r8169: add PHY c45 ops for MDIO_MMD_VENDOR2 registers

JIRA: https://issues.redhat.com/browse/RHEL-75590

commit 853e803
Author: Heiner Kallweit <hkallweit1@gmail.com>
Date:   Thu Feb 13 20:15:42 2025 +0100

    r8169: add PHY c45 ops for MDIO_MMD_VENDOR2 registers

    The integrated PHYs on chip versions from RTL8168g allow to address
    MDIO_MMD_VEND2 registers. All c22 standard registers are mapped to
    MDIO_MMD_VEND2 registers. So far the paging mechanism is used to
    address PHY registers. Add support for c45 ops to address MDIO_MMD_VEND2
    registers directly, w/o the paging.

    Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
    Reviewed-by: Andrew Lunn <andrew@lunn.ch>
    Link: https://patch.msgid.link/d6f97eaa-0f13-468f-89cb-75a41087bc4a@gmail.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Signed-off-by: Izabela Bakollari <ibakolla@redhat.com>

Author: Izabela Bakollari

drivers/net/ethernet/realtek/r8169_main.c

@@ -5209,6 +5209,33 @@ static int r8169_mdio_write_reg(struct mii_bus *mii_bus, int phyaddr,
 	return 0;
 }
 
+static int r8169_mdio_read_reg_c45(struct mii_bus *mii_bus, int addr,
+				   int devnum, int regnum)
+{
+	struct rtl8169_private *tp = mii_bus->priv;
+
+	if (addr > 0)
+		return -ENODEV;
+
+	if (devnum == MDIO_MMD_VEND2 && regnum > MDIO_STAT2)
+		return r8168_phy_ocp_read(tp, regnum);
+
+	return 0;
+}
+
+static int r8169_mdio_write_reg_c45(struct mii_bus *mii_bus, int addr,
+				    int devnum, int regnum, u16 val)
+{
+	struct rtl8169_private *tp = mii_bus->priv;
+
+	if (addr > 0 || devnum != MDIO_MMD_VEND2 || regnum <= MDIO_STAT2)
+		return -ENODEV;
+
+	r8168_phy_ocp_write(tp, regnum, val);
+
+	return 0;
+}
+
 static int r8169_mdio_register(struct rtl8169_private *tp)
 {
 	struct pci_dev *pdev = tp->pci_dev;
@@ -5239,6 +5266,11 @@ static int r8169_mdio_register(struct rtl8169_private *tp)
 	new_bus->read = r8169_mdio_read_reg;
 	new_bus->write = r8169_mdio_write_reg;
 
+	if (tp->mac_version >= RTL_GIGA_MAC_VER_40) {
+		new_bus->read_c45 = r8169_mdio_read_reg_c45;
+		new_bus->write_c45 = r8169_mdio_write_reg_c45;
+	}
+
 	ret = devm_mdiobus_register(&pdev->dev, new_bus);
 	if (ret)
 		return ret;