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

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Message-ID: <f0a50234-bc8c-09c4-e2c1-22cbeaba5c15@linaro.org>
Date:   Wed, 11 Jan 2023 19:12:52 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     William Zhang <william.zhang@...adcom.com>,
        Florian Fainelli <f.fainelli@...il.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 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.

> 
> 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?

Best regards,
Krzysztof