Re: [PATCH 1/6] drm: Add page_flip_target CRTC hook

[Daniel Vetter <daniel@ffwll.ch>]

On Thu, Aug 04, 2016 at 12:47:38PM +0200, Daniel Vetter wrote:
> On Thu, Aug 04, 2016 at 12:39:36PM +0900, Michel Dänzer wrote:
> > From: Michel Dänzer <michel.daenzer@amd.com>
> > 
> > Mostly the same as the existing page_flip hook, but takes an additional
> > parameter specifying the target vertical blank period when the flip
> > should take effect.
> > 
> > Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
> > ---
> >  drivers/gpu/drm/drm_crtc.c | 23 +++++++++++++++++++----
> >  include/drm/drm_crtc.h     | 14 ++++++++++++++
> >  2 files changed, 33 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> > index 9d3f80e..15ad7e2 100644
> > --- a/drivers/gpu/drm/drm_crtc.c
> > +++ b/drivers/gpu/drm/drm_crtc.c
> > @@ -5421,6 +5421,7 @@ int drm_mode_page_flip_ioctl(struct drm_device *dev,
> >  	struct drm_crtc *crtc;
> >  	struct drm_framebuffer *fb = NULL;
> >  	struct drm_pending_vblank_event *e = NULL;
> > +	u32 target_vblank = 0;
> >  	int ret = -EINVAL;
> >  
> >  	if (page_flip->flags & ~DRM_MODE_PAGE_FLIP_FLAGS ||
> > @@ -5434,6 +5435,18 @@ int drm_mode_page_flip_ioctl(struct drm_device *dev,
> >  	if (!crtc)
> >  		return -ENOENT;
> >  
> > +	if (crtc->funcs->page_flip_target) {
> > +		int r;
> > +
> > +		r = drm_crtc_vblank_get(crtc);
> 
> This leaks when e.g framebuffer_lookup fails.
> -Daniel
> 
> > +		if (r)
> > +			return r;
> > +
> > +		target_vblank = drm_crtc_vblank_count(crtc) +
> > +			!(page_flip->flags & DRM_MODE_PAGE_FLIP_ASYNC);
> > +	} else if (crtc->funcs->page_flip == NULL)
> > +		return -EINVAL;
> > +
> >  	drm_modeset_lock_crtc(crtc, crtc->primary);
> >  	if (crtc->primary->fb == NULL) {
> >  		/* The framebuffer is currently unbound, presumably
> > @@ -5444,9 +5457,6 @@ int drm_mode_page_flip_ioctl(struct drm_device *dev,
> >  		goto out;
> >  	}
> >  
> > -	if (crtc->funcs->page_flip == NULL)
> > -		goto out;
> > -
> >  	fb = drm_framebuffer_lookup(dev, page_flip->fb_id);
> >  	if (!fb) {
> >  		ret = -ENOENT;
> > @@ -5487,7 +5497,12 @@ int drm_mode_page_flip_ioctl(struct drm_device *dev,
> >  	}
> >  
> >  	crtc->primary->old_fb = crtc->primary->fb;
> > -	ret = crtc->funcs->page_flip(crtc, fb, e, page_flip->flags);
> > +	if (crtc->funcs->page_flip_target)
> > +		ret = crtc->funcs->page_flip_target(crtc, fb, e,
> > +						    page_flip->flags,
> > +						    target_vblank);
> > +	else
> > +		ret = crtc->funcs->page_flip(crtc, fb, e, page_flip->flags);
> >  	if (ret) {
> >  		if (page_flip->flags & DRM_MODE_PAGE_FLIP_EVENT)
> >  			drm_event_cancel_free(dev, &e->base);
> > diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> > index 9e6ab4a..ae1d9b6 100644
> > --- a/include/drm/drm_crtc.h
> > +++ b/include/drm/drm_crtc.h
> > @@ -579,6 +579,20 @@ struct drm_crtc_funcs {
> >  			 uint32_t flags);
> >  
> >  	/**
> > +	 * @page_flip_target:
> > +	 *
> > +	 * Same as @page_flip but with an additional parameter specifying the
> > +	 * target vertical blank period when the flip should take effect.

*absolute target vertical blank period as reported by
drm_crtc_vblank_count()

would imo be a good addition here.

> > +	 *
> > +	 * Note that the core code calls drm_crtc_vblank_get before this entry
> > +	 * point.
> 
> I think you should add "Drivers must drop that reference again by calling
> drm_crtc_vblank_put()."

Also, who should drop the reference in case ->page_flip_target fails?

> 
> It's a bit icky that we have this difference (both compared to old page
> flip, but also atomic doesn't grab a vblank reference either). But really
> can't be avoided, at least if we implement the relative mode.

With all issues addressed:

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
-Daniel

> -Daniel
> 
> > +	 */
> > +	int (*page_flip_target)(struct drm_crtc *crtc,
> > +				struct drm_framebuffer *fb,
> > +				struct drm_pending_vblank_event *event,
> > +				uint32_t flags, uint32_t target);
> > +
> > +	/**
> >  	 * @set_property:
> >  	 *
> >  	 * This is the legacy entry point to update a property attached to the
> > -- 
> > 2.8.1
> > 
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

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