linux-kernel - Re: [PATCH] drm/radeon: Fix regression with suspend/resume

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Date:	Tue, 17 Feb 2015 10:49:06 -0700
From:	Ross Zwisler <ross.zwisler@...ux.intel.com>
To:	"Deucher, Alexander" <Alexander.Deucher@....com>
Cc:	Michel Dänzer <michel@...nzer.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	Dave Airlie <airlied@...hat.com>, Lauri Kasanen <cand@....com>,
	"Koenig, Christian" <Christian.Koenig@....com>
Subject: Re: [PATCH] drm/radeon: Fix regression with suspend/resume

On Sat, 2015-02-14 at 06:25 +0000, Deucher, Alexander wrote:
> > -----Original Message-----
> > From: Ross Zwisler [mailto:ross.zwisler@...ux.intel.com]
> > Sent: Friday, February 13, 2015 10:55 PM
> > To: Michel Dänzer
> > Cc: linux-kernel@...r.kernel.org; dri-devel@...ts.freedesktop.org; Deucher,
> > Alexander; Dave Airlie; Lauri Kasanen; Koenig, Christian
> > Subject: Re: [PATCH] drm/radeon: Fix regression with suspend/resume
> > 
> > On Fri, 2015-02-13 at 11:41 +0900, Michel Dänzer wrote:
> > > On 13.02.2015 05:30, Ross Zwisler wrote:
> > > > This patch reverts the changes made in this commit:
> > > >
> > > >   deadcb36f49b ("drm/radeon: Use two-ended allocation by size, v2")
> > > >
> > > > That patch caused a regression on my system where the bottom of the
> > > > screen flickers after my laptop goes thorough a suspend and resume.
> > >
> > > What kind of flicker is it? E.g. does it only affect X or also console,
> > > does it flicker all the time or only when there is activity, what does
> > > it look like, ...
> > 
> > It's kind of hard to describe it precisely, so I made a video.  :)
> > 
> > http://youtu.be/ESm9SMnr0do
> > 
> > It only affects X, not the console, and it seems to go away if you log
> > out back to the login manager (I'm using GDM on Fedora 20) and back into
> > your window manager.
> 
> Does a VT switch or forcing a dpms cycle (sleep 5; xset dpms force off)
> also fix it?  It doesn't look related to the patch in question at all. 
> Is the flickering 100% reproducible or does it only happen
> periodically?

>From kernels 3.14 or so (when the deadcb36f49b patch was introduced)
till 3.18 it happened 100% of the time.  With 3.19 it only seems to
happen maybe 50% of the time, but is still very easily reproducible.

It's entirely possible that the patch isn't the root cause, but it just
brought out a bug somewhere else.  All I know is that I did a bisect,
and with the commit before this the issue never happens, and after this
commit it happens 100% of the time. :)  Also, reverting that commit with
3.19 makes the issue go away.

Nope, "xset dpms force off" doesn't fix it. After the screen goes black
and comes back, the flicker is still there.

- Ross

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