[Bug 107724] [CI][DRMTIP] igt@* - dmesg-warn / dmesg-fail - *ERROR* CPU pipe [ABC] FIFO underrun

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=107724

--- Comment #3 from Paulo Zanoni <przanoni at gmail.com> ---
Submitted https://patchwork.freedesktop.org/series/50579/ but I'm not sure it
will solve the problem.

I was looking at the logs for fi-icl-u and it seems that sometimes during boot
the interrupts just act like crazy: either you get a ton of interrupts, or the
IIR registers are unclearable and contain crazy values, with even reserved bits
set. I simply can't reproduce this type of problem you're seeing. Example:

https://intel-gfx-ci.01.org/tree/drm-tip/drmtip_115/fi-icl-u/boot3.log

This could be some memory corruption happening, or it could simply be a bad
BIOS.

Another thing that was brought to my attention is that we often get the
mysterious crazy interrupts right after enabling DMC. Would it be possible to
run a few tests with DMC disabled? The CI pages suggest the problem happens
only around 11% of the time, so a few rounds of tests would probably be needed
:/

Perhaps giving me remote access to the machine would also help us move forward
a little faster.

Thanks,
Paulo

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