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path: root/drivers/acpi/pci_root.c
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Diffstat (limited to 'drivers/acpi/pci_root.c')
-rw-r--r--drivers/acpi/pci_root.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 39f5d172e84f..314a187ed572 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -881,6 +881,7 @@ struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
int node = acpi_get_node(device->handle);
struct pci_bus *bus;
struct pci_host_bridge *host_bridge;
+ union acpi_object *obj;
info->root = root;
info->bridge = device;
@@ -917,6 +918,17 @@ struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
if (!(root->osc_control_set & OSC_PCI_EXPRESS_LTR_CONTROL))
host_bridge->native_ltr = 0;
+ /*
+ * Evaluate the "PCI Boot Configuration" _DSM Function. If it
+ * exists and returns 0, we must preserve any PCI resource
+ * assignments made by firmware for this host bridge.
+ */
+ obj = acpi_evaluate_dsm(ACPI_HANDLE(bus->bridge), &pci_acpi_dsm_guid, 1,
+ IGNORE_PCI_BOOT_CONFIG_DSM, NULL);
+ if (obj && obj->type == ACPI_TYPE_INTEGER && obj->integer.value == 0)
+ host_bridge->preserve_config = 1;
+ ACPI_FREE(obj);
+
pci_scan_child_bus(bus);
pci_set_host_bridge_release(host_bridge, acpi_pci_root_release_info,
info);