linux-kernel - Re: [PATCH v11 11/11] Documentation: amd-pstate: introduce new global sysfs attributes

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Message-ID: <43acfc0e-167b-3514-76ba-db3db8810bbc@amd.com>
Date:   Thu, 19 Jan 2023 11:03:56 +0530
From:   Wyes Karny <wyes.karny@....com>
To:     Perry Yuan <perry.yuan@....com>
Cc:     Deepak.Sharma@....com, Nathan.Fontenot@....com,
        Alexander.Deucher@....com, Shimmer.Huang@....com,
        Xiaojian.Du@....com, Li.Meng@....com, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, rafael.j.wysocki@...el.com,
        Mario.Limonciello@....com, viresh.kumar@...aro.org,
        ray.huang@....com
Subject: Re: [PATCH v11 11/11] Documentation: amd-pstate: introduce new global
 sysfs attributes



On 1/18/2023 1:22 PM, Perry Yuan wrote:
> The amd-pstate driver supports switching working modes at runtime.
> Users can view and change modes by interacting with the "status" sysfs
> attribute.
> 
> 1) check driver mode:
> $ cat /sys/devices/system/cpu/amd-pstate/status
> 
> 2) switch mode:
> `# echo "passive" | sudo tee /sys/devices/system/cpu/amd-pstate/status`
> or
> `# echo "active" | sudo tee /sys/devices/system/cpu/amd-pstate/status`
> 
> Acked-by: Huang Rui <ray.huang@....com>
> Tested-by: Wyes Karny <wyes.karny@....com>
> Reviewed-by: Mario Limonciello <mario.limonciello@....com>
> Signed-off-by: Perry Yuan <perry.yuan@....com>
Reviewed-by: Wyes Karny <wyes.karny@....com>

> ---
>  Documentation/admin-guide/pm/amd-pstate.rst | 29 +++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst
> index b6aee69f564f..5304adf2fc2f 100644
> --- a/Documentation/admin-guide/pm/amd-pstate.rst
> +++ b/Documentation/admin-guide/pm/amd-pstate.rst
> @@ -339,6 +339,35 @@ processor must provide at least nominal performance requested and go higher if c
>  operating conditions allow.
>  
>  
> +User Space Interface in ``sysfs``
> +=================================
> +
> +Global Attributes
> +-----------------
> +
> +``amd-pstate`` exposes several global attributes (files) in ``sysfs`` to
> +control its functionality at the system level.  They are located in the
> +``/sys/devices/system/cpu/amd-pstate/`` directory and affect all CPUs.
> +
> +``status``
> +	Operation mode of the driver: "active", "passive" or "disable".
> +
> +	"active"
> +		The driver is functional and in the ``active mode``
> +
> +	"passive"
> +		The driver is functional and in the ``passive mode``
> +
> +	"disable"
> +		The driver is unregistered and not functional now.
> +
> +        This attribute can be written to in order to change the driver's
> +        operation mode or to unregister it.  The string written to it must be
> +        one of the possible values of it and, if successful, writing one of
> +        these values to the sysfs file will cause the driver to switch over
> +        to the operation mode represented by that string - or to be
> +        unregistered in the "disable" case.
> +
>  ``cpupower`` tool support for ``amd-pstate``
>  ===============================================
>  

-- 
Thanks & Regards,
Wyes