I'm on a RX 560.

I can confirm that with 4.17, behavior has quite changed a lot. I don't thi=
nk
it's buggy for Polaris, but not documented correctly.
To make values "stick" in pp_sclk_od, you have to boot with the p=
arameter
amdgpu.ppfeaturemask=3D0xffffffff.

Applying values higher than 1 in pp_sclk_od don't get reported back correct=
ly,
cat pp_sclk_od always returns 1.
However, entering values higher than 1 have an effect despite of this, as t=
hey
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 pstat=
es
in pp_od_clk_voltage (again unlocked with amdgpu.ppfeaturemask=3D0xffffffff=
).