Re: [PATCH 06/20] ARM64 / ACPI: Introduce some PCI functions whenPCI is enabled

[Hanjun Guo]

On 2014å01æ20æ 16:20, Arnd Bergmann wrote:
> On Monday 20 January 2014 16:08:01 Hanjun Guo wrote:
> > > > diff --git a/drivers/acpi/plat/arm-core.c b/drivers/acpi/plat/arm-core.c
> > > > index 3c8521d..1835b21 100644
> > > > --- a/drivers/acpi/plat/arm-core.c
> > > > +++ b/drivers/acpi/plat/arm-core.c
> > > > @@ -100,6 +100,25 @@ int acpi_gsi_to_irq(u32 gsi, unsigned int *irq)
> > > >   }
> > > >   EXPORT_SYMBOL_GPL(acpi_gsi_to_irq);
> > > >   
> > > > +int acpi_isa_irq_to_gsi(unsigned isa_irq, u32 *gsi)
> > > > +{
> > > > +    return -1;
> > > > +}
> > > > +
> > > > +int acpi_register_ioapic(acpi_handle handle, u64 phys_addr, u32 gsi_base)
> > > > +{
> > > > +    /* TBD */
> > > > +    return -EINVAL;
> > > > +}
> > > > +EXPORT_SYMBOL(acpi_register_ioapic);
> > > > +
> > > > +int acpi_unregister_ioapic(acpi_handle handle, u32 gsi_base)
> > > > +{
> > > > +    /* TBD */
> > > > +    return -EINVAL;
> > > > +}
> > > > +EXPORT_SYMBOL(acpi_unregister_ioapic);
> > > > +
> > > My feeling is that these are better handled in the ACPI code by not
> > > calling them on architectures that have no ISA or no IOAPIC support.
> > >
> > > We have configuration symbols for both, so you don't have to make
> > > it depend on CONFIG_ARM64 or CONFIG_X86.
> > Do you mean introduce a stub function when there is no ISA support?
> Do you anticipate ISA devices on ARM64? I hope not ;-)

me too :)

> My guess is that whatever code calls this function should be disabled
> in reduced hw mode.

ok, that would be make sense, will update it in next version.

> > acpi_register_ioapic()/acpi_unregister_ioapic() will be used for IOAPIC
> > hotplug and GIC distributor is something like IOAPIC on x86, so I think
> > these two functions can be reserved for future use.
> But GIC is not hotplugged, is it? It still sounds x86 specific to me.

Well, if we want to do physical CPU hotplug on ARM/ARM64 (maybe years 
later?),
then GIC add/remove is needed because we have to remove GIC
on the SoC too when we remove the physical CPU.

Thanks
Hanjun
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