(In reply to iuno from comment #55)
> Make sure to raise the DC clock above the default value, e.g. to 625 MHz
> (value 62500)
> 
> If you use amdgpu: in amdgpu_atombios.c adev->clock.default_dispclk
> If you use radeon: in atombios_crtc.c rdev->clock.default_dispclk
> 
> That should fix the broken image. To fix flickering, set mclk to high (echo
> 1 > /sys/class/drm/card0/device/power_dpm_force_performance_level)

Confirming that this fixed the issue! MG279Q, r9 290 with amdgpu. Didn't have
to touch the mclk.