From 9f52fac1eaed7bd34fb5fd072176ca8f3e1d909c Mon Sep 17 00:00:00 2001
From: Erwan Gouriou <erwan.gouriou@st.com>
Date: Wed, 26 Jul 2023 16:10:43 +0200
Subject: [PATCH] driver: entropy: stm32: Enable PM

Enable PM on STM32 entropy driver.
Only supports PM_DEVICE for now, runtime support will be added later.

Signed-off-by: Erwan Gouriou <erwan.gouriou@st.com>
---
 drivers/entropy/entropy_stm32.c | 50 ++++++++++++++++++++++++++++++++-
 1 file changed, 49 insertions(+), 1 deletion(-)

diff --git a/drivers/entropy/entropy_stm32.c b/drivers/entropy/entropy_stm32.c
index 9f2ad136203..cecff05e9e3 100644
--- a/drivers/entropy/entropy_stm32.c
+++ b/drivers/entropy/entropy_stm32.c
@@ -24,6 +24,7 @@
 #include <stm32_ll_rng.h>
 #include <stm32_ll_system.h>
 #include <zephyr/sys/printk.h>
+#include <zephyr/pm/device.h>
 #include <zephyr/drivers/clock_control.h>
 #include <zephyr/drivers/clock_control/stm32_clock_control.h>
 #include <zephyr/irq.h>
@@ -639,13 +640,60 @@ static int entropy_stm32_rng_init(const struct device *dev)
 	return 0;
 }
 
+#ifdef CONFIG_PM_DEVICE
+static int entropy_stm32_rng_pm_action(const struct device *dev,
+				       enum pm_device_action action)
+{
+	struct entropy_stm32_rng_dev_data *dev_data = dev->data;
+	const struct entropy_stm32_rng_dev_cfg *dev_cfg = dev->config;
+	RNG_TypeDef *rng = dev_data->rng;
+	int res = 0;
+
+	switch (action) {
+	case PM_DEVICE_ACTION_SUSPEND:
+		LL_RNG_Disable(rng);
+
+#ifdef CONFIG_SOC_SERIES_STM32WBAX
+		uint32_t wait_cycles, rng_rate;
+
+		if (clock_control_get_rate(dev_data->clock,
+				(clock_control_subsys_t) &dev_cfg->pclken[0],
+				&rng_rate) < 0) {
+			return -EIO;
+		}
+
+		wait_cycles = SystemCoreClock / rng_rate * 2;
+
+		for (int i = wait_cycles; i >= 0; i--) {
+		}
+#endif /* CONFIG_SOC_SERIES_STM32WBAX */
+
+		res = clock_control_off(dev_data->clock,
+				(clock_control_subsys_t)&dev_cfg->pclken[0]);
+		break;
+	case PM_DEVICE_ACTION_RESUME:
+		res = clock_control_on(dev_data->clock,
+				(clock_control_subsys_t)&dev_cfg->pclken[0]);
+		LL_RNG_Enable(rng);
+		break;
+	default:
+		return -ENOTSUP;
+	}
+
+	return res;
+}
+#endif /* CONFIG_PM_DEVICE */
+
 static const struct entropy_driver_api entropy_stm32_rng_api = {
 	.get_entropy = entropy_stm32_rng_get_entropy,
 	.get_entropy_isr = entropy_stm32_rng_get_entropy_isr
 };
 
+PM_DEVICE_DT_INST_DEFINE(0, entropy_stm32_rng_pm_action);
+
 DEVICE_DT_INST_DEFINE(0,
-		    entropy_stm32_rng_init, NULL,
+		    entropy_stm32_rng_init,
+		    PM_DEVICE_DT_INST_GET(0),
 		    &entropy_stm32_rng_data, &entropy_stm32_rng_config,
 		    PRE_KERNEL_1, CONFIG_ENTROPY_INIT_PRIORITY,
 		    &entropy_stm32_rng_api);