[Bug 94337] Linux 4.5 regression: FIFO underruns on Skylake

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=94337

--- Comment #10 from Andre Fredette <anfredette at gmail.com> ---
I'm having similar issues with a Skylake-based Lenovo T460s.  I'm using Fedora
24 with the latest updates:

$ uname -a
Linux gaston 4.7.5-200.fc24.x86_64 #1 SMP Mon Sep 26 21:25:47 UTC 2016 x86_64
x86_64 x86_64 GNU/Linux

I see the comment above about bug fixes over the past month, but this is a
fairly recent kernel, so I'm posting in case this is a good data point.

I see many errors like the following:

Oct 07 22:35:13 gaston kernel: [drm:intel_cpu_fifo_underrun_irq_handler [i915]]
*ERROR* CPU pipe C FIFO underrun
Oct 07 22:35:13 gaston kernel: [drm:intel_cpu_fifo_underrun_irq_handler [i915]]
*ERROR* CPU pipe B FIFO underrun
Oct 07 12:25:25 gaston kernel: [drm:intel_cpu_fifo_underrun_irq_handler [i915]]
*ERROR* CPU pipe A FIFO underrun

I've been seeing one or the other of my external monitors black out for about a
second, and then come back.  On a few occasions, the system has completely
frozen during one of these blackouts.

It also frequently freezes when left unattended, and always when the screens
are "blanked".  I've been able to prevent the system from freezing by changing
the Power->"Blank screen" setting to "Never".

When the system "freezes", the only way I've been able to recover is to hold
down the power button.

The issues only seem to happen when running with external monitors - I've never
had the system freeze problem when I haven't had external monitors.  For
example, I ran for a week recently without external monitors and without any
system freezes.

I did a full fresh install of Fedora about a week ago to see if that would
help.  I ran for a few days without issues, but then it started again.

I have no idea whether these error logs have anything to do with my system
freeze problems.

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