linux-kernel - Re: [PATCH v11 3/3] crypto: Add Inside Secure SafeXcel EIP-93 crypto engine support

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Message-ID: <CA+_ehUzZruhT7Bko2Xm2kyOaZxUPA4vNLQhq_5V30gfjgmfcng@mail.gmail.com>
Date: Tue, 1 Apr 2025 12:54:05 +0200
From: "Christian Marangi (Ansuel)" <ansuelsmth@...il.com>
To: Herbert Xu <herbert@...dor.apana.org.au>
Cc: "David S. Miller" <davem@...emloft.net>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Antoine Tenart <atenart@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>, Waiman Long <longman@...hat.com>, 
	Boqun Feng <boqun.feng@...il.com>, Nathan Chancellor <nathan@...nel.org>, 
	Nick Desaulniers <ndesaulniers@...gle.com>, Bill Wendling <morbo@...gle.com>, 
	Justin Stitt <justinstitt@...gle.com>, linux-crypto@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	llvm@...ts.linux.dev, upstream@...oha.com, 
	Richard van Schagen <vschagen@...oud.com>
Subject: Re: [PATCH v11 3/3] crypto: Add Inside Secure SafeXcel EIP-93 crypto
 engine support

Il giorno mar 1 apr 2025 alle ore 12:08 Herbert Xu
<herbert@...dor.apana.org.au> ha scritto:
>
> On Tue, Jan 14, 2025 at 01:36:36PM +0100, Christian Marangi wrote:
> >
> > +static int eip93_send_hash_req(struct crypto_async_request *async, u8 *data,
> > +                            dma_addr_t *data_dma, u32 len, bool last)
> > +{
>
> ...
>
> > +again:
> > +     ret = eip93_put_descriptor(eip93, &cdesc);
> > +     if (ret) {
> > +             usleep_range(EIP93_RING_BUSY_DELAY,
> > +                          EIP93_RING_BUSY_DELAY * 2);
> > +             goto again;
> > +     }
> > +
> > +     /* Writing new descriptor count starts DMA action */
> > +     writel(1, eip93->base + EIP93_REG_PE_CD_COUNT);
>
> Why is there no locking here? Shouldn't this be under ring->write_lock?
>

Hi Herbert,
this is really to tell DMA that there is new packet to process and
gets decreased instantly.
The lock is used to track what descriptor index should be used in the
ring in the put and get
functions.