From c065c60e83c006611caed23d1320450fcd709398 Mon Sep 17 00:00:00 2001 From: Dan Streetman Date: Tue, 21 Apr 2009 13:37:12 -0400 Subject: USB: ehci-sched.c: EHCI SITD scheduling bugfix Without this patch, the driver won't check that the last fully-occupied uframe for a new split transaction was vacant beforehand. This can lead to a situation in which the first 188 bytes of a 192-byte isochronous transfer are scheduled in the same uframe as an existing interrupt transfer. The resulting schedule looks like this: uframe 0: 188-byte isoc-OUT SSPLIT, 8-byte int-IN SSPLIT uframe 1: 4-byte isoc-OUT SSPLIT The SSPLITs are intermingled, causing an error in the downstream hub's TT. If you are having problems with devices or hub ports resetting, or failed interrupt transfers, when you start using a USB audio or video (Isochronous) device, this patch may help. Signed-off-by: Dan Streetman Reported-by: Kung James Acked-by: David Brownell Cc: Alan Stern --- drivers/usb/host/ehci-sched.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c index ada5d2ba297..556d0ec0c1f 100644 --- a/drivers/usb/host/ehci-sched.c +++ b/drivers/usb/host/ehci-sched.c @@ -323,7 +323,7 @@ static int tt_available ( * already scheduled transactions */ if (125 < usecs) { - int ufs = (usecs / 125) - 1; + int ufs = (usecs / 125); int i; for (i = uframe; i < (uframe + ufs) && i < 8; i++) if (0 < tt_usecs[i]) { -- cgit v1.2.3-70-g09d2