net: Improve 88E151x PHY initialization

- The EEE fixup magic should also be enabled for RGMII
- Improved comments

Signed-off-by: Clemens Gruber <clemens.gruber@pqgruber.com>
Cc: Joe Hershberger <joe.hershberger@ni.com>
Cc: Hao Zhang <hzhang@ti.com>
Cc: Michal Simek <michal.simek@xilinx.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>

drivers/net/phy/marvell.c

@@ -303,24 +303,33 @@ static int m88e1518_config(struct phy_device *phydev)
 	 * As per Marvell Release Notes - Alaska 88E1510/88E1518/88E1512
 	 * /88E1514 Rev A0, Errata Section 3.1
 	 */
+
+	/* EEE initialization */
+	phy_write(phydev, MDIO_DEVAD_NONE, 22, 0x00ff);
+	phy_write(phydev, MDIO_DEVAD_NONE, 17, 0x214B);
+	phy_write(phydev, MDIO_DEVAD_NONE, 16, 0x2144);
+	phy_write(phydev, MDIO_DEVAD_NONE, 17, 0x0C28);
+	phy_write(phydev, MDIO_DEVAD_NONE, 16, 0x2146);
+	phy_write(phydev, MDIO_DEVAD_NONE, 17, 0xB233);
+	phy_write(phydev, MDIO_DEVAD_NONE, 16, 0x214D);
+	phy_write(phydev, MDIO_DEVAD_NONE, 17, 0xCC0C);
+	phy_write(phydev, MDIO_DEVAD_NONE, 16, 0x2159);
+	phy_write(phydev, MDIO_DEVAD_NONE, 22, 0x0000);
+
+	/* SGMII-to-Copper mode initialization */
 	if (phydev->interface == PHY_INTERFACE_MODE_SGMII) {
-		phy_write(phydev, MDIO_DEVAD_NONE, 22, 0x00ff);	/* page 0xff */
-		phy_write(phydev, MDIO_DEVAD_NONE, 17, 0x214B);
-		phy_write(phydev, MDIO_DEVAD_NONE, 16, 0x2144);
-		phy_write(phydev, MDIO_DEVAD_NONE, 17, 0x0C28);
-		phy_write(phydev, MDIO_DEVAD_NONE, 16, 0x2146);
-		phy_write(phydev, MDIO_DEVAD_NONE, 17, 0xB233);
-		phy_write(phydev, MDIO_DEVAD_NONE, 16, 0x214D);
-		phy_write(phydev, MDIO_DEVAD_NONE, 17, 0xCC0C);
-		phy_write(phydev, MDIO_DEVAD_NONE, 16, 0x2159);
-		phy_write(phydev, MDIO_DEVAD_NONE, 22, 0x0000);	/* reg page 0 */
-		phy_write(phydev, MDIO_DEVAD_NONE, 22, 18);    /* reg page 18 */
-		/* Write HWCFG_MODE = SGMII to Copper */
+		/* Select page 18 */
+		phy_write(phydev, MDIO_DEVAD_NONE, 22, 18);
+
+		/* In reg 20, write MODE[2:0] = 0x1 (SGMII to Copper) */
 		m88e1518_phy_writebits(phydev, 20, 0, 3, 1);
 
-		/* Phy reset */
+		/* PHY reset is necessary after changing MODE[2:0] */
 		m88e1518_phy_writebits(phydev, 20, 15, 1, 1);
-		phy_write(phydev, MDIO_DEVAD_NONE, 22, 0);     /* reg page 18 */
+
+		/* Reset page selection */
+		phy_write(phydev, MDIO_DEVAD_NONE, 22, 0);
+
 		udelay(100);
 	}