Subject: [RFC PATCH] PCI: allocate bus range instead of use max blindly

every bus will have extra busn_res, and linked them toghter to iobusn_resource.

later when need to find usabled bus number range, try allocate from the resource tree.

only test on x86 64 bit.

need to do:
	1. add /proc/iobusn ?
	2. expand bus range, when can not find enough range in parent range.
	3. use list instead to track transparent bus?

Signed-off-by: Yinghai Lu <yinghai@kernel.org>

diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
index b9676ae..15cd4b7 100644
--- a/arch/x86/include/asm/topology.h
+++ b/arch/x86/include/asm/topology.h
@@ -172,7 +172,7 @@ static inline void arch_fix_phys_package_id(int num, u32 slot)
 }
 
 struct pci_bus;
-void x86_pci_root_bus_resources(int bus, struct list_head *resources);
+void x86_pci_root_bus_resources(int bus, int *bus_max, struct list_head *resources);
 
 #ifdef CONFIG_SMP
 #define mc_capable()	((boot_cpu_data.x86_max_cores > 1) && \
diff --git a/arch/x86/pci/acpi.c b/arch/x86/pci/acpi.c
index a312e76..b48f0d9 100644
--- a/arch/x86/pci/acpi.c
+++ b/arch/x86/pci/acpi.c
@@ -348,6 +348,7 @@ struct pci_bus * __devinit pci_acpi_scan_root(struct acpi_pci_root *root)
 	struct acpi_device *device = root->device;
 	int domain = root->segment;
 	int busnum = root->secondary.start;
+	int bus_max = root->secondary.end;
 	LIST_HEAD(resources);
 	struct pci_bus *bus;
 	struct pci_sysdata *sd;
@@ -405,12 +406,20 @@ struct pci_bus * __devinit pci_acpi_scan_root(struct acpi_pci_root *root)
 	} else {
 		get_current_resources(device, busnum, domain, &resources);
 		if (list_empty(&resources))
-			x86_pci_root_bus_resources(busnum, &resources);
+			x86_pci_root_bus_resources(busnum, &bus_max, &resources);
 		bus = pci_create_root_bus(NULL, busnum, &pci_root_ops, sd,
 					  &resources);
-		if (bus)
+		if (bus) {
+			/* init busn_res */
+			bus->busn_res.start = (domain << 8) | busnum;
+			bus->busn_res.end = (domain << 8) | bus_max;
+			bus->busn_res.flags = IORESOURCE_BUS;
+
+			insert_resource(&iobusn_resource, &bus->busn_res);
+			dev_printk(KERN_DEBUG, &bus->dev, "busn_res: %06llx-%06llx inserted\n", (unsigned long long)bus->busn_res.start, (unsigned long long)bus->busn_res.end);
+
 			bus->subordinate = pci_scan_child_bus(bus);
-		else
+		} else
 			pci_free_resource_list(&resources);
 	}
 
diff --git a/arch/x86/pci/bus_numa.c b/arch/x86/pci/bus_numa.c
index fd3f655..3256fb9 100644
--- a/arch/x86/pci/bus_numa.c
+++ b/arch/x86/pci/bus_numa.c
@@ -7,7 +7,7 @@
 int pci_root_num;
 struct pci_root_info pci_root_info[PCI_ROOT_NR];
 
-void x86_pci_root_bus_resources(int bus, struct list_head *resources)
+void x86_pci_root_bus_resources(int bus, int *bus_max, struct list_head *resources)
 {
 	int i;
 	int j;
@@ -28,6 +28,7 @@ void x86_pci_root_bus_resources(int bus, struct list_head *resources)
 	       bus);
 
 	info = &pci_root_info[i];
+	*bus_max = info->bus_max;
 	for (j = 0; j < info->res_num; j++) {
 		struct resource *res;
 		struct resource *root;
@@ -51,6 +52,10 @@ default_resources:
 	printk(KERN_DEBUG "PCI: root bus %02x: using default resources\n", bus);
 	pci_add_resource(resources, &ioport_resource);
 	pci_add_resource(resources, &iomem_resource);
+	if (!bus)
+		*bus_max = 0xff;
+	else if (!*bus_max)
+		*bus_max = bus;
 }
 
 void __devinit update_res(struct pci_root_info *info, resource_size_t start,
diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
index 323481e..e673355 100644
--- a/arch/x86/pci/common.c
+++ b/arch/x86/pci/common.c
@@ -433,6 +433,7 @@ struct pci_bus * __devinit pcibios_scan_root(int busnum)
 	LIST_HEAD(resources);
 	struct pci_bus *bus = NULL;
 	struct pci_sysdata *sd;
+	int bus_max;
 
