igc: Add TransmissionOverrun counter

Add TransmissionOverrun as per defined by IEEE 802.1Q Bridges.
TransmissionOverrun counter shall be incremented if the implementation
detects that a frame from a given queue is still being transmitted by
the MAC when that gate-close event for that queue occurs.

This counter is utilised by the Certification conformance test to
inform the user application whether any packets are currently being
transmitted on a particular queue during a gate-close event.

Intel Discrete I225/I226 have a mechanism to not transmit a packets if
the gate open time is insufficient for the packet transmission by setting
the Strict_End bit. Thus, it is expected for this counter to be always
zero at this moment.

Inspired from enetc_taprio_stats() and enetc_taprio_queue_stats(), now
driver also report the tx_overruns counter per traffic class.

User can get this counter by using below command:
1) tc -s qdisc show dev <interface> root
2) tc -s class show dev <interface>

Test Result (Before):
class mq :1 root
Sent 1289 bytes 20 pkt (dropped 0, overlimits 0 requeues 0)
backlog 0b 0p requeues 0
class mq :2 root
Sent 124 bytes 2 pkt (dropped 0, overlimits 0 requeues 0)
backlog 0b 0p requeues 0
class mq :3 root
Sent 46028 bytes 86 pkt (dropped 0, overlimits 0 requeues 0)
backlog 0b 0p requeues 0
class mq :4 root
Sent 2596 bytes 14 pkt (dropped 0, overlimits 0 requeues 0)
backlog 0b 0p requeues 0

Test Result (After):
class taprio 100:1 root
Sent 8491 bytes 38 pkt (dropped 0, overlimits 0 requeues 0)
backlog 0b 0p requeues 0
Transmit overruns: 0
class taprio 100:2 root
Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
backlog 0b 0p requeues 0
Transmit overruns: 0
class taprio 100:3 root
Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
backlog 0b 0p requeues 0
Transmit overruns: 0
class taprio 100:4 root
Sent 994 bytes 11 pkt (dropped 0, overlimits 0 requeues 1)
backlog 0b 0p requeues 1
Transmit overruns: 0

Signed-off-by: Muhammad Husaini Zulkifli <[e-mail]>
Reviewed-by: Vladimir Oltean <[e-mail]>
Tested-by: Naama Meir <[e-mail]>
Signed-off-by: Tony Nguyen <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Paolo Abeni <[e-mail]>

drivers/net/ethernet/intel/igc/igc_main.c

···
 	return 0;
 }
 
+static void igc_taprio_stats(struct net_device *dev,
+			     struct tc_taprio_qopt_stats *stats)
+{
+	/* When Strict_End is enabled, the tx_overruns counter
+	 * will always be zero.
+	 */
+	stats->tx_overruns = 0;
+}
+
+static void igc_taprio_queue_stats(struct net_device *dev,
+				   struct tc_taprio_qopt_queue_stats *queue_stats)
+{
+	struct tc_taprio_qopt_stats *stats = &queue_stats->stats;
+
+	/* When Strict_End is enabled, the tx_overruns counter
+	 * will always be zero.
+	 */
+	stats->tx_overruns = 0;
+}
+
 static int igc_save_qbv_schedule(struct igc_adapter *adapter,
 				 struct tc_taprio_qopt_offload *qopt)
 {
···
 	size_t n;
 	int i;
 
-	if (qopt->cmd == TAPRIO_CMD_DESTROY)
+	switch (qopt->cmd) {
+	case TAPRIO_CMD_REPLACE:
+		break;
+	case TAPRIO_CMD_DESTROY:
 		return igc_tsn_clear_schedule(adapter);
-
-	if (qopt->cmd != TAPRIO_CMD_REPLACE)
+	case TAPRIO_CMD_STATS:
+		igc_taprio_stats(adapter->netdev, &qopt->stats);
+		return 0;
+	case TAPRIO_CMD_QUEUE_STATS:
+		igc_taprio_queue_stats(adapter->netdev, &qopt->queue_stats);
+		return 0;
+	default:
 		return -EOPNOTSUPP;
+	}
 
 	if (qopt->base_time < 0)
 		return -ERANGE;