Resolution problem with KVM switch

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1

I have an ATEN (CS1944DP) KVMP Switch where a Ubuntu computer and a Fedora 39 computer are connected.
When I switch from Fedora (res 256x1440 16:9) to Ubuntu with hotkey the resolution is OK with Ubuntu (res 256x1440 16:9) but switching back from Ubuntu to Fedora gives me resolution 1024x768 4:3 at Fedora.
To get back the resolution at Fedora I had before switching … a reboot of Fedora will fix it.
As I understand it is not an issue with the Switch but with Fedora.
How can that be fixed?

‘inxi -Gxx’ produced this output:

Graphics:
  Device-1: AMD Raven Ridge [Radeon Vega Series / Radeon Mobile Series]
    driver: amdgpu v: kernel arch: GCN-5 pcie: speed: 8 GT/s lanes: 16 ports:
    active: DP-1 empty: DP-2,DP-3,HDMI-A-1 bus-ID: 05:00.0 chip-ID: 1002:15dd
    temp: 38.0 C
  Display: wayland server: X.org v: 1.20.14 with: Xwayland v: 23.2.2
    compositor: gnome-shell v: 45.1 driver: X: loaded: amdgpu
    unloaded: fbdev,modesetting,vesa dri: radeonsi gpu: amdgpu display-ID: 0
  Monitor-1: DP-1 model: Dell U2715H res: 2560x1440 dpi: 109
    diag: 685mm (27")
  API: OpenGL v: 4.6 vendor: amd mesa v: 23.2.1 glx-v: 1.4 es-v: 3.2
    direct-render: yes renderer: AMD Radeon Vega 11 Graphics (raven LLVM 16.0.6
    DRM 3.54 6.6.2-201.fc39.x86_64) device-ID: 1002:15dd display-ID: :0.0
  API: EGL Message: EGL data requires eglinfo. Check --recommends.
2

What does inxi -Gxx report when you see the low res?

Do you see kernel messages in dmesg when you make the switch back?

Oh and its worth checking the cables are seated correctly.

3

When low res …

$ inxi -Gxx
Graphics:
  Device-1: AMD Raven Ridge [Radeon Vega
    Series / Radeon Mobile Series]
    driver: amdgpu v: kernel arch: GCN-5 pcie:
    speed: 8 GT/s lanes: 16 ports: active: DP-1
    empty: DP-2,DP-3,HDMI-A-1 bus-ID: 05:00.0
    chip-ID: 1002:15dd temp: 39.0 C
  Display: wayland server: X.org v: 1.20.14
    with: Xwayland v: 23.2.2
    compositor: gnome-shell v: 45.1 driver: X:
    loaded: amdgpu
    unloaded: fbdev,modesetting,vesa
    dri: radeonsi gpu: amdgpu display-ID: 0
  Monitor-1: DP-1 model: Dell U2715H
    res: 2560x1440 dpi: 109 diag: 685mm (27")
  API: OpenGL v: 4.6 vendor: amd mesa
    v: 23.2.1 glx-v: 1.4 es-v: 3.2
    direct-render: yes renderer: AMD Radeon
    Vega 11 Graphics (raven LLVM 16.0.6 DRM
    3.54 6.6.2-201.fc39.x86_64)
    device-ID: 1002:15dd display-ID: :0.0
  API: EGL Message: EGL data requires
    eglinfo. Check --recommends.

