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Commit 68335e81 authored by Alan Stern's avatar Alan Stern Committed by Greg Kroah-Hartman
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USB: EHCI: stagger frames for interrupt transfers 



This patch (as1243) tries to improve ehci-hcd's scheduling of
interrupt transfers.  Instead of trying to cram all transfers with the
same period into the same frame, the new code will spread the
transfers out among lots of different frames.  This should reduce the
periodic schedule load in any one frame -- some host controllers have
trouble when there's too much work to do.

A more thorough approach would stagger the uframe values as well.  But
this is enough to make a big improvement.

Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Tested-by: default avatarDwayne Fontenot <dwayne.fontenot@att.net>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent be475d90

drivers/usb/host/ehci-sched.c

+5 −3
Original line number Original line Diff line number Diff line
@@ -760,8 +760,10 @@ static int qh_schedule(struct ehci_hcd *ehci, struct ehci_qh *qh) 
	if (status) {

	if (status) {

		/* "normal" case, uframing flexible except with splits */

		/* "normal" case, uframing flexible except with splits */

		if (qh->period) {

		if (qh->period) {

			frame = qh->period - 1;

			int		i;

			do {



			for (i = qh->period; status && i > 0; --i) {

				frame = ++ehci->random_frame % qh->period;

				for (uframe = 0; uframe < 8; uframe++) {

				for (uframe = 0; uframe < 8; uframe++) {

					status = check_intr_schedule (ehci,

					status = check_intr_schedule (ehci,

							frame, uframe, qh,

							frame, uframe, qh,
@@ -769,7 +771,7 @@ static int qh_schedule(struct ehci_hcd *ehci, struct ehci_qh *qh) 
					if (status == 0)

					if (status == 0)

						break;

						break;

				}

				}

			} while (status && frame--);

			}





		/* qh->period == 0 means every uframe */

		/* qh->period == 0 means every uframe */

		} else {

		} else {

drivers/usb/host/ehci.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -116,6 +116,7 @@ struct ehci_hcd { /* one per controller */ 
	struct timer_list	watchdog;

	struct timer_list	watchdog;

	unsigned long		actions;

	unsigned long		actions;

	unsigned		stamp;

	unsigned		stamp;

	unsigned		random_frame;

	unsigned long		next_statechange;

	unsigned long		next_statechange;

	u32			command;

	u32			command;