linux-kernel - Re: [git pull] drm for v4.8

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Date:	Tue, 2 Aug 2016 11:10:42 +0300
From:	Ville Syrjälä <ville.syrjala@...ux.intel.com>
To:	Daniel Vetter <daniel@...ll.ch>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Daniel Vetter <daniel.vetter@...el.com>,
	DRI mailing list <dri-devel@...ts.freedesktop.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [git pull] drm for v4.8

On Tue, Aug 02, 2016 at 10:00:12AM +0200, Daniel Vetter wrote:
> On Tue, Aug 2, 2016 at 4:26 AM, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> > On Mon, Aug 1, 2016 at 9:32 PM, Dave Airlie <airlied@...ux.ie> wrote:
> >>
> >> This is the main drm pull request for 4.8, I'm down with a cold at the moment
> >> so hopefully this isn't in too bad a state, I finished pulling stuff last
> >> week mostly (nouveau fixes just went in today), so only this message should
> >> be influenced by illness. Apologies to anyone who's major feature I missed :-)
> >>
> >> i915:
> >>         BXT support enabled by default
> >>         GVT-g infrastructure
> >>         GuC command submission and fixes
> >>         BXT workarounds
> >>         SKL/BKL workarounds
> >>         Demidlayering device registration
> >>         Thundering herd fixes
> >>         Missing pci ids
> >>         Atomic updates
> >
> > Hmm. I did the merge and pushed it out, but testing it on my laptop
> > shows some very annoying flickering problem.
> >
> > The screen goes dark for a very short while (one frame? Who knows?
> > Seems longer occasionally). I have no idea what triggers it, but it
> > happens quite a lot when it happens. Like once every second or two.
> > And it seems to happen most of the time, although right now it happens
> > to be behaving nicely, so sometimes it goes for a while without the
> > flickering.
> >
> > Things *work*, but the flickering is nasty enough to make the end
> > result painful to use.
> >
> > The only thing I see in dmesg that looks bad is
> >
> >    [drm:intel_set_cpu_fifo_underrun_reporting [i915]] *ERROR*
> > uncleared fifo underrun on pipe A
> >    [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe A
> > FIFO underrun
> >
> > but I've seen that before, and it happens a couple of times during
> > boot. Not once per second.
> >
> > This is my old Vaio 11 Pro, now running Fedora 24 (up-to-date as of today).
> >
> > So it's bog-standard intel graphics (i5-4200U - Haswell ULT).
> >
> > Suggestions to try?
> 
> psr or fbc are the likely culprits. More likely fbc if the underruns
> correlate with the flicker (but note that by default we only report
> them once per modest, needs to be reset with a dpms or
> suspend/resume). Driver should even pick up the new module option
> settings at runtime (but again you need to force a modeset, just
> suspend/resume quickly), so fast to test.

I think FBC is still disabled by default on HSW.

So PSR seems more likely. The underruns might point at some watermark
fail though :(

I have a couple of pending PSR patches you may want to try as well,
if i915.enable_psr=0 helps.

First set is here:
git://github.com/vsyrjala/linux.git psr_setup_time_2
This should be perfectly safe to go in actually, as it will only result
in disabling PSR with certain panels.

The second set is here:
git://github.com/vsyrjala/linux.git psr_fixes_2
This one I think is causing some kind of slight regression on one
machine in our CI system. Still not sure what's going on there.

-- 
Ville Syrjälä
Intel OTC