type == PIPE_CONTROL) {
  			info1 |= (EHCI_TUNE_RL_HS << 28);
  			info1 |= 64 << 16;	/* usb2 fixed maxpacket */
  			info1 |= QH_TOGGLE_CTL;	/* toggle from qtd */
  			info2 |= (EHCI_TUNE_MULT_HS << 30);
  		} else if (type == PIPE_BULK) {
  			info1 |= (EHCI_TUNE_RL_HS << 28);
  			/* The USB spec says that high speed bulk endpoints
  			 * always use 512 byte maxpacket.  But some device
  			 * vendors decided to ignore that, and MSFT is happy
  			 * to help them do so.  So now people expect to use
  			 * such nonconformant devices with Linux too; sigh.
  			 */
  			info1 |= max_packet(maxp) << 16;
  			info2 |= (EHCI_TUNE_MULT_HS << 30);
  		} else {		/* PIPE_INTERRUPT */
  			info1 |= max_packet (maxp) << 16;
  			info2 |= hb_mult (maxp) << 30;
  		}
  		break;
  	default:
  		ehci_dbg(ehci, "bogus dev %p speed %d
  ", urb->dev,
  			urb->dev->speed);
  done:
  		qh_destroy(ehci, qh);
  		return NULL;
  	}
  
  	/* NOTE:  if (PIPE_INTERRUPT) { scheduler sets s-mask } */
  
  	/* init as live, toggle clear */
  	qh->qh_state = QH_STATE_IDLE;
  	hw = qh->hw;
  	hw->hw_info1 = cpu_to_hc32(ehci, info1);
  	hw->hw_info2 = cpu_to_hc32(ehci, info2);
  	qh->is_out = !is_input;
  	usb_settoggle (urb->dev, usb_pipeendpoint (urb->pipe), !is_input, 1);
  	return qh;
  }
  
  /*-------------------------------------------------------------------------*/
  
  static void enable_async(struct ehci_hcd *ehci)
  {
  	if (ehci->async_count++)
  		return;
  
  	/* Stop waiting to turn off the async schedule */
  	ehci->enabled_hrtimer_events &= ~BIT(EHCI_HRTIMER_DISABLE_ASYNC);
  
  	/* Don't start the schedule until ASS is 0 */
  	ehci_poll_ASS(ehci);
  	turn_on_io_watchdog(ehci);
  }
  
  static void disable_async(struct ehci_hcd *ehci)
  {
  	if (--ehci->async_count)
  		return;
  
  	/* The async schedule and unlink lists are supposed to be empty */
  	WARN_ON(ehci->async->qh_next.qh || !list_empty(&ehci->async_unlink) ||
  			!list_empty(&ehci->async_idle));
  
  	/* Don't turn off the schedule until ASS is 1 */
  	ehci_poll_ASS(ehci);
  }
  
  /* move qh (and its qtds) onto async queue; maybe enable queue.  */
  
  static void qh_link_async (struct ehci_hcd *ehci, struct ehci_qh *qh)
  {
  	__hc32		dma = QH_NEXT(ehci, qh->qh_dma);
  	struct ehci_qh	*head;
  
  	/* Don't link a QH if there's a Clear-TT-Buffer pending */
  	if (unlikely(qh->clearing_tt))
  		return;
  
  	WARN_ON(qh->qh_state != QH_STATE_IDLE);
  
  	/* clear halt and/or toggle; and maybe recover from silicon quirk */
  	qh_refresh(ehci, qh);
  
  	/* splice right after start */
  	head = ehci->async;
  	qh->qh_next = head->qh_next;
  	qh->hw->hw_next = head->hw->hw_next;
  	wmb ();
  
  	head->qh_next.qh = qh;
  	head->hw->hw_next = dma;
  
  	qh->qh_state = QH_STATE_LINKED;
  	qh->xacterrs = 0;
  	qh->exception = 0;
  	/* qtd completions reported later by interrupt */
  
  	enable_async(ehci);
  }
  
  /*-------------------------------------------------------------------------*/
  
  /*
   * For control/bulk/interrupt, return QH with these TDs appended.
   * Allocates and initializes the QH if necessary.
   * Returns null if it can't allocate a QH it needs to.
   * If the QH has TDs (urbs) already, that's great.
   */
  static struct ehci_qh *qh_append_tds (
  	struct ehci_hcd		*ehci,
  	struct urb		*urb,
  	struct list_head	*qtd_list,
  	int			epnum,
  	void			**ptr
  )
  {
  	struct ehci_qh		*qh = NULL;
  	__hc32			qh_addr_mask = cpu_to_hc32(ehci, 0x7f);
  
