Re: [PATCH] iio: Add t5403 barometric pressure sensor driver

[Hartmut Knaack <knaack.h@gmx.de>]

Peter Meerwald schrieb:
> 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
>
> Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
> Cc: Stefan Nilsson <stefan.nilsson@unixphere.com>
> ---
>  drivers/iio/pressure/Kconfig  |  10 ++
>  drivers/iio/pressure/Makefile |   1 +
>  drivers/iio/pressure/t5403.c  | 268 ++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 279 insertions(+)
>  create mode 100644 drivers/iio/pressure/t5403.c
>
> diff --git a/drivers/iio/pressure/Kconfig b/drivers/iio/pressure/Kconfig
> index ffac8ac..15afbc9 100644
> --- a/drivers/iio/pressure/Kconfig
> +++ b/drivers/iio/pressure/Kconfig
> @@ -70,4 +70,14 @@ config IIO_ST_PRESS_SPI
>  	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
> diff --git a/drivers/iio/pressure/Makefile b/drivers/iio/pressure/Makefile
> index c53d250..90a37e8 100644
> --- a/drivers/iio/pressure/Makefile
> +++ b/drivers/iio/pressure/Makefile
> @@ -9,6 +9,7 @@ obj-$(CONFIG_MPL3115) += mpl3115.o
>  obj-$(CONFIG_IIO_ST_PRESS) += st_pressure.o
>  st_pressure-y := st_pressure_core.o
>  st_pressure-$(CONFIG_IIO_BUFFER) += st_pressure_buffer.o
> +obj-$(CONFIG_T5403) += t5403.o
>  
>  obj-$(CONFIG_IIO_ST_PRESS_I2C) += st_pressure_i2c.o
>  obj-$(CONFIG_IIO_ST_PRESS_SPI) += st_pressure_spi.o
> diff --git a/drivers/iio/pressure/t5403.c b/drivers/iio/pressure/t5403.c
> new file mode 100644
> index 0000000..cb01d6d
> --- /dev/null
> +++ b/drivers/iio/pressure/t5403.c
> @@ -0,0 +1,268 @@
> +/*
> + * t5403.c - Support for EPCOS T5403 pressure/temperature sensor
> + *
> + * Copyright (c) 2014 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 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 1
^That needs to be 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);
This is a bit confusing. Although not causing any harm, I would keep sending data->mode unchanged at all time and just set/clear the pt bits as needed.
> +	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 */
What about simplifying those equations, they look to me like this:
S = (c9 * t_r^3)/2^46 + (c5 * t_r^2)/2^34 + (c4 * t_r)/2^17 + c3
O = (c9 * t_r^3)/2^31 + (c8 * t_r^2)/2^19 + (c7 * t_r)/2^3 + c_6 * 2^14
That should barely fit into s64.
> +	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;
> +
Check for the right mask (IIO_CHAN_INFO_INT_TIME).
> +	for (i = 0; i < ARRAY_SIZE(t5403_pressure_conv_ms); i++)
> +		if (val == 0 && val2 == t5403_pressure_conv_ms[i] * 1000) {
> +			mutex_lock(&data->lock);
> +			data->mode = i;
> +			mutex_unlock(&data->lock);
> +			return 0;
> +		}
> +	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 <pmeerw@pmeerw.net>");
> +MODULE_DESCRIPTION("EPCOS T5403 pressure/temperature sensor driver");
> +MODULE_LICENSE("GPL");