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USB: UHCI: improve scheduling of interrupt URBs

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This patch (as1140) adds a little intelligence to the interrupt-URB
scheduler in uhci-hcd.  Right now the scheduler is stupid; every URB
having the same period is assigned to the same slot.  Thus a large
group of period-N URBs can fill their slot and cause -ENOSPC errors
even when all the lower-period slots are empty.

With the patch, if an URB doesn't fit in its assigned slot then the
scheduler will try using lower-period slots.  This will provide
greater flexibility.  As an example, the driver will be able to handle
more than just three or four mice, which the current driver cannot.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Alan Stern 2008-09-25 16:59:57 -04:00 committed by Greg Kroah-Hartman
parent 925dff5dee
commit e58dcebcd8
1 changed files with 11 additions and 6 deletions
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17
drivers/usb/host/uhci-q.c
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@ -1065,13 +1065,18 @@ static int uhci_submit_interrupt(struct uhci_hcd *uhci, struct urb *urb,
}
if (exponent < 0)
return -EINVAL;
qh->period = 1 << exponent;
qh->skel = SKEL_INDEX(exponent);
/* For now, interrupt phase is fixed by the layout
* of the QH lists. */
qh->phase = (qh->period / 2) & (MAX_PHASE - 1);
ret = uhci_check_bandwidth(uhci, qh);
/* If the slot is full, try a lower period */
do {
qh->period = 1 << exponent;
qh->skel = SKEL_INDEX(exponent);
/* For now, interrupt phase is fixed by the layout
* of the QH lists.
*/
qh->phase = (qh->period / 2) & (MAX_PHASE - 1);
ret = uhci_check_bandwidth(uhci, qh);
} while (ret != 0 && --exponent >= 0);
if (ret)
return ret;
} else if (qh->period > urb->interval)