Re: [PATCH v5 1/3] Documentation: Add documentation for new platform_profile sysfs attribute

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Hi,

On 12/2/20 6:11 PM, Mark Pearson wrote:
> On modern systems the platform performance, temperature, fan and other
> hardware related characteristics are often dynamically configurable. The
> profile is often automatically adjusted to the load by some
> automatic-mechanism (which may very well live outside the kernel).
> 
> These auto platform-adjustment mechanisms often can be configured with
> one of several 'platform-profiles', with either a bias towards low-power
> consumption or towards performance (and higher power consumption and
> thermals).
> 
> Introduce a new platform_profile sysfs API which offers a generic API for
> selecting the performance-profile of these automatic-mechanisms.
> 
> Co-developed-by: Mark Pearson <markpearson@xxxxxxxxxx>
> Signed-off-by: Mark Pearson <markpearson@xxxxxxxxxx>
> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>

Thank you, patches 1 and 2 look good to me now, you may add my:

Reviewed-by: Hans de Goede <hdegoede@xxxxxxxxxx>

To patch 2 (since I'm co-author of patch 1 it would be a bit weird
to add it there too).

Rafael, it would be great if you pick up patches 1 and 2 for merging
into 5.11 (assuming that you agree that they are ready) then I will merge
patch 3 once 5.11-rc1 is out.

Regards,

Hans



> ---
> Changes in v2:
>  - updated to rst format
> Changes in v3, v4 & v5:
>  - version bump along with rest of patch series
> 
>  .../ABI/testing/sysfs-platform_profile.rst    | 66 +++++++++++++++++++
>  1 file changed, 66 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-platform_profile.rst
> 
> diff --git a/Documentation/ABI/testing/sysfs-platform_profile.rst b/Documentation/ABI/testing/sysfs-platform_profile.rst
> new file mode 100644
> index 000000000000..5f7b2a94409b
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-platform_profile.rst
> @@ -0,0 +1,66 @@
> +=======================================================================
> + Platform Profile Selection (e.g. /sys/firmware/acpi/platform_profile)
> +=======================================================================
> +
> +
> +On modern systems the platform performance, temperature, fan and other
> +hardware related characteristics are often dynamically configurable. The
> +profile is often automatically adjusted to the load by some
> +automatic mechanism (which may very well live outside the kernel).
> +
> +These auto platform adjustment mechanisms often can be configured with
> +one of several platform profiles, with either a bias towards low power
> +operation or towards performance.
> +
> +The purpose of the platform_profile attribute is to offer a generic sysfs
> +API for selecting the platform profile of these automatic mechanisms.
> +
> +Note that this API is only for selecting the platform profile, it is
> +NOT a goal of this API to allow monitoring the resulting performance
> +characteristics. Monitoring performance is best done with device/vendor
> +specific tools such as e.g. turbostat.
> +
> +Specifically when selecting a high performance profile the actual achieved
> +performance may be limited by various factors such as: the heat generated
> +by other components, room temperature, free air flow at the bottom of a
> +laptop, etc. It is explicitly NOT a goal of this API to let userspace know
> +about any sub-optimal conditions which are impeding reaching the requested
> +performance level.
> +
> +Since numbers on their own cannot represent the multiple variables that a
> +profile will adjust (power consumption, heat generation, etc) this API
> +uses strings to describe the various profiles. To make sure that userspace
> +gets a consistent experience this API document defines a fixed set of
> +profile names. Drivers *must* map their internal profile representation
> +onto this fixed set.
> +
> +
> +If there is no good match when mapping then a new profile name may be
> +added. Drivers which wish to introduce new profile names must:
> +
> + 1. Explain why the existing profile names canot be used.
> + 2. Add the new profile name, along with a clear description of the
> +    expected behaviour, to the documentation.
> +
> +:What:        /sys/firmware/acpi/platform_profile_choices
> +:Date:        October 2020
> +:Contact:     Hans de Goede <hdegoede@xxxxxxxxxx>
> +:Description: This file contains a space-separated list of profiles supported for this device.
> +
> +              Drivers must use the following standard profile-names::
> +
> +         		 low-power:     Low power consumption
> +         		 cool:          Cooler operation
> +		         quiet:         Quieter operation
> +		         balanced:      Balance between low power consumption and performance
> +		         performance:   High performance operation
> +
> +              Userspace may expect drivers to offer more than one of these
> +              standard profile names.
> +
> +:What:        /sys/firmware/acpi/platform_profile
> +:Date:        October 2020
> +:Contact:     Hans de Goede <hdegoede@xxxxxxxxxx>
> +:Description: Reading this file gives the current selected profile for this
> +              device. Writing this file with one of the strings from
> +              available_profiles changes the profile to the new value.
> 




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