Re: [PATCH 6/6 v2] iio: magn: ak8975: deploy runtime and system PM

[Jonathan Cameron <jic23@kernel.org>]

On 24/06/16 10:11, Linus Walleij wrote:
> This adds runtime PM support to the AK8975 driver. It solves two
> problems:
> 
> - After reading the first value the chip was left in MODE_ONCE,
>   meaning (presumably) it may be consuming more power. Now the
>   runtime PM hooks kick in and set it to POWER_DOWN.
> 
> - Regulators were simply enabled and left on, making it
>   impossible to turn the power consuming regulators off because
>   of the increased refcount. We now disable the regulators at
>   autosuspend.
> 
> - We also handle system suspend: by using pm_runtime_force_suspend()
>   and pm_runtime_force_resume() from the system PM sleep hooks,
>   the runtime PM code is managing the power also for this case.
>   It is currently not completely optimal: when the system resumes
>   the AK8974 goes into active mode even if noone is going to use
4? 

>   it: currently the force calls need to be paired, but the runtime
>   PM people are working on making it possible to leave devices
>   runtime suspended when coming back from sleep.
> 
> Inspired by my work on the BH1780 light sensor driver.
> 
> Cc: Ulf Hansson <ulf.hansson@linaro.org>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Looks good.  Will apply once the whole series will apply ;)

Jonathan
> ---
> ChangeLog v1->v2:
> - Split off an unrelated change to a separate patch.
> - Remove silly debug prints
> - Update commit description to describe system PM handling.
> ---
>  drivers/iio/magnetometer/ak8975.c | 72 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 72 insertions(+)
> 
> diff --git a/drivers/iio/magnetometer/ak8975.c b/drivers/iio/magnetometer/ak8975.c
> index 7fe92850f43c..c5398f086ad6 100644
> --- a/drivers/iio/magnetometer/ak8975.c
> +++ b/drivers/iio/magnetometer/ak8975.c
> @@ -33,6 +33,7 @@
>  #include <linux/of_gpio.h>
>  #include <linux/acpi.h>
>  #include <linux/regulator/consumer.h>
> +#include <linux/pm_runtime.h>
>  
>  #include <linux/iio/iio.h>
>  #include <linux/iio/sysfs.h>
> @@ -691,6 +692,8 @@ static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
>  	const struct ak_def *def = data->def;
>  	int ret;
>  
> +	pm_runtime_get_sync(&data->client->dev);
> +
>  	mutex_lock(&data->lock);
>  
>  	ret = ak8975_start_read_axis(data, client);
> @@ -703,6 +706,9 @@ static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
>  
>  	mutex_unlock(&data->lock);
>  
> +	pm_runtime_mark_last_busy(&data->client->dev);
> +	pm_runtime_put_autosuspend(&data->client->dev);
> +
>  	/* Clamp to valid range. */
>  	*val = clamp_t(s16, ret, -def->range, def->range);
>  	return IIO_VAL_INT;
> @@ -970,6 +976,18 @@ static int ak8975_probe(struct i2c_client *client,
>  		goto cleanup_buffer;
>  	}
>  
> +	/* Enable runtime PM */
> +	pm_runtime_get_noresume(&client->dev);
> +	pm_runtime_set_active(&client->dev);
> +	pm_runtime_enable(&client->dev);
> +	/*
> +	 * The device comes online in 500us, so add two orders of magnitude
> +	 * of delay before autosuspending: 50 ms.
> +	 */
> +	pm_runtime_set_autosuspend_delay(&client->dev, 50);
> +	pm_runtime_use_autosuspend(&client->dev);
> +	pm_runtime_put(&client->dev);
> +
>  	return 0;
>  
>  cleanup_buffer:
> @@ -984,6 +1002,9 @@ static int ak8975_remove(struct i2c_client *client)
>  	struct iio_dev *indio_dev = i2c_get_clientdata(client);
>  	struct ak8975_data *data = iio_priv(indio_dev);
>  
> +	pm_runtime_get_sync(&client->dev);
> +	pm_runtime_put_noidle(&client->dev);
> +	pm_runtime_disable(&client->dev);
>  	iio_device_unregister(indio_dev);
>  	iio_triggered_buffer_cleanup(indio_dev);
>  	ak8975_set_mode(data, POWER_DOWN);
> @@ -992,6 +1013,56 @@ static int ak8975_remove(struct i2c_client *client)
>  	return 0;
>  }
>  
> +#ifdef CONFIG_PM
> +static int ak8975_runtime_suspend(struct device *dev)
> +{
> +	struct i2c_client *client = to_i2c_client(dev);
> +	struct iio_dev *indio_dev = i2c_get_clientdata(client);
> +	struct ak8975_data *data = iio_priv(indio_dev);
> +	int ret;
> +
> +	/* Set the device in power down if it wasn't already */
> +	ret = ak8975_set_mode(data, POWER_DOWN);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "Error in setting power-down mode\n");
> +		return ret;
> +	}
> +	/* Next cut the regulators */
> +	ak8975_power_off(data);
> +
> +	return 0;
> +}
> +
> +static int ak8975_runtime_resume(struct device *dev)
> +{
> +	struct i2c_client *client = to_i2c_client(dev);
> +	struct iio_dev *indio_dev = i2c_get_clientdata(client);
> +	struct ak8975_data *data = iio_priv(indio_dev);
> +	int ret;
> +
> +	/* Take up the regulators */
> +	ak8975_power_on(data);
> +	/*
> +	 * We come up in powered down mode, the reading routines will
> +	 * put us in the mode to read values later.
> +	 */
> +	ret = ak8975_set_mode(data, POWER_DOWN);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "Error in setting power-down mode\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +#endif /* CONFIG_PM */
> +
> +static const struct dev_pm_ops ak8975_dev_pm_ops = {
> +	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
> +				pm_runtime_force_resume)
> +	SET_RUNTIME_PM_OPS(ak8975_runtime_suspend,
> +			   ak8975_runtime_resume, NULL)
> +};
> +
>  static const struct i2c_device_id ak8975_id[] = {
>  	{"ak8975", AK8975},
>  	{"ak8963", AK8963},
> @@ -1019,6 +1090,7 @@ MODULE_DEVICE_TABLE(of, ak8975_of_match);
>  static struct i2c_driver ak8975_driver = {
>  	.driver = {
>  		.name	= "ak8975",
> +		.pm = &ak8975_dev_pm_ops,
>  		.of_match_table = of_match_ptr(ak8975_of_match),
>  		.acpi_match_table = ACPI_PTR(ak_acpi_match),
>  	},
>