GPU and memory clock are still the same while idle and under heavy load.

gentoo niko # cat /sys/kernel/debug/dri/0/radeon_pm_info
state: PM_STATE_ACTIVE
default engine clock: 776000 kHz
current engine clock: 769500 kHz
default memory clock: 1126000 kHz
current memory clock: 1125000 kHz
gentoo niko # sleep 60 && cat /sys/kernel/debug/dri/0/radeon_pm_info
state: PM_STATE_ACTIVE
default engine clock: 776000 kHz
current engine clock: 769500 kHz
default memory clock: 1126000 kHz
current memory clock: 1125000 kHz