diff mbox

[v6,4/7] PCI/ACPI: Consolidate common PCI host bridge code into ACPI core

Message ID 1442218057-4355-5-git-send-email-jiang.liu@linux.intel.com (mailing list archive)
State Changes Requested, archived
Headers show

Commit Message

Jiang Liu Sept. 14, 2015, 8:07 a.m. UTC
Introduce common interface acpi_pci_root_create() and related data
structures to create PCI root bus for ACPI PCI host bridges. It will
be used to kill duplicated arch specific code for IA64 and x86. It may
also help ARM64 in future.

Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Tested-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
---
 drivers/acpi/pci_root.c  |  204 ++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/pci-acpi.h |   23 ++++++
 2 files changed, 227 insertions(+)

Comments

Bjorn Helgaas Oct. 6, 2015, 5:47 p.m. UTC | #1
Hi Jiang,

Strictly speaking, this patch by itself doesn't actually "consolidate"
anything because it only adds acpi_pci_root_create() (which isn't called by
anything yet), but doesn't remove the original x86 copy.

On Mon, Sep 14, 2015 at 04:07:33PM +0800, Jiang Liu wrote:
> Introduce common interface acpi_pci_root_create() and related data
> structures to create PCI root bus for ACPI PCI host bridges. It will
> be used to kill duplicated arch specific code for IA64 and x86. It may
> also help ARM64 in future.
> 
> Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Tested-by: Tony Luck <tony.luck@intel.com>
> Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>

Acked-by: Bjorn Helgaas <bhelgaas@google.com>

Some minor structuring comments below, but my ack is valid even if you
don't address them.

