Date:	Sun, 16 Dec 2012 21:27:49 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	David Miller <davem@...emloft.net>, tony.luck@...el.com,
	"H. Peter Anvin" <hpa@...or.com>, Jiang Liu <liuj97@...il.com>
Subject: Re: [PATCH] ACPI / PCI: Set root bridge ACPI handle in advance

On Sun, Dec 16, 2012 at 2:25 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> 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().
> Namely, if pci_acpi_scan_root() could easily pass the root bridge's
> ACPI handle to pci_create_root_bus(), the latter could set the ACPI
> handle in its struct pci_host_bridge object's "dev" member before
> passing it to device_register() and steps 6-8 above wouldn't be
> necessary any more.
>
> To make that happen I decided to repurpose the 4th argument of
> pci_create_root_bus(), because that allowed me to avoid defining
> additional callbacks or similar things and didn't seem to impact
> architectures without ACPI substantially.
>
> Only x86 and ia64 are affected directly, there should be no
> functional changes resulting from this on other architectures.

that is good one to avoid that find_root_bridge...

>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>
> Should apply to the current Linus' tree, boots correctly on x86(-64).



>
> Thanks,
> Rafael
>
> ---
>  arch/ia64/pci/pci.c              |    5 ++++-
>  arch/powerpc/kernel/pci-common.c |    3 ++-
>  arch/sparc/kernel/pci.c          |    3 ++-
>  arch/x86/pci/acpi.c              |    5 ++++-
>  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              |    9 ++++++++-
>  9 files changed, 31 insertions(+), 48 deletions(-)

you need to update other arch for pci_create_root_bus

arch/powerpc/kernel/pci-common.c:       bus =
pci_create_root_bus(hose->parent, hose->first_busno,
arch/s390/pci/pci.c:    zdev->bus = pci_create_root_bus(NULL,
ZPCI_BUS_NR, &pci_root_ops,
arch/sparc/kernel/pci.c:        bus = pci_create_root_bus(parent,
pbm->pci_first_busno, pbm->pci_ops,
drivers/parisc/dino.c:  dino_dev->hba.hba_bus = bus =
pci_create_root_bus(&dev->dev,
drivers/parisc/lba_pci.c:               pci_create_root_bus(&dev->dev,
lba_dev->hba.bus_num.start,


>
> Index: linux/arch/x86/pci/acpi.c
> ===================================================================
> --- linux.orig/arch/x86/pci/acpi.c
> +++ linux/arch/x86/pci/acpi.c
> @@ -450,6 +450,7 @@ struct pci_bus * __devinit pci_acpi_scan
>         LIST_HEAD(resources);
>         struct pci_bus *bus = NULL;
>         struct pci_sysdata *sd;
> +       struct pci_root_sys_info si;
>         int node;
>  #ifdef CONFIG_ACPI_NUMA
>         int pxm;
> @@ -486,6 +487,8 @@ struct pci_bus * __devinit pci_acpi_scan
>         sd = &info->sd;
>         sd->domain = domain;
>         sd->node = node;
> +       si.acpi_node.handle = device->handle;
> +       si.sysdata = sd;

maybe you can try to have si.acpi_handle directly ?

Yinghai
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