[PATCH 5.18 571/879] hwrng: cn10k - Optimize cn10k_rng_read()

Greg Kroah-Hartman
2022-06-08T01:38:22Z

From: Vladis Dronov <vdronov@redhat.com>

[ Upstream commit 753d6770879894de10d74b437ab99ea380f1cad7 ]

This function assumes that sizeof(void) is 1 and arithmetic works for
void pointers. This is a GNU C extention and may not work with other
compilers. Change this by using an u8 pointer.

Also move cn10k_read_trng() out of a loop thus saving some cycles.

Fixes: 38e9791a0209 ("hwrng: cn10k - Add random number generator support")
Signed-off-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/char/hw_random/cn10k-rng.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/char/hw_random/cn10k-rng.c b/drivers/char/hw_random/cn10k-rng.c
index 35001c63648b..dd226630b67d 100644
--- a/drivers/char/hw_random/cn10k-rng.c
+++ b/drivers/char/hw_random/cn10k-rng.c
@@ -90,6 +90,7 @@ static int cn10k_rng_read(struct hwrng *hwrng, void *data,
{
struct cn10k_rng *rng = (struct cn10k_rng *)hwrng->priv;
unsigned int size;
+ u8 *pos = data;
int err = 0;
u64 value;

@@ -102,17 +103,20 @@ static int cn10k_rng_read(struct hwrng *hwrng, void *data,
while (size >= 8) {
cn10k_read_trng(rng, &value);

- *((u64 *)data) = (u64)value;
+ *((u64 *)pos) = value;
size -= 8;
- data += 8;
+ pos += 8;
}

- while (size > 0) {
+ if (size > 0) {
cn10k_read_trng(rng, &value);

- *((u8 *)data) = (u8)value;
- size--;
- data++;
+ while (size > 0) {
+ *pos = (u8)value;
+ value >>= 8;
+ size--;
+ pos++;
+ }
}

return max - size;
--
2.35.1