applications: serial_lte_modem: Fix asserts when pressing power pin

Asserts were enabled with PR #20040.
This has caused an assert to occur when pressing power pin,
because GPIO callback (power_pin_callback_wakeup)
called slm_at_host_power_on, which called k_sleep(),
which has an assert that it's not called from interrupt context.
Added most of the wake up operation into a worker.

Jira: LRCS-70

Signed-off-by: Tommi Rantanen <tommi.rantanen@nordicsemi.no>

Author: trantanen

applications/serial_lte_modem/src/main.c

@@ -149,14 +149,22 @@ static int configure_power_pin_interrupt(gpio_callback_handler_t handler, gpio_f
 		return err;
 	}
 
-	LOG_DBG("Configured interrupt (0x%x) on power pin (%u).", flags, pin);
+	LOG_DBG("Configured interrupt (0x%x) on power pin (%u) with handler (%p).",
+		flags, pin, handler);
 	return 0;
 }
 
+static void slm_enter_sleep_work_fn(struct k_work *)
+{
+	slm_enter_sleep();
+}
+
 static void power_pin_callback_poweroff(const struct device *, struct gpio_callback *, uint32_t)
 {
+	static K_WORK_DEFINE(work, slm_enter_sleep_work_fn);
+
 	LOG_INF("Power off triggered.");
-	slm_enter_sleep();
+	k_work_submit(&work);
 }
 
 static void poweroff_interrupt_enabler(struct k_work *)
@@ -245,7 +253,7 @@ static void power_pin_callback_enable_poweroff(const struct device *dev,
 	/* Enable the poweroff interrupt after a small delay
 	 * so that it doesn't fire right away (which it does if enabled here).
 	 */
-	k_work_schedule(&work, K_MSEC(1));
+	poweroff_interrupt_enabler(NULL);
 }
 
 static void power_pin_callback_wakeup(const struct device *dev,
@@ -276,12 +284,21 @@ static void power_pin_callback_wakeup(const struct device *dev,
 		return;
 	}
 
+	atomic_set(&callback_running, false);
+}
+
+static void power_pin_callback_wakeup(const struct device *dev,
+				      struct gpio_callback *gpio_callback, uint32_t)
+{
+	static K_WORK_DEFINE(work, power_pin_callback_wakeup_work_fn);
+
+	LOG_INF("Resuming from idle shortly...");
 	gpio_remove_callback(dev, gpio_callback);
 
 	/* Enable the poweroff interrupt only when the pin will be back to a nonactive state. */
 	configure_power_pin_interrupt(power_pin_callback_enable_poweroff, GPIO_INT_EDGE_RISING);
 
-	atomic_set(&callback_running, false);
+	k_work_submit(&work);
 }
 
 void slm_enter_idle(void)