linux-kernel - Re: [PATCH V3 11/17] dt-bindings: arm: mediatek: Add #reset-cells property for MT8192-sys-clock

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Date:   Mon, 25 Apr 2022 09:44:15 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Rex-BC Chen <rex-bc.chen@...iatek.com>,
        "mturquette@...libre.com" <mturquette@...libre.com>,
        "sboyd@...nel.org" <sboyd@...nel.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>
Cc:     "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>,
        Chun-Jie Chen (陳浚桀) 
        <Chun-Jie.Chen@...iatek.com>,
        "wenst@...omium.org" <wenst@...omium.org>,
        Runyang Chen (陈润洋) 
        <Runyang.Chen@...iatek.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        Project_Global_Chrome_Upstream_Group 
        <Project_Global_Chrome_Upstream_Group@...iatek.com>
Subject: Re: [PATCH V3 11/17] dt-bindings: arm: mediatek: Add #reset-cells
 property for MT8192-sys-clock

On 25/04/2022 04:37, Rex-BC Chen wrote:
>>> +  '#reset-cells':
>>> +    maximum: 2
>>
>> Why this is a maximum? Usually this is const, so how do you use it
>> (with
>> what values)?
>>
> We need to let the driver compatible with previous setting in
> drivers/clk/mediatek/reset.c

Then it should be enum [1, 2], because '0' is not valid.

> There are two use cases in our reset driver:
> (Refer to [1])
> 
> 1. #reset-cells = <1>
>    When we input the argument, the older driver
> use is to calculate  
>    bank and bit by different method. From the implementation of
>    reset_xlate(), we can see if the argument number is 1, it will
>    return directly.

I understand this is an old binding with older compatibles, so this
should be restricted per each variant (allOf:if:then)... but wait, old
binding did not allow any reset-cells! You add an entirely new binding
property and already want to support some older (deprecated?) way.

> 
> 2. #reset-cells = <2>
>    The input arguments is offset and bit. When we input two arguments,
>    we can use reset_xlate() to calculate the corresponding id to assert
>    and deassert.
> 
> [1]:
> https://lore.kernel.org/all/20220422060152.13534-10-rex-bc.chen@mediatek.com/
> 
> If it's acceptable, I will add this in commit message.


Best regards,
Krzysztof