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SubjectRe: [Alternative][PATCH] ACPI / PCI: Set root bridge ACPI handle in advance
On Tue, Dec 25, 2012 at 3:42 PM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Subject: PCI / ACPI: Set root bridge ACPI handle in advance
>
> The ACPI handles of PCI root bridges need to be known to
> acpi_bind_one(), so that it can create the appropriate
> "firmware_node" and "physical_node" files for them, but currently
> the way it gets to know those handles is not exactly straightforward
> (to put it lightly).
>
> This is how it works, roughly:
>
> 1. acpi_bus_scan() finds the handle of a PCI root bridge,
> creates a struct acpi_device object for it and passes that
> object to acpi_pci_root_add().
>
> 2. acpi_pci_root_add() creates a struct acpi_pci_root object,
> populates its "device" field with its argument's address
> (device->handle is the ACPI handle found in step 1).
>
> 3. The struct acpi_pci_root object created in step 2 is passed
> to pci_acpi_scan_root() and used to get resources that are
> passed to pci_create_root_bus().
>
> 4. pci_create_root_bus() creates a struct pci_host_bridge object
> and passes its "dev" member to device_register().
>
> 5. platform_notify(), which for systems with ACPI is set to
> acpi_platform_notify(), is called.
>
> So far, so good. Now it starts to be "interesting".
>
> 6. acpi_find_bridge_device() is used to find the ACPI handle of
> the given device (which is the PCI root bridge) and executes
> acpi_pci_find_root_bridge(), among other things, for the
> given device object.
>
> 7. acpi_pci_find_root_bridge() uses the name (sic!) of the given
> device object to extract the segment and bus numbers of the PCI
> root bridge and passes them to acpi_get_pci_rootbridge_handle().
>
> 8. acpi_get_pci_rootbridge_handle() browses the list of ACPI PCI
> root bridges and finds the one that matches the given segment
> and bus numbers. Its handle is then used to initialize the
> ACPI handle of the PCI root bridge's device object by
> acpi_bind_one(). However, this is *exactly* the ACPI handle we
> started with in step 1.
>
> Needless to say, this is quite embarassing, but it may be avoided
> thanks to commit f3fd0c8 (ACPI: Allow ACPI handles of devices to be
> initialized in advance), which makes it possible to initialize the
> ACPI handle of a device before passing it to device_register().
>
> Accordingly, add a new __weak routine, pcibios_root_bridge_prepare(),
> defaulting to an empty implementation that can be replaced by the
> interested architecutres (x86 and ia64 at the moment) with functions
> that will set the root bridge's ACPI handle before its dev member is
> passed to device_register(). Make both x86 and ia64 provide such
> implementations of pcibios_root_bridge_prepare() and remove
> acpi_pci_find_root_bridge() and acpi_get_pci_rootbridge_handle() that aren't
> necessary any more.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
>
> Bjorn,
>
> Since you didn't like the implementation used in the previous patch, here's
> an alternative one using a __weak function.
>
> I don't really strongly prefer any of them. The advantage of the present one
> is that it changes fewer files and directly affects fewer architectures. The
> disadvantage of it is the addition of the __weak "callback".
>
> I wonder what the maintainers of the architectures in question (Peter, Tony)
> think.

I like this one much better because it doesn't change any of the PCI
interfaces (pci_create_root_bus()).

I don't see __weak as a disadvantage. We need some way of having
arch-specific hooks, and I don't think __weak is uglier than the other
techniques, e.g., #ifdefs. The original patch uses ACPI_HANDLE_SET()
in generic code and uses #ifdefs to define ACPI_HANDLE_SET() to
nothing on non-ACPI architectures.

