macb: restore wrap bit when performing underrun cleanup

When TX underrun occurs, a cleanup is performed that marks all buffers
as used. As a side effect it also clears the wrap bit in the last
buffer. This patch will restore the wrap bit.
Signed-off-by: Tord Andersson <tord.andersson@endian.se>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/macb.c

@@ -322,6 +322,9 @@ static void macb_tx(struct macb *bp)
 		for (i = 0; i < TX_RING_SIZE; i++)
 			bp->tx_ring[i].ctrl = MACB_BIT(TX_USED);
 
+		/* Add wrap bit */
+		bp->tx_ring[TX_RING_SIZE - 1].ctrl |= MACB_BIT(TX_WRAP);
+
 		/* free transmit buffer in upper layer*/
 		for (tail = bp->tx_tail; tail != head; tail = NEXT_TX(tail)) {
 			struct ring_info *rp = &bp->tx_skb[tail];