RE: dw_hdmi is showing wrong colour after commit 7cd70656d1285b79("drm/bridge: display-connector: implement bus fmts callbacks")

[Biju Das <biju.das.jz@bp.renesas.com>]

Hi Neil,
 
+ renesas-soc

> Subject: Re: dw_hdmi is showing wrong colour after commit
> 7cd70656d1285b79("drm/bridge: display-connector: implement bus fmts
> callbacks")
> 
> Hi,
> 
> On 13/01/2022 21:01, Fabio Estevam wrote:
> > Hi Biju,
> >
> > On Thu, Jan 13, 2022 at 2:45 PM Biju Das <biju.das.jz@bp.renesas.com>
> wrote:
> >>
> >> Hi All,
> >>
> >> RZ/G2{H, M, N} SoC has dw_hdmi IP and it was working ok(colour) till
> >> the commit
> >> 7cd70656d1285b79("drm/bridge: display-connector: implement bus fmts
> callbacks").
> >>
> >> After this patch, the screen becomes greenish(may be it is setting it
> into YUV format??).
> >>
> >> By checking the code, previously it used to call get_input_fmt callback
> and set colour as RGB24.
> >>
> >> After this commit, it calls get_output_fmt_callbck and returns 3
> >> outputformats(YUV16, YUV24 and RGB24) And get_input_fmt callback, I see
> the outputformat as YUV16 instead of RGB24.
> >>
> >> Not sure, I am the only one seeing this issue with dw_HDMI driver.
> 
> This patch was introduced to maintain the bridge color format negotiation
> after using DRM_BRIDGE_ATTACH_NO_CONNECTOR, but it seems it behaves
> incorrectly if the first bridge doesn't implement the negotiation
> callbacks.
> 
> Let me check the code to see how to fix that.

Thanks for the information, I am happy to test the patch/fix.

Cheers,
Biju

> 
> >
> > I have tested linux-next 20220112 on a imx6q-sabresd board, which shows:
> >
> > dwhdmi-imx 120000.hdmi: Detected HDMI TX controller v1.30a with HDCP
> > (DWC HDMI 3D TX PHY)
> >
> > The colors are shown correctly here.
> >
> 
> The imx doesn't use DRM_BRIDGE_ATTACH_NO_CONNECTOR so the negotiation
> fails and use the RGB fallback input & output format.
> 
> Anyway thanks for testing
> 
> Neil
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