linux-kernel - Re: [PATCH v3 02/12] dt-bindings: display: mediatek: add MT8195 hdmi bindings

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Date:   Mon, 2 Jan 2023 13:38:33 +0000
From:   Guillaume Ranquet <granquet@...libre.com>
To:     CK Hu <ck.hu@...iatek.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "kishon@...com" <kishon@...com>,
        Chunfeng Yun <Chunfeng.Yun@...iatek.com>,
        "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>,
        Jitao Shi <jitao.shi@...iatek.com>,
        "daniel@...ll.ch" <daniel@...ll.ch>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        "airlied@...il.com" <airlied@...il.com>,
        "rzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "koul@...nel.org" <vkoul@...nel.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "inux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        Mac Shen <Mac.Shen@...iatek.com>,
        "evicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "rzysztof.kozlowski@...aro.org" <krzysztof.kozlowski@...aro.org>,
        Stuart Lee <Stuart.Lee@...iatek.com>,
        "ri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "inux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-phy@...ts.infradead.org" <linux-phy@...ts.infradead.org>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH v3 02/12] dt-bindings: display: mediatek: add MT8195 hdmi bindings

On Mon, 26 Dec 2022 06:18, CK Hu (胡俊光) <ck.hu@...iatek.com> wrote:
>Hi, Guillaume:
>
>On Fri, 2022-11-04 at 15:09 +0100, Guillaume Ranquet wrote:
>> Add mt8195 SoC bindings for hdmi and hdmi-ddc
>>
>> On mt8195 the ddc i2c controller is part of the hdmi IP block and
>> thus has no
>> specific register range, power domain or interrupt, making it simpler
>> than its the legacy "mediatek,hdmi-ddc" binding.
>>
>> Signed-off-by: Guillaume Ranquet <granquet@...libre.com>
>> ---
>>
>
>[snip]
>
>> a/Documentation/devicetree/bindings/display/mediatek/mediatek,mt8195-
>> hdmi-ddc.yaml
>> b/Documentation/devicetree/bindings/display/mediatek/mediatek,mt8195-
>> hdmi-ddc.yaml
>> new file mode 100644
>> index 000000000000..2dc273689584
>> --- /dev/null
>> +++
>> b/Documentation/devicetree/bindings/display/mediatek/mediatek,mt8195-
>> hdmi-ddc.yaml
>> @@ -0,0 +1,51 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id:
>> https://urldefense.com/v3/__http://devicetree.org/schemas/display/mediatek/mediatek,mt8195-hdmi-ddc.yaml*__;Iw!!CTRNKA9wMg0ARbw!wwVQuq5lzW0lvUFUkVXPWT8cIu96xdkn4tMams1E55qyxEZmgV1i0WfpOlq57w$
>>
>> +$schema:
>> https://urldefense.com/v3/__http://devicetree.org/meta-schemas/core.yaml*__;Iw!!CTRNKA9wMg0ARbw!wwVQuq5lzW0lvUFUkVXPWT8cIu96xdkn4tMams1E55qyxEZmgV1i0WdSGOSxzw$
>>
>> +
>> +title: Mediatek HDMI DDC for mt8195
>> +
>> +maintainers:
>> +  - CK Hu <ck.hu@...iatek.com>
>> +  - Jitao shi <jitao.shi@...iatek.com>
>> +
>> +description: |
>> +  The HDMI DDC i2c controller is used to interface with the HDMI DDC
>> pins.
>> +
>> +properties:
>> +  compatible:
>> +    enum:
>> +      - mediatek,mt8195-hdmi-ddc
>> +
>> +  clocks:
>> +    maxItems: 1
>> +
>> +  clock-names:
>> +    items:
>> +      - const: ddc
>> +
>> +  mediatek,hdmi:
>> +    $ref: /schemas/types.yaml#/definitions/phandle
>> +    description:
>> +      A phandle to the mt8195 hdmi controller
>> +
>> +required:
>> +  - compatible
>> +  - clocks
>> +  - clock-names
>> +
>> +additionalProperties: false
>> +
>> +examples:
>> +  - |
>> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
>> +    #include <dt-bindings/interrupt-controller/irq.h>
>> +    hdmiddc0: i2c {
>> +      compatible = "mediatek,mt8195-hdmi-ddc";
>> +      mediatek,hdmi = <&hdmi0>;
>> +      clocks = <&clk26m>;
>> +      clock-names = "ddc";
>> +    };
>
>I think we should not have a virtual device. This ddc is part of
>mt8195-hdmi device, so just keep mt8195-hdmi, and let mt8195-hdmi
>driver to probe the sub driver of ddc driver.
>
>Regards,
>CK

Hi CK,

Thx for your input.
Though I would strongly prefer to keep the ddc as a separate "virtual device".

It aligns better with the goal of reusing as much code as possible
from the HDMI V1 IP,
which is something you have been advocating since V1 of this patch
quite some time ago
and has shaped this patch.

To me we are in a state that is clean and avoids branching in the hdmi
common code.
Would you reconsider and allow the use of that virtual device?

Thx,
Guillaume.

>
>> +
>> +...
>>