(In reply to Andy Furniss from comment #15)
> You should be able to do this eg. on my R9 285
> 
> echo manual > /sys/class/drm/card0/device/power_dpm_force_performance_level
> 
> cat /sys/class/drm/card0/device/pp_dpm_mclk 
> 0: 150Mhz *
> 1: 1375Mhz 
> 
> echo 1 > /sys/class/drm/card0/device/pp_dpm_mclk
> 
> cat /sys/class/drm/card0/device/pp_dpm_mclk 
> 0: 150Mhz 
> 1: 1375Mhz *
> 
> Though it will undo if you change modes or go into DPMS.

I can't apply "manual" mode: "invalid argument". I can't see pp_dpm_mclk clocks
either.