PCI: VIA CX700 quirk to disable PCI Bus Parking

PCI Bus Parking and PCI Master read caching on the VIA CX700 is buggy and
can lead to problems such as USB2.0 packet loss if a VT6212L controller
is on the PCI bus. It's disabled by default, but some BIOSes turn these
features on and this patch reverts the configuration to the safe defaults.

Signed-off-by: Tim Yamin <tim.yamin@zonbu.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/pci/quirks.c

@@ -1611,6 +1611,34 @@ DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_NVIDIA,  PCI_DEVICE_ID_NVIDIA_CK804_PCIE,
 DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_NVIDIA,  PCI_DEVICE_ID_NVIDIA_CK804_PCIE,
 			quirk_nvidia_ck804_pcie_aer_ext_cap);
 
+static void __devinit quirk_via_cx700_pci_parking_caching(struct pci_dev *dev)
+{
+	/*
+	 * Disable PCI Bus Parking and PCI Master read caching on CX700
+	 * which causes unspecified timing errors with a VT6212L on the PCI
+	 * bus leading to USB2.0 packet loss. The defaults are that these
+	 * features are turned off but some BIOSes turn them on.
+	 */
+
+	uint8_t b;
+	if (pci_read_config_byte(dev, 0x76, &b) == 0) {
+		if (b & 0x40) {
+			/* Turn off PCI Bus Parking */
+			pci_write_config_byte(dev, 0x76, b ^ 0x40);
+
+			/* Turn off PCI Master read caching */
+			pci_write_config_byte(dev, 0x72, 0x0);
+			pci_write_config_byte(dev, 0x75, 0x1);
+			pci_write_config_byte(dev, 0x77, 0x0);
+
+			printk(KERN_INFO
+				"PCI: VIA CX700 PCI parking/caching fixup on %s\n",
+				pci_name(dev));
+		}
+	}
+}
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_VIA, 0x324e, quirk_via_cx700_pci_parking_caching);
+
 #ifdef CONFIG_PCI_MSI
 /* Some chipsets do not support MSI. We cannot easily rely on setting
  * PCI_BUS_FLAGS_NO_MSI in its bus flags because there are actually