Kernel messages …

dmesg | grep -i kernel
[    0.064436] Booting paravirtualized kernel on bare hardware
[    0.071155] Kernel command line: BOOT_IMAGE=(hd0,gpt2)/vmlinuz-6.6.2-201.fc39.x86_64 root=UUID=81ee9c9b-0cdf-42d9-8aa4-299e7d7ce4fc ro rootflags=subvol=root rhgb quiet
[    0.071221] Unknown kernel command line parameters "rhgb BOOT_IMAGE=(hd0,gpt2)/vmlinuz-6.6.2-201.fc39.x86_64", will be passed to user space.
[    0.137604] Memory: 30578160K/31388472K available (18432K kernel code, 3275K rwdata, 14580K rodata, 4544K init, 5020K bss, 810056K reserved, 0K cma-reserved)
[    0.157503] Speculative Return Stack Overflow: WARNING: See https://kernel.org/doc/html/latest/admin-guide/hw-vuln/srso.html for mitigation options.
[    0.310969] DMA: preallocated 4096 KiB GFP_KERNEL pool for atomic allocations
[    0.310976] DMA: preallocated 4096 KiB GFP_KERNEL|GFP_DMA pool for atomic allocations
[    0.310981] DMA: preallocated 4096 KiB GFP_KERNEL|GFP_DMA32 pool for atomic allocations
[    0.903481] Loaded X.509 cert 'Fedora kernel signing key: 6dbb7c71dd90f40a376d62ea817b282dfae08557'
[    0.916195] Loaded X.509 cert 'Fedora kernel signing key: 6dbb7c71dd90f40a376d62ea817b282dfae08557'
[    1.166682] Freeing unused kernel image (initmem) memory: 4544K
[    1.166690] Write protecting the kernel read-only data: 34816k
[    1.167388] Freeing unused kernel image (rodata/data gap) memory: 1804K
[    1.461050] systemd[1]: Listening on systemd-udevd-kernel.socket - udev Kernel Socket.
[    1.465472] systemd[1]: Starting systemd-modules-load.service - Load Kernel Modules...
[    1.522743] systemd[1]: Finished systemd-modules-load.service - Load Kernel Modules.
[    1.524181] systemd[1]: Starting systemd-sysctl.service - Apply Kernel Variables...
[    4.670410] [drm] amdgpu kernel modesetting enabled.
[    4.679886] [drm] initializing kernel modesetting (RAVEN 0x1002:0x15DD 0x1002:0x15DD 0xC6).
[    6.559371] systemd[1]: Listening on systemd-udevd-kernel.socket - udev Kernel Socket.
[    6.568288] systemd[1]: Mounting sys-kernel-debug.mount - Kernel Debug File System...
[    6.571347] systemd[1]: Mounting sys-kernel-tracing.mount - Kernel Trace File System...
[    6.571644] systemd[1]: auth-rpcgss-module.service - Kernel Module supporting RPCSEC_GSS was skipped because of an unmet condition check (ConditionPathExists=/etc/krb5.keytab).
[    6.580948] systemd[1]: Starting modprobe@configfs.service - Load Kernel Module configfs...
[    6.583740] systemd[1]: Starting modprobe@dm_mod.service - Load Kernel Module dm_mod...
[    6.586712] systemd[1]: Starting modprobe@drm.service - Load Kernel Module drm...
[    6.589345] systemd[1]: Starting modprobe@fuse.service - Load Kernel Module fuse...
[    6.592074] systemd[1]: Starting modprobe@loop.service - Load Kernel Module loop...
[    6.634816] systemd[1]: Starting systemd-modules-load.service - Load Kernel Modules...
[    6.637753] systemd[1]: Starting systemd-network-generator.service - Generate network units from Kernel command line...
[    6.637924] systemd[1]: systemd-pcrmachine.service - TPM2 PCR Machine ID Measurement was skipped because of an unmet condition check (ConditionPathExists=/sys/firmware/efi/efivars/StubPcrKernelImage-4a67b082-0a4c-41cf-b6c7-440b29bb8c4f).
[    6.640674] systemd[1]: Starting systemd-remount-fs.service - Remount Root and Kernel File Systems...
[    6.649136] systemd[1]: Mounted sys-kernel-debug.mount - Kernel Debug File System.
[    6.649438] systemd[1]: Mounted sys-kernel-tracing.mount - Kernel Trace File System.
[    7.812212] MCE: In-kernel MCE decoding enabled.
4

More info when running xrandr
High res …

$ xrandr
Screen 0: minimum 16 x 16, current 2560 x 1440, maximum 32767 x 32767
DP-1 connected primary 2560x1440+0+0 (normal left inverted right x axis y axis) 600mm x 340mm
   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  
   1152x720      59.75  
   960x600       59.63  
   928x580       59.88  
   800x500       59.50  
   768x480       59.38  
   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

Low res …

$ xrandr
Screen 0: minimum 16 x 16, current 1024 x 768, maximum 32767 x 32767
DP-1 connected primary 1024x768+0+0 (normal left inverted right x axis y axis) 600mm x 340mm
   1024x768      59.92*+
   800x600       59.86  
   640x480       59.38  
   320x240       59.52  
   960x600       59.63  
   928x580       59.88  
   800x500       59.50  
   768x480       59.90  
   720x480       59.71  
   640x400       59.95  
   320x200       58.96  
   1024x576      59.90  
   864x486       59.92  
   720x400       59.55  
   640x350       59.77  
[forsete@balder: ~] $
5

What is the output of xrandr --verbose in both cases?
I wonder if the EDID is missing in the broken case.
Also do you see any edid logs in the output if sudo dmesg?

6

There is no apperance of ‘edid’ in the output of sudo dmesg.

