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

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

On Thu, Sep 26, 2024, at 2:14 PM, Mario Limonciello wrote:
> On 9/26/2024 08:58, Mark Pearson wrote:
>> 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.
>
> JFYI we're going to do something really similar in amdgpu when people 
> have enabled overclocking.  That's part of the inspiration for this RFC.
>
> https://lore.kernel.org/amd-gfx/CADnq5_M+vxGV6y8oEQHC+-CcqV-vW9ND4SsRHqHKbwR_b0iJ9g@mail.gmail.com/T/#m1d69399c3e799ea1ef2014a27fd6e555f9e70ba0
>

Nice :)

>> 
>> 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).
>
> Well the RFC was just to show it for the AMD PMF driver, but I think 
> that thinkpad_acpi, asus_armoury etc could all potentially implement the 
> 'custom' bit too if they offer an ACPI-WMI interface to similar settings.
>
>> 
>> 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
>
> I guess what you're proposing is that multiple drivers register as 
> profile handlers and they might not all export the same features.
>
> If we did something like this we could instead have the core call 
> callbacks for all platform profile handlers.  We could also drop a pile 
> of quirks from amd-pmf where there are some ASUS systems that advertise 
> SPS in in the PMF framework and also asus-wmi provides it.
>
> If I'm following you right, I generally like this idea.

Yep - that was the idea.

This feels like a step towards giving more control to power users - whilst keeping the basic simple for regular folk.

I can imagine utilities that would use this to enable specific configurations, via the custom profile mode, for many different scenario's; whilst still allowing a user to get back to the tested and vendor approved setting if things go badly.

Mark