net: enetc: implement ring reconfiguration procedure for PTP RX timestamping

The crude enetc_stop() -> enetc_open() mechanism suffers from 2
problems:

1. improper error checking
2. it involves phylink_stop() -> phylink_start() which loses the link

Right now, the driver is prepared to offer a better alternative: a ring
reconfiguration procedure which takes the RX BD size (normal or
extended) as argument. It allocates new resources (failing if that
fails), stops the traffic, and assigns the new resources to the rings.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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

@@ -2489,6 +2489,46 @@ int enetc_close(struct net_device *ndev)
 	return 0;
 }
 
+static int enetc_reconfigure(struct enetc_ndev_priv *priv, bool extended)
+{
+	struct enetc_bdr_resource *tx_res, *rx_res;
+	int err;
+
+	ASSERT_RTNL();
+
+	/* If the interface is down, do nothing. */
+	if (!netif_running(priv->ndev))
+		return 0;
+
+	tx_res = enetc_alloc_tx_resources(priv);
+	if (IS_ERR(tx_res)) {
+		err = PTR_ERR(tx_res);
+		goto out;
+	}
+
+	rx_res = enetc_alloc_rx_resources(priv, extended);
+	if (IS_ERR(rx_res)) {
+		err = PTR_ERR(rx_res);
+		goto out_free_tx_res;
+	}
+
+	enetc_stop(priv->ndev);
+	enetc_clear_bdrs(priv);
+	enetc_free_rxtx_rings(priv);
+
+	enetc_assign_tx_resources(priv, tx_res);
+	enetc_assign_rx_resources(priv, rx_res);
+	enetc_setup_bdrs(priv, extended);
+	enetc_start(priv->ndev);
+
+	return 0;
+
+out_free_tx_res:
+	enetc_free_tx_resources(tx_res, priv->num_tx_rings);
+out:
+	return err;
+}
+
 int enetc_setup_tc_mqprio(struct net_device *ndev, void *type_data)
 {
 	struct enetc_ndev_priv *priv = netdev_priv(ndev);
@@ -2681,43 +2721,47 @@ void enetc_set_features(struct net_device *ndev, netdev_features_t features)
 static int enetc_hwtstamp_set(struct net_device *ndev, struct ifreq *ifr)
 {
 	struct enetc_ndev_priv *priv = netdev_priv(ndev);
+	int err, new_offloads = priv->active_offloads;
 	struct hwtstamp_config config;
-	int ao;
 
 	if (copy_from_user(&config, ifr->ifr_data, sizeof(config)))
 		return -EFAULT;
 
 	switch (config.tx_type) {
 	case HWTSTAMP_TX_OFF:
-		priv->active_offloads &= ~ENETC_F_TX_TSTAMP_MASK;
+		new_offloads &= ~ENETC_F_TX_TSTAMP_MASK;
 		break;
 	case HWTSTAMP_TX_ON:
-		priv->active_offloads &= ~ENETC_F_TX_TSTAMP_MASK;
-		priv->active_offloads |= ENETC_F_TX_TSTAMP;
+		new_offloads &= ~ENETC_F_TX_TSTAMP_MASK;
+		new_offloads |= ENETC_F_TX_TSTAMP;
 		break;
 	case HWTSTAMP_TX_ONESTEP_SYNC:
-		priv->active_offloads &= ~ENETC_F_TX_TSTAMP_MASK;
-		priv->active_offloads |= ENETC_F_TX_ONESTEP_SYNC_TSTAMP;
+		new_offloads &= ~ENETC_F_TX_TSTAMP_MASK;
+		new_offloads |= ENETC_F_TX_ONESTEP_SYNC_TSTAMP;
 		break;
 	default:
 		return -ERANGE;
 	}
 
-	ao = priv->active_offloads;
 	switch (config.rx_filter) {
 	case HWTSTAMP_FILTER_NONE:
-		priv->active_offloads &= ~ENETC_F_RX_TSTAMP;
+		new_offloads &= ~ENETC_F_RX_TSTAMP;
 		break;
 	default:
-		priv->active_offloads |= ENETC_F_RX_TSTAMP;
+		new_offloads |= ENETC_F_RX_TSTAMP;
 		config.rx_filter = HWTSTAMP_FILTER_ALL;
 	}
 
-	if (netif_running(ndev) && ao != priv->active_offloads) {
-		enetc_close(ndev);
-		enetc_open(ndev);
+	if ((new_offloads ^ priv->active_offloads) & ENETC_F_RX_TSTAMP) {
+		bool extended = !!(new_offloads & ENETC_F_RX_TSTAMP);
+
+		err = enetc_reconfigure(priv, extended);
+		if (err)
+			return err;
 	}
 
+	priv->active_offloads = new_offloads;
+
 	return copy_to_user(ifr->ifr_data, &config, sizeof(config)) ?
 	       -EFAULT : 0;
 }