  	qh = (struct ehci_qh *) *ptr;
  	if (unlikely (qh == NULL)) {
  		/* can't sleep here, we have ehci->lock... */
  		qh = qh_make (ehci, urb, GFP_ATOMIC);
  		*ptr = qh;
  	}
  	if (likely (qh != NULL)) {
  		struct ehci_qtd	*qtd;
  
  		if (unlikely (list_empty (qtd_list)))
  			qtd = NULL;
  		else
  			qtd = list_entry (qtd_list->next, struct ehci_qtd,
  					qtd_list);
  
  		/* control qh may need patching ... */
  		if (unlikely (epnum == 0)) {
  
                          /* usb_reset_device() briefly reverts to address 0 */
                          if (usb_pipedevice (urb->pipe) == 0)
  				qh->hw->hw_info1 &= ~qh_addr_mask;
  		}
  
  		/* just one way to queue requests: swap with the dummy qtd.
  		 * only hc or qh_refresh() ever modify the overlay.
  		 */
  		if (likely (qtd != NULL)) {
  			struct ehci_qtd		*dummy;
  			dma_addr_t		dma;
  			__hc32			token;
  
  			/* to avoid racing the HC, use the dummy td instead of
  			 * the first td of our list (becomes new dummy).  both
  			 * tds stay deactivated until we're done, when the
  			 * HC is allowed to fetch the old dummy (4.10.2).
  			 */
  			token = qtd->hw_token;
  			qtd->hw_token = HALT_BIT(ehci);
  
  			dummy = qh->dummy;
  
  			dma = dummy->qtd_dma;
  			*dummy = *qtd;
  			dummy->qtd_dma = dma;
  
  			list_del (&qtd->qtd_list);
  			list_add (&dummy->qtd_list, qtd_list);
  			list_splice_tail(qtd_list, &qh->qtd_list);
  
  			ehci_qtd_init(ehci, qtd, qtd->qtd_dma);
  			qh->dummy = qtd;
  
  			/* hc must see the new dummy at list end */
  			dma = qtd->qtd_dma;
  			qtd = list_entry (qh->qtd_list.prev,
  					struct ehci_qtd, qtd_list);
  			qtd->hw_next = QTD_NEXT(ehci, dma);
  
  			/* let the hc process these next qtds */
  			wmb ();
  			dummy->hw_token = token;
  
  			urb->hcpriv = qh;
  		}
  	}
  	return qh;
  }
  
  /*-------------------------------------------------------------------------*/
  
  static int
  submit_async (
  	struct ehci_hcd		*ehci,
  	struct urb		*urb,
  	struct list_head	*qtd_list,
  	gfp_t			mem_flags
  ) {
  	int			epnum;
  	unsigned long		flags;
  	struct ehci_qh		*qh = NULL;
  	int			rc;
  
  	epnum = urb->ep->desc.bEndpointAddress;
  
  #ifdef EHCI_URB_TRACE
  	{
  		struct ehci_qtd *qtd;
  		qtd = list_entry(qtd_list->next, struct ehci_qtd, qtd_list);
  		ehci_dbg(ehci,
  			 "%s %s urb %p ep%d%s len %d, qtd %p [qh %p]
  ",
  			 __func__, urb->dev->devpath, urb,
  			 epnum & 0x0f, (epnum & USB_DIR_IN) ? "in" : "out",
  			 urb->transfer_buffer_length,
  			 qtd, urb->ep->hcpriv);
  	}
  #endif
  
  	spin_lock_irqsave (&ehci->lock, flags);
  	if (unlikely(!HCD_HW_ACCESSIBLE(ehci_to_hcd(ehci)))) {
  		rc = -ESHUTDOWN;
  		goto done;
  	}
  	rc = usb_hcd_link_urb_to_ep(ehci_to_hcd(ehci), urb);
  	if (unlikely(rc))
  		goto done;
  
  	qh = qh_append_tds(ehci, urb, qtd_list, epnum, &urb->ep->hcpriv);
  	if (unlikely(qh == NULL)) {
  		usb_hcd_unlink_urb_from_ep(ehci_to_hcd(ehci), urb);
  		rc = -ENOMEM;
  		goto done;
  	}
  
