[PATCH] USB: usb ignores 64bit dma

The dma hooks whereby EHCI can pass 64bit DMA support
up the driver stack (to avoid buffer copies) turn out
to broken on most architectures(*).  This patch just
disables them all, since it looks like those mechanisms
won't get fixed before 2.6.0-final.  For now it'd only
matter on a few big Intel boxes anyway.

Please merge.

- Dave

(*) On x86, mips, and arm dma_supported() doesn't
     even compare with the device's mask.  On several
     other architectures (reported on ppc, alpha,
     and sparc64), asking that question for non-PCI
     devices will just BUG() -- even though all info
     needed to answer the question is right at hand.

drivers/usb/host/ehci-hcd.c

@@ -426,8 +426,11 @@ static int ehci_start (struct usb_hcd *hcd)
 	 */
 	if (HCC_64BIT_ADDR (hcc_params)) {
 		writel (0, &ehci->regs->segment);
+#if 0
+// this is deeply broken on almost all architectures
 		if (!pci_set_dma_mask (ehci->hcd.pdev, 0xffffffffffffffffULL))
 			ehci_info (ehci, "enabled 64bit PCI DMA\n");
+#endif
 	}
 
 	/* help hc dma work well with cachelines */

drivers/usb/net/kaweth.c

@@ -1120,8 +1120,11 @@ static int kaweth_probe(
 
 	usb_set_intfdata(intf, kaweth);
 
+#if 0
+// dma_supported() is deeply broken on almost all architectures
 	if (dma_supported (&intf->dev, 0xffffffffffffffffULL))
 		kaweth->net->features |= NETIF_F_HIGHDMA;
+#endif
 
 	SET_NETDEV_DEV(netdev, &intf->dev);
 	if (register_netdev(netdev) != 0) {

drivers/usb/net/usbnet.c

@@ -2972,9 +2972,12 @@ usbnet_probe (struct usb_interface *udev, const struct usb_device_id *prod)
 	strcpy (net->name, "usb%d");
 	memcpy (net->dev_addr, node_id, sizeof node_id);
 
+#if 0
+// dma_supported() is deeply broken on almost all architectures
 	// possible with some EHCI controllers
 	if (dma_supported (&udev->dev, 0xffffffffffffffffULL))
 		net->features |= NETIF_F_HIGHDMA;
+#endif
 
 	net->change_mtu = usbnet_change_mtu;
 	net->get_stats = usbnet_get_stats;