pm: device: helper to query power state

Adds a helper function to query whether a device is currently powered.
This can be used to determine if the chip can be initialised now, or if
it needs to be deferred.

Signed-off-by: Jordan Yates <[email protected]>

Author: Jordan Yates

include/zephyr/pm/device.h

@@ -555,6 +555,16 @@ int pm_device_power_domain_add(const struct device *dev,
  */
 int pm_device_power_domain_remove(const struct device *dev,
 				  const struct device *domain);
+
+/**
+ * @brief Check if the device is currently powered.
+ *
+ * @param dev Device instance.
+ *
+ * @retval true If device is currently powered
+ * @retval false If device is not currently powered
+ */
+bool pm_device_is_powered(const struct device *dev);
 #else
 static inline void pm_device_init_suspended(const struct device *dev)
 {
@@ -626,6 +636,11 @@ static inline int pm_device_power_domain_remove(const struct device *dev,
 	return -ENOSYS;
 }
 
+static inline bool pm_device_is_powered(const struct device *dev)
+{
+	ARG_UNUSED(dev);
+	return true;
+}
 #endif /* CONFIG_PM_DEVICE */
 
 /** @} */

subsys/pm/device.c

@@ -372,3 +372,19 @@ bool pm_device_on_power_domain(const struct device *dev)
 	return false;
 #endif
 }
+
+bool pm_device_is_powered(const struct device *dev)
+{
+#ifdef CONFIG_PM_DEVICE_POWER_DOMAIN
+	struct pm_device *pm = dev->pm;
+
+	/* If a device doesn't support PM or is not under a PM domain,
+	 * assume it is always powered on.
+	 */
+	return (pm == NULL) ||
+	       (pm->domain == NULL) ||
+	       (pm->domain->pm->state == PM_DEVICE_STATE_ACTIVE);
+#else
+	return true;
+#endif
+}