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

[Thomas Gleixner <tglx@linutronix.de>]

On Thu, 20 Aug 2015, Jiang Liu wrote:
> On 2015/8/20 17:15, Thomas Gleixner wrote:
> > On Thu, 20 Aug 2015, Jiang Liu wrote:
> >> 	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.
> > 
> > Stupid question. Is the SCI polarity ever the opposite of PCI
> > polarity? I.e. is such a ACPI override valid at all? 
> Hi Thomas,
> 	I have analyzed another system which works:
> 1) SCI(IRQ9) works in level, high mode (so such an ACPI override is valid)
> 2) there's a flag to detect whether system works in PIC or APIC mode.
> 3) IRQ9 may be used for PCI IRQ if system works in PIC mode.

Why?

> 4) IRQ9 won't be used for PCI IRQ if system works in APIC mode.
> Based on the above observation, I feel solution 3) may be the best one.

Can you whip up a patch and test it on hyperv and maybe other machines
which have that SCI override.

Thanks

	tglx