net: enetc: preserve TX ring priority across reconfiguration

In the blamed commit, a rudimentary reallocation procedure for RX buffer
descriptors was implemented, for the situation when their format changes
between normal (no PTP) and extended (PTP).

enetc_hwtstamp_set() calls enetc_close() and enetc_open() in a sequence,
and this sequence loses information which was previously configured in
the TX BDR Mode Register, specifically via the enetc_set_bdr_prio() call.
The TX ring priority is configured by tc-mqprio and tc-taprio, and
affects important things for TSN such as the TX time of packets. The
issue manifests itself most visibly by the fact that isochron --txtime
reports premature packet transmissions when PTP is first enabled on an
enetc interface.

Save the TX ring priority in a new field in struct enetc_bdr (occupies a
2 byte hole on arm64) in order to make this survive a ring reconfiguration.

Fixes: 434cebabd3a2 ("enetc: Add dynamic allocation of extended Rx BD rings")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Link: https://lore.kernel.org/r/20221122130936.1704151-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 13 insertions, 8 deletions

diff --git a/drivers/net/ethernet/freescale/enetc/enetc_qos.c b/drivers/net/ethernet/freescale/enetc/enetc_qos.c
index a842e1999122..fcebb54224c0 100644
--- a/drivers/net/ethernet/freescale/enetc/enetc_qos.c
+++ b/drivers/net/ethernet/freescale/enetc/enetc_qos.c
@@ -137,6 +137,7 @@ int enetc_setup_tc_taprio(struct net_device *ndev, void *type_data)
 	struct tc_taprio_qopt_offload *taprio = type_data;
 	struct enetc_ndev_priv *priv = netdev_priv(ndev);
 	struct enetc_hw *hw = &priv->si->hw;
+	struct enetc_bdr *tx_ring;
 	int err;
 	int i;
 
@@ -145,16 +146,20 @@ int enetc_setup_tc_taprio(struct net_device *ndev, void *type_data)
 		if (priv->tx_ring[i]->tsd_enable)
 			return -EBUSY;
 
-	for (i = 0; i < priv->num_tx_rings; i++)
-		enetc_set_bdr_prio(hw, priv->tx_ring[i]->index,
-				   taprio->enable ? i : 0);
+	for (i = 0; i < priv->num_tx_rings; i++) {
+		tx_ring = priv->tx_ring[i];
+		tx_ring->prio = taprio->enable ? i : 0;
+		enetc_set_bdr_prio(hw, tx_ring->index, tx_ring->prio);
+	}
 
 	err = enetc_setup_taprio(ndev, taprio);
-
-	if (err)
-		for (i = 0; i < priv->num_tx_rings; i++)
-			enetc_set_bdr_prio(hw, priv->tx_ring[i]->index,
-					   taprio->enable ? 0 : i);
+	if (err) {
+		for (i = 0; i < priv->num_tx_rings; i++) {
+			tx_ring = priv->tx_ring[i];
+			tx_ring->prio = taprio->enable ? 0 : i;
+			enetc_set_bdr_prio(hw, tx_ring->index, tx_ring->prio);
+		}
+	}
 
 	return err;
 }