Re: [PATCH] iio: accel: Add support for Sensortek STK8312

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On Tue, 5 May 2015, Tiberiu Breana wrote:

> Minimal implementation of an IIO driver for the Sensortek
> STK8312 3-axis accelerometer.
> Datasheet:
> http://www.syi-group.com/uploadpic/data/201361817562681623.pdf

some comments below
 
> Includes:
> - ACPI support;
> - read_raw for x,y,z axes;
> - reading and setting the scale (range) parameter.
> - power management
> 
> Signed-off-by: Tiberiu Breana <tiberiu.a.breana@xxxxxxxxx>
> ---
>  drivers/iio/accel/Kconfig   |  11 ++
>  drivers/iio/accel/Makefile  |   2 +
>  drivers/iio/accel/stk8312.c | 375 ++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 388 insertions(+)
>  create mode 100644 drivers/iio/accel/stk8312.c
> 
> diff --git a/drivers/iio/accel/Kconfig b/drivers/iio/accel/Kconfig
> index 7c9a9a9..8bd8ccb 100644
> --- a/drivers/iio/accel/Kconfig
> +++ b/drivers/iio/accel/Kconfig
> @@ -136,4 +136,15 @@ config MMA9553
>  
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called mma9553.
> +
> +config STK8312
> +	tristate "Sensortek STK8312 3-Axis Accelerometer Driver"
> +	depends on I2C
> +	help
> +	  Say yes here to get support for the Sensortek STK8312 3-axis
> +	  accelerometer.
> +
> +	  Choosing M will build the driver as a module. If so, the module
> +	  will be called stk8312.
> +
>  endmenu
> diff --git a/drivers/iio/accel/Makefile b/drivers/iio/accel/Makefile
> index 99d89e4..8b327c1 100644
> --- a/drivers/iio/accel/Makefile
> +++ b/drivers/iio/accel/Makefile
> @@ -14,6 +14,8 @@ obj-$(CONFIG_MMA9551_CORE)	+= mma9551_core.o
>  obj-$(CONFIG_MMA9551)		+= mma9551.o
>  obj-$(CONFIG_MMA9553)		+= mma9553.o
>  
> +obj-$(CONFIG_STK8312)		+= stk8312.o
> +
>  obj-$(CONFIG_IIO_SSP_SENSORS_COMMONS) += ssp_accel_sensor.o
>  
>  obj-$(CONFIG_IIO_ST_ACCEL_3AXIS) += st_accel.o
> diff --git a/drivers/iio/accel/stk8312.c b/drivers/iio/accel/stk8312.c
> new file mode 100644
> index 0000000..ff27e6b
> --- /dev/null
> +++ b/drivers/iio/accel/stk8312.c
> @@ -0,0 +1,375 @@
> +/**
> + * Sensortek STK8312 3-Axis Accelerometer
> + *
> + * Copyright (c) 2015, Intel Corporation.
> + *
> + * This file is subject to the terms and conditions of version 2 of
> + * the GNU General Public License. See the file COPYING in the main
> + * directory of this archive for more details.
> + *
> + * IIO driver for STK8312; 7-bit I2C address: 0x3D.
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/i2c.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/delay.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +
> +#define STK8312_REG_XOUT		0x00
> +#define STK8312_REG_YOUT		0x01
> +#define STK8312_REG_ZOUT		0x02
> +#define STK8312_REG_MODE		0x07
> +#define STK8312_REG_STH			0x13
> +#define STK8312_REG_RESET		0x20
> +
> +#define STK8312_MODE_ACTIVE		1
> +#define STK8312_MODE_STANDBY		0
> +#define STK8312_MODE_MASK		0x01
> +#define STK8312_RNG_MASK		0xC0
> +#define STK8312_ALERT_MASK		0x40
> +#define STK8312_DATA6_MASK		0x3F
> +#define STK8312_RNG_SHIFT		6
> +#define STK8312_READ_RETRIES		16
> +
> +#define STK8312_DRIVER_NAME		"stk8312"
> +
> +#define STK8312_SCALE_AVAIL		"0.4747 0.4632 1.2354"

the scale values look strange: not monotonic, 0.47 ~= 0.46 ?!

> +
> +static const int stk8312_scale_table[][2] = {
> +	{0, 474700}, {0, 463200}, {1, 235400}
> +};
> +
> +#define STK8312_ACCEL_CHANNEL(axis) {				\
> +	.type = IIO_ACCEL,					\
> +	.modified = 1,						\
> +	.channel2 = IIO_MOD_##axis,				\
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
> +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
> +}
> +
> +static const struct iio_chan_spec stk8312_channels[] = {
> +	STK8312_ACCEL_CHANNEL(X),
> +	STK8312_ACCEL_CHANNEL(Y),
> +	STK8312_ACCEL_CHANNEL(Z),
> +};
> +
> +struct stk8312_data {
> +	struct i2c_client *client;
> +	struct mutex lock;
> +	int range;
> +	u8 mode;
> +};
> +
> +static IIO_CONST_ATTR(in_accel_scale_available, STK8312_SCALE_AVAIL);
> +
> +static struct attribute *stk8312_attributes[] = {
> +	&iio_const_attr_in_accel_scale_available.dev_attr.attr,
> +	NULL,
> +};
> +
> +static const struct attribute_group stk8312_attribute_group = {
> +	.attrs = stk8312_attributes
> +};
> +
> +static int stk8312_set_mode(struct stk8312_data *data, u8 mode)
> +{
> +	int ret;
> +	u8 masked_reg;
> +	struct i2c_client *client = data->client;
> +
> +	if (mode > 1)
> +		return -EINVAL;
> +	else if (mode == data->mode)
> +		return 0;
> +
> +	ret = i2c_smbus_read_byte_data(client, STK8312_REG_MODE);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "register read failed\n");

