[Bug 94471] Displayport monitor randomly disconnects

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=94471

Leho Kraav <leho at kraav.com> changed:

           What    |Removed                     |Added
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                 CC|                            |leho at kraav.com

--- Comment #3 from Leho Kraav <leho at kraav.com> ---
Kernel 3.19.3

I can confirm that similar things with that kernel error message is happening
here as well.

apr   08 12:25:10 papaya kernel: [drm:drm_dp_get_mst_branch_device.isra.17
[drm_kms_helper]] *ERROR* failed to lookup MSTB with lct 2, rad 00

I have an LG 27" 2560 http://www.lg.com/us/monitors/lg-27EA83-D-led-monitor
connected to DELL PR02X dock via DisplayPort.

* After docking the laptop, if the monitor was powered on and sitting in
standby, all xrandr activation attempts fail with "*ERROR* failed to lookup
MSTB with lct 2, rad 00"

* After docking the laptop, I always have to power cycle the monitor in order
for xrandr --output DP1-1-8 --auto to succeed. See above.


MST implementation has been very flaky from the time it was implemented, but I
do understand it's more like prototype stage thing still and not enough
resource is available to make it more bulletproof. I've been able to crash the
whole display system with just xrandr-based display connection management 
consistently, as in the screen goes completely blank with no way to bring it
back. Sucks a lot for being able to trust Linux with the basics, as a business
mobile desktop platform. Some more adventures for those interested
https://bugs.freedesktop.org/show_bug.cgi?id=85913

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