r8169: improve RTL8168g PHY suspend quirk

According to Realtek the ERI register 0x1a8 quirk is needed to work
around a hw issue with the PHY on RTL8168g. The register needs to be
changed before powering down the PHY. Currently we don't meet this
requirement, however I'm not aware of any problems caused by this.
Therefore I see the change as an improvement.

The PHY driver has no means to access the chip ERI registers,
therefore we have to intercept MDIO writes to BMCR register.
If the BMCR_PDOWN bit is going to be set, then let's apply the
quirk before actually powering down the PHY.
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/realtek/r8169_main.c

@@ -872,6 +872,25 @@ static void r8168_mac_ocp_modify(struct rtl8169_private *tp, u32 reg, u16 mask,
 	r8168_mac_ocp_write(tp, reg, (data & ~mask) | set);
 }
 
+/* Work around a hw issue with RTL8168g PHY, the quirk disables
+ * PHY MCU interrupts before PHY power-down.
+ */
+static void rtl8168g_phy_suspend_quirk(struct rtl8169_private *tp, int value)
+{
+	switch (tp->mac_version) {
+	case RTL_GIGA_MAC_VER_40:
+	case RTL_GIGA_MAC_VER_41:
+	case RTL_GIGA_MAC_VER_49:
+		if (value & BMCR_RESET || !(value & BMCR_PDOWN))
+			rtl_eri_set_bits(tp, 0x1a8, 0xfc000000);
+		else
+			rtl_eri_clear_bits(tp, 0x1a8, 0xfc000000);
+		break;
+	default:
+		break;
+	}
+};
+
 static void r8168g_mdio_write(struct rtl8169_private *tp, int reg, int value)
 {
 	if (reg == 0x1f) {
@@ -882,6 +901,9 @@ static void r8168g_mdio_write(struct rtl8169_private *tp, int reg, int value)
 	if (tp->ocp_base != OCP_STD_PHY_BASE)
 		reg -= 0x10;
 
+	if (tp->ocp_base == OCP_STD_PHY_BASE && reg == MII_BMCR)
+		rtl8168g_phy_suspend_quirk(tp, value);
+
 	r8168_phy_ocp_write(tp, tp->ocp_base + reg * 2, value);
 }
 
@@ -2210,20 +2232,8 @@ static void rtl_pll_power_down(struct rtl8169_private *tp)
 	case RTL_GIGA_MAC_VER_25 ... RTL_GIGA_MAC_VER_26:
 	case RTL_GIGA_MAC_VER_32 ... RTL_GIGA_MAC_VER_33:
 	case RTL_GIGA_MAC_VER_37:
-	case RTL_GIGA_MAC_VER_39:
-	case RTL_GIGA_MAC_VER_43:
-	case RTL_GIGA_MAC_VER_44:
-	case RTL_GIGA_MAC_VER_45:
-	case RTL_GIGA_MAC_VER_46:
-	case RTL_GIGA_MAC_VER_47:
-	case RTL_GIGA_MAC_VER_48:
-	case RTL_GIGA_MAC_VER_50 ... RTL_GIGA_MAC_VER_63:
-		RTL_W8(tp, PMCH, RTL_R8(tp, PMCH) & ~0x80);
-		break;
-	case RTL_GIGA_MAC_VER_40:
-	case RTL_GIGA_MAC_VER_41:
-	case RTL_GIGA_MAC_VER_49:
-		rtl_eri_clear_bits(tp, 0x1a8, 0xfc000000);
+	case RTL_GIGA_MAC_VER_39 ... RTL_GIGA_MAC_VER_41:
+	case RTL_GIGA_MAC_VER_43 ... RTL_GIGA_MAC_VER_63:
 		RTL_W8(tp, PMCH, RTL_R8(tp, PMCH) & ~0x80);
 		break;
 	default:
@@ -2241,20 +2251,10 @@ static void rtl_pll_power_up(struct rtl8169_private *tp)
 	case RTL_GIGA_MAC_VER_43:
 		RTL_W8(tp, PMCH, RTL_R8(tp, PMCH) | 0x80);
 		break;
-	case RTL_GIGA_MAC_VER_44:
-	case RTL_GIGA_MAC_VER_45:
-	case RTL_GIGA_MAC_VER_46:
-	case RTL_GIGA_MAC_VER_47:
-	case RTL_GIGA_MAC_VER_48:
-	case RTL_GIGA_MAC_VER_50 ... RTL_GIGA_MAC_VER_63:
+	case RTL_GIGA_MAC_VER_40 ... RTL_GIGA_MAC_VER_41:
+	case RTL_GIGA_MAC_VER_44 ... RTL_GIGA_MAC_VER_63:
 		RTL_W8(tp, PMCH, RTL_R8(tp, PMCH) | 0xc0);
 		break;
-	case RTL_GIGA_MAC_VER_40:
-	case RTL_GIGA_MAC_VER_41:
-	case RTL_GIGA_MAC_VER_49:
-		RTL_W8(tp, PMCH, RTL_R8(tp, PMCH) | 0xc0);
-		rtl_eri_set_bits(tp, 0x1a8, 0xfc000000);
-		break;
 	default:
 		break;
 	}