[Bug 1716857] Re: nvidia-drm.modeset=1, gdm3 and optimus laptop results in no external monitors detected by Xorg

Sun May 3 14:23:00 UTC 2020

Another correction. For the one workaround, switching to discrete
graphics in the BIOS only seemed to get past the initial gnome login.
But resuming from DPMS off/suspend, the same error loop happens even
when hybrid graphics is disabled in the BIOS.

Even worse, seems hardware acceleration ends up being disabled:

$ journalctl --no-hostname -b -p warning _COMM=gnome-shell
-- Logs begin at Wed 2019-02-06 14:13:52 SAST, end at Sun 2020-05-03 16:09:45 SAST. --
May 03 14:51:40 org.gnome.Shell.desktop[2284]: glamor: 'wl_drm' not supported
May 03 14:51:40 org.gnome.Shell.desktop[2284]: Missing Wayland requirements for glamor GBM backend
May 03 14:51:40 org.gnome.Shell.desktop[2284]: Failed to initialize glamor, falling back to sw
...
May 03 14:53:25 gnome-shell[6549]: setup_framebuffers: assertion 'width > 0' failed

The "EGL failed to allocate resources" error stops happening probably
because gnome-shell isn't even using hardware acceleration now.

I've also disabled all gnome shell extensions to avoid noise/errors in
the logs and will try weed out the problem better.

I checked `grep -C2 -E '(EE)|(WW)' /var/log/Xorg.0.log` and things seem
fine:

[    45.181] (II) NVIDIA dlloader X Driver  440.59  Thu Jan 30 01:08:17 UTC 2020
[    45.181] (II) NVIDIA Unified Driver for all Supported NVIDIA GPUs
--
[    45.182] (II) LoadModule: "ramdac"
[    45.182] (II) Module "ramdac" already built-in
[    45.183] (WW) Falling back to old probe method for modesetting
[    45.183] (II) NVIDIA(0): Creating default Display subsection in Screen section
	"Default Screen Section" for depth/fbbpp 24/32
--
[    46.392] (==) NVIDIA(0): Silken mouse enabled
[    46.392] (==) NVIDIA(0): DPMS enabled
[    46.393] (WW) NVIDIA(0): Option "PrimaryGPU" is not used
[    46.393] (II) Loading sub module "dri2"
[    46.393] (II) LoadModule: "dri2"

Note, I've done no customisation to X config - trying to stick to
defaults.

xrandr confirms only one provider / hybrid is indeed off and Intel not
in use:

$ xrandr --listproviders 
Providers: number : 1
Provider 0: id: 0x218 cap: 0x1, Source Output crtcs: 4 outputs: 6 associated providers: 0 name:NVIDIA-0

I'm guessing the Lenovo P53 impliments a mux/switch to connect the
laptop panel to the NVidia card so that Intel is disabled in this mode.

And double checking, also no i915 modules are loaded:

$ lsmod | grep '^drm'
drm_kms_helper        180224  1 nvidia_drm
drm                   491520  10 drm_kms_helper,nvidia_drm

So there seems to be, on current Ubuntu 18.04.4 LTS (fully up to date as
of today), a 4K / UHD 60Hz issue with Nvidia, as seen in X log

[    45.228] (II) NVIDIA GLX Module  440.59  Thu Jan 30 01:05:38 UTC
2020

Lastly, I think due to `needs_root_rights=yes` in
/etc/X11/Xwrapper.config, X logs to /var/log/Xorg.0.log again instead of
the X without root which used to log at  ~/.local/share/xorg/Xorg.0.log

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https://bugs.launchpad.net/bugs/1716857

Title:
  nvidia-drm.modeset=1, gdm3 and optimus laptop results in no external
  monitors detected by Xorg

Status in gdm3 package in Ubuntu:
  Opinion
Status in nvidia-graphics-drivers-375 package in Ubuntu:
  Confirmed
Status in nvidia-graphics-drivers-418 package in Ubuntu:
  Confirmed
Status in nvidia-graphics-drivers-430 package in Ubuntu:
  Confirmed
Status in nvidia-graphics-drivers-435 package in Ubuntu:
  Confirmed
Status in systemd package in Ubuntu:
  Confirmed

Bug description:
  Context:
  17.10 development packages, nvidia binary driver 375, modeset=1 for the nvidia driver.
  ubuntu desktop (gnome shell), fresh install
  ThinkPad W520 in Nvidia Optimus bios mode.
  Nvidia profile.

  Result:
  no external monitors are detected.
  xrandr does not even list them as disconnected (normally it would list five external disconnected monitors)

  lsmod 
  shows that nvidia driver is loaded
  and the modesetting is working at some level because there is no tearing on the laptop panel

  Note: modeset=1 is the only way to get flicker-free graphics on the laptop panel. modeset=1 is not the default setting but it is highly desirable. 

  It works if lightdm is used which is why I have reported this against gdm3
  My sessions in this configuration have mostly crashed after a few minutes with a gdm3 fail whale message in syslog but nothing else looks interesting.

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