linux-kernel - Re: [Alternative][PATCH] ACPI / PCI: Set root bridge ACPI handle in advance, v2

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Message-ID: <4001131.iQGP87KxgR@vostro.rjw.lan>
Date:	Fri, 11 Jan 2013 22:53:31 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Tony Luck <tony.luck@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>, Jiang Liu <liuj97@...il.com>,
	Myron Stowe <myron.stowe@...hat.com>
Subject: Re: [Alternative][PATCH] ACPI / PCI: Set root bridge ACPI handle in advance, v2

On Thursday, January 10, 2013 01:05:24 AM Rafael J. Wysocki wrote:
> On Wednesday, January 09, 2013 03:27:29 PM Yinghai Lu wrote:
> > On Wed, Jan 9, 2013 at 3:06 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> > > On Wednesday, January 09, 2013 03:16:59 PM Bjorn Helgaas wrote:
> > >> On Wed, Jan 9, 2013 at 2:33 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().
> > >> >
> > >> > 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.
> > >> >
> > >> > Included is a fix for breakage on systems with non-ACPI PCI host
> > >> > bridges from Bjorn Helgaas.
> > >> >
> > >> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > >>
> > >> Looks good to me!
> > >>
> > >> Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>
> > >
> > > Thanks!
> > >
> > > I'll wait for comments from the others, if any, and put it into my acpi-scan
> > > branch after a couple of days.  It doesn't need to be there technically, but
> > > it's kind of related.
> > 
> > I tested it with acpi-scan and pci-root-bus-hotplug patchset, and it works well.
> > so
> > Acked-by: Yinghai Lu <yinghai@...nel.org>
> 
> Thanks!
> 
> > BTW, found one left over of change about ->acpi_handle==> ACPI_HANDLE..
> 
> Can you please submit that patch with a proper changelog?
> 
> It is a mainline bug now (and a build regression for that matter), so I'd like to
> push the fix to Linus for v3.8-rc4.

May I have your sign-off for the patch below at least?

Rafael


> > Index: linux-2.6/drivers/acpi/glue.c
> > ===================================================================
> > --- linux-2.6.orig/drivers/acpi/glue.c
> > +++ linux-2.6/drivers/acpi/glue.c
> > @@ -311,7 +311,7 @@ static int acpi_platform_notify(struct d
> >         if (!ret) {
> >                 struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
> > 
> > -               acpi_get_name(dev->acpi_handle, ACPI_FULL_PATHNAME, &buffer);
> > +               acpi_get_name(ACPI_HANDLE(dev), ACPI_FULL_PATHNAME, &buffer);
> >                 DBG("Device %s -> %s\n", dev_name(dev), (char *)buffer.pointer);
> >                 kfree(buffer.pointer);
> >         } else
> > 
> > 


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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