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

From	Sergio Villar Senin <svillar@igalia.com>
Newsgroups	linux.debian.bugs.dist, linux.debian.kernel
Subject	Bug#909770: i915: Does not show gdm greeter on eDP: Link Training failed at link rate = 270000, lane count = 2
Date	2018-10-17 10:40 +0200
Message-ID	<wJPwZ-6V7-1@gated-at.bofh.it> (permalink)
References	<wCLRv-8cd-7@gated-at.bofh.it> <wHkQG-7HJ-9@gated-at.bofh.it> <wHlto-89s-5@gated-at.bofh.it> <wCLRv-8cd-7@gated-at.bofh.it> <wHlto-89s-5@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Cross-posted to 2 groups.

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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 

O Mér, 10-10-2018 ás 13:01 +0100, Simon McVittie escribiu:
> 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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Bug#909770: i915: Does not show gdm greeter on eDP: Link Training failed at link rate = 270000, lane count = 2 Sergio Villar Senin <svillar@igalia.com> - 2018-10-17 10:40 +0200

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