Re: [PATCH 5/5] iio: magn: ak8975: deploy runtime PM

[Ulf Hansson <ulf.hansson@linaro.org>]

On 22 June 2016 at 00:18, Linus Walleij <linus.walleij@linaro.org> 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.
>
> 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>
> ---
>  drivers/iio/magnetometer/ak8975.c | 80 ++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 78 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iio/magnetometer/ak8975.c b/drivers/iio/magnetometer/ak8975.c
> index 1c6e4157a91f..71a8e3348b8a 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;
> @@ -970,26 +976,95 @@ 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:
>         iio_triggered_buffer_cleanup(indio_dev);
>  power_off:
> -       ak8975_power_off(client);
> +       ak8975_power_off(data);

Is this really related to this change?

>         return err;
>  }
>
>  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_power_off(client);
> +       ak8975_set_mode(data, POWER_DOWN);
> +       ak8975_power_off(data);

I think these two last lines deserves as separate patch.

> +
> +       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;
> +
> +       dev_info(&client->dev, "%s\n", __func__);

Perhaps remove this print, seems like a leftover for a debug exercise. :-)

> +       /* 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;
> +
> +       dev_info(&client->dev, "%s\n", __func__);

Ditto.

> +       /* 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)

The system PM support isn't mentioned in the change log.

I don't mind that you add it within $subject patch, just add some
words about it in the changelog. Perhaps you can mention that you
"deploy system PM support via the runtime PM centric approach".

> +       SET_RUNTIME_PM_OPS(ak8975_runtime_suspend,
> +                          ak8975_runtime_resume, NULL)
> +};
> +
>  static const struct i2c_device_id ak8975_id[] = {
>         {"ak8975", AK8975},
>         {"ak8963", AK8963},
> @@ -1017,6 +1092,7 @@ 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),
>         },
> --
> 2.4.11
>

Nice work!

Kind regards
Uffe