linux-kernel - [PATCH v3 4/6] hwrng: exynos: Implement bus clock control

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Date: Thu, 20 Jun 2024 18:13:37 -0500
From: Sam Protsenko <semen.protsenko@...aro.org>
To: Łukasz Stelmach <l.stelmach@...sung.com>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>
Cc: Anand Moon <linux.amoon@...il.com>,
	Olivia Mackall <olivia@...enic.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Alim Akhtar <alim.akhtar@...sung.com>,
	linux-samsung-soc@...r.kernel.org,
	linux-crypto@...r.kernel.org,
	devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3 4/6] hwrng: exynos: Implement bus clock control

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

Signed-off-by: Sam Protsenko <semen.protsenko@...aro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Reviewed-by: Anand Moon <linux.amoon@...il.com>
---
Changes in v3:
  - Added missing '\n' in dev_err_probe()
  - Added R-b tag from Krzysztof
  - Added R-b tag from Anand

Changes in v2:
  - Used devm_clk_get_optional_enabled() to avoid calling
    clk_prepare_enable() for PCLK

 drivers/char/hw_random/exynos-trng.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/char/hw_random/exynos-trng.c b/drivers/char/hw_random/exynos-trng.c
index 997bd22f4498..6ef2ee6c9804 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;
 };
 
@@ -141,6 +142,13 @@ static int exynos_trng_probe(struct platform_device *pdev)
 		goto err_clock;
 	}
 
+	trng->pclk = devm_clk_get_optional_enabled(&pdev->dev, "pclk");
+	if (IS_ERR(trng->pclk)) {
+		ret = dev_err_probe(&pdev->dev, PTR_ERR(trng->pclk),
+				    "Could not get pclk\n");
+		goto err_clock;
+	}
+
 	ret = devm_hwrng_register(&pdev->dev, &trng->rng);
 	if (ret) {
 		dev_err(&pdev->dev, "Could not register hwrng device.\n");
-- 
2.39.2