Revert "r8169: enable 64-bit DMA by default for PCI Express devices (v2)"

This reverts commit 35317688.

People are reporting problems due to this change and there
is no anticipation that the cause will be tracked down
any time soon.

We can try next time to selectively re-enable this based upon chip
type, or have a black list of some sort.
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/r8169.c

@@ -187,7 +187,7 @@ static DEFINE_PCI_DEVICE_TABLE(rtl8169_pci_tbl) = {
 MODULE_DEVICE_TABLE(pci, rtl8169_pci_tbl);
 
 static int rx_copybreak = 200;
-static int use_dac = -1;
+static int use_dac;
 static struct {
 	u32 msg_enable;
 } debug = { -1 };
@@ -511,8 +511,7 @@ MODULE_DESCRIPTION("RealTek RTL-8169 Gigabit Ethernet driver");
 module_param(rx_copybreak, int, 0);
 MODULE_PARM_DESC(rx_copybreak, "Copy breakpoint for copy-only-tiny-frames");
 module_param(use_dac, int, 0);
-MODULE_PARM_DESC(use_dac, "Enable PCI DAC. -1 defaults on for PCI Express only."
-" Unsafe on 32 bit PCI slot.");
+MODULE_PARM_DESC(use_dac, "Enable PCI DAC. Unsafe on 32 bit PCI slot.");
 module_param_named(debug, debug.msg_enable, int, 0);
 MODULE_PARM_DESC(debug, "Debug verbosity level (0=none, ..., 16=all)");
 MODULE_LICENSE("GPL");
@@ -2974,7 +2973,6 @@ rtl8169_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 	void __iomem *ioaddr;
 	unsigned int i;
 	int rc;
-	int this_use_dac = use_dac;
 
 	if (netif_msg_drv(&debug)) {
 		printk(KERN_INFO "%s Gigabit Ethernet driver %s loaded\n",
@@ -3040,17 +3038,8 @@ rtl8169_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 
 	tp->cp_cmd = PCIMulRW | RxChkSum;
 
-	tp->pcie_cap = pci_find_capability(pdev, PCI_CAP_ID_EXP);
-	if (!tp->pcie_cap)
-		netif_info(tp, probe, dev, "no PCI Express capability\n");
-
-	if (this_use_dac < 0)
-		this_use_dac = tp->pcie_cap != 0;
-
 	if ((sizeof(dma_addr_t) > 4) &&
-	    this_use_dac &&
-	    !pci_set_dma_mask(pdev, DMA_BIT_MASK(64))) {
-		netif_info(tp, probe, dev, "using 64-bit DMA\n");
+	    !pci_set_dma_mask(pdev, DMA_BIT_MASK(64)) && use_dac) {
 		tp->cp_cmd |= PCIDAC;
 		dev->features |= NETIF_F_HIGHDMA;
 	} else {
@@ -3069,6 +3058,10 @@ rtl8169_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 		goto err_out_free_res_4;
 	}
 
+	tp->pcie_cap = pci_find_capability(pdev, PCI_CAP_ID_EXP);
+	if (!tp->pcie_cap)
+		netif_info(tp, probe, dev, "no PCI Express capability\n");
+
 	RTL_W16(IntrMask, 0x0000);
 
 	/* Soft reset the chip. */