Power-saving/performance toggles for amdgpu

[Bastien Nocera]

On Fri, 2021-08-06 at 11:45 -0400, Alex Deucher wrote:
> You could set one of the profiles which sets more or less aggressive
> clocking, but you still get the advantages of the SMU being able to
> dynamically adjust the clocks.  If you manually force the clock to low
> or high, you end up forcing all clocks, even if a particular engine is
> not in use.  E.g., if you are not using video decode, there is no need
> to force the decoder clocks high as well.  Also, if the userspace tool
> dies for some reason, that will leave the clocks in the forced state.

This looks like the best option for that use case. I've documented it
here:
https://gitlab.freedesktop.org/hadess/power-profiles-daemon/-/issues/3#note_1021578

Thanks very much for your help!