[PATCH 3.2 020/185] can: c_can: Fix RX message handling, handlelost message before EOB

From: Ben Hutchings
Date: Sat Dec 28 2013 - 21:12:28 EST

3.2.54-rc1 review patch. If anyone has any objections, please let me know.


From: Markus Pargmann <mpa@xxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxx>
Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
drivers/net/can/c_can/c_can.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- 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_d
msg_ctrl_save = priv->read_reg(priv,

- 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);
@@ -774,6 +771,9 @@ static int c_can_do_rx_poll(struct net_d

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

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