This is a note to let you know that I've just added the patch titled
USB: fix latency in uhci-hcd and ohci-hcd
to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.
If you have any questions about this process, please let me know.
>From e1944017839d7dfbf7329fac4bdec8b4050edf5e Mon Sep 17 00:00:00 2001
From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Date: Tue, 14 May 2013 13:57:19 -0400
Subject: 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@xxxxxxxxxxxxxxxxxxx>
Reported-and-tested-by: Joe Rayhawk <jrayhawk@xxxxxxxxxxxxxxxx>
CC: Clemens Ladisch <clemens@xxxxxxxxxx>
CC: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/host/ohci-hcd.c | 2 +-
drivers/usb/host/uhci-q.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/usb/host/ohci-hcd.c b/drivers/usb/host/ohci-hcd.c
index 9e6de95..df1af0b 100644
--- a/drivers/usb/host/ohci-hcd.c
+++ b/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? */
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 @@ static int uhci_submit_isochronous(struct uhci_hcd *uhci, struct urb *urb,
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)) {
--
1.8.3.rc1.46.g4a27aed
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