> ---
>  drivers/acpi/pci_root.c  |  204 ++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/pci-acpi.h |   23 ++++++
>  2 files changed, 227 insertions(+)
> 
> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> index 393706a5261b..48d27bd35b58 100644
> --- a/drivers/acpi/pci_root.c
> +++ b/drivers/acpi/pci_root.c
> @@ -652,6 +652,210 @@ static void acpi_pci_root_remove(struct acpi_device *device)
>  	kfree(root);
>  }
>  
> +/*
> + * Following code to support acpi_pci_root_create() is copied from
> + * arch/x86/pci/acpi.c and modified so it could be reused by x86, IA64
> + * and ARM64.
> + */
> +static void acpi_pci_root_validate_resources(struct device *dev,
> +					     struct list_head *resources,
> +					     unsigned long type)
> +{
> +	LIST_HEAD(list);
> +	struct resource *res1, *res2, *root = NULL;
> +	struct resource_entry *tmp, *entry, *entry2;
> +
> +	BUG_ON((type & (IORESOURCE_MEM | IORESOURCE_IO)) == 0);
> +	root = (type & IORESOURCE_MEM) ? &iomem_resource : &ioport_resource;
> +
> +	list_splice_init(resources, &list);
> +	resource_list_for_each_entry_safe(entry, tmp, &list) {
> +		bool free = false;
> +		resource_size_t end;
> +
> +		res1 = entry->res;
> +		if (!(res1->flags & type))
> +			goto next;
> +
> +		/* Exclude non-addressable range or non-addressable portion */
> +		end = min(res1->end, root->end);
> +		if (end <= res1->start) {
> +			dev_info(dev, "host bridge window %pR (ignored, not CPU addressable)\n",
> +				 res1);
> +			free = true;
> +			goto next;
> +		} else if (res1->end != end) {
> +			dev_info(dev, "host bridge window %pR ([%#llx-%#llx] ignored, not CPU addressable)\n",
> +				 res1, (unsigned long long)end + 1,
> +				 (unsigned long long)res1->end);
> +			res1->end = end;
> +		}
> +
> +		resource_list_for_each_entry(entry2, resources) {
> +			res2 = entry2->res;
> +			if (!(res2->flags & type))
> +				continue;
> +
> +			/*
> +			 * I don't like throwing away windows because then
> +			 * our resources no longer match the ACPI _CRS, but
> +			 * the kernel resource tree doesn't allow overlaps.
> +			 */
> +			if (resource_overlaps(res1, res2)) {
> +				res2->start = min(res1->start, res2->start);
> +				res2->end = max(res1->end, res2->end);
> +				dev_info(dev, "host bridge window expanded to %pR; %pR ignored\n",
> +					 res2, res1);
> +				free = true;
> +				goto next;
> +			}
> +		}
> +
> +next:
> +		resource_list_del(entry);
> +		if (free)
> +			resource_list_free_entry(entry);
> +		else
> +			resource_list_add_tail(entry, resources);
> +	}
> +}
> +
> +static int acpi_pci_probe_root_resources(struct acpi_pci_root_info *info)
> +{
> +	int ret;
> +	struct list_head *list = &info->resources;
> +	struct acpi_device *device = info->bridge;
> +	struct resource_entry *entry, *tmp;
> +	unsigned long flags;
> +
> +	flags = IORESOURCE_IO | IORESOURCE_MEM | IORESOURCE_MEM_8AND16BIT;
> +	ret = acpi_dev_get_resources(device, list,
> +				     acpi_dev_filter_resource_type_cb,
> +				     (void *)flags);
> +	if (ret < 0)
> +		dev_warn(&device->dev,
> +			 "failed to parse _CRS method, error code %d\n", ret);
> +	else if (ret == 0)
> +		dev_dbg(&device->dev,
> +			"no IO and memory resources present in _CRS\n");
> +	else {
> +		resource_list_for_each_entry_safe(entry, tmp, list) {
> +			if (entry->res->flags & IORESOURCE_DISABLED)
> +				resource_list_destroy_entry(entry);
> +			else
> +				entry->res->name = info->name;
> +		}
> +		acpi_pci_root_validate_resources(&device->dev, list,
> +						 IORESOURCE_MEM);
> +		acpi_pci_root_validate_resources(&device->dev, list,
> +						 IORESOURCE_IO);
> +	}
> +
> +	return ret;
> +}
> +
> +static void pci_acpi_root_add_resources(struct acpi_pci_root_info *info)
> +{
> +	struct resource_entry *entry, *tmp;
> +	struct resource *res, *conflict, *root = NULL;
> +
> +	resource_list_for_each_entry_safe(entry, tmp, &info->resources) {
> +		res = entry->res;
> +		if (res->flags & IORESOURCE_MEM)
> +			root = &iomem_resource;
> +		else if (res->flags & IORESOURCE_IO)
> +			root = &ioport_resource;
> +		else
> +			continue;
> +
> +		conflict = insert_resource_conflict(root, res);
> +		if (conflict) {
> +			dev_info(&info->bridge->dev,
> +				 "ignoring host bridge window %pR (conflicts with %s %pR)\n",
> +				 res, conflict->name, conflict);
> +			resource_list_destroy_entry(entry);
> +		}
> +	}
> +}
> +
> +static void __acpi_pci_root_release_info(struct acpi_pci_root_info *info)
> +{
> +	struct resource *res;
> +	struct resource_entry *entry, *tmp;
> +
> +	if (!info)
> +		return;
> +
> +	resource_list_for_each_entry_safe(entry, tmp, &info->resources) {
> +		res = entry->res;
> +		if (res->parent &&
> +		    (res->flags & (IORESOURCE_MEM | IORESOURCE_IO)))
> +			release_resource(res);
> +		resource_list_destroy_entry(entry);
> +	}
> +
> +	info->ops->release_info(info);
> +}
> +
> +static void acpi_pci_root_release_info(struct pci_host_bridge *bridge)
> +{
> +	struct resource *res;
> +	struct resource_entry *entry;
> +
> +	resource_list_for_each_entry(entry, &bridge->windows) {
> +		res = entry->res;
> +		if (res->parent &&
> +		    (res->flags & (IORESOURCE_MEM | IORESOURCE_IO)))
> +			release_resource(res);
> +	}
> +	__acpi_pci_root_release_info(bridge->release_data);
> +}
> +
> +struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
> +				     struct acpi_pci_root_ops *ops,
> +				     struct acpi_pci_root_info *info,
> +				     void *sysdata)
> +{
> +	int ret, busnum = root->secondary.start;
> +	struct acpi_device *device = root->device;
> +	int node = acpi_get_node(device->handle);
> +	struct pci_bus *bus;
> +
> +	info->root = root;
> +	info->bridge = device;
> +	info->ops = ops;
> +	INIT_LIST_HEAD(&info->resources);
> +	snprintf(info->name, sizeof(info->name), "PCI Bus %04x:%02x",
> +		 root->segment, busnum);
> +
> +	if (ops->init_info && ops->init_info(info))
> +		goto out_release_info;
> +	ret = acpi_pci_probe_root_resources(info);
> +	if (ops->prepare_resources)
> +		ret = ops->prepare_resources(info, ret);
> +	if (ret < 0)
> +		goto out_release_info;
> +	else if (ret > 0)
> +		pci_acpi_root_add_resources(info);

This is unnecessarily complicated: you set "ret", then overwrite it if
ops->prepare_resources.  By the time you test "ret", it's messy to
figure out what it means.

