arch/powerpc/kernel/pci_of_scan.c - linux - Git at Google

 /*
  * Helper routines to scan the device tree for PCI devices and busses
  *
  * Migrated out of PowerPC architecture pci_64.c file by Grant Likely
  * <grant.likely@secretlab.ca> so that these routines are available for
  * 32 bit also.
  *
  * Copyright (C) 2003 Anton Blanchard <anton@au.ibm.com>, IBM
  *   Rework, based on alpha PCI code.
  * Copyright (c) 2009 Secret Lab Technologies Ltd.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
  * version 2 as published by the Free Software Foundation.
  */

 #include <linux/pci.h>
 #include <asm/pci-bridge.h>
 #include <asm/prom.h>

 /**
  * get_int_prop - Decode a u32 from a device tree property
  */
 static u32 get_int_prop(struct device_node *np, const char *name, u32 def)
 {
 	const u32 *prop;
 	int len;

 	prop = of_get_property(np, name, &len);
 	if (prop && len >= 4)
 		return *prop;
 	return def;
 }

 /**
  * pci_parse_of_flags - Parse the flags cell of a device tree PCI address
  * @addr0: value of 1st cell of a device tree PCI address.
  * @bridge: Set this flag if the address is from a bridge 'ranges' property
  */
 unsigned int pci_parse_of_flags(u32 addr0, int bridge)
 {
 	unsigned int flags = 0;

 	if (addr0 & 0x02000000) {
 		flags = IORESOURCE_MEM | PCI_BASE_ADDRESS_SPACE_MEMORY;
 		flags |= (addr0 >> 22) & PCI_BASE_ADDRESS_MEM_TYPE_64;
 		flags |= (addr0 >> 28) & PCI_BASE_ADDRESS_MEM_TYPE_1M;
 		if (addr0 & 0x40000000)
 			flags |= IORESOURCE_PREFETCH
 				 | PCI_BASE_ADDRESS_MEM_PREFETCH;
 		/* Note: We don't know whether the ROM has been left enabled
 		 * by the firmware or not. We mark it as disabled (ie, we do
 		 * not set the IORESOURCE_ROM_ENABLE flag) for now rather than
 		 * do a config space read, it will be force-enabled if needed
 		 */
 		if (!bridge && (addr0 & 0xff) == 0x30)
 			flags |= IORESOURCE_READONLY;
 	} else if (addr0 & 0x01000000)
 		flags = IORESOURCE_IO | PCI_BASE_ADDRESS_SPACE_IO;
 	if (flags)
 		flags |= IORESOURCE_SIZEALIGN;
 	return flags;
 }

 /**
  * of_pci_parse_addrs - Parse PCI addresses assigned in the device tree node
  * @node: device tree node for the PCI device
  * @dev: pci_dev structure for the device
  *
  * This function parses the 'assigned-addresses' property of a PCI devices'
  * device tree node and writes them into the associated pci_dev structure.
  */
 static void of_pci_parse_addrs(struct device_node *node, struct pci_dev *dev)
 {
 	u64 base, size;
 	unsigned int flags;
 	struct resource *res;
 	const u32 *addrs;
 	u32 i;
 	int proplen;

 	addrs = of_get_property(node, "assigned-addresses", &proplen);
 	if (!addrs)
 		return;
 	pr_debug("    parse addresses (%d bytes) @ %p\n", proplen, addrs);
 	for (; proplen >= 20; proplen -= 20, addrs += 5) {
 		flags = pci_parse_of_flags(addrs[0], 0);
 		if (!flags)
 			continue;
 		base = of_read_number(&addrs[1], 2);
 		size = of_read_number(&addrs[3], 2);
 		if (!size)
 			continue;
 		i = addrs[0] & 0xff;
 		pr_debug("  base: %llx, size: %llx, i: %x\n",
 			 (unsigned long long)base,
 			 (unsigned long long)size, i);

 		if (PCI_BASE_ADDRESS_0 <= i && i <= PCI_BASE_ADDRESS_5) {
 			res = &dev->resource[(i - PCI_BASE_ADDRESS_0) >> 2];
 		} else if (i == dev->rom_base_reg) {
 			res = &dev->resource[PCI_ROM_RESOURCE];
 			flags |= IORESOURCE_READONLY | IORESOURCE_CACHEABLE;
 		} else {
 			printk(KERN_ERR "PCI: bad cfg reg num 0x%x\n", i);
 			continue;
 		}
 		res->start = base;
 		res->end = base + size - 1;
 		res->flags = flags;
 		res->name = pci_name(dev);
 	}
 }

