phy: atheros: add support for RGMII_ID, RGMII_TXID and RGMII_RXID

This adds support for internal delay on RX and TX on RGMII interface for the
AR8035 phy.

This is basically the same Linux driver do. Tested on a Zynq Zturn board (for
which u-boot support in is my tree; first patch waiting ML approval)

Signed-off-by: Andrea Merello <andrea.merello@gmail.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Acked-by: Marek Vasut <marex@denx.de>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>

drivers/net/phy/atheros.c

@@ -31,6 +31,22 @@ static int ar8035_config(struct phy_device *phydev)
 	regval = phy_read(phydev, MDIO_DEVAD_NONE, 0x1e);
 	phy_write(phydev, MDIO_DEVAD_NONE, 0x1e, (regval|0x0100));
 
+	if ((phydev->interface == PHY_INTERFACE_MODE_RGMII_ID) ||
+	    (phydev->interface == PHY_INTERFACE_MODE_RGMII_TXID)) {
+		/* select debug reg 5 */
+		phy_write(phydev, MDIO_DEVAD_NONE, 0x1D, 0x5);
+		/* enable tx delay */
+		phy_write(phydev, MDIO_DEVAD_NONE, 0x1E, 0x0100);
+	}
+
+	if ((phydev->interface == PHY_INTERFACE_MODE_RGMII_ID) ||
+	    (phydev->interface == PHY_INTERFACE_MODE_RGMII_RXID)) {
+		/* select debug reg 0 */
+		phy_write(phydev, MDIO_DEVAD_NONE, 0x1D, 0x0);
+		/* enable rx delay */
+		phy_write(phydev, MDIO_DEVAD_NONE, 0x1E, 0x8000);
+	}
+
 	phydev->supported = phydev->drv->features;
 
 	genphy_config_aneg(phydev);