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

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Message-ID: <31644849-dc69-ddfc-a6b6-6ffd37d64d2b@broadcom.com>
Date:   Wed, 11 Jan 2023 10:04:16 -0800
From:   William Zhang <william.zhang@...adcom.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        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 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";

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.

Does this sound good to you?

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