Both ops->prepare_resources() and pci_acpi_root_add_resources()
should be able to deal with empty resource lists, so can you do the
following instead?

    ret = acpi_pci_probe_root_resources(info);
    if (ret < 0)
        goto out_release_info;
    if (ops->prepare_resources) {
        ret = ops->prepare_resources(info, ret);
        if (ret < 0)
            goto out_release_info;
    }
    pci_acpi_root_add_resources(info);

> +	pci_add_resource(&info->resources, &root->secondary);
> +
> +	bus = pci_create_root_bus(NULL, busnum, ops->pci_ops,
> +				  sysdata, &info->resources);
> +	if (bus) {

    if (!bus)
        goto out_release_info;

Then it looks like the other error paths above, and you can un-indent
the following code, which is the normal path:

> +		pci_scan_child_bus(bus);
> +		pci_set_host_bridge_release(to_pci_host_bridge(bus->bridge),
> +					    acpi_pci_root_release_info, info);
> +		if (node != NUMA_NO_NODE)
> +			dev_printk(KERN_DEBUG, &bus->dev, "on NUMA node %d\n",
> +				   node);
> +		return bus;
> +	}
> +
> +out_release_info:
> +	__acpi_pci_root_release_info(info);
> +	return NULL;
> +}
> +
>  void __init acpi_pci_root_init(void)
>  {
>  	acpi_hest_init();
> diff --git a/include/linux/pci-acpi.h b/include/linux/pci-acpi.h
> index a965efa52152..583af37c6030 100644
> --- a/include/linux/pci-acpi.h
> +++ b/include/linux/pci-acpi.h
> @@ -52,6 +52,29 @@ static inline acpi_handle acpi_pci_get_bridge_handle(struct pci_bus *pbus)
>  	return ACPI_HANDLE(dev);
>  }
>  
> +struct acpi_pci_root;
> +struct acpi_pci_root_ops;
> +
> +struct acpi_pci_root_info {
> +	struct acpi_pci_root		*root;
> +	struct acpi_device		*bridge;
> +	struct acpi_pci_root_ops	*ops;
> +	struct list_head		resources;
> +	char				name[16];
> +};
> +
> +struct acpi_pci_root_ops {
> +	struct pci_ops *pci_ops;
> +	int (*init_info)(struct acpi_pci_root_info *info);
> +	void (*release_info)(struct acpi_pci_root_info *info);
> +	int (*prepare_resources)(struct acpi_pci_root_info *info, int status);
> +};
> +
> +extern struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
> +					    struct acpi_pci_root_ops *ops,
> +					    struct acpi_pci_root_info *info,
> +					    void *sd);
> +
>  void acpi_pci_add_bus(struct pci_bus *bus);
>  void acpi_pci_remove_bus(struct pci_bus *bus);
>  
> -- 
> 1.7.10.4
> 
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Jiang Liu Oct. 8, 2015, 5:32 a.m. UTC | #2
On 2015/10/7 1:47, Bjorn Helgaas wrote:
> Hi Jiang,
> 
> Strictly speaking, this patch by itself doesn't actually "consolidate"
> anything because it only adds acpi_pci_root_create() (which isn't called by
> anything yet), but doesn't remove the original x86 copy.
> 
<snit>
>> +struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
>> +				     struct acpi_pci_root_ops *ops,
>> +				     struct acpi_pci_root_info *info,
>> +				     void *sysdata)
>> +{
>> +	int ret, busnum = root->secondary.start;
>> +	struct acpi_device *device = root->device;
>> +	int node = acpi_get_node(device->handle);
>> +	struct pci_bus *bus;
>> +
>> +	info->root = root;
>> +	info->bridge = device;
>> +	info->ops = ops;
>> +	INIT_LIST_HEAD(&info->resources);
>> +	snprintf(info->name, sizeof(info->name), "PCI Bus %04x:%02x",
>> +		 root->segment, busnum);
>> +
>> +	if (ops->init_info && ops->init_info(info))
>> +		goto out_release_info;
>> +	ret = acpi_pci_probe_root_resources(info);
>> +	if (ops->prepare_resources)
>> +		ret = ops->prepare_resources(info, ret);
>> +	if (ret < 0)
>> +		goto out_release_info;
>> +	else if (ret > 0)
>> +		pci_acpi_root_add_resources(info);
> 
> This is unnecessarily complicated: you set "ret", then overwrite it if
> ops->prepare_resources.  By the time you test "ret", it's messy to
> figure out what it means.
> 
> Both ops->prepare_resources() and pci_acpi_root_add_resources()
> should be able to deal with empty resource lists, so can you do the
> following instead?
> 
>     ret = acpi_pci_probe_root_resources(info);
>     if (ret < 0)
>         goto out_release_info;
Hi Bjorn,
	Thanks for review:)
	The original code is used to handle a special case for x86,
where acpi_pci_probe_root_resources() fails but ops->prepare_resources()
succeeds. For x86, PCI host bridge resources may probed by means
other than ACPI when pci_use_crs is true (AMD and Broadcom hostbridges).
So we can't return failure when acpi_pci_probe_root_resources() fails.
+	ret = acpi_pci_probe_root_resources(info);
+	if (ops->prepare_resources)
+		ret = ops->prepare_resources(info, ret);
+	if (ret < 0)
+		goto out_release_info;

