On Tue, Dec 25, 2012 at 2:42 PM, Rafael J. Wysocki <rjw@xxxxxxx> wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> 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@xxxxxxxxx>
> ---
>
> 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.
>
> Thanks,
> Rafael
>
> ---
> 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;
> +}
> +
You may need to put that weak version to another file.
some version gcc/ld will inline the weak version directly if it is in same file.
otherwise
Acked-by: Yinghai Lu <yinghai@xxxxxxxxxx>
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