>>Ah. I missed there was a v2 and replied to v1.
No problem Jon and thanks for the suggestion. A delay of 5ms
was not worth it when calculation itself takes only ~3ms.
I have implemented runtime PM keeping a delay of 200 ms
which I think should suffice. Have sent you v3.
-----Original Message-----
From: Jonathan Cameron <jic23@xxxxxxxxxx>
Sent: Sunday, October 2, 2022 6:52 PM
To: Khandelwal, Rajat <rajat.khandelwal@xxxxxxxxx>
Cc: lars@xxxxxxxxxx; linux-iio@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
Subject: Re: [PATCH v2] iio: pressure: mpl115: Implementing low power mode by shutdown gpio
On Tue, 27 Sep 2022 23:12:12 +0530
Rajat Khandelwal <rajat.khandelwal@xxxxxxxxx> wrote:
> MPL115 supports shutdown gpio which can be used to set the default
> state to low power mode. Power from all internal circuits and
> registers is removed. This is done by pulling the SHDN pin to low.
> This patch sets the default mode to low-power and only exits when a
> reading is required from the chip. This maximises power savings.
>
> According to spec., a wakeup time period of ~5 ms exists between
> waking up and actually communicating with the device. This is
> implemented using sleep delay.
>
> Signed-off-by: Rajat Khandelwal <rajat.khandelwal@xxxxxxxxx>
Ah. I missed there was a v2 and replied to v1.
> ---
>
> v2: Grammatically completing subject line
>
> drivers/iio/pressure/mpl115.c | 33 +++++++++++++++++++++++++++++----
> 1 file changed, 29 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/iio/pressure/mpl115.c
> b/drivers/iio/pressure/mpl115.c index 5bf5b9abe6f1..c0ad3e941d05
> 100644
> --- a/drivers/iio/pressure/mpl115.c
> +++ b/drivers/iio/pressure/mpl115.c
> @@ -3,13 +3,12 @@
> * mpl115.c - Support for Freescale MPL115A pressure/temperature sensor
> *
> * Copyright (c) 2014 Peter Meerwald <pmeerw@xxxxxxxxxx>
> - *
> - * TODO: shutdown pin
> */
>
> #include <linux/module.h>
> #include <linux/iio/iio.h>
> #include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
>
> #include "mpl115.h"
>
> @@ -27,6 +26,7 @@ struct mpl115_data {
> s16 a0;
> s16 b1, b2;
> s16 c12;
> + struct gpio_desc *shutdown;
> const struct mpl115_ops *ops;
> };
>
> @@ -102,13 +102,27 @@ static int mpl115_read_raw(struct iio_dev
> *indio_dev,
>
> switch (mask) {
> case IIO_CHAN_INFO_PROCESSED:
> - ret = mpl115_comp_pressure(data, val, val2);
> + if (data->shutdown) {
> + gpiod_set_value(data->shutdown, 0);
> + usleep_range(5000, 6000);
> + ret = mpl115_comp_pressure(data, val, val2);
> + gpiod_set_value(data->shutdown, 1);
> + } else
> + ret = mpl115_comp_pressure(data, val, val2);
> +
> if (ret < 0)
> return ret;
> return IIO_VAL_INT_PLUS_MICRO;
> case IIO_CHAN_INFO_RAW:
> /* temperature -5.35 C / LSB, 472 LSB is 25 C */
> - ret = mpl115_read_temp(data);
> + if (data->shutdown) {
> + gpiod_set_value(data->shutdown, 0);
> + usleep_range(5000, 6000);
> + ret = mpl115_read_temp(data);
> + gpiod_set_value(data->shutdown, 1);
> + } else
> + ret = mpl115_read_temp(data);
> +
> if (ret < 0)
> return ret;
> *val = ret >> 6;
> @@ -185,6 +199,17 @@ int mpl115_probe(struct device *dev, const char *name,
> return ret;
> data->c12 = ret;
>
> + data->shutdown = devm_gpiod_get_optional(dev, "shutdown",
> + GPIOD_OUT_HIGH);
> + if (IS_ERR(data->shutdown))
> + return dev_err_probe(dev, PTR_ERR(data->shutdown),
> + "cannot get shutdown gpio\n");
> +
> + if (data->shutdown)
> + dev_dbg(dev, "low-power mode enabled");
> + else
> + dev_dbg(dev, "low-power mode disabled");
> +
> return devm_iio_device_register(dev, indio_dev); }
> EXPORT_SYMBOL_NS_GPL(mpl115_probe, IIO_MPL115);
