linux-kernel - Re: [PATCH v2 4/7] crypto: sun4i-ss: handle BigEndian for cipher

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Date:   Wed, 23 Sep 2020 20:06:08 +0200
From:   LABBE Corentin <clabbe@...libre.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     David Miller <davem@...emloft.net>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>,
        "# 3.4.x" <stable@...r.kernel.org>
Subject: Re: [PATCH v2 4/7] crypto: sun4i-ss: handle BigEndian for cipher

On Wed, Sep 23, 2020 at 04:00:32PM +0200, Arnd Bergmann wrote:
> On Sun, Sep 20, 2020 at 8:37 PM Corentin Labbe <clabbe@...libre.com> wrote:
> >
> > Ciphers produce invalid results on BE.
> > Key and IV need to be written in LE.
> >
> > Fixes: 6298e948215f2 ("crypto: sunxi-ss - Add Allwinner Security System crypto accelerator")
> > Cc: <stable@...r.kernel.org>
> > Signed-off-by: Corentin Labbe <clabbe@...libre.com>
> > ---
> >  drivers/crypto/allwinner/sun4i-ss/sun4i-ss-cipher.c | 12 ++++++------
> >  1 file changed, 6 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/crypto/allwinner/sun4i-ss/sun4i-ss-cipher.c b/drivers/crypto/allwinner/sun4i-ss/sun4i-ss-cipher.c
> > index c6c25204780d..a05889745097 100644
> > --- a/drivers/crypto/allwinner/sun4i-ss/sun4i-ss-cipher.c
> > +++ b/drivers/crypto/allwinner/sun4i-ss/sun4i-ss-cipher.c
> > @@ -52,13 +52,13 @@ static int noinline_for_stack sun4i_ss_opti_poll(struct skcipher_request *areq)
> >
> >         spin_lock_irqsave(&ss->slock, flags);
> >
> > -       for (i = 0; i < op->keylen; i += 4)
> > -               writel(*(op->key + i / 4), ss->base + SS_KEY0 + i);
> > +       for (i = 0; i < op->keylen / 4; i++)
> > +               writel(cpu_to_le32(op->key[i]), ss->base + SS_KEY0 + i * 4);
> 
> I suspect what you actually want here is writesl() in place of the
> loop. This skips the byteswap on big-endian, rather than swapping
> each word twice.
> 
> The point is that this register seems to act as a FIFO for a byte-stream
> rather than a 32-bit fixed-endian register.
> 
>      Arnd

Thanks, using writesl() fixes the warning, but I need to keep the loop since the register is different each time.
Or does it is better to use directly __raw_writel() ?