[Intel-gfx] Screen flicker regression on Baytrail

[Jani Nikula]

On Thu, 27 Oct 2016, Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com> wrote:
> While testing our upcoming HDMI audio patches, I experienced pretty bad 
> screen flicker regressions on my Baytrail compute stick. This happens 
> with both v09-rc2 and drm-intel-nightly.
>
> A quick bisect with all the audio patches removed points to the 
> following commit:
>
> 2efb813d5388e18255c54afac77bd91acd586908 is the first bad commit
> commit 2efb813d5388e18255c54afac77bd91acd586908
> Author: Chris Wilson <chris at chris-wilson.co.uk>
> Date:   Thu Aug 18 17:17:06 2016 +0100
>
>      drm/i915: Fallback to using unmappable memory for scanout
>
> More logs below. I don't have the background to fix this myself and I 
> don't see an obvious link with Baytrail but I hope someone smarter than 
> me can help fix this

Looking around, there's bug [1] with same culprit. Please follow up
there.

BR,
Jani.

[1] https://bugs.freedesktop.org/show_bug.cgi?id=98036


>
> -Pierre
>
>
> git bisect start
> # bad: [d8923dcfa53d59886d432a3fc430e26cb92ce86a] drm/i915: Track 
> display alignment on VMA
> git bisect bad d8923dcfa53d59886d432a3fc430e26cb92ce86a
> # good: [03af84fe7f48937941fbb4dcd6cf66c68ae0edd4] drm/i915: Choose 
> partial chunksize based on tile row size
> git bisect good 03af84fe7f48937941fbb4dcd6cf66c68ae0edd4
> # good: [50349247ea807ad0950bbcedb1abb576e6a785db] drm/i915: Drop 
> ORIGIN_GTT for untracked GTT writes
> git bisect good 50349247ea807ad0950bbcedb1abb576e6a785db
> # bad: [2efb813d5388e18255c54afac77bd91acd586908] drm/i915: Fallback to 
> using unmappable memory for scanout
> git bisect bad 2efb813d5388e18255c54afac77bd91acd586908
> # good: [821188778b9be2050d45490c4b2b009d51f041e0] drm/i915: Choose not 
> to evict faultable objects from the GGTT
> git bisect good 821188778b9be2050d45490c4b2b009d51f041e0
> # first bad commit: [2efb813d5388e18255c54afac77bd91acd586908] drm/i915: 
> Fallback to using unmappable memory for scanout
>
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-- 
Jani Nikula, Intel Open Source Technology Center