diff --git a/drivers/net/dsa/mv88e6xxx/serdes.c b/drivers/net/dsa/mv88e6xxx/serdes.c
index 55273013bfb55c5b59a72b6b7fdaff0c1c508915..2b05ead515cdcbe756ec4d34d67e823912174e49 100644
--- a/drivers/net/dsa/mv88e6xxx/serdes.c
+++ b/drivers/net/dsa/mv88e6xxx/serdes.c
@@ -830,7 +830,7 @@ int mv88e6390_serdes_power(struct mv88e6xxx_chip *chip, int port, int lane,
 			   bool up)
 {
 	u8 cmode = chip->ports[port].cmode;
-	int err = 0;
+	int err;
 
 	switch (cmode) {
 	case MV88E6XXX_PORT_STS_CMODE_SGMII:
@@ -842,6 +842,9 @@ int mv88e6390_serdes_power(struct mv88e6xxx_chip *chip, int port, int lane,
 	case MV88E6XXX_PORT_STS_CMODE_RXAUI:
 		err = mv88e6390_serdes_power_10g(chip, lane, up);
 		break;
+	default:
+		err = -EINVAL;
+		break;
 	}
 
 	if (!err && up)
@@ -1541,6 +1544,9 @@ int mv88e6393x_serdes_power(struct mv88e6xxx_chip *chip, int port, int lane,
 	case MV88E6393X_PORT_STS_CMODE_10GBASER:
 		err = mv88e6390_serdes_power_10g(chip, lane, on);
 		break;
+	default:
+		err = -EINVAL;
+		break;
 	}
 
 	if (err)