[kde] [Bug 453557] New: Black screen when waking up the computer in 4K resolution with KDE and an HDMI Edid emulator connected

[Chema]

https://bugs.kde.org/show_bug.cgi?id=453557

            Bug ID: 453557
           Summary: Black screen when waking up the computer in 4K
                    resolution with KDE and an HDMI Edid emulator
                    connected
           Product: kde
           Version: unspecified
          Platform: Other
                OS: Linux
            Status: REPORTED
          Severity: normal
          Priority: NOR
         Component: general
          Assignee: unassigned-bugs at kde.org
          Reporter: rondo.sp at gmail.com
  Target Milestone: ---

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]).

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