the message doesn't explain much, maybe mention register name or drop the 
thing

> +		return ret;
> +	}
> +	masked_reg = ret & (~STK8312_MODE_MASK);
> +	masked_reg |= mode;
> +
> +	ret = i2c_smbus_write_byte_data(client, STK8312_REG_MODE,
> +					masked_reg);
> +	if (ret < 0)
> +		dev_err(&client->dev, "failed to change sensor mode\n");
> +	else
> +		data->mode = mode;
> +
> +	return ret;
> +}
> +
> +static int stk8312_set_range(struct stk8312_data *data, u8 range)
> +{
> +	int ret;
> +	int masked_reg;

u8 probably

> +	u8 mode;
> +	struct i2c_client *client = data->client;
> +
> +	if (range < 0 || range > 2)
> +		return -EINVAL;
> +
> +	if (range == data->range)
> +		return 0;
> +
> +	mode = data->mode;
> +	/* We need to go in standby mode to modify registers */
> +	ret = stk8312_set_mode(data, STK8312_MODE_STANDBY);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = i2c_smbus_read_byte_data(client, STK8312_REG_STH);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "register read failed\n");
> +		return ret;
> +	}
> +
> +	masked_reg = ret & (~STK8312_RNG_MASK);
> +	masked_reg |= range << STK8312_RNG_SHIFT;
> +
> +	ret = i2c_smbus_write_byte_data(client, STK8312_REG_STH, masked_reg);
> +	if (ret < 0)
> +		dev_err(&client->dev, "failed to change sensor range\n");
> +	else
> +		data->range = range;
> +
> +	return stk8312_set_mode(data, mode);
> +}
> +
> +static int stk8312_read_accel(struct stk8312_data *data, int axis)
> +{
> +	int ret;
> +	u8 reg;
> +	int retries = STK8312_READ_RETRIES;
> +	struct i2c_client *client = data->client;
> +
> +	switch (axis) {

you could use the iio channel's .address field to store the register to 
read and save this switch

> +	case IIO_MOD_X:
> +		reg = STK8312_REG_XOUT;
> +		break;
> +	case IIO_MOD_Y:
> +		reg = STK8312_REG_YOUT;
> +		break;
> +	case IIO_MOD_Z:
> +		reg = STK8312_REG_ZOUT;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	ret = i2c_smbus_read_byte_data(client, reg);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "register read failed\n");
> +		return ret;
> +	}
> +	if (data->range == 0) {
> +		/* 6bit mode */
> +		while (retries--) {
> +			if (ret & STK8312_ALERT_MASK) {
> +				/* The register is being updated. Try again. */
> +				msleep(20);
> +				ret = i2c_smbus_read_byte_data(client, reg);
> +				if (ret < 0) {
> +					dev_err(&data->client->dev,
> +						"register read failed\n");
> +					return ret;
> +				}
> +			} else {
> +				ret &= STK8312_DATA6_MASK;
> +				return sign_extend32(ret, 5);
> +			}
> +		}
> +		dev_err(&data->client->dev,
> +				"register read failed, data not ready\n");
> +		return -EIO;
> +	}
> +	/* 8bit mode */
> +	return sign_extend32(ret, 7);
> +}
> +
> +static int stk8312_read_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int *val, int *val2, long mask)
> +{
> +	struct stk8312_data *data = iio_priv(indio_dev);
> +
> +	if (chan->type != IIO_ACCEL)
> +		return -EINVAL;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		mutex_lock(&data->lock);
> +		*val = stk8312_read_accel(data, chan->channel2);
> +		mutex_unlock(&data->lock);
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SCALE:
> +		*val = stk8312_scale_table[data->range][0];
> +		*val2 = stk8312_scale_table[data->range][1];
> +		return IIO_VAL_INT_PLUS_MICRO;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static int stk8312_write_raw(struct iio_dev *indio_dev,
> +			     struct iio_chan_spec const *chan,
> +			     int val, int val2, long mask)
> +{
> +	int i;
> +	int index = -1;
> +	int ret;
> +	struct stk8312_data *data = iio_priv(indio_dev);
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_SCALE:
> +		for (i = 0; i < ARRAY_SIZE(stk8312_scale_table); i++)
> +			if (val == stk8312_scale_table[i][0] &&
> +			    val2 == stk8312_scale_table[i][1]) {
> +				index = i;
> +				break;
> +			}
> +		if (index < 0)
> +			return -EINVAL;
> +
> +		mutex_lock(&data->lock);
> +		ret = stk8312_set_range(data, index);
> +		mutex_unlock(&data->lock);
> +
> +		return ret;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static const struct iio_info stk8312_info = {
> +	.driver_module		= THIS_MODULE,
> +	.read_raw		= stk8312_read_raw,
> +	.write_raw		= stk8312_write_raw,
> +	.attrs			= &stk8312_attribute_group,
> +};
> +
> +static int stk8312_init(struct iio_dev *indio_dev)
> +{
> +	int ret;
> +	struct stk8312_data *data = iio_priv(indio_dev);
> +	struct i2c_client *client = data->client;
> +
> +	/* A software reset is recommended at power-on */
> +	ret = i2c_smbus_write_byte_data(data->client, STK8312_REG_RESET, 0x00);
> +	if (ret < 0)
> +		dev_err(&client->dev, "failed to reset sensor");

