drivers: net: cpsw: dual_emac: fix reducing of rx descriptor during ifdown

In Dual EMAC, when both interface are up and while doing ifdown with heavy
traffic then skbs already processed by DMA from that slave emac has to be
requeued as still the other interface is up and running.

Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ti/cpsw.c

@@ -699,6 +699,28 @@ static void cpsw_rx_handler(void *token, int len, int status)
 	cpsw_dual_emac_src_port_detect(status, priv, ndev, skb);
 
 	if (unlikely(status < 0) || unlikely(!netif_running(ndev))) {
+		bool ndev_status = false;
+		struct cpsw_slave *slave = priv->slaves;
+		int n;
+
+		if (priv->data.dual_emac) {
+			/* In dual emac mode check for all interfaces */
+			for (n = priv->data.slaves; n; n--, slave++)
+				if (netif_running(slave->ndev))
+					ndev_status = true;
+		}
+
+		if (ndev_status && (status >= 0)) {
+			/* The packet received is for the interface which
+			 * is already down and the other interface is up
+			 * and running, intead of freeing which results
+			 * in reducing of the number of rx descriptor in
+			 * DMA engine, requeue skb back to cpdma.
+			 */
+			new_skb = skb;
+			goto requeue;
+		}
+
 		/* the interface is going down, skbs are purged */
 		dev_kfree_skb_any(skb);
 		return;
@@ -717,6 +739,7 @@ static void cpsw_rx_handler(void *token, int len, int status)
 		new_skb = skb;
 	}
 
+requeue:
 	ret = cpdma_chan_submit(priv->rxch, new_skb, new_skb->data,
 			skb_tailroom(new_skb), 0);
 	if (WARN_ON(ret < 0))