iio: accel: Add support for Sensortek STK8BA50

Minimal implementation of an IIO driver for the Sensortek
STK8BA50 3-axis accelerometer. Datasheet:
http://szgsensor.com/uploads/soft/141229/STK8BA50%D2%E5%BC%CE.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

@@ -147,4 +147,14 @@ config STK8312
 	  Choosing M will build the driver as a module. If so, the module
 	  will be called stk8312.
 
+config STK8BA50
+	tristate "Sensortek STK8BA50 3-Axis Accelerometer Driver"
+	depends on I2C
+	help
+	  Say yes here to get support for the Sensortek STK8BA50 3-axis
+	  accelerometer.
+
+	  Choosing M will build the driver as a module. If so, the module
+	  will be called stk8ba50.
+
 endmenu

drivers/iio/accel/Makefile

@@ -15,6 +15,7 @@ obj-$(CONFIG_MMA9551)		+= mma9551.o
 obj-$(CONFIG_MMA9553)		+= mma9553.o
 
 obj-$(CONFIG_STK8312)		+= stk8312.o
+obj-$(CONFIG_STK8BA50)		+= stk8ba50.o
 
 obj-$(CONFIG_IIO_SSP_SENSORS_COMMONS) += ssp_accel_sensor.o
 

drivers/iio/accel/stk8ba50.c

@@ -0,0 +1,302 @@
+/**
+ * Sensortek STK8BA50 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.
+ *
+ * STK8BA50 7-bit I2C address: 0x18.
+ */
+
+#include <linux/acpi.h>
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+#define STK8BA50_REG_XOUT			0x02
+#define STK8BA50_REG_YOUT			0x04
+#define STK8BA50_REG_ZOUT			0x06
+#define STK8BA50_REG_RANGE			0x0F
+#define STK8BA50_REG_POWMODE			0x11
+#define STK8BA50_REG_SWRST			0x14
+
+#define STK8BA50_MODE_NORMAL			0
+#define STK8BA50_MODE_SUSPEND			1
+#define STK8BA50_MODE_POWERBIT			BIT(7)
+#define STK8BA50_DATA_SHIFT			6
+#define STK8BA50_RESET_CMD			0xB6
+
+#define STK8BA50_DRIVER_NAME			"stk8ba50"
+
+#define STK8BA50_SCALE_AVAIL			"0.0384 0.0767 0.1534 0.3069"
+
+/*
+ * The accelerometer has four measurement ranges:
+ * +/-2g; +/-4g; +/-8g; +/-16g
+ *
+ * Acceleration values are 10-bit, 2's complement.
+ * Scales are calculated as following:
+ *
+ * scale1 = (2 + 2) * 9.81 / (2^10 - 1)   = 0.0384
+ * scale2 = (4 + 4) * 9.81 / (2^10 - 1)   = 0.0767
+ * etc.
+ *
+ * Scales are stored in this format:
+ * { <register value>, <scale value> }
+ *
+ * Locally, the range is stored as a table index.
+ */
+static const int stk8ba50_scale_table[][2] = {
+	{3, 38400}, {5, 76700}, {8, 153400}, {12, 306900}
+};
+
+struct stk8ba50_data {
+	struct i2c_client *client;
+	struct mutex lock;
+	int range;
+};
+
+#define STK8BA50_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 stk8ba50_channels[] = {
+	STK8BA50_ACCEL_CHANNEL(STK8BA50_REG_XOUT, X),
+	STK8BA50_ACCEL_CHANNEL(STK8BA50_REG_YOUT, Y),
+	STK8BA50_ACCEL_CHANNEL(STK8BA50_REG_ZOUT, Z),
+};
+
+static IIO_CONST_ATTR(in_accel_scale_available, STK8BA50_SCALE_AVAIL);
+
+static struct attribute *stk8ba50_attributes[] = {
+	&iio_const_attr_in_accel_scale_available.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group stk8ba50_attribute_group = {
+	.attrs = stk8ba50_attributes
+};
+
+static int stk8ba50_read_accel(struct stk8ba50_data *data, u8 reg)
+{
+	int ret;
+	struct i2c_client *client = data->client;
+
+	ret = i2c_smbus_read_word_data(client, reg);
+	if (ret < 0) {
+		dev_err(&client->dev, "register read failed\n");
+		return ret;
+	}
+
+	return sign_extend32(ret >> STK8BA50_DATA_SHIFT, 9);
+}
+
+static int stk8ba50_read_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int *val, int *val2, long mask)
+{
+	struct stk8ba50_data *data = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		mutex_lock(&data->lock);
+		*val = stk8ba50_read_accel(data, chan->address);
+		mutex_unlock(&data->lock);
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = 0;
+		*val2 = stk8ba50_scale_table[data->range][1];
+		return IIO_VAL_INT_PLUS_MICRO;
+	}
+
+	return -EINVAL;
+}
+
+static int stk8ba50_write_raw(struct iio_dev *indio_dev,
+			      struct iio_chan_spec const *chan,
+			      int val, int val2, long mask)
