https://bugzilla.kernel.org/show_bug.cgi?id=60523
--- Comment #18 from Tobias Droste tdroste@gmx.de --- Doesn't help here.
But I can confirm that it works as soon as dpms is active and dpm switches to power level 0. It stays at power level 0 after the monitors are active again and I can echo things to power_dpm_force_performance_level. But as soon as it goes back to power level 2 it stays there and echoing to power_dpm_force_performance_level fails again.