>     if (ops->prepare_resources) {
>         ret = ops->prepare_resources(info, ret);
>         if (ret < 0)
>             goto out_release_info;
>     }
>     pci_acpi_root_add_resources(info);
I will remove the redundant check of (ret > 0) in:
+	else if (ret > 0)
+		pci_acpi_root_add_resources(info);

> 
>> +	pci_add_resource(&info->resources, &root->secondary);
>> +
>> +	bus = pci_create_root_bus(NULL, busnum, ops->pci_ops,
>> +				  sysdata, &info->resources);
>> +	if (bus) {
> 
>     if (!bus)
>         goto out_release_info;
> 
> Then it looks like the other error paths above, and you can un-indent
> the following code, which is the normal path:
Will do this.
Thanks!
Gerry
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Bjorn Helgaas Oct. 8, 2015, 1:20 p.m. UTC | #3
On Thu, Oct 08, 2015 at 01:32:04PM +0800, Jiang Liu wrote:
> On 2015/10/7 1:47, Bjorn Helgaas wrote:
> >> +struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
> >> +				     struct acpi_pci_root_ops *ops,
> >> +				     struct acpi_pci_root_info *info,
> >> +				     void *sysdata)
> >> +{
> >> +	int ret, busnum = root->secondary.start;
> >> +	struct acpi_device *device = root->device;
> >> +	int node = acpi_get_node(device->handle);
> >> +	struct pci_bus *bus;
> >> +
> >> +	info->root = root;
> >> +	info->bridge = device;
> >> +	info->ops = ops;
> >> +	INIT_LIST_HEAD(&info->resources);
> >> +	snprintf(info->name, sizeof(info->name), "PCI Bus %04x:%02x",
> >> +		 root->segment, busnum);
> >> +
> >> +	if (ops->init_info && ops->init_info(info))
> >> +		goto out_release_info;
> >> +	ret = acpi_pci_probe_root_resources(info);
> >> +	if (ops->prepare_resources)
> >> +		ret = ops->prepare_resources(info, ret);
> >> +	if (ret < 0)
> >> +		goto out_release_info;
> >> +	else if (ret > 0)
> >> +		pci_acpi_root_add_resources(info);
> > 
> > This is unnecessarily complicated: you set "ret", then overwrite it if
> > ops->prepare_resources.  By the time you test "ret", it's messy to
> > figure out what it means.
> > 
> > Both ops->prepare_resources() and pci_acpi_root_add_resources()
> > should be able to deal with empty resource lists, so can you do the
> > following instead?
> > 
> >     ret = acpi_pci_probe_root_resources(info);
> >     if (ret < 0)
> >         goto out_release_info;
>
> 	The original code is used to handle a special case for x86,
> where acpi_pci_probe_root_resources() fails but ops->prepare_resources()
> succeeds. For x86, PCI host bridge resources may probed by means
> other than ACPI when pci_use_crs is true (AMD and Broadcom hostbridges).
> So we can't return failure when acpi_pci_probe_root_resources() fails.

That's even worse than I thought.  I take back my ack; I think this
really needs to be restructured so it does the right thing *and* reads
clearly.  Having convoluted generic code to deal with an arch-specific
special case is a recipe for breakage in the future.

