[Intel-gfx] Bad flicker on skylake HQD due to code in the 4.7 merge window

[James Bottomley]

On Fri, 2016-06-17 at 16:34 +0300, Jani Nikula wrote:
> On Fri, 17 Jun 2016, Daniel Vetter <daniel at ffwll.ch> wrote:
> > On Thu, Jun 16, 2016 at 03:42:12PM -0700, James Bottomley wrote:
> > > On Thu, 2016-06-16 at 14:29 -0700, James Bottomley wrote:
> > > > On Thu, 2016-06-16 at 23:24 +0200, Daniel Vetter wrote:
> > > > > I guess we'll need the bisect on this one to make progress.
> > > > 
> > > > Sigh, I was afraid that might be the next step.
> > > 
> > > OK, I have a curious data point.  I assumed the problem would be
> > > somewhere in the drm update, so I started bisecting that at the
> > > top. 
> > >  However, the top most commit:
> > > 
> > > commit 1d6da87a3241deb13d073c4125d19ed0e5a0c62c
> > > Merge: 1f40c49 a39ed68
> > > Author: Linus Torvalds <torvalds at linux-foundation.org>
> > > Date:   Mon May 23 11:48:48 2016 -0700
> > > 
> > >     Merge branch 'drm-next' of
> > > git://people.freedesktop.org/~airlied/linux
> > > 
> > > Isn't actually bad.  There's no flicker here, so whatever caused
> > > the
> > > problem came from some update after this.
> > 
> > There was a fixes pull after this. Might be worth it to restrict to
> > just
> > the i915 changes, which are just
> > 5b4fd5b1111b1230cd037..157d2c7fad0863222
> > 
> > Looking at those nothing seems to stick out which might explain
> > what's
> > happening for you.

OK, so just on the firmware, the system seems less flickery with the
new 1.4.3 UEFI, so I'm starting to think it is a Skylake errata issue. 
 The flicker isn't gone for good, but seems to be reboot dependent
(it's there in some boots, but gone on a reboot).

> This should be easy enough to try before bisecting:
> http://patchwork.freedesktop.org/patch/msgid/1466162081-12042-1-git-s
> end-email-mika.kahola at intel.com

Applying this didn't seem to make a difference: still there on some and
gone on other reboots.

James