[Intel-gfx] Screen flicker regression on Baytrail

[Pierre-Louis Bossart]

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

-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