[PATCH 4/7] hwrng: exynos: Implement bus clock control

[Sam Protsenko <semen.protsenko@linaro.org>]

Some SoCs like Exynos850 might require the SSS bus clock (PCLK) to be
enabled in order to access TRNG registers. Add and handle optional PCLK
clock accordingly to make it possible.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
---
 drivers/char/hw_random/exynos-trng.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/drivers/char/hw_random/exynos-trng.c b/drivers/char/hw_random/exynos-trng.c
index 88a5088ed34d..4520a280134c 100644
--- a/drivers/char/hw_random/exynos-trng.c
+++ b/drivers/char/hw_random/exynos-trng.c
@@ -47,7 +47,8 @@
 struct exynos_trng_dev {
 	struct device	*dev;
 	void __iomem	*mem;
-	struct clk	*clk;
+	struct clk	*clk;	/* operating clock */
+	struct clk	*pclk;	/* bus clock */
 	struct hwrng	rng;
 };
 
@@ -141,10 +142,23 @@ static int exynos_trng_probe(struct platform_device *pdev)
 		goto err_clock;
 	}
 
+	trng->pclk = devm_clk_get_optional(&pdev->dev, "pclk");
+	if (IS_ERR(trng->pclk)) {
+		ret = dev_err_probe(&pdev->dev, PTR_ERR(trng->pclk),
+				    "cannot get pclk");
+		goto err_clock;
+	}
+
+	ret = clk_prepare_enable(trng->pclk);
+	if (ret) {
+		dev_err(&pdev->dev, "Could not enable the pclk.\n");
+		goto err_clock;
+	}
+
 	ret = clk_prepare_enable(trng->clk);
 	if (ret) {
 		dev_err(&pdev->dev, "Could not enable the clk.\n");
-		goto err_clock;
+		goto err_clock_enable;
 	}
 
 	ret = devm_hwrng_register(&pdev->dev, &trng->rng);
@@ -160,6 +174,9 @@ static int exynos_trng_probe(struct platform_device *pdev)
 err_register:
 	clk_disable_unprepare(trng->clk);
 
+err_clock_enable:
+	clk_disable_unprepare(trng->pclk);
+
 err_clock:
 	pm_runtime_put_noidle(&pdev->dev);
 
@@ -174,6 +191,7 @@ static void exynos_trng_remove(struct platform_device *pdev)
 	struct exynos_trng_dev *trng = platform_get_drvdata(pdev);
 
 	clk_disable_unprepare(trng->clk);
+	clk_disable_unprepare(trng->pclk);
 
 	pm_runtime_put_sync(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
-- 
2.39.2