Failure to use 3840x2160 30hz with Intel 620 chipset

[Pierre Couderc <pierre@couderc.eu>]

I have a problem when trying a 4K display with Acer swift5. They say 
that 3840x2160 30hz is supported...

When I try (under bullseye) :

gtf  3840 2160 30

xrandr --newmode  "3840x2160_30.00"  339.57  3840 4080 4496 5152 2160 
2161 2164 2197  -HSync +Vsync
xrandr --addmode HDMI-1   3840x2160_30.00
xrandr --output HDMI-1 --mode "3840x2160_30.00"

the PC crashes (all is black, need to power off).

Did anyone success in similar case..?

Thnaks for any help.

PC