hwrng: exynos - Fix missing configuration after suspend to RAM

After suspend to RAM the device stopped to work with ETIMEDOUT error:

$ dd if=/dev/hwrng of=/dev/null bs=1 count=16
dd: reading `/dev/hwrng': Connection timed out

In the STATUS register the bits #5 (PRNG_DONE) and #1
(SEED_SETTING_DONE) were not set. Instead PRNG_ERROR (seventh bit) was
high.

After each system suspend initialize the seed to fix the error.
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/exynos-rng.c

@@ -53,15 +53,11 @@ static void exynos_rng_writel(struct exynos_rng *rng, u32 val, u32 offset)
 	__raw_writel(val, rng->mem + offset);
 }
 
-static int exynos_init(struct hwrng *rng)
+static int exynos_rng_configure(struct exynos_rng *exynos_rng)
 {
-	struct exynos_rng *exynos_rng = container_of(rng,
-						struct exynos_rng, rng);
 	int i;
 	int ret = 0;
 
-	pm_runtime_get_sync(exynos_rng->dev);
-
 	for (i = 0 ; i < 5 ; i++)
 		exynos_rng_writel(exynos_rng, jiffies,
 				EXYNOS_PRNG_SEED_OFFSET + 4*i);
@@ -70,6 +66,17 @@ static int exynos_init(struct hwrng *rng)
 						 & SEED_SETTING_DONE))
 		ret = -EIO;
 
+	return ret;
+}
+
+static int exynos_init(struct hwrng *rng)
+{
+	struct exynos_rng *exynos_rng = container_of(rng,
+						struct exynos_rng, rng);
+	int ret = 0;
+
+	pm_runtime_get_sync(exynos_rng->dev);
+	ret = exynos_rng_configure(exynos_rng);
 	pm_runtime_put_noidle(exynos_rng->dev);
 
 	return ret;
@@ -155,10 +162,31 @@ static int exynos_rng_runtime_resume(struct device *dev)
 
 	return clk_prepare_enable(exynos_rng->clk);
 }
+
+static int exynos_rng_suspend(struct device *dev)
+{
+	return pm_runtime_force_suspend(dev);
+}
+
+static int exynos_rng_resume(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct exynos_rng *exynos_rng = platform_get_drvdata(pdev);
+	int ret;
+
+	ret = pm_runtime_force_resume(dev);
+	if (ret)
+		return ret;
+
+	return exynos_rng_configure(exynos_rng);
+}
 #endif
 
-static UNIVERSAL_DEV_PM_OPS(exynos_rng_pm_ops, exynos_rng_runtime_suspend,
-					exynos_rng_runtime_resume, NULL);
+static const struct dev_pm_ops exynos_rng_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(exynos_rng_suspend, exynos_rng_resume)
+	SET_RUNTIME_PM_OPS(exynos_rng_runtime_suspend,
+			   exynos_rng_runtime_resume, NULL)
+};
 
 static struct platform_driver exynos_rng_driver = {
 	.driver		= {