Re: [PATCH] iio: Add driver for Infineon DPS310

[Jonathan Cameron]

On 04/05/17 08:19, Joel Stanley wrote:
> The DPS310 is a temperature and pressure sensor. It can be accessed over
> i2c and SPI.
> 
> This driver supports polled measurement of temperature over i2c only.
> 
> Signed-off-by: Joel Stanley <joel@xxxxxxxxx>
Few bits inline, but looks pretty good for a v1.
> ---
>  drivers/iio/pressure/Kconfig  |  11 ++
>  drivers/iio/pressure/Makefile |   1 +
>  drivers/iio/pressure/dps310.c | 401 ++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 413 insertions(+)
>  create mode 100644 drivers/iio/pressure/dps310.c
> 
> diff --git a/drivers/iio/pressure/Kconfig b/drivers/iio/pressure/Kconfig
> index bd8d96b96771..50caefc0cd7d 100644
> --- a/drivers/iio/pressure/Kconfig
> +++ b/drivers/iio/pressure/Kconfig
> @@ -42,6 +42,17 @@ config BMP280_SPI
>  	depends on SPI_MASTER
>  	select REGMAP
>  
> +config DPS310
> +       tristate "Infineon DPS310 pressure and temperature sensor"
> +       depends on I2C
> +       select REGMAP_I2C
> +       help
> +	 Support for the Infineon DPS310 digital barometric pressure sensor.
> +	 This driver measures temperature only.
> +
> +	 This driver can also be built as a module.  If so, the module will be
> +	 called dps310.
> +
>  config HID_SENSOR_PRESS
>  	depends on HID_SENSOR_HUB
>  	select IIO_BUFFER
> diff --git a/drivers/iio/pressure/Makefile b/drivers/iio/pressure/Makefile
> index de3dbc81dc5a..997bbaebfa34 100644
> --- a/drivers/iio/pressure/Makefile
> +++ b/drivers/iio/pressure/Makefile
> @@ -8,6 +8,7 @@ obj-$(CONFIG_BMP280) += bmp280.o
>  bmp280-objs := bmp280-core.o bmp280-regmap.o
>  obj-$(CONFIG_BMP280_I2C) += bmp280-i2c.o
>  obj-$(CONFIG_BMP280_SPI) += bmp280-spi.o
> +obj-$(CONFIG_DPS310) += dps310.o
>  obj-$(CONFIG_HID_SENSOR_PRESS)   += hid-sensor-press.o
>  obj-$(CONFIG_HP03) += hp03.o
>  obj-$(CONFIG_MPL115) += mpl115.o
> diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
> new file mode 100644
> index 000000000000..5e8f91a5662b
> --- /dev/null
> +++ b/drivers/iio/pressure/dps310.c
> @@ -0,0 +1,401 @@
> +/*
> + * Copyright 2017 IBM Corporation
> + *
> + * Joel Stanley <joel@xxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version
> + * 2 of the License, or (at your option) any later version.
> + *
> + * The DPS310 is a barometric pressure and temperature sensor.
> + * Currently only reading a single temperature is supported by
> + * this driver.
> + *
> + * TODO:
> + *  - Pressure sensor readings
> + *  - Optionally support the FIFO
> + */
> +
> +#include <linux/module.h>
> +#include <linux/i2c.h>
> +#include <linux/regmap.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
Slight preference for alphabetical order though grouping the iio
ones at the end is fine.
> +
General preference in IIO is to prefix
all defines with something driver appropriate.

DPS310_PRS_BASE etc 

Avoids potential mess down the line with defines
in headers. Lots of these are very generic so
that's not implausible.
> +#define PRS_BASE	0x00
> +#define TMP_BASE	0x03
> +#define PRS_CFG		0x06
> +#define TMP_CFG		0x07
> +#define  TMP_RATE_BITS	GENMASK(6, 4)
> +#define  TMP_PRC_BITS	GENMASK(3, 0)
> +#define  TMP_EXT	BIT(7)
> +#define MEAS_CFG	0x08
> +#define  MEAS_CTRL_BITS	GENMASK(2, 0)
> +#define   PRESSURE_EN	BIT(0)
> +#define   TEMP_EN	BIT(1)
> +#define   BACKGROUND	BIT(2)
> +#define  PRS_RDY	BIT(4)
> +#define  TMP_RDY	BIT(5)
> +#define  SENSOR_RDY	BIT(6)
> +#define  COEF_RDY	BIT(7)
> +#define CFG_REG		0x09
> +#define  INT_HL		BIT(7)
> +#define  TMP_SHIFT_EN	BIT(3)
> +#define  PRS_SHIFT_EN	BIT(4)
> +#define  FIFO_EN	BIT(5)
> +#define  SPI_EN		BIT(6)
> +#define RESET		0x0c
> +#define  RESET_MAGIC	(BIT(0) | BIT(3))
> +#define COEF_BASE	0x10
> +
> +#define TMP_RATE(_n)	ilog2(_n)
You define these but then have it long hand in the code?
