Comment # 4 on bug 106177 from tempel.julian@gmail.com

I'm on a RX 560.

I can confirm that with 4.17, behavior has quite changed a lot. I don't think
it's buggy for Polaris, but not documented correctly.
To make values "stick" in pp_sclk_od, you have to boot with the parameter
amdgpu.ppfeaturemask=0xffffffff.

Applying values higher than 1 in pp_sclk_od don't get reported back correctly,
cat pp_sclk_od always returns 1.
However, entering values higher than 1 have an effect despite of this, as they
allow using of higher clocks in pp_od_clk_voltage.

And unlike with 4.16, higher values than 0 in pp_sclk_od don't automatically
lead to higher clocks. Additionally it is also required to change the pstates
in pp_od_clk_voltage (again unlocked with amdgpu.ppfeaturemask=0xffffffff).