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>

2 files changed, 50 insertions, 6 deletions

diff --git a/arch/x86/pci/acpi.c b/arch/x86/pci/acpi.c
index a2f8cdb8c1d5..5f11ff6f5389 100644
--- a/arch/x86/pci/acpi.c
+++ b/arch/x86/pci/acpi.c
@@ -15,6 +15,51 @@ struct pci_root_info {
         int busnum;
 };
 
+static bool pci_use_crs = true;
+
+static int __init set_use_crs(const struct dmi_system_id *id)
+{
+        pci_use_crs = true;
+        return 0;
+}
+
+static const struct dmi_system_id pci_use_crs_table[] __initconst = {
+        /* http://bugzilla.kernel.org/show_bug.cgi?id=14183 */
+        {
+                .callback = set_use_crs,
+                .ident = "IBM System x3800",
+                .matches = {
+                        DMI_MATCH(DMI_SYS_VENDOR, "IBM"),
+                        DMI_MATCH(DMI_PRODUCT_NAME, "x3800"),
+                },
+        },
+        {}
+};
+
+void __init pci_acpi_crs_quirks(void)
+{
+        int year;
+
+        if (dmi_get_date(DMI_BIOS_DATE, &year, NULL, NULL) && year < 2008)
+                pci_use_crs = false;
+
+        dmi_check_system(pci_use_crs_table);
+
+        /*
+         * If the user specifies "pci=use_crs" or "pci=nocrs" explicitly, that
+         * takes precedence over anything we figured out above.
+         */
+        if (pci_probe & PCI_ROOT_NO_CRS)
+                pci_use_crs = false;
+        else if (pci_probe & PCI_USE__CRS)
+                pci_use_crs = true;
+
+        printk(KERN_INFO "PCI: %s host bridge windows from ACPI; "
+               "if necessary, use \"pci=%s\" and report a bug\n",
+               pci_use_crs ? "Using" : "Ignoring",
+               pci_use_crs ? "nocrs" : "use_crs");
+}
+
 static acpi_status
 resource_to_addr(struct acpi_resource *resource,
                         struct acpi_resource_address64 *addr)
@@ -106,7 +151,7 @@ setup_resource(struct acpi_resource *acpi_res, void *data)
         res->child = NULL;
         align_resource(info->bridge, res);
 
-        if (!(pci_probe & PCI_USE__CRS)) {
+        if (!pci_use_crs) {
                 dev_printk(KERN_DEBUG, &info->bridge->dev,
                            "host bridge window %pR (ignored)\n", res);
                 return AE_OK;
@@ -137,12 +182,8 @@ get_current_resources(struct acpi_device *device, int busnum,
         struct pci_root_info info;
         size_t size;
 
-        if (pci_probe & PCI_USE__CRS)
+        if (pci_use_crs)
                 pci_bus_remove_resources(bus);
-        else
-                dev_info(&device->dev,
-                         "ignoring host bridge windows from ACPI; "
-                         "boot with \"pci=use_crs\" to use them\n");
 
         info.bridge = device;
         info.bus = bus;
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;