linux-kernel - Re: [PATCH 1/3] ACPI: platform_profile: Add support for hidden choices

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Message-Id: <299cc6b8-a43b-4bc0-a7dd-ce3bde5f1a48@app.fastmail.com>
Date: Sat, 01 Mar 2025 22:23:09 -0500
From: "Mark Pearson" <mpearson-lenovo@...ebb.ca>
To: "Antheas Kapenekakis" <lkml@...heas.dev>,
 "Mario Limonciello" <superm1@...nel.org>
Cc: "Kurt Borja" <kuurtb@...il.com>,
 "Shyam Sundar S K" <Shyam-sundar.S-k@....com>,
 "Rafael J. Wysocki" <rafael@...nel.org>,
 "Hans de Goede" <hdegoede@...hat.com>,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
 "Luke D . Jones" <luke@...nes.dev>,
 "platform-driver-x86@...r.kernel.org" <platform-driver-x86@...r.kernel.org>,
 "open list" <linux-kernel@...r.kernel.org>,
 "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
 "Derek J . Clark" <derekjohn.clark@...il.com>, me@...egospodneti.ch,
 "Denis Benato" <benato.denis96@...il.com>,
 "Limonciello, Mario" <mario.limonciello@....com>,
 "Armin Wolf" <W_Armin@....de>
Subject: Re: [PATCH 1/3] ACPI: platform_profile: Add support for hidden choices



On Sat, Mar 1, 2025, at 11:15 AM, Antheas Kapenekakis wrote:
> On Sat, 1 Mar 2025 at 17:04, Mario Limonciello <superm1@...nel.org> wrote:
>>
>>
>>
>> On 3/1/25 08:06, Antheas Kapenekakis wrote:
>> > On Sat, 1 Mar 2025 at 14:52, Mario Limonciello <superm1@...nel.org> wrote:
>> >>
>> >>>>> Let me know what you think!
>> >>>>
>> >>>> I don't really like that profiles can get out of sync, this is asking
>> >>>> for a non-deterministic behavior that can be difficult to diagnose
>> >>>> issues and also difficult for userspace to work with.
>> >>>
>> >>> I agree with Mario here. Imagine two drivers, one with low-power and
>> >>> one with quiet. They both begin at performance.
>> >>>
>> >>> Then, userspace software gets confused (incl. ppd) and sets firmware
>> >>> profile to low-power. The latter gets left in performance, causing
>> >>> excess drain.
>> >>>
>> >>> I do not believe the legacy interface should be deprecated. Right now,
>> >>> amd-pmf is a NOOP in most devices
>> >>
>> >> "Most" devices is not accurate.  There are a lot of devices that it does
>> >> enable.  In the gaming space right now it's often behaving as a no-op.
>> >
>> > That would be a fair description. Can you give some examples of
>> > devices that use the interface? Devices with and without vendor
>> > software.
>>
>> Off hand the Framework 13 and 16 AMD both use PMF exclusively.  So do a
>> bunch of HP commercial laptops.
>
> I will ask Kyle to check it out.
>
>> Mark can keep me honest, but I want to say the Strix Thinkpad laptops
>> have both PMF and vendor interface (thinkpad-acpi).
>
> Hm, yeah that would be interesting to hear about
>

Yep, support both.

>>   >>
>> >> "Power mode" is a concept, it doesn't just apply to configuring sPPT and
>> >> fPPT.  I envisage that a vendor that actively uses PMF and their own
>> >> interface would be changing different things by the different interfaces.
>> >>
>> >> For "example" PMF may reconfigure sPPT, fPPT, STT and STAPM but their
>> >> driver may notify their EC to change a fan curve.
>> >
>> > No. If PMF changes these values it also needs to change the fan curve
>> > itself via the BIOS notification. Doing otherwise would lead to
>> > situations where users do not install the vendor driver and cook their
>> > device.
>>
>> Fan curves are just that; curves.  They just control how quickly fans
>> ramp up not whether or not they "work".
>
> The APU reaches a similar temperature (Tctl) across a wide TDP range,
> so temperature cannot be used on its own to determine fan speed.
> Manufacturers that provide different fan curves depending on the TDP
> mode usually cap the maximum fan speed on low TDPs. So you can get
> funny situations where the device is set to 30W, but the fan runs as
> if its using 10W leading to thermal soaking. So it is very important
> for those to be inline.
>
>> But in any case; that's a firmware issue not a platform profile design
>> issue.
>
> It would be a hypothetical scenario. I do not expect such a device to exist.
>
>> > So I expect that when PMF controls things it controls
>> > everything. I would expect if vendors fallback to the pmf firmware
>> > notifications while also providing vendor software there would be some
>> > synergy between them, such as changing which fan preset is selected by
>> > the PMF interface.
>> >
>>
>> I can't control what vendors do; it's their decision how to manage their
>> systems.  All I can do is provide infrastructure to help.
>
> This was more of my intuition of how I would expect amd-pmf
> integration to be done in Windows where one of the drivers might be
> missing.
>
> Since only thinkpads are expected to do both, perhaps Mark can check
> out how they work. I have a thinkpad that is 11th gen intel.
>

I'll do some checking next week (away this weekend). Mario will ping you offline for best testing to do.

Mark