From: Prarit Bhargava <prarit@redhat.com>
Subject: [RHEL 4.6 PATCH]: Fix ACPI PCI root bridge querying time
Date: Tue, 16 Jan 2007 11:30:31 -0500
Bugzilla: 218799
Message-Id: <20070116163031.19210.76159.sendpatchset@prarit.boston.redhat.com>
Changelog: [acpi]: Fix ACPI PCI root bridge querying time


The method used to find the PCI root bridge in ACPI is very time consuming and
slow.  It doesn't scale well at all.

Backport of

http://marc.theaimsgroup.com/?l=linux-acpi&m=116528003825154&w=2

--- linux-2.6.18.orig/drivers/acpi/pci_root.c	2007-01-16 10:53:43.000000000 -0500
+++ linux-2.6.18/drivers/acpi/pci_root.c	2007-01-16 10:57:50.000000000 -0500
@@ -120,6 +120,20 @@ void acpi_pci_unregister_driver(struct a
 
 EXPORT_SYMBOL(acpi_pci_unregister_driver);
 
+acpi_handle acpi_get_pci_rootbridge_handle(unsigned int seg, unsigned int bus)
+{
+	struct acpi_pci_root *tmp;
+
+	list_for_each_entry(tmp, &acpi_pci_roots, node) {
+		if ((tmp->id.segment == (u16) seg) && (tmp->id.bus ==(u16) bus))
+			return tmp->device->handle;
+	}
+	return NULL;
+}
+
+EXPORT_SYMBOL_GPL(acpi_get_pci_rootbridge_handle);
+
+
 static acpi_status
 get_root_bridge_busnr_callback(struct acpi_resource *resource, void *data)
 {
--- linux-2.6.18.orig/drivers/acpi/glue.c	2007-01-16 10:53:43.000000000 -0500
+++ linux-2.6.18/drivers/acpi/glue.c	2007-01-16 10:56:30.000000000 -0500
@@ -86,125 +86,6 @@ static int acpi_find_bridge_device(struc
 	return ret;
 }
 
-/* Get PCI root bridge's handle from its segment and bus number */
-struct acpi_find_pci_root {
-	unsigned int seg;
-	unsigned int bus;
-	acpi_handle handle;
-};
-
-static acpi_status
-do_root_bridge_busnr_callback(struct acpi_resource *resource, void *data)
-{
-	unsigned long *busnr = (unsigned long *)data;
-	struct acpi_resource_address64 address;
-
-	if (resource->type != ACPI_RESOURCE_TYPE_ADDRESS16 &&
-	    resource->type != ACPI_RESOURCE_TYPE_ADDRESS32 &&
-	    resource->type != ACPI_RESOURCE_TYPE_ADDRESS64)
-		return AE_OK;
-
-	acpi_resource_to_address64(resource, &address);
-	if ((address.address_length > 0) &&
-	    (address.resource_type == ACPI_BUS_NUMBER_RANGE))
-		*busnr = address.minimum;
-
-	return AE_OK;
-}
-
-static int get_root_bridge_busnr(acpi_handle handle)
-{
-	acpi_status status;
-	unsigned long bus, bbn;
-	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
-
-	acpi_get_name(handle, ACPI_FULL_PATHNAME, &buffer);
-
-	status = acpi_evaluate_integer(handle, METHOD_NAME__BBN, NULL,
-				       &bbn);
-	if (status == AE_NOT_FOUND) {
-		/* Assume bus = 0 */
-		printk(KERN_INFO PREFIX
-		       "Assume root bridge [%s] bus is 0\n",
-		       (char *)buffer.pointer);
-		status = AE_OK;
-		bbn = 0;
-	}
-	if (ACPI_FAILURE(status)) {
-		bbn = -ENODEV;
-		goto exit;
-	}
-	if (bbn > 0)
-		goto exit;
-
-	/* _BBN in some systems return 0 for all root bridges */
-	bus = -1;
-	status = acpi_walk_resources(handle, METHOD_NAME__CRS,
-				     do_root_bridge_busnr_callback, &bus);
-	/* If _CRS failed, we just use _BBN */
-	if (ACPI_FAILURE(status) || (bus == -1))
-		goto exit;
-	/* We select _CRS */
-	if (bbn != bus) {
-		printk(KERN_INFO PREFIX
-		       "_BBN and _CRS returns different value for %s. Select _CRS\n",
-		       (char *)buffer.pointer);
-		bbn = bus;
-	}
-      exit:
-	kfree(buffer.pointer);
-	return (int)bbn;
-}
-
-static acpi_status
-find_pci_rootbridge(acpi_handle handle, u32 lvl, void *context, void **rv)
-{
-	struct acpi_find_pci_root *find = (struct acpi_find_pci_root *)context;
-	unsigned long seg, bus;
-	acpi_status status;
-	int tmp;
-	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
-
-	acpi_get_name(handle, ACPI_FULL_PATHNAME, &buffer);
-
-	status = acpi_evaluate_integer(handle, METHOD_NAME__SEG, NULL, &seg);
-	if (status == AE_NOT_FOUND) {
-		/* Assume seg = 0 */
-		status = AE_OK;
-		seg = 0;
-	}
-	if (ACPI_FAILURE(status)) {
-		status = AE_CTRL_DEPTH;
-		goto exit;
-	}
-
-	tmp = get_root_bridge_busnr(handle);
-	if (tmp < 0) {
-		printk(KERN_ERR PREFIX
-		       "Find root bridge failed for %s\n",
-		       (char *)buffer.pointer);
-		status = AE_CTRL_DEPTH;
-		goto exit;
-	}
-	bus = tmp;
-
-	if (seg == find->seg && bus == find->bus)
-		find->handle = handle;
-	status = AE_OK;
-      exit:
-	kfree(buffer.pointer);
-	return status;
-}
-
-acpi_handle acpi_get_pci_rootbridge_handle(unsigned int seg, unsigned int bus)
-{
-	struct acpi_find_pci_root find = { seg, bus, NULL };
-
-	acpi_get_devices(PCI_ROOT_HID_STRING, find_pci_rootbridge, &find, NULL);
-	return find.handle;
-}
-EXPORT_SYMBOL_GPL(acpi_get_pci_rootbridge_handle);
-
 /* Get device's handler per its address under its parent */
 struct acpi_find_child {
 	acpi_handle handle;