Hi Michel,

Although I have not tested yet about mesa 17.2, I have noticed that this issue
only appears in the full or small sized window of Chromium. So, until now it
only has happened to Chromium; but this did not happen with my previous Nvidia
card, so I guess there is a relationship with my (new) RX 580.

I also noticed that it only happens, once in a while (every 15-30 minutes) and
when I active the Chromium window (bring it to the front). The garbled window
auto recovers after a short time, I guess 5 seconds.

Does this new information help to narrow the search?
Do you still want me to try with mesa 17.2?
Or do you have another plan of attack?

Since I am on a rolling release these are currently my key components:
* Kernel: 4.14.8
* Kernel driver: amdgpu
* X11: xf86-video-amdgpu 1.4.0
* Mesa: mesa 17.3.1
* Chromium: 63.0.3239.108
* chrome://gpu/ gives: <see attachment:
https://bugs.freedesktop.org/attachment.cgi?id=136453>

Maybe the chrome gpu page gives a clue?