linux-kernel - [PATCH] can: c_can: Handle lost message before EOB

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Message-Id: <1382950480-12515-1-git-send-email-mpa@pengutronix.de>
Date:	Mon, 28 Oct 2013 09:54:40 +0100
From:	Markus Pargmann <mpa@...gutronix.de>
To:	Marc Kleine-Budde <mkl@...gutronix.de>,
	Wolfgang Grandegger <wg@...ndegger.com>
Cc:	linux-can@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel@...gutronix.de,
	Markus Pargmann <mpa@...gutronix.de>
Subject: [PATCH] can: c_can: Handle lost message before EOB

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 a interrupt
loop.

This patch handles lost packets before EOB packets.

Signed-off-by: Markus Pargmann <mpa@...gutronix.de>
---
 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 a668cd4..e3fc07c 100644
--- a/drivers/net/can/c_can/c_can.c
+++ b/drivers/net/can/c_can/c_can.c
@@ -814,9 +814,6 @@ 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++;
@@ -824,6 +821,9 @@ 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;
 
-- 
1.8.4.rc3

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