 	while ((bus = pci_find_next_bus(bus)) != NULL) {
 		if (bus->number == busnum) {
@@ -454,8 +455,8 @@ struct pci_bus * __devinit pcibios_scan_root(int busnum)
 	sd->node = get_mp_bus_to_node(busnum);
 
 	printk(KERN_DEBUG "PCI: Probing PCI hardware (bus %02x)\n", busnum);
-	x86_pci_root_bus_resources(busnum, &resources);
-	bus = pci_scan_root_bus(NULL, busnum, &pci_root_ops, sd, &resources);
+	x86_pci_root_bus_resources(busnum, &bus_max, &resources);
+	bus = pci_scan_root_bus(NULL, busnum, bus_max, &pci_root_ops, sd, &resources);
 	if (!bus) {
 		pci_free_resource_list(&resources);
 		kfree(sd);
@@ -643,6 +644,7 @@ struct pci_bus * __devinit pci_scan_bus_on_node(int busno, struct pci_ops *ops,
 	LIST_HEAD(resources);
 	struct pci_bus *bus = NULL;
 	struct pci_sysdata *sd;
+	int bus_max;
 
 	/*
 	 * Allocate per-root-bus (not per bus) arch-specific data.
@@ -655,8 +657,8 @@ struct pci_bus * __devinit pci_scan_bus_on_node(int busno, struct pci_ops *ops,
 		return NULL;
 	}
 	sd->node = node;
-	x86_pci_root_bus_resources(busno, &resources);
-	bus = pci_scan_root_bus(NULL, busno, ops, sd, &resources);
+	x86_pci_root_bus_resources(busno, &bus_max, &resources);
+	bus = pci_scan_root_bus(NULL, busno, bus_max, ops, sd, &resources);
 	if (!bus) {
 		pci_free_resource_list(&resources);
 		kfree(sd);
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 05c5f76..dc5413d 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -693,6 +693,12 @@ int __devinit pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max,
 			child->primary = primary;
 			child->subordinate = subordinate;
 			child->bridge_ctl = bctl;
+
+			child->busn_res.start = (pci_domain_nr(bus) << 8) | secondary;
+			child->busn_res.end = (pci_domain_nr(bus) << 8) | subordinate;
+			child->busn_res.flags = IORESOURCE_BUS | IORESOURCE_BUSY;
+			dev_printk(KERN_DEBUG, &child->dev, "busn_res: %06llx-%06llx inserted\n", (unsigned long long)child->busn_res.start, (unsigned long long)child->busn_res.end);
+			insert_resource(&bus->busn_res, &child->busn_res);
 		}
 
 		cmax = pci_scan_child_bus(child);
@@ -705,6 +711,11 @@ int __devinit pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max,
 		 * We need to assign a number to this bus which we always
 		 * do in the second pass.
 		 */
+		resource_size_t n_size;
+		struct resource busn_res;
+		int ret = -ENOMEM;
+		int old_max = max;
+
 		if (!pass) {
 			if (pcibios_assign_all_busses() || broken)
 				/* Temporarily disable forwarding of the
@@ -721,20 +732,40 @@ int __devinit pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max,
 		/* Clear errors */
 		pci_write_config_word(dev, PCI_STATUS, 0xffff);
 
-		/* Prevent assigning a bus number that already exists.
-		 * This can happen when a bridge is hot-plugged, so in
-		 * this case we only re-scan this bus. */
-		child = pci_find_bus(pci_domain_nr(bus), max+1);
-		if (!child) {
-			child = pci_add_new_bus(bus, dev, ++max);
-			if (!child)
-				goto out;
+		/* find bigest range in bus->busn_res that we can use */
+		n_size = resource_size(&bus->busn_res) - 1;
+		memset(&busn_res, 0, sizeof(struct resource));
+		dev_printk(KERN_DEBUG, &dev->dev, "try to find busn in busn_res: %06llx-%06llx \n", (unsigned long long)bus->busn_res.start, (unsigned long long)bus->busn_res.end);
+		while (n_size > 0) {
+			ret = allocate_resource(&bus->busn_res, &busn_res, n_size, bus->busn_res.start + 1, bus->busn_res.end, 1, NULL, NULL);
+			if (ret == 0)
+				break;
+			n_size--;
 		}
+
+		if (ret != 0)
+			goto out;
+
+		child = pci_add_new_bus(bus, dev, busn_res.start & 0xff);
+		if (!child)
+			goto out;
+
+		child->subordinate = busn_res.end & 0xff;
+
+		release_resource(&busn_res);
+		child->busn_res.start = busn_res.start;
+		child->busn_res.end = busn_res.end;
+		child->busn_res.flags = IORESOURCE_BUS | IORESOURCE_BUSY;
+		dev_printk(KERN_DEBUG, &child->dev, "busn_res: %06llx-%06llx inserted\n", child->busn_res.start, child->busn_res.end);
+		insert_resource(&bus->busn_res, &child->busn_res);
+
 		buses = (buses & 0xff000000)
 		      | ((unsigned int)(child->primary)     <<  0)
 		      | ((unsigned int)(child->secondary)   <<  8)
 		      | ((unsigned int)(child->subordinate) << 16);
 
