iio: accel: Add support for Sensortek STK8312

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

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@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

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

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

drivers/iio/accel/stk8312.c

+/**
+ * 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_REG_AFECTRL		0x24
+#define STK8312_REG_OTPADDR		0x3D
+#define STK8312_REG_OTPDATA		0x3E
+#define STK8312_REG_OTPCTRL		0x3F
+
+#define STK8312_MODE_ACTIVE		1
+#define STK8312_MODE_STANDBY		0
+#define STK8312_MODE_MASK		0x01
+#define STK8312_RNG_MASK		0xC0
+#define STK8312_RNG_SHIFT		6
+#define STK8312_READ_RETRIES		16
+
+#define STK8312_DRIVER_NAME		"stk8312"
+
+/*
+ * The accelerometer has two measurement ranges:
+ *
+ * -6g - +6g (8-bit, signed)
+ * -16g - +16g (8-bit, signed)
+ *
+ * scale1 = (6 + 6) * 9.81 / (2^8 - 1)     = 0.4616
+ * scale2 = (16 + 16) * 9.81 / (2^8 - 1)   = 1.2311
+ */
+#define STK8312_SCALE_AVAIL		"0.4616 1.2311"
+
+static const int stk8312_scale_table[][2] = {
+	{0, 461600}, {1, 231100}
+};
+
+#define STK8312_ACCEL_CHANNEL(reg, axis) {			\
+	.type = IIO_ACCEL,					\
+	.address = reg,						\
+	.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(STK8312_REG_XOUT, X),
+	STK8312_ACCEL_CHANNEL(STK8312_REG_YOUT, Y),
+	STK8312_ACCEL_CHANNEL(STK8312_REG_ZOUT, 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_otp_init(struct stk8312_data *data)
+{
+	int ret;
+	int count = 10;
+	struct i2c_client *client = data->client;
+
+	ret = i2c_smbus_write_byte_data(client, STK8312_REG_OTPADDR, 0x70);
+	if (ret < 0)
+		goto exit_err;
+	ret = i2c_smbus_write_byte_data(client, STK8312_REG_OTPCTRL, 0x02);
+	if (ret < 0)
+		goto exit_err;
+
+	do {
+		usleep_range(1000, 5000);
+		ret = i2c_smbus_read_byte_data(client, STK8312_REG_OTPCTRL);
+		if (ret < 0)
+			goto exit_err;
+		count--;
+	} while (!(ret & 0x80) && count > 0);
+
+	if (count == 0)
+		goto exit_err;
+
+	ret = i2c_smbus_read_byte_data(client, STK8312_REG_OTPDATA);
+	if (ret < 0)
+		goto exit_err;
+
+	ret = i2c_smbus_write_byte_data(data->client,
+			STK8312_REG_AFECTRL, ret);
+	if (ret < 0)
+		goto exit_err;
+	msleep(150);
+
+	return ret;
+
+exit_err:
+	dev_err(&client->dev, "failed to initialize sensor\n");
+	return ret;
+}
+
+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, "failed to change sensor mode\n");
+		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");
+		return ret;
+	}
+
+	data->mode = mode;
+	if (mode == STK8312_MODE_ACTIVE) {
+		/* Need to run OTP sequence before entering active mode */
+		usleep_range(1000, 5000);
+		ret = stk8312_otp_init(data);
+	}
+
+	return ret;
+}
+
+static int stk8312_set_range(struct stk8312_data *data, u8 range)
+{
+	int ret;
+	u8 masked_reg;
+	u8 mode;
+	struct i2c_client *client = data->client;
+
+	if (range != 1 && range != 2)
+		return -EINVAL;
+	else 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, "failed to change sensor range\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, u8 address)
+{
+	int ret;
+	struct i2c_client *client = data->client;
+
+	if (address > 2)
+		return -EINVAL;
+
+	ret = i2c_smbus_read_byte_data(client, address);
+	if (ret < 0) {
+		dev_err(&client->dev, "register read failed\n");
+		return ret;
+	}
+
+	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->address);
+		mutex_unlock(&data->lock);
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = stk8312_scale_table[data->range - 1][0];
+		*val2 = stk8312_scale_table[data->range - 1][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 + 1;
+				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_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);
+
+	/* 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\n");
+		return ret;
+	}
+	ret = stk8312_set_range(data, 1);
+	if (ret < 0)
+		return ret;
+
+	ret = stk8312_set_mode(data, STK8312_MODE_ACTIVE);
+	if (ret < 0)
+		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@intel.com>");
+MODULE_DESCRIPTION("STK8312 3-Axis Accelerometer driver");
+MODULE_LICENSE("GPL v2");