[PATCH v2 2/4] crypto: exynos - Improve performance of PRNG
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STALE3233d
SUPERSEDED
From: Łukasz Stelmach <l.stelmach@samsung.com>
Date: 2017-12-11 14:07:02
Also in:
linux-samsung-soc, lkml
Subsystem:
crypto api, the rest · Maintainers:
Herbert Xu, "David S. Miller", Linus Torvalds
Status: Superseded by v3 (posted 2017-12-12). [go to v3]
Revision v2 (3 revisions archived).
Revisions (3)
- v1
- v2 current [diff against previous]
- v3 [diff against previous]
Cc: Marek Szyprowski <m.szyprowski@samsung.com>, Bartlomiej Zolnierkiewicz <redacted>
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.stelmach@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