Hi res …

$ xrandr --verbose
Screen 0: minimum 16 x 16, current 2560 x 1440, maximum 32767 x 32767
DP-1 connected primary 2560x1440+0+0 (0x23) normal (normal left inverted right x axis y axis) 600mm x 340mm
	Identifier: 0x21
	Timestamp:  27208
	Subpixel:   unknown
	Gamma:      1.0:1.0:1.0
	Brightness: 0.0
	Clones:    
	CRTC:       0
	CRTCs:      0
	Transform:  1.000000 0.000000 0.000000
	            0.000000 1.000000 0.000000
	            0.000000 0.000000 1.000000
	           filter: 
	RANDR Emulation: 1 
	non-desktop: 0 
		supported: 0, 1
  2560x1440 (0x23) 312.000MHz -HSync +VSync *current +preferred
        h: width  2560 start 2752 end 3024 total 3488 skew    0 clock  89.45KHz
        v: height 1440 start 1443 end 1448 total 1493           clock  59.91Hz
  1920x1440 (0x24) 233.250MHz -HSync +VSync
        h: width  1920 start 2064 end 2264 total 2608 skew    0 clock  89.44KHz
        v: height 1440 start 1443 end 1447 total 1493           clock  59.90Hz
  1600x1200 (0x25) 161.000MHz -HSync +VSync
        h: width  1600 start 1712 end 1880 total 2160 skew    0 clock  74.54KHz
        v: height 1200 start 1203 end 1207 total 1245           clock  59.87Hz
  1440x1080 (0x26) 128.750MHz -HSync +VSync
        h: width  1440 start 1528 end 1680 total 1920 skew    0 clock  67.06KHz
        v: height 1080 start 1083 end 1087 total 1120           clock  59.87Hz
  1400x1050 (0x27) 121.500MHz -HSync +VSync
        h: width  1400 start 1488 end 1632 total 1864 skew    0 clock  65.18KHz
        v: height 1050 start 1053 end 1057 total 1089           clock  59.86Hz
  1280x1024 (0x28) 108.750MHz -HSync +VSync
        h: width  1280 start 1368 end 1496 total 1712 skew    0 clock  63.52KHz
        v: height 1024 start 1027 end 1034 total 1063           clock  59.76Hz
  1280x960 (0x29) 101.250MHz -HSync +VSync
        h: width  1280 start 1360 end 1488 total 1696 skew    0 clock  59.70KHz
        v: height  960 start  963 end  967 total  996           clock  59.94Hz
  1152x864 (0x2a) 81.500MHz -HSync +VSync
        h: width  1152 start 1216 end 1336 total 1520 skew    0 clock  53.62KHz
        v: height  864 start  867 end  871 total  897           clock  59.78Hz
  1024x768 (0x2b) 63.250MHz -HSync +VSync
        h: width  1024 start 1072 end 1176 total 1328 skew    0 clock  47.63KHz
        v: height  768 start  771 end  775 total  798           clock  59.68Hz
  800x600 (0x2c) 38.250MHz -HSync +VSync
        h: width   800 start  832 end  912 total 1024 skew    0 clock  37.35KHz
        v: height  600 start  603 end  607 total  624           clock  59.86Hz
  640x480 (0x2d) 23.750MHz -HSync +VSync
        h: width   640 start  664 end  720 total  800 skew    0 clock  29.69KHz
        v: height  480 start  483 end  487 total  500           clock  59.38Hz
  320x240 (0x2e)  6.000MHz -HSync +VSync
        h: width   320 start  336 end  360 total  400 skew    0 clock  15.00KHz
        v: height  240 start  243 end  247 total  252           clock  59.52Hz
  1920x1200 (0x2f) 193.250MHz -HSync +VSync
        h: width  1920 start 2056 end 2256 total 2592 skew    0 clock  74.56KHz
        v: height 1200 start 1203 end 1209 total 1245           clock  59.88Hz
  1680x1050 (0x30) 146.000MHz -HSync +VSync
        h: width  1680 start 1784 end 1960 total 2240 skew    0 clock  65.18KHz
        v: height 1050 start 1053 end 1059 total 1089           clock  59.85Hz
  1440x900 (0x31) 106.500MHz -HSync +VSync
        h: width  1440 start 1528 end 1672 total 1904 skew    0 clock  55.93KHz
        v: height  900 start  903 end  909 total  934           clock  59.89Hz