return ret;

> +
> +	ret = stk8312_set_mode(data, STK8312_MODE_ACTIVE);
> +	if (ret < 0)
> +		dev_err(&client->dev, "failed to enable sensor");
> +
> +	return ret;
> +}
> +
> +static int stk8312_probe(struct i2c_client *client,
> +			 const struct i2c_device_id *id)
> +{
> +	int ret;
> +	struct iio_dev *indio_dev;
> +	struct stk8312_data *data;
> +
> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
> +	if (!indio_dev) {
> +		dev_err(&client->dev, "iio allocation failed!\n");
> +		return -ENOMEM;
> +	}
> +
> +	data = iio_priv(indio_dev);
> +	data->client = client;
> +	i2c_set_clientdata(client, indio_dev);
> +	mutex_init(&data->lock);
> +
> +	indio_dev->dev.parent = &client->dev;
> +	indio_dev->info = &stk8312_info;
> +	indio_dev->name = STK8312_DRIVER_NAME;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = stk8312_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(stk8312_channels);
> +
> +	ret = stk8312_init(indio_dev);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "sensor initialization failed\n");

we already had an error message in _init, not needed here again

> +		return ret;
> +	}
> +
> +	ret = iio_device_register(indio_dev);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "device_register failed\n");
> +		stk8312_set_mode(data, STK8312_MODE_STANDBY);
> +	}
> +
> +	return ret;
> +}
> +
> +static int stk8312_remove(struct i2c_client *client)
> +{
> +	struct iio_dev *indio_dev = i2c_get_clientdata(client);
> +
> +	iio_device_unregister(indio_dev);
> +
> +	return stk8312_set_mode(iio_priv(indio_dev), STK8312_MODE_STANDBY);
> +}
> +
> +#ifdef CONFIG_PM_SLEEP
> +static int stk8312_suspend(struct device *dev)
> +{
> +	struct stk8312_data *data;
> +
> +	data = iio_priv(i2c_get_clientdata(to_i2c_client(dev)));
> +
> +	return stk8312_set_mode(data, STK8312_MODE_STANDBY);
> +}
> +
> +static int stk8312_resume(struct device *dev)
> +{
> +	struct stk8312_data *data;
> +
> +	data = iio_priv(i2c_get_clientdata(to_i2c_client(dev)));
> +
> +	return stk8312_set_mode(data, STK8312_MODE_ACTIVE);
> +}
> +
> +static SIMPLE_DEV_PM_OPS(stk8312_pm_ops, stk8312_suspend, stk8312_resume);
> +
> +#define STK8312_PM_OPS (&stk8312_pm_ops)
> +#else
> +#define STK8312_PM_OPS NULL
> +#endif
> +
> +static const struct i2c_device_id stk8312_i2c_id[] = {
> +	{"STK8312", 0},
> +	{}
> +};
> +
> +static const struct acpi_device_id stk8312_acpi_id[] = {
> +	{"STK8312", 0},
> +	{}
> +};
> +
> +MODULE_DEVICE_TABLE(acpi, stk8312_acpi_id);
> +
> +static struct i2c_driver stk8312_driver = {
> +	.driver = {
> +		.name = "stk8312",
> +		.pm = STK8312_PM_OPS,
> +		.acpi_match_table = ACPI_PTR(stk8312_acpi_id),
> +	},
> +	.probe =            stk8312_probe,
> +	.remove =           stk8312_remove,
> +	.id_table =         stk8312_i2c_id,
> +};
> +
> +module_i2c_driver(stk8312_driver);
> +
> +MODULE_AUTHOR("Tiberiu Breana <tiberiu.a.breana@xxxxxxxxx>");
> +MODULE_DESCRIPTION("STK8312 3-Axis Accelerometer driver");
> +MODULE_LICENSE("GPL v2");
> 

-- 

Peter Meerwald
+43-664-2444418 (mobile)
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