Created attachment 121103 [details]
Screenshot of failure

Sometimes after the deactivation of the screensaver or also on bootup the
screen shows flickering noise and a duplicated screen image. (Attached there is
the used test image and a screenshot of the failure image). 

We tested on various kernel versions, latest kernel tested was 4.4.0. We run a
customized debian image. 

Further investigations showed, that in the failure scenario the measured clk
frequency was only 25MHz but it should be 35MHz. 

We also tried to deactivate dpms completly (radeon.dpm=0 in kernel parameters)
and also turned the dpms off in the screensaver, but we still sometimes
encounter the problem after a reboot. 

Attached you will find a dmesg output with drm.debug=0xf activated. 

We use a Radeon PALM on a AMD G-T40E 2x1GHz