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    SubjectRe: [PATCH] [RFC] ondemand governor: dynamic cpufreq scaling with different CPUs
    On Mon, Aug 1, 2011 at 7:51 AM, Len Brown <> wrote:
    > Re: software vs hardware coordination
    > Speaking for Intel, everything we make, from hand-sets to supercomputers
    > supports hardware coorination.
    > Think about it -- if we did not, then we would not be able
    > to support a legacy OS that doesn't know how to do SW coordination.
    > HW coordiation is the simplest thing for the SW because
    > SW doesn't have to know anything at all about topology constraints.
    > It is also the simplest thing for the BIOS, which doesn't have
    > to correctly describe topology.
    > Yes, there is an MSR bit that the BIOS can flip to disable
    > HW coordination.  90% of the time that bit is set it is a BIOS bug.
    > eg. the bit is set, but the BIOS fails to properly set up the
    > ACPI tables to properly enable SW coordination, resulting
    > in a system with really strange performance issues.
    > Indeed, I proposed before, and I will propose again that
    > the underlying ACPI _PSD support behind SW coordination
    > be completely removed from Linux.
    > Venki,
    > I recall that you mentioned one platform that depends on it --
    > and I'd  like to understand that issue and address it with a quirk
    > rather than expose all systems to BIOS bugs due to bogus _PSD support.

    Agree. Addressing this as a quirk would be fine. The processor that
    needs it is E74xx series, IIRC.


    > Winston,
    > Your system is running in SW coordination mode?
    > What do you see if you run with the patch below?
    > I'd be intersted to see the output from adpidump for your system.
    > thanks,
    > -Len Brown
    > Intel Open Source Technology Center
    > ---
    > diff --git a/include/acpi/pdc_intel.h b/include/acpi/pdc_intel.h
    > index 552637b..d081595 100644
    > --- a/include/acpi/pdc_intel.h
    > +++ b/include/acpi/pdc_intel.h
    > @@ -22,7 +22,6 @@
    >                                         ACPI_PDC_C_C1_HALT | \
    > -                                        ACPI_PDC_SMP_P_SWCOORD | \
    >                                         ACPI_PDC_SMP_P_HWCOORD | \
    >                                         ACPI_PDC_P_FFH)
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