[PATCH net 1/1] igc: Fix double reset adapter triggered from a single taprio cmd

[Faizal Rahim <faizal.abdul.rahim@xxxxxxxxxxxxxxx>]

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: d3750076d464 ("igc: Add TransmissionOverrun counter")
Signed-off-by: Faizal Rahim <faizal.abdul.rahim@xxxxxxxxxxxxxxx>
---
 drivers/net/ethernet/intel/igc/igc_main.c | 33 ++++++++++++-----------
 1 file changed, 17 insertions(+), 16 deletions(-)

diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
index 87b655b839c1..33069880c86c 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c
@@ -6310,21 +6310,6 @@ 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;

@@ -6433,7 +6418,23 @@ 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;

--
2.25.1