drivers: entropy: gecko_trng: Fully initialize on read

If the TRNG has been unretained, it's not sufficient to enable
the clock, it must be fully reinitialized.

This is a minimal fix to ensure entropy is accumulated after sleep.
Long term, this driver should be made to use device power
management with power domain awareness.

Upstream-status: available
Signed-off-by: Aksel Skauge Mellbye <[email protected]>
(cherry picked from commit e61c04e)

Author: asmellby

drivers/entropy/entropy_gecko_trng.c

@@ -44,6 +44,25 @@
 #endif	/* _SILICON_LABS_32B_SERIES_2_CONFIG_* */
 #endif	/* CONFIG_CRYPTO_ACC_GECKO_TRNG */
 
+static int entropy_gecko_trng_init(const struct device *dev)
+{
+	/* Enable the TRNG0 clock. */
+#ifndef CONFIG_CRYPTO_ACC_GECKO_TRNG
+	CMU_ClockEnable(cmuClock_TRNG0, true);
+
+	/* Enable TRNG0. */
+	TRNG0->CONTROL = TRNG_CONTROL_ENABLE;
+#else
+	/* Enable the CRYPTO ACC clock. */
+	CMU_ClockEnable(cmuClock_CRYPTOACC, true);
+
+	/* Enable TRNG */
+	S2_CTRL |= S2_CTRL_ENABLE;
+#endif
+
+	return 0;
+}
+
 static void entropy_gecko_trng_read(uint8_t *output, size_t len)
 {
 #ifndef CONFIG_CRYPTO_ACC_GECKO_TRNG
@@ -77,7 +96,7 @@ static int entropy_gecko_trng_get_entropy(const struct device *dev,
 	ARG_UNUSED(dev);
 
 #ifdef CONFIG_CRYPTO_ACC_GECKO_TRNG
-	CMU_ClockEnable(cmuClock_CRYPTOACC, true);
+	entropy_gecko_trng_init(dev);
 #endif
 
 	while (length) {
@@ -130,25 +149,6 @@ static int entropy_gecko_trng_get_entropy_isr(const struct device *dev,
 	}
 }
 
-static int entropy_gecko_trng_init(const struct device *dev)
-{
-	/* Enable the TRNG0 clock. */
-#ifndef CONFIG_CRYPTO_ACC_GECKO_TRNG
-	CMU_ClockEnable(cmuClock_TRNG0, true);
-
-	/* Enable TRNG0. */
-	TRNG0->CONTROL = TRNG_CONTROL_ENABLE;
-#else
-	/* Enable the CRYPTO ACC clock. */
-	CMU_ClockEnable(cmuClock_CRYPTOACC, true);
-
-	/* Enable TRNG */
-	S2_CTRL |= S2_CTRL_ENABLE;
-#endif
-
-	return 0;
-}
-
 static DEVICE_API(entropy, entropy_gecko_trng_api_funcs) = {
 	.get_entropy = entropy_gecko_trng_get_entropy,
 	.get_entropy_isr = entropy_gecko_trng_get_entropy_isr