RE: [EXT] Re: [PATCH v1 3/5] drm: bridge: dw_hdmi: Enable GCP only for Deep Color

[Sandor Yu]

Hi,

> -----Original Message-----
> From: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
> Sent: 2022年4月6日 17:20
> To: Sandor Yu <sandor.yu@xxxxxxx>; dri-devel@xxxxxxxxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; andrzej.hajda@xxxxxxxxx;
> robert.foss@xxxxxxxxxx; Laurent.pinchart@xxxxxxxxxxxxxxxx;
> jonas@xxxxxxxxx; jernej.skrabec@xxxxxxxxx
> Cc: S.J. Wang <shengjiu.wang@xxxxxxx>; cai.huoqing@xxxxxxxxx;
> maxime@xxxxxxxxxx; harry.wentland@xxxxxxx; hverkuil-cisco@xxxxxxxxx;
> amuel@xxxxxxxxxxxx
> Subject: [EXT] Re: [PATCH v1 3/5] drm: bridge: dw_hdmi: Enable GCP only for
> Deep Color
> 
> Caution: EXT Email
> 
> On 06/04/2022 10:48, Sandor.yu@xxxxxxx wrote:
> > From: Sandor Yu <Sandor.yu@xxxxxxx>
> >
> > HDMI1.4b specification section 6.5.3:
> > Source shall only send GCPs with non-zero CD to sinks that indicate
> > support for Deep Color.
> >
> > DW HDMI GPC default enabled, clear gpc_auto bit for bpp 24.
> >
> > Signed-off-by: Sandor Yu <Sandor.yu@xxxxxxx>
> > ---
> >   drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 8 ++++++++
> >   1 file changed, 8 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > index b11577de4836..c7b11582529e 100644
> > --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > @@ -1160,6 +1160,14 @@ static void hdmi_video_packetize(struct
> dw_hdmi *hdmi)
> >               HDMI_VP_PR_CD_DESIRED_PR_FACTOR_MASK);
> >       hdmi_writeb(hdmi, val, HDMI_VP_PR_CD);
> >
> > +     val = hdmi_readb(hdmi, HDMI_FC_DATAUTO3);
> > +     if (color_depth == 4)
> > +             /* disable Auto GCP when bpp 24 */
> > +             val &= ~0x4;
> > +     else
> > +             val |= 0x4;
> > +     hdmi_writeb(hdmi, val, HDMI_FC_DATAUTO3);
> > +
> >       hdmi_modb(hdmi,
> HDMI_VP_STUFF_PR_STUFFING_STUFFING_MODE,
> >                 HDMI_VP_STUFF_PR_STUFFING_MASK,
> HDMI_VP_STUFF);
> >
> 
> Do you handle the case when color_depth == 0 when output is YUV422 ?
For YUV422 color depth 8, the gcp_auto bit need clear too, I will add it.
> 
> Neil
Thanks,
Sandor