net: enetc: reset taprio stats when taprio is deleted

Currently, the window_drop stats persist even if an incorrect Qdisc was
removed from the interface and a new one is installed. This is because
the enetc driver keeps the state, and that is persistent across multiple
Qdiscs.

To resolve the issue, clear all win_drop counters from all TX queues
when the currently active Qdisc is removed. These counters are zero
by default. The counters visible in ethtool -S are also affected,
but I don't care very much about preserving those enough to keep them
monotonically incrementing.

Fixes: 4802fca ("net: enetc: report statistics counters for taprio")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/enetc/enetc_qos.c

@@ -127,6 +127,14 @@ static int enetc_setup_taprio(struct enetc_ndev_priv *priv,
 	return 0;
 }
 
+static void enetc_reset_taprio_stats(struct enetc_ndev_priv *priv)
+{
+	int i;
+
+	for (i = 0; i < priv->num_tx_rings; i++)
+		priv->tx_ring[i]->stats.win_drop = 0;
+}
+
 static void enetc_reset_taprio(struct enetc_ndev_priv *priv)
 {
 	struct enetc_hw *hw = &priv->si->hw;
@@ -145,6 +153,7 @@ static void enetc_taprio_destroy(struct net_device *ndev)
 
 	enetc_reset_taprio(priv);
 	enetc_reset_tc_mqprio(ndev);
+	enetc_reset_taprio_stats(priv);
 }
 
 static void enetc_taprio_stats(struct net_device *ndev,