Re: [PATCH] dt-bindings: soc: imx8mp-media-blk-ctrl: Add LDB into DT example

[Marek Vasut <marex@denx.de>]

On 6/30/22 21:31, Krzysztof Kozlowski wrote:

Hi,

[...]

>>>> diff --git a/Documentation/devicetree/bindings/soc/imx/fsl,imx8mp-media-blk-ctrl.yaml b/Documentation/devicetree/bindings/soc/imx/fsl,imx8mp-media-blk-ctrl.yaml
>>>> index b246d8386ba4a..05a19d3229830 100644
>>>> --- a/Documentation/devicetree/bindings/soc/imx/fsl,imx8mp-media-blk-ctrl.yaml
>>>> +++ b/Documentation/devicetree/bindings/soc/imx/fsl,imx8mp-media-blk-ctrl.yaml
>>>> @@ -18,11 +18,18 @@ properties:
>>>>      compatible:
>>>>        items:
>>>>          - const: fsl,imx8mp-media-blk-ctrl
>>>> +      - const: simple-mfd
>>>
>>> Not really... simple-mfd means devices is really simple and you just use
>>> it to instantiate children. However this is not simple - it's a power
>>> domain controller with several clocks and power domains as input.
>>>
>>> It's not a simple MFD, but a regular device.
>>
>> I don't understand this comment. The LDB bridge is literally two
>> registers with a few bits in this media block controller register area.
>> Can you expand on why the simple-mfd is unsuitable and what should it be
>> instead ?
> 
> Looking at the bindings you have there 10 power domains, 10 input clocks
> and a domain provider. The driver is also not that simple which is
> another argument that this is not simple-mfd. Simply, it is not simple.
> 
> What I meant, is that probably you should populate children from the
> driver instead of adding simple-mfd compatible. Once you add simple-mfd,
> you cannot remove it and children cannot use anything from the parent.

No, I don't think so.

The block controller provides those 10 power domains, those are separate 
things controlled by separate registers within the block control 
register space.

This LDB bridge are two more completely unrelated registers which have 
nothing to do with those power domains . They are just in the same 
register block because they had to put those registers somewhere. And 
they are mixed literally in the middle of the register block, because 
there was space it seems. Hence the simple-mfd is I think the right 
thing here.