[PATCH v4 2/2] net: phy: realtek: Change TX-delay setting for RGMII modes only

[Serge Semin <fancer.lancer@gmail.com>]

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>

---
Changelog v3
- Accept id and rxid interface mode by clearing the TX_DELAY bit
  in this case.

Changelog v4
- Rebase onto net-next
---
 drivers/net/phy/realtek.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/net/phy/realtek.c b/drivers/net/phy/realtek.c
index cfbc0ca61123..761ce3b1e7bd 100644
--- a/drivers/net/phy/realtek.c
+++ b/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);
 }
-- 
2.21.0