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

[Steven Newbury]

On Thu, 2016-06-23 at 15:59 +0300, Jani Nikula wrote:
> On Thu, 23 Jun 2016, Steven Newbury <steve at snewbury.org.uk> wrote:
> > [ Unknown signature status ]
> > On Sun, 2016-06-19 at 14:53 -0700, James Bottomley wrote:
> > > On Fri, 2016-06-17 at 16:06 -0700, James Bottomley wrote:
> > > > 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-g
> > > > > it
> > > > > -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.
> > > 
> > > OK, my candidate bad commit is this one:
> > > 
> > > commit a05628195a0d9f3173dd9aa76f482aef692e46ee
> > > Author: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > > Date:   Mon Apr 11 10:23:51 2016 +0300
> > > 
> > >     drm/i915: Get panel_type from OpRegion panel details
> > > 
> > > After being more careful about waiting to identify flicker, this
> > > one
> > > seems to be the one the bisect finds.  I'm now running v4.7-rc3
> > > with
> > > this one reverted and am currently seeing no flicker
> > > problems.  It
> > > is,
> > > however, early days because the flicker can hide for long
> > > periods, so
> > > I
> > > 'll wait until Monday evening and a few reboots before declaring
> > > victory.
> > > 
> > >  
> > I'm seeing this on my IvyBridge.  I'll try reverting the commit
> > here
> > too, to see if it's the same issue.
> 
> IvyBridge doesn't have low vswing for eDP. If reverting helps, it's a
> different failure mode.
> 
It must be something else then.  Actually, in my case linus/master is
okay.  I saw the subject and though it must be the same issue.  I'm
seeing it with drm-intel nightly/next branches.  Shall I try to bisect
it?  Symptoms are similar, although I would describe it more like
flashes of a different buffer across parts of the screen.


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