Bug#998378: Second monitor has correct mouse cursor and white+garbage

[Julien Puydt]

Le mercredi 03 novembre 2021 à 10:56 +0000, Simon McVittie a écrit :
> Control: tags -1 + moreinfo
> 
> On Wed, 03 Nov 2021 at 09:55:20 +0100, Julien Puydt wrote:
> > Where should I have a look to find error messages and fix the issue?
> 
> If in doubt, the answer is always the systemd journal (system log).
> 

Which I don't know how to read ; I get a lot of:

DMAR: DRHD: handling fault status reg 3
DMAR: [DMA Read NO_PASID] Request device [0x01:0x00.0] fault addr
0xfb808000 [fault reason 0x06] PTE Read access is not set

and:
dmar_fault: 36986 callbacks suppressed

which might be a smoking gun...

> > (1) The main "card" is Intel Corporation CoffeeLake-H GT2 [UHD
> > Graphics
> > 630], with kernel module i915. The second "card" is NVIDIA
> > Corporation
> > GP107M [GeForce GTX 1050 Mobile], with kernel module nouveau.
> 
> This sounds like it might be a dual-GPU laptop. Am I correct? If yes,
> what model of laptop?
> 

Yes, it's a laptop, ACER Nitro AN515-52.

> How is the "first" screen with correct display
> connected? (HDMI? DisplayPort? VGA? Built-in screen of a laptop?)
> 
Built-in screen.

> How is the "second" screen with incorrect display connected?
> 

HDMI cable.

> Do you know which GPU the two screens are physically connected to?
> For a desktop, it should be obvious from looking at which part they
> are
> plugged into; for a laptop, it's non-obvious, but we might be able to
> find
> out if you told us what laptop it is.
> 

The built-in screen is i915 and the external nouveau, as far as I know
-- at least I always had to modprobe nouveau for the second screen to
activate.

> > (2) I think both physical screens are detected, since xrandr says:
> > 
> > Screen 0: minimum 16 x 16, current 3840 x 1080, maximum 32767 x
> > 32767
> > XWAYLAND0 connected primary 1920x1080+0+0 (normal left inverted
> > right x
> > axis y axis) 340mm x 190mm
> >    1920x1080     60.05*+
> > XWAYLAND1 connected 1920x1080+1920+0 (normal left inverted right x
> > axis
> > y axis) 530mm x 300mm
> >    1920x1080    143.88*+
> 
> This is telling you about the emulated screens corresponding to your
> real screens, as presented by Xwayland based on information provided
> by GNOME Shell in native Wayland mode. For the real (lower-level)
> story, it might be helpful to look at:
> 
> head /sys/class/drm/card*-*/status
> head /sys/class/drm/card*-*/modes
> 

Status is "connected" for both ; for modes card0-eDP-1 has a single one
and the card1-HDMI-A-1 has many.

> I wonder whether the very high refresh rate (144 Hz) on the second
> screen is relevant to this: that's relatively unusual. If you
> configure it for a lower refresh rate like 60 Hz in gnome-control-
> center, does that work any better?

I had to install gnome-control-center for that ; no, it doesn't work
any better.

Thanks,

J.Puydt