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

commit 5d0f801a 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@pengutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

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;