net: gianfar: add support for software TX timestamping

These are required by certain network profiling applications in order to
measure delays.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Reviewed-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Link: https://lore.kernel.org/r/20220629181335.3800821-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: vladimiroltean

drivers/net/ethernet/freescale/gianfar.c

@@ -1944,6 +1944,7 @@ static netdev_tx_t gfar_start_xmit(struct sk_buff *skb, struct net_device *dev)
 		lstatus |= BD_LFLAG(TXBD_CRC | TXBD_READY) | skb_headlen(skb);
 	}
 
+	skb_tx_timestamp(skb);
 	netdev_tx_sent_queue(txq, bytes_sent);
 
 	gfar_wmb();

drivers/net/ethernet/freescale/gianfar_ethtool.c

@@ -1457,6 +1457,7 @@ static int gfar_get_ts_info(struct net_device *dev,
 
 	if (!(priv->device_flags & FSL_GIANFAR_DEV_HAS_TIMER)) {
 		info->so_timestamping = SOF_TIMESTAMPING_RX_SOFTWARE |
+					SOF_TIMESTAMPING_TX_SOFTWARE |
 					SOF_TIMESTAMPING_SOFTWARE;
 		return 0;
 	}
@@ -1474,7 +1475,10 @@ static int gfar_get_ts_info(struct net_device *dev,
 
 	info->so_timestamping = SOF_TIMESTAMPING_TX_HARDWARE |
 				SOF_TIMESTAMPING_RX_HARDWARE |
-				SOF_TIMESTAMPING_RAW_HARDWARE;
+				SOF_TIMESTAMPING_RAW_HARDWARE |
+				SOF_TIMESTAMPING_RX_SOFTWARE |
+				SOF_TIMESTAMPING_TX_SOFTWARE |
+				SOF_TIMESTAMPING_SOFTWARE;
 	info->tx_types = (1 << HWTSTAMP_TX_OFF) |
 			 (1 << HWTSTAMP_TX_ON);
 	info->rx_filters = (1 << HWTSTAMP_FILTER_NONE) |