External monitor power management issues
from GreatBlueHeron@piefed.ca to linux@lemmy.ml on 26 Jun 2025 12:22
https://piefed.ca/post/33944

It feels weird to just jump into a generic Linux community and ask a question. It’s nice being so small - kinda like the internet used to be.

Anyway, I’ve been running Linux servers for decades but only recently switched my desktop. I first tried Debian 12 and I’m now on OpenSUSE Tumbleweed - I switched in the hope of getting newer drivers and maybe fixing this issue.

I have a HP laptop with onboard Intel graphics and an external monitor connected with USB-C. In general it works great - until it doesn’t. From time to time the external monitor does not wake up after a suspend. Normally turning the monitor off and back on will cause some sort of driver reset and it comes back. Once or twice this has not helped and I’ve had to reboot.

I’m running Xorg as Wayland on Tumbleweed won’t start on t his machine. Wayland may have worked with Debian, I don’t recall. I don’t think it’s worth listing details of my versions as it’s happened on two distros and through a couple of minor updates to Xorg on openSUSE. It happens with KDE or LXDE.

Any suggestions?

#linux

threaded - newest

just_another_person@lemmy.world on 26 Jun 2025 13:07 next collapse

Few things:

  1. If you use the same USB port for this all the time, disable power saving on that port
  2. Make sure this isn’t a PD port (this is a laptop design annoyance)
  3. Make sure your monitor’s own power saving settings aren’t the issue by disabling things like “deep sleep” or similar

Another thing to try is download Fedora LiveUSB and test it with that (it will be Wayland). If it works, then you know it’s a config issue with your distro.

GreatBlueHeron@piefed.ca on 26 Jun 2025 14:10 collapse

1) If you use the same USB port for this all the time, disable power saving on that port

I use the same port all the time. I want power saving on the port. I like to just get up from my PC and have it go to sleep by itself and wake back up when I come and jiggle the mouse. It's working exactly as I would like maybe 90% of the time. Just sometimes the external monitor doesn't wake up.

2) Make sure this isn't a PD port (this is a laptop design annoyance)

It is a PD port, and it is powering the laptop. I'm not sure why this would be a problem? It's worked fine for 5-6 years with Windows and works 90% of the time now with Linux.

3) Make sure your monitor's own power saving settings aren't the issue by disabling things like "deep sleep" or similar

Again, I'm not sure how this could be a problem for the scenario I describe. The settings work fine 90% of the time. It's not even time related: sometimes I can come to it first thing in the morning, after it's been asleep all night, and it wakes perfectly; sometimes I can get up to go get a glass of water and come back and the external monitor won't wake up. It seems totally random.

just_another_person@lemmy.world on 26 Jun 2025 15:27 collapse

  1. Power saving features may not fire on changing from sleep states. This happens on Windows as well, but the power management system in Windows disables power saving features of the port when a display is detected. In Linux you want this off for the same reasons. It doesn’t prevent the machine from sleeping.
  2. On waking, PD ports can cause issues with negotiation of the signal reset and changemode for displays.
  3. Monitors communicate their power status over USB-C, so when your machine wakes up, it may try to fire an event that says “wake up” to the monitor, but if the monitor isn’t in a state where it’s expected a signal (deep sleep), then it won’t wake up.

Any one of these could be the issue, but if you don’t want to take steps to debug it, then just unplugging and replugging the cable will kick the monitor back up.

catloaf@lemm.ee on 26 Jun 2025 14:59 next collapse

Does it work if you unplug and replug? If you hit a button other than power does it wake up, or does it say “no signal” or something? Does the laptop see it? Anything in any log? Can you force a redetection from the laptop?

GreatBlueHeron@piefed.ca on 26 Jun 2025 15:13 collapse

Does it work if you unplug and replug?

In general, yes.

If you hit a button other than power does it wake up, or does it say "no signal" or something?

Yes.

Does the laptop see it?

I'm assuming not as it does not display on it. Next time it happens I'll see what xrandr says.

Anything in any log?

Nothing in Xorg.0.log and nothing that seems related in the journal. I'll keep journalctl --follow running and see if anything that I didn't pick as being related comes up next time it happens.

Can you force a redetection from the laptop?

Probably, but I don't know how.

BCsven@lemmy.ca on 26 Jun 2025 15:43 next collapse

I ran into this with HDMI on motherboard, not always though. My remedy was, since I had KDE connect on phone and PC, that I run a display shut down and wake command from the phone. It seems to wake something up in the OS

glitching@lemmy.ml on 27 Jun 2025 08:48 collapse

you’re running way too old a distro for what you want. debian 12 has its merits as a server, you install it and leave it be and it just works.

what you want - fluidity with power management, dock/undock, etc - although achievable with tweaking this and that isn’t being worked on, not on X, not on debian 12, so it’s not like those things will eventually get there. so you need a semi-modern distro, like ubuntu or fedora or even trixie.

wayland isn’t new, it’s default on a lot of distros since 2021 or so, so you can be sure that your use case was previosly met and solved. costs you nothing to boot e.g. F42 off a USB and try it out (has to be 42 as earlier live sessions default to X11). if you have lots of RAM, add the rd.live.ram switch so it copies the image to RAM and everything is super-snappy for testing and it doesn’t touch your SSD.