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

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Date:   Wed, 11 Jan 2023 10:02:50 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Florian Fainelli <f.fainelli@...il.com>,
        William Zhang <william.zhang@...adcom.com>,
        Linux SPI List <linux-spi@...r.kernel.org>,
        Broadcom Kernel List <bcm-kernel-feedback-list@...adcom.com>
Cc:     anand.gore@...adcom.com, tomer.yacoby@...adcom.com,
        dan.beygelman@...adcom.com, joel.peshkin@...adcom.com,
        jonas.gorski@...il.com, kursad.oney@...adcom.com, dregan@...l.com,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/16] dt-bindings: spi: Add bcmbca-hsspi controller
 support

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