> +#define TMP_PRC(_n)	ilog2(_n)
> +
> +#define MCELSIUS_PER_CELSIUS	1000
> +
> +const int scale_factor[] = {
> +	 524288,
> +	1572864,
> +	3670016,
> +	7864320,
> +	 253952,
> +	 516096,
> +	1040384,
> +	2088960,
> +};
> +
> +struct dps310_data {
> +	struct i2c_client *client;
> +	struct regmap *regmap;
> +
> +	s32 c0, c1;
> +	s32 temp_raw;
> +};
> +
> +static const struct iio_chan_spec dps310_channels[] = {
> +	{
> +		.type = IIO_TEMP,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_OFFSET) |
> +			BIT(IIO_CHAN_INFO_SCALE) |
> +			BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO) |
> +			BIT(IIO_CHAN_INFO_SAMP_FREQ) |
> +			BIT(IIO_CHAN_INFO_RAW),
> +	},
> +};
> +
> +static s32 dps310_twos_compliment(u32 raw, size_t num_bits)
> +{
> +	s32 out = raw;
> +
> +	if (raw & BIT(num_bits - 1))
> +		out = raw - BIT(num_bits);
> +
> +	return out;
> +}
> +
> +static int dps310_get_temp_coef(struct dps310_data *data)
> +{
> +	struct regmap *regmap = data->regmap;
> +	uint8_t coef[3] = {0};
> +	int ready, r;
> +	u32 c0, c1;
> +
> +	r = regmap_read(regmap, MEAS_CFG, &ready);
> +	if (r < 0)
> +		return r;
> +
> +	if (!(ready & COEF_RDY))
> +		return -EAGAIN;
> +
> +	/*
> +	 * Read temperature calibration coefficients c0 and c1 from the
> +	 * COEF register. The numbers are 12-bit 2's compliment numbers
> +	 */
> +	r = regmap_bulk_read(regmap, COEF_BASE, coef, 3);
> +	if (r < 0)
> +		return r;
> +
> +	c0 = (coef[0] << 4) | (coef[1] >> 4);
> +	data->c0 = dps310_twos_compliment(c0, 12);
> +
> +	c1 = ((coef[1] & GENMASK(3, 0)) << 8) | coef[2];
> +	data->c1 = dps310_twos_compliment(c1, 12);
> +
> +	return 0;
> +}
> +
> +static int dps310_get_temp_precision(struct dps310_data *data)
> +{
> +	int val, r;
> +
> +	r = regmap_read(data->regmap, TMP_CFG, &val);
> +	if (r < 0)
> +		return r;
> +
> +	/*
> +	 * Scale factor is bottom 4 bits of the register, but 1111 is
> +	 * reserved so just grab bottom three
> +	 */
> +	return BIT(val & GENMASK(2, 0));
> +}
> +
> +static int dps310_set_temp_precision(struct dps310_data *data, int val)
> +{
> +	int ret;
> +	u8 shift_en;
> +
> +	if (val < 0 || val > 128)
> +		return -EINVAL;
> +
> +	shift_en = val >= 16 ? TMP_SHIFT_EN : 0;
> +	ret = regmap_write_bits(data->regmap, CFG_REG, TMP_SHIFT_EN, shift_en);
> +	if (ret)
> +		return ret;
> +
> +	return regmap_update_bits(data->regmap, TMP_CFG, TMP_PRC_BITS,
> +			TMP_PRC(val));
> +}
> +
> +static int dps310_set_temp_samp_freq(struct dps310_data *data, int freq)
> +{
> +	uint8_t val;
> +
> +	if (freq < 0 || freq > 128)
> +		return -EINVAL;
> +
> +	val = ilog2(freq) << 4;
> +
> +	return regmap_update_bits(data->regmap, TMP_CFG, TMP_RATE_BITS, val);
> +}
> +
> +static int dps310_get_temp_samp_freq(struct dps310_data *data)
> +{
> +	int val, r;
> +
> +	r = regmap_read(data->regmap, TMP_CFG, &val);
> +	if (r < 0)
> +		return r;
> +
> +	return BIT((val & TMP_RATE_BITS) >> 4);
> +}
> +
> +static int dps310_get_temp_k(struct dps310_data *data)
> +{
> +	int index = ilog2(dps310_get_temp_precision(data));
> +
> +	return scale_factor[index];
I'd just put the whole thing in one line, but up to you.
