iio: Add Freescale MPL3115A2 pressure / temperature sensor driver

I2C-controlled MEMS sensor with 20-bit pressure measurement (pascal) and
12-bit temperature measurement

driver only exposes basic functionality, see TODO remarks
datasheet: http://cache.freescale.com/files/sensors/doc/data_sheet/MPL3115A2.pdf

v2:
* store 20-bit value in 32-bit buffer element (instead of 24-bit)
* zero buffer to prevent kernel data leak to userspace
* fix mutex unlock in trigger handler (thanks Andi Shyti)

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Reviewed-by: Andi Shyti <andi@etezian.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/pressure/Kconfig

@@ -5,6 +5,18 @@
 
 menu "Pressure sensors"
 
+config MPL3115
+	tristate "Freescale MPL3115A2 pressure sensor driver"
+	depends on I2C
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
+	help
+	  Say yes here to build support for the Freescale MPL3115A2
+	  pressure sensor / altimeter.
+
+          To compile this driver as a module, choose M here: the module
+          will be called mpl3115.
+
 config IIO_ST_PRESS
 	tristate "STMicroelectronics pressure sensor Driver"
 	depends on (I2C || SPI_MASTER) && SYSFS

drivers/iio/pressure/Makefile

@@ -3,6 +3,7 @@
 #
 
 # When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_MPL3115) += mpl3115.o
 obj-$(CONFIG_IIO_ST_PRESS) += st_pressure.o
 st_pressure-y := st_pressure_core.o
 st_pressure-$(CONFIG_IIO_BUFFER) += st_pressure_buffer.o

