Bug#1008296: Workaround for my machine

[alban.browaeys at gmail.com]

On Thu, 8 Sep 2022 17:22:00 -0300 =?UTF-8?Q?Sebasti=C3=A1n_Lacuesta?=
<sebastianlacuesta at gmail.com> wrote:
> Hi Alban,
> 
> My nvidia driver version: 510.85.02-1
> 
> cat /sys/module/nvidia_drm/parameters/modeset
> N


the gdm udev rules work how they ought to, ie:
/lib/udev/rules.d/61-gdm.rules "
# disable wayland if nvidia-drm modeset is not enabled
ATTR{parameters/modeset}!="Y", GOTO="gdm_disable_wayland"
"

a way around is
https://wiki.archlinux.org/title/GDM#Wayland_and_the_proprietary_NVIDIA_driver
ie https://wiki.archlinux.org/title/NVIDIA#DRM_kernel_mode_setting,
that is, add in /etc/default/grub to "GRUB_CMDLINE_LINUX_DEFAULT":
"nvidia_drm.modeset=1"
the run update-grub as root.

> 
> grep nomodeset /proc/cmdline
> <Empty>
> 
> Cheers,
> 
> Sebastián
> 
> El sáb, 27 ago 2022 a las 3:20, <alban.browaeys at gmail.com> escribió:
> 
> > On Fri, 8 Apr 2022 18:19:06 -0300 =?UTF-
8?Q?Sebasti=C3=A1n_Lacuesta?=
> > <sebastianlacuesta at gmail.com> wrote:
> > > Overwritting 61-gdm.rules with
> > >
> > > ln -s /dev/null /etc/udev/rules.d/61-gdm.rules
> > >
> > > solves the issue for me.
> >


About drm modeset
https://ubuntuforums.org/showthread.php?t=1613132  "
The newest kernels have moved the video mode setting into the kernel.
So all the programming of the hardware specific clock rates and
registers on the video card happen in the kernel rather than in the X
driver when the X server starts.. This makes it possible to have high
resolution nice looking splash (boot) screens and flicker free
transitions from boot splash to login screen. Unfortunately, on some
cards this doesnt work properly and you end up with a black screen.
Adding the nomodeset parameter instructs the kernel to not load video
drivers and use BIOS modes instead until X is loaded.
"
So enabling Kernel Mode Setting might lead to a black screen before the
nvidia driver is loaded (gdm start) if the nvidia driver is broken (or
not loaded).



>From https://wiki.archlinux.org/title/Wayland#XWayland 5.1 tells
enabling DRM KMS is required (for XWayland application only ?, ie most
games).



For early loading (console with optional "high resolution nice looking
splash (boot) screens and flicker free transitions from boot splash to
login screen") add in /etc/initramfs-tools/modules:
"nvidia nvidia_modeset nvidia_uvm nvidia_drm"
then run:
update-initramfs -u
(this only update the latest installed kernel), or for all kernels:
update-initramfs -u -k all
This if you want o try plymouth or want to set "GRUB_GFXMODE=" in
/etc/default/grub.

https://wiki.archlinux.org/title/kernel_mode_setting 2.1 tells that
NVIDIA kms has to be manually enabled (what we saw above).

All in all I do not believe this is software gdm bug that you cannot
start gdm in wayland mode with nvidia modesetting disabled (even if it
is disabled by default).

Can you confirm that with nvidia modeset enabled you do not need any
hack to start GDM in wayland mode (ie as i GDM shows gnome xorg and
wayland options)?
This is still an issue but a note on 
/usr/share/doc/gdm3/README.Debian might be enough to clarify that on
nvidia setups one has to enable modeset on grub?

Kind regards,

Alban


PS: I still do not know if current NVIDIA driver default to not enable
modeset is really an issue for gnome wayland or if only helps with
screen flickers when switching from wyaland to console and helps with
advanced graphics on boot console.
Maybe this requirement could be removed, and in this case this bug
should be forwarded upstream.