linux-kernel - Re: [PATCH] cpufreq/intel_pstate: Add kernel command line option disable intel

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Date:	Fri, 15 Feb 2013 09:53:24 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	dirk.brandewie@...il.com
Cc:	rjw@...k.pl, linux-kernel@...r.kernel.org, cpufreq@...r.kernel.org,
	Dirk Brandewie <dirk.j.brandewie@...el.com>
Subject: Re: [PATCH] cpufreq/intel_pstate: Add kernel command line option
 disable intel_pstate.

On Fri, Feb 15, 2013 at 12:08 AM,  <dirk.brandewie@...il.com> wrote:
> From: Dirk Brandewie <dirk.brandewie@...il.com>
>
> 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@...el.com>
> ---
>  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.

> +{
> +       if (!str)
> +               return -EINVAL;
> +
> +       if (!strcmp(str, "disable"))
> +               no_load = 1;
> +       return 0;
> +}
> +early_param("intel_pstate", intel_pstate_setup);
--
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