Monitor won't resume from sleep

I have an issue with my RX 5700 XT, one monitor connected via Displayport. If I leave the xfce display settings to not configure new devices when connected the screen will go blank after 5 minutes for a few seconds before coming back, will never go to sleep. If I enable profiles and to configure new displays it’ll go black and stay black but will never come back on, have to reboot.

journalctl shows the following messages when attempting to reinitialise the screen:

Sep 09 06:40:58 Manjaro kernel: [drm:dpcd_set_source_specific_data [amdgpu]] ERROR Error in DP aux read transaction, not writing source specific data
Sep 09 06:40:58 Manjaro kernel: [drm:retrieve_link_cap [amdgpu]] ERROR retrieve_link_cap: Read dpcd data failed.

The only solution is a full reboot, turning the screen off and on again still doesn’t work

Do you use amdgpu.dc=0 as kernel parameter ?
Have you seen this?

What kernel version are you booting now?

Currently booting 5.8.6-1, I haven’t set any kernel parameters. Checking through dmesg I can’t find any initialisation of Display Core so I assume it’s already disabled.

I’ve had a scan through that topic but I’m not seeing any powerplay errors on my end and I’ve only got the one monitor connected and in use.

I am having the exact same issue with Manjaro Xfce and kernel 5.10.15-1-MANJARO dated Feb. 10th 2021, on a computer with an Intel J4105 and no dedicated GPU.

My monitor (a projector in this case) used to wake correctly some weeks or months ago, but I don’t know what was the last working kernel, or if it is related to the kernel in my case.

Note that “Display power management” is set to “Blank after: never” in Xfce power settings, but the display still turns off after some inactivity and that is not the projector turning off (it’s still on, but loses its source and finds it again if I move the mouse, but the image doesn’t come up; again, this used to work and the hardware setup was not changed).

[Edit] Let me disambiguate that I am talking about screen blacking out without the system suspending here.