PCI/ACPI: Reserve firmware-allocated resources for hot-added root buses

Firmware may have assigned PCI BARs for hot-added devices, so reserve
those resources before trying to allocate more.

[bhelgaas: move empty weak definition here]
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/acpi/pci_root.c

@@ -650,8 +650,10 @@ static int acpi_pci_root_start(struct acpi_device *device)
 	struct acpi_pci_root *root = acpi_driver_data(device);
 	struct acpi_pci_driver *driver;
 
-	if (system_state != SYSTEM_BOOTING)
+	if (system_state != SYSTEM_BOOTING) {
+		pcibios_resource_survey_bus(root->bus);
 		pci_assign_unassigned_bus_resources(root->bus);
+	}
 
 	mutex_lock(&acpi_pci_root_lock);
 	list_for_each_entry(driver, &acpi_pci_drivers, node)

drivers/pci/bus.c

@@ -158,6 +158,8 @@ pci_bus_alloc_resource(struct pci_bus *bus, struct resource *res,
 	return ret;
 }
 
+void __weak pcibios_resource_survey_bus(struct pci_bus *bus) { }
+
 /**
  * pci_bus_add_device - add a single device
  * @dev: device to add

include/linux/pci.h

@@ -674,6 +674,7 @@ extern struct list_head pci_root_buses;	/* list of all known PCI buses */
 /* Some device drivers need know if pci is initiated */
 extern int no_pci_devices(void);
 
+void pcibios_resource_survey_bus(struct pci_bus *bus);
 void pcibios_fixup_bus(struct pci_bus *);
 int __must_check pcibios_enable_device(struct pci_dev *, int mask);
 /* Architecture specific versions may override this (weak) */