linux-kernel - [PATCH 2/2] hwrng: imx-rngc - reasonable timeout for initial seed

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Date:   Tue, 12 Sep 2023 16:31:18 +0200
From:   Martin Kaiser <martin@...ser.cx>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     linux-crypto@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Martin Kaiser <martin@...ser.cx>
Subject: [PATCH 2/2] hwrng: imx-rngc - reasonable timeout for initial seed

Set a more reasonable timeout for calculating the initial seed.

The reference manuals says that "The initial seed takes approximately
2,000,000 clock cycles." The rngc peripheral clock runs at >= 33.25MHz,
so seeding takes at most 60ms.

A timeout of 200ms is more appropriate than the current value of 3
seconds.

Signed-off-by: Martin Kaiser <martin@...ser.cx>
---
 drivers/char/hw_random/imx-rngc.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/char/hw_random/imx-rngc.c b/drivers/char/hw_random/imx-rngc.c
index 127c292dfbbf..118a72acb99b 100644
--- a/drivers/char/hw_random/imx-rngc.c
+++ b/drivers/char/hw_random/imx-rngc.c
@@ -51,9 +51,8 @@
 
 #define RNGC_ERROR_STATUS_STAT_ERR	0x00000008
 
-#define RNGC_TIMEOUT  3000 /* 3 sec */
-
 #define RNGC_SELFTEST_TIMEOUT 2500 /* us */
+#define RNGC_SEED_TIMEOUT      200 /* ms */
 
 static bool self_test = true;
 module_param(self_test, bool, 0);
@@ -184,7 +183,8 @@ static int imx_rngc_init(struct hwrng *rng)
 		cmd = readl(rngc->base + RNGC_COMMAND);
 		writel(cmd | RNGC_CMD_SEED, rngc->base + RNGC_COMMAND);
 
-		ret = wait_for_completion_timeout(&rngc->rng_op_done, msecs_to_jiffies(RNGC_TIMEOUT));
+		ret = wait_for_completion_timeout(&rngc->rng_op_done,
+						  msecs_to_jiffies(RNGC_SEED_TIMEOUT));
 		if (!ret) {
 			ret = -ETIMEDOUT;
 			goto err;
-- 
2.39.2