linux-kernel - Re: [PATCH v2 03/19] dt-bindings: power: mediatek: Add bindings for MediaTek SCPSYS

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Date:   Tue, 19 Jul 2022 10:50:29 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Tinghan Shen <tinghan.shen@...iatek.com>,
        Yong Wu <yong.wu@...iatek.com>, Joerg Roedel <joro@...tes.org>,
        Will Deacon <will@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Lee Jones <lee.jones@...aro.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        MandyJH Liu <mandyjh.liu@...iatek.com>
Cc:     iommu@...ts.linux.dev, linux-mediatek@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH v2 03/19] dt-bindings: power: mediatek: Add bindings for
 MediaTek SCPSYS

On 19/07/2022 10:17, Tinghan Shen wrote:
>>> +    syscon@...06000 {
>>> +        compatible = "mediatek,scpsys", "syscon", "simple-mfd";
>>
>> This should be a SoC-specific compatible (and filename).
> 
> Ok. I think that you mean "mediatek,mt8195-scpsys".
> I'll update it in next version.

Yes.

> 
>>
>>> +        reg = <0x10006000 0x100>;
>>> +
>>> +        spm: power-controller {
>>
>> I think you created before less-portable, quite constrained bindings for
>> power controller. You now require that mt8195-power-controller is always
>> a child of some parent device which will share its regmap/MMIO with it.
>>
>> And what if in your next block there is no scpsys block and power
>> controller is the scpsys alone? It's not possible with your bindings.
> 
> Do you mean a power controller node that looks like this?
> 
> scpsys: power-controller@...06000 {
> 	compatible = "mediatek,mt6797-scpsys";
> 	#power-domain-cells = <1>;
> 
> 	// ...
> };

Yes, I mean, with an unit address.

> 
>>
>> Wouldn't it be better to assign some address space to the
>> power-controller (now as an offset from scpsys)?
> 
> Is this mean adding an offset after the node name?
> 
> spm: power-controller@0 {

This or above. I think it does not matter for the bindings - it's an
implementation detail, whether you give to the child absolute SoC
address or you give an bus-specific (scpsys) sub-address/offset.

The point is that you have an unit address, thus in the future this
could be a device node separate from scpsys.

Best regards,
Krzysztof