can: c_can: Fix RX message handling, 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 an interrupt loop.

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

Cc: linux-stable <stable@vger.kernel.org>
Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/drivers/net/can/c_can/c_can.c b/drivers/net/can/c_can/c_can.c
index a668cd4..e3fc07c 100644 (file)
--- 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;