linux-kernel - Re: [PATCH 2/7] crypto: stm32

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Message-ID: <050aa1fb-34ab-b9e0-7772-af53ec32d312@foss.st.com>
Date:   Thu, 13 Jul 2023 09:59:48 +0200
From:   Thomas BOURGOIN <thomas.bourgoin@...s.st.com>
To:     Linus Walleij <linus.walleij@...aro.org>
CC:     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>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Lionel Debieve <lionel.debieve@...s.st.com>,
        <linux-crypto@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/7] crypto: stm32 - add new algorithms support

Hi Linus,

On 7/13/23 00:56, Linus Walleij wrote:
> Yes this fixes the bug and the tests pass fine 😄

Great news

> I wonder why SHA1 was affected? Same codepath?

Yes the number of CSR to save is the same for SHA256 and SHA1. You can 
look at the 'Context swapping' chapter (47.3.3) in the reference manual 
for UX500. There is a note at the end telling that you do not have to 
save all 54 register if you do HASH operation, only 38 are necessary :
  > If the context swap does not involve HMAC operations, registers 
cs_rk0 to cs_rk7 and
> cs_rh0 to cs_rh7 can be ignored
Best regards,

Thomas