  	/* Control/bulk operations through TTs don't need scheduling,
  	 * the HC and TT handle it when the TT has a buffer ready.
  	 */
  	if (likely (qh->qh_state == QH_STATE_IDLE))
  		qh_link_async(ehci, qh);
   done:
  	spin_unlock_irqrestore (&ehci->lock, flags);
  	if (unlikely (qh == NULL))
  		qtd_list_free (ehci, urb, qtd_list);
  	return rc;
  }
  
  /*-------------------------------------------------------------------------*/
  #ifdef CONFIG_USB_HCD_TEST_MODE
  /*
   * This function creates the qtds and submits them for the
   * SINGLE_STEP_SET_FEATURE Test.
   * This is done in two parts: first SETUP req for GetDesc is sent then
   * 15 seconds later, the IN stage for GetDesc starts to req data from dev
   *
   * is_setup : i/p arguement decides which of the two stage needs to be
   * performed; TRUE - SETUP and FALSE - IN+STATUS
   * Returns 0 if success
   */
  static int submit_single_step_set_feature(
  	struct usb_hcd  *hcd,
  	struct urb      *urb,
  	int             is_setup
  ) {
  	struct ehci_hcd		*ehci = hcd_to_ehci(hcd);
  	struct list_head	qtd_list;
  	struct list_head	*head;
  
  	struct ehci_qtd		*qtd, *qtd_prev;
  	dma_addr_t		buf;
  	int			len, maxpacket;
  	u32			token;
  
  	INIT_LIST_HEAD(&qtd_list);
  	head = &qtd_list;
  
  	/* URBs map to sequences of QTDs:  one logical transaction */
  	qtd = ehci_qtd_alloc(ehci, GFP_KERNEL);
  	if (unlikely(!qtd))
  		return -1;
  	list_add_tail(&qtd->qtd_list, head);
  	qtd->urb = urb;
  
  	token = QTD_STS_ACTIVE;
  	token |= (EHCI_TUNE_CERR << 10);
  
  	len = urb->transfer_buffer_length;
  	/*
  	 * Check if the request is to perform just the SETUP stage (getDesc)
  	 * as in SINGLE_STEP_SET_FEATURE test, DATA stage (IN) happens
  	 * 15 secs after the setup
  	 */
  	if (is_setup) {
  		/* SETUP pid */
  		qtd_fill(ehci, qtd, urb->setup_dma,
  				sizeof(struct usb_ctrlrequest),
  				token | (2 /* "setup" */ << 8), 8);
  
  		submit_async(ehci, urb, &qtd_list, GFP_ATOMIC);
  		return 0; /*Return now; we shall come back after 15 seconds*/
  	}
  
  	/*
  	 * IN: data transfer stage:  buffer setup : start the IN txn phase for
  	 * the get_Desc SETUP which was sent 15seconds back
  	 */
  	token ^= QTD_TOGGLE;   /*We need to start IN with DATA-1 Pid-sequence*/
  	buf = urb->transfer_dma;
  
  	token |= (1 /* "in" */ << 8);  /*This is IN stage*/
  
  	maxpacket = max_packet(usb_maxpacket(urb->dev, urb->pipe, 0));
  
  	qtd_fill(ehci, qtd, buf, len, token, maxpacket);
  
  	/*
  	 * Our IN phase shall always be a short read; so keep the queue running
  	 * and let it advance to the next qtd which zero length OUT status
  	 */
  	qtd->hw_alt_next = EHCI_LIST_END(ehci);
  
  	/* STATUS stage for GetDesc control request */
  	token ^= 0x0100;        /* "in" <--> "out"  */
  	token |= QTD_TOGGLE;    /* force DATA1 */
  
  	qtd_prev = qtd;
  	qtd = ehci_qtd_alloc(ehci, GFP_ATOMIC);
  	if (unlikely(!qtd))
  		goto cleanup;
  	qtd->urb = urb;
  	qtd_prev->hw_next = QTD_NEXT(ehci, qtd->qtd_dma);
  	list_add_tail(&qtd->qtd_list, head);
  
  	/* dont fill any data in such packets */
  	qtd_fill(ehci, qtd, 0, 0, token, 0);
  
  	/* by default, enable interrupt on urb completion */
  	if (likely(!(urb->transfer_flags & URB_NO_INTERRUPT)))
  		qtd->hw_token |= cpu_to_hc32(ehci, QTD_IOC);
  
  	submit_async(ehci, urb, &qtd_list, GFP_KERNEL);
  
  	return 0;
  
  cleanup:
  	qtd_list_free(ehci, urb, head);
  	return -1;
  }
  #endif /* CONFIG_USB_HCD_TEST_MODE */
  
