linux-kernel - Re: [PATCH 06/20] ARM64 / ACPI: Introduce some PCI functions when PCI is enabled

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Date:	Mon, 20 Jan 2014 22:13:55 +0800
From:	Hanjun Guo <hanjun.guo@...aro.org>
To:	Arnd Bergmann <arnd@...db.de>
CC:	linaro-kernel@...ts.linaro.org,
	Mark Rutland <mark.rutland@....com>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Rob Herring <robh@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Olof Johansson <olof@...om.net>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	linux-kernel@...r.kernel.org, linaro-acpi@...ts.linaro.org,
	linux-acpi@...r.kernel.org, patches@...aro.org,
	Grant Likely <grant.likely@...aro.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	linux-arm-kernel@...ts.infradead.org, Charles.Garcia-Tobin@....com
Subject: Re: [PATCH 06/20] ARM64 / ACPI: Introduce some PCI functions when
 PCI is enabled

On 2014年01月20日 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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