From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= <ville.syrjala@linux.intel.com>
Subject: Re: [PATCH v2 3/6] drm/i915: Implement LRI based FBC
	tracking
Date: Wed, 6 Nov 2013 19:51:14 +0200
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To: Chris Wilson <chris@chris-wilson.co.uk>, intel-gfx@lists.freedesktop.org
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On Wed, Nov 06, 2013 at 05:36:01PM +0000, Chris Wilson wrote:
> On Wed, Nov 06, 2013 at 07:23:25PM +0200, ville.syrjala@linux.intel.com w=
rote:
> > +bool intel_fb_obj_has_fbc(struct drm_i915_gem_object *obj)
> > +{
> > +	struct drm_device *dev =3D obj->base.dev;
> > +	struct drm_i915_private *dev_priv =3D dev->dev_private;
> > +	struct drm_crtc *crtc;
> > +
> > +	/* check for potential scanout */
> > +	if (!obj->pin_display)
> > +		return false;
> =

> 	if (dev_oriv->fbc.plane =3D=3D -1)
> 		return false;
> =

> 	crtc =3D dev_priv->plane_to_crtc[dev_priv->fbc.plane];
> =

> 	mutex_lock(&crtc->mutex);
> 	has_fbc =3D crtc->fb && to_intel_framebuffer(crtc->fb)->obj =3D=3D obj;
> 	mutex_unlock(&crtc->mutex);
> =

> 	return has_fbc
>  }
> =

> Perhaps?

Oh yeah, much nicer. Except now the locking I came up here sucks. Need
to rethink that part somehow. Maybe I'll just slap an
ACCESS_ONCE(crtc->fb) there. Hmm, but I guess I'd also need to grab a
reference to the fb to avoid it disappearing while were looking at it.

This is starting to be a bit hairy. So maybe I should just stick our
current fbc scanout object to dev_priv->fbc.obj, and update it when
doing page flips/modeset. I really didn't want to start messing about
with fbc locking but looks like there's no way around it.

-- =

Ville Syrj=E4l=E4
Intel OTC