Merge branch 'pci/resource'

  - Evaluate ACPI "PCI Boot Configuration"_DSM (Benjamin Herrenschmidt)

  - Don't auto-realloc if we're preserving firmware config (Benjamin
    Herrenschmidt)

  - Allow arm64 to reallocate resources if necessary (Benjamin
    Herrenschmidt)

  - Preserve firmware config on arm64 when desired (Benjamin Herrenschmidt)

  - Simplify resource distribution to hotplug bridges (Nicholas Johnson)

* pci/resource:
  PCI: Skip resource distribution when no hotplug bridges
  PCI: Simplify pci_bus_distribute_available_resources()
  arm64: PCI: Preserve firmware configuration when desired
  arm64: PCI: Allow resource reallocation if necessary
  PCI: Don't auto-realloc if we're preserving firmware config
  PCI/ACPI: Evaluate PCI Boot Configuration _DSM

2 files changed, 45 insertions, 27 deletions

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index c36781a9b493..0d57f817ef1e 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -894,6 +894,7 @@ 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;
@@ -930,6 +931,17 @@ 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);
diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 0cdd5ff389de..79b1fa6519be 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -1684,10 +1684,15 @@ static enum enable_type pci_realloc_detect(struct pci_bus *bus,
 					   enum enable_type enable_local)
 {
 	bool unassigned = false;
+	struct pci_host_bridge *host;
 
 	if (enable_local != undefined)
 		return enable_local;
 
+	host = pci_find_host_bridge(bus);
+	if (host->preserve_config)
+		return auto_disabled;
+
 	pci_walk_bus(bus, iov_resources_unassigned, &unassigned);
 	if (unassigned)
 		return auto_enabled;
@@ -1861,16 +1866,6 @@ static void pci_bus_distribute_available_resources(struct pci_bus *bus,
 			     available_mmio_pref);
 
 	/*
-	 * Calculate the total amount of extra resource space we can
-	 * pass to bridges below this one.  This is basically the
-	 * extra space reduced by the minimal required space for the
-	 * non-hotplug bridges.
-	 */
-	remaining_io = available_io;
-	remaining_mmio = available_mmio;
-	remaining_mmio_pref = available_mmio_pref;
-
-	/*
 	 * Calculate how many hotplug bridges and normal bridges there
 	 * are on this bus.  We will distribute the additional available
 	 * resources between hotplug bridges.
@@ -1882,6 +1877,34 @@ static void pci_bus_distribute_available_resources(struct pci_bus *bus,
 			normal_bridges++;
 	}
 
+	/*
+	 * There is only one bridge on the bus so it gets all available
+	 * resources which it can then distribute to the possible hotplug
+	 * bridges below.
+	 */
+	if (hotplug_bridges + normal_bridges == 1) {
+		dev = list_first_entry(&bus->devices, struct pci_dev, bus_list);
+		if (dev->subordinate) {
+			pci_bus_distribute_available_resources(dev->subordinate,
+				add_list, available_io, available_mmio,
+				available_mmio_pref);
+		}
+		return;
+	}
+
+	if (hotplug_bridges == 0)
+		return;
+
+	/*
+	 * Calculate the total amount of extra resource space we can
+	 * pass to bridges below this one.  This is basically the
+	 * extra space reduced by the minimal required space for the
+	 * non-hotplug bridges.
+	 */
+	remaining_io = available_io;
+	remaining_mmio = available_mmio;
+	remaining_mmio_pref = available_mmio_pref;
+
 	for_each_pci_bridge(dev, bus) {
 		const struct resource *res;
 
@@ -1906,21 +1929,6 @@ static void pci_bus_distribute_available_resources(struct pci_bus *bus,
 	}
 
 	/*
-	 * There is only one bridge on the bus so it gets all available
-	 * resources which it can then distribute to the possible hotplug
-	 * bridges below.
-	 */
-	if (hotplug_bridges + normal_bridges == 1) {
-		dev = list_first_entry(&bus->devices, struct pci_dev, bus_list);
-		if (dev->subordinate) {
-			pci_bus_distribute_available_resources(dev->subordinate,
-				add_list, available_io, available_mmio,
-				available_mmio_pref);
-		}
-		return;
-	}
-
-	/*
 	 * Go over devices on this bus and distribute the remaining
 	 * resource space between hotplug bridges.
 	 */
@@ -1936,8 +1944,6 @@ static void pci_bus_distribute_available_resources(struct pci_bus *bus,
 		 * Distribute available extra resources equally between
 		 * hotplug-capable downstream ports taking alignment into
 		 * account.
-		 *
-		 * Here hotplug_bridges is always != 0.
 		 */
 		align = pci_resource_alignment(bridge, io_res);
 		io = div64_ul(available_io, hotplug_bridges);