My laptop (core m5-6y54) starts flickering after returning from Suspend (to RAM) or other commands touching the video driver (xrandr, powertop --calibrate, ...)

From kernel (tested with up to 5.7) I get the message:

[drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe A FIFO underrun

I added a bug with more details here:

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1872760

but guys from Ubuntu seems not able to help (as it is an upstream bug) !?

This happend not in older kernels, but these have the problem not to go in power save states. So I think the fix of that 

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1863489

causes this regression.

Hope someone can help. For a  laptop it is better to have both - standby and power saving. Thank you.

Arno