https://bugs.freedesktop.org/show_bug.cgi?id=106303
--- Comment #3 from Mike bugs.freedesktop.org@pm.port0.org --- 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').