net: phy: realtek: Change TX-delay setting for RGMII modes only

It's prone to problems if delay is cleared out for other than RGMII
modes. So lets set/clear the TX-delay in the config register only
if actually RGMII-like interface mode is requested. This only
concerns rtl8211f chips.
Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/realtek.c

@@ -161,12 +161,23 @@ static int rtl8211c_config_init(struct phy_device *phydev)
 
 static int rtl8211f_config_init(struct phy_device *phydev)
 {
-	u16 val = 0;
+	u16 val;
 
-	/* enable TX-delay for rgmii-id and rgmii-txid, otherwise disable it */
-	if (phydev->interface == PHY_INTERFACE_MODE_RGMII_ID ||
-	    phydev->interface == PHY_INTERFACE_MODE_RGMII_TXID)
+	/* enable TX-delay for rgmii-{id,txid}, and disable it for rgmii and
+	 * rgmii-rxid. The RX-delay can be enabled by the external RXDLY pin.
+	 */
+	switch (phydev->interface) {
+	case PHY_INTERFACE_MODE_RGMII:
+	case PHY_INTERFACE_MODE_RGMII_RXID:
+		val = 0;
+		break;
+	case PHY_INTERFACE_MODE_RGMII_ID:
+	case PHY_INTERFACE_MODE_RGMII_TXID:
 		val = RTL8211F_TX_DELAY;
+		break;
+	default: /* the rest of the modes imply leaving delay as is. */
+		return 0;
+	}
 
 	return phy_modify_paged(phydev, 0xd08, 0x11, RTL8211F_TX_DELAY, val);
 }