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USB: EHCI: change deschedule logic for interrupt QHs

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This patch (as1281) changes the way ehci-hcd deschedules interrupt
QHs, copying the approach used for async QHs.  The caller is no longer
responsible for rescheduling the QH if its queue is non-empty; instead
the reschedule is done directly by intr_deschedule(), after calling
qh_completions().  This is exactly the same as how end_unlink_async()
works.

ehci_urb_dequeue() and intr_deschedule() now correctly handle the case
where they are called while another interrupt URB for the same QH is
being given back.  This was a surprisingly large blind spot.  And
scan_periodic() now respects the new needs_rescan flag.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: David Brownell <david-b@pacbell.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Alan Stern 2009-08-19 12:22:44 -04:00 • committed by Greg Kroah-Hartman
parent 3a44494e23
commit a448c9d8c5
3 changed files with 40 additions and 34 deletions
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36
drivers/usb/host/ehci-sched.c
View file

@ -615,8 +615,19 @@ static int qh_unlink_periodic(struct ehci_hcd *ehci, struct ehci_qh *qh)
static void intr_deschedule (struct ehci_hcd *ehci, struct ehci_qh *qh)
{
unsigned wait;
struct ehci_qh_hw *hw = qh->hw;
unsigned wait;
struct ehci_qh_hw *hw = qh->hw;
int rc;
/* If the QH isn't linked then there's nothing we can do
* unless we were called during a giveback, in which case
* qh_completions() has to deal with it.
*/
if (qh->qh_state != QH_STATE_LINKED) {
if (qh->qh_state == QH_STATE_COMPLETING)
qh->needs_rescan = 1;
return;
}
qh_unlink_periodic (ehci, qh);
@ -636,6 +647,24 @@ static void intr_deschedule (struct ehci_hcd *ehci, struct ehci_qh *qh)
qh->qh_state = QH_STATE_IDLE;
hw->hw_next = EHCI_LIST_END(ehci);
wmb ();
qh_completions(ehci, qh);
/* reschedule QH iff another request is queued */
if (!list_empty(&qh->qtd_list) &&
HC_IS_RUNNING(ehci_to_hcd(ehci)->state)) {
rc = qh_schedule(ehci, qh);
/* An error here likely indicates handshake failure
* or no space left in the schedule. Neither fault
* should happen often ...
*
* FIXME kill the now-dysfunctional queued urbs
*/
if (rc != 0)
ehci_err(ehci, "can't reschedule qh %p, err %d\n",
qh, rc);
}
}
/*-------------------------------------------------------------------------*/
@ -2213,7 +2242,8 @@ restart:
type = Q_NEXT_TYPE(ehci, q.qh->hw->hw_next);
q = q.qh->qh_next;
modified = qh_completions (ehci, temp.qh);
if (unlikely (list_empty (&temp.qh->qtd_list)))
if (unlikely(list_empty(&temp.qh->qtd_list) ||
temp.qh->needs_rescan))
intr_deschedule (ehci, temp.qh);
qh_put (temp.qh);
break;