linux-kernel - Re: [PATCH 0/4] amd_pstate: Add guided autonomous mode support

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Date:   Thu, 8 Dec 2022 12:48:41 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Wyes Karny <wyes.karny@....com>
Cc:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        Huang Rui <ray.huang@....com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Mario.Limonciello@....com, Perry.Yuan@....com,
        Ananth Narayan <ananth.narayan@....com>, gautham.shenoy@....com
Subject: Re: [PATCH 0/4] amd_pstate: Add guided autonomous mode support

On Wed, Dec 7, 2022 at 4:47 PM Wyes Karny <wyes.karny@....com> wrote:
>
> From ACPI spec[1] below 3 modes for CPPC can be defined:
> 1. Non autonomous: OS scaling governor specifies operating frequency/
>    performance level through `Desired Performance` register and PMFW
> follows that.
> 2. Guided autonomous: OS scaling governor specifies min and max
>    frequencies/ performance levels through `Minimum Performance` and
> `Maximum Performance` register, and PMFW can autonomously select an
> operating frequency in this range.
> 3. Fully autonomous: OS only hints (via EPP) to PMFW for the required
>    energy performance preference for the workload and PMFW autonomously
> scales the frequency.
>
> Currently (1) is supported by amd_pstate as passive mode, and (3) is
> implemented by EPP support[2]. This change is to support (2).

Well, can you guys please agree on priorities?  Like which one is more
important and so it should go in first?

At this point I'm not sure what the ordering assumptions with respect
to the EPP series are.

Also this submission is late for 6.2, so I will only regard it as 6.3
material on the condition the above gets clarified.  In the meantime,
please address review comments and consider resending after 6.2-rc1 is
out.

Thanks!