mvpp2: refactor MTU change code

[ Upstream commit 230bd958c2c846ee292aa38bc6b006296c24ca01 ]

The MTU change code can call napi_disable() with the device already down,
leading to a deadlock. Also, lot of code is duplicated unnecessarily.

Rework mvpp2_change_mtu() to avoid the deadlock and remove duplicated code.

Fixes: 3f518509 ("ethernet: Add new driver for Marvell Armada 375 network unit")
Signed-off-by: NMatteo Croce <mcroce@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c

@@ -3501,6 +3501,7 @@ static int mvpp2_set_mac_address(struct net_device *dev, void *p)
 static int mvpp2_change_mtu(struct net_device *dev, int mtu)
 {
 	struct mvpp2_port *port = netdev_priv(dev);
+	bool running = netif_running(dev);
 	int err;
 
 	if (!IS_ALIGNED(MVPP2_RX_PKT_SIZE(mtu), 8)) {
@@ -3509,40 +3510,24 @@ static int mvpp2_change_mtu(struct net_device *dev, int mtu)
 		mtu = ALIGN(MVPP2_RX_PKT_SIZE(mtu), 8);
 	}
 
-	if (!netif_running(dev)) {
-		err = mvpp2_bm_update_mtu(dev, mtu);
-		if (!err) {
-			port->pkt_size =  MVPP2_RX_PKT_SIZE(mtu);
-			return 0;
-		}
-
-		/* Reconfigure BM to the original MTU */
-		err = mvpp2_bm_update_mtu(dev, dev->mtu);
-		if (err)
-			goto log_error;
-	}
-
+	if (running)
 		mvpp2_stop_dev(port);
 
 	err = mvpp2_bm_update_mtu(dev, mtu);
-	if (!err) {
+	if (err) {
+		netdev_err(dev, "failed to change MTU\n");
+		/* Reconfigure BM to the original MTU */
+		mvpp2_bm_update_mtu(dev, dev->mtu);
+	} else {
 		port->pkt_size =  MVPP2_RX_PKT_SIZE(mtu);
-		goto out_start;
 	}
 
-	/* Reconfigure BM to the original MTU */
-	err = mvpp2_bm_update_mtu(dev, dev->mtu);
-	if (err)
-		goto log_error;
-
-out_start:
+	if (running) {
 		mvpp2_start_dev(port);
 		mvpp2_egress_enable(port);
 		mvpp2_ingress_enable(port);
+	}
 
-	return 0;
-log_error:
-	netdev_err(dev, "failed to change MTU\n");
 	return err;
 }