[PATCH 1/6] dt-bindings: mfd: add binding for Apple Mac System Management Controller

[Krzysztof Kozlowski]

On 01/09/2022 18:24, Russell King (Oracle) wrote:
> On Thu, Sep 01, 2022 at 06:15:46PM +0300, Krzysztof Kozlowski wrote:
>> On 01/09/2022 18:12, Russell King (Oracle) wrote:
>>>>> +  compatible:
>>>>> +    items:
>>>>> +      - enum:
>>>>> +        - apple,t8103-smc
>>>>
>>>> You miss two spaces of indentation on this level.
>>>
>>> Should that be picked up by the dt checker?
>>
>> I think yamllint complains about it. It is not a hard-dependency, so
>> maybe you don't have it installed.
>>
>>>
>>>>> +        - apple,t8112-smc
>>>>> +        - apple,t6000-smc
>>>>
>>>> Bring some order here - either alphabetical or by date of release (as in
>>>> other Apple schemas). I think t6000 was before t8112, so it's none of
>>>> that orders.
>>>
>>> Ok.
>>>
>>>>> +      - const: apple,smc
>>>>> +
>>>>> +  reg:
>>>>> +    description: Two regions, one for the SMC area and one for the SRAM area.
>>>>
>>>> You need constraints for size/order, so in this context list with
>>>> described items.
>>>
>>> How do I do that? I tried maxItems/minItems set to 2, but the dt checker
>>> objected to it.
>>
>> One way:
>> reg:
>>   items:
>>     - description: SMC area
>>     - description: SRAM area
>>
>> but actually this is very similar what you wrote for reg-names - kind of
>> obvious, so easier way:
>>
>> reg:
>>   maxItems: 2
> 
> Doesn't work. With maxItems: 2, the example fails, yet it correctly lists
> two regs which are 64-bit address and 64-bit size - so in total 8 32-bit
> ints.
> 
> Documentation/devicetree/bindings/mfd/apple,smc.example.dtb: smc at 23e400000: reg: [[2, 1044381696], [0, 16384], [2, 1071644672], [0, 1048576]] is too long
>         From schema: /home/rmk/git/linux-rmk/Documentation/devicetree/bindings/mfd/apple,smc.yaml
> 
> Hence, I originally had maxItems: 2, and ended up deleting it because of
> the dt checker.
> 
> With the two descriptions, it's the same failure.

Yeah, they should create same result.

> 
> I think the problem is that the checker has no knowledge in the example
> of how big each address and size element of the reg property is. So,
> it's interpreting it as four entries of 32-bit address,size pairs
> instead of two entries of 64-bit address,size pairs. Yep, that's it,
> if I increase the number of "- description" entries to four then it's
> happy.
> 
> So, what's the solution?
> 

If you open generated DTS examples (in your
kbuild-output/Documentation/devicetree/bindings/mfd/) you will see which
address/size cells are expected. By default it is I think address/size
cells=1, so you need a bus node setting it to 2.

Best regards,
Krzysztof