igc: Fix double reset adapter triggered from a single taprio cmd

Following the implementation of "igc: Add TransmissionOverrun counter"
patch, when a taprio command is triggered by user, igc processes two
commands: TAPRIO_CMD_REPLACE followed by TAPRIO_CMD_STATS. However, both
commands unconditionally pass through igc_tsn_offload_apply() which
evaluates and triggers reset adapter. The double reset causes issues in
the calculation of adapter->qbv_count in igc.

TAPRIO_CMD_REPLACE command is expected to reset the adapter since it
activates qbv. It's unexpected for TAPRIO_CMD_STATS to do the same
because it doesn't configure any driver-specific TSN settings. So, the
evaluation in igc_tsn_offload_apply() isn't needed for TAPRIO_CMD_STATS.

To address this, commands parsing are relocated to
igc_tsn_enable_qbv_scheduling(). Commands that don't require an adapter
reset will exit after processing, thus avoiding igc_tsn_offload_apply().

Fixes: d3750076 ("igc: Add TransmissionOverrun counter")
Signed-off-by: Faizal Rahim <faizal.abdul.rahim@linux.intel.com>
Acked-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Tested-by: Mor Bar-Gabay <morx.bar.gabay@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Link: https://patch.msgid.link/20240730173304.865479-1-anthony.l.nguyen@intel.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

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

@@ -6306,21 +6306,6 @@ static int igc_save_qbv_schedule(struct igc_adapter *adapter,
 	size_t n;
 	int i;
 
-	switch (qopt->cmd) {
-	case TAPRIO_CMD_REPLACE:
-		break;
-	case TAPRIO_CMD_DESTROY:
-		return igc_tsn_clear_schedule(adapter);
-	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;
 
@@ -6429,7 +6414,23 @@ static int igc_tsn_enable_qbv_scheduling(struct igc_adapter *adapter,
 	if (hw->mac.type != igc_i225)
 		return -EOPNOTSUPP;
 
-	err = igc_save_qbv_schedule(adapter, qopt);
+	switch (qopt->cmd) {
+	case TAPRIO_CMD_REPLACE:
+		err = igc_save_qbv_schedule(adapter, qopt);
+		break;
+	case TAPRIO_CMD_DESTROY:
+		err = igc_tsn_clear_schedule(adapter);
+		break;
+	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 (err)
 		return err;