linux-kernel - Re: [PATCH v7 6/9] crypto: qce: core: Add new compatibles for qce crypto driver

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Date:   Wed, 21 Sep 2022 08:27:01 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Bhupesh Sharma <bhupesh.sharma@...aro.org>,
        linux-crypto@...r.kernel.org, devicetree@...r.kernel.org
Cc:     agross@...nel.org, herbert@...dor.apana.org.au,
        linux-kernel@...r.kernel.org, robh+dt@...nel.org,
        linux-arm-msm@...r.kernel.org, thara.gopinath@...il.com,
        robh@...nel.org, andersson@...nel.org, bhupesh.linux@...il.com,
        davem@...emloft.net, Jordan Crouse <jorcrous@...zon.com>
Subject: Re: [PATCH v7 6/9] crypto: qce: core: Add new compatibles for qce
 crypto driver

On 21/09/2022 08:16, Bhupesh Sharma wrote:
> 
> 
> On 9/20/22 8:42 PM, Krzysztof Kozlowski wrote:
>> On 20/09/2022 13:40, Bhupesh Sharma wrote:
>>> Since we decided to use soc specific compatibles for describing
>>> the qce crypto IP nodes in the device-trees, adapt the driver
>>> now to handle the same.
>>>
>>> Keep the old deprecated compatible strings still in the driver,
>>> to ensure backward compatibility.
>>>
>>> Cc: Bjorn Andersson <andersson@...nel.org>
>>> Cc: Rob Herring <robh@...nel.org>
>>> Cc: herbert@...dor.apana.org.au
>>> Tested-by: Jordan Crouse <jorcrous@...zon.com>
>>> Signed-off-by: Bhupesh Sharma <bhupesh.sharma@...aro.org>
>>> ---
>>>   drivers/crypto/qce/core.c | 9 +++++++++
>>>   1 file changed, 9 insertions(+)
>>>
>>> diff --git a/drivers/crypto/qce/core.c b/drivers/crypto/qce/core.c
>>> index 63be06df5519..99ed540611ab 100644
>>> --- a/drivers/crypto/qce/core.c
>>> +++ b/drivers/crypto/qce/core.c
>>> @@ -291,8 +291,17 @@ static int qce_crypto_remove(struct platform_device *pdev)
>>>   }
>>>   
>>>   static const struct of_device_id qce_crypto_of_match[] = {
>>> +	/* Following two entries are deprecated (kept only for backward compatibility) */
>>>   	{ .compatible = "qcom,crypto-v5.1", },
>>>   	{ .compatible = "qcom,crypto-v5.4", },
>>
>> This is okay, so there is no ABI break.
> 
> Great. Thanks for the confirmation.
> 
>>> +	/* Add compatible strings as per updated dt-bindings, here: */
>>> +	{ .compatible = "qcom,ipq4019-qce", },
>>> +	{ .compatible = "qcom,ipq6018-qce", },
>>> +	{ .compatible = "qcom,ipq8074-qce", },
>>> +	{ .compatible = "qcom,msm8996-qce", },
>>> +	{ .compatible = "qcom,sdm845-qce", },
>>> +	{ .compatible = "qcom,sm8150-qce", },
>>> +	{ .compatible = "qcom,sm8250-qce", },
>>
>> This is a bit odd... you have 7 devices which are simply compatible or
>> even the same. This should be instead one compatible.
>>
>> I don't really get why do you want to deprecate "qcom,crypto-v5.1".
>> Commit msg only says "we decided" but I do not know who is "we" and "why
>> we decided like this". If you want to deprecate it, perfectly fine by
>> me, but please say in commit msg why you are doing it.
> 
> I understand. This patchset has been in flight for some time and hence I 
> might have missed sharing some detailed information about the review 
> comments and rework done along the way (in the cover letter for this 
> series).
> 
> Coming back to your concern, here is the relevant background:
> - Please see: 
> https://lore.kernel.org/linux-arm-msm/20210316222825.GA3792517@robh.at.kernel.org/
> 
> - Rob shared some comments on the v1 series regarding the soc-specific 
> compatibles. He mentioned in the above thread that 'you should stick 
> with SoC specific compatibles as *everyone* else does (including most 
> QCom bindings).'
> 
> - So, while I had proposed "qcom,crypto-v5.1" (for ipq6018) and 
> "qcom,crypto-v5.4" (for sdm845, sm8150) etc. as the compatible(s) in the 
> v1 series, I shifted to using the soc-specific compatibles from the v2 
> series, onwards.

Then the reason could be - Reviewers preferred SoC-based compatible
instead of IP-block-version-based.

What is confusing is the difference between that link and here. That
link wanted to introduce 4 different compatibles... and here you have
even 7 compatibles being the same.

> 
> - Basically, since we are going to have newer qce IP versions available 
> in near future, e.g. "qcom,crypto-v5.5" etc, and we will have 2 or more 
> SoCs also sharing 1 version, these compatibles would grow and become 
> more confusing. IMO, having a soc-specific compatible in such cases is 
> probably a much cleaner approach.
> 
> Hope this helps answer some of your concerns and provides some relevant 
> background information.

Sure, but I still think you should have only one compatible in the
driver in such case. You don't have differences between them from the
driver point of view, so the devices seem to be compatible.

If not, what are the differences?

Best regards,
Krzysztof