iio: pressure: mpl115: Implementing low power mode by shutdown gpio

MPL115 supports shutdown gpio which can be used to set the 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 enables runtime PM on MPL115 to increase 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@linux.intel.com>
Link: https://lore.kernel.org/r/20221010173720.568916-1-rajat.khandelwal@linux.intel.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/pressure/mpl115.c b/drivers/iio/pressure/mpl115.c
index 5bf5b9abe6f1a4e6161da0978fdf92ebf545ee96..02ea38c8a3e4312264ca3078d3c31b3c94158c96 100644 (file)
--- a/drivers/iio/pressure/mpl115.c
+++ b/drivers/iio/pressure/mpl115.c
@@ -4,12 +4,13 @@
  *
  * Copyright (c) 2014 Peter Meerwald <pmeerw@pmeerw.net>
  *
- * TODO: shutdown pin
+ * TODO: synchronization with system suspend
  */
 
 #include <linux/module.h>
 #include <linux/iio/iio.h>
 #include <linux/delay.h>
+#include <linux/gpio/consumer.h>
 
 #include "mpl115.h"
 
@@ -27,6 +28,7 @@ struct mpl115_data {
        s16 a0;
        s16 b1, b2;
        s16 c12;
+       struct gpio_desc *shutdown;
        const struct mpl115_ops *ops;
 };
 
@@ -102,16 +104,24 @@ static int mpl115_read_raw(struct iio_dev *indio_dev,
 
        switch (mask) {
        case IIO_CHAN_INFO_PROCESSED:
+               pm_runtime_get_sync(data->dev);
                ret = mpl115_comp_pressure(data, val, val2);
                if (ret < 0)
                        return ret;
+               pm_runtime_mark_last_busy(data->dev);
+               pm_runtime_put_autosuspend(data->dev);
+
                return IIO_VAL_INT_PLUS_MICRO;
        case IIO_CHAN_INFO_RAW:
+               pm_runtime_get_sync(data->dev);
                /* temperature -5.35 C / LSB, 472 LSB is 25 C */
                ret = mpl115_read_temp(data);
                if (ret < 0)
                        return ret;
+               pm_runtime_mark_last_busy(data->dev);
+               pm_runtime_put_autosuspend(data->dev);
                *val = ret >> 6;
+
                return IIO_VAL_INT;
        case IIO_CHAN_INFO_OFFSET:
                *val = -605;
@@ -168,6 +178,8 @@ int mpl115_probe(struct device *dev, const char *name,
        if (ret)
                return ret;
 
+       dev_set_drvdata(dev, indio_dev);
+
        ret = data->ops->read(data->dev, MPL115_A0);
        if (ret < 0)
                return ret;
@@ -185,10 +197,58 @@ int mpl115_probe(struct device *dev, const char *name,
                return ret;
        data->c12 = ret;
 
+       data->shutdown = devm_gpiod_get_optional(dev, "shutdown",
+                                                GPIOD_OUT_LOW);
+       if (IS_ERR(data->shutdown))
+               return dev_err_probe(dev, PTR_ERR(data->shutdown),
+                                    "cannot get shutdown gpio\n");
+
+       if (data->shutdown) {
+               /* Enable runtime PM */
+               pm_runtime_get_noresume(dev);
+               pm_runtime_set_active(dev);
+               pm_runtime_enable(dev);
+
+               /*
+                * As the device takes 3 ms to come up with a fresh
+                * reading after power-on and 5 ms to actually power-on,
+                * do not shut it down unnecessarily. Set autosuspend to
+                * 2000 ms.
+                */
+               pm_runtime_set_autosuspend_delay(dev, 2000);
+               pm_runtime_use_autosuspend(dev);
+               pm_runtime_put(dev);
+
+               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);
 
+static int mpl115_runtime_suspend(struct device *dev)
+{
+       struct mpl115_data *data = iio_priv(dev_get_drvdata(dev));
+
+       gpiod_set_value(data->shutdown, 1);
+
+       return 0;
+}
+
+static int mpl115_runtime_resume(struct device *dev)
+{
+       struct mpl115_data *data = iio_priv(dev_get_drvdata(dev));
+
+       gpiod_set_value(data->shutdown, 0);
+       usleep_range(5000, 6000);
+
+       return 0;
+}
+
+EXPORT_NS_RUNTIME_DEV_PM_OPS(mpl115_dev_pm_ops, mpl115_runtime_suspend,
+                         mpl115_runtime_resume, NULL, IIO_MPL115);
+
 MODULE_AUTHOR("Peter Meerwald <pmeerw@pmeerw.net>");
 MODULE_DESCRIPTION("Freescale MPL115 pressure/temperature driver");
 MODULE_LICENSE("GPL");

diff --git a/drivers/iio/pressure/mpl115.h b/drivers/iio/pressure/mpl115.h
index 57d55eb8e661789f675b2993893774e7995af34a..78a0068a17bbcf415cd9c881c60524b5dfec2269 100644 (file)
--- a/drivers/iio/pressure/mpl115.h
+++ b/drivers/iio/pressure/mpl115.h
@@ -6,6 +6,8 @@
  * Copyright (c) 2016 Akinobu Mita <akinobu.mita@gmail.com>
  */
 
+#include <linux/pm_runtime.h>
+
 #ifndef _MPL115_H_
 #define _MPL115_H_
 
@@ -18,4 +20,7 @@ struct mpl115_ops {
 int mpl115_probe(struct device *dev, const char *name,
                        const struct mpl115_ops *ops);
 
+/*PM ops */
+extern const struct dev_pm_ops mpl115_dev_pm_ops;
+
 #endif

diff --git a/drivers/iio/pressure/mpl115_i2c.c b/drivers/iio/pressure/mpl115_i2c.c
index 099ab1c6832c5d2b0a4039d7ee720925b497ac33..555bda1146fb95b11ea38114237939e80d793b55 100644 (file)
--- a/drivers/iio/pressure/mpl115_i2c.c
+++ b/drivers/iio/pressure/mpl115_i2c.c
@@ -53,6 +53,7 @@ MODULE_DEVICE_TABLE(i2c, mpl115_i2c_id);
 static struct i2c_driver mpl115_i2c_driver = {
        .driver = {
                .name   = "mpl115",
+               .pm = pm_ptr(&mpl115_dev_pm_ops),
        },
        .probe = mpl115_i2c_probe,
        .id_table = mpl115_i2c_id,

diff --git a/drivers/iio/pressure/mpl115_spi.c b/drivers/iio/pressure/mpl115_spi.c
index 7feec87e2704ef590000be5c24061f8113d46311..58d218fd90dcb9666a530b9011ad7394983f7d19 100644 (file)
--- a/drivers/iio/pressure/mpl115_spi.c
+++ b/drivers/iio/pressure/mpl115_spi.c
@@ -92,6 +92,7 @@ MODULE_DEVICE_TABLE(spi, mpl115_spi_ids);
 static struct spi_driver mpl115_spi_driver = {
        .driver = {
                .name   = "mpl115",
+               .pm = pm_ptr(&mpl115_dev_pm_ops),
        },
        .probe = mpl115_spi_probe,
        .id_table = mpl115_spi_ids,