I have two monitors connected to my AMD RX 6650 XT. Both monitors with DisplayPort. When I boot the PC with the monitors being off, the DisplayPort will not have any signal when I turn the monitors on after boot. The monitors complain about “no DP signal” and stay dark.
I can not recover from that situation. Regardless which keys I press, the monitors stay dark with no signal. I have to do a REISUB to reboot the PC to recover from that.
The problem does no occur if the main monitor is on HDMI. So it has to do with DisplayPort.
I wonder if anybody here experiences the same issue or might even have a solution for that.
You can try restarting X. For a standard case, Ctrl-Alt + F3 (give it 5 secs) and back.
No DM, or which DM? Look in DM logs and the journal.
I had a similar case today (with AMD integr).
I have LightDM with a setup script with debug output logging.
A VGA output (FullHD), which is treated/named as DM-1, and an HDMI monitor/output.
Boot with no power on the monitors. After power on, no signal to both.
After swapping TTYs and LightDM restart:
VGA (primary) had failsafe resolution (1024x768) with LightDM login box.
HDMI no signal.
After login to BSPWM session, my randr script provided successful/expected outputs.
In case this is related to kernels, I suggest testing a fallback image.
My main monitor is a Dell U2724DE. When I visited the Dell website to eventually find a hint if the problem is related to the monitor I found a firmware upgrade. Until that point I didnt even know that a monitor can receive a firmware upgrade.
Luckily Dell supports Linux to install firmware for their monitors. Unfortunately only Ubuntu. I installed the recommended Ubuntu 20.04 LTS on a USB drive, installed the Dell firmware software on top and did the upgrade. Firmware version went from M3T103 to M3T105. And my problem with the Displayport is gone!