  /*-------------------------------------------------------------------------*/
  
  static void single_unlink_async(struct ehci_hcd *ehci, struct ehci_qh *qh)
  {
  	struct ehci_qh		*prev;
  
  	/* Add to the end of the list of QHs waiting for the next IAAD */
  	qh->qh_state = QH_STATE_UNLINK_WAIT;
  	list_add_tail(&qh->unlink_node, &ehci->async_unlink);
  
  	/* Unlink it from the schedule */
  	prev = ehci->async;
  	while (prev->qh_next.qh != qh)
  		prev = prev->qh_next.qh;
  
  	prev->hw->hw_next = qh->hw->hw_next;
  	prev->qh_next = qh->qh_next;
  	if (ehci->qh_scan_next == qh)
  		ehci->qh_scan_next = qh->qh_next.qh;
  }
  
  static void start_iaa_cycle(struct ehci_hcd *ehci)
  {
  	/* Do nothing if an IAA cycle is already running */
  	if (ehci->iaa_in_progress)
  		return;
  	ehci->iaa_in_progress = true;
  
  	/* If the controller isn't running, we don't have to wait for it */
  	if (unlikely(ehci->rh_state < EHCI_RH_RUNNING)) {
  		end_unlink_async(ehci);
  
  	/* Otherwise start a new IAA cycle */
  	} else if (likely(ehci->rh_state == EHCI_RH_RUNNING)) {
  
  		/* Make sure the unlinks are all visible to the hardware */
  		wmb();
  
  		ehci_writel(ehci, ehci->command | CMD_IAAD,
  				&ehci->regs->command);
  		ehci_readl(ehci, &ehci->regs->command);
  		ehci_enable_event(ehci, EHCI_HRTIMER_IAA_WATCHDOG, true);
  	}
  }
  
  /* the async qh for the qtds being unlinked are now gone from the HC */
  
  static void end_unlink_async(struct ehci_hcd *ehci)
  {
  	struct ehci_qh		*qh;
  	bool			early_exit;
  
  	if (ehci->has_synopsys_hc_bug)
  		ehci_writel(ehci, (u32) ehci->async->qh_dma,
  			    &ehci->regs->async_next);
  
  	/* The current IAA cycle has ended */
  	ehci->iaa_in_progress = false;
  
  	if (list_empty(&ehci->async_unlink))
  		return;
  	qh = list_first_entry(&ehci->async_unlink, struct ehci_qh,
  			unlink_node);	/* QH whose IAA cycle just ended */
  
  	/*
  	 * If async_unlinking is set then this routine is already running,
  	 * either on the stack or on another CPU.
  	 */
  	early_exit = ehci->async_unlinking;
  
  	/* If the controller isn't running, process all the waiting QHs */
  	if (ehci->rh_state < EHCI_RH_RUNNING)
  		list_splice_tail_init(&ehci->async_unlink, &ehci->async_idle);
  
  	/*
  	 * Intel (?) bug: The HC can write back the overlay region even
  	 * after the IAA interrupt occurs.  In self-defense, always go
  	 * through two IAA cycles for each QH.
  	 */
  	else if (qh->qh_state == QH_STATE_UNLINK_WAIT) {
  		qh->qh_state = QH_STATE_UNLINK;
  		early_exit = true;
  	}
  
  	/* Otherwise process only the first waiting QH (NVIDIA bug?) */
  	else
  		list_move_tail(&qh->unlink_node, &ehci->async_idle);
  
  	/* Start a new IAA cycle if any QHs are waiting for it */
  	if (!list_empty(&ehci->async_unlink))
  		start_iaa_cycle(ehci);
  
  	/*
  	 * Don't allow nesting or concurrent calls,
  	 * or wait for the second IAA cycle for the next QH.
  	 */
  	if (early_exit)
  		return;
  
