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    SubjectRe: [PATCH] intel_idle: PCI quirk to prevent Lenovo Ideapad s10-3 boot hang

    > > > > we check (and clear) that bit only if the acpi tables
    > > > > tell us to do so.
    > > >
    > > > Do the tables tell us to do so on this platform?
    > >
    > > In this configuration, yes, otherwise acpi_idle
    > > would have failed in exactly the same way.
    >
    > So why is intel_idle not paying attention to what the platform is
    > requesting?

    ACPI's BM_STS mechanism is obsolete, and is fundmentally
    incompatible with a tickless OS. The status bit is a NO-OP
    on most modern chip-sets under normal conditions.
    However, even when not a NO-OP, it is supposed to
    be just an indicator and clearing it should have
    no functional effect on the hardware except to
    re-arm the hardware that looks for BM_STS.

    Clearing BM_STS on the NM10 chipset at boot-time to
    make the system boot has nothing to do with
    "what the platform is requesting".
    It is a workaround for a platform bug that is randomly
    masked by how the behaviour of the legacy ACPI OS.

    intel_idle it knows nothing about ACPI, and it never will.

    thanks,
    Len Brown, Intel Open Source Technology Center




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