net: phy: realtek: add support for the 2.5Gbps PHY in RTL8125

This adds support for the integrated 2.5Gbps PHY in Realtek RTL8125.
Advertisement of 2.5Gbps mode is done via a vendor-specific register.
Same applies to reading NBase-T link partner advertisement.
Unfortunately this 2.5Gbps PHY shares the PHY ID with the integrated
1Gbps PHY's in other Realtek network chips and so far no method is
known to differentiate them. As a workaround use a dedicated fake PHY ID
that is set by the network driver by intercepting the MDIO PHY ID read.

v2:
- Create dedicated PHY driver and use a fake PHY ID that is injected by
  the network driver. Suggested by Andrew Lunn.
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/realtek.c

@@ -39,6 +39,11 @@
 #define RTL8366RB_POWER_SAVE			0x15
 #define RTL8366RB_POWER_SAVE_ON			BIT(12)
 
+#define RTL_ADV_2500FULL			BIT(7)
+#define RTL_LPADV_10000FULL			BIT(11)
+#define RTL_LPADV_5000FULL			BIT(6)
+#define RTL_LPADV_2500FULL			BIT(5)
+
 MODULE_DESCRIPTION("Realtek PHY driver");
 MODULE_AUTHOR("Johnson Leung");
 MODULE_LICENSE("GPL");
@@ -256,6 +261,53 @@ static int rtl8366rb_config_init(struct phy_device *phydev)
 	return ret;
 }
 
+static int rtl8125_get_features(struct phy_device *phydev)
+{
+	linkmode_set_bit(ETHTOOL_LINK_MODE_2500baseT_Full_BIT,
+			 phydev->supported);
+
+	return genphy_read_abilities(phydev);
+}
+
+static int rtl8125_config_aneg(struct phy_device *phydev)
+{
+	int ret = 0;
+
+	if (phydev->autoneg == AUTONEG_ENABLE) {
+		u16 adv2500 = 0;
+
+		if (linkmode_test_bit(ETHTOOL_LINK_MODE_2500baseT_Full_BIT,
+				      phydev->advertising))
+			adv2500 = RTL_ADV_2500FULL;
+
+		ret = phy_modify_paged_changed(phydev, 0xa5d, 0x12,
+					       RTL_ADV_2500FULL, adv2500);
+		if (ret < 0)
+			return ret;
+	}
+
+	return __genphy_config_aneg(phydev, ret);
+}
+
+static int rtl8125_read_status(struct phy_device *phydev)
+{
+	if (phydev->autoneg == AUTONEG_ENABLE) {
+		int lpadv = phy_read_paged(phydev, 0xa5d, 0x13);
+
+		if (lpadv < 0)
+			return lpadv;
+
+		linkmode_mod_bit(ETHTOOL_LINK_MODE_10000baseT_Full_BIT,
+			phydev->lp_advertising, lpadv & RTL_LPADV_10000FULL);
+		linkmode_mod_bit(ETHTOOL_LINK_MODE_5000baseT_Full_BIT,
+			phydev->lp_advertising, lpadv & RTL_LPADV_5000FULL);
+		linkmode_mod_bit(ETHTOOL_LINK_MODE_2500baseT_Full_BIT,
+			phydev->lp_advertising, lpadv & RTL_LPADV_2500FULL);
+	}
+
+	return genphy_read_status(phydev);
+}
+
 static struct phy_driver realtek_drvs[] = {
 	{
 		PHY_ID_MATCH_EXACT(0x00008201),
@@ -332,6 +384,16 @@ static struct phy_driver realtek_drvs[] = {
 		.resume		= genphy_resume,
 		.read_page	= rtl821x_read_page,
 		.write_page	= rtl821x_write_page,
+	}, {
+		PHY_ID_MATCH_EXACT(0x001cca50),
+		.name		= "RTL8125 2.5Gbps internal",
+		.get_features	= rtl8125_get_features,
+		.config_aneg	= rtl8125_config_aneg,
+		.read_status	= rtl8125_read_status,
+		.suspend	= genphy_suspend,
+		.resume		= genphy_resume,
+		.read_page	= rtl821x_read_page,
+		.write_page	= rtl821x_write_page,
 	}, {
 		PHY_ID_MATCH_EXACT(0x001cc961),
 		.name		= "RTL8366RB Gigabit Ethernet",