linux-kernel - Re: [PATCH v1 08/25] dt-bindings: clock: mt8173: Add dummy clock ID

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Message-ID: <46edd627-c128-b979-823f-0a94fe9d425b@linaro.org>
Date:   Fri, 23 Dec 2022 10:26:35 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>, mturquette@...libre.com
Cc:     sboyd@...nel.org, matthias.bgg@...il.com, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, wenst@...omium.org,
        johnson.wang@...iatek.com, miles.chen@...iatek.com,
        fparent@...libre.com, chun-jie.chen@...iatek.com,
        sam.shih@...iatek.com, y.oudjana@...tonmail.com,
        nfraprado@...labora.com, rex-bc.chen@...iatek.com,
        ryder.lee@...nel.org, daniel@...rotopia.org,
        jose.exposito89@...il.com, yangyingliang@...wei.com,
        pablo.sun@...iatek.com, msp@...libre.com, weiyi.lu@...iatek.com,
        ikjn@...omium.org, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, devicetree@...r.kernel.org,
        kernel@...labora.com
Subject: Re: [PATCH v1 08/25] dt-bindings: clock: mt8173: Add dummy clock ID

On 23/12/2022 10:21, AngeloGioacchino Del Regno wrote:
> Il 23/12/22 09:52, Krzysztof Kozlowski ha scritto:
>> On 22/12/2022 12:48, AngeloGioacchino Del Regno wrote:
>>> Some old MediaTek clock drivers are starting the clock count (so, the
>>> clock ID) from one instead of zero and this is logically incorrect,
>>> as we should start from 0.
>>> During a cleanup an issue emerged due to that and the cleanest and
>>> shortest way to keep devicetree backwards compatibility while still
>>> performing the well deserved cleanup is to add a dummy clock where
>>> needed, with ID 0.
>>
>> Unfortunately I do not understand at all why adding dummy (fake) ID
>> cleans anything here. Unifying IDs to start from 0 is not an argument on
>> DT bindings header IDs.
>>
>> Best regards,
>> Krzysztof
>>
>>
> 
> All clocks are in one or multiple arrays, and if we don't register ID 0,
> devicetrees will reference the wrong clock, as the IDs will shift back by
> one during registration.

So what stops you to register some 0-dummy clock? Why do you need a
binding for it?

> This was done for a commonization of probe() and remove() callbacks for
> MediaTek clock drivers... since we have 3 affected SoCs (MT8173, MT2701
> and MT6779) out of *19* (soon 20), to me, it didn't make sense to write
> commonized code to address this just because of 3 out of 20 SoCs (note
> that each SoC has around 4 clock drivers).
> 
> Any suggestion to keep this one short, while not touching dt-bindings?

Just add a clock or better empty entry in your table, without touching
bindings.


Best regards,
Krzysztof