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

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Message-ID: <alpine.DEB.2.11.1508201247370.3873@nanos>
Date:	Thu, 20 Aug 2015 13:13:34 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Jiang Liu <jiang.liu@...ux.intel.com>
cc:	"Rafael J. Wysocki" <rafael@...nel.org>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	Nick Meier <nmeier@...rosoft.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: Re: [Patch v2] x86, ACPI, irq: Add a quirk to override SCI polarity
 for HyperV

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
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