[ 3.5.y.z extended stable ] Patch "USB: EHCI: fix bug in scheduling periodic split transfers" has been added to staging queue

[Herton Ronaldo Krzesinski]

This is a note to let you know that I have just added a patch titled

    USB: EHCI: fix bug in scheduling periodic split transfers

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Herton

------

>From e6dc80ced58a29df7711d3b35863393ea52aea4c Mon Sep 17 00:00:00 2001
From: Alan Stern <stern at rowland.harvard.edu>
Date: Wed, 30 Jan 2013 16:36:40 -0500
Subject: [PATCH] USB: EHCI: fix bug in scheduling periodic split transfers

commit 3e619d04159be54b3daa0b7036b0ce9e067f4b5d upstream.

This patch (as1654) fixes a very old bug in ehci-hcd, connected with
scheduling of periodic split transfers.  The calculations for
full/low-speed bus usage are all carried out after the correction for
bit-stuffing has been applied, but the values in the max_tt_usecs
array assume it hasn't been.  The array should allow for allocation of
up to 90% of the bus capacity, which is 900 us, not 780 us.

The symptom caused by this bug is that any isochronous transfer to a
full-speed device with a maxpacket size larger than about 980 bytes is
always rejected with a -ENOSPC error.

Signed-off-by: Alan Stern <stern at rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 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 33182c6..ccc9f70 100644
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -236,7 +236,7 @@ static inline unsigned char tt_start_uframe(struct ehci_hcd *ehci, __hc32 mask)
 }

 static const unsigned char
-max_tt_usecs[] = { 125, 125, 125, 125, 125, 125, 30, 0 };
+max_tt_usecs[] = { 125, 125, 125, 125, 125, 125, 125, 25 };

 /* carryover low/fullspeed bandwidth that crosses uframe boundries */
 static inline void carryover_tt_bandwidth(unsigned short tt_usecs[8])
--
1.7.9.5