enetc: add software timestamping

Provide a software TX timestamp and add it to the ethtool query
interface.

skb_tx_timestamp() is also needed if one would like to use PHY
timestamping.
Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/enetc/enetc.c

@@ -227,6 +227,8 @@ static int enetc_map_tx_buffs(struct enetc_bdr *tx_ring, struct sk_buff *skb,
 	enetc_bdr_idx_inc(tx_ring, &i);
 	tx_ring->next_to_use = i;
 
+	skb_tx_timestamp(skb);
+
 	/* let H/W know BD ring has been updated */
 	enetc_wr_reg(tx_ring->tpir, i); /* includes wmb() */
 

drivers/net/ethernet/freescale/enetc/enetc_ethtool.c

@@ -579,6 +579,7 @@ static int enetc_get_ts_info(struct net_device *ndev,
 			   (1 << HWTSTAMP_FILTER_ALL);
 #else
 	info->so_timestamping = SOF_TIMESTAMPING_RX_SOFTWARE |
+				SOF_TIMESTAMPING_TX_SOFTWARE |
 				SOF_TIMESTAMPING_SOFTWARE;
 #endif
 	return 0;