Re: [PATCH v4 3/4] drm/mediatek: Add gamma correction.

[Daniel Vetter]

On Thu, Aug 11, 2016 at 11:02:27AM +0300, Ville Syrjälä wrote:
> On Thu, Aug 11, 2016 at 09:51:16AM +0200, Philipp Zabel wrote:
> > Am Donnerstag, den 11.08.2016, 10:44 +0300 schrieb Ville Syrjälä:
> > > On Thu, Aug 11, 2016 at 09:32:59AM +0200, Philipp Zabel wrote:
> > > > Am Donnerstag, den 28.07.2016, 10:22 +0800 schrieb Bibby Hsieh:
> > > > > Add gamma set function to correct brightness values.
> > > > > It applies arbitrary mapping curve to compensate the
> > > > > incorrect transfer function of the panel.
> > > > > 
> > > > > Signed-off-by: Bibby Hsieh <bibby.hsieh@xxxxxxxxxxxx>
> > > > > ---
> > > > >  drivers/gpu/drm/mediatek/mtk_drm_crtc.c     |    8 ++++++-
> > > > >  drivers/gpu/drm/mediatek/mtk_drm_crtc.h     |    1 +
> > > > >  drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c |   31 +++++++++++++++++++++++++++
> > > > >  drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h |   10 +++++++++
> > > > >  4 files changed, 49 insertions(+), 1 deletion(-)
> > > > > 
> > > > > diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> > > > > index 24aa3ba..cbb460a5 100644
> > > > > --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> > > > > +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> > > > > @@ -409,6 +409,9 @@ static void mtk_drm_crtc_atomic_flush(struct drm_crtc *crtc,
> > > > >  	}
> > > > >  	if (pending_planes)
> > > > >  		mtk_crtc->pending_planes = true;
> > > > > +	if (crtc->state->color_mgmt_changed)
> > > > > +		for (i = 0; i < mtk_crtc->ddp_comp_nr; i++)
> > > > > +			mtk_ddp_gamma_set(mtk_crtc->ddp_comp[i], crtc->state);
> > > > >  }
> > > > >  
> > > > >  static const struct drm_crtc_funcs mtk_crtc_funcs = {
> > > > > @@ -418,6 +421,7 @@ static const struct drm_crtc_funcs mtk_crtc_funcs = {
> > > > >  	.reset			= mtk_drm_crtc_reset,
> > > > >  	.atomic_duplicate_state	= mtk_drm_crtc_duplicate_state,
> > > > >  	.atomic_destroy_state	= mtk_drm_crtc_destroy_state,
> > > > > +	.gamma_set		= drm_atomic_helper_legacy_gamma_set,
> > > > >  };
> > > > >  
> > > > >  static const struct drm_crtc_helper_funcs mtk_crtc_helper_funcs = {
> > > > > @@ -568,7 +572,9 @@ int mtk_drm_crtc_create(struct drm_device *drm_dev,
> > > > >  				&mtk_crtc->planes[1].base, pipe);
> > > > >  	if (ret < 0)
> > > > >  		goto unprepare;
> > > > > -
> > > > > +	drm_mode_crtc_set_gamma_size(&mtk_crtc->base, MTK_LUT_SIZE);
> > > > > +	drm_helper_crtc_enable_color_mgmt(&mtk_crtc->base, MTK_LUT_SIZE,
> > > > > +					  MTK_LUT_SIZE);
> > > > 
> > > > I have applied all four patches and rebased onto v4.8-rc1, replacing
> > > > drm_helper_crtc_enable_color_mgmt with:
> > > > 
> > > > 	drm_crtc_enable_color_mgmt(&mtk_crtc->base, MTK_LUT_SIZE,
> > > > 				   true, MTK_LUT_SIZE);
> > > 
> > > BTW that looks wrong (already in the original). AFAICS the patch just
> > > handled the gamma_lut, not the degamma_lut, so telling you have both
> > > is not right.
> > 
> > Thanks, so should that be
> >        drm_crtc_enable_color_mgmt(&mtk_crtc->base, 0, false,
> >                                   MTK_LUT_SIZE);
> > instead, since we only handle gamma?
> 
> Hmm. Yeah, that looks correct since you didn't seem to have "ctm" either.

Yup, that's how this is meant to be used.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch