Re: Bug#909770: i915: Does not show gdm greeter on eDP: Link Training failed at link rate = 270000, lane count = 2
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
On Wed, 10 Oct 2018 at 13:22:37 +0200, Sergio Villar Senin wrote:
> 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
kernel/graphics maintainers:
Original bug report:
> 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
Most relevant-looking log message:
> laptop kernel: [drm:intel_dp_start_link_train [i915]] *ERROR*
> [CONNECTOR:71:eDP-1] Link Training failed at link rate = 270000, lane
> count = 2
Workaround (presumably suspend/resume retries link training):
> BTW I noticed that it is possible to enter the session by following the
> next steps:
> 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
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