Zephyr Device Driver Developement dynamic Power Management Hoo in Trigger_OWN_THREAD

[ChrisBay]

Hi there, I´m totally new to Zephyr & Nordic, started with some Trainings on NRF52840DK and jumped in with a device driver developement where I took a availalbe out of Tree driver of nuvton, nau7802 and enhanced it to my purposes.

I took the the latest sensor api to orient myself here with the implementation. (Some things still to do to come fullfill the requirements)

https://docs.zephyrproject.org/latest/hardware/peripherals/sensor/index.html

Since I use here the Trigger_own Thread method my intention was to Power the nau7802 up if the device_thread is active and power the nau7802 down if thread is suspended.

I have not figured out a better way as using a method to start/stop the thread from normal_user and hook in with the 

calls of

- pm_device_runtime_put(dev);

- pm_device_runtime_get(dev);

for powering up/down the nau7802 device.

What is the intended way to achive the power management on device level? I saw examples where the power up/down hooks are withing sample fetch but in IMO for higher sample rates that´s not suitable.

Full Example Can be Found here: github.com/.../nordic_fw

int ownThread_suspend(const struct device *dev)
{
    int ret;
    struct nau7802_data *data = dev->data;
    k_thread_suspend(&data->thread);
    data->threadState = THREAD_SUSPENDED;
    LOG_INF("NAU7802_THREAD_SUSPENDED");

    /* Check if device runtime power managemeng is enabled */
    if (IS_ENABLED(CONFIG_PM_DEVICE_RUNTIME))
    {

        /* let power management system know that device is no longer needed needed  */
        ret = pm_device_runtime_put(dev);
        if (ret != 0)
        {
            LOG_DBG("PM_DEVICE_ACTION_Resuming Failed %d", ret);
        }
    }

    return 0;
}

int ownThread_resume(const struct device *dev)
{
    int ret;
    struct nau7802_data *data = dev->data;
    k_thread_resume(&data->thread);
    data->threadState = THREAD_RUNNING;
    LOG_INF("NAU7802_THREAD_RESUMED");

    if (IS_ENABLED(CONFIG_PM_DEVICE_RUNTIME))
    {
        /* Check if device runtime power managemeng is enabled */
        ret = pm_device_runtime_get(dev);
        if (ret != 0)
        {
            LOG_DBG("PM_DEVICE_ACTION_Resuming Failed %d", ret);
        }
    }

    return 0;
}

[Kazi Afroza Sultana]

Hello,

''I have not figured out a better way as using a method to start/stop the thread from normal_user and hook in with the 

calls of

- pm_device_runtime_put(dev);

- pm_device_runtime_get(dev);

for powering up/down the nau7802 device.''

 

When the device runtime power management strategy is enabled on a device, it will go into the suspend state during the initialization process. Then, when the device is to be used, it is the device driver’s responsibility to notify the power management subsystem about this fact. This can be done using the pm_device_runtime_get() function. 

When the device’s operation is complete and the device does not need to be in operational mode anymore, the device driver needs to notify the PM subsystem to let it put the device into the suspend state by calling pm_device_runtime_put().

So, your approach using pm_device_runtime_get() and pm_device_runtime_put() in your thread management logic—is valid and in accordance the with Zephyr’s intended device power management strategy (https://academy.nordicsemi.com/courses/nrf-connect-sdk-intermediate/lessons/lesson-7-device-driver-dev/topic/exercise-2-adding-power-management-to-a-custom-driver/).