 /**
  * of_create_pci_dev - Given a device tree node on a pci bus, create a pci_dev
  * @node: device tree node pointer
  * @bus: bus the device is sitting on
  * @devfn: PCI function number, extracted from device tree by caller.
  */
 struct pci_dev *of_create_pci_dev(struct device_node *node,
 				 struct pci_bus *bus, int devfn)
 {
 	struct pci_dev *dev;
 	const char *type;
 	struct pci_slot *slot;

 	dev = alloc_pci_dev();
 	if (!dev)
 		return NULL;
 	type = of_get_property(node, "device_type", NULL);
 	if (type == NULL)
 		type = "";

 	pr_debug("    create device, devfn: %x, type: %s\n", devfn, type);

 	dev->bus = bus;
 	dev->sysdata = node;
 	dev->dev.parent = bus->bridge;
 	dev->dev.bus = &pci_bus_type;
 	dev->devfn = devfn;
 	dev->multifunction = 0;		/* maybe a lie? */
 	dev->needs_freset = 0;		/* pcie fundamental reset required */
 	set_pcie_port_type(dev);

 	list_for_each_entry(slot, &dev->bus->slots, list)
 		if (PCI_SLOT(dev->devfn) == slot->number)
 			dev->slot = slot;

 	dev->vendor = get_int_prop(node, "vendor-id", 0xffff);
 	dev->device = get_int_prop(node, "device-id", 0xffff);
 	dev->subsystem_vendor = get_int_prop(node, "subsystem-vendor-id", 0);
 	dev->subsystem_device = get_int_prop(node, "subsystem-id", 0);

 	dev->cfg_size = pci_cfg_space_size(dev);

 	dev_set_name(&dev->dev, "%04x:%02x:%02x.%d", pci_domain_nr(bus),
 		dev->bus->number, PCI_SLOT(devfn), PCI_FUNC(devfn));
 	dev->class = get_int_prop(node, "class-code", 0);
 	dev->revision = get_int_prop(node, "revision-id", 0);

 	pr_debug("    class: 0x%x\n", dev->class);
 	pr_debug("    revision: 0x%x\n", dev->revision);

 	dev->current_state = 4;		/* unknown power state */
 	dev->error_state = pci_channel_io_normal;
 	dev->dma_mask = 0xffffffff;

 	/* Early fixups, before probing the BARs */
 	pci_fixup_device(pci_fixup_early, dev);

 	if (!strcmp(type, "pci") || !strcmp(type, "pciex")) {
 		/* a PCI-PCI bridge */
 		dev->hdr_type = PCI_HEADER_TYPE_BRIDGE;
 		dev->rom_base_reg = PCI_ROM_ADDRESS1;
 		set_pcie_hotplug_bridge(dev);
 	} else if (!strcmp(type, "cardbus")) {
 		dev->hdr_type = PCI_HEADER_TYPE_CARDBUS;
 	} else {
 		dev->hdr_type = PCI_HEADER_TYPE_NORMAL;
 		dev->rom_base_reg = PCI_ROM_ADDRESS;
 		/* Maybe do a default OF mapping here */
 		dev->irq = NO_IRQ;
 	}

 	of_pci_parse_addrs(node, dev);

 	pr_debug("    adding to system ...\n");

 	pci_device_add(dev, bus);

 	return dev;
 }
 EXPORT_SYMBOL(of_create_pci_dev);

