linux-kernel - Re: [PATCH 1/2] dt-bindings: crypto: qcom,prng: document SM8550

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Message-ID: <08e4a3b2-0943-4e22-957e-37079184b48b@linaro.org>
Date:   Thu, 24 Aug 2023 10:46:57 +0200
From:   neil.armstrong@...aro.org
To:     Konrad Dybcio <konrad.dybcio@...aro.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Om Prakash Singh <quic_omprsing@...cinc.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Vinod Koul <vkoul@...nel.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-crypto@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: crypto: qcom,prng: document SM8550

On 24/08/2023 10:40, Konrad Dybcio wrote:
> On 24.08.2023 08:37, Krzysztof Kozlowski wrote:
>> On 24/08/2023 01:32, Om Prakash Singh wrote:
>>>
>>>
>>> On 8/23/2023 1:25 PM, Neil Armstrong wrote:
>>>> Hi,
>>>>
>>>> On 23/08/2023 02:10, Om Prakash Singh wrote:
>>>>>
>>>>>
>>>>> On 8/22/2023 9:34 PM, Konrad Dybcio wrote:
>>>>>> On 22.08.2023 16:54, Om Prakash Singh wrote:
>>>>>>> PRNG Block on most of newer target from Qualcomm have some
>>>>>>> configuration where clock is configured by security firmware.
>>>>>>>
>>>>>>> Adding separate compatible string for each platform is overhead.
>>>>>>>
>>>>>>> We need to introduce common compatible string that can be used for
>>>>>>> all platforms with same configuration.
>>>>>>>
>>>>>>> I would suggest to use "qcom,rng-ee" for newer platform, dropping
>>>>>>> "p" also signifies it is not a Pseudo Random Number Generator.
>>>>>> Please reply inline and don't top-post.
>>>>>>
>>>>>>
>>>>>> Is this what you're trying to say?
>>>>>>
>>>>>> 1. sort out the clock requirements for designs where Linux manages it
>>>>>>      vs where the FW does so >
>>>>>> 2. introduce a new compatible for SoCs implementing a TRNG
>>>>>>
>>>>>> 3. for SoCs in 2., register the TRNG as a hwrng device
>>>>>
>>>>> Yes to all
>>>>
>>>> I can send a proposal, but that means writing a new driver for this
>>>> compatible in drivers/char/hw_random/ right ?
>>>
>>> We can add hwrng support in same driver like
>>> drivers/crypto/hisilicon/trng/trng.c
>>>
>>> As Krzysztof is suggesting we need to have platform specific compatible
>>
>> That's independent question
>>
>>> string, we can go with your change. for hwrng support I will send
>>> separate patches.
>>
>> Any bindings decision should be made now. We don't produce knowingly
>> incomplete bindings just to change them later. Therefore now you need to
>> decide whether you call it prng-ee or something else.
> Herbert already picked up the 8450 compatible last week or so.
> If we decide quickly, perhaps it can be reverted and substituted
> with the non-*P*RNG one. It would theoretically be an ABI break,
> but:
> 
> a) it would be very very prompt
> b) the dts patch hasn't been merged so there are no users
> 
> I'd be fine with that, not sure about the rest of you guys.

I'm fine for that aswell, this can be done quickly without the
hwrng part

I can quickly refresh this serie with :
1) introduce a new "qcom,trng" and move "qcom,sm8450-prng-ee" to "qcom,sm8450-trng"
2) add qcom,sm8550-prng-ee
3) add "qcom,trng"  to the driver compatible list

then afterwards, the hwrng part can be added in a separate serie.

Neil

> 
> Konrad