Messages in this thread | | | Date | Mon, 7 Jul 2008 15:01:31 +0100 (BST) | From | "Maciej W. Rozycki" <> | Subject | Re: [PATCH 2/2] acpi: Disable IRQ 0 through I/O APIC for some HP systems |
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On Mon, 7 Jul 2008, Rafael J. Wysocki wrote:
> > It makes absolutely no sense and should be harmful to call > > clear_IO_APIC_pin(apic1, pin1) here, because both apic1 and pin1 should be > > equal to -1 here. If it has to be called, then I suppose the DMI matching > > did not work and the workaround has not been enabled. > > Do you realize that the clear_IO_APIC_pin(apic1, pin1) thing is _only_ called > _IF_ the DMI matching did work?
Well, it is the very intent of the DMI quirk to set apic1 and pin1 both to -1, as a result of IRQ0 being absent from our I/O APIC interrupt routing table. Therefore if the quirk did indeed work, a call to clear_IO_APIC_pin() is useless and likely harmful as its callees don't do range checking (my understanding of code is it results in random poking at the local APIC through the FIX_APIC_BASE fixmap). There should be nothing to clear too, as interrupt redirection entries for all the I/O APIC inputs are cleared (the mask is set to 1 and the remaining fields zeroed) when clear_IO_APIC() is called from enable_IO_APIC() upon initialization and all the unused ones (not referred to from anywhere in the interrupt routing table) are never touched afterwards.
Maciej
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