Comment 32 for bug 1849084

P.B. I tried to verify your observation. Without luck. First I generated a Windows-10 bootable USB drive and managed to install and run the "AMD Driver Auto-detect tool". On Windows it was successful to set the computer into standby and resume. Then I've done a warm-start of the computer an booted into Linux. Now I was able to set the machine into standby and back to resume successfully.

The next experiment was to do a power down reset and try the standby/resume with Linux again. It stopped with a blank black screen with backlight switched on. After a warm start (Alt-SysReq-B) all subsequent standby/resume cycles worked perfectly.

My guess is that after a warm start some GPU register settings remain untouched causing success of the resume. Or in other words, the initial setup of the GPU is missing something which is done with the first (unsuccessful) standby/resume after power up.

My ubuntu kernel version is meanwhile 5.3.0-46-generic.