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    SubjectRe: [PATCH v2] acpi: Fix regression where _PPC is not read at boot even when ignore_ppc=0
    On Thu, Apr 30, 2009 at 09:25:56AM +0200, Ingo Molnar wrote:

    > OTOH, if you rely on me figuring out which patch to revert and what
    > to do, it will take an indeterminate amount of time - together with
    > all the other items in my 'would be nice to hack on, given a bit of
    > free time' queue :)

    Here's Darrick's patch:

    Earlier, Ingo Molnar posted a patch to make it so that the kernel would avoid
    reading _PPC on his broken T60. Unfortunately, it seems that with Thomas
    Renninger's patch last July to eliminate _PPC evaluations when the processor
    driver loads, the kernel never actually reads _PPC at all! This is problematic
    if you happen to boot your non-T60 computer in a state where the BIOS _wants_
    _PPC to be something other than zero.

    So, put the _PPC evaluation back into acpi_processor_get_performance_info if
    ignore_ppc isn't 1.

    This second version restores the correct function call, which simplifies
    the patch. I apologize for the churn and the poor eyesight.

    Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
    ---

    drivers/acpi/processor_perflib.c | 6 +++++-
    1 files changed, 5 insertions(+), 1 deletions(-)


    diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c
    index cafb410..85af717 100644
    --- a/drivers/acpi/processor_perflib.c
    +++ b/drivers/acpi/processor_perflib.c
    @@ -348,7 +348,11 @@ static int acpi_processor_get_performance_info(struct acpi_processor *pr)
    if (result)
    goto update_bios;

    - return 0;
    + /* We need to call _PPC once when cpufreq starts */
    + if (ignore_ppc != 1)
    + result = acpi_processor_get_platform_limit(pr);
    +
    + return result;

    /*
    * Having _PPC but missing frequencies (_PSS, _PCT) is a very good hint that
    --
    Matthew Garrett | mjg59@srcf.ucam.org

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