Re: [RFC 5/8] drm/fence: add fence to drm_pending_event

[Gustavo Padovan <gustavo@padovan.org>]

2016-04-15 Daniel Vetter <daniel@ffwll.ch>:

> On Thu, Apr 14, 2016 at 06:29:38PM -0700, Gustavo Padovan wrote:
> > From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
> > 
> > Now a drm_pending_event can either send a real drm_event or signal a
> > fence, or both. It allow us to signal via fences when the buffer is
> > displayed on the screen. Which in turn means that the previous buffer
> > is not in use anymore and can be freed or sent back to another driver
> > for processing.
> > 
> > Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
> 
> Do you have atomic igt testcase that exercise all the combinations of
> drm_event and in/out-fences and make sure it all keeps working? Tomeu
> already converted that over to be a generic testcase.

Not yet. I'll check for test cases.

> 
> > ---
> >  drivers/gpu/drm/drm_atomic.c | 19 +++++++++++++------
> >  drivers/gpu/drm/drm_fops.c   |  5 +++--
> >  drivers/gpu/drm/drm_irq.c    |  7 +++++++
> >  include/drm/drmP.h           |  1 +
> >  4 files changed, 24 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> > index 6702502..0b95526 100644
> > --- a/drivers/gpu/drm/drm_atomic.c
> > +++ b/drivers/gpu/drm/drm_atomic.c
> > @@ -1431,7 +1431,8 @@ EXPORT_SYMBOL(drm_atomic_async_commit);
> >   */
> >  
> >  static struct drm_pending_vblank_event *create_vblank_event(
> > -		struct drm_device *dev, struct drm_file *file_priv, uint64_t user_data)
> > +		struct drm_device *dev, struct drm_file *file_priv,
> > +		struct fence *fence, uint64_t user_data)
> >  {
> >  	struct drm_pending_vblank_event *e = NULL;
> >  	int ret;
> > @@ -1444,12 +1445,17 @@ static struct drm_pending_vblank_event *create_vblank_event(
> >  	e->event.base.length = sizeof(e->event);
> >  	e->event.user_data = user_data;
> >  
> > -	ret = drm_event_reserve_init(dev, file_priv, &e->base, &e->event.base);
> > -	if (ret) {
> > -		kfree(e);
> > -		return NULL;
> > +	if (file_priv) {
> > +		ret = drm_event_reserve_init(dev, file_priv, &e->base,
> > +					     &e->event.base);
> > +		if (ret) {
> > +			kfree(e);
> > +			return NULL;
> > +		}
> >  	}
> >  
> > +	e->base.fence = fence;
> > +
> >  	return e;
> >  }
> >  
> > @@ -1676,7 +1682,8 @@ retry:
> >  		for_each_crtc_in_state(state, crtc, crtc_state, i) {
> >  			struct drm_pending_vblank_event *e;
> >  
> > -			e = create_vblank_event(dev, file_priv, arg->user_data);
> > +			e = create_vblank_event(dev, file_priv, NULL,
> > +						arg->user_data);
> >  			if (!e) {
> >  				ret = -ENOMEM;
> >  				goto out;
> > diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c
> > index aeef58e..38def49 100644
> > --- a/drivers/gpu/drm/drm_fops.c
> > +++ b/drivers/gpu/drm/drm_fops.c
> > @@ -801,8 +801,9 @@ void drm_send_event_locked(struct drm_device *dev, struct drm_pending_event *e)
> >  {
> >  	assert_spin_locked(&dev->event_lock);
> >  
> > -	if (!e->file_priv) {
> > -		e->destroy(e);
> > +	if (!e->file_priv || !e->event) {
> 
> This would be a bug: e->file_priv != NULL iff e->event != NULL. How did
> this happen?

Not sure now. But I needed this to prevent a crash, I don't have logs of
it anymore, I'll check this again.

> 
> > +		if (e->destroy)
> > +			e->destroy(e);
> >  		return;
> >  	}
> >  
> > diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
> > index 3c1a6f1..0c5d7cb 100644
> > --- a/drivers/gpu/drm/drm_irq.c
> > +++ b/drivers/gpu/drm/drm_irq.c
> > @@ -41,6 +41,7 @@
> >  
> >  #include <linux/vgaarb.h>
> >  #include <linux/export.h>
> > +#include <linux/fence.h>
> >  
> >  /* Access macro for slots in vblank timestamp ringbuffer. */
> >  #define vblanktimestamp(dev, pipe, count) \
> > @@ -1124,6 +1125,12 @@ void drm_send_vblank_event(struct drm_device *dev, unsigned int pipe,
> >  		now = get_drm_timestamp();
> >  	}
> >  	e->pipe = pipe;
> > +
> > +	if (e->base.fence) {
> > +		fence_signal(e->base.fence);
> > +		fence_put(e->base.fence);
> > +	}
> 
> I'd put this into drm_send_event_locked even. In case we send out fences
> for other events too (e.g. exynos uses drm_event for rendering ...).

Okay. Looking into that.

	Gustavo