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SubjectRe: [PATCH 2/2] acpi: Disable IRQ 0 through I/O APIC for some HP systems
Date
On Monday, 7 of July 2008, Maciej W. Rozycki wrote:
> On Mon, 7 Jul 2008, Rafael J. Wysocki wrote:
>
> > BTW, did you even to look at the code _as_ _is_ in linux-next?
>
> Well, I hope it has not changed too much since my recent work in this
> area...

Please look at it.

> > In fact, it is _impossible_ that either apic1 or pin1 are equal to -1 at this
> > point, because of this part:
>
> With the workaround activated it is virtually certain.

Which workaround?

There are no any workarounds related to this problem in the 20080704 linux-next
and that's what my patch was against.

> > /*
> > * Some BIOS writers are clueless and report the ExtINTA
> > * I/O APIC input from the cascaded 8259A as the timer
> > * interrupt input. So just in case, if only one pin
> > * was found above, try it both directly and through the
> > * 8259A.
> > */
> > if (pin1 == -1) {
> > pin1 = pin2;
> > apic1 = apic2;
> > no_pin1 = 1;
> > } else if (pin2 == -1) {
> > pin2 = pin1;
> > apic2 = apic1;
> > }
> >
> > that originates from your patch.
>
> And the conclusion is? If we leave MP-table setups aside as irrelevant
> for this configuration, we can be almost certain apic2 and pin2 are both
> equal to -1 at this point. This is because (unlike the MP table) ACPI has
> no provisions in its tables for ExtINTA APIC interrupt inputs. Therefore
> the only case apic2 and pin2 may not be equal -1 here is when the firmware
> had set up one of the inputs as such in the hardware before initiating
> bootstrap which has been subsequently noted by a piece of code in
> enable_IO_APIC() which examines the I/O APIC for such a condition.
>
> I have taken these circumstances very much into account when preparing
> the workaround, based on the assumption that if the firmware has set up an
> I/O APIC line as an ExtINTA interrupt, then it means it considers it
> suitable to use in such a manner. This furthermore implies the line
> should be safe to be used in any valid 8259A mode of operation, such as
> one we use to forward IRQ0 transparently through the 8259A (we
> double-check it just in case though, as workarounds for hardware bugs in
> the past made it not always true). The workaround therefore applies to
> genuine IRQ0 routing as reported by ACPI only and not any possible legacy
> ExtINTA fallback that we may attempt to use.
>
> Of course, as determined previously, the ExtINTA line is not safe to be
> used on your box, but it has not been set up by the firmware as an ExtINTA
> interrupt either, so the assumption mentioned above remains valid and has
> no negative impact on your system. At this point all of apic1, apic2,
> pin1 and pin2 should be equal -1, which means the reassignments you quoted
> make no changes to the variables.
>
> > End even without this part apic1 and pin1 are _not_ equal to -1 on this box
> > (apic2 and pin2 are, but that's a different matter).
>
> Which means the workaround has not triggered and the rest of cosideration
> is therefore irrelevant. Please get us these DMI IDs, so that we can see
> what's wrong with the quirk.

I used those DMI IDs and your quirk didn't work, even after removing the
dependency of acpi_dmi_table[] from __i386__. For this reason, I prepared an
alternative patch that did work and posted it for your information.

Now, you're saying that my patch couldn't work, while in fact it did.

Thanks,
Rafael


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