net: dsa: mv88e6xxx: Unregister MDIO bus on error path

The MDIO busses need to be unregistered before they are freed,
otherwise BUG() is called. Add a call to the unregister code if the
registration fails, since we can have multiple busses, of which some
may correctly register before one fails. This requires moving the code
around a little.

Fixes: a3c53be5 ("net: dsa: mv88e6xxx: Support multiple MDIO busses")
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx/chip.c

@@ -2177,6 +2177,19 @@ static const struct of_device_id mv88e6xxx_mdio_external_match[] = {
 	{ },
 };
 
+static void mv88e6xxx_mdios_unregister(struct mv88e6xxx_chip *chip)
+
+{
+	struct mv88e6xxx_mdio_bus *mdio_bus;
+	struct mii_bus *bus;
+
+	list_for_each_entry(mdio_bus, &chip->mdios, list) {
+		bus = mdio_bus->bus;
+
+		mdiobus_unregister(bus);
+	}
+}
+
 static int mv88e6xxx_mdios_register(struct mv88e6xxx_chip *chip,
 				    struct device_node *np)
 {
@@ -2201,27 +2214,16 @@ static int mv88e6xxx_mdios_register(struct mv88e6xxx_chip *chip,
 		match = of_match_node(mv88e6xxx_mdio_external_match, child);
 		if (match) {
 			err = mv88e6xxx_mdio_register(chip, child, true);
-			if (err)
+			if (err) {
+				mv88e6xxx_mdios_unregister(chip);
 				return err;
+			}
 		}
 	}
 
 	return 0;
 }
 
-static void mv88e6xxx_mdios_unregister(struct mv88e6xxx_chip *chip)
-
-{
-	struct mv88e6xxx_mdio_bus *mdio_bus;
-	struct mii_bus *bus;
-
-	list_for_each_entry(mdio_bus, &chip->mdios, list) {
-		bus = mdio_bus->bus;
-
-		mdiobus_unregister(bus);
-	}
-}
-
 static int mv88e6xxx_get_eeprom_len(struct dsa_switch *ds)
 {
 	struct mv88e6xxx_chip *chip = ds->priv;