[Intel-gfx] Kernel Error: [drm:intel_cpu_fifo_underrun_irq_handler [i915]]

[Max Biegert]

Hello!

I've been recently scouring through journalctl because of another error
and found this kernel error multiple times:

Nov 09 17:49:35 Leonidas kernel:
[drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe A
FIFO underrun

They started happening around beginning of November 2018 and occur
without further kernel messages around them. They also happen very
irregularly and there is no visible sign (as screen flickering or
similar) of the error.

I have a Lenovo T470p (Kaby Lake with discrete Nvidia 940MX card)
running Arch Linux with gnome on wayland and currently xf86-video-intel 
version 2.99.917+860+g3a2dec17. The appearance of the error messages
sort of match with the update of xf86-video-intel from version
2.99.917+847+g25c9a2fc to 2.99.917+853+g0932a6b3 end of October 2018.

I've seen on the bug tracker[1] that there are multiple open issues
where this kernel error appears, but I do not see any visual signs so I
don't know where this belongs. I do not use any external monitors,
though.

As I do not have any impairements of usability I consider this low
priority, but if I can be of any assistance, let me know.


Output of
journalctl -p err | grep "drm:intel_cpu" | wc
--> 29 occurences
The first occurence was on Nov 2 2018.

In the attachment you can see two possibly interesting kernel messages
around the error, although the second one is around a different error:
Dec 15 21:55:19 Leonidas kernel: [drm:intel_dp_start_link_train [i915]]
*ERROR* failed to enable link training
This error occured only twice mid Decembre.


If I can help with this report or should post it somewhere else, please
let me know.

Kind regards,
Max


[1] 
https://bugs.freedesktop.org/buglist.cgi?quicksearch=CPU%20fifo%20underrun

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