net: phy: realtek: Introduce PHY_RTL8201F_S700_RMII_TIMINGS to adjust rx/tx timings

RTL8201F PHY module found on Actions Semi Cubieboard7 seems to have
specific Rx/Tx interface timings requirement for proper PHY operations.
These timing values are not documented anywhere and picked from vendor
code.

This commits lets proper packets to be transmitted over the network.

Signed-off-by: Amit Singh Tomar <amittomer25@gmail.com>
diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
index b0bd762..4e1a93b 100644
--- a/drivers/net/phy/Kconfig
+++ b/drivers/net/phy/Kconfig
@@ -235,6 +235,15 @@
 	  Default n, which means that the PHY state is not changed. To work
 	  around the issues, change this setting to y.
 
+config RTL8201F_PHY_S700_RMII_TIMINGS
+	bool "Ethernet PHY RTL8201F: adjust RMII Tx Interface timings"
+	depends on PHY_REALTEK
+	help
+	  This provides an option to configure specific timing requirements (needed
+	  for proper PHY operations) for the PHY module present on ACTION SEMI S700
+	  based cubieboard7. Exact timing requiremnets seems to be SoC specific
+	  (and it's undocumented) that comes from vendor code itself.
+
 config PHY_SMSC
 	bool  "Microchip(SMSC) Ethernet PHYs support"
 
diff --git a/drivers/net/phy/realtek.c b/drivers/net/phy/realtek.c
index feffdcc..b1b1fa5 100644
--- a/drivers/net/phy/realtek.c
+++ b/drivers/net/phy/realtek.c
@@ -14,6 +14,7 @@
 #define PHY_RTL8211x_FORCE_MASTER BIT(1)
 #define PHY_RTL8211E_PINE64_GIGABIT_FIX BIT(2)
 #define PHY_RTL8211F_FORCE_EEE_RXC_ON BIT(3)
+#define PHY_RTL8201F_S700_RMII_TIMINGS BIT(4)
 
 #define PHY_AUTONEGOTIATE_TIMEOUT 5000
 
@@ -60,6 +61,15 @@
 #define MIIM_RTL8211F_RX_DELAY		0x8
 #define MIIM_RTL8211F_LCR		0x10
 
+#define RTL8201F_RMSR			0x10
+
+#define RMSR_RX_TIMING_SHIFT		BIT(2)
+#define RMSR_RX_TIMING_MASK		GENMASK(7, 4)
+#define RMSR_RX_TIMING_VAL		0x4
+#define RMSR_TX_TIMING_SHIFT		BIT(3)
+#define RMSR_TX_TIMING_MASK		GENMASK(11, 8)
+#define RMSR_TX_TIMING_VAL		0x5
+
 static int rtl8211f_phy_extread(struct phy_device *phydev, int addr,
 				int devaddr, int regnum)
 {
@@ -114,6 +124,15 @@
 	return 0;
 }
 
+static int rtl8210f_probe(struct phy_device *phydev)
+{
+#ifdef CONFIG_RTL8201F_PHY_S700_RMII_TIMINGS
+	phydev->flags |= PHY_RTL8201F_S700_RMII_TIMINGS;
+#endif
+
+	return 0;
+}
+
 /* RealTek RTL8211x */
 static int rtl8211x_config(struct phy_device *phydev)
 {
@@ -162,6 +181,21 @@
 /* RealTek RTL8201F */
 static int rtl8201f_config(struct phy_device *phydev)
 {
+	unsigned int reg;
+
+	if (phydev->flags & PHY_RTL8201F_S700_RMII_TIMINGS) {
+		phy_write(phydev, MDIO_DEVAD_NONE, MIIM_RTL8211F_PAGE_SELECT,
+			  7);
+		reg = phy_read(phydev, MDIO_DEVAD_NONE, RTL8201F_RMSR);
+		reg &= ~(RMSR_RX_TIMING_MASK | RMSR_TX_TIMING_MASK);
+		/* Set the needed Rx/Tx Timings for proper PHY operation */
+		reg |= (RMSR_RX_TIMING_VAL << RMSR_RX_TIMING_SHIFT)
+		       | (RMSR_TX_TIMING_VAL << RMSR_TX_TIMING_SHIFT);
+		phy_write(phydev, MDIO_DEVAD_NONE, RTL8201F_RMSR, reg);
+		phy_write(phydev, MDIO_DEVAD_NONE, MIIM_RTL8211F_PAGE_SELECT,
+			  0);
+	}
+
 	genphy_config_aneg(phydev);
 
 	return 0;
@@ -412,6 +446,7 @@
 	.uid = 0x1cc816,
 	.mask = 0xffffff,
 	.features = PHY_BASIC_FEATURES,
+	.probe = &rtl8210f_probe,
 	.config = &rtl8201f_config,
 	.startup = &rtl8211e_startup,
 	.shutdown = &genphy_shutdown,