[PATCH v2] net: dsa: mv88e6xxx: support RGMII cmode

[Marcus Carlberg <marcus.carlberg@axis.com>]

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>
---

Notes:
    v2: add phy mode input validation for SERDES only ports

 drivers/net/dsa/mv88e6xxx/port.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/net/dsa/mv88e6xxx/port.c b/drivers/net/dsa/mv88e6xxx/port.c
index 90c55f23b7c9..5c4195c635b0 100644
--- a/drivers/net/dsa/mv88e6xxx/port.c
+++ b/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)
-- 
2.20.1