[Intel-gfx] 5.6 DP-MST regression: 1 of 2 monitors on TB3 (DP-MST) dock no longer light up

[Alex Deucher]

On Wed, Feb 26, 2020 at 10:16 AM Hans de Goede <hdegoede at redhat.com> wrote:
>
> Hi Lyude and everyone else,
>
> Lyude I'm mailing you about this because you have done a lot of
> work on DP MST, but if this rings a bell to anyone else feel
> free to weigh in on this.

Might be a duplicate of:
https://gitlab.freedesktop.org/drm/amd/issues/1052

Alex

>
> I'm currently using a Lenovo X1 7th gen + a Lenovo TB3 gen 2 dock
> as my daily rider for testing purposes. When 5.6-rc1 came out I
> noticed that only 1 of the 2 1920x1080 at 60 monitors on the dock
> lights up.
>
> There are no kernel errors in the logs, but mutter/gnome-shell says:
>
> gnome-shell[1316]: Failed to post KMS update: Page flip of 93 failed
>
> With 93 being the crtc-id of the crtc used for the monitor which is
> displaying black. Since then I've waited for 5.6-rc3 hoping that a
> fix was already queued up, but 5.6-rc3 still has this problem.
>
> gnome-shell does behave as if all monitors are connected, so the
> monitor is seen, but we are failing to actually send any frames
> to it.
>
> I've put a log collected with drm.debug=0x104 here:
> https://fedorapeople.org/~jwrdegoede/drm-debug.log
>
> This message stands out as pointing to the likely cause of this problem:
>
> [    3.309061] [drm:intel_dump_pipe_config [i915]] MST master transcoder: <invalid>
>
> Regards,
>
> Hans
>
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