[PATCH 4/7] drm/omap: Implement CTM property for CRTC using OVL managers CPR matrix

[Laurent Pinchart]

Hi Jyri,

On Thu, Sep 05, 2019 at 01:00:51PM +0300, Jyri Sarha wrote:
> On 05/09/2019 00:52, Laurent Pinchart wrote:
> >>>>>>  static void omap_crtc_write_crtc_properties(struct drm_crtc *crtc)
> >>>>>>  {
> >>>>>>  	struct omap_drm_private *priv = crtc->dev->dev_private;
> >>>>>> @@ -402,7 +428,16 @@ static void omap_crtc_write_crtc_properties(struct drm_crtc *crtc)
> >>>>>>  	info.default_color = 0x000000;
> >>>>>>  	info.trans_enabled = false;
> >>>>>>  	info.partial_alpha_enabled = false;
> >>>>>> -	info.cpr_enable = false;
> >>>>>> +
> >>>>>> +	if (crtc->state->ctm) {
> >>>>>> +		struct drm_color_ctm *ctm =
> >>>>>> +			(struct drm_color_ctm *) crtc->state->ctm->data;
> >>>>>> +
> >>>>>> +		info.cpr_enable = true;
> >>>>>> +		omap_crtc_cpr_coefs_from_ctm(ctm, &info.cpr_coefs);
> >>>>>
> >>>>> As an optimisation it would be nice to only write the coefficients when
> >>>>> they actually change. That could be implemented on top of this series.
> >>>>
> >>>> E.g. apply this ?
> >>>>
> >>>> - if (crtc->state->ctm)
> >>>> + if (crtc->state->color_mgmt_changed && crtc->state->ctm)
> >>>
> >>> Something like that, but .mgr_setup() should then be taught not to write
> >>> unchanged CTM tables to registers. Do you think it would be worth it ?
> >>
> >> Hmmm, jess I should do it like this:
> >> if (crtc->state->color_mgmt_changed) {
> >> 	if (crtc->state->ctm) {
> >> ...
> >>>>>> +	} else {
> >>>>>> +		info.cpr_enable = false;
> >>>>>> +	}
> >> }
> >>
> >> This way the whole CPR functionality is turned off, if the there is no
> >> CTM in the crtc state.
> >
> > Yes, but you would also need to update .mgr_setup() :-) A new
> > color_mgmt_changed flag would be needed in the info structure too.
> 
> I am starting to thing that such an "optimization" may not be worth the
> added complexity. The arithmetic and writing three registers is not that
> costly and we do not commit a new crtc state that often.

We call omap_crtc_write_crtc_properties() in omap_crtc_atomic_flush(),
so that's at every page flip...

> If we later consider otherwise we can add the optimization as a separate
> patch.

-- 
Regards,

Laurent Pinchart