 /**
  * of_scan_pci_bridge - Set up a PCI bridge and scan for child nodes
  * @node: device tree node of bridge
  * @dev: pci_dev structure for the bridge
  *
  * of_scan_bus() calls this routine for each PCI bridge that it finds, and
  * this routine in turn call of_scan_bus() recusively to scan for more child
  * devices.
  */
 void __devinit of_scan_pci_bridge(struct device_node *node,
 				  struct pci_dev *dev)
 {
 	struct pci_bus *bus;
 	const u32 *busrange, *ranges;
 	int len, i, mode;
 	struct resource *res;
 	unsigned int flags;
 	u64 size;

 	pr_debug("of_scan_pci_bridge(%s)\n", node->full_name);

 	/* parse bus-range property */
 	busrange = of_get_property(node, "bus-range", &len);
 	if (busrange == NULL || len != 8) {
 		printk(KERN_DEBUG "Can't get bus-range for PCI-PCI bridge %s\n",
 		       node->full_name);
 		return;
 	}
 	ranges = of_get_property(node, "ranges", &len);
 	if (ranges == NULL) {
 		printk(KERN_DEBUG "Can't get ranges for PCI-PCI bridge %s\n",
 		       node->full_name);
 		return;
 	}

 	bus = pci_add_new_bus(dev->bus, dev, busrange[0]);
 	if (!bus) {
 		printk(KERN_ERR "Failed to create pci bus for %s\n",
 		       node->full_name);
 		return;
 	}

 	bus->primary = dev->bus->number;
 	bus->subordinate = busrange[1];
 	bus->bridge_ctl = 0;
 	bus->sysdata = node;

 	/* parse ranges property */
 	/* PCI #address-cells == 3 and #size-cells == 2 always */
 	res = &dev->resource[PCI_BRIDGE_RESOURCES];
 	for (i = 0; i < PCI_NUM_RESOURCES - PCI_BRIDGE_RESOURCES; ++i) {
 		res->flags = 0;
 		bus->resource[i] = res;
 		++res;
 	}
 	i = 1;
 	for (; len >= 32; len -= 32, ranges += 8) {
 		flags = pci_parse_of_flags(ranges[0], 1);
 		size = of_read_number(&ranges[6], 2);
 		if (flags == 0 || size == 0)
 			continue;
 		if (flags & IORESOURCE_IO) {
 			res = bus->resource[0];
 			if (res->flags) {
 				printk(KERN_ERR "PCI: ignoring extra I/O range"
 				       " for bridge %s\n", node->full_name);
 				continue;
 			}
 		} else {
 			if (i >= PCI_NUM_RESOURCES - PCI_BRIDGE_RESOURCES) {
 				printk(KERN_ERR "PCI: too many memory ranges"
 				       " for bridge %s\n", node->full_name);
 				continue;
 			}
 			res = bus->resource[i];
 			++i;
 		}
 		res->start = of_read_number(&ranges[1], 2);
 		res->end = res->start + size - 1;
 		res->flags = flags;
 	}
 	sprintf(bus->name, "PCI Bus %04x:%02x", pci_domain_nr(bus),
 		bus->number);
 	pr_debug("    bus name: %s\n", bus->name);

 	mode = PCI_PROBE_NORMAL;
 	if (ppc_md.pci_probe_mode)
 		mode = ppc_md.pci_probe_mode(bus);
 	pr_debug("    probe mode: %d\n", mode);

 	if (mode == PCI_PROBE_DEVTREE)
 		of_scan_bus(node, bus);
 	else if (mode == PCI_PROBE_NORMAL)
 		pci_scan_child_bus(bus);
 }
 EXPORT_SYMBOL(of_scan_pci_bridge);

 /**
  * __of_scan_bus - given a PCI bus node, setup bus and scan for child devices
  * @node: device tree node for the PCI bus
  * @bus: pci_bus structure for the PCI bus
  * @rescan_existing: Flag indicating bus has already been set up
  */
 static void __devinit __of_scan_bus(struct device_node *node,
 				    struct pci_bus *bus, int rescan_existing)
 {
 	struct device_node *child;
 	const u32 *reg;
 	int reglen, devfn;
 	struct pci_dev *dev;

 	pr_debug("of_scan_bus(%s) bus no %d...\n",
 		 node->full_name, bus->number);

