[3.8.y.z extended stable] Patch "can: c_can: Fix RX message handling, handle lost message before EOB" has been added to staging queue

[Kamal Mostafa]

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

    can: c_can: Fix RX message handling, handle lost message before EOB

to the linux-3.8.y-queue branch of the 3.8.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-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.14.

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

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 387b48716c293044d8500ccf48631b318d100442 Mon Sep 17 00:00:00 2001
From: Markus Pargmann <mpa at pengutronix.de>
Date: Mon, 28 Oct 2013 09:54:40 +0100
Subject: can: c_can: Fix RX message handling, handle lost message before EOB

commit 5d0f801a2ccec3b1fdabc3392c8d99ed0413d216 upstream.

If we handle end of block messages with higher priority than a lost message,
we can run into an endless interrupt loop.

This is reproducable with a am335x processor and "cansequence -r" at 1Mbit.
As soon as we loose a packet we can't escape from an interrupt loop.

This patch fixes the problem by handling lost packets before EOB packets.

Signed-off-by: Markus Pargmann <mpa at pengutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl at pengutronix.de>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/net/can/c_can/c_can.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/can/c_can/c_can.c b/drivers/net/can/c_can/c_can.c
index 2282b1a..915847d 100644
--- a/drivers/net/can/c_can/c_can.c
+++ b/drivers/net/can/c_can/c_can.c
@@ -810,9 +810,6 @@ static int c_can_do_rx_poll(struct net_device *dev, int quota)
 			msg_ctrl_save = priv->read_reg(priv,
 					C_CAN_IFACE(MSGCTRL_REG, 0));

-			if (msg_ctrl_save & IF_MCONT_EOB)
-				return num_rx_pkts;
-
 			if (msg_ctrl_save & IF_MCONT_MSGLST) {
 				c_can_handle_lost_msg_obj(dev, 0, msg_obj);
 				num_rx_pkts++;
@@ -820,6 +817,9 @@ static int c_can_do_rx_poll(struct net_device *dev, int quota)
 				continue;
 			}

+			if (msg_ctrl_save & IF_MCONT_EOB)
+				return num_rx_pkts;
+
 			if (!(msg_ctrl_save & IF_MCONT_NEWDAT))
 				continue;

--
1.8.3.2