Re: [RFC v4 2/4] platform/x86/amd: dptc: Add AMD DPTCi driver

[Mario Limonciello <mario.limonciello@amd.com>]

>>
>> So please; do not make assumptions based on a lack of hard data.
>> If you don't have data for multiple years of a system or multiple chips
>> in the system, leave it off your quirk list.  They can always be added
>> later when the data is available.
> 
> Specifically for GPD, the userspace implementation has been tested on
> all generations. It is fine to choose a (lower) limit that works on
> all of them. The thermals did not change between generations.
> Saturation above 20W means that there is little difference between
> 22W, 25W, 28W, 30W, etc. If there is doubt, going lower is fine. Even
> if one device can do 5W more it does not matter (but the chassis,
> battery, and cooler are exactly the same; only the board was revised
> for the new SoC).
> 
> 8-20W is the sweet spot for these APUs. 8W and 15W are sane for
> low-power/balanced. The only question is how close to 30W should be
> the maximum and where performance should point to. This version does
> 25W for performance. 20W might be better for daily use until AC/DC
> detection.
> 
> We do not need to complicate things. All this driver needs to do is
> expose a slider from 4-30W. This covers 6800-HX370 for all vendors and
> matches user expectation. AI Max will need further research as I do
> not have a lot of data on its performance curve. Ayaneo had some drops
> between 2022-2023 that had lower TDP limits, but there is less than 1k
> units in existence.

User expectation and reality aren't necessarily the same.

Performance is tied to a thermal design.  A user might want to run a 
handheld at the max performance, but max performance is not purely a 
function of the APU.

It's a function of the APU + cooling solution + power distribution.

That's why I have been saying there need to be different values for 
different parts, and you can't make assumptions year to year.

Even if the external chassis plastics are identical, a different fan or 
heatpipe might be used and those are non-trivial impacts.

The values used should be calculated by performance measurements of the 
entire solution in a thermal chamber.

I know you're not going to be able to do that, but that's what 
manufacturers /should/ be doing.