net: dsa: mv88e6xxx: setup message ports

All interconnectable Marvell switch chips have an ATU Learn2All feature
which allows newly learnt addresses to be spanned on ports marked as
"Message Port".

This commit configures the DSA ports as Message Port. Note that this has
no effect until the Learn2All feature is enabled.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/dsa/mv88e6xxx/port.c b/drivers/net/dsa/mv88e6xxx/port.c
index 9bb0f21..40fe481 100644
--- a/drivers/net/dsa/mv88e6xxx/port.c
+++ b/drivers/net/dsa/mv88e6xxx/port.c
@@ -535,6 +535,24 @@
 
 /* Offset 0x05: Port Control 1 */
 
+int mv88e6xxx_port_set_message_port(struct mv88e6xxx_chip *chip, int port,
+				    bool message_port)
+{
+	u16 val;
+	int err;
+
+	err = mv88e6xxx_port_read(chip, port, PORT_CONTROL_1, &val);
+	if (err)
+		return err;
+
+	if (message_port)
+		val |= PORT_CONTROL_1_MESSAGE_PORT;
+	else
+		val &= ~PORT_CONTROL_1_MESSAGE_PORT;
+
+	return mv88e6xxx_port_write(chip, port, PORT_CONTROL_1, val);
+}
+
 /* Offset 0x06: Port Based VLAN Map */
 
 int mv88e6xxx_port_set_vlan_map(struct mv88e6xxx_chip *chip, int port, u16 map)