Message-ID: <20170110104301.rr2tc5p2kajbglsz@phenom.ffwll.local>
Date:   Tue, 10 Jan 2017 11:43:01 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Sean Paul <seanpaul@...omium.org>
Cc:     Peter Ujfalusi <peter.ujfalusi@...com>,
        freedesktop-bugs@...lsd.com, gleb@...tmail.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Daniel Vetter <daniel.vetter@...el.com>, stable@...r.kernel.org
Subject: Re: [PATCH v2] drm: Schedule the output_poll_work with 1s delay if
 we have delayed event

On Tue, Jan 10, 2017 at 11:40:59AM +0100, Daniel Vetter wrote:
> On Mon, Jan 09, 2017 at 11:50:59AM -0500, Sean Paul wrote:
> > On Mon, Jan 9, 2017 at 9:31 AM, Peter Ujfalusi <peter.ujfalusi@...com> wrote:
> > > Instead of scheduling the work to handle the initial delayed event, use 1s
> > > delay.
> > >
> > > This delay should not be needed, but Optimus/nouveau will fail in a
> > > mysterious way if the delayed event is handled as soon as possible like it
> > 
> > Has anyone tried to demystify the failure? It seems like fixing the
> > root problem would be better than this.
> 
> Peter is on it, but fixing the regression meanwhile has priority imo.
> 
> > Perhaps we should just revert 339fd36238dd to fix stable.
> 
> That will make people unhappy about the delay again, so I think 1s delay
> is the better option.

For the future: If you add an in-patch changelog then it'd would have been
clear that we discussed all this already. Also good to cc all previous
commenters when submitting a new version.
-Daniel

> 
> > 
> > Sean
> > 
> > > is done in drm_helper_probe_single_connector_modes() in case the poll
> > > was enabled before.
> > >
> > > Reverting 339fd36238dd would give back the 10 sec (!) delay to handle the
> > > delayed event. Adding 1sec delay to the poll_work is enough to work around
> > > the issue in Optimus setups and gives shorter response on handling the
> > > initial delayed event.
> > >
> > > Fixes: 339fd36238dd ("drm: drm_probe_helper: Fix output_poll_work scheduling")
> > > Cc: stable@...r.kernel.org   # v4.9
> > > Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>
> > > ---
> > >  drivers/gpu/drm/drm_probe_helper.c | 10 +++++++++-
> > >  1 file changed, 9 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
> > > index 06a62e37fbdc..258abed43e38 100644
> > > --- a/drivers/gpu/drm/drm_probe_helper.c
> > > +++ b/drivers/gpu/drm/drm_probe_helper.c
> > > @@ -146,8 +146,16 @@ void drm_kms_helper_poll_enable_locked(struct drm_device *dev)
> > >         drm_connector_list_iter_put(&conn_iter);
> > >
> > >         if (dev->mode_config.delayed_event) {
> > > +               /*
> 
> I added a FIXME: heading here to make it stick out more, and then applied
> the patch.
> 
> Thanks, Daniel
> 
> > > +                * Use short (1s) delay to handle the initial delayed event.
> > > +                * This delay should not be needed, but Optimus/nouveau will
> > > +                * fail in a mysterious way if the delayed event is handled as
> > > +                * soon as possible like it is done in
> > > +                * drm_helper_probe_single_connector_modes() in case the poll
> > > +                * was enabled before.
> > > +                */
> > >                 poll = true;
> > > -               delay = 0;
> > > +               delay = HZ;
> > >         }
> > >
> > >         if (poll)
> > > --
> > > 2.11.0
> > >
> > 
> > 
> > 
> > -- 
> > Sean Paul, Software Engineer, Google / Chromium OS
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@...ts.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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