 	/* Scan direct children */
 	for_each_child_of_node(node, child) {
 		pr_debug("  * %s\n", child->full_name);
 		if (!of_device_is_available(child))
 			continue;
 		reg = of_get_property(child, "reg", &reglen);
 		if (reg == NULL || reglen < 20)
 			continue;
 		devfn = (reg[0] >> 8) & 0xff;

 		/* create a new pci_dev for this device */
 		dev = of_create_pci_dev(child, bus, devfn);
 		if (!dev)
 			continue;
 		pr_debug("    dev header type: %x\n", dev->hdr_type);
 	}

 	/* Apply all fixups necessary. We don't fixup the bus "self"
 	 * for an existing bridge that is being rescanned
 	 */
 	if (!rescan_existing)
 		pcibios_setup_bus_self(bus);
 	pcibios_setup_bus_devices(bus);

 	/* Now scan child busses */
 	list_for_each_entry(dev, &bus->devices, bus_list) {
 		if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE ||
 		    dev->hdr_type == PCI_HEADER_TYPE_CARDBUS) {
 			struct device_node *child = pci_device_to_OF_node(dev);
 			if (child)
 				of_scan_pci_bridge(child, dev);
 		}
 	}
 }

 /**
  * of_scan_bus - given a PCI bus node, setup bus and scan for child devices
  * @node: device tree node for the PCI bus
  * @bus: pci_bus structure for the PCI bus
  */
 void __devinit of_scan_bus(struct device_node *node,
 			   struct pci_bus *bus)
 {
 	__of_scan_bus(node, bus, 0);
 }
 EXPORT_SYMBOL_GPL(of_scan_bus);

 /**
  * of_rescan_bus - given a PCI bus node, scan for child devices
  * @node: device tree node for the PCI bus
  * @bus: pci_bus structure for the PCI bus
  *
  * Same as of_scan_bus, but for a pci_bus structure that has already been
  * setup.
  */
 void __devinit of_rescan_bus(struct device_node *node,
 			     struct pci_bus *bus)
 {
 	__of_scan_bus(node, bus, 1);
 }
 EXPORT_SYMBOL_GPL(of_rescan_bus);
	/*
	* Helper routines to scan the device tree for PCI devices and busses
	*
	* Migrated out of PowerPC architecture pci_64.c file by Grant Likely
	* <grant.likely@secretlab.ca> so that these routines are available for
	* 32 bit also.
	*
	* Copyright (C) 2003 Anton Blanchard <anton@au.ibm.com>, IBM
	* Rework, based on alpha PCI code.
	* Copyright (c) 2009 Secret Lab Technologies Ltd.
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License
	* version 2 as published by the Free Software Foundation.
	*/

	#include <linux/pci.h>
	#include <asm/pci-bridge.h>
	#include <asm/prom.h>

	/**
	* get_int_prop - Decode a u32 from a device tree property
	*/
	static u32 get_int_prop(struct device_node np, const char name, u32 def)
	{
	const u32 *prop;
	int len;

	prop = of_get_property(np, name, &len);
	if (prop && len >= 4)
	return *prop;
	return def;
	}

	/**
	* pci_parse_of_flags - Parse the flags cell of a device tree PCI address
	* @addr0: value of 1st cell of a device tree PCI address.
	* @bridge: Set this flag if the address is from a bridge 'ranges' property
	*/
	unsigned int pci_parse_of_flags(u32 addr0, int bridge)
	{
	unsigned int flags = 0;

