[PATCH 4/5] drm: Allow reenabling of vblank interrupts even if refcount>0

[Ville Syrjälä]

On Tue, Mar 04, 2014 at 10:16:02AM +0100, Daniel Vetter wrote:
> On Fri, Feb 21, 2014 at 09:03:34PM +0200, ville.syrjala at linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > 
> > If someone holds a vblank reference across the modeset, and after/during
> > the modeset someone tries to grab a vblank reference, the current code
> > won't re-enable the vblank interrupts. That's not good, so instead allow
> > the driver to choose whether drm_vblank_get() should always enable the
> > interrupts regardless of the refcount.
> > 
> > Combined with the drm_vblank_off/drm_vblank_on reject mechanism, this
> > can also be used to allow drivers to use vblank interrupts during
> > modeset, whether or not someone is currently holding a vblank reference.
> > 
> > Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > ---
> >  drivers/gpu/drm/drm_irq.c | 3 ++-
> >  include/drm/drmP.h        | 6 ++++++
> >  2 files changed, 8 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
> > index 6e5d820..d613b6f 100644
> > --- a/drivers/gpu/drm/drm_irq.c
> > +++ b/drivers/gpu/drm/drm_irq.c
> > @@ -897,7 +897,8 @@ int drm_vblank_get(struct drm_device *dev, int crtc)
> >  	}
> >  
> >  	/* Going from 0->1 means we have to enable interrupts again */
> > -	if (atomic_add_return(1, &dev->vblank[crtc].refcount) == 1) {
> > +	if (atomic_add_return(1, &dev->vblank[crtc].refcount) == 1 ||
> > +	    dev->vblank_always_enable_on_get) {
> >  		spin_lock(&dev->vblank_time_lock);
> >  		if (!dev->vblank[crtc].enabled) {
> >  			/* Enable vblank irqs under vblank_time_lock protection.
> > diff --git a/include/drm/drmP.h b/include/drm/drmP.h
> > index ee40483..3eca0ee 100644
> > --- a/include/drm/drmP.h
> > +++ b/include/drm/drmP.h
> > @@ -1156,6 +1156,12 @@ struct drm_device {
> >  	 */
> >  	bool vblank_disable_allowed;
> >  
> > +	/*
> > +	 * Should a non-rejected drm_vblank_get() always enable the
> > +	 * vblank interrupt regardless of the current refcount?
> > +	 */
> > +	bool vblank_always_enable_on_get;
> 
> Nack for this hack. Why can't drm_vblank_on not just re-enable the vblank
> interrupt if we still have a vblank reference?

Hmm. Yeah that seems like a nicer way to go about it.

-- 
Ville Syrjälä
Intel OTC