That firmware kills kde / plasma5 and freezes the machine!

What I've done:
Copied the firmware files to /lib/firmware/amdgpu/
ran dracut to build new initrd
reboot

graphical login comes up
after logging in to kde plasma 5 the machine freezes

After a hard power of I logged into icewm.
That desktop came up. I opened an console. Ok. 
Started dolphin. Machine has frozen immediately. Even the clock in the desktop
toolbar stopped working.

Before starting dolphin I had a look at dmesg. I couldn't find any new error
messages. Unfortunately I do not have these messages around any more.
I also had a look at the /var/log/Xorg.<i>.log
There was no log written from the kde session freezing the machine.

Could you please test that firmware with a kde plasma 5 desktop? Please!