On 29 June 2016 at 14:08, Linus Walleij <linus.walleij@xxxxxxxxxx> 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 AK8975 goes into active mode even if noone is going to use
> 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@xxxxxxxxxx>
> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Reviewed-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
Kind regards
Uffe
> ---
> ChangeLog v2->v3:
> - Rebase, fix commit message.
> 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 43dc1c74be9e..d26796eb0b1b 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>
> @@ -692,6 +693,8 @@ static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
> u16 buff;
> int ret;
>
> + pm_runtime_get_sync(&data->client->dev);
> +
> mutex_lock(&data->lock);
>
> ret = ak8975_start_read_axis(data, client);
> @@ -706,6 +709,9 @@ 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);
> +
> /* Swap bytes and convert to valid range. */
> buff = le16_to_cpu(buff);
> *val = clamp_t(s16, buff, -def->range, def->range);
> @@ -974,6 +980,18 @@ 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:
> @@ -988,6 +1006,9 @@ 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);
> @@ -996,6 +1017,56 @@ 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},
> @@ -1023,6 +1094,7 @@ 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
>
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