net: ethernet: mvneta: Add back interface mode validation

When writing the serdes configuration register was moved to
mvneta_config_interface() the whole code block was removed from
mvneta_port_power_up() in the assumption that its only purpose was to
write the serdes configuration register. As mentioned by Russell King
its purpose was also to check for valid interface modes early so that
later in the driver we do not have to care for unexpected interface
modes.
Add back the test to let the driver bail out early on unhandled
interface modes.

Fixes: b474855 ("net: ethernet: mvneta: Fix Serdes configuration for SoCs without comphy")
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Reviewed-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/mvneta.c

@@ -5009,10 +5009,18 @@ static void mvneta_conf_mbus_windows(struct mvneta_port *pp,
 }
 
 /* Power up the port */
-static void mvneta_port_power_up(struct mvneta_port *pp, int phy_mode)
+static int mvneta_port_power_up(struct mvneta_port *pp, int phy_mode)
 {
 	/* MAC Cause register should be cleared */
 	mvreg_write(pp, MVNETA_UNIT_INTR_CAUSE, 0);
+
+	if (phy_mode != PHY_INTERFACE_MODE_QSGMII &&
+	    phy_mode != PHY_INTERFACE_MODE_SGMII &&
+	    !phy_interface_mode_is_8023z(phy_mode) &&
+	    !phy_interface_mode_is_rgmii(phy_mode))
+		return -EINVAL;
+
+	return 0;
 }
 
 /* Device initialization routine */
@@ -5198,7 +5206,11 @@ static int mvneta_probe(struct platform_device *pdev)
 	if (err < 0)
 		goto err_netdev;
 
-	mvneta_port_power_up(pp, phy_mode);
+	err = mvneta_port_power_up(pp, pp->phy_interface);
+	if (err < 0) {
+		dev_err(&pdev->dev, "can't power up port\n");
+		return err;
+	}
 
 	/* Armada3700 network controller does not support per-cpu
 	 * operation, so only single NAPI should be initialized.
@@ -5352,7 +5364,11 @@ static int mvneta_resume(struct device *device)
 		}
 	}
 	mvneta_defaults_set(pp);
-	mvneta_port_power_up(pp, pp->phy_interface);
+	err = mvneta_port_power_up(pp, pp->phy_interface);
+	if (err < 0) {
+		dev_err(device, "can't power up port\n");
+		return err;
+	}
 
 	netif_device_attach(dev);