Re: [PATCH v16 4/4] drm/bridge: dw-hdmi: fix bus formats negotiation for 8 bit modes

[Neil Armstrong]

Hi,

On 02/03/2022 12:15, H. Nikolaus Schaller wrote:
> Hi Neil,
>
> > Am 02.03.2022 um 11:25 schrieb Neil Armstrong <narmstrong@xxxxxxxxxxxx>:
> >
> > > I added a printk for hdmi->sink_is_hdmi. This returns 1. Which IMHO is to be expected
> > > since I am using a HDMI connector and panel... So your patch will still add the UYVY formats.
> > > Either the synposys module inside the jz4780 or the panel does not understand them.
> >
> > By selecting the UYVY formats, the driver will enable the colorspace converters in the dw-hdmi IP,
> > I don't see why it doesn't work here...
> >
> > There is a bit called `Support Color Space Converter` in config0_id:
> > bit	|	Name	|	R/W	|	Desc
> > 2 	|	csc	| 	R 	|	Indicates if Color Space Conversion block is present
> >
> > Could you dump all the config0 bits:
> >
> > =======================><=============================
> > diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > index 54d8fdad395f..547731482da8 100644
> > --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > @@ -3431,6 +3431,7 @@ struct dw_hdmi *dw_hdmi_probe(struct platform_device *pdev,
> >         pdevinfo.id = PLATFORM_DEVID_AUTO;
> >
> >         config0 = hdmi_readb(hdmi, HDMI_CONFIG0_ID);
> > +       dev_info(dev, "config0: %x\n", config0);
> >         config3 = hdmi_readb(hdmi, HDMI_CONFIG3_ID);
> >
> >         if (iores && config3 & HDMI_CONFIG3_AHBAUDDMA) {
> > =======================><=============================
> >
> > If this bit is missing, this would explain the black screen.
>
> [    9.291011] dw-hdmi-ingenic 10180000.hdmi: config0: bf
>
> Hm. Or is the color-space conversion of the sw-hdmi module inside the jz4780 broken
> or not configured properly?
>
> (cross-checked: RGB mode still works if I force hdmi->sink_is_hdmi = false)

I don't understand what's wrong, can you try to make the logic select MEDIA_BUS_FMT_YUV8_1X24 instead of DRM_COLOR_FORMAT_YCBCR422 ?

If your CSC is broken, we'll need to disable it on your platform.

Thanks,
Neil

> BR and thanks,
> Nikolaus