Re: [PATCH 2/3] crypto: exynos - Improve performance of PRNG

[Stephan Mueller]

Am Dienstag, 5. Dezember 2017, 13:35:57 CET schrieb Åukasz Stelmach:

Hi Åukasz,

> Use memcpy_fromio() instead of custom exynos_rng_copy_random() function
> to retrieve generated numbers from the registers of PRNG.
> 
> Remove unnecessary invocation of cpu_relax().
> 
> Signed-off-by: Åukasz Stelmach <l.stelmach@xxxxxxxxxxx>
> ---
>  drivers/crypto/exynos-rng.c | 36 +++++-------------------------------
>  1 file changed, 5 insertions(+), 31 deletions(-)
> 
> diff --git a/drivers/crypto/exynos-rng.c b/drivers/crypto/exynos-rng.c
> index 894ef93ef5ec..002e9d2a83cc 100644
> --- a/drivers/crypto/exynos-rng.c
> +++ b/drivers/crypto/exynos-rng.c
> @@ -130,34 +130,6 @@ 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).
> @@ -171,6 +143,8 @@ static int exynos_rng_get_random(struct exynos_rng_dev
> *rng, {
>  	int retry = EXYNOS_RNG_WAIT_RETRIES;
> 
> +	*read = min_t(size_t, dlen, EXYNOS_RNG_SEED_SIZE);
> +
>  	if (rng->type == EXYNOS_PRNG_TYPE4) {
>  		exynos_rng_writel(rng, EXYNOS_RNG_CONTROL_START,
>  				  EXYNOS_RNG_CONTROL);
> @@ -180,8 +154,8 @@ static int exynos_rng_get_random(struct exynos_rng_dev
> *rng, }
> 
>  	while (!(exynos_rng_readl(rng,
> -			EXYNOS_RNG_STATUS) & EXYNOS_RNG_STATUS_RNG_DONE) && --retry)
> -		cpu_relax();
> +			EXYNOS_RNG_STATUS) & EXYNOS_RNG_STATUS_RNG_DONE) &&
> +	       --retry);

Is this related to the patch?
> 
>  	if (!retry)
>  		return -ETIMEDOUT;
> @@ -189,7 +163,7 @@ 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);
> +	memcpy_fromio(dst, rng->mem + EXYNOS_RNG_OUT_BASE, *read);
> 
>  	return 0;
>  }



Ciao
Stephan