  1280x800 (0x32) 83.500MHz -HSync +VSync
        h: width  1280 start 1352 end 1480 total 1680 skew    0 clock  49.70KHz
        v: height  800 start  803 end  809 total  831           clock  59.81Hz
  1152x720 (0x33) 66.500MHz -HSync +VSync
        h: width  1152 start 1208 end 1320 total 1488 skew    0 clock  44.69KHz
        v: height  720 start  723 end  729 total  748           clock  59.75Hz
  960x600 (0x34) 45.250MHz -HSync +VSync
        h: width   960 start  992 end 1088 total 1216 skew    0 clock  37.21KHz
        v: height  600 start  603 end  609 total  624           clock  59.63Hz
  928x580 (0x35) 42.750MHz -HSync +VSync
        h: width   928 start  968 end 1056 total 1184 skew    0 clock  36.11KHz
        v: height  580 start  583 end  589 total  603           clock  59.88Hz
  800x500 (0x36) 30.750MHz -HSync +VSync
        h: width   800 start  824 end  896 total  992 skew    0 clock  31.00KHz
        v: height  500 start  503 end  509 total  521           clock  59.50Hz
  768x480 (0x37) 28.500MHz -HSync +VSync
        h: width   768 start  792 end  864 total  960 skew    0 clock  29.69KHz
        v: height  480 start  483 end  489 total  500           clock  59.38Hz
  720x480 (0x38) 26.750MHz -HSync +VSync
        h: width   720 start  744 end  808 total  896 skew    0 clock  29.85KHz
        v: height  480 start  483 end  493 total  500           clock  59.71Hz
  640x400 (0x39) 19.750MHz -HSync +VSync
        h: width   640 start  664 end  720 total  800 skew    0 clock  24.69KHz
        v: height  400 start  403 end  409 total  417           clock  59.20Hz
  320x200 (0x3a)  5.000MHz -HSync +VSync
        h: width   320 start  336 end  360 total  400 skew    0 clock  12.50KHz
        v: height  200 start  203 end  209 total  212           clock  58.96Hz
  2048x1152 (0x3b) 197.000MHz -HSync +VSync
        h: width  2048 start 2184 end 2400 total 2752 skew    0 clock  71.58KHz
        v: height 1152 start 1155 end 1160 total 1195           clock  59.90Hz
  1920x1080 (0x3c) 172.750MHz -HSync +VSync
        h: width  1920 start 2048 end 2248 total 2576 skew    0 clock  67.06KHz
        v: height 1080 start 1083 end 1088 total 1120           clock  59.88Hz
  1600x900 (0x3d) 118.000MHz -HSync +VSync
        h: width  1600 start 1696 end 1856 total 2112 skew    0 clock  55.87KHz
        v: height  900 start  903 end  908 total  934           clock  59.82Hz
  1368x768 (0x3e) 85.250MHz -HSync +VSync
        h: width  1368 start 1440 end 1576 total 1784 skew    0 clock  47.79KHz
        v: height  768 start  771 end  781 total  798           clock  59.88Hz
  1280x720 (0x3f) 74.500MHz -HSync +VSync
        h: width  1280 start 1344 end 1472 total 1664 skew    0 clock  44.77KHz
        v: height  720 start  723 end  728 total  748           clock  59.86Hz
  1024x576 (0x40) 46.500MHz -HSync +VSync
        h: width  1024 start 1064 end 1160 total 1296 skew    0 clock  35.88KHz
        v: height  576 start  579 end  584 total  599           clock  59.90Hz
  864x486 (0x41) 32.250MHz -HSync +VSync
        h: width   864 start  888 end  968 total 1072 skew    0 clock  30.08KHz
        v: height  486 start  489 end  494 total  506           clock  59.45Hz
  720x400 (0x42) 22.250MHz -HSync +VSync
        h: width   720 start  744 end  808 total  896 skew    0 clock  24.83KHz
        v: height  400 start  403 end  413 total  417           clock  59.55Hz
  640x350 (0x43) 17.500MHz -HSync +VSync
        h: width   640 start  664 end  720 total  800 skew    0 clock  21.88KHz
        v: height  350 start  353 end  363 total  366           clock  59.77Hz