drivers/iio/pressure/mpl3115.c

@@ -0,0 +1,329 @@
+/*
+ * mpl3115.c - Support for Freescale MPL3115A2 pressure/temperature sensor
+ *
+ * Copyright (c) 2013 Peter Meerwald <pmeerw@pmeerw.net>
+ *
+ * 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 0x60)
+ *
+ * TODO: FIFO buffer, altimeter mode, oversampling, continuous mode,
+ * interrupts, user offset correction, raw mode
+ */
+
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/triggered_buffer.h>
+#include <linux/delay.h>
+
+#define MPL3115_STATUS 0x00
+#define MPL3115_OUT_PRESS 0x01 /* MSB first, 20 bit */
+#define MPL3115_OUT_TEMP 0x04 /* MSB first, 12 bit */
+#define MPL3115_WHO_AM_I 0x0c
+#define MPL3115_CTRL_REG1 0x26
+
+#define MPL3115_DEVICE_ID 0xc4
+
+#define MPL3115_STATUS_PRESS_RDY BIT(2)
+#define MPL3115_STATUS_TEMP_RDY BIT(1)
+
+#define MPL3115_CTRL_RESET BIT(2) /* software reset */
+#define MPL3115_CTRL_OST BIT(1) /* initiate measurement */
+#define MPL3115_CTRL_ACTIVE BIT(0) /* continuous measurement */
+#define MPL3115_CTRL_OS_258MS (BIT(5) | BIT(4)) /* 64x oversampling */
+
+struct mpl3115_data {
+	struct i2c_client *client;
+	struct mutex lock;
+	u8 ctrl_reg1;
+};
+
+static int mpl3115_request(struct mpl3115_data *data)
+{
+	int ret, tries = 15;
+
+	/* trigger measurement */
+	ret = i2c_smbus_write_byte_data(data->client, MPL3115_CTRL_REG1,
+		data->ctrl_reg1 | MPL3115_CTRL_OST);
+	if (ret < 0)
+		return ret;
+
+	while (tries-- > 0) {
+		ret = i2c_smbus_read_byte_data(data->client, MPL3115_CTRL_REG1);
+		if (ret < 0)
+			return ret;
+		/* wait for data ready, i.e. OST cleared */
+		if (!(ret & MPL3115_CTRL_OST))
+			break;
+		msleep(20);
+	}
+
+	if (tries < 0) {
+		dev_err(&data->client->dev, "data not ready\n");
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int mpl3115_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int *val, int *val2, long mask)
+{
+	struct mpl3115_data *data = iio_priv(indio_dev);
+	s32 tmp = 0;
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		if (iio_buffer_enabled(indio_dev))
+			return -EBUSY;
+
+		switch (chan->type) {
+		case IIO_PRESSURE: /* in 0.25 pascal / LSB */
+			mutex_lock(&data->lock);
+			ret = mpl3115_request(data);
+			if (ret < 0) {
+				mutex_unlock(&data->lock);
+				return ret;
+			}
+			ret = i2c_smbus_read_i2c_block_data(data->client,
+				MPL3115_OUT_PRESS, 3, (u8 *) &tmp);
+			mutex_unlock(&data->lock);
+			if (ret < 0)
+				return ret;
+			*val = sign_extend32(be32_to_cpu(tmp) >> 12, 23);
+			return IIO_VAL_INT;
+		case IIO_TEMP: /* in 0.0625 celsius / LSB */
+			mutex_lock(&data->lock);
+			ret = mpl3115_request(data);
+			if (ret < 0) {
+				mutex_unlock(&data->lock);
+				return ret;
+			}
+			ret = i2c_smbus_read_i2c_block_data(data->client,
+				MPL3115_OUT_TEMP, 2, (u8 *) &tmp);
+			mutex_unlock(&data->lock);
+			if (ret < 0)
+				return ret;
+			*val = sign_extend32(be32_to_cpu(tmp) >> 20, 15);
+			return IIO_VAL_INT;
+		default:
+			return -EINVAL;
+		}
+	case IIO_CHAN_INFO_SCALE:
+		switch (chan->type) {
+		case IIO_PRESSURE:
+			*val = 0;
+			*val2 = 250; /* want kilopascal */
+			return IIO_VAL_INT_PLUS_MICRO;
+		case IIO_TEMP:
+			*val = 0;
+			*val2 = 62500;
+			return IIO_VAL_INT_PLUS_MICRO;
+		default:
+			return -EINVAL;
+		}
+	}
+	return -EINVAL;
+}
+
+static irqreturn_t mpl3115_trigger_handler(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *indio_dev = pf->indio_dev;
+	struct mpl3115_data *data = iio_priv(indio_dev);
+	u8 buffer[16]; /* 32-bit channel + 16-bit channel + padding + ts */
+	int ret, pos = 0;
+
+	mutex_lock(&data->lock);
+	ret = mpl3115_request(data);
+	if (ret < 0) {
+		mutex_unlock(&data->lock);
+		goto done;
+	}
+
+	memset(buffer, 0, sizeof(buffer));
+	if (test_bit(0, indio_dev->active_scan_mask)) {
+		ret = i2c_smbus_read_i2c_block_data(data->client,
+			MPL3115_OUT_PRESS, 3, &buffer[pos]);
+		if (ret < 0) {
