[Bug 95176] LCD flickering on Thinkpad T440p (Haswell) with kernel 4.6-rc4 (PSR enabled)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=95176

--- Comment #36 from Dmitry Nezhevenko <dion at dion.org.ua> ---
It looks like something very strange happens. I'm not sure whether it's caused
by patches or it's just mainline 4.6.2 behavior. 

I've docked my t440p laptop to dock with external monitor connected and
configured internal eDP as secondary.

And got followed: https://youtu.be/kfiqEOpQ1do

So I'm getting flickering on external monitor. But when I'm displaying watch -n
0.1 cat /sys/kernel/debug/dri/0/i915_edp_psr_status everything seems to be ok.

Also when I'm typing something flickering stops for a while.

dmesg contains followed:
[23279.278108] [drm:intel_set_cpu_fifo_underrun_reporting [i915]] *ERROR*
uncleared fifo underrun on pipe B
[23279.278119] [drm:ironlake_irq_handler [i915]] *ERROR* CPU pipe B FIFO
underrun
[23393.451412] [drm:intel_set_cpu_fifo_underrun_reporting [i915]] *ERROR*
uncleared fifo underrun on pipe B
[23393.451422] [drm:ironlake_irq_handler [i915]] *ERROR* CPU pipe B FIFO
underrun

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