igb: Add update to last_rx_timestamp in Rx rings

In order to support a more accurate check for a PTP Rx hang where the
device can no longer timestamp received packets, we need to update, per
ring, when the last Rx timestamp was. Because of how the PTP Rx hang logic
works, the current logic is valid, but properly updating the ring variable
increases the accuracy of the check.

Signed-off-by: Matthew Vick <matthew.vick@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/igb/igb.h

@@ -514,13 +514,18 @@ extern void igb_ptp_rx_rgtstamp(struct igb_q_vector *q_vector,
 extern void igb_ptp_rx_pktstamp(struct igb_q_vector *q_vector,
 				unsigned char *va,
 				struct sk_buff *skb);
-static inline void igb_ptp_rx_hwtstamp(struct igb_q_vector *q_vector,
+static inline void igb_ptp_rx_hwtstamp(struct igb_ring *rx_ring,
 				       union e1000_adv_rx_desc *rx_desc,
 				       struct sk_buff *skb)
 {
 	if (igb_test_staterr(rx_desc, E1000_RXDADV_STAT_TS) &&
 	    !igb_test_staterr(rx_desc, E1000_RXDADV_STAT_TSIP))
-		igb_ptp_rx_rgtstamp(q_vector, skb);
+		igb_ptp_rx_rgtstamp(rx_ring->q_vector, skb);
+
+	/* Update the last_rx_timestamp timer in order to enable watchdog check
+	 * for error case of latched timestamp on a dropped packet.
+	 */
+	rx_ring->last_rx_timestamp = jiffies;
 }
 
 extern int igb_ptp_hwtstamp_ioctl(struct net_device *netdev,