net: dsa: mv88e6xxx: support RGMII cmode

Since the probe defaults all interfaces to the highest speed possible
(10GBASE-X in mv88e6393x) before the phy mode configuration from the
devicetree is considered it is currently impossible to use port 0 in
RGMII mode.

This change will allow RGMII modes to be configurable for port 0
enabling port 0 to be configured as RGMII as well as serial depending
on configuration.

Signed-off-by: Marcus Carlberg <marcus.carlberg@axis.com>
Link: https://lore.kernel.org/r/20220822144136.16627-1-marcus.carlberg@axis.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/mv88e6xxx/chip.c

@@ -816,6 +816,14 @@ static void mv88e6393x_phylink_get_caps(struct mv88e6xxx_chip *chip, int port,
 				MAC_10000FD;
 		}
 	}
+
+	if (port == 0) {
+		__set_bit(PHY_INTERFACE_MODE_RMII, supported);
+		__set_bit(PHY_INTERFACE_MODE_RGMII, supported);
+		__set_bit(PHY_INTERFACE_MODE_RGMII_ID, supported);
+		__set_bit(PHY_INTERFACE_MODE_RGMII_RXID, supported);
+		__set_bit(PHY_INTERFACE_MODE_RGMII_TXID, supported);
+	}
 }
 
 static void mv88e6xxx_get_caps(struct dsa_switch *ds, int port,

drivers/net/dsa/mv88e6xxx/port.c

@@ -517,6 +517,12 @@ static int mv88e6xxx_port_set_cmode(struct mv88e6xxx_chip *chip, int port,
 	case PHY_INTERFACE_MODE_RMII:
 		cmode = MV88E6XXX_PORT_STS_CMODE_RMII;
 		break;
+	case PHY_INTERFACE_MODE_RGMII:
+	case PHY_INTERFACE_MODE_RGMII_ID:
+	case PHY_INTERFACE_MODE_RGMII_RXID:
+	case PHY_INTERFACE_MODE_RGMII_TXID:
+		cmode = MV88E6XXX_PORT_STS_CMODE_RGMII;
+		break;
 	case PHY_INTERFACE_MODE_1000BASEX:
 		cmode = MV88E6XXX_PORT_STS_CMODE_1000BASEX;
 		break;
@@ -634,6 +640,19 @@ int mv88e6393x_port_set_cmode(struct mv88e6xxx_chip *chip, int port,
 	if (port != 0 && port != 9 && port != 10)
 		return -EOPNOTSUPP;
 
+	if (port == 9 || port == 10) {
+		switch (mode) {
+		case PHY_INTERFACE_MODE_RMII:
+		case PHY_INTERFACE_MODE_RGMII:
+		case PHY_INTERFACE_MODE_RGMII_ID:
+		case PHY_INTERFACE_MODE_RGMII_RXID:
+		case PHY_INTERFACE_MODE_RGMII_TXID:
+			return -EINVAL;
+		default:
+			break;
+		}
+	}
+
 	/* mv88e6393x errata 4.5: EEE should be disabled on SERDES ports */
 	err = mv88e6xxx_port_read(chip, port, MV88E6XXX_PORT_MAC_CTL, &reg);
 	if (err)