[PATCH] drm: allow changing DPMS mode for non-CRTC displays

[Eric Engestrom]

On Thursday, 2016-12-01 14:15:05 +0000, Chris Wilson wrote:
> On Thu, Dec 01, 2016 at 03:30:01PM +0200, Marta Lofstedt wrote:
> > For non-CRTC displays,
> 
> A connector not attached to a CRTC works. It is the active connectors
> that were broken.
> 
> > the drm_atomic_helper_connector_dpms
> > will always set the connector back the old DPMS state
> > before returning. This makes it impossible to change
> > DPMS state.
> > 
> > fixes: 0853695c3ba46f97dfc0b5885f7b7e640ca212dd
> > 
> > Signed-off-by: Marta Lofstedt <marta.lofstedt at intel.com>
> > ---
> >  drivers/gpu/drm/drm_atomic_helper.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> > index 494680c..6a5acb9 100644
> > --- a/drivers/gpu/drm/drm_atomic_helper.c
> > +++ b/drivers/gpu/drm/drm_atomic_helper.c
> > @@ -2885,8 +2885,8 @@ int drm_atomic_helper_connector_dpms(struct drm_connector *connector,
> >  fail:
> >  	if (ret == -EDEADLK)
> >  		goto backoff;
> > -
> > -	connector->dpms = old_mode;
> > +	if (ret != 0)
> > +		connector->dpms = old_mode;
> 
> Patch however is correct.
> 
> Fix the subject line to reflect the impact correctly, amend the fixes
> tag and add the appropriate CCs
> 
> Fixes: 0853695c3ba4 ("drm: Add reference counting to drm_atomic_state")
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> Cc: Eric Engestrom <eric.engestrom at imgtec.com>

Good catch!
Reviewed-by: Eric Engestrom <eric.engestrom at imgtec.com>

I just had another look at the change (0853695c3ba4) and I don't believe
there was any other unintended behaviour change.

> Cc: Sean Paul <seanpaul at chromium.org>
> Cc: dri-devel at lists.freedesktop.org
> Cc: <drm-intel-fixes at lists.freedesktop.org>
> 
> And mention if there was a testcase exercising the failure. If not
> please suggest one.
> -Chris
> 
> -- 
> Chris Wilson, Intel Open Source Technology Centre