iio: Add t5403 barometric pressure sensor driver

16-bit pressure and temperature sensor

the chip can do I2C and SPI, only the I2C interface is supported
by the driver at the moment

datasheet: http://www.epcos.com/inf/57/ds/T5400.pdf
application note: http://www.epcos.com/blob/993154/download/1/t5403-applicationnote.pdf

an out-of-tree driver targetting the input subsystem is at
https://github.com/unixphere/t5400, it was rejected here:
http://comments.gmane.org/gmane.linux.kernel.input/28107

v2: (thanks Hartmut Knaack)
* fix MODE_HIGH, equals 2
* check INT_TIME mask in write_raw()

Signed-off-by: Peter Meerwald <[e-mail]>
Cc: Stefan Nilsson <[e-mail]>
Reviewed-by: Hartmut Knaack <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/pressure/Kconfig

···
 	depends on IIO_ST_PRESS
 	depends on IIO_ST_SENSORS_SPI
 
+config T5403
+	tristate "EPCOS T5403 digital barometric pressure sensor driver"
+	depends on I2C
+	help
+	  Say yes here to build support for the EPCOS T5403 pressure sensor
+	  connected via I2C.
+
+          To compile this driver as a module, choose M here: the module
+          will be called t5403.
+
 endmenu

drivers/iio/pressure/Makefile

···
 obj-$(CONFIG_IIO_ST_PRESS) += st_pressure.o
 st_pressure-y := st_pressure_core.o
 st_pressure-$(CONFIG_IIO_BUFFER) += st_pressure_buffer.o
+obj-$(CONFIG_T5403) += t5403.o
 
 obj-$(CONFIG_IIO_ST_PRESS_I2C) += st_pressure_i2c.o
 obj-$(CONFIG_IIO_ST_PRESS_SPI) += st_pressure_spi.o

