[PATCH] drm/exynos: only run atomic_check() if crtc is active

[Daniel Vetter]

On Thu, Nov 12, 2015 at 02:49:29PM +0100, Thierry Reding wrote:
> On Thu, Nov 12, 2015 at 11:11:20AM -0200, Gustavo Padovan wrote:
> > From: Gustavo Padovan <gustavo.padovan at collabora.co.uk>
> > 
> > Fixes an regression added by 3ae2436 (drm/exynos/mixer: replace
> > direct cross-driver call with drm mode). The whole atomic update
> > was failing if the hdmi display is not present/active. Add a test
> > to only run atomic_check() if the CRTC is active.
> > 
> > Signed-off-by: Gustavo Padovan <gustavo.padovan at collabora.co.uk>
> > ---
> >  drivers/gpu/drm/exynos/exynos_drm_crtc.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/exynos/exynos_drm_crtc.c b/drivers/gpu/drm/exynos/exynos_drm_crtc.c
> > index b3ba27f..1d3ca0a 100644
> > --- a/drivers/gpu/drm/exynos/exynos_drm_crtc.c
> > +++ b/drivers/gpu/drm/exynos/exynos_drm_crtc.c
> > @@ -55,6 +55,9 @@ static int exynos_crtc_atomic_check(struct drm_crtc *crtc,
> >  {
> >  	struct exynos_drm_crtc *exynos_crtc = to_exynos_crtc(crtc);
> >  
> > +	if (!state->active)
> > +		return 0;
> > +
> >  	if (exynos_crtc->ops->atomic_check)
> >  		return exynos_crtc->ops->atomic_check(exynos_crtc, state);
> >  
> 
> This looks like something that the core should be doing.

Nah, this is a bug in exynos atomic_check code. Drivers _must_ check state
irrespective of state->active - if they forgoe any checking when active =
false then legacy DPMS On might spuriuosly fail, which will upset
userspace. There shouldn't be any exceptions to this rule.

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