x86/pci/mrst: Use configuration mechanism 1 for 00:00.0, 00:02.0, 00:…

…03.0

For real PCI devices 00:00.0, 00:02.0 and 00:03.0, there is either no
PCI shim, or no guarantee of data correctness of offset 256-4k.  So for
whatever reason, Linux kernel should not do MMCFG PCI config access to
those devices.  Instead, always use configuration mechanism 1 for those
devices.

The 00:00.0, 00:02.0 and 00:03.0 devices are built-in single-function
devices and are not PCI-PCI bridges, so this set of devices should be
complete.

Signed-off-by: Bin Gao <bin.gao@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

arch/x86/pci/mrst.c

@@ -141,6 +141,11 @@ static int pci_device_update_fixed(struct pci_bus *bus, unsigned int devfn,
  */
 static bool type1_access_ok(unsigned int bus, unsigned int devfn, int reg)
 {
+	if (bus == 0 && (devfn == PCI_DEVFN(2, 0)
+				|| devfn == PCI_DEVFN(0, 0)
+				|| devfn == PCI_DEVFN(3, 0)))
+		return 1;
+
 	/* This is a workaround for A0 LNC bug where PCI status register does
 	 * not have new CAP bit set. can not be written by SW either.
 	 *
@@ -150,10 +155,7 @@ static bool type1_access_ok(unsigned int bus, unsigned int devfn, int reg)
 	 */
 	if (reg >= 0x100 || reg == PCI_STATUS || reg == PCI_HEADER_TYPE)
 		return 0;
-	if (bus == 0 && (devfn == PCI_DEVFN(2, 0)
-				|| devfn == PCI_DEVFN(0, 0)
-				|| devfn == PCI_DEVFN(3, 0)))
-		return 1;
+
 	return 0; /* langwell on others */
 }