Maybe you can move the non-ACPI resource probing from
prepare_resources() into acpi_pci_probe_root_resources() (you could
rename it to something more generic if that helps).

> +	ret = acpi_pci_probe_root_resources(info);
> +	if (ops->prepare_resources)
> +		ret = ops->prepare_resources(info, ret);
> +	if (ret < 0)
> +		goto out_release_info;
> 
> >     if (ops->prepare_resources) {
> >         ret = ops->prepare_resources(info, ret);
> >         if (ret < 0)
> >             goto out_release_info;
> >     }
> >     pci_acpi_root_add_resources(info);
> I will remove the redundant check of (ret > 0) in:
> +	else if (ret > 0)
> +		pci_acpi_root_add_resources(info);
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Jiang Liu Oct. 9, 2015, 8:19 a.m. UTC | #4
On 2015/10/8 21:20, Bjorn Helgaas wrote:
> On Thu, Oct 08, 2015 at 01:32:04PM +0800, Jiang Liu wrote:
>> On 2015/10/7 1:47, Bjorn Helgaas wrote:
>>>> +struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
>>>> +				     struct acpi_pci_root_ops *ops,
>>>> +				     struct acpi_pci_root_info *info,
>>>> +				     void *sysdata)
>>>> +{
>>>> +	int ret, busnum = root->secondary.start;
>>>> +	struct acpi_device *device = root->device;
>>>> +	int node = acpi_get_node(device->handle);
>>>> +	struct pci_bus *bus;
>>>> +
>>>> +	info->root = root;
>>>> +	info->bridge = device;
>>>> +	info->ops = ops;
>>>> +	INIT_LIST_HEAD(&info->resources);
>>>> +	snprintf(info->name, sizeof(info->name), "PCI Bus %04x:%02x",
>>>> +		 root->segment, busnum);
>>>> +
>>>> +	if (ops->init_info && ops->init_info(info))
>>>> +		goto out_release_info;
>>>> +	ret = acpi_pci_probe_root_resources(info);
>>>> +	if (ops->prepare_resources)
>>>> +		ret = ops->prepare_resources(info, ret);
>>>> +	if (ret < 0)
>>>> +		goto out_release_info;
>>>> +	else if (ret > 0)
>>>> +		pci_acpi_root_add_resources(info);
>>>
>>> This is unnecessarily complicated: you set "ret", then overwrite it if
>>> ops->prepare_resources.  By the time you test "ret", it's messy to
>>> figure out what it means.
>>>
>>> Both ops->prepare_resources() and pci_acpi_root_add_resources()
>>> should be able to deal with empty resource lists, so can you do the
>>> following instead?
>>>
>>>     ret = acpi_pci_probe_root_resources(info);
>>>     if (ret < 0)
>>>         goto out_release_info;
>>
>> 	The original code is used to handle a special case for x86,
>> where acpi_pci_probe_root_resources() fails but ops->prepare_resources()
>> succeeds. For x86, PCI host bridge resources may probed by means
>> other than ACPI when pci_use_crs is true (AMD and Broadcom hostbridges).
>> So we can't return failure when acpi_pci_probe_root_resources() fails.
> 
> That's even worse than I thought.  I take back my ack; I think this
> really needs to be restructured so it does the right thing *and* reads
> clearly.  Having convoluted generic code to deal with an arch-specific
> special case is a recipe for breakage in the future.
> 
> Maybe you can move the non-ACPI resource probing from
> prepare_resources() into acpi_pci_probe_root_resources() (you could
> rename it to something more generic if that helps).
Hi Bjorn,
	How about this solution?
1) export acpi_pci_probe_root_resources() as a helper to arch code
2) change ACPI core code as below
        if (ops->init_info && ops->init_info(info))
                goto out_release_info;
        if (ops->prepare_resources)
                ret = ops->prepare_resources(info);
        else
                ret = acpi_pci_probe_root_resources(info);
        if (ret < 0)
                goto out_release_info;

        pci_acpi_root_add_resources(info);
        pci_add_resource(&info->resources, &root->secondary);
        bus = pci_create_root_bus(NULL, busnum, ops->pci_ops,
                                  sysdata, &info->resources);
        if (!bus)
                goto out_release_info;

By this way, if arch has special requirement, it could implement
prepare_resources callback and make use of
acpi_pci_probe_root_resources() if needed.
Thanks!
Gerry
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diff mbox