drivers/iio/pressure/t5403.c

···
+/*
+ * t5403.c - Support for EPCOS T5403 pressure/temperature sensor
+ *
+ * Copyright (c) 2014 Peter Meerwald <[e-mail]>
+ *
+ * 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.
+ *
+ * (7-bit I2C slave address 0x77)
+ *
+ * TODO: end-of-conversion irq
+ */
+
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/delay.h>
+
+#define T5403_DATA 0xf5 /* data, LSB first, 16 bit */
+#define T5403_CALIB_DATA 0x8e /* 10 calibration coeff., LSB first, 16 bit */
+#define T5403_SLAVE_ADDR 0x88 /* I2C slave address, 0x77 */
+#define T5403_COMMAND 0xf1
+
+/* command bits */
+#define T5403_MODE_SHIFT 3 /* conversion time: 2, 8, 16, 66 ms */
+#define T5403_PT BIT(1) /* 0 .. pressure, 1 .. temperature measurement */
+#define T5403_SCO BIT(0) /* start conversion */
+
+#define T5403_MODE_LOW 0
+#define T5403_MODE_STANDARD 1
+#define T5403_MODE_HIGH 2
+#define T5403_MODE_ULTRA_HIGH 3
+
+#define T5403_I2C_MASK (~BIT(7))
+#define T5403_I2C_ADDR 0x77
+
+static const int t5403_pressure_conv_ms[] = {2, 8, 16, 66};
+
+struct t5403_data {
+	struct i2c_client *client;
+	struct mutex lock;
+	int mode;
+	__le16 c[10];
+};
+
+#define T5403_C_U16(i) le16_to_cpu(data->c[(i) - 1])
+#define T5403_C(i) sign_extend32(T5403_C_U16(i), 15)
+
+static int t5403_read(struct t5403_data *data, bool pressure)
+{
+	int wait_time = 3;  /* wakeup time in ms */
+
+	int ret = i2c_smbus_write_byte_data(data->client, T5403_COMMAND,
+		(pressure ? (data->mode << T5403_MODE_SHIFT) : T5403_PT) |
+		T5403_SCO);
+	if (ret < 0)
+		return ret;
+
+	wait_time += pressure ? t5403_pressure_conv_ms[data->mode] : 2;
+
+	msleep(wait_time);
+
+	return i2c_smbus_read_word_data(data->client, T5403_DATA);
+}
+
+static int t5403_comp_pressure(struct t5403_data *data, int *val, int *val2)
+{
+	int ret;
+	s16 t_r;
+	u16 p_r;
+	s32 S, O, X;
+
+	mutex_lock(&data->lock);
+
+	ret = t5403_read(data, false);
+	if (ret < 0)
+		goto done;
+	t_r = ret;
+
+	ret = t5403_read(data, true);
+	if (ret < 0)
+		goto done;
+	p_r = ret;
+
+	/* see EPCOS application note */
+	S = T5403_C_U16(3) + (s32) T5403_C_U16(4) * t_r / 0x20000 +
+		T5403_C(5) * t_r / 0x8000 * t_r / 0x80000 +
+		T5403_C(9) * t_r / 0x8000 * t_r / 0x8000 * t_r / 0x10000;
+
+	O = T5403_C(6) * 0x4000 + T5403_C(7) * t_r / 8 +
+		T5403_C(8) * t_r / 0x8000 * t_r / 16 +
+		T5403_C(9) * t_r / 0x8000 * t_r / 0x10000 * t_r;
+
+	X = (S * p_r + O) / 0x4000;
+
+	X += ((X - 75000) * (X - 75000) / 0x10000 - 9537) *
+	    T5403_C(10) / 0x10000;
+
+	*val = X / 1000;
+	*val2 = (X % 1000) * 1000;
+
+done:
+	mutex_unlock(&data->lock);
+	return ret;
+}
+
+static int t5403_comp_temp(struct t5403_data *data, int *val)
+{
+	int ret;
+	s16 t_r;
+
+	mutex_lock(&data->lock);
+	ret = t5403_read(data, false);
+	if (ret < 0)
+		goto done;
+	t_r = ret;
+
+	/* see EPCOS application note */
+	*val = ((s32) T5403_C_U16(1) * t_r / 0x100 +
+		(s32) T5403_C_U16(2) * 0x40) * 1000 / 0x10000;
+
+done:
+	mutex_unlock(&data->lock);
+	return ret;
+}
+
+static int t5403_read_raw(struct iio_dev *indio_dev,
+			  struct iio_chan_spec const *chan,
+			  int *val, int *val2, long mask)
+{
+	struct t5403_data *data = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_PROCESSED:
+		switch (chan->type) {
+		case IIO_PRESSURE:
+			ret = t5403_comp_pressure(data, val, val2);
+			if (ret < 0)
+				return ret;
+			return IIO_VAL_INT_PLUS_MICRO;
+		case IIO_TEMP:
+			ret = t5403_comp_temp(data, val);
+			if (ret < 0)
+				return ret;
+			return IIO_VAL_INT;
+		default:
+			return -EINVAL;
+	    }
+	case IIO_CHAN_INFO_INT_TIME:
+		*val = 0;
+		*val2 = t5403_pressure_conv_ms[data->mode] * 1000;
+		return IIO_VAL_INT_PLUS_MICRO;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int t5403_write_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *chan,
+			   int val, int val2, long mask)
+{
+	struct t5403_data *data = iio_priv(indio_dev);
+	int i;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_INT_TIME:
+		if (val != 0)
+			return -EINVAL;
+		for (i = 0; i < ARRAY_SIZE(t5403_pressure_conv_ms); i++)
+			if (val2 == t5403_pressure_conv_ms[i] * 1000) {
+				mutex_lock(&data->lock);
+				data->mode = i;
+				mutex_unlock(&data->lock);
+				return 0;
+			}
+		return -EINVAL;
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_chan_spec t5403_channels[] = {
+	{
+		.type = IIO_PRESSURE,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED) |
+		    BIT(IIO_CHAN_INFO_INT_TIME),
+	},
+	{
+		.type = IIO_TEMP,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
+	},
+};
+
+static IIO_CONST_ATTR_INT_TIME_AVAIL("0.002 0.008 0.016 0.066");
+
+static struct attribute *t5403_attributes[] = {
+	&iio_const_attr_integration_time_available.dev_attr.attr,
+	NULL
+};
+
+static const struct attribute_group t5403_attribute_group = {
+	.attrs = t5403_attributes,
+};
+
+static const struct iio_info t5403_info = {
+	.read_raw = &t5403_read_raw,
+	.write_raw = &t5403_write_raw,
+	.attrs = &t5403_attribute_group,
+	.driver_module = THIS_MODULE,
+};
+
+static int t5403_probe(struct i2c_client *client,
+			 const struct i2c_device_id *id)
+{
+	struct t5403_data *data;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA |
+	    I2C_FUNC_SMBUS_I2C_BLOCK))
+		return -ENODEV;
+
+	ret = i2c_smbus_read_byte_data(client, T5403_SLAVE_ADDR);
+	if (ret < 0)
+		return ret;
+	if ((ret & T5403_I2C_MASK) != T5403_I2C_ADDR)
+		return -ENODEV;
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	data = iio_priv(indio_dev);
+	data->client = client;
+	mutex_init(&data->lock);
+
+	i2c_set_clientdata(client, indio_dev);
+	indio_dev->info = &t5403_info;
+	indio_dev->name = id->name;
+	indio_dev->dev.parent = &client->dev;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = t5403_channels;
+	indio_dev->num_channels = ARRAY_SIZE(t5403_channels);
+
+	data->mode = T5403_MODE_STANDARD;
+
+	ret = i2c_smbus_read_i2c_block_data(data->client, T5403_CALIB_DATA,
+	    sizeof(data->c), (u8 *) data->c);
+	if (ret < 0)
+		return ret;
+
+	return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static const struct i2c_device_id t5403_id[] = {
+	{ "t5403", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, t5403_id);
+
+static struct i2c_driver t5403_driver = {
+	.driver = {
+		.name	= "t5403",
+	},
+	.probe = t5403_probe,
+	.id_table = t5403_id,
+};
+module_i2c_driver(t5403_driver);
+
+MODULE_AUTHOR("Peter Meerwald <[e-mail]>");
+MODULE_DESCRIPTION("EPCOS T5403 pressure/temperature sensor driver");
+MODULE_LICENSE("GPL");