app: Add overlay for mdm-power-gpios

Adds overlay overlay-zephyr-modem.overlay for mdm-power-gpios,
so that Cellular Modem driver, which does not currently support
DTR, can power on and power off Serial Modem.

Kconfig CONFIG_SM_START_SLEEP removed. Serial Modem Will start
from sleep if mdm-power-gpios is included.

Signed-off-by: Markus Lassila <markus.lassila@nordicsemi.no>

Author: MarkusLassila

app/Kconfig

@@ -79,15 +79,6 @@ config SM_UART_TX_BUF_SIZE
 	  If the buffers are full, will send synchronously.
 	  These buffers are not used when CMUX is in use.
 
-#
-# GPIO functionality
-#
-config SM_START_SLEEP
-	bool "Enter sleep on startup"
-	help
-	  If enabled, the SiP is put into deep sleep when powered on.
-	  TODO: DTR to wake up from sleep is not implemented yet.
-
 #
 # Automatic network attach
 #

app/overlay-zephyr-modem.conf

@@ -4,8 +4,5 @@
 # SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
 #
 
-# The nRF91 is power-managed by Zephyr's modem_cellular driver running on the other chip.
-CONFIG_SM_START_SLEEP=y
-
 # Compatibility with cellular modem driver.
 CONFIG_SM_MODEM_CELLULAR=y

app/overlay-zephyr-modem.overlay

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2025 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+ / {
+	chosen {
+		ncs,sm-power-key = &power_key;
+	};
+};
+
+&dtr_uart2 {
+	/* Currently Cellular Modem driver does not drive DTR, so set it always active */
+	dtr-gpios = <&gpio0 31 (GPIO_PULL_DOWN | GPIO_ACTIVE_LOW)>;
+};
+/ {
+	power_key: sm-power-key {
+		compatible = "nordic,sm-power-key";
+		gpios = <&gpio0 22 (GPIO_PULL_UP | GPIO_ACTIVE_LOW)>;
+		status = "okay";
+	};
+};
+
+&gpio0 {
+	status = "okay";
+	/* Use PORT events to save power */
+	sense-edge-mask = <0xFFFFFFFF>;
+};

app/sample.yaml

@@ -136,9 +136,8 @@ tests:
     build_only: true
     extra_args:
       - EXTRA_CONF_FILE="overlay-cmux.conf;overlay-ppp.conf;overlay-zephyr-modem.conf"
-      - EXTRA_DTC_OVERLAY_FILE="overlay-external-mcu.overlay"
+      - EXTRA_DTC_OVERLAY_FILE="overlay-external-mcu.overlay;overlay-zephyr-modem.overlay"
     platform_allow:
-      - nrf9160dk/nrf9160/ns
       - nrf9161dk/nrf9161/ns
       - nrf9151dk/nrf9151/ns
     integration_platforms:

app/src/main.c

@@ -202,7 +202,11 @@ int start_execute(void)
 
 	LOG_INF("Serial Modem");
 
-	sm_ctrl_pin_init();
+	err = sm_ctrl_pin_init();
+	if (err) {
+		LOG_ERR("Failed to init ctrl_pin: %d", err);
+		return err;
+	}
 
 	/* This will send "READY" or "INIT ERROR" to UART so after this nothing
 	 * should be done that can fail
@@ -228,6 +232,8 @@ int main(void)
 	nrf_power_resetreas_clear(NRF_POWER_NS, 0x70017);
 	LOG_DBG("RR: 0x%08x", rr);
 
+	sm_ctrl_pin_init_gpios();
+
 	/* Init and load settings */
 	if (sm_settings_init() != 0) {
 		LOG_WRN("Failed to init sm settings");
@@ -254,13 +260,12 @@ int main(void)
 
 	check_app_fota_status();
 
-#if defined(CONFIG_SM_START_SLEEP)
-
+#if DT_HAS_CHOSEN(ncs_sm_power_key)
 	if (!(rr & NRF_POWER_RESETREAS_OFF_MASK)) { /* DETECT signal from GPIO */
 
-		sm_ctrl_pin_enter_sleep_no_uninit();
+		sm_ctrl_pin_enter_sleep_no_uninit(true);
 	}
-#endif /* CONFIG_SM_START_SLEEP */
+#endif
 
 	ret = start_execute();
 exit:

app/src/sm_ctrl_pin.c

@@ -18,11 +18,20 @@
 
 LOG_MODULE_REGISTER(sm_ctrl_pin, CONFIG_SM_LOG_LEVEL);
 
-#if DT_NODE_HAS_PROP(DT_CHOSEN(ncs_sm_uart), dtr_gpios)
+#define SM_DTR_GPIOS DT_NODE_HAS_PROP(DT_CHOSEN(ncs_sm_uart), dtr_gpios)
+#define SM_HAS_PWR_KEY DT_HAS_CHOSEN(ncs_sm_power_key)
+
+#if SM_DTR_GPIOS
 static const struct gpio_dt_spec dtr_gpio =
 	GPIO_DT_SPEC_GET_OR(DT_CHOSEN(ncs_sm_uart), dtr_gpios, {0});
 
