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linux-next/drivers/usb/host/ehci-q.c
Corentin Labbe a0ef2bdfa3 usb: host: Replace empty define with do while 
It's dangerous to use empty code define.
Furthermore it lead to the following warning:
"suggest braces around empty body in an « else » statement"

So let's replace emptyness by "do {} while(0)"

Furthermore, as suggested by Joe Perches, rename the macro to INCR.

Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-09-28 15:03:37 +02:00

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// SPDX-License-Identifier: GPL-2.0+
/*
* Copyright (C) 2001-2004 by David Brownell
*/
/* 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;
if (qh->should_be_inactive)
ehci_warn(ehci, "qh %p should be inactive!\n", qh);
} else {
qh_update(ehci, qh, qtd);
}
qh->should_be_inactive = 0;
}
/*-------------------------------------------------------------------------*/
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\n",
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\n",
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)) {
INCR(ehci->stats.unlink);
} else {
/* report non-error and short read status as zero */
if (status == -EINPROGRESS || status == -EREMOTEIO)
status = 0;
INCR(ehci->stats.complete);
}
#ifdef EHCI_URB_TRACE
ehci_dbg (ehci,
"%s %s urb %p ep%d%s status %d len %d/%d\n",
__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]\n",
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\n",
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;
qh->unlink_reason |= QH_UNLINK_HALTED;
/* 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;
qh->unlink_reason |= QH_UNLINK_SHORT_READ;
}
/* 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;
qh->unlink_reason |= QH_UNLINK_SHUTDOWN;
}
/* 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);
qh->should_be_inactive = 1;
/* 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->unlink_reason |= QH_UNLINK_DUMMY_OVERLAY;
/* Let the caller know if the QH needs to be unlinked. */
return qh->unlink_reason;
}
/*-------------------------------------------------------------------------*/
/*
* 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 = 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);
struct usb_host_endpoint *ep;
u32 info1 = 0, info2 = 0;
int is_input, type;
int maxp = 0;
int mult;
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);
ep = usb_pipe_endpoint (urb->dev, urb->pipe);
maxp = usb_endpoint_maxp (&ep->desc);
mult = usb_endpoint_maxp_mult (&ep->desc);
/* 1024 byte maxpacket is a hardware ceiling. High bandwidth
* acts like up to 3KB, but is built from smaller packets.
*/
if (maxp > 1024) {
ehci_dbg(ehci, "bogus qh maxpacket %d\n", 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, mult * 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, 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 |= maxp << 16;
info2 |= (EHCI_TUNE_MULT_HS << 30);
} else { /* PIPE_INTERRUPT */
info1 |= maxp << 16;
info2 |= mult << 30;
}
break;
default:
ehci_dbg(ehci, "bogus dev %p speed %d\n", 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->unlink_reason = 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]\n",
__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, and interrupt after SETUP completion */
qtd_fill(ehci, qtd, urb->setup_dma,
sizeof(struct usb_ctrlrequest),
QTD_IOC | 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 = 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);
/* Interrupt after STATUS completion */
qtd_fill(ehci, qtd, 0, 0, token | QTD_IOC, 0);
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)
{
/* 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 if one isn't already running */
} else if (ehci->rh_state == EHCI_RH_RUNNING &&
!ehci->iaa_in_progress) {
/* 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->iaa_in_progress = true;
ehci_enable_event(ehci, EHCI_HRTIMER_IAA_WATCHDOG, true);
}
}
static void end_iaa_cycle(struct ehci_hcd *ehci)
{
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;
end_unlink_async(ehci);
}
/* See if 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 (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) {
/*
* Second IAA cycle has finished. Process only the first
* waiting QH (NVIDIA (?) bug).
*/
list_move_tail(&qh->unlink_node, &ehci->async_idle);
}
/*
* AMD/ATI (?) bug: The HC can continue to use an active QH long
* after the IAA interrupt occurs. To prevent problems, QHs that
* may still be active will wait until 2 ms have passed with no
* change to the hw_current and hw_token fields (this delay occurs
* between the two IAA cycles).
*
* The EHCI spec (4.8.2) says that active QHs must not be removed
* from the async schedule and recommends waiting until the QH
* goes inactive. This is ridiculous because the QH will _never_
* become inactive if the endpoint NAKs indefinitely.
*/
/* Some reasons for unlinking guarantee the QH can't be active */
else if (qh->unlink_reason & (QH_UNLINK_HALTED |
QH_UNLINK_SHORT_READ | QH_UNLINK_DUMMY_OVERLAY))
goto DelayDone;
/* The QH can't be active if the queue was and still is empty... */
else if ((qh->unlink_reason & QH_UNLINK_QUEUE_EMPTY) &&
list_empty(&qh->qtd_list))
goto DelayDone;
/* ... or if the QH has halted */
else if (qh->hw->hw_token & cpu_to_hc32(ehci, QTD_STS_HALT))
goto DelayDone;
/* Otherwise we have to wait until the QH stops changing */
else {
__hc32 qh_current, qh_token;
qh_current = qh->hw->hw_current;
qh_token = qh->hw->hw_token;
if (qh_current != ehci->old_current ||
qh_token != ehci->old_token) {
ehci->old_current = qh_current;
ehci->old_token = qh_token;
ehci_enable_event(ehci,
EHCI_HRTIMER_ACTIVE_UNLINK, true);
return;
}
DelayDone:
qh->qh_state = QH_STATE_UNLINK;
early_exit = true;
}
ehci->old_current = ~0; /* Prepare for next QH */
/* 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) {
qh_to_unlink->unlink_reason |= QH_UNLINK_QUEUE_EMPTY;
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;
}
}
#ifdef CONFIG_PM
/* The root hub is suspended; unlink all the async QHs */
static void 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);
}
}
#endif
/* 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;
}
}
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