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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Tue, 28 Sep 2021 11:00:41 +0200
Message-ID: <CAMuHMdURNY5BRc6bfaYxX+k02w7mz2aRLOi9uW-qaoT3oBPFtQ@mail.gmail.com>
Subject: Re: [PATCH 1/4] crypto: nintendo-aes - add a new AES driver
To:     Joel Stanley <joel@jms.id.au>
Cc:     Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>,
        Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
        devicetree <devicetree@vger.kernel.org>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Paul Mackerras <paulus@samba.org>,
        Ash Logan <ash@heyquark.com>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        "David S. Miller" <davem@davemloft.net>,
        =?UTF-8?Q?Jonathan_Neusch=C3=A4fer?= <j.ne@posteo.net>
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On Wed, Sep 22, 2021 at 4:12 AM Joel Stanley <joel@jms.id.au> wrote:
> On Tue, 21 Sept 2021 at 21:47, Emmanuel Gil Peyrot
> <linkmauve@linkmauve.fr> wrote:
> >
> > This engine implements AES in CBC mode, using 128-bit keys only.  It is
> > present on both the Wii and the Wii U, and is apparently identical in
> > both consoles.
> >
> > The hardware is capable of firing an interrupt when the operation is
> > done, but this driver currently uses a busy loop, I’m not too sure
> > whether it would be preferable to switch, nor how to achieve that.
> >
> > It also supports a mode where no operation is done, and thus could be
> > used as a DMA copy engine, but I don’t know how to expose that to the
> > kernel or whether it would even be useful.
> >
> > In my testing, on a Wii U, this driver reaches 80.7 MiB/s, while the
> > aes-generic driver only reaches 30.9 MiB/s, so it is a quite welcome
> > speedup.
> >
> > This driver was written based on reversed documentation, see:
> > https://wiibrew.org/wiki/Hardware/AES
> >
> > Signed-off-by: Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
> > Tested-by: Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>  # on Wii U
> > ---
> >  drivers/crypto/Kconfig        |  11 ++
> >  drivers/crypto/Makefile       |   1 +
> >  drivers/crypto/nintendo-aes.c | 273 ++++++++++++++++++++++++++++++++++
> >  3 files changed, 285 insertions(+)
> >  create mode 100644 drivers/crypto/nintendo-aes.c
> >
> > diff --git a/drivers/crypto/Kconfig b/drivers/crypto/Kconfig
> > index 9a4c275a1335..adc94ad7462d 100644
> > --- a/drivers/crypto/Kconfig
> > +++ b/drivers/crypto/Kconfig
> > @@ -871,4 +871,15 @@ config CRYPTO_DEV_SA2UL
> >
> >  source "drivers/crypto/keembay/Kconfig"
> >
> > +config CRYPTO_DEV_NINTENDO
> > +       tristate "Support for the Nintendo Wii U AES engine"
> > +       depends on WII || WIIU || COMPILE_TEST
>
> This current seteup will allow the driver to be compile tested for
> non-powerpc, which will fail on the dcbf instructions.
>
> Perhaps use this instead:
>
>        depends on WII || WIIU || (COMPILE_TEST && PPC)

Or:

    depends on PPC
    depends on WII || WIIU || COMPILE_TEST

to distinguish between hard and soft dependencies.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds