mlxsw: spectrum: Implement loopback ethtool feature

Allow user to enable loopback feature for individual ports using ethtool.
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/spectrum.c

@@ -1669,6 +1669,25 @@ static int mlxsw_sp_feature_hw_tc(struct net_device *dev, bool enable)
 	return 0;
 }
 
+static int mlxsw_sp_feature_loopback(struct net_device *dev, bool enable)
+{
+	struct mlxsw_sp_port *mlxsw_sp_port = netdev_priv(dev);
+	char pplr_pl[MLXSW_REG_PPLR_LEN];
+	int err;
+
+	if (netif_running(dev))
+		mlxsw_sp_port_admin_status_set(mlxsw_sp_port, false);
+
+	mlxsw_reg_pplr_pack(pplr_pl, mlxsw_sp_port->local_port, enable);
+	err = mlxsw_reg_write(mlxsw_sp_port->mlxsw_sp->core, MLXSW_REG(pplr),
+			      pplr_pl);
+
+	if (netif_running(dev))
+		mlxsw_sp_port_admin_status_set(mlxsw_sp_port, true);
+
+	return err;
+}
+
 typedef int (*mlxsw_sp_feature_handler)(struct net_device *dev, bool enable);
 
 static int mlxsw_sp_handle_feature(struct net_device *dev,
@@ -1700,8 +1719,20 @@ static int mlxsw_sp_handle_feature(struct net_device *dev,
 static int mlxsw_sp_set_features(struct net_device *dev,
 				 netdev_features_t features)
 {
-	return mlxsw_sp_handle_feature(dev, features, NETIF_F_HW_TC,
+	netdev_features_t oper_features = dev->features;
+	int err = 0;
+
+	err |= mlxsw_sp_handle_feature(dev, features, NETIF_F_HW_TC,
 				       mlxsw_sp_feature_hw_tc);
+	err |= mlxsw_sp_handle_feature(dev, features, NETIF_F_LOOPBACK,
+				       mlxsw_sp_feature_loopback);
+
+	if (err) {
+		dev->features = oper_features;
+		return -EINVAL;
+	}
+
+	return 0;
 }
 
 static struct devlink_port *
@@ -3452,7 +3483,7 @@ static int mlxsw_sp_port_create(struct mlxsw_sp *mlxsw_sp, u8 local_port,
 
 	dev->features |= NETIF_F_NETNS_LOCAL | NETIF_F_LLTX | NETIF_F_SG |
 			 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_TC;
-	dev->hw_features |= NETIF_F_HW_TC;
+	dev->hw_features |= NETIF_F_HW_TC | NETIF_F_LOOPBACK;
 
 	dev->min_mtu = 0;
 	dev->max_mtu = ETH_MAX_MTU;