diff --git a/target/linux/generic/files/drivers/net/phy/b53/b53_common.c b/target/linux/generic/files/drivers/net/phy/b53/b53_common.c
index 676e301559..d96d8b8b6d 100644
--- a/target/linux/generic/files/drivers/net/phy/b53/b53_common.c
+++ b/target/linux/generic/files/drivers/net/phy/b53/b53_common.c
@@ -1370,9 +1370,8 @@ static int b53_switch_init(struct b53_device *dev)
 			sw_dev->cpu_port = 5;
 	}
 
-	/* cpu port is always last */
-	sw_dev->ports = sw_dev->cpu_port + 1;
 	dev->enabled_ports |= BIT(sw_dev->cpu_port);
+	sw_dev->ports = fls(dev->enabled_ports);
 
 	dev->ports = devm_kzalloc(dev->dev,
 				  sizeof(struct b53_port) * sw_dev->ports,