Comment # 1 on bug 101528 from Alexander Tsoy

Same problem with TONGA. When GPU is idle, mclk goes to its maximum. This is
easily reproducible: just turn off the monitor. I noticed this issue after
upgrade from 4.9.x kernels to 4.11.7. Maybe I'll check the mainline kernel
later and/or bisect.

# cat /sys/class/drm/card0/device/pp_dpm_mclk
0: 150Mhz
1: 300Mhz
2: 700Mhz
3: 1450Mhz *
# sensors amdgpu-\*
amdgpu-pci-0100
Adapter: PCI adapter
fan1:        2025 RPM
temp1:        +47.0°C  (crit =  +0.0°C, hyst =  +0.0°C)