[Intel-gfx] [PATCH] drm/i915: Avoid reading fbc registers in vain when fbc was never enabled.

[Rodrigo Vivi]

On Fri, Sep 19, 2014 at 8:40 AM, Daniel Vetter <daniel at ffwll.ch> wrote:

> On Thu, Sep 18, 2014 at 11:42:44AM -0700, Rodrigo Vivi wrote:
> > On Thu, Sep 18, 2014 at 4:39 AM, Daniel Vetter <daniel at ffwll.ch> wrote:
> >
> > > On Thu, Sep 18, 2014 at 07:28:48AM +0100, Chris Wilson wrote:
> > > > On Wed, Sep 17, 2014 at 04:59:20PM -0400, Rodrigo Vivi wrote:
> > > > > If it wasn't never enabled by kernel parameter or platform default
> > > > > we can avoid reading registers so many times in vain
> > > >
> > > > Nak.
> > >
> > > Well I've merged this for now to reduce fbc impact.
> > >
> >
> > Uhm, unfortunatelly I'm afraid Chris was right.
> > Paulo also nacked it. Because it just helps when it was explicitly
> disabled
> > by setting i915.enable_fbc=0 while the default is -1.
> >
> > I though about returning on <= 0, but Paulo is afraid that when enabling
> > back for some platform people would forget to fix this part here and I
> > agree.
>
> Well I guess I should have read mails before pushing out a new -next ;-)
> So this is now baked in. Should I revert or can we just fix up on top?
>

No problem, I can fix this on top.

But what do you prefer:

1. <=0 return and changing parameter permission from 600 to 400
2. dev_priv->fbc_enabled
3. or check if fbc_no_reason was ever set? Although I don't like the
fbc_no_reason and would like to clean it up in the future. But anyway, any
option here is temporary until a proper rework for cleanup and real fix.


> -Daniel
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
>



-- 
Rodrigo Vivi
Blog: http://blog.vivi.eng.br
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