Subject: Re: dw_hdmi is showing wrong colour after commit
 7cd70656d1285b79("drm/bridge: display-connector: implement bus fmts
 callbacks")
To:     Fabio Estevam <festevam@gmail.com>,
        Biju Das <biju.das.jz@bp.renesas.com>
Cc:     "daniel@ffwll.ch" <daniel@ffwll.ch>,
        "Laurent.pinchart@ideasonboard.com" 
        <Laurent.pinchart@ideasonboard.com>,
        "robert.foss@linaro.org" <robert.foss@linaro.org>,
        "jonas@kwiboo.se" <jonas@kwiboo.se>,
        "jernej.skrabec@gmail.com" <jernej.skrabec@gmail.com>,
        "martin.blumenstingl@googlemail.com" 
        <martin.blumenstingl@googlemail.com>,
        "linux-amlogic@lists.infradead.org" 
        <linux-amlogic@lists.infradead.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
References: <OS0PR01MB59221ED76B74231F5836D5FB86539@OS0PR01MB5922.jpnprd01.prod.outlook.com>
 <CAOMZO5DJiCb5bJN5_nxnYa-FsK-u7QtFghWNzs_-udE42XPDeA@mail.gmail.com>
From:   Neil Armstrong <narmstrong@baylibre.com>
Organization: Baylibre
Message-ID: <502f3ec4-fea4-8e14-c7a9-39418fc05d6d@baylibre.com>
Date:   Fri, 14 Jan 2022 09:23:51 +0100
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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.

> 
> 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