Re: [PATCH v9 01/22] dt-bindings: ARM: Mediatek: Add new document bindings of imp i2c wrapper controller

[Matthias Brugger <matthias.bgg@gmail.com>]

On 10/06/2021 19:41, Stephen Boyd wrote:
> Quoting Matthias Brugger (2021-06-08 07:45:49)
>>
>>
>> On 07/06/2021 07:20, Chun-Jie Chen wrote:
>>> On Wed, 2021-06-02 at 12:12 -0500, Rob Herring wrote:
>>>>> +
>>>>> +description:
>>>>> +  The Mediatek imp i2c wrapper controller provides functional
>>>>> configurations and clocks to the system.
>>>>> +
>>>>> +properties:
>>>>> +  compatible:
>>>>> +    items:
>>>>> +      - enum:
>>>>> +          - mediatek,mt8192-imp_iic_wrap_c
>>>>> +          - mediatek,mt8192-imp_iic_wrap_e
>>>>> +          - mediatek,mt8192-imp_iic_wrap_s
>>>>> +          - mediatek,mt8192-imp_iic_wrap_ws
>>>>> +          - mediatek,mt8192-imp_iic_wrap_w
>>>>> +          - mediatek,mt8192-imp_iic_wrap_n
>>>>
>>>> Looks to me like these are all the same h/w, but just have differing 
>>>> sets of clocks. That's not really a reason to have different 
>>>> compatibles. 
>>>>
>>>> If you need to know what clocks are present, you can walk the DT for 
>>>> all 'clocks' properties matching this clock controller instance. Or
>>>> use 
>>>> 'clock-indices' to define which ones are present.
> 
> Is the idea to use clock-indices and then list all the clock ids in
> there and match them up at driver probe time to register the clocks
> provided by the IO region? Feels like we'll do a lot of parsing at each
> boot to match up structures and register clks with the clk framework.
> 
> If it's like other SoCs then the clk id maps to a hard macro for a type
> of clk, and those hard macros have been glued together with other clks
> and then partitioned into different IO regions to make up a clock
> controller. Or maybe in this case, those clk hard macros have been
> scattered into each IP block like SPI, i2c, uart, etc. so that the clock
> controller doesn't really exist and merely the gates and rate control
> (mux/divider) for the clk that's clocking some particular IP block all
> live inside the IP wrapper. If it's this case then I hope there are a
> bunch of PLLs that are fixed rate so that the i2c clk doesn't have to go
> outside the wrapper to change frequency (of which there should be two
> "standard" frequencies anyway).
> 
>>>>
>>>> Rob
>>>
>>> Some module is divided to sub-modules which are designed in different
>>> h/w blocks for different usage, and if we want to use the same
>>> compatible to present these h/w blocks, we need to move the clock data
>>> provided by these h/w blocks to dts, but we usually use different
>>> compatible to get the h/w blocks data in
>>> Mediatek's clock driver, so do you suggest to register clock provided
>>> by different h/w blocks using same compatible?
>>>
>>
>> The mapping of them is as following:
>> imp_iic_wrap_c:  11007000
>> imp_iic_wrap_e:  11cb1000
>> imp_iic_wrap_s:  11d03000
>> imp_iic_wrap_ws: 11d23000
>> imp_iic_wrap_w:  11e01000
>> imp_iic_wrap_n:  11f02000
>>
> 
> Sure. What is their purpose though? Are they simply a bunch of different
> i2c clks?
> 

That would be need to be answered by MediaTek as I don't have access to any
documentation.

Regards,
Matthias

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