r8169: fix DMA being used after buffer free if WoL is enabled

IOMMU errors have been reported if WoL is enabled and interface is
brought down. It turned out that the network chip triggers DMA
transfers after the DMA buffers have been freed. For WoL to work we
need to leave rx enabled, therefore simply stop the chip from being
a DMA busmaster.

Fixes: 567ca57f ("r8169: add rtl8169_up")
Tested-by: Paul Blazejowski <paulb@blazebox.homeip.net>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/realtek/r8169_main.c

@@ -4646,6 +4646,9 @@ static void rtl8169_down(struct rtl8169_private *tp)
 
 	rtl8169_update_counters(tp);
 
+	pci_clear_master(tp->pci_dev);
+	rtl_pci_commit(tp);
+
 	rtl8169_cleanup(tp, true);
 
 	rtl_prepare_power_down(tp);
@@ -4653,6 +4656,7 @@ static void rtl8169_down(struct rtl8169_private *tp)
 
 static void rtl8169_up(struct rtl8169_private *tp)
 {
+	pci_set_master(tp->pci_dev);
 	phy_resume(tp->phydev);
 	rtl8169_init_phy(tp);
 	napi_enable(&tp->napi);
@@ -5307,8 +5311,6 @@ static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 
 	rtl_hw_reset(tp);
 
-	pci_set_master(pdev);
-
 	rc = rtl_alloc_irq(tp);
 	if (rc < 0) {
 		dev_err(&pdev->dev, "Can't allocate interrupt\n");