Re: [Patch v2] x86, ACPI, irq: Add a quirk to override SCI polarity for HyperV

[Jiang Liu <jiang.liu@linux.intel.com>]

On 2015/8/19 16:40, Thomas Gleixner wrote:
> On Wed, 19 Aug 2015, Thomas Gleixner wrote:
>> On Wed, 19 Aug 2015, Jiang Liu wrote:
>>> On 2015/8/19 14:45, Rafael J. Wysocki wrote:
>>>> Well, the regression at hand has just shown that the assertion in the
>>>> changelog of that commit ("no need for for special treatment for GSI
>>>> used by ACPI SCI") does not really hold.  So, if the only motivation
>>>> for it was to get rid of one extra check in mp_unregister_gsi()
>>>> (mp_register_gsi() still needs to check if it is dealing with the SCI
>>>> anyway), I'd vote for reverting it.
>>> Hi Rafael,
>>> 	The motivation is to treat SCI as normal IOAPIC interrupt so
>>> we could enforce stricter pin attribute checking. Now it does reveal
>>> flaws in ACPI BIOS implementations, but we ran into trouble about how to
>>> handle those flaws:(
>>
>> The intent of this change is entirely correct, though it seems that
>> reality of ACPI is just different.
>>
>> To be on the safe side of things, I agree with Rafael that we should
>> revert that patch instead of introducing a single platform quirk.
> 
> Jiang,
> 
> can you please prepare a revert patch for this?
Hi Rafael and Thomas,
	I have tried to revert commit cd68f6bd53cf, but found
it's not an easy task now.
	When converting to hierarchical irqdomain, the IOAPIC
internal and interfaces have changed much, and seems no easy
way to revert cd68f6bd53cf. There may be three possible solutions
here:
1) use quirk to correct SCI polarity, as the patch does.
2) change IOAPIC interfaces to provide a special way to
   handle SCI interrupt.
3) change drivers/acpi/pci_link.c to penalize SCI IRQ so it
   won't be used for PCI IRQ if SCI polarity conflicts with
   PCI IRQ polarity.

What's your thoughts here?

Thanks!
Gerry