	if (addr0 & 0x02000000) {
	flags = IORESOURCE_MEM \| PCI_BASE_ADDRESS_SPACE_MEMORY;
	flags \|= (addr0 >> 22) & PCI_BASE_ADDRESS_MEM_TYPE_64;
	flags \|= (addr0 >> 28) & PCI_BASE_ADDRESS_MEM_TYPE_1M;
	if (addr0 & 0x40000000)
	flags \|= IORESOURCE_PREFETCH
	\| PCI_BASE_ADDRESS_MEM_PREFETCH;
	/* Note: We don't know whether the ROM has been left enabled
	* by the firmware or not. We mark it as disabled (ie, we do
	* not set the IORESOURCE_ROM_ENABLE flag) for now rather than
	* do a config space read, it will be force-enabled if needed
	*/
	if (!bridge && (addr0 & 0xff) == 0x30)
	flags \|= IORESOURCE_READONLY;
	} else if (addr0 & 0x01000000)
	flags = IORESOURCE_IO \| PCI_BASE_ADDRESS_SPACE_IO;
	if (flags)
	flags \|= IORESOURCE_SIZEALIGN;
	return flags;
	}

	/**
	* of_pci_parse_addrs - Parse PCI addresses assigned in the device tree node
	* @node: device tree node for the PCI device
	* @dev: pci_dev structure for the device
	*
	* This function parses the 'assigned-addresses' property of a PCI devices'
	* device tree node and writes them into the associated pci_dev structure.
	*/
	static void of_pci_parse_addrs(struct device_node node, struct pci_dev dev)
	{
	u64 base, size;
	unsigned int flags;
	struct resource *res;
	const u32 *addrs;
	u32 i;
	int proplen;

	addrs = of_get_property(node, "assigned-addresses", &proplen);
	if (!addrs)
	return;
	pr_debug(" parse addresses (%d bytes) @ %p\n", proplen, addrs);
	for (; proplen >= 20; proplen -= 20, addrs += 5) {
	flags = pci_parse_of_flags(addrs[0], 0);
	if (!flags)
	continue;
	base = of_read_number(&addrs[1], 2);
	size = of_read_number(&addrs[3], 2);
	if (!size)
	continue;
	i = addrs[0] & 0xff;
	pr_debug(" base: %llx, size: %llx, i: %x\n",
	(unsigned long long)base,
	(unsigned long long)size, i);

	if (PCI_BASE_ADDRESS_0 <= i && i <= PCI_BASE_ADDRESS_5) {
	res = &dev->resource[(i - PCI_BASE_ADDRESS_0) >> 2];
	} else if (i == dev->rom_base_reg) {
	res = &dev->resource[PCI_ROM_RESOURCE];
	flags \|= IORESOURCE_READONLY \| IORESOURCE_CACHEABLE;
	} else {
	printk(KERN_ERR "PCI: bad cfg reg num 0x%x\n", i);
	continue;
	}
	res->start = base;
	res->end = base + size - 1;
	res->flags = flags;
	res->name = pci_name(dev);
	}
	}

	/**
	* of_create_pci_dev - Given a device tree node on a pci bus, create a pci_dev
	* @node: device tree node pointer
	* @bus: bus the device is sitting on
	* @devfn: PCI function number, extracted from device tree by caller.
	*/
	struct pci_dev of_create_pci_dev(struct device_node node,
	struct pci_bus *bus, int devfn)
	{
	struct pci_dev *dev;
	const char *type;
	struct pci_slot *slot;

	dev = alloc_pci_dev();
	if (!dev)
	return NULL;
	type = of_get_property(node, "device_type", NULL);
	if (type == NULL)
	type = "";

	pr_debug(" create device, devfn: %x, type: %s\n", devfn, type);

	dev->bus = bus;
	dev->sysdata = node;
	dev->dev.parent = bus->bridge;
	dev->dev.bus = &pci_bus_type;
	dev->devfn = devfn;
	dev->multifunction = 0; /* maybe a lie? */
	dev->needs_freset = 0; /* pcie fundamental reset required */
	set_pcie_port_type(dev);

	list_for_each_entry(slot, &dev->bus->slots, list)
	if (PCI_SLOT(dev->devfn) == slot->number)
	dev->slot = slot;

