Multiple monitor issue on Wayland

Inxsible · 2023-09-18 01:58:41

Hello,

I recently moved my desktops from a HP Prodesk 600 to a HP t730 thin client (as I want to repurpose my Prodesk as a low power Proxmox server) and now my multiple displays don't work as expected.

The Prodesk has: DP-1, DP-2 and VGA outputs. I had connected 3 monitors to it and used it without any issues.

Since moving to the t730 thin client which has 4 DP outputs (although I have only connected 2 monitors this time around) I have a weird problem. If I poweroff my monitors using the power switch on the monitors, then upon switching the monitors back on again, I get just a gray screen. No mouse, no desktop windows and even the swaylock doesn't display the keypresses from the keyboard. However, if I switch the monitors off again, but only switch ONE of them on again, I am able to get to the desktop and the computer works flawlessly with ONE monitor. However, once it works and if I switch on the 2nd monitor again, I get gray screens on both monitors again and I have to then switch them both off again and only start ONE of them. This is NOT after the computer goes to sleep/hibernate or anything. It happens even after I reboot and immediately switch off the monitors and switch them back on 5 seconds later. Once in a while, if I disconnect the DP cable and reconnect it, both monitors will work, but this is not consistent and most times even disconnect /reconnect of the DP cable doesn't enable the 2nd monitor to work.

I read a few threads related to kernel bug with 2 DP monitors, but I tested that and upon reboot both the monitors work just fine. It's only when I power switch them off and then turn them on again, that the issue occurs. I will also test this out by keeping the monitors powered but waiting for the swaylock to timeout and set the dpms off and see if it behaves differently.

I am using Wayland and so I only have mesa installed and am NOT using the amdgpu drivers. (The Prodesk was an Intel based computer - so I thought it might be a video driver issue, but it doesn't seem like it)

I read some related threads like : https://bbs.archlinux.org/viewtopic.php?id=260159 but that seems to be an issue with X11 and not wayland.

I am unable to understand why this happens. Any pointers?

Last edited by Inxsible (2023-09-18 02:07:38)

Inxsible · 2023-09-18 15:29:27

I tested this by setting a very low value for the timeout for swayidle but the monitor was responsive and took in my password and brought back the desktop. Even manually setting dpms off and then setting it back on (blindly) works as expected. So I don't think this is an issue with the dpms.
Here's my swayidle config just in case:

 exec swayidle -w \
          timeout 900 'swaylock -f -c 000000' \
          timeout 1200 'swaymsg "output * dpms off"' \
               resume 'swaymsg "output * dpms on"' \
          before-sleep 'swaylock -f -c 000000'

Only when I turn the monitor's power switch off, the problem arises. I used the same monitors with the Prodesk and didn't have any issues. For testing, I reconnected the Prodesk to the same monitors and had no issues. It seems that the thin client kills the signal to the DP cables if the monitors are switched off and for whatever reason cannot reset back when the monitors are switched back on.

If I connect only 1 monitor to the HP thin client, I have ZERO issues and everything works as expected, even when power switching the monitor off and then on again.

Any help here please??

Skidout · 2023-09-19 02:34:49

The only thing I can think of is to try using the linux-drm-tip-git kernel and see if that fixes it, but it seems like it might actually be an issue with Sway.

Inxsible · 2023-09-19 14:23:31

Skidout wrote:

The only thing I can think of is to try using the linux-drm-tip-git kernel and see if that fixes it, but it seems like it might actually be an issue with Sway.

It wouldn't work with the Prodesk either in that case. It's probably a combination of a few things in my opinion. amd vs intel, dpms, sway.

Right now I have resorted to just using a single monitor, even though I have 3 sitting on my workdesk.

Lone_Wolf · 2023-09-19 14:37:17

Do your monitors support DisplayPort Multi Stream Transport aka MST aka daisy-chaining ?

If so, make sure it is set to disabled on every monitor except ones that are using it.

Inxsible · 2023-09-27 01:05:55

Lone_Wolf wrote:

Do your monitors support DisplayPort Multi Stream Transport aka MST aka daisy-chaining ?
If so, make sure it is set to disabled on every monitor except ones that are using it.

No, I don't think they support daisy-chaining. In any case, I was connecting the monitors directly to the hp t730 DP ports.

Arch Linux

#1 2023-09-18 01:58:41

Multiple monitor issue on Wayland

#2 2023-09-18 15:29:27

Re: Multiple monitor issue on Wayland

#3 2023-09-19 02:34:49

Re: Multiple monitor issue on Wayland

#4 2023-09-19 14:23:31

Re: Multiple monitor issue on Wayland

#5 2023-09-19 14:37:17

Re: Multiple monitor issue on Wayland

#6 2023-09-27 01:05:55

Re: Multiple monitor issue on Wayland

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