samples: boards: stm32: Add example for STOP3 mode on STM32U5

Simple blinky example, but using STOP3 mode. When in STOP3 mode,
GPIOs are not driven, but only pull-up or pull-down can be enabled
based on value in PWR registers.

Signed-off-by: Adam Berlinger <[email protected]>

Author: ABESTM

boards/st/nucleo_u575zi_q/nucleo_u575zi_q-common.dtsi

@@ -199,3 +199,13 @@ zephyr_udc0: &usbotg_fs {
 &vbat4 {
 	status = "okay";
 };
+
+&clk_lsi {
+	status = "okay";
+};
+
+stm32_lp_tick_source: &lptim1 {
+	clocks = <&rcc STM32_CLOCK_BUS_APB3 0x00000800>,
+		 <&rcc STM32_SRC_LSI LPTIM1_SEL(1)>;
+	status = "okay";
+};

samples/boards/stm32/power_mgmt/stop3/CMakeLists.txt

@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(stm32_pm_stop3)
+
+target_sources(app PRIVATE src/main.c)

samples/boards/stm32/power_mgmt/stop3/README.rst

@@ -0,0 +1,38 @@
+.. _stm32-pm-stop3:
+
+STM32 PM STOP3 mode
+###################
+
+Overview
+********
+
+This sample is a minimum application to demonstrate basic power management
+behavior in a basic blinking LED set up and STM32U5 STOP3 low power mode.
+
+.. _stm32-pm-stop3-requirements:
+
+Requirements
+************
+
+At the moment, only ``nucleo_u575zi_q`` board is supported.
+The board shall have an RTC to use it during the standby mode as a replacement
+for LPTIM (which is disabled).
+
+Building and Running
+********************
+
+Build and flash examples as follows:
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/boards/stm32/power_mgmt/stop3
+   :board: nucleo_u575zi_q
+   :goals: build flash
+   :compact:
+
+After flashing, the LED starts to blink.
+
+PM configurations
+*****************
+
+By default, :kconfig:option:`CONFIG_PM_DEVICE` and :kconfig:option:`CONFIG_PM_DEVICE_RUNTIME`
+are enabled.

samples/boards/stm32/power_mgmt/stop3/boards/nucleo_u575zi_q.overlay

@@ -0,0 +1,22 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Copyright (c) 2024 STMicroelectronics
+ */
+
+/ {
+	chosen {
+		st,lptim-stdby-timer = &rtc;
+	};
+};
+
+&cpu0 {
+	cpu-power-states = <&stop0 &stop1 &stop2 &stop3>;
+};
+
+&rtc {
+	status = "okay";
+	clocks = <&rcc STM32_CLOCK_BUS_APB3 0x00200000>,
+			<&rcc STM32_SRC_LSI RTC_SEL(2)>;
+	prescaler = <32768>;
+};

samples/boards/stm32/power_mgmt/stop3/prj.conf

@@ -0,0 +1,5 @@
+CONFIG_PM=y
+CONFIG_PM_DEVICE=y
+CONFIG_PM_DEVICE_RUNTIME=y
+CONFIG_PM_DEVICE_RUNTIME_EXCLUSIVE=n
+CONFIG_ASSERT=y

samples/boards/stm32/power_mgmt/stop3/sample.yaml

@@ -0,0 +1,14 @@
+sample:
+  name: STM32 STOP3 Power Management
+tests:
+  sample.boards.stm32.power_mgmt.stop3:
+    tags:
+      - LED
+      - power
+    harness: console
+    platform_allow: nucleo_u575zi_q
+    harness_config:
+      type: one_line
+      regex:
+        - "Device ready"
+    extra_args: "CONFIG_DEBUG=y"

samples/boards/stm32/power_mgmt/stop3/src/main.c

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2024 STMicroelectronics
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/kernel.h>
+#include <zephyr/device.h>
+#include <zephyr/devicetree.h>
+#include <zephyr/drivers/gpio.h>
+#include <zephyr/sys/printk.h>
+#include <stm32u5xx_ll_pwr.h>
+#include <gpio/gpio_stm32.h>
+
+#define SLEEP_TIME_MS   2000
+
+static const struct gpio_dt_spec led =
+	GPIO_DT_SPEC_GET(DT_ALIAS(led0), gpios);
+
+int main(void)
+{
+	bool led_is_on = true;
+
+	/* Compute GPIO port to be passed to LL_PWR_EnableGPIOPullUp etc. */
+	const struct gpio_stm32_config *cfg = led.port->config;
+	uint32_t pwr_port = ((uint32_t)LL_PWR_GPIO_PORTA) + (cfg->port * 8);
+
+	__ASSERT_NO_MSG(gpio_is_ready_dt(&led));
+
+	printk("Device ready\n");
+	gpio_pin_configure_dt(&led, GPIO_OUTPUT_ACTIVE);
+
+	/* Enable the pull-up/pull-down feature globally.
+	 * User can decide to not use this feature to further reduce power consumption
+	 *
+	 * This configuration is active only in STOP3 mode, so no need to disable it
+	 * during wake up
+	 */
+	LL_PWR_EnablePUPDConfig();
+
+	while (true) {
+		gpio_pin_set(led.port, led.pin, (int)led_is_on);
+		/* In STOP3, GPIOs are disabled. Only pull-up/pull-down can be enabled.
+		 * So we enable pull-up/pull-down based on LED status
+		 */
+		if (led_is_on) {
+			LL_PWR_DisableGPIOPullDown(pwr_port, (1 << led.pin));
+			LL_PWR_EnableGPIOPullUp(pwr_port, (1 << led.pin));
+		} else {
+			LL_PWR_DisableGPIOPullUp(pwr_port, (1 << led.pin));
+			LL_PWR_EnableGPIOPullDown(pwr_port, (1 << led.pin));
+		}
+
+		k_msleep(SLEEP_TIME_MS);
+		led_is_on = !led_is_on;
+	}
+	return 0;
+}