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authorDan Streetman2009-04-21 13:37:12 -0400
committerGreg Kroah-Hartman2009-04-23 14:15:28 -0700
commitc065c60e83c006611caed23d1320450fcd709398 (patch)
tree59640660e40d4f5da151fb209888c7dc435cef09 /drivers/usb
parent37768adf9a1d49aeac0db1ba3dc28b3274b7b789 (diff)
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 <ddstreet@ieee.org> Reported-by: Kung James <kong1191@gmail.com> Acked-by: David Brownell <dbrownell@users.sourceforge.net> Cc: Alan Stern <stern@rowland.harvard.edu>
Diffstat (limited to 'drivers/usb')
-rw-r--r--drivers/usb/host/ehci-sched.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index ada5d2ba297b..556d0ec0c1f8 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]) {