[PATCH 3.18 153/183] USB: EHCI: fix initialization bug in iso_stream_schedule()

Greg Kroah-Hartman
2015-01-25T18:29:18Z

From: Alan Stern <stern@rowland.harvard.edu>

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@rowland.harvard.edu>
Fixes: c3ee9b76aa93
Reported-by: Joe Bryant <tenminjoe@yahoo.com>
Tested-by: Joe Bryant <tenminjoe@yahoo.com>
Tested-by: Martin Long <martin@longhome.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/usb/host/ehci-sched.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

--- 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;