net: ethernet: ti: am65-cpsw-nuss: Fix null pointer dereference for ndev

In the TX completion packet stage of TI SoCs with CPSW2G instance, which
has single external ethernet port, ndev is accessed without being
initialized if no TX packets have been processed. It results into null
pointer dereference, causing kernel to crash. Fix this by having a check
on the number of TX packets which have been processed.

Fixes: 9a369ae ("net: ethernet: ti: am65-cpsw: remove am65_cpsw_nuss_tx_compl_packets_2g()")
Signed-off-by: Nishanth Menon <[email protected]>
Signed-off-by: Chintan Vankar <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Paolo Abeni <[email protected]>

Author: nmenon

drivers/net/ethernet/ti/am65-cpsw-nuss.c

@@ -1522,7 +1522,7 @@ static int am65_cpsw_nuss_tx_compl_packets(struct am65_cpsw_common *common,
 		}
 	}
 
-	if (single_port) {
+	if (single_port && num_tx) {
 		netif_txq = netdev_get_tx_queue(ndev, chn);
 		netdev_tx_completed_queue(netif_txq, num_tx, total_bytes);
 		am65_cpsw_nuss_tx_wake(tx_chn, ndev, netif_txq);