I adjusted my pstates in "/sys/class/drm/card0/device/pp_od_clk_voltage" that
the GPU voltage should never be above 900 mV:

(...)
5:       1126Mhz        880 mV
6:       1180Mhz        890 mV
7:       1209Mhz        900 mV

And in normal 3D applications "watch -n 0.5  cat
/sys/kernel/debug/dri/0/amdgpu_pm_info" accordingly never reports more than 900
mV for VDDGFX.

But when I play a video in mpv with VAAPI/VDPAU, reported VDDGFX often jumps to
1100 mV, which clearly is undesired behavior. It sticks again to normal 900 mV
as soon as I disable hardware decoding.

Now the question is, if the reported voltage is correct (then adjusting
pp_od_clk_voltage has a bug) or if the real voltage is just reported wrong
(than information in amdgpu_pm_info would be wrong).

Happens with both 4.17rc2 and drm-next-4.18-wip.
GPU is RX 560.