linux-kernel - [PATCH 2/4] hwrng: exynos - Add timeout for waiting on init done

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Date:	Mon, 19 Oct 2015 13:37:40 +0900
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Kukjin Kim <kgene@...nel.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Matt Mackall <mpm@...enic.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-crypto@...r.kernel.org
Cc:	Heiner Kallweit <hkallweit1@...il.com>
Subject: [PATCH 2/4] hwrng: exynos - Add timeout for waiting on init done

Driver may hang waiting indefinitely for PRNG to finish its
initialization stage. Instead of stalling return -ETIMEDOUT error.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
---
 drivers/char/hw_random/exynos-rng.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/char/hw_random/exynos-rng.c b/drivers/char/hw_random/exynos-rng.c
index dc4701fd814f..dfaaaafb8ddd 100644
--- a/drivers/char/hw_random/exynos-rng.c
+++ b/drivers/char/hw_random/exynos-rng.c
@@ -81,14 +81,17 @@ static int exynos_read(struct hwrng *rng, void *buf,
 	struct exynos_rng *exynos_rng = container_of(rng,
 						struct exynos_rng, rng);
 	u32 *data = buf;
+	int retry = 100;
 
 	pm_runtime_get_sync(exynos_rng->dev);
 
 	exynos_rng_writel(exynos_rng, PRNG_START, 0);
 
 	while (!(exynos_rng_readl(exynos_rng,
-			EXYNOS_PRNG_STATUS_OFFSET) & PRNG_DONE))
+			EXYNOS_PRNG_STATUS_OFFSET) & PRNG_DONE) && --retry)
 		cpu_relax();
+	if (!retry)
+		return -ETIMEDOUT;
 
 	exynos_rng_writel(exynos_rng, PRNG_DONE, EXYNOS_PRNG_STATUS_OFFSET);
 
-- 
1.9.1

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