r8169: add rtl_disable_exit_l1()

Add rtl_disable_exit_l1() for ensuring that the chip doesn't
inadvertently exit ASPM L1 when being in a low-power mode.
The new function is called from rtl_prepare_power_down() which
has to be moved in the code to avoid a forward declaration.

According to Realtek OCP register 0xc0ac shadows ERI register 0xd4
on RTL8168 versions from RTL8168g. This allows to simplify the
code a little.

v2:
- call rtl_disable_exit_l1() also if DASH or WoL are enabled
Suggested-by: Chun-Hao Lin <hau@realtek.com>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/realtek/r8169_main.c

@@ -2667,10 +2667,7 @@ static void rtl_enable_exit_l1(struct rtl8169_private *tp)
 	case RTL_GIGA_MAC_VER_37 ... RTL_GIGA_MAC_VER_38:
 		rtl_eri_set_bits(tp, 0xd4, 0x0c00);
 		break;
-	case RTL_GIGA_MAC_VER_40 ... RTL_GIGA_MAC_VER_53:
-		rtl_eri_set_bits(tp, 0xd4, 0x1f80);
-		break;
-	case RTL_GIGA_MAC_VER_60 ... RTL_GIGA_MAC_VER_63:
+	case RTL_GIGA_MAC_VER_40 ... RTL_GIGA_MAC_VER_63:
 		r8168_mac_ocp_modify(tp, 0xc0ac, 0, 0x1f80);
 		break;
 	default:
@@ -2678,6 +2675,20 @@ static void rtl_enable_exit_l1(struct rtl8169_private *tp)
 	}
 }
 
+static void rtl_disable_exit_l1(struct rtl8169_private *tp)
+{
+	switch (tp->mac_version) {
+	case RTL_GIGA_MAC_VER_34 ... RTL_GIGA_MAC_VER_38:
+		rtl_eri_clear_bits(tp, 0xd4, 0x1f00);
+		break;
+	case RTL_GIGA_MAC_VER_40 ... RTL_GIGA_MAC_VER_63:
+		r8168_mac_ocp_modify(tp, 0xc0ac, 0x1f80, 0);
+		break;
+	default:
+		break;
+	}
+}
+
 static void rtl_hw_aspm_clkreq_enable(struct rtl8169_private *tp, bool enable)
 {
 	/* Don't enable ASPM in the chip if OS can't control ASPM */
@@ -4702,7 +4713,7 @@ static void rtl8169_down(struct rtl8169_private *tp)
 	rtl_pci_commit(tp);
 
 	rtl8169_cleanup(tp, true);
-
+	rtl_disable_exit_l1(tp);
 	rtl_prepare_power_down(tp);
 }