AMD Ryzen 5 3400G with Radeon Vega Graphics

Hi,

I was lucky to get the hands on a mini-ITX containing a
"AMD Ryzen 5 3400G with Radeon Vega Graphics".

FreeBSD-13 installed just fine and 4K HDMI output works too with AMDGPU. 
However I noticed some problems with a webcamd DVB-T receiver, that it 
had lots of dropouts I couldn't understand. When I looked closer at this 
it turns out that something was blocking the threads for longer amounts 
of time, up to 100 ms at random. After some debugging I eventually found:

sysctl machdep.idle

machdep.idle: acpi
machdep.idle_available: spin, mwait, hlt, acpi

And when I set it to:

sysctl machdep.idle=spin

The problems I saw vanished.

Anyone else having such experiences with Ryzen?

--HPS