diff --git a/drivers/net/dsa/b53/b53_common.c b/drivers/net/dsa/b53/b53_common.c
index 8f50abe739b7..0783fc121bbb 100644
--- a/drivers/net/dsa/b53/b53_common.c
+++ b/drivers/net/dsa/b53/b53_common.c
@@ -2256,6 +2256,9 @@ static int b53_change_mtu(struct dsa_switch *ds, int port, int mtu)
 	if (is5325(dev) || is5365(dev))
 		return -EOPNOTSUPP;
 
+	if (!dsa_is_cpu_port(ds, port))
+		return 0;
+
 	enable_jumbo = (mtu >= JMS_MIN_SIZE);
 	allow_10_100 = (dev->chip_id == BCM583XX_DEVICE_ID);
 
diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
index 07c897b13de1..5b4e2ce5470d 100644
--- a/drivers/net/dsa/mv88e6xxx/chip.c
+++ b/drivers/net/dsa/mv88e6xxx/chip.c
@@ -3626,7 +3626,8 @@ static int mv88e6xxx_change_mtu(struct dsa_switch *ds, int port, int new_mtu)
 	mv88e6xxx_reg_lock(chip);
 	if (chip->info->ops->port_set_jumbo_size)
 		ret = chip->info->ops->port_set_jumbo_size(chip, port, new_mtu);
-	else if (chip->info->ops->set_max_frame_size)
+	else if (chip->info->ops->set_max_frame_size &&
+		 dsa_is_cpu_port(ds, port))
 		ret = chip->info->ops->set_max_frame_size(chip, new_mtu);
 	mv88e6xxx_reg_unlock(chip);