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Subject: Re: dw_hdmi is showing wrong colour after commit
 7cd70656d1285b79("drm/bridge: display-connector: implement bus fmts
 callbacks")
To:     Kieran Bingham <kieran.bingham@ideasonboard.com>,
        Biju Das <biju.das.jz@bp.renesas.com>,
        Fabio Estevam <festevam@gmail.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>,
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        <linux-amlogic@lists.infradead.org>,
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        <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>,
        "linux-renesas-soc@vger.kernel.org" 
        <linux-renesas-soc@vger.kernel.org>
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 <164241711700.10801.9011781958267060147@Monstersaurus>
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 <164242831905.10801.10615379536917395435@Monstersaurus>
From:   Neil Armstrong <narmstrong@baylibre.com>
Organization: Baylibre
Message-ID: <92f37b42-23db-4aab-5262-911d07b6301f@baylibre.com>
Date:   Mon, 17 Jan 2022 15:07:45 +0100
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On 17/01/2022 15:05, Kieran Bingham wrote:
> Quoting Neil Armstrong (2022-01-17 13:53:47)
>> On 17/01/2022 11:58, Kieran Bingham wrote:
>>> Hi Neil,
> 
> <big snips to clear up contexts>
> 
>>> This fixes the issue for me here on an H3 Salvator-XS.
>>>
>>> Could you add...
>>>
>>> Bisected-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
>>> Tested-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
>>>
>>> alongside Biju's Reported-by: tag when posting as a fix please?
>>
>>
>> Which patch did you test ?
> 
> Ah, yes that's not clear is it - sorry! I replied in the wrong place on
> the thread when I went back to the mail ... see below...
> 
>>>> I'm not happy with this version since it's merely a hack which makes it work.
>>>>
>>>> Can you test the following change instead, it's correctly handles your situation in a generic manner.
>>>>
>>>> ========================><=============================
>>>> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
>>>> index 54d8fdad395f..9f2e1cac0ae2 100644
>>>> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
>>>> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
>>>> @@ -2551,8 +2551,9 @@ static u32 *dw_hdmi_bridge_atomic_get_output_bus_fmts(struct drm_bridge *bridge,
>>>>         if (!output_fmts)
>>>>                 return NULL;
>>>>
>>>> -       /* If dw-hdmi is the only bridge, avoid negociating with ourselves */
>>>> -       if (list_is_singular(&bridge->encoder->bridge_chain)) {
>>>> +       /* If dw-hdmi is the first or only bridge, avoid negociating with ourselves */
>>>> +       if (list_is_singular(&bridge->encoder->bridge_chain) ||
>>>> +           list_is_first(&bridge->chain_node, &bridge->encoder->bridge_chain)) {
>>>>                 *num_output_fmts = 1;
>>>>                 output_fmts[0] = MEDIA_BUS_FMT_FIXED;
>>>>
>>>> @@ -2673,6 +2674,10 @@ static u32 *dw_hdmi_bridge_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
>>>>         if (!input_fmts)
>>>>                 return NULL;
>>>>
>>>> +       /* If dw-hdmi is the first bridge fall-back to safe output format */
>>>> +       if (list_is_first(&bridge->chain_node, &bridge->encoder->bridge_chain))
>>>> +               output_fmt = MEDIA_BUS_FMT_FIXED;
>>>> +
>>>>         switch (output_fmt) {
>>>>         /* If MEDIA_BUS_FMT_FIXED is tested, return default bus format */
>>>>         case MEDIA_BUS_FMT_FIXED:
>>>> ========================><=============================
> 
> Sorry, I replied in the wrong part of the thread.
> 
> Here's the direct diff on my local tree:
> 
> 
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index 54d8fdad395f..cac9a87949f1 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -2551,8 +2551,10 @@ static u32 *dw_hdmi_bridge_atomic_get_output_bus_fmts(struct drm_bridge *bridge,
>         if (!output_fmts)
>                 return NULL;
>  
> -       /* If dw-hdmi is the only bridge, avoid negociating with ourselves */
> -       if (list_is_singular(&bridge->encoder->bridge_chain)) {
> +       /* If dw-hdmi is the first or only bridge, avoid negociating with ourselves */
> +       if (list_is_singular(&bridge->encoder->bridge_chain) ||
> +           list_is_first(&bridge->chain_node, &bridge->encoder->bridge_chain)) {
> +
>                 *num_output_fmts = 1;
>                 output_fmts[0] = MEDIA_BUS_FMT_FIXED;
>  
> @@ -2673,6 +2675,10 @@ static u32 *dw_hdmi_bridge_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
>         if (!input_fmts)
>                 return NULL;
>  
> +       /* If dw-hdmi is the first bridge fall-back to safe output format */
> +       if (list_is_first(&bridge->chain_node, &bridge->encoder->bridge_chain))
> +               output_fmt = MEDIA_BUS_FMT_FIXED;
> +
>         switch (output_fmt) {
>         /* If MEDIA_BUS_FMT_FIXED is tested, return default bus format */
>         case MEDIA_BUS_FMT_FIXED:
> 
> Which I believe matches the above.

Ok thanks of clarifying !

let me post it asap.

Neil

> 
> --
> Kieran
>