[Intel-gfx] [PATCH] drm/damage_helper: Fix handling of cursor dirty buffers

[Souza, Jose]

On Wed, 2021-08-18 at 11:54 +0200, Daniel Vetter wrote:
> On Tue, Aug 17, 2021 at 04:26:04PM -0700, José Roberto de Souza wrote:
> > Cursors don't have a framebuffer so the fb comparisson was always
> > failing and atomic state was being committed without any plane state.
> > 
> > So here checking if objects match when checking cursors.
> 
> This looks extremely backwards ... what exactly is this fixing? If this
> isn't based on a real world compositor usage but some igt, then I'd say
> the igt here is very wrong.

Yes it is IGT.
Writing to cursor buffer current in the screen and calling drmModeDirtyFB() causes a empty atomic commit by drm_atomic_helper_dirtyfb().


> -Daniel
> 
> > Fixes: b9fc5e01d1ce ("drm: Add helper to implement legacy dirtyfb")
> > Cc: Daniel Vetter <daniel.vetter at intel.com>
> > Cc: Rob Clark <robdclark at gmail.com>
> > Cc: Deepak Rawat <drawat at vmware.com>
> > Cc: Gwan-gyeong Mun <gwan-gyeong.mun at intel.com>
> > Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
> > ---
> >  drivers/gpu/drm/drm_damage_helper.c | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_damage_helper.c b/drivers/gpu/drm/drm_damage_helper.c
> > index 8eeff0c7bdd47..595187d97c131 100644
> > --- a/drivers/gpu/drm/drm_damage_helper.c
> > +++ b/drivers/gpu/drm/drm_damage_helper.c
> > @@ -157,12 +157,18 @@ int drm_atomic_helper_dirtyfb(struct drm_framebuffer *fb,
> >  retry:
> >  	drm_for_each_plane(plane, fb->dev) {
> >  		struct drm_plane_state *plane_state;
> > +		bool match;
> >  
> >  		ret = drm_modeset_lock(&plane->mutex, state->acquire_ctx);
> >  		if (ret)
> >  			goto out;
> >  
> > -		if (plane->state->fb != fb) {
> > +		match = plane->state->fb == fb;
> > +		/* Check if objs match to handle dirty buffers of cursors */
> > +		if (plane->type == DRM_PLANE_TYPE_CURSOR && plane->state->fb)
> > +			match |= fb->obj[0] == plane->state->fb->obj[0];
> > +
> > +		if (!match) {
> >  			drm_modeset_unlock(&plane->mutex);
> >  			continue;
> >  		}
> > -- 
> > 2.32.0
> > 
>