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

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Message-ID: <20160617081218.GY6754@nuc-i3427.alporthouse.com>
Date:	Fri, 17 Jun 2016 09:12:18 +0100
From:	Chris Wilson <chris@...is-wilson.co.uk>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
Cc:	Daniel Vetter <daniel@...ll.ch>,
	intel-gfx <intel-gfx@...ts.freedesktop.org>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [Intel-gfx] Bad flicker on skylake HQD due to code in the 4.7
 merge window

On Thu, Jun 16, 2016 at 02:29:07PM -0700, James Bottomley wrote:
> On Thu, 2016-06-16 at 23:24 +0200, Daniel Vetter wrote:
> > On Thu, Jun 16, 2016 at 11:15 PM, James Bottomley
> > <James.Bottomley@...senpartnership.com> wrote:
> > > On Mon, 2016-06-13 at 13:14 +0300, Jani Nikula wrote:
> > > > On Tue, 31 May 2016, James Bottomley <
> > > > James.Bottomley@...senPartnership.com> wrote:
> > > > > On Tue, 2016-05-31 at 10:51 +0300, Jani Nikula wrote:
> > > > > > On Mon, 30 May 2016, James Bottomley <
> > > > > > James.Bottomley@...senPartnership.com> wrote:
> > > > > > > I've tested a pristine 4.6.0 system, so it's definitely
> > > > > > > something
> > > > > > > that
> > > > > > > went in during the merge window.  The flicker isn't
> > > > > > > continuous,
> > > > > > > it's
> > > > > > > periodic, with an interval of something like 2-5 seconds. 
> > > > > > >  It
> > > > > > > looks
> > > > > > > like an old analogue TV going out of sync and then
> > > > > > > resyncing.
> > > > > > >  I've
> > > > > > > attached the dmesg and X.org log below just in case they
> > > > > > > can
> > > > > > > help.
> > > > > > >  I
> > > > > > > might be able to bisect this next week, but, unfortunately,
> > > > > > > this is
> > > > > > > my
> > > > > > > current laptop and I'm travelling this week.
> > > > > > 
> > > > > > Please try i915.enable_psr=0 module parameter.
> > > > > 
> > > > > Makes no discernable difference.  Current parameter settings
> > > > > are:
> > > > 
> > > > Sorry for the silence. Would you mind trying out drm-intel
> > > > -nightly
> > > > branch of [1]?
> > > > 
> > > > BR,
> > > > Jani.
> > > > 
> > > > [1] http://cgit.freedesktop.org/drm-intel
> > > 
> > > No, flicker is still there (and in fact seems worse) with the tree
> > > with
> > > this commit at the top:
> > > 
> > > commit 3eb202ecc3668583f9ff4338211dbab47d755d1c
> > > Author: Daniel Vetter <daniel.vetter@...ll.ch>
> > > Date:   Thu Jun 16 14:38:54 2016 +0200
> > > 
> > >     drm-intel-nightly: 2016y-06m-16d-12h-38m-37s UTC integration
> > > manifest
> > 
> > Strange indeed, I hoped the improved watermark code in -nightly would
> > help. I assume nothing in dmesg about underruns or something similar?
> 
> Not that I can tell.  I've attached the full dmesg just in case.

It is worth using drm.debug=0xe to get the full atomic modesetting
splat. There may be a tell-tale in there that we don't yet have a
warning for.
-Chris
>
-- 
Chris Wilson, Intel Open Source Technology Centre