Re: [PATCH] Documentation: Add documentation for new platform_profile sysfs attribute

[Elia Devito]

Hi to all,

In data martedì 27 ottobre 2020 17:42:19 CET, Mark Pearson ha scritto:
> From: Hans de Goede <hdegoede@xxxxxxxxxx>
> 
> 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 somei
> 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>
> ---
> Changes in V1:
>  - Moved from RFC to proposed patch
>  - Added cool profile as requested
>  - removed extra-profiles as no longer relevant
> 
>  .../ABI/testing/sysfs-platform_profile        | 66 +++++++++++++++++++
>  1 file changed, 66 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-platform_profile
> 
> diff --git a/Documentation/ABI/testing/sysfs-platform_profile
> b/Documentation/ABI/testing/sysfs-platform_profile new file mode 100644
> index 000000000000..240bd3d7532b
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-platform_profile
> @@ -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
> +consumption or towards performance (and higher power consumption and
> +thermals).
> +
> +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 are a rather meaningless way to describe platform-profiles
> +this API uses strings to describe the various profiles. To make sure that
> +userspace gets a consistent experience when using this API this API
> +document defines a fixed set of profile-names. Drivers *must* map their
> +internal profile representation/names onto this fixed set.
> +
> +If for some reason 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. Have very good reasons to do so.
> +2. Add the new profile-name to this document, so that future drivers which
> also +   have a similar problem can use the same name.
> +
> +What:		/sys/firmware/acpi/platform_profile_choices
> +Date:		October 2020
> +Contact:	Hans de Goede <hdegoede@xxxxxxxxxx>
> +Description:
> +		Reading this file gives a space separated list of profiles
> +		supported for this device.
> +
> +		Drivers must use the following standard profile-names:
> +
> +		low-power:		Emphasises low power consumption
> +		cool:			Emphasises cooler 
operation
> +		quiet:			Emphasises quieter 
operation
> +		balanced:		Balance between low power 
consumption
> +					and performance
> +		performance:		Emphasises performance 
(and may lead to
> +					higher temperatures and 
fan speeds)
> +
> +		Userspace may expect drivers to offer at least several 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.
> --
> 2.28.0

From my perspective now is perfect, thanks to all for the work.

Regards
Elia