Video projector not detected anymore (under Xorg 1.18.4)

Philippe Dosch Philippe.Dosch at
Thu Nov 3 16:05:22 UTC 2016

Le 03/11/2016 à 16:12, Łukasz Maśko a écrit :
> Dnia czwartek, 3 listopada 2016 15:41:52 Philippe Dosch pisze:
>> Hi Folks,
>> I'm assistant professor and I teach with the same video projectors
>> since years (with each of the last three kubuntu releases on my
>> laptop). I have a strange trouble since my last kubuntu update (2
>> weeks ago). Now I'm under kubuntu 16.10, with a 1.18.4 Xorg server:
> Hello!
> I have exactly the same problem and it lies in the kernel itself, probably in
> i915 driver, not in X. The change was introuced in kernel 4.7.0, the last of
> the 4.6.x line (4.6.7) works fine. The changes deal with detection of external
> Display Port and as a result I get first an error like this:
> [drm:intel_dp_start_link_train [i915]] *ERROR* failed to update link training

Hi Dnia,

I have the same message several times at boot time (also found in
dmesg). But in my case, my troubles are related to the VGA port, not
the display port.

> at the kernel start (visible in dmesg). And then this output is not recognized
> anymore. I have filed a bug report

I saw your post, but it is related to the display port and I don't
know if the DP trouble makes some side effects with the VGA port.

> Maybe you can confirm it or append yours so we make developers fix this? I
> have no idea how to fix this myself. I'm just keeping kernel 4.6.7 to use when
> I want to do my presentations.

It's an idea, maybe I could downgrade to a 4.6.x kernel to see what happens.


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