-static struct gpio_callback gpio_cb;
+static struct gpio_callback dtr_gpio_cb;
+#endif
+#if SM_HAS_PWR_KEY
+static const struct gpio_dt_spec mdm_pwr_gpio =
+	GPIO_DT_SPEC_GET_OR(DT_CHOSEN(ncs_sm_power_key), gpios, {0});
+
+static struct gpio_callback mdm_pwr_gpio_cb;
 #endif
 
 static int ext_xtal_control(bool xtal_on)
@@ -58,7 +67,7 @@ static int ext_xtal_control(bool xtal_on)
 	return err;
 }
 
-#if DT_NODE_HAS_PROP(DT_CHOSEN(ncs_sm_uart), dtr_gpios)
+#if SM_DTR_GPIOS
 static void dtr_enable_fn(struct k_work *)
 {
 	LOG_INF("DTR pin callback work function.");
@@ -82,7 +91,7 @@ static void dtr_pin_callback(const struct device *dev, struct gpio_callback *gpi
 
 int sm_ctrl_pin_ready(void)
 {
-#if DT_NODE_HAS_PROP(DT_CHOSEN(ncs_sm_uart), dtr_gpios)
+#if SM_DTR_GPIOS
 	if (gpio_is_ready_dt(&dtr_gpio)) {
 		return 0;
 	}
@@ -91,31 +100,15 @@ int sm_ctrl_pin_ready(void)
 	return -EFAULT;
 }
 
-void sm_ctrl_pin_enter_sleep(void)
+void sm_ctrl_pin_enter_sleep_no_uninit(bool at_host_power_off)
 {
-#if DT_NODE_HAS_PROP(DT_CHOSEN(ncs_sm_uart), dtr_gpios)
-	int err;
-
-	err = sm_ctrl_pin_ready();
-	if (err) {
-		return;
-	}
-
-	/* Stop threads, uninitialize host and disable DTR UART. */
-	sm_at_host_uninit();
-
-	/* Only power off the modem if it has not been put
-	 * in flight mode to allow reducing NVM wear.
-	 */
-	if (!sm_is_modem_functional_mode(LTE_LC_FUNC_MODE_OFFLINE)) {
-		sm_power_off_modem();
+#if SM_DTR_GPIOS || SM_HAS_PWR_KEY
+	if (at_host_power_off) {
+		sm_at_host_power_off();
 	}
 
-	gpio_pin_interrupt_configure_dt(&dtr_gpio, GPIO_INT_DISABLE);
-
-	LOG_INF("Entering sleep.");
+	LOG_INF("Entering sleep. No uninit.");
 	LOG_PANIC();
-	nrf_gpio_cfg_sense_set(dtr_gpio.pin, NRF_GPIO_PIN_SENSE_LOW);
 
 	k_sleep(K_MSEC(100));
 
@@ -124,26 +117,27 @@ void sm_ctrl_pin_enter_sleep(void)
 #endif
 }
 
-/* TODO: Cellular modem driver uses pulse triggered power management, which is not suitable with
- *       the current implementation.
- */
-void sm_ctrl_pin_enter_sleep_no_uninit(void)
+void sm_ctrl_pin_enter_sleep(void)
 {
-#if DT_NODE_HAS_PROP(DT_CHOSEN(ncs_sm_uart), dtr_gpios)
-	LOG_INF("Entering sleep.");
-	LOG_PANIC();
-	nrf_gpio_cfg_sense_set(dtr_gpio.pin, NRF_GPIO_PIN_SENSE_LOW);
+#if SM_DTR_GPIOS || SM_HAS_PWR_KEY
 
-	k_sleep(K_MSEC(100));
+	/* Stop threads, uninitialize host and disable DTR UART. */
+	sm_at_host_uninit();
 
-	nrf_regulators_system_off(NRF_REGULATORS_NS);
-	assert(false);
+	/* Only power off the modem if it has not been put
+	 * in flight mode to allow reducing NVM wear.
+	 */
+	if (!sm_is_modem_functional_mode(LTE_LC_FUNC_MODE_OFFLINE)) {
+		sm_power_off_modem();
+	}
+
+	sm_ctrl_pin_enter_sleep_no_uninit(false);
 #endif
 }
 
 void sm_ctrl_pin_enter_idle(void)
 {
-#if DT_NODE_HAS_PROP(DT_CHOSEN(ncs_sm_uart), dtr_gpios)
+#if SM_DTR_GPIOS
 	LOG_INF("Entering idle.");
 	int err;
 
