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

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Message-ID: <09674d15-d639-4cb3-837a-9575f0028a76@kernel.org>
Date: Sat, 1 Mar 2025 07:52:15 -0600
From: Mario Limonciello <superm1@...nel.org>
To: Antheas Kapenekakis <lkml@...heas.dev>
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>, Mark Pearson
 <mpearson-lenovo@...ebb.ca>,
 "open list:AMD PMF DRIVER" <platform-driver-x86@...r.kernel.org>,
 open list <linux-kernel@...r.kernel.org>,
 "open list:ACPI" <linux-acpi@...r.kernel.org>,
 "Derek J . Clark" <derekjohn.clark@...il.com>, me@...egospodneti.ch,
 Denis Benato <benato.denis96@...il.com>,
 Mario Limonciello <mario.limonciello@....com>, Armin Wolf <W_Armin@....de>
Subject: Re: [PATCH 1/3] ACPI: platform_profile: Add support for hidden
 choices

>>> 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.

> so there is actually 0 reason for
> generic power handlers to move to the new API. Just extra work. So
> lets make sure the legacy endpoint works properly for the foreseeable
> future.
> 
> Also, when power handlers start moving to the new interface, they will
> hardcode choices based on the name. As they should. TDP needs to be
> customized per device/manufacturer. So moving handlers between
> low-power and quiet will not be possible.
> 
> @Mario: I do not have a device with an amd-pmf integration. All of
> mine have stub handlers. I would expect that a properly configured pmf
> handler for e.g., Asus would do the same as the armoury interface, so
> that users do not have to rely to vendor software on WIndows. Then
> power profiles would be synced between windows and armoury. In that
> case, we have a problem of setting the power mode twice. What would be
> the mitigation for something like that?
> 
> Antheas

"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.

If we really end up with a situation that vendor interface and PMF do 
the same thing we can cross that bridge then.