Low res …


 $ xrandr --verbose
Screen 0: minimum 16 x 16, current 1024 x 768, maximum 32767 x 32767
DP-1 connected primary 1024x768+0+0 (0x414) normal (normal left inverted right x axis y axis) 600mm x 340mm
	Identifier: 0x413
	Timestamp:  27208
	Subpixel:   unknown
	Gamma:      11.:inf:inf
	Brightness: 0.38
	Clones:    
	CRTC:       0
	CRTCs:      0
	Transform:  1.000000 0.000000 0.000000
	            0.000000 1.000000 0.000000
	            0.000000 0.000000 1.000000
	           filter: 
	RANDR Emulation: 1 
	non-desktop: 0 
		supported: 0, 1
  1024x768 (0x414) 63.500MHz -HSync +VSync *current +preferred
        h: width  1024 start 1072 end 1176 total 1328 skew    0 clock  47.82KHz
        v: height  768 start  771 end  775 total  798           clock  59.92Hz
  800x600 (0x2c) 38.250MHz -HSync +VSync
        h: width   800 start  832 end  912 total 1024 skew    0 clock  37.35KHz
        v: height  600 start  603 end  607 total  624           clock  59.86Hz
  640x480 (0x2d) 23.750MHz -HSync +VSync
        h: width   640 start  664 end  720 total  800 skew    0 clock  29.69KHz
        v: height  480 start  483 end  487 total  500           clock  59.38Hz
  320x240 (0x2e)  6.000MHz -HSync +VSync
        h: width   320 start  336 end  360 total  400 skew    0 clock  15.00KHz
        v: height  240 start  243 end  247 total  252           clock  59.52Hz
  960x600 (0x34) 45.250MHz -HSync +VSync
        h: width   960 start  992 end 1088 total 1216 skew    0 clock  37.21KHz
        v: height  600 start  603 end  609 total  624           clock  59.63Hz
  928x580 (0x35) 42.750MHz -HSync +VSync
        h: width   928 start  968 end 1056 total 1184 skew    0 clock  36.11KHz
        v: height  580 start  583 end  589 total  603           clock  59.88Hz
  800x500 (0x36) 30.750MHz -HSync +VSync
        h: width   800 start  824 end  896 total  992 skew    0 clock  31.00KHz
        v: height  500 start  503 end  509 total  521           clock  59.50Hz
  768x480 (0x415) 28.750MHz -HSync +VSync
        h: width   768 start  792 end  864 total  960 skew    0 clock  29.95KHz
        v: height  480 start  483 end  489 total  500           clock  59.90Hz
  720x480 (0x38) 26.750MHz -HSync +VSync
        h: width   720 start  744 end  808 total  896 skew    0 clock  29.85KHz
        v: height  480 start  483 end  493 total  500           clock  59.71Hz
  640x400 (0x416) 20.000MHz -HSync +VSync
        h: width   640 start  664 end  720 total  800 skew    0 clock  25.00KHz
        v: height  400 start  403 end  409 total  417           clock  59.95Hz
  320x200 (0x3a)  5.000MHz -HSync +VSync
        h: width   320 start  336 end  360 total  400 skew    0 clock  12.50KHz
        v: height  200 start  203 end  209 total  212           clock  58.96Hz
  1024x576 (0x40) 46.500MHz -HSync +VSync
        h: width  1024 start 1064 end 1160 total 1296 skew    0 clock  35.88KHz
        v: height  576 start  579 end  584 total  599           clock  59.90Hz
  864x486 (0x417) 32.500MHz -HSync +VSync
        h: width   864 start  888 end  968 total 1072 skew    0 clock  30.32KHz
        v: height  486 start  489 end  494 total  506           clock  59.92Hz
  720x400 (0x42) 22.250MHz -HSync +VSync
        h: width   720 start  744 end  808 total  896 skew    0 clock  24.83KHz
        v: height  400 start  403 end  413 total  417           clock  59.55Hz
  640x350 (0x43) 17.500MHz -HSync +VSync
        h: width   640 start  664 end  720 total  800 skew    0 clock  21.88KHz
        v: height  350 start  353 end  363 total  366           clock  59.77Hz
7

I suspect the problem is that the EDID is not sent when or corrupted when you switch between systems. On the off chance that the problem tracks to the port used what happens if you switch the cables between the two systems?

8

I replaced the Ubuntu system with Windows11.
So now I have following setup:

Switch port 1: Dell laptop with Fedora
Switch port 2: Window11
Switch port 3: Fedora desktop computer
Switch port 4: Not used

The Windows11 keeps the resolution when switching but not the Fedora computers.
Strange that the problem occurs only with Fedora …

You suspect the problem is that the EDID is not sent correctly when switching.
Is it a cable problem, switch problem or Fedora problem?
I don’t have any experience with EDID … I have upgraded the switch to the latest firmware.
Should I contact the switch supplier?

9

kernel.org Admin Guide EDID offers workarounds.

10

I switched the cables but the problem remains … but only for Fedora system … Windows11 & Ubuntu works OK

11

Sound very diffucult for avarage users …