	dev->vendor = get_int_prop(node, "vendor-id", 0xffff);
	dev->device = get_int_prop(node, "device-id", 0xffff);
	dev->subsystem_vendor = get_int_prop(node, "subsystem-vendor-id", 0);
	dev->subsystem_device = get_int_prop(node, "subsystem-id", 0);

	dev->cfg_size = pci_cfg_space_size(dev);

	dev_set_name(&dev->dev, "%04x:%02x:%02x.%d", pci_domain_nr(bus),
	dev->bus->number, PCI_SLOT(devfn), PCI_FUNC(devfn));
	dev->class = get_int_prop(node, "class-code", 0);
	dev->revision = get_int_prop(node, "revision-id", 0);

	pr_debug(" class: 0x%x\n", dev->class);
	pr_debug(" revision: 0x%x\n", dev->revision);

	dev->current_state = 4; /* unknown power state */
	dev->error_state = pci_channel_io_normal;
	dev->dma_mask = 0xffffffff;

	/* Early fixups, before probing the BARs */
	pci_fixup_device(pci_fixup_early, dev);

	if (!strcmp(type, "pci") \|\| !strcmp(type, "pciex")) {
	/* a PCI-PCI bridge */
	dev->hdr_type = PCI_HEADER_TYPE_BRIDGE;
	dev->rom_base_reg = PCI_ROM_ADDRESS1;
	set_pcie_hotplug_bridge(dev);
	} else if (!strcmp(type, "cardbus")) {
	dev->hdr_type = PCI_HEADER_TYPE_CARDBUS;
	} else {
	dev->hdr_type = PCI_HEADER_TYPE_NORMAL;
	dev->rom_base_reg = PCI_ROM_ADDRESS;
	/* Maybe do a default OF mapping here */
	dev->irq = NO_IRQ;
	}

	of_pci_parse_addrs(node, dev);

	pr_debug(" adding to system ...\n");

	pci_device_add(dev, bus);

	return dev;
	}
	EXPORT_SYMBOL(of_create_pci_dev);

	/**
	* of_scan_pci_bridge - Set up a PCI bridge and scan for child nodes
	* @node: device tree node of bridge
	* @dev: pci_dev structure for the bridge
	*
	* of_scan_bus() calls this routine for each PCI bridge that it finds, and
	* this routine in turn call of_scan_bus() recusively to scan for more child
	* devices.
	*/
	void __devinit of_scan_pci_bridge(struct device_node *node,
	struct pci_dev *dev)
	{
	struct pci_bus *bus;
	const u32 busrange, ranges;
	int len, i, mode;
	struct resource *res;
	unsigned int flags;
	u64 size;

	pr_debug("of_scan_pci_bridge(%s)\n", node->full_name);

	/* parse bus-range property */
	busrange = of_get_property(node, "bus-range", &len);
	if (busrange == NULL \|\| len != 8) {
	printk(KERN_DEBUG "Can't get bus-range for PCI-PCI bridge %s\n",
	node->full_name);
	return;
	}
	ranges = of_get_property(node, "ranges", &len);
	if (ranges == NULL) {
	printk(KERN_DEBUG "Can't get ranges for PCI-PCI bridge %s\n",
	node->full_name);
	return;
	}

	bus = pci_add_new_bus(dev->bus, dev, busrange[0]);
	if (!bus) {
	printk(KERN_ERR "Failed to create pci bus for %s\n",
	node->full_name);
	return;
	}

	bus->primary = dev->bus->number;
	bus->subordinate = busrange[1];
	bus->bridge_ctl = 0;
	bus->sysdata = node;

