[Bug 97596] [SKL] [regression] Flickering artefact window at top left of screens in kernel 4.8-rc5

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=97596

yann <yann.argotti at intel.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      i915 platform|                            |SKL
      i915 features|                            |display/watermark

--- Comment #1 from yann <yann.argotti at intel.com> ---
(In reply to rockorequin from comment #0)
> Created attachment 126212 [details]
> syslog for 4.8-rc5
> 
> I am seeing a flickering artefact window at the top left of my monitors when
> I use 4.8-rc4 and -rc5 on my Skylake GPU using the modeset driver in Ubuntu
> 16.10 on an XPS 15 9550.
> 
> The artefact looks a bit like a small black gnome-terminal window with white
> text inside at the top left of the monitor (it's not the same as my actual
> gnome-terminal window, which has orange text in it) and flickers rapidly in
> and out of existence for maybe half a second to a second when it is
> triggered.
> 
> I see the the artefact at the top of both my HDMI external monitor and the
> laptop internal monitor (I have them set up with the external monitor on
> top, in case that's relevant). IIRC it appears on the display where the
> mouse is currently.
> 
> I find it is triggered reasonably consistently by moving the mouse between
> monitors or by clicking on a gnome-terminal window to focus it and then
> pressing a key.
> 
> It makes the desktop unusable so I would rate it higher than normal (for me
> it's a blocker).
> 
> The artefact wasn't present in kernels 4.4 through 4.7.
> 
> I can't see anything in particular in the log (attached) that is related to
> the flickering. drm logs some CPU buffer underrun messages and also one
> saying "GuC firmware load skipped", which doesn't happen with kernel 4.7.2.
> 
> I don't think this is bug
> https://bugs.freedesktop.org/show_bug.cgi?id=97450, because that one seems
> to be talking about full-screen flickering and there it occurs randomly and
> only on the external monitor.
> 
> I think the artefact I'm seeing is mentioned in
> https://bugs.freedesktop.org/show_bug.cgi?id=97242 (comment 6), but that bug
> was primarily about another issue and has been closed.

One can see in your log several issues on multiple components that you may
consider to resolve also, but regarding graphic, the following could be linked
to flickering :
Sep  5 11:17:44 xps15-9550 kernel: [   16.307746] [drm:gen8_irq_handler [i915]]
*ERROR* CPU pipe A FIFO underrun

Sep  5 11:18:55 xps15-9550 kernel: [   86.939567] [drm:gen8_irq_handler [i915]]
*ERROR* CPU pipe B FIFO underrun

Sep  5 11:20:12 xps15-9550 kernel: [  164.003111] [drm:gen8_irq_handler [i915]]
*ERROR* CPU pipe A FIFO underrun

So, there is chance that it is dup of bug 97450, and therefore can you confirm
if, without any external display connected, it is occurring on your laptop
display?

Moreover, add drm.debug=0xe on the boot command line and then attached new
kernel log

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