+{
+	int ret;
+	int i;
+	int index = -1;
+	struct stk8ba50_data *data = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_SCALE:
+		if (val != 0)
+			return -EINVAL;
+
+		for (i = 0; i < ARRAY_SIZE(stk8ba50_scale_table); i++)
+			if (val2 == stk8ba50_scale_table[i][1]) {
+				index = i;
+				break;
+			}
+		if (index < 0)
+			return -EINVAL;
+
+		ret = i2c_smbus_write_byte_data(data->client,
+				STK8BA50_REG_RANGE,
+				stk8ba50_scale_table[index][0]);
+		if (ret < 0)
+			dev_err(&data->client->dev,
+					"failed to set measurement range\n");
+		else
+			data->range = index;
+
+		return ret;
+	}
+
+	return -EINVAL;
+}
+
+static const struct iio_info stk8ba50_info = {
+	.driver_module		= THIS_MODULE,
+	.read_raw		= stk8ba50_read_raw,
+	.write_raw		= stk8ba50_write_raw,
+	.attrs			= &stk8ba50_attribute_group,
+};
+
+static int stk8ba50_set_power(struct stk8ba50_data *data, bool mode)
+{
+	int ret;
+	u8 masked_reg;
+	struct i2c_client *client = data->client;
+
+	ret = i2c_smbus_read_byte_data(client, STK8BA50_REG_POWMODE);
+	if (ret < 0)
+		goto exit_err;
+
+	if (mode)
+		masked_reg = ret | STK8BA50_MODE_POWERBIT;
+	else
+		masked_reg = ret & (~STK8BA50_MODE_POWERBIT);
+
+	ret = i2c_smbus_write_byte_data(client, STK8BA50_REG_POWMODE,
+					masked_reg);
+	if (ret < 0)
+		goto exit_err;
+
+	return ret;
+
+exit_err:
+	dev_err(&client->dev, "failed to change sensor mode\n");
+	return ret;
+}
+
+static int stk8ba50_probe(struct i2c_client *client,
+			  const struct i2c_device_id *id)
+{
+	int ret;
+	struct iio_dev *indio_dev;
+	struct stk8ba50_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 = &stk8ba50_info;
+	indio_dev->name = STK8BA50_DRIVER_NAME;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = stk8ba50_channels;
+	indio_dev->num_channels = ARRAY_SIZE(stk8ba50_channels);
+
+	/* Reset all registers on startup */
+	ret = i2c_smbus_write_byte_data(client,
+			STK8BA50_REG_SWRST, STK8BA50_RESET_CMD);
+	if (ret < 0) {
+		dev_err(&client->dev, "failed to reset sensor\n");
+		return ret;
+	}
+
+	/* The default range is +/-2g */
+	data->range = 0;
+
+	ret = iio_device_register(indio_dev);
+	if (ret < 0) {
+		dev_err(&client->dev, "device_register failed\n");
+		stk8ba50_set_power(data, STK8BA50_MODE_SUSPEND);
+	}
+
+	return ret;
+}
+
+static int stk8ba50_remove(struct i2c_client *client)
+{
+	struct iio_dev *indio_dev = i2c_get_clientdata(client);
+
+	iio_device_unregister(indio_dev);
+
+	return stk8ba50_set_power(iio_priv(indio_dev), STK8BA50_MODE_SUSPEND);
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int stk8ba50_suspend(struct device *dev)
+{
+	struct stk8ba50_data *data;
+
+	data = iio_priv(i2c_get_clientdata(to_i2c_client(dev)));
+
+	return stk8ba50_set_power(data, STK8BA50_MODE_SUSPEND);
+}
+
+static int stk8ba50_resume(struct device *dev)
+{
+	struct stk8ba50_data *data;
+
+	data = iio_priv(i2c_get_clientdata(to_i2c_client(dev)));
+
+	return stk8ba50_set_power(data, STK8BA50_MODE_NORMAL);
+}
+
+static SIMPLE_DEV_PM_OPS(stk8ba50_pm_ops, stk8ba50_suspend, stk8ba50_resume);
+
+#define STK8BA50_PM_OPS (&stk8ba50_pm_ops)
+#else
+#define STK8BA50_PM_OPS NULL
+#endif
+
+static const struct i2c_device_id stk8ba50_i2c_id[] = {
+	{"stk8ba50", 0},
+	{}
+};
+
+static const struct acpi_device_id stk8ba50_acpi_id[] = {
+	{"STK8BA50", 0},
+	{}
+};
+
+MODULE_DEVICE_TABLE(acpi, stk8ba50_acpi_id);
+
+static struct i2c_driver stk8ba50_driver = {
+	.driver = {
+		.name = "stk8ba50",
+		.pm = STK8BA50_PM_OPS,
+		.acpi_match_table = ACPI_PTR(stk8ba50_acpi_id),
+	},
+	.probe =            stk8ba50_probe,
+	.remove =           stk8ba50_remove,
+	.id_table =         stk8ba50_i2c_id,
+};
+
+module_i2c_driver(stk8ba50_driver);
+
+MODULE_AUTHOR("Tiberiu Breana <tiberiu.a.breana@intel.com>");
+MODULE_DESCRIPTION("STK8BA50 3-Axis Accelerometer driver");
+MODULE_LICENSE("GPL v2");