Re: [PATCH 02/16] dt-bindings: spi: Add bcmbca-hsspi controller support

[William Zhang <william.zhang@broadcom.com>]

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On 01/11/2023 10:12 AM, Krzysztof Kozlowski wrote:
> On 11/01/2023 19:04, William Zhang wrote:
>>
>>
>> On 01/11/2023 01:02 AM, Krzysztof Kozlowski wrote:
>>> On 10/01/2023 23:18, Florian Fainelli wrote:
>>>> On 1/10/23 00:40, Krzysztof Kozlowski wrote:
>>>>>>> No, it is discouraged in such forms. Family or IP block compatibles
>>>>>>> should be prepended with a specific compatible. There were many issues
>>>>>>> when people insisted on generic or family compatibles...
>>>>>>>
>>>>>>>> Otherwise we will have to have a compatible string with chip model for
>>>>>>>> each SoC even they share the same IP. We already have more than ten of
>>>>>>>> SoCs and the list will increase.  I don't see this is a good solution too.
>>>>>>>
>>>>>>> You will have to do it anyway even with generic fallback, so I don't get
>>>>>>> what is here to gain... I also don't get why Broadcom should be here
>>>>>>> special, different than others. Why it is not a good solution for
>>>>>>> Broadcom SoCs but it is for others?
>>>>>>>
>>>>>> I saw a few other vendors like these qcom ones:
>>>>>>      qcom,spi-qup.yaml
>>>>>>          - qcom,spi-qup-v1.1.1 # for 8660, 8960 and 8064
>>>>>>          - qcom,spi-qup-v2.1.1 # for 8974 and later
>>>>>>          - qcom,spi-qup-v2.2.1 # for 8974 v2 and later
>>>>>>      qcom,spi-qup.yaml
>>>>>>          const: qcom,geni-spi
>>>>>
>>>>> IP block version numbers are allowed when there is clear mapping between
>>>>> version and SoCs using it. This is the case for Qualcomm because there
>>>>> is such clear mapping documented and available for Qualcomm engineers
>>>>> and also some of us (although not public).
>>>>>
>>>>>> I guess when individual who only has one particular board/chip and is
>>>>>> not aware of the IP family,  it is understandable to use the chip
>>>>>> specific compatible string.
>>>>>
>>>>> Family of devices is not a versioned IP block.
>>>>
>>>> Would it be acceptable to define for instance:
>>>>
>>>> - compatible = "brcm,bcm6868-hsspi", "brcm,bcmbca-hsspi";
>>>
>>> Yes, this is perfectly valid. Although it does not solve William
>>> concerns because it requires defining specific compatibles for all of
>>> the SoCs.
>>>
>>> Best regards,
>>> Krzysztof
>>>
>> As I mentioned in another email,  I would be okay to use these
>> compatibles to differentiate by ip rev and to conforms to brcm convention:
>> "brcm,bcmXYZ-hsspi", "brcm,bcmbca-hsspi-v1.0", "brcm,bcmbca-hsspi";
>> "brcm,bcmXYZ-hsspi", "brcm,bcmbca-hsspi-v1.1", "brcm,bcmbca-hsspi";
> 
> 
> Drop the version in such case, no benefits. I assume XYZ is the SoC
> model, so for example 6868.
> 
Yes XYZ is the SoC model
>>
>> In the two drivers I included in this series, it will be bound to
>> brcm,bcmbca-hsspi-v1.0 (in additional to brcm,bcm6328-hsspi) and
>> brcm,bcmbca-hsspi-v1.1 respectively.  This way we don't need to update
>> the driver with a new soc specific compatible whenever a new chips comes
>> out.
> 
> I don't understand why do you bring it now as an argument. You defined
> before that your driver will bind to the generic bcmbca compatible, so
> now it is not enough?
> 
No as we are adding chip model specific info here.  The existing driver 
spi-bcm63xx-hsspi.c only binds to brcm,bcm6328-hsspi. This driver 
supports all the chips with rev1.0 controller so I am using this 6328 
string for other chips with v1.0 in the dts patch, which is not ideal.
Now I have to add more compatible to this driver and for each new chip 
with 1.0 in the future if any.

With all the thoughts from you and Florian,  I think it is better to use 
rev compatible in the driver but add on chip model compatible in the dts.



> Best regards,
> Krzysztof
> 

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