linux-kernel - Re: [PATCH v3 2/4] crypto: exynos

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Date:   Wed, 13 Dec 2017 09:07:57 +0100
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Łukasz Stelmach <l.stelmach@...sung.com>
Cc:     robh+dt@...nel.org, Stephan Mueller <smueller@...onox.de>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S . Miller" <davem@...emloft.net>,
        Kukjin Kim <kgene@...nel.org>, linux-crypto@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH v3 2/4] crypto: exynos - Improve performance of PRNG

On Tue, Dec 12, 2017 at 5:36 PM, Łukasz Stelmach <l.stelmach@...sung.com> wrote:
> Use memcpy_fromio() instead of custom exynos_rng_copy_random() function
> to retrieve generated numbers from the registers of PRNG.

If I recall correctly, you mentioned before that it improves the
performance. If so it would be nice to mention some numbers here.

Anyway it is fine with me:
Reviewed-by: Krzysztof Kozlowski <krzk@...nel.org>

Best regards,
Krzysztof

>
> Signed-off-by: Łukasz Stelmach <l.stelmach@...sung.com>
> ---
>  drivers/crypto/exynos-rng.c | 31 ++-----------------------------
>  1 file changed, 2 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/crypto/exynos-rng.c b/drivers/crypto/exynos-rng.c
> index 825c09619eb8..dcdd444d0b3b 100644
> --- a/drivers/crypto/exynos-rng.c
> +++ b/drivers/crypto/exynos-rng.c
> @@ -131,34 +131,6 @@ static int exynos_rng_set_seed(struct exynos_rng_dev *rng,
>  }
>
>  /*
> - * Read from output registers and put the data under 'dst' array,
> - * up to dlen bytes.
> - *
> - * Returns number of bytes actually stored in 'dst' (dlen
> - * or EXYNOS_RNG_SEED_SIZE).
> - */
> -static unsigned int exynos_rng_copy_random(struct exynos_rng_dev *rng,
> -                                          u8 *dst, unsigned int dlen)
> -{
> -       unsigned int cnt = 0;
> -       int i, j;
> -       u32 val;
> -
> -       for (j = 0; j < EXYNOS_RNG_SEED_REGS; j++) {
> -               val = exynos_rng_readl(rng, EXYNOS_RNG_OUT(j));
> -
> -               for (i = 0; i < 4; i++) {
> -                       dst[cnt] = val & 0xff;
> -                       val >>= 8;
> -                       if (++cnt >= dlen)
> -                               return cnt;
> -               }
> -       }
> -
> -       return cnt;
> -}
> -
> -/*
>   * Start the engine and poll for finish.  Then read from output registers
>   * filling the 'dst' buffer up to 'dlen' bytes or up to size of generated
>   * random data (EXYNOS_RNG_SEED_SIZE).
> @@ -190,7 +162,8 @@ static int exynos_rng_get_random(struct exynos_rng_dev *rng,
>         /* Clear status bit */
>         exynos_rng_writel(rng, EXYNOS_RNG_STATUS_RNG_DONE,
>                           EXYNOS_RNG_STATUS);
> -       *read = exynos_rng_copy_random(rng, dst, dlen);
> +       *read = min_t(size_t, dlen, EXYNOS_RNG_SEED_SIZE);
> +       memcpy_fromio(dst, rng->mem + EXYNOS_RNG_OUT_BASE, *read);
>
>         return 0;
>  }
> --
> 2.11.0
>