x86/PCI: use host bridge _CRS info by default on 2008 and newer machines

The main benefit of using ACPI host bridge window information is that
we can do better resource allocation in systems with multiple host bridges,
e.g., http://bugzilla.kernel.org/show_bug.cgi?id=14183

Sometimes we need _CRS information even if we only have one host bridge,
e.g., https://bugs.launchpad.net/ubuntu/+source/linux/+bug/341681

Most of these systems are relatively new, so this patch turns on
"pci=use_crs" only on machines with a BIOS date of 2008 or newer.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
index d2552c68e94d..3736176acaab 100644
--- a/arch/x86/pci/common.c
+++ b/arch/x86/pci/common.c
@@ -520,6 +520,9 @@ char * __devinit  pcibios_setup(char *str)
         } else if (!strcmp(str, "use_crs")) {
                 pci_probe |= PCI_USE__CRS;
                 return NULL;
+        } else if (!strcmp(str, "nocrs")) {
+                pci_probe |= PCI_ROOT_NO_CRS;
+                return NULL;
         } else if (!strcmp(str, "earlydump")) {
                 pci_early_dump_regs = 1;
                 return NULL;