[PATCH v3] char: hw_random: atmel-rng: disable TRNG during suspend

* [PATCH v3] char: hw_random: atmel-rng: disable TRNG during suspend
@ 2016-10-28  8:00 ` Wenyou Yang
  0 siblings, 0 replies; 4+ messages in thread
From: Wenyou Yang @ 2016-10-28  8:00 UTC (permalink / raw)
  To: Herbert Xu, Matt Mackall
  Cc: linux-arm-kernel, Nicolas Ferre, linux-crypto, Wenyou Yang, Wenyou Yang

To fix the over consumption on the VDDCore due to the TRNG enabled,
disable the TRNG during suspend, not only disable the user interface
clock (which is controlled by PMC). Because the user interface clock
is independent from any clock that may be used in the entropy source
logic circuitry.

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
---

Changes in v3:
 - Add Acked-by tag.

Changes in v2:
 - Enable the user interface first, then enable the internal clock
   when resume.

 drivers/char/hw_random/atmel-rng.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/drivers/char/hw_random/atmel-rng.c b/drivers/char/hw_random/atmel-rng.c
index 0fcc9e6..ae7cae5 100644
--- a/drivers/char/hw_random/atmel-rng.c
+++ b/drivers/char/hw_random/atmel-rng.c
@@ -48,6 +48,16 @@ static int atmel_trng_read(struct hwrng *rng, void *buf, size_t max,
 		return 0;
 }
 
+static void atmel_trng_enable(struct atmel_trng *trng)
+{
+	writel(TRNG_KEY | 1, trng->base + TRNG_CR);
+}
+
+static void atmel_trng_disable(struct atmel_trng *trng)
+{
+	writel(TRNG_KEY, trng->base + TRNG_CR);
+}
+
 static int atmel_trng_probe(struct platform_device *pdev)
 {
 	struct atmel_trng *trng;
@@ -71,7 +81,7 @@ static int atmel_trng_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
-	writel(TRNG_KEY | 1, trng->base + TRNG_CR);
+	atmel_trng_enable(trng);
 	trng->rng.name = pdev->name;
 	trng->rng.read = atmel_trng_read;
 
@@ -94,7 +104,7 @@ static int atmel_trng_remove(struct platform_device *pdev)
 
 	hwrng_unregister(&trng->rng);
 
-	writel(TRNG_KEY, trng->base + TRNG_CR);
+	atmel_trng_disable(trng);
 	clk_disable_unprepare(trng->clk);
 
 	return 0;
@@ -105,6 +115,7 @@ static int atmel_trng_suspend(struct device *dev)
 {
 	struct atmel_trng *trng = dev_get_drvdata(dev);
 
+	atmel_trng_disable(trng);
 	clk_disable_unprepare(trng->clk);
 
 	return 0;
@@ -113,8 +124,15 @@ static int atmel_trng_suspend(struct device *dev)
 static int atmel_trng_resume(struct device *dev)
 {
 	struct atmel_trng *trng = dev_get_drvdata(dev);
+	int ret;
+
+	ret = clk_prepare_enable(trng->clk);
+	if (ret)
+		return ret;
 
-	return clk_prepare_enable(trng->clk);
+	atmel_trng_enable(trng);
+
+	return 0;
 }
 
 static const struct dev_pm_ops atmel_trng_pm_ops = {
-- 
2.7.4

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