@@ -152,8 +146,8 @@ void sm_ctrl_pin_enter_idle(void)
 		return;
 	}
 
-	gpio_init_callback(&gpio_cb, dtr_pin_callback, BIT(dtr_gpio.pin));
-	err = gpio_add_callback_dt(&dtr_gpio, &gpio_cb);
+	gpio_init_callback(&dtr_gpio_cb, dtr_pin_callback, BIT(dtr_gpio.pin));
+	err = gpio_add_callback_dt(&dtr_gpio, &dtr_gpio_cb);
 	if (err) {
 		LOG_ERR("gpio_add_callback failed: %d", err);
 		return;
@@ -175,15 +169,70 @@ void sm_ctrl_pin_enter_shutdown(void)
 	assert(false);
 }
 
+void sm_ctrl_pin_init_gpios(void)
+{
+#if SM_DTR_GPIOS
+	nrf_gpio_cfg_sense_set(dtr_gpio.pin, NRF_GPIO_PIN_SENSE_LOW);
+#endif
+
+#if SM_HAS_PWR_KEY
+	/* Configure Modem Power GPIO */
+	if (!gpio_is_ready_dt(&mdm_pwr_gpio)) {
+		LOG_ERR("Modem Power GPIO not ready");
+		return;
+	}
+	int err = gpio_pin_configure_dt(&mdm_pwr_gpio, GPIO_INPUT);
+
+	if (err < 0) {
+		LOG_ERR("Failed to configure Modem Power GPIO (%d).", err);
+		return;
+	}
+	nrf_gpio_cfg_sense_set(mdm_pwr_gpio.pin, NRF_GPIO_PIN_SENSE_LOW);
+#endif
+}
+
+
+#if SM_HAS_PWR_KEY
+static void pwr_pin_fn(struct k_work *)
+{
+	nrf_gpio_cfg_sense_set(mdm_pwr_gpio.pin, NRF_GPIO_PIN_SENSE_LOW);
+	sm_ctrl_pin_enter_sleep();
+}
+
+static void pwr_pin_callback(const struct device *dev, struct gpio_callback *gpio_callback,
+			     uint32_t)
+{
+	static K_WORK_DELAYABLE_DEFINE(work, pwr_pin_fn);
+
+	k_work_reschedule(&work, K_MSEC(10));
+}
+#endif
+
 int sm_ctrl_pin_init(void)
 {
 	int err;
 
 	err = ext_xtal_control(true);
-	if (err < 0) {
+	if (err) {
 		LOG_ERR("Failed to enable ext XTAL: %d", err);
 		return err;
 	}
-
-	return err;
+#if SM_HAS_PWR_KEY
+	if (!gpio_is_ready_dt(&mdm_pwr_gpio)) {
+		LOG_ERR("Modem Power GPIO not ready");
+		return -ENODEV;
+	}
+	err = gpio_pin_interrupt_configure_dt(&mdm_pwr_gpio, GPIO_INT_EDGE_TO_ACTIVE);
+	if (err) {
+		LOG_ERR("Failed to configure Modem Power GPIO interrupt (%d).", err);
+		return err;
+	}
+	gpio_init_callback(&mdm_pwr_gpio_cb, pwr_pin_callback, BIT(mdm_pwr_gpio.pin));
+	err = gpio_add_callback_dt(&mdm_pwr_gpio, &mdm_pwr_gpio_cb);
+	if (err) {
+		LOG_ERR("Failed to add Modem Power GPIO callback (%d).", err);
+		return err;
+	}
+#endif
+	return 0;
 }

app/src/sm_ctrl_pin.h

@@ -32,22 +32,28 @@ void sm_ctrl_pin_enter_sleep(void);
 
 /**
  * @brief Enter sleep without uninitializing AT host.
+ *
+ * @param at_host_power_off If true, power off AT host before entering sleep.
  */
-void sm_ctrl_pin_enter_sleep_no_uninit(void);
+void sm_ctrl_pin_enter_sleep_no_uninit(bool at_host_power_off);
 
 /**
  * @brief nRF91 Series SiP enters System OFF mode.
  */
 void sm_ctrl_pin_enter_shutdown(void);
 
+/**
+ * @brief Initialize Serial Modem control pins.
+ */
+void sm_ctrl_pin_init_gpios(void);
+
 /**
  * @brief Initialize Serial Modem control pin module.
  *
  * @retval 0 on success, nonzero otherwise.
  */
 int sm_ctrl_pin_init(void);
 
-
 /** @} */
 
 #endif /* SM_CTRL_PIN_ */

dts/bindings/sm/nordic,sm-power-key.yaml

@@ -0,0 +1,13 @@
+# Copyright (c) 2025 Nordic Semiconductor ASA
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+
+description: |
+    Serial Modem power pin for Zephyr Modem.
+
+compatible: "nordic,sm-power-key"
+
+properties:
+  gpios:
+    type: phandle-array
+    description: Input. Power GPIO pin.
+    required: true