[Bug 98036] [BYT] constant screen flicker and rendering errors [regression]

[bugzilla-daemon at freedesktop.org]

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

Eero Tamminen <eero.t.tamminen at intel.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[BYT] flickering is seen    |[BYT] constant screen
                   |after running benchmark     |flicker and rendering
                   |synmark [regression]        |errors [regression]

--- Comment #4 from Eero Tamminen <eero.t.tamminen at intel.com> ---
There are several issues coming from this (not sure whether all come from same
commit, but at least they're caused by the commits surrounding the indicated
kernel commit):
* Desktop flickers so badly that it makes the device unusable.  At first the
screen may look OK, but after gfx has been used for a while, e.g. by running
glxgears, it goes black (and shows the real desktop only e.g. while switching
to virtual terminal and back)
* Lightsmark 2008 benchmark colors are wrong in some scenes
* Most SynMark tests are rendered wrong: screeen is divided to (approximately)
128 pixel high stripes which have different offsets

These issues happens *only on BYT*, BDW/BSW/SKL/HSW/SNB are not affected.

Triggering the issues requires *both*:
* kernel from this commit (18th August) or later, and
* modesetting driver or recent Intel DDX.

Issues happen with:
* Latest git version of modesetting built on Ubuntu 16.04 environment
* Modesetting version from Ubuntu 16.04 repos
* "Recent" Intel DDX built on Ubuntu 16.04 environment

However, issue isn't triggered when using older Intel DDX from Ubuntu 16.04:
  http://packages.ubuntu.com/xenial-updates/xserver-xorg-video-intel

(Ubuntu uses version 2.99.917+git20160325 with following patches applied:
- revert-dpms-fix.patch
- preserve-mouse-cursor-after-vt-switch.patch
- add-more-kbl-pciids.diff
- remove-invalid-kbl-pciids.diff
)

I tried bisecting with our pre-built binaries, whether there was some change in
Intel DDX that would trigger this but results are inconclusive because we had
build environment switch:
  1. Intel DDX built on Gentoo against dependencies pulled from X repositories
of that same time (22nd July) doesn't trigger the issue with new kernel (on
Ubuntu where the builds are tested)
  2. But same Intel DDX commit built against Ubuntu 16.04 does trigger the
issue
  3. However, X server / modesetting built in same environment as 1), does also
trigger the issue, so the second trigger (besides kernel) doesn't seem to be
just the build environment for Intel DDX

-> IMHO makes more sense to look into kernel.


Luis, can the indicated patch be reverted from latest kernel and if yes, does
that fix all the issues?

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