Add a config phase for the Texas Instruments DP83TD510E ethenet PHY

The config phase currently sets the following properties from the
device tree:
  * RMII / RGMII mode (note : RMII master / slave can only be set
    by straps and cannot be changed at runtime)
  * RGMII delays. These delays can be enabled on the phy side, only
    as a boolean. Delays are enabled if phy-mode is rgmii-id, or
    rgmii-[rx|tx]id which enables only the corresponding delay.
  * In case another mode is encountered, do nothing and return
    success (keep old behavior)

Signed-off-by: Julien Blanc <julien.blanc@sprinte.eu>
---
Changes in v3:
- fix returning an uninitialized value if mode was not rgmii[-xx]
  or rmii (mii is a valid mode for this phy as well). Return
  success in that case to keep the old driver behavior.
- updated commit description accordingly

Changes in v2:
- remove the usage of phy_get_internal_delay
- use booleans to make it clear that thy phy supports only a
  fixed delay activation, no configurable delay

 drivers/net/phy/dp83td510.c | 68 +++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/drivers/net/phy/dp83td510.c b/drivers/net/phy/dp83td510.c
index 9e9a41bf6457..f47802825cfe 100644
--- a/drivers/net/phy/dp83td510.c
+++ b/drivers/net/phy/dp83td510.c
@@ -30,6 +30,12 @@
 #define DP83TD510E_INT1_LINK			BIT(13)
 #define DP83TD510E_INT1_LINK_EN			BIT(5)
 
+#define DP83TD510E_RCSR				0x17
+#define DP83TD510E_RMII_MODE_EN			BIT(5)
+#define DP83TD510E_RGMII_MODE_EN		BIT(9)
+#define DP83TD510E_TX_CLK_SHIFT			BIT(11)
+#define DP83TD510E_RX_CLK_SHIFT			BIT(12)
+
 #define DP83TD510E_CTRL				0x1f
 #define DP83TD510E_CTRL_HW_RESET		BIT(15)
 #define DP83TD510E_CTRL_SW_RESET		BIT(14)
@@ -649,6 +655,67 @@ static int dp83td510_config_aneg(struct phy_device *phydev)
 	return genphy_c45_check_and_restart_aneg(phydev, changed);
 }
 
+static bool dp83td510_config_rgmii_rx_delay(struct phy_device *phydev)
+{
+	return phydev->interface == PHY_INTERFACE_MODE_RGMII_ID ||
+	       phydev->interface == PHY_INTERFACE_MODE_RGMII_RXID;
+}
+
+static bool dp83td510_config_rgmii_tx_delay(struct phy_device *phydev)
+{
+	return phydev->interface == PHY_INTERFACE_MODE_RGMII_ID ||
+	       phydev->interface == PHY_INTERFACE_MODE_RGMII_TXID;
+}
+
+static int dp83td510_config_init(struct phy_device *phydev)
+{
+	int rgmii_delay = 0;
+	bool rx_int_delay;
+	bool tx_int_delay;
+	int ret;
+
+	if (phy_interface_is_rgmii(phydev)) {
+		rx_int_delay = dp83td510_config_rgmii_rx_delay(phydev);
+		/* Set DP83TD510E_RX_CLK_SHIFT to enable rx clk internal delay */
+		if (rx_int_delay)
+			rgmii_delay |= DP83TD510E_RX_CLK_SHIFT;
+
+		tx_int_delay = dp83td510_config_rgmii_tx_delay(phydev);
+
+		/* Set DP83TD510E_TX_CLK_SHIFT to enable tx clk internal delay */
+		if (tx_int_delay)
+			rgmii_delay |= DP83TD510E_TX_CLK_SHIFT;
+
+		ret = phy_modify_mmd(phydev, MDIO_MMD_VEND2, DP83TD510E_RCSR,
+				     DP83TD510E_RX_CLK_SHIFT | DP83TD510E_TX_CLK_SHIFT,
+				     rgmii_delay);
+		if (ret)
+			return ret;
+
+		ret = phy_set_bits_mmd(phydev, MDIO_MMD_VEND2,
+				       DP83TD510E_RCSR, DP83TD510E_RGMII_MODE_EN);
+
+		if (ret)
+			return ret;
+
+	} else if (phydev->interface == PHY_INTERFACE_MODE_RMII) {
+		// set RMII_MODE_EN, clear RGMII_MODE_EN (exclusive)
+		ret = phy_modify_mmd(phydev, MDIO_MMD_VEND2, DP83TD510E_RCSR,
+				     DP83TD510E_RMII_MODE_EN | DP83TD510E_RGMII_MODE_EN,
+				     DP83TD510E_RMII_MODE_EN);
+		if (ret)
+			return ret;
+	} else {
+		// may be RMII, which is supported, or something else. Just 
+		// return success to keep the old behavior and not break 
+		// anything. Configuration may have been done by straps so 
+		// it's better to keep as-is.
+		ret = 0;
+	}
+
+	return ret;
+}
+
 static int dp83td510_get_sqi(struct phy_device *phydev)
 {
 	int sqi, ret;
@@ -942,6 +1009,7 @@ static struct phy_driver dp83td510_driver[] = {
 	.name		= "TI DP83TD510E",
 
 	.flags          = PHY_POLL_CABLE_TEST,
+	.config_init	= dp83td510_config_init,
 	.probe		= dp83td510_probe,
 	.config_aneg	= dp83td510_config_aneg,
 	.read_status	= dp83td510_read_status,
-- 
2.47.3