pm: device_runtime: Add helper to wait on async ops

Add a function that properly uses a mutex to check a condition before
wait on the conditional variable.

Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>

include/pm/device.h

@@ -119,6 +119,8 @@ struct pm_device {
 	struct k_work_delayable work;
 	/** Event conditional var to listen to the sync request events */
 	struct k_condvar condvar;
+	/** Condvar mutex */
+	struct k_mutex condvar_lock;
 };
 
 /** Bit position in device_pm::atomic_flags that records whether the

include/pm/device_runtime.h

@@ -109,6 +109,23 @@ int pm_device_put(const struct device *dev);
  * @retval Errno Negative errno code if failure.
  */
 int pm_device_put_sync(const struct device *dev);
+
+/**
+ * @brief Wait on a device to finish an operation.
+ *
+ * The calling thread blocks until the device finishes a @ref pm_device_put or
+ * @ref pm_device_get operation. If there is no operation in progress
+ * this function will return immediately.
+ *
+ * @param dev Pointer to device structure of the specific device driver
+ * the caller is interested in.
+ * @param timeout The timeout passed to k_condvar_wait. If a timeout happens
+ * this function will return immediately.
+ * @retval 0 If successful.
+ * @retval Errno Negative errno code if failure.
+ */
+int pm_device_wait(const struct device *dev, k_timeout_t timeout);
+
 #else
 static inline void pm_device_enable(const struct device *dev) { }
 static inline void pm_device_disable(const struct device *dev) { }
@@ -116,6 +133,8 @@ static inline int pm_device_get(const struct device *dev) { return -ENOSYS; }
 static inline int pm_device_get_sync(const struct device *dev) { return -ENOSYS; }
 static inline int pm_device_put(const struct device *dev) { return -ENOSYS; }
 static inline int pm_device_put_sync(const struct device *dev) { return -ENOSYS; }
+static inline int pm_device_wait(const struct device *dev,
+		k_timeout_t timeout) { return -ENOSYS; }
 #endif
 
 /** @} */

kernel/device.c

@@ -32,6 +32,7 @@ static inline void device_pm_state_init(const struct device *dev)
 		.usage = ATOMIC_INIT(0),
 		.lock = {},
 		.condvar = Z_CONDVAR_INITIALIZER(dev->pm->condvar),
+		.condvar_lock = Z_MUTEX_INITIALIZER(dev->pm->condvar_lock),
 	};
 #endif /* CONFIG_PM_DEVICE */
 }

subsys/pm/device_runtime.c

@@ -224,3 +224,22 @@ void pm_device_disable(const struct device *dev)
 	k_spin_unlock(&dev->pm->lock, key);
 	SYS_PORT_TRACING_FUNC_EXIT(pm, device_disable, dev);
 }
+
+int pm_device_wait(const struct device *dev, k_timeout_t timeout)
+{
+	int ret = 0;
+
+	k_mutex_lock(&dev->pm->condvar_lock, K_FOREVER);
+	while ((k_work_delayable_is_pending(&dev->pm->work)) ||
+		(atomic_get(&dev->pm->state) == PM_DEVICE_STATE_SUSPENDING) ||
+		(atomic_get(&dev->pm->state) == PM_DEVICE_STATE_RESUMING)) {
+		ret = k_condvar_wait(&dev->pm->condvar, &dev->pm->condvar_lock,
+			       timeout);
+		if (ret != 0) {
+			break;
+		}
+	}
+	k_mutex_unlock(&dev->pm->condvar_lock);
+
+	return ret;
+}