[Bug 105998] [CI][SKL only] igt@* - dmesg-warn - *ERROR* failed to enable link training

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=105998

--- Comment #4 from Martin Peres <martin.peres at free.fr> ---
(In reply to Chris Murphy from comment #3)
> Created attachment 141573 [details]
> dmesg, drm.debug=0xe
> 
> I'm seeing this on
> 
> 00:02.0 VGA compatible controller [0300]: Intel Corporation Skylake GT2 [HD
> Graphics 520] [8086:1916] (rev 07) (prog-if 00 [VGA controller])
> 	Subsystem: Hewlett-Packard Company Device [103c:81a0]
> 
> 
> [12446.213836] f29h.local kernel: [drm:intel_dp_start_link_train [i915]]
> *ERROR* failed to enable link training
> [12446.213959] f29h.local kernel: [drm:intel_dp_start_link_train [i915]]
> [CONNECTOR:79:DP-1] Link Training failed at link rate = 162000, lane count =
> 4
> [12446.214211] f29h.local kernel: [drm:intel_dp_modeset_retry_work_fn
> [i915]] [CONNECTOR:79:DP-1]
> 
> 
> 4.19.0-0.rc3.git2.1.fc30.x86_64 which is git 54eda9df17f3.
> 
> 
> So far it's only happening on wake from S3, possibly the connected external
> display itself hasn't come out of power save at the initial link training?
> Subsequent link training appears to be OK.
> 
> On the primary display at about this time (hard to say), there is a flicker
> at GDM (GNOME login). I can't tell if it's related.

Thanks for this detailed report Chris, I am pulling in Manasi who has been
developing this feature. She should be able to tell us for sure if your
sensible explanation is sound, and how we could fix this.

However, I would recommend writing a new bug report, given that not all link
training failures stem from the same root cause. Since our failing tests are
not S3-related, you likely experience a separate issue that is best handled in
a separate bug.

In any case, how much impact this issue has for you? This is important for us
to prioritise bugs.

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