[3.13.y-ckt stable] Patch "USB: EHCI: fix initialization bug in iso_stream_schedule()" has been added to staging queue

[Kamal Mostafa]

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

    USB: EHCI: fix initialization bug in iso_stream_schedule()

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt16.

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

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 6a046b6c20670e6dd00e612980af4becc5337e3a Mon Sep 17 00:00:00 2001
From: Alan Stern <stern at rowland.harvard.edu>
Date: Thu, 4 Dec 2014 10:21:56 -0500
Subject: USB: EHCI: fix initialization bug in iso_stream_schedule()

commit 6d89252a998a695ecb0348fc2d717dc33d90cae9 upstream.

Commit c3ee9b76aa93 (EHCI: improved logic for isochronous scheduling)
introduced the idea of using ehci->last_iso_frame as the origin (or
base) for the circular calculations involved in modifying the
isochronous schedule.  However, the new code it added used
ehci->last_iso_frame before the value was properly initialized.  This
patch rectifies the mistake by moving the initialization lines earlier
in iso_stream_schedule().

This fixes Bugzilla #72891.

Signed-off-by: Alan Stern <stern at rowland.harvard.edu>
Fixes: c3ee9b76aa93
Reported-by: Joe Bryant <tenminjoe at yahoo.com>
Tested-by: Joe Bryant <tenminjoe at yahoo.com>
Tested-by: Martin Long <martin at longhome.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/usb/host/ehci-sched.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index e113fd7..c399606 100644
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -1581,6 +1581,10 @@ iso_stream_schedule (
 	else
 		next = (now + 2 + 7) & ~0x07;	/* full frame cache */

+	/* If needed, initialize last_iso_frame so that this URB will be seen */
+	if (ehci->isoc_count == 0)
+		ehci->last_iso_frame = now >> 3;
+
 	/*
 	 * Use ehci->last_iso_frame as the base.  There can't be any
 	 * TDs scheduled for earlier than that.
@@ -1671,10 +1675,6 @@ iso_stream_schedule (
 	urb->start_frame = start & (mod - 1);
 	if (!stream->highspeed)
 		urb->start_frame >>= 3;
-
-	/* Make sure scan_isoc() sees these */
-	if (ehci->isoc_count == 0)
-		ehci->last_iso_frame = now >> 3;
 	return status;

  fail:
--
1.9.1