Laptop, nouveau and external monitor

[Ilia Mirkin]

On Wed, Jan 1, 2025 at 9:57 PM H <agents at meddatainc.com> wrote:

> Running the latest version of Rocky Linux 9 fully updated and Mate on a
> Dell Inspiron 7570 laptop with a UHD display, i.e. 3840 x 2160 pixels. I
> would like to attach two external monitors and initially experimented with
> a Dell dock model 3100 and the latest version of the DisplayLink and evdi
> drivers. However, although the Mate display applet shows the correct
> resolution for the laptop display itself and for the external monitor which
> is running at 1920 x 1080 pixels, the resolution on the second, external
> display is more like 640 x 480 pixels.
>
> While I initially thought this was due to a bug in the DisplayLink/evdi
> drivers, I see the same issue when I connect the monitor directly to the
> HDMI output on the laptop itself, ie. DisplayLink/evdi are presumably not
> involved although they are installed, nor is the dock of course.
>
> I just discovered running xrandr --listmonitors that, while the internal
> laptop monitor is labeled eDP-1, xrandr identifies the external monitor as
> using DP-1 although it uses the laptop HDMI-connector. Further, while mate
> hardware display monitor also identifies it as using DP-1 - possibly based
> on xrandr output - the monitor itself tells me it is connected using its
> HDMI1 connector. xrandr does report the correct display resolution, though.
>
> Thus, it looks like xrandr/nouveau misreads the configuration feeding it
> to mate. I just updated the laptop BIOS to the very latest version and saw
> no difference.
>
> I am using an HDMI-HDMI cable with no adapters. I have tried both booting
> with the external monitor already attached and attaching/reattaching it
> later. The monitor is an Acer S230HL monitor.
>
> I am using the nouveau driver and inxi reports the presence of both Intel
> UHD Graphics 620 and Nvidia GM108M (GeForce 940MX).
>
> The kernel is:
> Linux 5.14.0-503.15.1.el9_5.x86_64 #1 SMP PREEMPT_DYNAMIC Tue Nov 26
> 17:24:29 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux
>
> Could this be an nouveau bug (I am running X11 and not Wayland)? How
> should I troubleshoot it?
>

No, this could not be a nouveau bug. I'm fairly sure that the GM108 is a
pure accelerator, so your screen is being connected to not-the-nvidia board
(either Intel or the USB DisplayLink thing).

Your Xorg log should generally have more useful info.

Cheers,

  -ilia
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