Patch

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 393706a5261b..48d27bd35b58 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -652,6 +652,210 @@  static void acpi_pci_root_remove(struct acpi_device *device)
 	kfree(root);
 }
 
+/*
+ * Following code to support acpi_pci_root_create() is copied from
+ * arch/x86/pci/acpi.c and modified so it could be reused by x86, IA64
+ * and ARM64.
+ */
+static void acpi_pci_root_validate_resources(struct device *dev,
+					     struct list_head *resources,
+					     unsigned long type)
+{
+	LIST_HEAD(list);
+	struct resource *res1, *res2, *root = NULL;
+	struct resource_entry *tmp, *entry, *entry2;
+
+	BUG_ON((type & (IORESOURCE_MEM | IORESOURCE_IO)) == 0);
+	root = (type & IORESOURCE_MEM) ? &iomem_resource : &ioport_resource;
+
+	list_splice_init(resources, &list);
+	resource_list_for_each_entry_safe(entry, tmp, &list) {
+		bool free = false;
+		resource_size_t end;
+
+		res1 = entry->res;
+		if (!(res1->flags & type))
+			goto next;
+
+		/* Exclude non-addressable range or non-addressable portion */
+		end = min(res1->end, root->end);
+		if (end <= res1->start) {
+			dev_info(dev, "host bridge window %pR (ignored, not CPU addressable)\n",
+				 res1);
+			free = true;
+			goto next;
+		} else if (res1->end != end) {
+			dev_info(dev, "host bridge window %pR ([%#llx-%#llx] ignored, not CPU addressable)\n",
+				 res1, (unsigned long long)end + 1,
+				 (unsigned long long)res1->end);
+			res1->end = end;
+		}
+
+		resource_list_for_each_entry(entry2, resources) {
+			res2 = entry2->res;
+			if (!(res2->flags & type))
+				continue;
+
+			/*
+			 * I don't like throwing away windows because then
+			 * our resources no longer match the ACPI _CRS, but
+			 * the kernel resource tree doesn't allow overlaps.
+			 */
+			if (resource_overlaps(res1, res2)) {
+				res2->start = min(res1->start, res2->start);
+				res2->end = max(res1->end, res2->end);
+				dev_info(dev, "host bridge window expanded to %pR; %pR ignored\n",
+					 res2, res1);
+				free = true;
+				goto next;
+			}
+		}
+
+next:
+		resource_list_del(entry);
+		if (free)
+			resource_list_free_entry(entry);
+		else
+			resource_list_add_tail(entry, resources);
+	}
+}
+
+static int acpi_pci_probe_root_resources(struct acpi_pci_root_info *info)
+{
+	int ret;
+	struct list_head *list = &info->resources;
+	struct acpi_device *device = info->bridge;
+	struct resource_entry *entry, *tmp;
+	unsigned long flags;
+
+	flags = IORESOURCE_IO | IORESOURCE_MEM | IORESOURCE_MEM_8AND16BIT;
+	ret = acpi_dev_get_resources(device, list,
+				     acpi_dev_filter_resource_type_cb,
+				     (void *)flags);
+	if (ret < 0)
+		dev_warn(&device->dev,
+			 "failed to parse _CRS method, error code %d\n", ret);
+	else if (ret == 0)
+		dev_dbg(&device->dev,
+			"no IO and memory resources present in _CRS\n");
+	else {
+		resource_list_for_each_entry_safe(entry, tmp, list) {
+			if (entry->res->flags & IORESOURCE_DISABLED)
+				resource_list_destroy_entry(entry);
+			else
+				entry->res->name = info->name;
+		}
+		acpi_pci_root_validate_resources(&device->dev, list,
+						 IORESOURCE_MEM);
+		acpi_pci_root_validate_resources(&device->dev, list,
+						 IORESOURCE_IO);
+	}
+
+	return ret;
+}
+
+static void pci_acpi_root_add_resources(struct acpi_pci_root_info *info)
+{
+	struct resource_entry *entry, *tmp;
+	struct resource *res, *conflict, *root = NULL;
+
+	resource_list_for_each_entry_safe(entry, tmp, &info->resources) {
+		res = entry->res;
+		if (res->flags & IORESOURCE_MEM)
+			root = &iomem_resource;
