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    Subject[tip:x86/autoprobe] x86, acpi: Load acpi-cpufreq from processor driver automatically
    Commit-ID:  848fd8ee1881650226f11113e17b0118a792e12f
    Gitweb: http://git.kernel.org/tip/848fd8ee1881650226f11113e17b0118a792e12f
    Author: Andi Kleen <ak@linux.intel.com>
    AuthorDate: Mon, 19 Dec 2011 15:46:30 -0800
    Committer: H. Peter Anvin <hpa@linux.intel.com>
    CommitDate: Mon, 19 Dec 2011 15:49:43 -0800
    x86, acpi: Load acpi-cpufreq from processor driver automatically

    The only left over hole in automatic cpufreq driver loading was the loading
    of ACPI cpufreq. This driver should be loaded when ACPI supports a _PDC
    method and the CPU vendor wants to use acpi cpufreq.

    Simply add a request module call to the acpi processor core driver
    when this is true. This seems like the simplest solution for this.

    Cc: lenb@kernel.org
    Signed-off-by: Andi Kleen <ak@linux.intel.com>
    Link: http://lkml.kernel.org/r/1324338394-4670-5-git-send-email-andi@firstfloor.org
    Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
    ---
    drivers/acpi/processor_driver.c | 1 +
    drivers/acpi/processor_perflib.c | 22 ++++++++++++++++++++++
    include/acpi/processor.h | 1 +
    3 files changed, 24 insertions(+), 0 deletions(-)
    diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
    index 9d7bc9f..9e933ed 100644
    --- a/drivers/acpi/processor_driver.c
    +++ b/drivers/acpi/processor_driver.c
    @@ -499,6 +499,7 @@ static int __cpuinit acpi_processor_add(struct acpi_device *device)

    #ifdef CONFIG_CPU_FREQ
    acpi_processor_ppc_has_changed(pr, 0);
    + acpi_processor_load_module(pr);
    #endif
    acpi_processor_get_throttling_info(pr);
    acpi_processor_get_limit_info(pr);
    diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c
    index 85b3237..0af48a8 100644
    --- a/drivers/acpi/processor_perflib.c
    +++ b/drivers/acpi/processor_perflib.c
    @@ -240,6 +240,28 @@ void acpi_processor_ppc_exit(void)
    acpi_processor_ppc_status &= ~PPC_REGISTERED;
    }

    +/*
    + * Do a quick check if the systems looks like it should use ACPI
    + * cpufreq. We look at a _PCT method being available, but don't
    + * do a whole lot of sanity checks.
    + */
    +void acpi_processor_load_module(struct acpi_processor *pr)
    +{
    + static int requested;
    + acpi_status status = 0;
    + struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
    +
    + if (!arch_has_acpi_pdc() || requested)
    + return;
    + status = acpi_evaluate_object(pr->handle, "_PCT", NULL, &buffer);
    + if (!ACPI_FAILURE(status)) {
    + printk(KERN_INFO PREFIX "Requesting acpi_cpufreq\n");
    + request_module_nowait("acpi_cpufreq");
    + requested = 1;
    + }
    + kfree(buffer.pointer);
    +}
    +
    static int acpi_processor_get_performance_control(struct acpi_processor *pr)
    {
    int result = 0;
    diff --git a/include/acpi/processor.h b/include/acpi/processor.h
    index 610f6fb..da57fdc 100644
    --- a/include/acpi/processor.h
    +++ b/include/acpi/processor.h
    @@ -224,6 +224,7 @@ struct acpi_processor_errata {
    } piix4;
    };

    +extern void acpi_processor_load_module(struct acpi_processor *pr);
    extern int acpi_processor_preregister_performance(struct
    acpi_processor_performance
    __percpu *performance);

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