Wayland KDE and GNOME support 2560x1440 monitor differently?

I used to work under GNOME from Fedora 28 to 36. However, Gnome Wayland does not support my external display with 2560x1440 @ 60 Hz or 78 Hz. In order for the resolution to work, I have to use Xorg, but add refresh rate of 39 Hz to work with xrandr. Recently, out of curiosity, I tried with KDE plasma, and found Plasma Wayland support 2560x1440 at refresh rate of 60 Hz without any configurations. I have to wonder what’s the magic of KDE Plasma Wayland that makes the resolution work, but not Gnome Wayland? The funny thing is if I log out KDE session (not reboot), and log into Gnome Wayland session, the 2560x1440 can work at 60 Hz. Anyone can explain why?

That’s very odd. I haven’t seen that behavior with my 1440p monitor. It should be based on the EDID that your monitor reports. Can you share the output of xrandrfrom the differing environments?

Thanks for your reply. Below is the output of xrandr:

Screen 0: minimum 320 x 200, current 4480 x 1440, maximum 16384 x 16384
eDP-1 connected 1920x1080+2560+0 (normal left inverted right x axis y axis) 381mm x 214mm
   1920x1080     60.05*+  60.01    59.97    59.96    59.93  
   1680x1050     59.95    59.88  
   1400x1050     59.98  
   1600x900      59.99    59.94    59.95    59.82  
   1280x1024     60.02  
   1400x900      59.96    59.88  
   1280x960      60.00  
   1440x810      60.00    59.97  
   1368x768      59.88    59.85  
   1280x800      59.99    59.97    59.81    59.91  
   1280x720      60.00    59.99    59.86    59.74  
   1024x768      60.04    60.00  
   960x720       60.00  
   928x696       60.05  
   896x672       60.01  
   1024x576      59.95    59.96    59.90    59.82  
   960x600       59.93    60.00  
   960x540       59.96    59.99    59.63    59.82  
   800x600       60.00    60.32    56.25  
   840x525       60.01    59.88  
   864x486       59.92    59.57  
   700x525       59.98  
   800x450       59.95    59.82  
   640x512       60.02  
   700x450       59.96    59.88  
   640x480       60.00    59.94  
   720x405       59.51    58.99  
   684x384       59.88    59.85  
   640x400       59.88    59.98  
   640x360       59.86    59.83    59.84    59.32  
   512x384       60.00  
   512x288       60.00    59.92  
   480x270       59.63    59.82  
   400x300       60.32    56.34  
   432x243       59.92    59.57  
   320x240       60.05  
   360x202       59.51    59.13  
   320x180       59.84    59.32  
DP-1 connected primary 2560x1440+0+0 (normal left inverted right x axis y axis) 698mm x 393mm
   2560x1440     74.78 +  59.95* 
   2560x1440_40.00  39.96  
   1920x1440     75.00    60.00  
   1856x1392     75.00    60.00  
   1792x1344     75.00    60.00  
   2048x1152     60.00  
   1920x1200     74.93    59.95  
   1920x1080     60.00    50.00    59.94  
   1920x1080i    60.00    50.00    59.94  
   1600x1200     75.00    70.00    65.00    60.00  
   1680x1050     74.89    59.88  
   1680x945      60.02  
   1400x1050     74.87    59.95  
   1600x900      60.00  
   1280x1024     75.02    60.02  
   1440x900      74.98    59.90  
   1280x960      60.00  
   1366x768      59.79  
   1360x768      60.02  
   1280x800      74.93    59.91  
   1152x864      75.00  
   1280x768      74.89    59.99  
   1280x720      60.00    50.00    59.94  
   1024x768      75.03    70.07    60.00  
   1024x576      59.97  
   800x600       72.19    75.00    60.32    56.25  
   720x576       50.00  
   848x480       60.00  
   720x480       60.00    59.94  
   640x480       75.00    72.81    60.00    59.94  
DP-2 disconnected (normal left inverted right x axis y axis)

This is obtained after I logout KDE and login xorg session.