+		max = child->secondary;
+
 		/*
 		 * yenta.c forces a secondary latency timer of 176.
 		 * Copy that behaviour here.
@@ -802,6 +833,12 @@ int __devinit pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max,
 		 */
 		child->subordinate = max;
 		pci_write_config_byte(dev, PCI_SUBORDINATE_BUS, max);
+		child->busn_res.end &= ~0xff;
+		child->busn_res.end |= max;
+		dev_printk(KERN_DEBUG, &child->dev, "busn_res: %06llx-%06llx adjusted\n", (unsigned long long)child->busn_res.start, (unsigned long long)child->busn_res.end);
+
+		if (old_max > max)
+			max = old_max;
 	}
 
 	sprintf(child->name,
@@ -1641,7 +1678,7 @@ err_out:
 	return NULL;
 }
 
-struct pci_bus * __devinit pci_scan_root_bus(struct device *parent, int bus,
+struct pci_bus * __devinit pci_scan_root_bus(struct device *parent, int bus, int bus_max,
 		struct pci_ops *ops, void *sysdata, struct list_head *resources)
 {
 	struct pci_bus *b;
@@ -1650,6 +1687,13 @@ struct pci_bus * __devinit pci_scan_root_bus(struct device *parent, int bus,
 	if (!b)
 		return NULL;
 
+	/* init busn_res */
+	b->busn_res.start = (pci_domain_nr(b) << 8) | bus;
+	b->busn_res.end = (pci_domain_nr(b) << 8) | bus_max;
+	b->busn_res.flags = IORESOURCE_BUS;
+
+	insert_resource(&iobusn_resource, &b->busn_res);
+
 	b->subordinate = pci_scan_child_bus(b);
 	pci_bus_add_devices(b);
 	return b;
diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
index ef3c18a..4ca0f74 100644
--- a/drivers/pci/remove.c
+++ b/drivers/pci/remove.c
@@ -68,6 +68,7 @@ void pci_remove_bus(struct pci_bus *pci_bus)
 
 	down_write(&pci_bus_sem);
 	list_del(&pci_bus->node);
+	release_resource(&pci_bus->busn_res);
 	up_write(&pci_bus_sem);
 	if (!pci_bus->is_added)
 		return;
diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index e885ba2..6fe9e19 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -136,6 +136,7 @@ struct resource {
 /* PC/ISA/whatever - the normal PC address spaces: IO and memory */
 extern struct resource ioport_resource;
 extern struct resource iomem_resource;
+extern struct resource iobusn_resource;
 
 extern struct resource *request_resource_conflict(struct resource *root, struct resource *new);
 extern int request_resource(struct resource *root, struct resource *new);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index d266085..edaac82 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -420,6 +420,7 @@ struct pci_bus {
 	struct list_head slots;		/* list of slots on this bus */
 	struct resource *resource[PCI_BRIDGE_RESOURCE_NUM];
 	struct list_head resources;	/* address space routed to this bus */
+	struct resource busn_res;	/* track registered bus num range */
 
 	struct pci_ops	*ops;		/* configuration access functions */
 	void		*sysdata;	/* hook for sys-specific extension */
@@ -666,7 +667,8 @@ struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
 				    struct pci_ops *ops, void *sysdata,
 				    struct list_head *resources);
 struct pci_bus * __devinit pci_scan_root_bus(struct device *parent, int bus,
-					     struct pci_ops *ops, void *sysdata,
+					     int bus_max, struct pci_ops *ops,
+					     void *sysdata,
 					     struct list_head *resources);
 struct pci_bus *pci_add_new_bus(struct pci_bus *parent, struct pci_dev *dev,
 				int busnr);
diff --git a/kernel/resource.c b/kernel/resource.c
index 7640b3a..53b42f0 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -38,6 +38,14 @@ struct resource iomem_resource = {
 };
 EXPORT_SYMBOL(iomem_resource);
 
+struct resource iobusn_resource = {
+	.name	= "PCI busn",
+	.start	= 0,
+	.end	= 0xffffff,
+	.flags	= IORESOURCE_BUS,
+};
+EXPORT_SYMBOL(iobusn_resource);
+
 /* constraints to be met while allocating resources */
 struct resource_constraint {
 	resource_size_t min, max, align;