Bug 453557

Summary:	Black screen when waking up the computer in 4K resolution with KDE and an HDMI Edid emulator connected
Product:	[Plasma] KScreen	Reporter:	Chema <rondo.sp>
Component:	common	Assignee:	kscreen-bugs-null <kscreen-bugs-null>
Status:	REPORTED ---
Severity:	normal	CC:	kangarooo, nate, notmart, xaver.hugl
Priority:	NOR
Version:	5.24.5
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description Chema 2022-05-09 00:46:58 UTC

SUMMARY
When the computer cable is connected to an HDMI Edid emulator and the screen resolution is in 4K, when the computer sleeps from KDE and then wakes up, the monitor does not receive HDMI video signal and only black screen is displayed. When you switch sessions by pressing the Ctrl+Alt+F1 keys, the computer starts sending the HDMI signal to the monitor and then you can see the screen perfectly.

This problem does not occur on the Windows operating system nor does it occur with the GNOME desktop environment (tested with Fedora and Manjaro). In GNOME this works perfectly when the screen is in 4K resolution. It also does not happen if the KDE resolution at the time of suspending the computer is set to less than 4K resolution, but if it is 4K or higher, the problem I just mentioned occurs.

It does not depend on the Linux kernel either, I have tried with versions 5.16, 5.17 and 5.18 and the same thing happens in all of them from KDE.

STEPS TO REPRODUCE
1. Have an HDMI Edid emulator connected to the computer (or a KVM switch) in the HDMI input, and have the HDMI cable from the computer connected to the HDMI Edid emulator --> (HDMI Edid emulator: https://www.evanlak.com/products /hdmi-edid-emulator-4k-120hz).

2. Have the screen resolution in 4K mode (3840x2160).

3. Put the computer in sleep mode and wait a few seconds.

4. Wake up the computer.

OBSERVED RESULT
When I wake up the computer, the screen is completely black, the monitor does not receive an HDMI video signal. It doesn't react until you press (for example) Ctrl+Alt+F1 to switch sessions. By doing so, the monitor begins to receive the video signal and is already displayed correctly.

In KDE it works correctly with the HDMI Edid emulator connected if the screen resolution is less than 4K, but from 4K resolution the problem that I mentioned occurs that the screen stays black when waking up the computer.

I have tried several distros with GNOME (Fedora and Manjaro) and with this desktop environment it works perfectly having the HDMI Edid emulator connected, the computer can be suspended in 4K resolution and when it wakes up it shows the screen correctly again. However, I have tried several distros with KDE (Manjaro and KDE Neon) and in both the same thing happens, when suspending the computer in 4K resolution with the HDMI Edid emulator connected, when waking it up the screen is black until it is changed from session. I have also tried several Linux kernels (5.16, 5.17 and 5.18) and the same thing happens in all of them. It doesn't seem like a problem with the kernel, but with KDE, since as I say in the GNOME distros it works perfectly.

In the Windows operating system it also works perfectly, if I suspend the computer with the screen at 4K resolution, when I wake it up it is displayed correctly.

EXPECTED RESULT
As it happens in the GNOME desktop environment, when you wake up the computer it should correctly display the KDE screen and not get a black screen on the monitor without receiving an HDMI signal.

SOFTWARE/OS VERSIONS
Windows:
macOS:
Linux/KDE Plasma: 5.24.5
(available in About System)
KDE Plasma Version: 5.24.5
KDE Frameworks Version: 5.93.0
Qt Version: 5.15.3

ADDITIONAL INFORMATION
My computer is an AMD Ryzen 5 3550H with Radeon Vega Mobile GFX, the GPU is an integrated AMD Radeon Vega 8 Graphics. Linux is using the video-linux driver (Picasso [ATI Technologies Inc]).

Comment 1 Chema 2022-05-09 01:00:31 UTC

Sorry, the link to the HDMI Edid emulator was pasted wrong. The correct link is:

https://www.evanlak.com/products/hdmi-edid-emulator-4k-120hz

Or in Amazon:

https://www.amazon.com/EVanlak-Generrtion-Passthrough-Eliminated-Thunderbolt/dp/B07YMTMMH5?th=1

Comment 2 Chema 2022-05-09 01:10:23 UTC

Sorry, I also forgot to comment that this happens indistinctly in both X11 and Wayland, it doesn't matter which one you started, the same thing happens in both.

Comment 3 Chema 2022-05-11 16:25:33 UTC

I have discovered an interesting thing, I comment it in case it can give some clue of the cause of the problem.

When in a session with KDE at 4K screen resolution with the bidirectional HDMI Edid emulator connected, the computer is put into sleep mode and then wakes up, as I have mentioned, the monitor does not receive an HDMI signal and the screen remains black, no matter how much you move the mouse does not react, it does not receive a HDMI signal.

However, I have discovered a curious thing. If with the screen being black without receiving an HDMI signal, you wait 5 minutes for the lock screen to pop up, then when you move the mouse, it works! The monitor starts to receive HDMI signal, it is activated and you can see the KDE lock screen perfectly!

I just tested this with the KDE version of Fedora 36 that was released yesterday.

Comment 4 Kangarooo 2022-12-17 22:26:11 UTC

Is it fixed?
Can you try again?
Does connecting monitors and then running this in terminal fixes?
xrandr -q

Comment 5 Kangarooo 2022-12-17 22:27:36 UTC

Is it fixed?
Can you try again?
1. Maybe computer thinks it extending monitor, so try to move mouse if it appeared there.
2. Does connecting monitors and then running this in terminal fixes?
xrandr -q

Comment 6 Chema 2022-12-17 22:38:56 UTC

Hi,

I have performed the test again executing the command that you have indicated in the terminal, but the result is the same, when the computer goes into sleep mode, when it is woken up the screen stays black until you press Ctrl + F1 to change session in Linux, then the HDMI signal is recovered.

I am not using two monitors, nor am I using a laptop, I only have one monitor plugged into a KVM switch to which I have another 2 mini pc plugged, one with Windows and the other with Linux, and I have the HDMI emulator plugged into them so that the screen switching between machines is instantaneous.

However, I have also carried out the test connecting only the monitor cable directly to the computer, which has the HDMI emulator connected (I mean, without using the KVM switch) and the result is the same as indicated above.

Regards.

Comment 7 Nate Graham 2022-12-24 21:47:15 UTC

There's a chance this is fixed in the upcoming Plasma 5.27 due to the big multimonitor refactor.

Comment 8 Chema 2022-12-26 09:16:53 UTC

In that case, I'll wait for version 5.27 to see if that change solves this problem and the other problem with the HDMI bidirectional emulator. If it still doesn't work, I'll resend the logs.