Comment # 3 on bug 106303 from Mike

Also noted, that
/sys/class/drm/card0/device/pp_num_states is limited to:
states: 2
0 boot
1 performance

And power_dpm_state is always 'performance' regarless of values echoed to
power_dpm_force_performance_level (tried 'low', 'auto', 'balanced' and 'boot').