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@xxxxxxxxxxxxxxxxxxx>
Reported-and-tested-by: Joe Rayhawk <jrayhawk@xxxxxxxxxxxxxxxx>
CC: Clemens Ladisch <clemens@xxxxxxxxxx>
CC: <stable@xxxxxxxxxxxxxxx>
---
[as1681]
drivers/usb/host/ohci-hcd.c | 2 +-
drivers/usb/host/uhci-q.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
Index: usb-3.9/drivers/usb/host/ohci-hcd.c
===================================================================
--- usb-3.9.orig/drivers/usb/host/ohci-hcd.c
+++ usb-3.9/drivers/usb/host/ohci-hcd.c
@@ -233,7 +233,7 @@ static int ohci_urb_enqueue (
urb->start_frame = frame;
}
} else if (ed->type == PIPE_ISOCHRONOUS) {
- u16 next = ohci_frame_no(ohci) + 2;
+ u16 next = ohci_frame_no(ohci) + 1;
u16 frame = ed->last_iso + ed->interval;
/* Behind the scheduling threshold? */
Index: usb-3.9/drivers/usb/host/uhci-q.c
===================================================================
--- usb-3.9.orig/drivers/usb/host/uhci-q.c
+++ usb-3.9/drivers/usb/host/uhci-q.c
@@ -1287,7 +1287,7 @@ static int uhci_submit_isochronous(struc
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)) {
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