+		else if (res->flags & IORESOURCE_IO)
+			root = &ioport_resource;
+		else
+			continue;
+
+		conflict = insert_resource_conflict(root, res);
+		if (conflict) {
+			dev_info(&info->bridge->dev,
+				 "ignoring host bridge window %pR (conflicts with %s %pR)\n",
+				 res, conflict->name, conflict);
+			resource_list_destroy_entry(entry);
+		}
+	}
+}
+
+static void __acpi_pci_root_release_info(struct acpi_pci_root_info *info)
+{
+	struct resource *res;
+	struct resource_entry *entry, *tmp;
+
+	if (!info)
+		return;
+
+	resource_list_for_each_entry_safe(entry, tmp, &info->resources) {
+		res = entry->res;
+		if (res->parent &&
+		    (res->flags & (IORESOURCE_MEM | IORESOURCE_IO)))
+			release_resource(res);
+		resource_list_destroy_entry(entry);
+	}
+
+	info->ops->release_info(info);
+}
+
+static void acpi_pci_root_release_info(struct pci_host_bridge *bridge)
+{
+	struct resource *res;
+	struct resource_entry *entry;
+
+	resource_list_for_each_entry(entry, &bridge->windows) {
+		res = entry->res;
+		if (res->parent &&
+		    (res->flags & (IORESOURCE_MEM | IORESOURCE_IO)))
+			release_resource(res);
+	}
+	__acpi_pci_root_release_info(bridge->release_data);
+}
+
+struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
+				     struct acpi_pci_root_ops *ops,
+				     struct acpi_pci_root_info *info,
+				     void *sysdata)
+{
+	int ret, busnum = root->secondary.start;
+	struct acpi_device *device = root->device;
+	int node = acpi_get_node(device->handle);
+	struct pci_bus *bus;
+
+	info->root = root;
+	info->bridge = device;
+	info->ops = ops;
+	INIT_LIST_HEAD(&info->resources);
+	snprintf(info->name, sizeof(info->name), "PCI Bus %04x:%02x",
+		 root->segment, busnum);
+
+	if (ops->init_info && ops->init_info(info))
+		goto out_release_info;
+	ret = acpi_pci_probe_root_resources(info);
+	if (ops->prepare_resources)
+		ret = ops->prepare_resources(info, ret);
+	if (ret < 0)
+		goto out_release_info;
+	else if (ret > 0)
+		pci_acpi_root_add_resources(info);
+	pci_add_resource(&info->resources, &root->secondary);
+
+	bus = pci_create_root_bus(NULL, busnum, ops->pci_ops,
+				  sysdata, &info->resources);
+	if (bus) {
+		pci_scan_child_bus(bus);
+		pci_set_host_bridge_release(to_pci_host_bridge(bus->bridge),
+					    acpi_pci_root_release_info, info);
+		if (node != NUMA_NO_NODE)
+			dev_printk(KERN_DEBUG, &bus->dev, "on NUMA node %d\n",
+				   node);
+		return bus;
+	}
+
+out_release_info:
+	__acpi_pci_root_release_info(info);
+	return NULL;
+}
+
 void __init acpi_pci_root_init(void)
 {
 	acpi_hest_init();
diff --git a/include/linux/pci-acpi.h b/include/linux/pci-acpi.h
index a965efa52152..583af37c6030 100644
--- a/include/linux/pci-acpi.h
+++ b/include/linux/pci-acpi.h
@@ -52,6 +52,29 @@  static inline acpi_handle acpi_pci_get_bridge_handle(struct pci_bus *pbus)
 	return ACPI_HANDLE(dev);
 }
 
+struct acpi_pci_root;
+struct acpi_pci_root_ops;
+
+struct acpi_pci_root_info {
+	struct acpi_pci_root		*root;
+	struct acpi_device		*bridge;
+	struct acpi_pci_root_ops	*ops;
+	struct list_head		resources;
+	char				name[16];
+};
+
+struct acpi_pci_root_ops {
+	struct pci_ops *pci_ops;
+	int (*init_info)(struct acpi_pci_root_info *info);
+	void (*release_info)(struct acpi_pci_root_info *info);
+	int (*prepare_resources)(struct acpi_pci_root_info *info, int status);
+};
+
+extern struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
+					    struct acpi_pci_root_ops *ops,
+					    struct acpi_pci_root_info *info,
+					    void *sd);
+
 void acpi_pci_add_bus(struct pci_bus *bus);
 void acpi_pci_remove_bus(struct pci_bus *bus);