Re: [PATCH v3 4/4] iio: magnetometer: ak8975: Add gpio reset support

Stephan Gerhold
2020-05-19T13:26:35Z

On Tue, May 19, 2020 at 02:43:54PM +0200, Jonathan Albrieux wrote:
> According to AK09911 datasheet, if reset gpio is provided then
> deassert reset on ak8975_power_on() and assert reset on ak8975_power_off().
>
> Without reset's deassertion during ak8975_power_on(), driver's probe fails
> on ak8975_who_i_am while() checking for device identity for AK09911 chip.
>
> AK09911 has an active low reset gpio to handle register's reset.
> AK09911 datasheed says that, if not used, reset pin should be connected

Another minor typo: datasheed -> datasheet

In any case, FWIW:
Reviewed-by: Stephan Gerhold <stephan@gerhold.net>

> to VID. This patch emulates this situation.
>
> Signed-off-by: Jonathan Albrieux <jonathan.albrieux@gmail.com>
> ---
> drivers/iio/magnetometer/ak8975.c | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
> diff --git a/drivers/iio/magnetometer/ak8975.c b/drivers/iio/magnetometer/ak8975.c
> index fd368455cd7b..a23422aad97d 100644
> --- a/drivers/iio/magnetometer/ak8975.c
> +++ b/drivers/iio/magnetometer/ak8975.c
> @@ -358,6 +358,7 @@ struct ak8975_data {
> u8 asa[3];
> long raw_to_gauss[3];
> struct gpio_desc *eoc_gpiod;
> + struct gpio_desc *reset_gpiod;
> int eoc_irq;
> wait_queue_head_t data_ready_queue;
> unsigned long flags;
> @@ -384,6 +385,9 @@ static int ak8975_power_on(const struct ak8975_data *data)
> "Failed to enable specified Vid supply\n");
> return ret;
> }
> +
> + gpiod_set_value_cansleep(data->reset_gpiod, 0);
> +
> /*
> * According to the datasheet the power supply rise time is 200us
> * and the minimum wait time before mode setting is 100us, in
> @@ -396,6 +400,8 @@ static int ak8975_power_on(const struct ak8975_data *data)
> /* Disable attached power regulator if any. */
> static void ak8975_power_off(const struct ak8975_data *data)
> {
> + gpiod_set_value_cansleep(data->reset_gpiod, 1);
> +
> regulator_disable(data->vid);
> regulator_disable(data->vdd);
> }
> @@ -839,6 +845,7 @@ static int ak8975_probe(struct i2c_client *client,
> struct ak8975_data *data;
> struct iio_dev *indio_dev;
> struct gpio_desc *eoc_gpiod;
> + struct gpio_desc *reset_gpiod;
> const void *match;
> unsigned int i;
> int err;
> @@ -856,6 +863,16 @@ static int ak8975_probe(struct i2c_client *client,
> if (eoc_gpiod)
> gpiod_set_consumer_name(eoc_gpiod, "ak_8975");
>
> + /*
> + * According to AK09911 datasheet, if reset GPIO is provided then
> + * deassert reset on ak8975_power_on() and assert reset on
> + * ak8975_power_off().
> + */
> + reset_gpiod = devm_gpiod_get_optional(&client->dev,
> + "reset", GPIOD_OUT_HIGH);
> + if (IS_ERR(reset_gpiod))
> + return PTR_ERR(reset_gpiod);
> +
> /* Register with IIO */
> indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
> if (indio_dev == NULL)
> @@ -866,6 +883,7 @@ static int ak8975_probe(struct i2c_client *client,
>
> data->client = client;
> data->eoc_gpiod = eoc_gpiod;
> + data->reset_gpiod = reset_gpiod;
> data->eoc_irq = 0;
>
> err = iio_read_mount_matrix(&client->dev, "mount-matrix", &data->orientation);
> --
> 2.17.1