net: fec: fix multicast filtering hardware setup

Fix hardware setup of multicast address hash:
- Never clear the hardware hash (to avoid packet loss)
- Construct the hash register values in software and then write once
to hardware

Signed-off-by: Rui Sousa <rui.sousa@nxp.com>
Signed-off-by: Fugang Duan <fugang.duan@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/fec_main.c

@@ -2910,6 +2910,7 @@ static void set_multicast_list(struct net_device *ndev)
 	struct netdev_hw_addr *ha;
 	unsigned int i, bit, data, crc, tmp;
 	unsigned char hash;
+	unsigned int hash_high = 0, hash_low = 0;
 
 	if (ndev->flags & IFF_PROMISC) {
 		tmp = readl(fep->hwp + FEC_R_CNTRL);
@@ -2932,11 +2933,7 @@ static void set_multicast_list(struct net_device *ndev)
 		return;
 	}
 
-	/* Clear filter and add the addresses in hash register
-	 */
-	writel(0, fep->hwp + FEC_GRP_HASH_TABLE_HIGH);
-	writel(0, fep->hwp + FEC_GRP_HASH_TABLE_LOW);
-
+	/* Add the addresses in hash register */
 	netdev_for_each_mc_addr(ha, ndev) {
 		/* calculate crc32 value of mac address */
 		crc = 0xffffffff;
@@ -2954,16 +2951,14 @@ static void set_multicast_list(struct net_device *ndev)
 		 */
 		hash = (crc >> (32 - FEC_HASH_BITS)) & 0x3f;
 
-		if (hash > 31) {
-			tmp = readl(fep->hwp + FEC_GRP_HASH_TABLE_HIGH);
-			tmp |= 1 << (hash - 32);
-			writel(tmp, fep->hwp + FEC_GRP_HASH_TABLE_HIGH);
-		} else {
-			tmp = readl(fep->hwp + FEC_GRP_HASH_TABLE_LOW);
-			tmp |= 1 << hash;
-			writel(tmp, fep->hwp + FEC_GRP_HASH_TABLE_LOW);
-		}
+		if (hash > 31)
+			hash_high |= 1 << (hash - 32);
+		else
+			hash_low |= 1 << hash;
 	}
+
+	writel(hash_high, fep->hwp + FEC_GRP_HASH_TABLE_HIGH);
+	writel(hash_low, fep->hwp + FEC_GRP_HASH_TABLE_LOW);
 }
 
 /* Set a MAC change in hardware. */