[Bug 94593] Flickering Screen on Dell XPS13 9350

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=94593

--- Comment #44 from Peter Y. Chuang <peteryuchuang at gmail.com> ---
(In reply to nhellwege from comment #43)
> (In reply to tranceash from comment #38)
> > looks like a power management issues dating 8 months back, Also happened on
> > the broadwell systems https://bugs.freedesktop.org/show_bug.cgi?id=91393.
> > This makes any linux system a pain to work because of this integrated gpu
> > driver . Skylake has been out for 7 months and we still have problems
> 
> I am starting to believe that the common error 
> 
>  [drm:intel_cpu_fifo_underrun_irq_handler [i915_bpo]] *ERROR* CPU pipe A
> FIFO underrun
> 
> is not actually responsible for the flicker. To be more precise, the FIFO
> underrun may result in conjunction with a flicker, but is not a unique
> indication. I am currently bisecting the kernel and right now I am on commit
> 5ffd4da+. This commit does show the FIFO underun but not at the same time
> the screen turns completely black for a split second. 
> 
> I assume the flicker (screen completely black for a split second) is not
> directly mapped by the FIFO underrun. 
> 
> Reading https://bugs.freedesktop.org/show_bug.cgi?id=91393, I think our bug
> is at least related, if not identical.

I tend to agree with you that the error 

[drm:intel_cpu_fifo_underrun_irq_handler [i915_bpo]] *ERROR* CPU pipe A FIFO
underrun

may not be specific to the problem we are talking about here.

Regarding my previous comment on whether the laptop is plugged into AC, Thomas
is right: if I wait long enough, the flicker does occur even when plugged in,
although much less frequent on my machine. 

Interestingly, now that I am plugged into AC, the CPU pipe A FIFO underrun
thing is no longer the error I see. Instead, this is the error I saw on dmesg:

[ 2045.481992] [drm:intel_pipe_update_end [i915]] *ERROR* Atomic update failure
on pipe A (start=84070 end=84071) time 9 us, min 1073, max 1079, scanline start
1087, end 1079

This is the first time I see this error since I started looking for the
solution for this problem.

Hope this might give you some clues.

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