  	/* Process the idle QHs */
  	ehci->async_unlinking = true;
  	while (!list_empty(&ehci->async_idle)) {
  		qh = list_first_entry(&ehci->async_idle, struct ehci_qh,
  				unlink_node);
  		list_del(&qh->unlink_node);
  
  		qh->qh_state = QH_STATE_IDLE;
  		qh->qh_next.qh = NULL;
  
  		if (!list_empty(&qh->qtd_list))
  			qh_completions(ehci, qh);
  		if (!list_empty(&qh->qtd_list) &&
  				ehci->rh_state == EHCI_RH_RUNNING)
  			qh_link_async(ehci, qh);
  		disable_async(ehci);
  	}
  	ehci->async_unlinking = false;
  }
  
  static void start_unlink_async(struct ehci_hcd *ehci, struct ehci_qh *qh);
  
  static void unlink_empty_async(struct ehci_hcd *ehci)
  {
  	struct ehci_qh		*qh;
  	struct ehci_qh		*qh_to_unlink = NULL;
  	int			count = 0;
  
  	/* Find the last async QH which has been empty for a timer cycle */
  	for (qh = ehci->async->qh_next.qh; qh; qh = qh->qh_next.qh) {
  		if (list_empty(&qh->qtd_list) &&
  				qh->qh_state == QH_STATE_LINKED) {
  			++count;
  			if (qh->unlink_cycle != ehci->async_unlink_cycle)
  				qh_to_unlink = qh;
  		}
  	}
  
  	/* If nothing else is being unlinked, unlink the last empty QH */
  	if (list_empty(&ehci->async_unlink) && qh_to_unlink) {
  		start_unlink_async(ehci, qh_to_unlink);
  		--count;
  	}
  
  	/* Other QHs will be handled later */
  	if (count > 0) {
  		ehci_enable_event(ehci, EHCI_HRTIMER_ASYNC_UNLINKS, true);
  		++ehci->async_unlink_cycle;
  	}
  }
  
  /* The root hub is suspended; unlink all the async QHs */
  static void __maybe_unused unlink_empty_async_suspended(struct ehci_hcd *ehci)
  {
  	struct ehci_qh		*qh;
  
  	while (ehci->async->qh_next.qh) {
  		qh = ehci->async->qh_next.qh;
  		WARN_ON(!list_empty(&qh->qtd_list));
  		single_unlink_async(ehci, qh);
  	}
  	start_iaa_cycle(ehci);
  }
  
  /* makes sure the async qh will become idle */
  /* caller must own ehci->lock */
  
  static void start_unlink_async(struct ehci_hcd *ehci, struct ehci_qh *qh)
  {
  	/* If the QH isn't linked then there's nothing we can do. */
  	if (qh->qh_state != QH_STATE_LINKED)
  		return;
  
  	single_unlink_async(ehci, qh);
  	start_iaa_cycle(ehci);
  }
  
  /*-------------------------------------------------------------------------*/
  
  static void scan_async (struct ehci_hcd *ehci)
  {
  	struct ehci_qh		*qh;
  	bool			check_unlinks_later = false;
  
  	ehci->qh_scan_next = ehci->async->qh_next.qh;
  	while (ehci->qh_scan_next) {
  		qh = ehci->qh_scan_next;
  		ehci->qh_scan_next = qh->qh_next.qh;
  
  		/* clean any finished work for this qh */
  		if (!list_empty(&qh->qtd_list)) {
  			int temp;
  
  			/*
  			 * Unlinks could happen here; completion reporting
  			 * drops the lock.  That's why ehci->qh_scan_next
  			 * always holds the next qh to scan; if the next qh
  			 * gets unlinked then ehci->qh_scan_next is adjusted
  			 * in single_unlink_async().
  			 */
  			temp = qh_completions(ehci, qh);
  			if (unlikely(temp)) {
  				start_unlink_async(ehci, qh);
  			} else if (list_empty(&qh->qtd_list)
  					&& qh->qh_state == QH_STATE_LINKED) {
  				qh->unlink_cycle = ehci->async_unlink_cycle;
  				check_unlinks_later = true;
  			}
  		}
  	}
  
  	/*
  	 * Unlink empty entries, reducing DMA usage as well
  	 * as HCD schedule-scanning costs.  Delay for any qh
  	 * we just scanned, there's a not-unusual case that it
  	 * doesn't stay idle for long.
  	 */
  	if (check_unlinks_later && ehci->rh_state == EHCI_RH_RUNNING &&
  			!(ehci->enabled_hrtimer_events &
  				BIT(EHCI_HRTIMER_ASYNC_UNLINKS))) {
  		ehci_enable_event(ehci, EHCI_HRTIMER_ASYNC_UNLINKS, true);
  		++ehci->async_unlink_cycle;
  	}
  }