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Message-ID: <761791af-971d-8e64-857c-4b3cbf9487da@collabora.com>
Date: Tue, 3 Jan 2023 11:11:38 +0100
From: AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com>
To: Guillaume Ranquet <granquet@...libre.com>,
"oul@...nel.org" <vkoul@...nel.org>, CK Hu <ck.hu@...iatek.com>,
"obh+dt@...nel.org" <robh+dt@...nel.org>,
"kishon@...com" <kishon@...com>,
Chunfeng Yun <Chunfeng.Yun@...iatek.com>,
"hunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>,
Jitao Shi <jitao.shi@...iatek.com>,
"daniel@...ll.ch" <daniel@...ll.ch>,
"atthias.bgg@...il.com" <matthias.bgg@...il.com>,
".zabel@...gutronix.de" <p.zabel@...gutronix.de>,
"irlied@...il.com" <airlied@...il.com>,
"zysztof.kozlowski+dt@...aro.org" <krzysztof.kozlowski+dt@...aro.org>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"nux-mediatek@...ts.infradead.org"
<linux-mediatek@...ts.infradead.org>,
Mac Shen <Mac.Shen@...iatek.com>,
"vicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"zysztof.kozlowski@...aro.org" <krzysztof.kozlowski@...aro.org>,
Stuart Lee <Stuart.Lee@...iatek.com>,
"i-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
"nux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"inux-phy@...ts.infradead.org" <linux-phy@...ts.infradead.org>
Subject: Re: [PATCH v3 02/12] dt-bindings: display: mediatek: add MT8195 hdmi
bindings
Il 02/01/23 16:19, Guillaume Ranquet ha scritto:
> On Mon, 02 Jan 2023 15:14, AngeloGioacchino Del Regno
> <angelogioacchino.delregno@...labora.com> wrote:
>> Il 02/01/23 14:38, Guillaume Ranquet ha scritto:
>>> 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.
>>>
>>
>> You can as well keep the DDC as a separated driver, but register in the HDMI v1 and
>> v2 driver at probe time.
>>
>> Doing that, you won't need any devicetree node specific to any virtual device :-)
>>
>> Cheers,
>> Angelo
>>
>>
>
> Sure, but does it make any sense for HDMI v1?
> As the ddc in v1 is a real device which (in theory) can be reused by other IPs.
>
> I would see either v1 and v2 ddc exposed as a devicetree node (which
> is what I favor).
> Or v1 as a devicetree node and v2 probed directly from the hdmi code base.
>
The last option looks sensible, since v1 has an external ddc, but on v2 it's
integrated.
v1 -> dt probe
v2 -> driver probe
> Thx,
> Guillaume.
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