Use the phy_interface_mode_is_rgmii() function to check if the PHY mode
is set to any of: RGMII, RGMII_ID, RGMII_RXID or RGMII_TXID in the
following places:

 - When selecting the MAC PCS, make sure we return NULL in case the PHY
   mode is RGMII (as there is no PCS to configure).

 - When doing a port config, make sure we do not do the low-speed device
   configuration, in case the PHY mode is RGMII.

Note that we could also have used is_port_rgmii() here, but it makes
more sense to me to use the phylink provided functions, as we are
called by phylink, and the RGMII modes have already been validated
against the supported interfaces of the ports.

Reviewed-by: Steen Hegelund <Steen.Hegelund@microchip.com>
Reviewed-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: Daniel Machon <daniel.machon@microchip.com>
---
 drivers/net/ethernet/microchip/sparx5/sparx5_phylink.c | 3 +++
 drivers/net/ethernet/microchip/sparx5/sparx5_port.c    | 3 ++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_phylink.c b/drivers/net/ethernet/microchip/sparx5/sparx5_phylink.c
index f8562c1a894d..cb55e05e5611 100644
--- a/drivers/net/ethernet/microchip/sparx5/sparx5_phylink.c
+++ b/drivers/net/ethernet/microchip/sparx5/sparx5_phylink.c
@@ -32,6 +32,9 @@ sparx5_phylink_mac_select_pcs(struct phylink_config *config,
 {
 	struct sparx5_port *port = netdev_priv(to_net_dev(config->dev));
 
+	if (phy_interface_mode_is_rgmii(interface))
+		return NULL;
+
 	return &port->phylink_pcs;
 }
 
diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_port.c b/drivers/net/ethernet/microchip/sparx5/sparx5_port.c
index 8f4f19a2bd65..b494970752fd 100644
--- a/drivers/net/ethernet/microchip/sparx5/sparx5_port.c
+++ b/drivers/net/ethernet/microchip/sparx5/sparx5_port.c
@@ -994,6 +994,7 @@ int sparx5_port_config(struct sparx5 *sparx5,
 		       struct sparx5_port *port,
 		       struct sparx5_port_config *conf)
 {
+	bool rgmii = phy_interface_mode_is_rgmii(conf->phy_mode);
 	bool high_speed_dev = sparx5_is_baser(conf->portmode);
 	const struct sparx5_ops *ops = sparx5->data->ops;
 	int err, urgency, stop_wm;
@@ -1003,7 +1004,7 @@ int sparx5_port_config(struct sparx5 *sparx5,
 		return err;
 
 	/* high speed device is already configured */
-	if (!high_speed_dev)
+	if (!rgmii && !high_speed_dev)
 		sparx5_port_config_low_set(sparx5, port, conf);
 
 	/* Configure flow control */

-- 
2.34.1