	/* parse ranges property */
	/* PCI #address-cells == 3 and #size-cells == 2 always */
	res = &dev->resource[PCI_BRIDGE_RESOURCES];
	for (i = 0; i < PCI_NUM_RESOURCES - PCI_BRIDGE_RESOURCES; ++i) {
	res->flags = 0;
	bus->resource[i] = res;
	++res;
	}
	i = 1;
	for (; len >= 32; len -= 32, ranges += 8) {
	flags = pci_parse_of_flags(ranges[0], 1);
	size = of_read_number(&ranges[6], 2);
	if (flags == 0 \|\| size == 0)
	continue;
	if (flags & IORESOURCE_IO) {
	res = bus->resource[0];
	if (res->flags) {
	printk(KERN_ERR "PCI: ignoring extra I/O range"
	" for bridge %s\n", node->full_name);
	continue;
	}
	} else {
	if (i >= PCI_NUM_RESOURCES - PCI_BRIDGE_RESOURCES) {
	printk(KERN_ERR "PCI: too many memory ranges"
	" for bridge %s\n", node->full_name);
	continue;
	}
	res = bus->resource[i];
	++i;
	}
	res->start = of_read_number(&ranges[1], 2);
	res->end = res->start + size - 1;
	res->flags = flags;
	}
	sprintf(bus->name, "PCI Bus %04x:%02x", pci_domain_nr(bus),
	bus->number);
	pr_debug(" bus name: %s\n", bus->name);

	mode = PCI_PROBE_NORMAL;
	if (ppc_md.pci_probe_mode)
	mode = ppc_md.pci_probe_mode(bus);
	pr_debug(" probe mode: %d\n", mode);

	if (mode == PCI_PROBE_DEVTREE)
	of_scan_bus(node, bus);
	else if (mode == PCI_PROBE_NORMAL)
	pci_scan_child_bus(bus);
	}
	EXPORT_SYMBOL(of_scan_pci_bridge);

	/**
	* __of_scan_bus - given a PCI bus node, setup bus and scan for child devices
	* @node: device tree node for the PCI bus
	* @bus: pci_bus structure for the PCI bus
	* @rescan_existing: Flag indicating bus has already been set up
	*/
	static void __devinit __of_scan_bus(struct device_node *node,
	struct pci_bus *bus, int rescan_existing)
	{
	struct device_node *child;
	const u32 *reg;
	int reglen, devfn;
	struct pci_dev *dev;

	pr_debug("of_scan_bus(%s) bus no %d...\n",
	node->full_name, bus->number);

	/* Scan direct children */
	for_each_child_of_node(node, child) {
	pr_debug(" * %s\n", child->full_name);
	if (!of_device_is_available(child))
	continue;
	reg = of_get_property(child, "reg", &reglen);
	if (reg == NULL \|\| reglen < 20)
	continue;
	devfn = (reg[0] >> 8) & 0xff;

	/* create a new pci_dev for this device */
	dev = of_create_pci_dev(child, bus, devfn);
	if (!dev)
	continue;
	pr_debug(" dev header type: %x\n", dev->hdr_type);
	}

	/* Apply all fixups necessary. We don't fixup the bus "self"
	* for an existing bridge that is being rescanned
	*/
	if (!rescan_existing)
	pcibios_setup_bus_self(bus);
	pcibios_setup_bus_devices(bus);

	/* Now scan child busses */
	list_for_each_entry(dev, &bus->devices, bus_list) {
	if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE \|\|
	dev->hdr_type == PCI_HEADER_TYPE_CARDBUS) {
	struct device_node *child = pci_device_to_OF_node(dev);
	if (child)
	of_scan_pci_bridge(child, dev);
	}
	}
	}

	/**
	* of_scan_bus - given a PCI bus node, setup bus and scan for child devices
	* @node: device tree node for the PCI bus
	* @bus: pci_bus structure for the PCI bus
	*/
	void __devinit of_scan_bus(struct device_node *node,
	struct pci_bus *bus)
	{
	__of_scan_bus(node, bus, 0);
	}
	EXPORT_SYMBOL_GPL(of_scan_bus);

	/**
	* of_rescan_bus - given a PCI bus node, scan for child devices
	* @node: device tree node for the PCI bus
	* @bus: pci_bus structure for the PCI bus
	*
	* Same as of_scan_bus, but for a pci_bus structure that has already been
	* setup.
	*/
	void __devinit of_rescan_bus(struct device_node *node,
	struct pci_bus *bus)
	{
	__of_scan_bus(node, bus, 1);
	}
	EXPORT_SYMBOL_GPL(of_rescan_bus);