Re: [Linaro-acpi] [PATCH V1 10/11] pci, acpi: Provide generic way to assign bus domain number.

[Tomasz Nowicki]

On 03.11.2015 17:10, Lorenzo Pieralisi wrote:
> On Tue, Oct 27, 2015 at 05:38:41PM +0100, Tomasz Nowicki wrote:
> > Architectures which support PCI_DOMAINS_GENERIC (like ARM64)
> > cannot call pci_bus_assign_domain_nr along ACPI PCI host bridge
> > initialization since this function needs valid parent device reference
> > to be able to retrieve domain number (aka segment).
> >
> > We can omit that blocker and pass down host bridge device via
> > pci_create_root_bus parameter and then be able to evaluate _SEG method
> > being in pci_bus_assign_domain_nr.
> >
> > Note that _SEG method is optional, therefore _SEG absence means
> > that all PCI buses belong to domain 0.
> >
> > Signed-off-by: Tomasz Nowicki <tn@xxxxxxxxxxxx>
> > ---
> >   drivers/acpi/pci_root.c |  2 +-
> >   drivers/pci/pci.c       | 32 +++++++++++++++++++++++++++-----
> >   2 files changed, 28 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> > index 850d7bf..e682dc6 100644
> > --- a/drivers/acpi/pci_root.c
> > +++ b/drivers/acpi/pci_root.c
> > @@ -839,7 +839,7 @@ struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
> >
> >   	pci_acpi_root_add_resources(info);
> >   	pci_add_resource(&info->resources, &root->secondary);
> > -	bus = pci_create_root_bus(NULL, busnum, ops->pci_ops,
> > +	bus = pci_create_root_bus(&device->dev, busnum, ops->pci_ops,
> >   				  sysdata, &info->resources);
>
> If I read x86 code correctly, they rely on the first argument to be
> NULL, I think you would break x86 by doing that, see:
>
> arch/x86/pci/acpi.c (pcibios_root_bridge_prepare())
>
> By the way, can't we move the code setting up the ACPI_COMPANION
> to core PCI code and stop relying on sysdata for that ?

Yes, that will break x86&ia64 but as you said it may be overcome with 
consolidation of ACPI_COMPANION into the core code.

Tomasz
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