Bug#909770: i915: Does not show gdm greeter on eDP: Link Training failed at link rate = 270000, lane count = 2

[Simon McVittie]

Control: retitle 909770 i915: Does not show gdm greeter on eDP: Link Training failed at link rate = 270000, lane count = 2
Control: severity 909770 important
Control: reassign 909770 src:linux
Control: affects 909770 gdm3

Note that I've reproduced today this very same issue with lightdm as
well, so I guess this is the confirmation that the bug is somewhere
else. Graphics drivers maybe?

Yes, this sounds like a graphics driver problem. Summarizing for

Boot the computer, then wait for the login screen (gdm) to appear.
The background of the plyumouth theme is shown but the list of
users is not there as expected.
Sometimes I press the power button and the system suspends to
RAM. When resuming then the gdm login screen is there, *but* if I try to
enter any session (GNOME) it does not work. The authentication seems
to succeed but then the screen becomes blank and there is no
possibility to even switch to the terminals via Ctr-Alt-Fx.

Logs: https://pastebin.com/PiwQdiR2 and
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=909770#17

laptop kernel: [drm:intel_dp_start_link_train [i915]] *ERROR*
[CONNECTOR:71:eDP-1] Link Training failed at link rate = 270000, lane
count = 2
BTW I noticed that it is possible to enter the session by following the
1- Boot
2- Nothing is shown. Press power button to suspend
3- Resume laptop. gdm is shown
4- Enter credentials. Succeeds.
5- Nothing is shown. Press power button to suspend
6- Resume laptop. GNOME session is opened and working normally

Disabling Wayland in gdm does not work around this. Switching to lightdm
works around this (presumably it chooses video modes in a way that does
not exactly match GNOME?), but not entirely reliably.

smcv

[Sergio Villar Senin]

I think this patch[1] might potentially fix it. I'd love to give it a
try since I suffer this issue in many different situations (normal
startup, attaching external monitors, random flickers...).

BR

[1] https://bugs.freedesktop.org/show_bug.cgi?id=105267

Post by Simon McVittie
Control: retitle 909770 i915: Does not show gdm greeter on eDP: Link
Training failed at link rate = 270000, lane count = 2
Control: severity 909770 important
Control: reassign 909770 src:linux
Control: affects 909770 gdm3

Note that I've reproduced today this very same issue with lightdm as
well, so I guess this is the confirmation that the bug is somewhere
else. Graphics drivers maybe?

Yes, this sounds like a graphics driver problem. Summarizing for

Boot the computer, then wait for the login screen (gdm) to appear.
The background of the plyumouth theme is shown but the list of
users is not there as expected.
Sometimes I press the power button and the system suspends to
RAM. When resuming then the gdm login screen is there, *but* if I try to
enter any session (GNOME) it does not work. The authentication seems
to succeed but then the screen becomes blank and there is no
possibility to even switch to the terminals via Ctr-Alt-Fx.

Logs: https://pastebin.com/PiwQdiR2 and
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=909770#17

laptop kernel: [drm:intel_dp_start_link_train [i915]] *ERROR*
[CONNECTOR:71:eDP-1] Link Training failed at link rate = 270000, lane
count = 2
BTW I noticed that it is possible to enter the session by following the
1- Boot
2- Nothing is shown. Press power button to suspend
3- Resume laptop. gdm is shown
4- Enter credentials. Succeeds.
5- Nothing is shown. Press power button to suspend
6- Resume laptop. GNOME session is opened and working normally

Disabling Wayland in gdm does not work around this. Switching to lightdm
works around this (presumably it chooses video modes in a way that does
not exactly match GNOME?), but not entirely reliably.
smcv