From 68335e816a92411649955a9903b1f30c388ea322 Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Fri, 22 May 2009 17:02:33 -0400 Subject: 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: Alan Stern Tested-by: Dwayne Fontenot Cc: David Brownell Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/ehci-sched.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'drivers/usb/host/ehci-sched.c') diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c index 556d0ec0c1f..9d1babc7ff6 100644 --- a/drivers/usb/host/ehci-sched.c +++ b/drivers/usb/host/ehci-sched.c @@ -760,8 +760,10 @@ static int qh_schedule(struct ehci_hcd *ehci, struct ehci_qh *qh) if (status) { /* "normal" case, uframing flexible except with splits */ if (qh->period) { - frame = qh->period - 1; - do { + int i; + + for (i = qh->period; status && i > 0; --i) { + frame = ++ehci->random_frame % qh->period; for (uframe = 0; uframe < 8; uframe++) { status = check_intr_schedule (ehci, frame, uframe, qh, @@ -769,7 +771,7 @@ static int qh_schedule(struct ehci_hcd *ehci, struct ehci_qh *qh) if (status == 0) break; } - } while (status && frame--); + } /* qh->period == 0 means every uframe */ } else { -- cgit v1.2.3