net: bcmgenet: correct MIB access of UniMAC RUNT counters

commit 1ad3d225 upstream.

The gap between the Tx status counters and the Rx RUNT counters is now
being added to allow correct reporting of the registers.

Fixes: 1c1008c7 ("net: bcmgenet: add main driver file")
Signed-off-by: Doug Berger <opendmb@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/net/ethernet/broadcom/genet/bcmgenet.c

@@ -713,13 +713,16 @@ static void bcmgenet_update_mib_counters(struct bcmgenet_priv *priv)
 		switch (s->type) {
 		case BCMGENET_STAT_NETDEV:
 			continue;
-		case BCMGENET_STAT_MIB_RX:
-		case BCMGENET_STAT_MIB_TX:
 		case BCMGENET_STAT_RUNT:
-			if (s->type != BCMGENET_STAT_MIB_RX)
-				offset = BCMGENET_STAT_OFFSET;
+			offset += BCMGENET_STAT_OFFSET;
+			/* fall through */
+		case BCMGENET_STAT_MIB_TX:
+			offset += BCMGENET_STAT_OFFSET;
+			/* fall through */
+		case BCMGENET_STAT_MIB_RX:
 			val = bcmgenet_umac_readl(priv, UMAC_MIB_START +
 								j + offset);
+			offset = 0;	/* Reset Offset */
 			break;
 		case BCMGENET_STAT_MISC:
 			if (GENET_IS_V1(priv)) {