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I recently upgraded my computer to the latest debian 12 distribution. After the install, the default configuration using nouveau and wayland enabled me to see my dual screens with no problem. In my BIOS, IGD multimonitor is enabled.

To get better GPU performance, I then installed the nvidia driver for my graphical card, and switched from wayland to Xserver.

From this point on, everything seems odd: both my screens are working, the second screen being a mirror of the first. I can't detect the second screen through lspci, though:

01:00.0 VGA compatible controller: NVIDIA Corporation TU116 [GeForce GTX 1660 Ti] (rev a1)

I cannot force the mirrored screen to just be an extension of the first screen through "usual" methods: I went to the screen display module in debian 12, it shows an "HDMI-0" and "HDMI-1-1" screen, but when I press "detect", it detects HDMI-1-1 on both screens. The "HDMI-0" screen cannot be detected, although it is listed, has a resolution etc. Furthermore, it is clearly specified that both those screens are not mirroring any other screen.

Here are two screenshots of what is shown through the screen configuration module

Finally, I tried to use nvidia-config to generate a decent xorg.conf file and get myself out of this situation. The nvidia-config seems to only detect one screen also, even though both are being used by my computer (one is mirroring the second):

nvidia-config module

I tried to manually tweak my xorg.conf file and add instructions to handle the second monitor, so far it's not a success. Below is the conf file and some extra information provided by xrandr:

/etc/X11/xorg.conf:

# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings:  version 525.125.06

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0" 0 0
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0" "CorePointer"
    Option         "Xinerama" "0"
EndSection

Section "Files"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Mouse0"
    Driver         "mouse"
    Option         "Protocol" "auto"
    Option         "Device" "/dev/psaux"
    Option         "Emulate3Buttons" "no"
    Option         "ZAxisMapping" "4 5"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Keyboard0"
    Driver         "kbd"
EndSection

Section "Monitor"
    # HorizSync source: edid, VertRefresh source: edid
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "Idek Iiyama PL2288H"
    HorizSync       15.0 - 83.0
    VertRefresh     55.0 - 76.0
    Option         "DPMS"
EndSection

Section "Monitor"
    # HorizSync source: edid, VertRefresh source: edid
    Identifier     "Monitor1"
    VendorName     "Unknown"
    ModelName      "Idek Iiyama PL2288H"
    HorizSync       15.0 - 83.0
    VertRefresh     55.0 - 76.0
    Option         "DPMS"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "NVIDIA GeForce GTX 1660 Ti"
EndSection

Section "Screen"
    Identifier     "screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "Stereo" "0"
    Option         "nvidiaXineramaInfoOrder" "DFP-4"
    Option         "metamodes" "nvidia-auto-select +0+0"
    Option         "SLI" "Off"
    Option         "MultiGPU" "Off"
    Option         "BaseMosaic" "off"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Section "Device"
    Identifier     "screen1"
    Driver         "modesetting"
    BusID          "PCI:00:02.0"
EndSection

Section "Screen"
    Identifier     "screen1"
    Device         "Device1"
    Monitor        "Monitor1"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

xrandr output:

xrandr --listproviders
Providers: number : 2
Provider 0: id: 0x1b7 cap: 0x1, Source Output crtcs: 4 outputs: 7 associated providers: 1 name:NVIDIA-0
Provider 1: id: 0x202 cap: 0xf, Source Output, Sink Output, Source Offload, Sink Offload crtcs: 3 outputs: 4 associated providers: 1 name:modesetting
xrandr | grep HDMI                                                                                                                                                                                                                  1 ↵
HDMI-0 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 477mm x 268mm
HDMI-1-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 477mm x 268mm
HDMI-1-2 disconnected (normal left inverted right x axis y axis)
HDMI-1-3 disconnected (normal left inverted right x axis y axis)

I did not explore much with wayland instead of Xserver for two reasons: one, lots of people on the internet seem to advise against mixing wayland and nvidia-drivers. Two, if i let wayland active instead of Xserver, the second screen simply turns dark, and I've not been able to detect or configure it. The problem I encounter using Xserver seems a little more mild than when using Wayland.

Thanks in advance to anyone that could figure out what went wrong in what was supposed to be a clean install.

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  • I don't think lspci would ever detect screens, and the screens seem to be detected normally by xrandr. What happens if you try to activate th screens with xrandr? Something like xrandr --output HDMI-0 --auto --output HDMI-1 --left-of HDMI-0 --auto?
    – terdon
    Commented Sep 4, 2023 at 12:39
  • I inputed your command, it seems the HDMI-1 screen is working, but the HDMI-0 screen turns dark. I can move my mouse outside of the HDMI-1 screen boundaries, so i guess in some way my computer understands there is supposed to be a second monitor, but it remains dark.
    – oryx
    Commented Sep 4, 2023 at 13:15
  • OK. Please add that to the question. Also, you might want to try different combinations of those options, for instance, does xrandr --output HDMI-0 --auto alone make the HDMI-0 screen work?
    – terdon
    Commented Sep 4, 2023 at 13:18
  • It seems your first xrandr commands worked! It didnt seem to work at first but after a reboot the dual screens are properly working. Thanks a lot!
    – oryx
    Commented Sep 4, 2023 at 13:35

1 Answer 1

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Since your screens are correctly detected by xrandr, try setting them up using that. Something like this command should do it:

xrandr --output HDMI-0 --auto --output HDMI-1 --left-of HDMI-0 --auto
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  • This worked well on Debian 12 once I figured out that you can have lots of Display options like DP-x for Display ports. Do a xrandr and you can see which are active, you might need to pipe it into less if you have lots of options/screens. I ending up with HDMI-2 and DP-2 when I was seting up a TV box with Kodi and 2-4k screens, one of them being a 60" LG.
    – cpu
    Commented May 19 at 13:30

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