can: at91_can: add listen only mode

This patch adds listen only mode support to the at91_can driver.
Signed-off-by: Yoann DI-RUZZA <ydiruzza@gmail.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/at91_can.c

@@ -420,7 +420,11 @@ static void at91_chip_start(struct net_device *dev)
 	at91_transceiver_switch(priv, 1);
 
 	/* enable chip */
-	at91_write(priv, AT91_MR, AT91_MR_CANEN);
+	if (priv->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)
+		reg_mr = AT91_MR_CANEN | AT91_MR_ABM;
+	else
+		reg_mr = AT91_MR_CANEN;
+	at91_write(priv, AT91_MR, reg_mr);
 
 	priv->can.state = CAN_STATE_ERROR_ACTIVE;
 
@@ -1341,7 +1345,8 @@ static int at91_can_probe(struct platform_device *pdev)
 	priv->can.bittiming_const = &at91_bittiming_const;
 	priv->can.do_set_mode = at91_set_mode;
 	priv->can.do_get_berr_counter = at91_get_berr_counter;
-	priv->can.ctrlmode_supported = CAN_CTRLMODE_3_SAMPLES;
+	priv->can.ctrlmode_supported = CAN_CTRLMODE_3_SAMPLES |
+		CAN_CTRLMODE_LISTENONLY;
 	priv->dev = dev;
 	priv->reg_base = addr;
 	priv->devtype_data = *devtype_data;