[PATCH v2] drm: Schedule the output_poll_work with 1s delay if we have delayed event

[Daniel Vetter]

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 at ti.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.

> 
> 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 at vger.kernel.org   # v4.9
> > Signed-off-by: Peter Ujfalusi <peter.ujfalusi at ti.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
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch