Cc: Marek Szyprowski <m.szyprow...@samsung.com>, Bartlomiej Zolnierkiewicz
<b.zolnier...@samsung.com>
Use memcpy_fromio() instead of custom exynos_rng_copy_random() function
to retrieve generated numbers from the registers of PRNG.
Rearrange the loop around cpu_relax(). In a loop with while() at the
beginning and the cpu_relax() removed the retry variable is decremented
twice (down to 98). This means, the status register is read three
times before the hardware is ready (which is very quick). Apparently,
cpu_relax() requires noticeable amount of time to execute, so it seems
better to call it for the first time before checking the status of
PRNG. The do {} while () loop decrements the retry variable only once,
which means, the time required for cpu_relax() is long enough to for
the PRNG to provide results. On the other hand, performance in this
arrangement isn't much worse than in a loop without cpu_relax().
Signed-off-by: Łukasz Stelmach <l.stelm...@samsung.com>
---
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 2f554b82f49f..7d8f658480d3 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).
@@ -180,9 +152,10 @@ static int exynos_rng_get_random(struct exynos_rng_dev
*rng,
EXYNOS_RNG_SEED_CONF);
}
- while (!(exynos_rng_readl(rng,
- EXYNOS_RNG_STATUS) & EXYNOS_RNG_STATUS_RNG_DONE) &&
--retry)
+ do {
cpu_relax();
+ } while (!(exynos_rng_readl(rng, EXYNOS_RNG_STATUS) &
+ EXYNOS_RNG_STATUS_RNG_DONE) && --retry);
if (!retry)
return -ETIMEDOUT;
@@ -190,7 +163,8 @@ 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
