linux-kernel - RE: [PATCH v3 2/8] Documentation: amd-pstate: add EPP profiles introduction

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Date:   Sun, 13 Nov 2022 16:23:37 +0000
From:   "Yuan, Perry" <Perry.Yuan@....com>
To:     "Limonciello, Mario" <Mario.Limonciello@....com>,
        "rafael.j.wysocki@...el.com" <rafael.j.wysocki@...el.com>,
        "Huang, Ray" <Ray.Huang@....com>,
        "viresh.kumar@...aro.org" <viresh.kumar@...aro.org>
CC:     "Sharma, Deepak" <Deepak.Sharma@....com>,
        "Fontenot, Nathan" <Nathan.Fontenot@....com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Huang, Shimmer" <Shimmer.Huang@....com>,
        "Du, Xiaojian" <Xiaojian.Du@....com>,
        "Meng, Li (Jassmine)" <Li.Meng@....com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 2/8] Documentation: amd-pstate: add EPP profiles
 introduction

[AMD Official Use Only - General]

Hi Mario

> -----Original Message-----
> From: Limonciello, Mario <Mario.Limonciello@....com>
> Sent: Tuesday, November 8, 2022 2:34 AM
> To: Yuan, Perry <Perry.Yuan@....com>; rafael.j.wysocki@...el.com; Huang,
> Ray <Ray.Huang@....com>; viresh.kumar@...aro.org
> Cc: Sharma, Deepak <Deepak.Sharma@....com>; Fontenot, Nathan
> <Nathan.Fontenot@....com>; Deucher, Alexander
> <Alexander.Deucher@....com>; Huang, Shimmer
> <Shimmer.Huang@....com>; Du, Xiaojian <Xiaojian.Du@....com>; Meng,
> Li (Jassmine) <Li.Meng@....com>; linux-pm@...r.kernel.org; linux-
> kernel@...r.kernel.org
> Subject: Re: [PATCH v3 2/8] Documentation: amd-pstate: add EPP profiles
> introduction
> 
> On 11/7/2022 11:56, Perry Yuan wrote:
> > The patch add AMD pstate EPP feature introduction and what EPP
> > preference supported for AMD processors.
> >
> > User can get supported list from
> > energy_performance_available_preferences attribute file, or update
> > current profile to energy_performance_preference file
> >
> > 1) See all EPP profiles
> > $ sudo cat
> >
> /sys/devices/system/cpu/cpu0/cpufreq/energy_performance_available_pref
> > erences default performance balance_performance balance_power power
> >
> > 2) Check current EPP profile
> > $ sudo cat
> > /sys/devices/system/cpu/cpu0/cpufreq/energy_performance_preference
> > performance
> >
> > 3) Set new EPP profile
> > $ sudo bash -c "echo power >
> /sys/devices/system/cpu/cpu0/cpufreq/energy_performance_preference"
> >
> > Signed-off-by: Perry Yuan <Perry.Yuan@....com>
> > ---
> >   Documentation/admin-guide/pm/amd-pstate.rst | 19
> +++++++++++++++++++
> >   1 file changed, 19 insertions(+)
> >
> > diff --git a/Documentation/admin-guide/pm/amd-pstate.rst
> > b/Documentation/admin-guide/pm/amd-pstate.rst
> > index 8f3d30c5a0d8..78c6525d5a49 100644
> > --- a/Documentation/admin-guide/pm/amd-pstate.rst
> > +++ b/Documentation/admin-guide/pm/amd-pstate.rst
> > @@ -262,6 +262,25 @@ lowest non-linear performance in `AMD CPPC
> Performance Capability
> >   <perf_cap_>`_.)
> >   This attribute is read-only.
> >   > +``energy_performance_available_preferences``
> > +
> > +All the supported EPP preference could be selected, List of the
> > +strings that can be set to the ``energy_performance_preference``
> > +attribute those different profiles represent different energy vs
> > +efficiency hints provided to low-level firmware however, the
> > +``default`` represents the epp value is set by platform firmware This
> > +attribute is read-only.
> 
> My proposal at rewording it.
> 
> A list of all the supported EPP preferences that could be used for
> ``energy_performance_preference` on this system.
> These profiles represent different hints that are provided to the low-level
> firmware about the user's desired energy vs efficiency tradeoff.  ``default``
> represents the epp value is set by platform firmware. This attribute is read-
> only.

Make sense.
Fixed in V4 as you suggested.

> 
> 
> > +
> > +``energy_performance_preference``
> > +
> > +The current energy performance preference can be read from this
> attribute.
> > +and user can change current preference according to energy or
> > +performance needs Please get all support profiles list from
> > +``energy_performance_available_preferences`` attribute, all the
> > +profiles are integer values defined between 0 to 255 when EPP feature
> > +is enabled by platform firmware, if EPP feature is disabled, driver
> > +will ignore the written value This attribute is read-write.
> > +
> >   Other performance and frequency values can be read back from
> >   ``/sys/devices/system/cpu/cpuX/acpi_cppc/``, see :ref:`cppc_sysfs`.
> >