Re: [RFC 0/2] "custom" ACPI platform profile support

["Mark Pearson" <mpearson-lenovo@squebb.ca>]

Thanks Mario,

On Wed, Sep 25, 2024, at 10:59 PM, Mario Limonciello wrote:
> From: Mario Limonciello <mario.limonciello@amd.com>
>
> There are two major ways to tune platform performance in Linux:
>  * ACPI platform profile
>  * Manually tuning APU performance
>
> Changing the ACPI platform profile is a "one stop shop" to change
> performance limits and fan curves all at the same time.
>
> On AMD systems the manual tuning methods typically involve changing
> values of settings such as fPPT, sPPT or SPL.
>
> The problem with changing these settings manually is that the definition
> of the ACPI platform profile if supported by the hardware is no longer
> accurate.  At best this can cause misrepresenting the state of the
> platform to userspace and at worst can cause the state machine into an
> invalid state.
>
> The existence and continued development of projects such as ryzenadj which
> manipulate debugging interfaces show there is a demand for manually tuning
> performance.
>
> Furthermore some systems (such as ASUS and Lenovo handhelds) offer an
> ACPI-WMI interface for changing these settings. If using anything outside
> that WMI interface the state will be wrong.  If using that WMI interface
> the platform profile will be wrong.
>
> This series introduces a "custom" ACPI platform profile and adds support
> for the AMD PMF driver to use it when a user has enabled manual
> adjustments.
>
> If agreeable a similar change should be made to asus-armoury and any other
> drivers that export the ability to change these settings but also a
> platform profile.
>

As someone who supports customers on Lenovo devices and hits the occasional situation where a user has made strange tweaks to different power related settings, and then complains about power or thermal issues - I love the idea that it can be made clear the system has been 'adjusted' in a non standard way. I can also see why users would want interfaces to do those changes.

Some suggestions:

I'm wondering if we can make it so a driver can register only a 'custom' profile as an extra profile handler?

The thinking here is the custom setting in this series is implemented for the amd sps driver, and therefore on a regular Lenovo laptop wouldn't be used, as the thinkpad_acpi driver will grab the profile slot, Users on Lenovo systems aren't going to be able to get at these extra tweaks (unless they unload thinkpad_acpi, which has other side effects).

If the sps driver can offer a custom mode, separately from thinkpad_acpi, then users can tweak settings to their hearts content but get back to regular mode when done.

I also think there needs to be a way that when you switch from custom back to a 'regular' profile that it would do a clean up of anything tweaked. e.g. when switching away from custom the ppd driver should call a 'custom mode cleanup' function, so things can be undone and returned to how they were when it was started.

Mark