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Subject: Re: [PATCH 07/18] MIPS: DTS: jz4780: fix otg node as reported by
 dtbscheck
From:   "H. Nikolaus Schaller" <hns@goldelico.com>
In-Reply-To: <3e95f567-03f5-bf9c-1856-9fe602e9b025@linaro.org>
Date:   Sat, 9 Apr 2022 15:53:31 +0200
Cc:     Rob Herring <robh+dt@kernel.org>,
        Paul Cercueil <paul@crapouillou.net>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
        linux-mips@vger.kernel.org, letux-kernel@openphoenux.org
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 <bd19b6eb-d53a-b665-749d-46c275c85ccc@linaro.org>
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 <3e95f567-03f5-bf9c-1856-9fe602e9b025@linaro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
        =?utf-8?B?IuWRqOeQsOadsCAoWmhvdSBZYW5qaWUpIg==?= 
        <zhouyanjie@wanyeetech.com>
Precedence: bulk


> Am 09.04.2022 um 15:44 schrieb Krzysztof Kozlowski =
<krzysztof.kozlowski@linaro.org>:
>=20
> On 09/04/2022 15:32, H. Nikolaus Schaller wrote:
>>=20
>>=20
>>> Am 09.04.2022 um 15:15 schrieb Krzysztof Kozlowski =
<krzysztof.kozlowski@linaro.org>:
>>>=20
>>> On 09/04/2022 15:05, H. Nikolaus Schaller wrote:
>>>>>=20
>>>>> This looks wrong, the block usually should have a specific =
compatible.
>>>>> Please mention why it does not.
>>>>=20
>>>> Well, I did not even have that idea that it could need an =
explanation.
>>>>=20
>>>> There is no "ingenic,jz4780-otg" and none is needed here to make it =
work.
>>>=20
>>> Make it work in what terms? We talk about hardware description, =
right?
>>=20
>> Yes.
>>=20
>>>=20
>>>>=20
>>>> Therefore the generic "snps,dwc2" is sufficient.
>>>=20
>>> No, you are mixing now driver behavior (is sufficient) with hardware
>>> description.
>>=20
>> No. "snps,dwc2" is a hardware description for a licensed block.
>> Not a driver behavior.
>=20
> snps,dwc2 matches the original block, not necessarily this
> implementation. Unless you are sure?

I assume. Nobody has reported an issue without having any specific =
jz4780 driver in place.
Well, that is only evidence, not bullet proof.

>=20
>>=20
>>> Most of licensed blocks require the specific compatible to
>>> differentiate it.
>>=20
>> If there is a need to differentiate.
>=20
> No, regardless whether there is a need currently, most of them have
> specific compatibles, because there are some minor differences. Even =
if
> difference is not visible from programming model or wiring, it might
> justify it's own specific compatible. For example because maybe once
> that tiny difference will require some changes.
>=20
> Someone added the ingenic compatible, so why do you assume that one =
tool
> (bindings) is correct but other piece of code (using specific
> compatible) is not? You use the argument "bindings warning" which is =
not
> enough. Argument that blocks are 100% same, is good enough, if you are
> sure. Just use it in commit msg. But are you sure that these are the
> same? Same pins, same programming model (entire model, not used by =
Linux)?

The compatible ingenic,jz4780-otg was introduced in =
158c774d3c64859e84dd20e04d5fb18c8d3d318e.
Hence I have added Yanjie for clarification why he added it in the .dts =
and not in the bindings.

BR and thanks,
Nikolaus