net: stmmac: ptp: stmmac_enable(): move change of plat->flags into mutex

This is a preparation patch. The next patch will check if an external TS
is active and return with an error. So we have to move the change of the
plat->flags that tracks if external timestamping is enabled after that
check.

Prepare for this change and move the plat->flags change into the mutex
and the if (on).
Signed-off-by: Johannes Zink <j.zink@pengutronix.de>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c

@@ -192,17 +192,17 @@ static int stmmac_enable(struct ptp_clock_info *ptp,
 		write_unlock_irqrestore(&priv->ptp_lock, flags);
 		break;
 	case PTP_CLK_REQ_EXTTS:
-		if (on)
-			priv->plat->flags |= STMMAC_FLAG_EXT_SNAPSHOT_EN;
-		else
-			priv->plat->flags &= ~STMMAC_FLAG_EXT_SNAPSHOT_EN;
 		mutex_lock(&priv->aux_ts_lock);
 		acr_value = readl(ptpaddr + PTP_ACR);
 		acr_value &= ~PTP_ACR_MASK;
 		if (on) {
+			priv->plat->flags |= STMMAC_FLAG_EXT_SNAPSHOT_EN;
+
 			/* Enable External snapshot trigger */
 			acr_value |= PTP_ACR_ATSEN(rq->extts.index);
 			acr_value |= PTP_ACR_ATSFC;
+		} else {
+			priv->plat->flags &= ~STMMAC_FLAG_EXT_SNAPSHOT_EN;
 		}
 		netdev_dbg(priv->dev, "Auxiliary Snapshot %d %s.\n",
 			   rq->extts.index, on ? "enabled" : "disabled");