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

> ---
> arch/ia64/pci/pci.c | 8 ++++++++
> arch/x86/pci/acpi.c | 9 +++++++++
> drivers/acpi/pci_root.c | 18 ------------------
> drivers/pci/pci-acpi.c | 19 -------------------
> drivers/pci/probe.c | 16 ++++++++++++++++
> include/acpi/acpi_bus.h | 1 -
> include/linux/pci.h | 2 ++
> 7 files changed, 35 insertions(+), 38 deletions(-)
>
> Index: linux/drivers/pci/probe.c
> ===================================================================
> --- linux.orig/drivers/pci/probe.c
> +++ linux/drivers/pci/probe.c
> @@ -1632,6 +1632,18 @@ unsigned int pci_scan_child_bus(struct p
> return max;
> }
>
> +/**
> + * pcibios_root_bridge_prepare - Platform-specific host bridge setup.
> + * @bridge: Host bridge to set up.
> + *
> + * Default empty implementation. Replace with an architecture-specific setup
> + * routine, if necessary.
> + */
> +int __weak pcibios_root_bridge_prepare(struct pci_host_bridge *bridge)
> +{
> + return 0;
> +}
> +
> struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
> struct pci_ops *ops, void *sysdata, struct list_head *resources)
> {
> @@ -1665,6 +1677,10 @@ struct pci_bus *pci_create_root_bus(stru
> bridge->dev.parent = parent;
> bridge->dev.release = pci_release_bus_bridge_dev;
> dev_set_name(&bridge->dev, "pci%04x:%02x", pci_domain_nr(b), bus);
> + error = pcibios_root_bridge_prepare(bridge);
> + if (error)
> + goto bridge_dev_reg_err;
> +
> error = device_register(&bridge->dev);
> if (error)
> goto bridge_dev_reg_err;
> Index: linux/include/linux/pci.h
> ===================================================================
> --- linux.orig/include/linux/pci.h
> +++ linux/include/linux/pci.h
> @@ -378,6 +378,8 @@ void pci_set_host_bridge_release(struct
> void (*release_fn)(struct pci_host_bridge *),
> void *release_data);
>
> +int pcibios_root_bridge_prepare(struct pci_host_bridge *bridge);
> +
> /*
> * The first PCI_BRIDGE_RESOURCE_NUM PCI bus resources (those that correspond
> * to P2P or CardBus bridge windows) go in a table. Additional ones (for
> Index: linux/arch/x86/pci/acpi.c
> ===================================================================
> --- linux.orig/arch/x86/pci/acpi.c
> +++ linux/arch/x86/pci/acpi.c
> @@ -593,6 +593,15 @@ struct pci_bus * __devinit pci_acpi_scan
> return bus;
> }
>
> +int pcibios_root_bridge_prepare(struct pci_host_bridge *bridge)
> +{
> + struct pci_sysdata *sd = bridge->bus->sysdata;
> + struct pci_root_info *info = container_of(sd, struct pci_root_info, sd);
> +
> + ACPI_HANDLE_SET(&bridge->dev, info->bridge->handle);
> + return 0;
> +}
> +
> int __init pci_acpi_init(void)
> {
> struct pci_dev *dev = NULL;
> Index: linux/arch/ia64/pci/pci.c
> ===================================================================
> --- linux.orig/arch/ia64/pci/pci.c
> +++ linux/arch/ia64/pci/pci.c
> @@ -396,6 +396,14 @@ out1:
> return NULL;
> }
>
> +int pcibios_root_bridge_prepare(struct pci_host_bridge *bridge)
> +{
> + struct pci_controller *controller = bridge->bus->sysdata;
> +
> + ACPI_HANDLE_SET(&bridge->dev, controller->acpi_handle);
> + return 0;
> +}
> +
> static int __devinit is_valid_resource(struct pci_dev *dev, int idx)
> {
> unsigned int i, type_mask = IORESOURCE_IO | IORESOURCE_MEM;
> Index: linux/drivers/pci/pci-acpi.c
> ===================================================================
> --- linux.orig/drivers/pci/pci-acpi.c
> +++ linux/drivers/pci/pci-acpi.c
> @@ -302,24 +302,6 @@ static int acpi_pci_find_device(struct d
> return 0;
> }
>
> -static int acpi_pci_find_root_bridge(struct device *dev, acpi_handle *handle)
> -{
> - int num;
> - unsigned int seg, bus;
> -
> - /*
> - * The string should be the same as root bridge's name
> - * Please look at 'pci_scan_bus_parented'
> - */
> - num = sscanf(dev_name(dev), "pci%04x:%02x", &seg, &bus);
> - if (num != 2)
> - return -ENODEV;
> - *handle = acpi_get_pci_rootbridge_handle(seg, bus);
> - if (!*handle)
> - return -ENODEV;
> - return 0;
> -}
> -
> static void pci_acpi_setup(struct device *dev)
> {
> struct pci_dev *pci_dev = to_pci_dev(dev);
> @@ -378,7 +360,6 @@ static void pci_acpi_cleanup(struct devi
> static struct acpi_bus_type acpi_pci_bus = {
> .bus = &pci_bus_type,
> .find_device = acpi_pci_find_device,
> - .find_bridge = acpi_pci_find_root_bridge,
> .setup = pci_acpi_setup,
> .cleanup = pci_acpi_cleanup,
> };
> Index: linux/drivers/acpi/pci_root.c
> ===================================================================
> --- linux.orig/drivers/acpi/pci_root.c
> +++ linux/drivers/acpi/pci_root.c
> @@ -107,24 +107,6 @@ 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 *root;
> - acpi_handle handle = NULL;
> -
> - mutex_lock(&acpi_pci_root_lock);
> - list_for_each_entry(root, &acpi_pci_roots, node)
> - if ((root->segment == (u16) seg) &&
> - (root->secondary.start == (u16) bus)) {
> - handle = root->device->handle;
> - break;
> - }
> - mutex_unlock(&acpi_pci_root_lock);
> - return handle;
> -}
> -
> -EXPORT_SYMBOL_GPL(acpi_get_pci_rootbridge_handle);
> -
> /**
> * acpi_is_root_bridge - determine whether an ACPI CA node is a PCI root bridge
> * @handle - the ACPI CA node in question.
> Index: linux/include/acpi/acpi_bus.h
> ===================================================================
> --- linux.orig/include/acpi/acpi_bus.h
> +++ linux/include/acpi/acpi_bus.h
> @@ -443,7 +443,6 @@ struct acpi_pci_root {
> /* helper */
> acpi_handle acpi_get_child(acpi_handle, u64);
> int acpi_is_root_bridge(acpi_handle);
> -acpi_handle acpi_get_pci_rootbridge_handle(unsigned int, unsigned int);
> struct acpi_pci_root *acpi_pci_find_root(acpi_handle handle);
> #define DEVICE_ACPI_HANDLE(dev) ((acpi_handle)ACPI_HANDLE(dev))
>
>


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