Issue with laptop using ATI Radeon RX 580.
 

Working with an HP laptop containing a Radeon RX 580 video card, I encountered an issue wherein the screen would not turn back on when the laptop lid is closed and reopened. I have opened a bug report with the kernel folks. I can work around the issue by blacklisting the amdgpu video driver. I am currently running Linux 4.19.5. I will update this thread with any new developments.

I suspect that the new amd display code (in amdgpu) loads upon booting your machine.
It has various problems. One of them is when /sbin/setterm is switching on consoleblanking
in /etc/rc.d/rc.M. I changed it to /sbin/setterm -blank 0. Everything seem to work okay with
my AMD Vega64 now. Before the system chrashed whenever the console or desktop blanked the monitor.
I also could not reboot or shut down normally, it would stay on until i pressed reset.
This might be the same problem as yours.

I'm not sure if the new display code is even needed for your card.
If it's not, you can just pass amdgpu.dc=0 to the kernel and everything should work just fine.

setterm -blank 0 didn't work. Nor does dc=0.

try consoleblank=0

It didn't work.

A little more information might be very helpful...
Output of /sbin/lspci -v and dmesg is a start.

Regardless of hardware; I have tested this on three different machines with three
different graphics cards, I get the same amdgpu warnings and chrash trace from the
new display code as you if I let line 25 in rc.M run.

If anyone has experienced this issue, please add yourself to the bug report via the link above.

Update: with the kernel built from drm-next-4.21-wip, loading the amdgpu module with dc=1, and the latest kernel firmware from git, the display wakes up on resume. I'll test this for a few days: if it still works, I'll mark this as solved.

Just tried with 4.19.11: does not work. When loading the module, the screen goes blank.

On further thought, I will wait until a fix appears in a released kernel before I mark this as solved.

Turns out passing dc=1 to the module is not necessary.

The screen wakes up on resume with 4.20.2. Marking this solved.