+			mutex_unlock(&data->lock);
+			goto done;
+		}
+		pos += 4;
+	}
+
+	if (test_bit(1, indio_dev->active_scan_mask)) {
+		ret = i2c_smbus_read_i2c_block_data(data->client,
+			MPL3115_OUT_TEMP, 2, &buffer[pos]);
+		if (ret < 0) {
+			mutex_unlock(&data->lock);
+			goto done;
+		}
+	}
+	mutex_unlock(&data->lock);
+
+	iio_push_to_buffers_with_timestamp(indio_dev, buffer,
+		iio_get_time_ns());
+
+done:
+	iio_trigger_notify_done(indio_dev->trig);
+	return IRQ_HANDLED;
+}
+
+static const struct iio_chan_spec mpl3115_channels[] = {
+	{
+		.type = IIO_PRESSURE,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+			BIT(IIO_CHAN_INFO_SCALE),
+		.scan_index = 0,
+		.scan_type = {
+			.sign = 's',
+			.realbits = 20,
+			.storagebits = 32,
+			.shift = 12,
+			.endianness = IIO_BE,
+		}
+	},
+	{
+		.type = IIO_TEMP,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+			BIT(IIO_CHAN_INFO_SCALE),
+		.scan_index = 1,
+		.scan_type = {
+			.sign = 's',
+			.realbits = 12,
+			.storagebits = 16,
+			.shift = 4,
+			.endianness = IIO_BE,
+		}
+	},
+	IIO_CHAN_SOFT_TIMESTAMP(2),
+};
+
+static const struct iio_info mpl3115_info = {
+	.read_raw = &mpl3115_read_raw,
+	.driver_module = THIS_MODULE,
+};
+
+static int mpl3115_probe(struct i2c_client *client,
+			 const struct i2c_device_id *id)
+{
+	struct mpl3115_data *data;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	ret = i2c_smbus_read_byte_data(client, MPL3115_WHO_AM_I);
+	if (ret < 0)
+		return ret;
+	if (ret != MPL3115_DEVICE_ID)
+		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 = &mpl3115_info;
+	indio_dev->name = id->name;
+	indio_dev->dev.parent = &client->dev;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = mpl3115_channels;
+	indio_dev->num_channels = ARRAY_SIZE(mpl3115_channels);
+
+	/* software reset, I2C transfer is aborted (fails) */
+	i2c_smbus_write_byte_data(client, MPL3115_CTRL_REG1,
+		MPL3115_CTRL_RESET);
+	msleep(50);
+
+	data->ctrl_reg1 = MPL3115_CTRL_OS_258MS;
+	ret = i2c_smbus_write_byte_data(client, MPL3115_CTRL_REG1,
+		data->ctrl_reg1);
+	if (ret < 0)
+		return ret;
+
+	ret = iio_triggered_buffer_setup(indio_dev, NULL,
+		mpl3115_trigger_handler, NULL);
+	if (ret < 0)
+		return ret;
+
+	ret = iio_device_register(indio_dev);
+	if (ret < 0)
+		goto buffer_cleanup;
+	return 0;
+
+buffer_cleanup:
+	iio_triggered_buffer_cleanup(indio_dev);
+	return ret;
+}
+
+static int mpl3115_standby(struct mpl3115_data *data)
+{
+	return i2c_smbus_write_byte_data(data->client, MPL3115_CTRL_REG1,
+		data->ctrl_reg1 & ~MPL3115_CTRL_ACTIVE);
+}
+
+static int mpl3115_remove(struct i2c_client *client)
+{
+	struct iio_dev *indio_dev = i2c_get_clientdata(client);
+
+	iio_device_unregister(indio_dev);
+	iio_triggered_buffer_cleanup(indio_dev);
+	mpl3115_standby(iio_priv(indio_dev));
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int mpl3115_suspend(struct device *dev)
+{
+	return mpl3115_standby(iio_priv(i2c_get_clientdata(
+		to_i2c_client(dev))));
+}
+
+static int mpl3115_resume(struct device *dev)
+{
+	struct mpl3115_data *data = iio_priv(i2c_get_clientdata(
+		to_i2c_client(dev)));
+
+	return i2c_smbus_write_byte_data(data->client, MPL3115_CTRL_REG1,
+		data->ctrl_reg1);
+}
+
+static SIMPLE_DEV_PM_OPS(mpl3115_pm_ops, mpl3115_suspend, mpl3115_resume);
+#define MPL3115_PM_OPS (&mpl3115_pm_ops)
+#else
+#define MPL3115_PM_OPS NULL
+#endif
+
+static const struct i2c_device_id mpl3115_id[] = {
+	{ "mpl3115", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, mpl3115_id);
+
+static struct i2c_driver mpl3115_driver = {
+	.driver = {
+		.name	= "mpl3115",
+		.pm	= MPL3115_PM_OPS,
+	},
+	.probe = mpl3115_probe,
+	.remove = mpl3115_remove,
+	.id_table = mpl3115_id,
+};
+module_i2c_driver(mpl3115_driver);
+
+MODULE_AUTHOR("Peter Meerwald <pmeerw@pmeerw.net>");
+MODULE_DESCRIPTION("Freescale MPL3115 pressure/temperature driver");
+MODULE_LICENSE("GPL");