USB: fix latency in uhci-hcd and ohci-hcd
Commits c44b225077bb1fb25ed5cd5c4f226897b91bedd4 (UHCI: implement new
semantics for URB_ISO_ASAP) and
6a41b4d3fe8cd4cc95181516fc6fba7b1747a27c (OHCI: implement new
semantics for URB_ISO_ASAP) increased the latency for isochronous URBs
in uhci-hcd and ohci-hcd respectively to 2 milliseconds, in an
attempt to avoid underruns. It turns out that not only was this
unnecessary -- 1-ms latency works okay -- it also causes problems with
certain application loads such as real-time audio.
This patch changes the latency for both drivers back to 1 ms.
This should be applied to -stable kernels going back to 3.8.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-and-tested-by: Joe Rayhawk <jrayhawk@fairlystable.org>
CC: Clemens Ladisch <clemens@ladisch.de>
CC: <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/host/uhci-q.c b/drivers/usb/host/uhci-q.c
index f0976d8..041c6dd 100644
--- a/drivers/usb/host/uhci-q.c
+++ b/drivers/usb/host/uhci-q.c
@@ -1287,7 +1287,7 @@
return -EINVAL; /* Can't change the period */
} else {
- next = uhci->frame_number + 2;
+ next = uhci->frame_number + 1;
/* Find the next unused frame */
if (list_empty(&qh->queue)) {