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#1 2022-06-21 08:41:38

kobhian
Member
Registered: 2021-02-07
Posts: 10

Screen disabled when using hardware KVM

Hello,

I have two machines operating on the same screen through a hardware KVM (both computers using Displayport 1.4)

If I boot into Arch, it all works fine, but as soon as I switch to Windows and try to return to Arch, it just doesn't turn on the screen until I reboot. The machine is still running as I can still do most of my work through SSH but that's not ideal if I need to use some GUI-only apps.

I take it happens for the KVM literally switches off the hardware connection and Arch can't see the screen if it's booted already, anyway to force arch to re-check the connection as I switch back?

Thank you!

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#2 2022-06-21 10:11:30

Lone_Wolf
Member
From: Netherlands, Europe
Registered: 2005-10-04
Posts: 10,140

Re: Screen disabled when using hardware KVM

Does windows has the issue also ?

I can think of atleast 2 possible causes :

- the kvm switch may not fully support DP 1.4 (many kvm switches for consumers focus on hdmi support)

- the videocard and/or driver in the archlinux system don't handle DP changes well

Brand & model of the kvm switch ?

please post full lspci -k output from the arch system (run as normal user)

Last edited by Lone_Wolf (2022-06-21 10:11:53)


Disliking systemd intensely, but not satisfied with alternatives so focusing on taming systemd.
Did you use the guided installer ? If yes, I can't help you.

(A works at time B)  && (time C > time B ) ≠  (A works at time C)

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#3 2022-06-21 10:22:42

kobhian
Member
Registered: 2021-02-07
Posts: 10

Re: Screen disabled when using hardware KVM

Hello Lone_Worf,

The KVM is DP 1.4.
Windows works great with it, 0 issues.
here's the KVM and its specs
My Graphic card is an Nvidia GTX 980, running the standard Nvidia driver
Here's the full lspci -k output - https://pastebin.com/k4jwTjPr

Thanks!

Last edited by kobhian (2022-06-21 10:23:06)

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#4 2022-06-21 10:48:08

Lone_Wolf
Member
From: Netherlands, Europe
Registered: 2005-10-04
Posts: 10,140

Re: Screen disabled when using hardware KVM

The kvm switch doesn't use DP over USB-C as I expected, but has DP connectors for the hosts .

lspci doesn't show an iGPU, so this is a system with one discrete nvidia videocard, not a hybrid graphics setup.

Uncommon setup, but should make troubleshooting easier.

Are you using X or wayland ?
How are you starting the graphics environment ?

Does the problem also occur if you boot to console multi-user.target and not start graphics environment ?
see https://wiki.archlinux.org/title/System … _boot_into

Last edited by Lone_Wolf (2022-06-21 10:48:42)


Disliking systemd intensely, but not satisfied with alternatives so focusing on taming systemd.
Did you use the guided installer ? If yes, I can't help you.

(A works at time B)  && (time C > time B ) ≠  (A works at time C)

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#5 2022-06-21 10:55:27

kobhian
Member
Registered: 2021-02-07
Posts: 10

Re: Screen disabled when using hardware KVM

I am using X.

I am starting the graphics environment in the standard way, GDM?

if I switch to another tty, without a graphical environment, it works, if I switch back to my main tty, I get my lockscreen, but as soon as I input my pw, it blacks out and turns screen off.

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