usb: fix SB700 usb subsystem hang bug

diff -ruN a/drivers/usb/host/ehci-pci.c b/drivers/usb/host/ehci-pci.c
@@ -66,6 +66,8 @@
 {
 	struct ehci_hcd		*ehci = hcd_to_ehci(hcd);
 	struct pci_dev		*pdev = to_pci_dev(hcd->self.controller);
+	struct pci_dev		*p_smbus;
+	u8			rev;
 	u32			temp;
 	int			retval;
 

@@ -166,6 +168,25 @@
 			pci_write_config_byte(pdev, 0x4b, tmp | 0x20);
 		}
 		break;
+	case PCI_VENDOR_ID_ATI:
+		/* SB700 old version has a bug in EHCI controller,
+		 * which causes usb devices lose response in some cases.
+		 */
+		if (pdev->device == 0x4396) {
+			p_smbus = pci_get_device(PCI_VENDOR_ID_ATI,
+						 PCI_DEVICE_ID_ATI_SBX00_SMBUS,
+						 NULL);
+			if (!p_smbus)
+				break;
+			rev = p_smbus->revision;
+			if ((rev == 0x3a) || (rev == 0x3b)) {
+				u8 tmp;
+				pci_read_config_byte(pdev, 0x53, &tmp);
+				pci_write_config_byte(pdev, 0x53, tmp | (1<<3));
+			}
+			pci_dev_put(p_smbus);
+		}
+		break;
 	}
 
 	ehci_reset(ehci);