Now I logout the previous xorg session, and login to gnome Wayland session, I got this:

Screen 0: minimum 16 x 16, current 4480 x 1440, maximum 32767 x 32767
XWAYLAND0 connected primary 2560x1440+0+0 (normal left inverted right x axis y axis) 700mm x 390mm
   2560x1440     59.91*+
   1920x1440     59.90  
   1600x1200     59.87  
   1440x1080     59.87  
   1400x1050     59.86  
   1280x1024     59.76  
   1280x960      59.94  
   1152x864      59.78  
   1024x768      59.68  
   800x600       59.86  
   640x480       59.38  
   320x240       59.52  
   1920x1200     59.88  
   1680x1050     59.85  
   1440x900      59.89  
   1280x800      59.81  
   720x480       59.71  
   640x400       59.20  
   320x200       58.96  
   2048x1152     59.90  
   1920x1080     59.88  
   1600x900      59.82  
   1368x768      59.88  
   1280x720      59.86  
   1024x576      59.90  
   864x486       59.45  
   720x400       59.55  
   640x350       59.77  
XWAYLAND1 connected 1920x1080+2560+0 (normal left inverted right x axis y axis) 380mm x 210mm
   1920x1080     59.96*+
   1440x1080     59.99  
   1400x1050     59.98  
   1280x1024     59.89  
   1280x960      59.94  
   1152x864      59.96  
   1024x768      59.92  
   800x600       59.86  
   640x480       59.38  
   320x240       59.52  
   1680x1050     59.95  
   1440x900      60.03  
   1280x800      59.99  
   720x480       59.71  
   640x400       59.95  
   320x200       58.96  
   1600x900      59.95  
   1368x768      59.88  
   1280x720      59.86  
   1024x576      59.90  
   864x486       59.92  
   720x400       59.55  
   640x350       59.77

Now, I rebooted and directly login to Gnome Wayland session, the external monitor does not receive signal under 2560x1440@59.9 Hz from the previous session. The output of xrandr:

XWAYLAND0 connected 2560x1440+0+0 (normal left inverted right x axis y axis) 700mm x 390mm
   2560x1440     59.91*+
   1920x1440     59.90  
   1600x1200     59.87  
   1440x1080     59.87  
   1400x1050     59.86  
   1280x1024     59.76  
   1280x960      59.94  
   1152x864      59.78  
   1024x768      59.68  
   800x600       59.86  
   640x480       59.38  
   320x240       59.52  
   1920x1200     59.88  
   1680x1050     59.85  
   1440x900      59.89  
   1280x800      59.81  
   720x480       59.71  
   640x400       59.20  
   320x200       58.96  
   2048x1152     59.90  
   1920x1080     59.88  
   1600x900      59.82  
   1368x768      59.88  
   1280x720      59.86  
   1024x576      59.90  
   864x486       59.45  
   720x400       59.55  
   640x350       59.77  
XWAYLAND1 connected primary 1920x1080+2560+0 (normal left inverted right x axis y axis) 380mm x 210mm
   1920x1080     59.96*+
   1440x1080     59.99  
   1400x1050     59.98  
   1280x1024     59.89  
   1280x960      59.94  
   1152x864      59.96  
   1024x768      59.92  
   800x600       59.86  
   640x480       59.38  
   320x240       59.52  
   1680x1050     59.95  
   1440x900      60.03  
   1280x800      59.99  
   720x480       59.71  
   640x400       59.95  
   320x200       58.96  
   1600x900      59.95  
   1368x768      59.88  
   1280x720      59.86  
   1024x576      59.90  
   864x486       59.92  
   720x400       59.55  
   640x350       59.77

Now I logout the gnome Wayland session, and log back in to KDE Wayland session, I got this:

