linux-kernel - Re: [PATCH v2, 1/2] drm/mediatek: Fix gamma correction issue

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Date:   Fri, 13 Dec 2019 16:03:11 +0800
From:   Yongqiang Niu <yongqiang.niu@...iatek.com>
To:     CK Hu <ck.hu@...iatek.com>
CC:     Philipp Zabel <p.zabel@...gutronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "David Airlie" <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Mark Rutland <mark.rutland@....com>,
        <dri-devel@...ts.freedesktop.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH v2, 1/2] drm/mediatek: Fix gamma correction issue

On Fri, 2019-12-13 at 15:48 +0800, CK Hu wrote:
> Hi, Yongqiang:
> 
> The title is too rough. Any bug of gamma would be this title. I would
> like the title show explicitly what it does.
> 
> On Fri, 2019-12-13 at 15:28 +0800, Yongqiang Niu wrote:
> > if there is no gamma function in the crtc
> > display path, don't add gamma property
> > for crtc
> > 
> > Signed-off-by: Yongqiang Niu <yongqiang.niu@...iatek.com>
> > ---
> >  drivers/gpu/drm/mediatek/mtk_drm_crtc.c | 10 ++++++++--
> >  1 file changed, 8 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> > index ca4fc47..9a8e1d4 100644
> > --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> > +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> > @@ -734,6 +734,7 @@ int mtk_drm_crtc_create(struct drm_device *drm_dev,
> >  	int pipe = priv->num_pipes;
> >  	int ret;
> >  	int i;
> > +	uint gamma_lut_size = 0;
> >  
> >  	if (!path)
> >  		return 0;
> > @@ -785,6 +786,9 @@ int mtk_drm_crtc_create(struct drm_device *drm_dev,
> >  		}
> >  
> >  		mtk_crtc->ddp_comp[i] = comp;
> > +
> > +		if (comp->funcs->gamma_set)
> > +			gamma_lut_size = MTK_LUT_SIZE;
> >  	}
> >  
> >  	for (i = 0; i < mtk_crtc->ddp_comp_nr; i++)
> > @@ -805,8 +809,10 @@ int mtk_drm_crtc_create(struct drm_device *drm_dev,
> >  				NULL, pipe);
> >  	if (ret < 0)
> >  		return ret;
> > -	drm_mode_crtc_set_gamma_size(&mtk_crtc->base, MTK_LUT_SIZE);
> > -	drm_crtc_enable_color_mgmt(&mtk_crtc->base, 0, false, MTK_LUT_SIZE);
> > +
> > +	if (gamma_lut_size)
> > +		drm_mode_crtc_set_gamma_size(&mtk_crtc->base, gamma_lut_size);
> > +	drm_crtc_enable_color_mgmt(&mtk_crtc->base, 0, false, gamma_lut_size);
> 
> If there is no gamma, shall we enable color management?
> 
> Regards,
> CK

drm_crtc_enable_color_mgmt will check the gamma_lut_size parameter,
if no gamma, gamma_lut_size will be 0, and gamma_lut_size will not attch
gamma property for the crtc
> 
> >  	priv->num_pipes++;
> >  	mutex_init(&mtk_crtc->hw_lock);
> >  
> 
>