net: sparx5: only return PCS for modes that require it

The RGMII ports have no PCS to configure. Make sure we only return the
PCS for port modes that require it.

Reviewed-by: Russell King (Oracle) <[email protected]>
Tested-by: Robert Marko <[email protected]>
Signed-off-by: Daniel Machon <[email protected]>
Link: https://patch.msgid.link/20241220-sparx5-lan969x-switch-driver-4-v5-5-fa8ba5dff732@microchip.com
Signed-off-by: Jakub Kicinski <[email protected]>

Author: Danielmachon

drivers/net/ethernet/microchip/sparx5/sparx5_phylink.c

@@ -32,7 +32,19 @@ sparx5_phylink_mac_select_pcs(struct phylink_config *config,
 {
 	struct sparx5_port *port = netdev_priv(to_net_dev(config->dev));
 
-	return &port->phylink_pcs;
+	/* Return the PCS for all the modes that require it. */
+	switch (interface) {
+	case PHY_INTERFACE_MODE_SGMII:
+	case PHY_INTERFACE_MODE_QSGMII:
+	case PHY_INTERFACE_MODE_1000BASEX:
+	case PHY_INTERFACE_MODE_2500BASEX:
+	case PHY_INTERFACE_MODE_5GBASER:
+	case PHY_INTERFACE_MODE_10GBASER:
+	case PHY_INTERFACE_MODE_25GBASER:
+		return &port->phylink_pcs;
+	default:
+		return NULL;
+	}
 }
 
 static void sparx5_phylink_mac_config(struct phylink_config *config,