On Tue, Dec 5, 2017 at 1:35 PM, Łukasz Stelmach <l.stelmach@xxxxxxxxxxx> wrote:
> 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: Łukasz 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);
> +
Do not set *read on error path. Only on success. Although now it will
not matter but that is the expected behavior - if possible, do not
affect state outside of a block in case of error.
> 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);
It looks like unrelated change so split it into separate commit with
explanation why you are changing the common busy-loop pattern.
exynos_rng_readl() uses relaxed versions of readl() so I would expect
here cpu_relax().
Best regards,
Krzysztof
