sucotronic

Wow, that was a very helpful answer, thanks a lot!!
With that info I can just blacklist that modules (anyway, I'm not interested in using the ADC functionality of the A20 :P) and now the system shows proper low cpu usage:
root@lime:~# cat /etc/modprobe.d/fix.conf blacklist sun4i_gpadc sun4i_gpadc_iio root@lime:~# ps auxk -cpu | head USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 1 0.0 0.5 26932 5332 ? Ss 00:07 0:07 /sbin/init root 2 0.0 0.0 0 0 ? S 00:07 0:00 [kthreadd] root 3 0.0 0.0 0 0 ? I< 00:07 0:00 [rcu_gp] root 4 0.0 0.0 0 0 ? I< 00:07 0:00 [rcu_par_gp] root 8 0.0 0.0 0 0 ? I< 00:07 0:00 [mm_percpu_wq] root 9 0.0 0.0 0 0 ? S 00:07 0:00 [ksoftirqd/0] root 10 0.0 0.0 0 0 ? I 00:07 0:23 [rcu_sched] root 11 0.0 0.0 0 0 ? I 00:07 0:00 [rcu_bh] root 12 0.0 0.0 0 0 ? S 00:07 0:00 [migration/0]  

i think it could be a generic a20 problem - maybe have a look at:
 
https://forum.armbian.com/topic/7575-k-worker-problem-on-a20-based-boards/
https://forum.armbian.com/topic/14282-headless-systems-and-sun4i_drm_hdmi-a10a20/
https://superuser.com/questions/1515001/debian-10-buster-on-cubietruck-with-bug-in-sun4i-drm-hdmi
 
best wishes - hexdump