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Subject[PATCH v6 7/7] crypto: caam - limit single JD RNG output to maximum of 16 bytes
Date
In order to follow recommendation in SP800-90C (section "9.4 The
Oversampling-NRBG Construction") limit the output of "generate" JD
submitted to CAAM. See
https://lore.kernel.org/linux-crypto/VI1PR0402MB3485EF10976A4A69F90E5B0F98580@VI1PR0402MB3485.eurprd04.prod.outlook.com/
for more details.

This change should make CAAM's hwrng driver good enough to have 999
quality rating.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Cc: Chris Healy <cphealy@gmail.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Horia Geantă <horia.geanta@nxp.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Iuliana Prodan <iuliana.prodan@nxp.com>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-imx@nxp.com
---
drivers/crypto/caam/caamrng.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/crypto/caam/caamrng.c b/drivers/crypto/caam/caamrng.c
index 91ccde0240fe..2b75ffffcac9 100644
--- a/drivers/crypto/caam/caamrng.c
+++ b/drivers/crypto/caam/caamrng.c
@@ -23,7 +23,7 @@
#include "error.h"

/* length of descriptors */
-#define CAAM_RNG_MAX_FIFO_STORE_SIZE U16_MAX
+#define CAAM_RNG_MAX_FIFO_STORE_SIZE 16

#define CAAM_RNG_FIFO_LEN SZ_32K /* Must be a multiple of 2 */

@@ -134,7 +134,7 @@ static void caam_rng_fill_async(struct caam_rng_ctx *ctx)

sg_init_table(sg, ARRAY_SIZE(sg));
nents = kfifo_dma_in_prepare(&ctx->fifo, sg, ARRAY_SIZE(sg),
- CAAM_RNG_FIFO_LEN);
+ CAAM_RNG_MAX_FIFO_STORE_SIZE);
if (!nents)
return;

@@ -241,6 +241,7 @@ int caam_rng_init(struct device *ctrldev)
ctx->rng.init = caam_init;
ctx->rng.cleanup = caam_cleanup;
ctx->rng.read = caam_read;
+ ctx->rng.quality = 999;

dev_info(ctrldev, "registering rng-caam\n");

--
2.21.0
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