Re: [PATCH] cpufreq/intel_pstate: Add kernel command line option disable intel_pstate.

[Rafael J. Wysocki]

On Friday, February 15, 2013 09:53:24 AM Viresh Kumar wrote:
> On Fri, Feb 15, 2013 at 12:08 AM,  <dirk.brandewie@xxxxxxxxx> wrote:
> > From: Dirk Brandewie <dirk.brandewie@xxxxxxxxx>
> >
> > When intel_pstate is configured into the kernel it will become the
> > perferred scaling driver for processors that is supports.  Allow the
> 
> s/perferred/preferred
> 
> s/is/it
> 
> > user to override this by adding:
> >    intel_pstate=disable
> > on the kernel command line.
> >
> > Signed-off-by: Dirk Brandewie <dirk.j.brandewie@xxxxxxxxx>
> > ---
> >  Documentation/kernel-parameters.txt |    5 +++++
> >  drivers/cpufreq/intel_pstate.c      |   16 ++++++++++++++++
> >  2 files changed, 21 insertions(+), 0 deletions(-)
> >
> > diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> > index 6c72381..41c5d9e 100644
> > --- a/Documentation/kernel-parameters.txt
> > +++ b/Documentation/kernel-parameters.txt
> > @@ -1131,6 +1131,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
> >                         0       disables intel_idle and fall back on acpi_idle.
> >                         1 to 6  specify maximum depth of C-state.
> >
> > +       intel_pstate=  [X86]
> > +                      disable
> > +                        Do not enable intel_pstate as the default
> > +                        scaling driver for the supported processors
> > +
> >         intremap=       [X86-64, Intel-IOMMU]
> >                         on      enable Interrupt Remapping (default)
> >                         off     disable Interrupt Remapping
> > diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> > index e879963..9cbb733 100644
> > --- a/drivers/cpufreq/intel_pstate.c
> > +++ b/drivers/cpufreq/intel_pstate.c
> > @@ -773,11 +773,16 @@ static void intel_pstate_exit(void)
> >  }
> >  module_exit(intel_pstate_exit);
> >
> > +static int no_load;
> > +
> >  static int __init intel_pstate_init(void)
> >  {
> >         int rc = 0;
> >         const struct x86_cpu_id *id;
> >
> > +       if (no_load)
> > +               return -ENODEV;
> > +
> >         id = x86_match_cpu(intel_pstate_cpu_ids);
> >         if (!id)
> >                 return -ENODEV;
> > @@ -802,6 +807,17 @@ out:
> >  }
> >  device_initcall(intel_pstate_init);
> >
> > +static int __init intel_pstate_setup(char *str)
> 
> Parameter to this is really not required. By default intel_pstate
> driver is enabled, so just past disable_intel_pstate from command line
> without any args.

Well, quite frankly, I'm fine with both.  It all boils down to passing a
specific string on the kernel command line.

Thanks,
Rafael


> > +{
> > +       if (!str)
> > +               return -EINVAL;
> > +
> > +       if (!strcmp(str, "disable"))
> > +               no_load = 1;
> > +       return 0;
> > +}
> > +early_param("intel_pstate", intel_pstate_setup);
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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