XWAYLAND0 connected 1920x1080+2560+0 (normal left inverted right x axis y axis) 380mm x 210mm
   1920x1080     59.96*+
   1440x1080     59.99  
   1400x1050     59.98  
   1280x1024     59.89  
   1280x960      59.94  
   1152x864      59.96  
   1024x768      59.92  
   800x600       59.86  
   640x480       59.38  
   320x240       59.52  
   1680x1050     59.95  
   1440x900      60.03  
   1280x800      59.99  
   720x480       59.71  
   640x400       59.95  
   320x200       58.96  
   1600x900      59.95  
   1368x768      59.88  
   1280x720      59.86  
   1024x576      59.90  
   864x486       59.92  
   720x400       59.55  
   640x350       59.77  
XWAYLAND1 connected primary 2560x1440+0+0 (normal left inverted right x axis y axis) 700mm x 390mm
   2560x1440     59.91*+
   1920x1440     59.90  
   1600x1200     59.87  
   1440x1080     59.87  
   1400x1050     59.86  
   1280x1024     59.89  
   1280x960      59.94  
   1152x864      59.78  
   1024x768      59.68  
   800x600       59.86  
   640x480       59.38  
   320x240       59.52  
   1920x1200     59.88  
   1680x1050     59.85  
   1440x900      59.89  
   1280x800      59.81  
   720x480       59.71  
   640x400       59.20  
   320x200       58.96  
   2048x1152     59.90  
   1920x1080     59.88  
   1600x900      59.82  
   1368x768      59.88  
   1280x720      59.86  
   1024x576      59.90  
   864x486       59.45  
   720x400       59.55  
   640x350       59.77

The odd thing I see is that the the monitors appear to support the same resolutions overall but are showing up in different order between the two. Sometimes the 1080p is listed first and other times the 1440p is listed first.

Sorry for the edits. I see

DP-1 connected primary 2560x1440+0+0 (normal left inverted right x axis y axis) 698mm x 393mm
   2560x1440     74.78 +  59.95* 

in your first one with Xorg, so it seems Xorg detects a 75fps option where Wayland only detects a 60fps option. It seems this has more to do with Xorg vs Wayland than the desktop environment. If it works over 75fps with Xorg, then it’s a bug in Wayland, as far as I can tell.

In the display settings for KDE, both 75 Hz and 59.95 Hz refresh rates are shown (detected?), but only works with 59.95 Hz. If I select 75 Hz, the external monitor shows no signal.

If I log out of KDE and log back into gnome Wayland, 59.95 Hz also works, but not if you directly boost into gnome Wayland. Sounds to me that if I boost into gnome Wayland, some packages related to deal with 59.96 hz, otherwise started in KDE, not started, or ignored. If we can find this missing piece, I could directly boost into gnome Wayland session that supports 2560x1440 @59.95 Hz.

Right now, if I directly boost into gnome Wayland, I have to reduce the resolution to 2048x1152 @59.95 Hz for the external monitor to work.

It seems Wayland is reporting your actual sane capabilities and Xorg is also presenting theoretical capabilities, so neither is technically wrong in that case.

Here’s where this is going to get annoying. I’ve had displays that only got certain framerates over specific connectors (DisplayPort, HDMI, DVI, etc.), and cases where a monitor that otherwise might get a higher resolution over HDMI didn’t if the USB-C dock used DisplayPort internally. Additionally, some BIOS have a toggle where you can trade off more monitors for lower resolution support, especially if via USB-C/Thunderbolt. All of this is a terrible modern, mess, but since this is detected as DisplayPort now, try HDMI instead and if this is an HDMI cable, it might be going over a DP connection on the dock or internally, so try a DisplayPort cable instead, if that’s the case.

In fact, I connect the external monitor with HDMI cable. But I don’t know why it shows Display Port (DP-1). Under the same kernel, it works well under KDE Wayland, not gnome Wayland.

Unfortunately, many boards now have an HDMI port that is actually a DisplayPort on board and this can cause all sorts of weird issues. Do you have a DisplayPort port and cable that you could try instead?

No, I only have HDMI port on my computer. So far, I can live with KDE plasma. At my level, I don’t see any difference from Gnome Wayland, except for workflow.

After last update to the new kernel (inux fedora 5.19.4-200.fc36.x86_64 #1 SMP PREEMPT_DYNAMIC Thu Aug 25 17:42:04 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux), I can use 2560x1440 @59.95 Hz after directly login to Gnome Wayland. I further tried with 78 Hz, it works as well.

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