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

[Luis Henriques]

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-3.5.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.
-Luis

------

>From ffba2280c6836b72ad6711513ea3f2a486375b7a 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>
[ luis: backported to 3.5: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques 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 64647d4..91d1b5a 100644
--- a/drivers/net/can/c_can/c_can.c
+++ b/drivers/net/can/c_can/c_can.c
@@ -764,9 +764,6 @@ static int c_can_do_rx_poll(struct net_device *dev, int quota)
 			msg_ctrl_save = priv->read_reg(priv,
 					&priv->regs->ifregs[0].msg_cntrl);

-			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++;
@@ -774,6 +771,9 @@ 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