> +}
> +
> +static int dps310_read_temp(struct dps310_data *data)
> +{
> +	struct device *dev = &data->client->dev;
> +	struct regmap *regmap = data->regmap;
> +	uint8_t val[3] = {0};
> +	int r, ready;
> +	int T_raw;
> +
> +	r = regmap_read(regmap, MEAS_CFG, &ready);
> +	if (r < 0)
> +		return r;
> +	if (!(ready & TMP_RDY)) {
> +		dev_dbg(dev, "temperature not ready\n");
> +		return -EAGAIN;
> +	}
> +
> +	r = regmap_bulk_read(regmap, TMP_BASE, val, 3);
> +	if (r < 0)
> +		return r;
> +
> +	T_raw = (val[0] << 16) | (val[1] << 8) | val[2];
> +	data->temp_raw = dps310_twos_compliment(T_raw, 24);
> +
> +	return 0;
> +}
> +
> +static bool dps310_is_writeable_reg(struct device *dev, unsigned int reg)
> +{
> +	switch (reg) {
> +	case PRS_CFG:
> +	case TMP_CFG:
> +	case MEAS_CFG:
> +	case CFG_REG:
> +	case RESET:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
> +static bool dps310_is_volatile_reg(struct device *dev, unsigned int reg)
> +{
> +	switch (reg) {
> +	case PRS_BASE ... (PRS_BASE + 2):
Bit ugly defining this like this.  IS PRS_BASE + 2 something that has
a logical name of its own?
> +	case TMP_BASE ... (TMP_BASE + 2):
> +	case MEAS_CFG:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
> +static int dps310_write_raw(struct iio_dev *iio,
> +			    struct iio_chan_spec const *chan, int val,
> +			    int val2, long mask)
> +{
> +	struct dps310_data *data = iio_priv(iio);
> +
> +	if (chan->type != IIO_TEMP)
> +		return -EINVAL;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		return dps310_set_temp_samp_freq(data, val);
> +	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
> +		return dps310_set_temp_precision(data, val);
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static int dps310_read_raw(struct iio_dev *iio,
> +			   struct iio_chan_spec const *chan,
> +			   int *val, int *val2, long mask)
> +{
> +	struct dps310_data *data = iio_priv(iio);
> +	int ret;
> +
> +	/* c0 * 0.5 + c1 * T_raw / kT ÂC */
Whilst interesting why is this comment right here?
> +	switch (mask) {
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		*val = dps310_get_temp_samp_freq(data);
> +		return IIO_VAL_INT;
> +
> +	case IIO_CHAN_INFO_RAW:
> +		ret = dps310_read_temp(data);
> +		if (ret)
> +			return ret;
> +
> +		*val = data->temp_raw * data->c1;
> +		return IIO_VAL_INT;
> +
> +	case IIO_CHAN_INFO_OFFSET:
> +		*val = (data->c0 >> 1) * dps310_get_temp_k(data);
> +		return IIO_VAL_INT;
> +
> +	case IIO_CHAN_INFO_SCALE:
> +		*val = MCELSIUS_PER_CELSIUS;
> +		*val2 = dps310_get_temp_k(data);
> +		return IIO_VAL_FRACTIONAL;
> +
> +	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
> +		*val = dps310_get_temp_precision(data);
> +		return IIO_VAL_INT;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static const struct regmap_config dps310_regmap_config = {
> +	.reg_bits = 8,
> +	.val_bits = 8,
> +	.writeable_reg = dps310_is_writeable_reg,
> +	.volatile_reg = dps310_is_volatile_reg,
> +	.cache_type = REGCACHE_RBTREE,
> +	.max_register = 0x29,
> +};
> +
> +static const struct iio_info dps310_info = {
> +	.driver_module = THIS_MODULE,
> +	.read_raw = dps310_read_raw,
> +	.write_raw = dps310_write_raw,
> +};
> +
> +static int dps310_probe(struct i2c_client *client,
> +			const struct i2c_device_id *id)
> +{
> +	struct dps310_data *data;
> +	struct iio_dev *iio;
> +	int r;
> +
> +	iio = devm_iio_device_alloc(&client->dev,  sizeof(*data));
> +	if (!iio)
> +		return -ENOMEM;
> +
> +	data = iio_priv(iio);
> +	data->client = client;
> +
> +	iio->dev.parent = &client->dev;
> +	iio->name = id->name;
> +	iio->channels = dps310_channels;
> +	iio->num_channels = ARRAY_SIZE(dps310_channels);
> +	iio->info = &dps310_info;
> +	iio->modes = INDIO_DIRECT_MODE;
> +
> +	data->regmap = devm_regmap_init_i2c(client, &dps310_regmap_config);
> +	if (IS_ERR(data->regmap))
> +		return PTR_ERR(data->regmap);
> +
Not that obvious what the next two calls are doing, perhaps comments?
(the third one is good)
> +	r = regmap_write(data->regmap, TMP_CFG, TMP_EXT | TMP_PRC(1));
> +	if (r < 0)
> +		return r;
> +	r = regmap_write_bits(data->regmap, CFG_REG, TMP_SHIFT_EN, 0);
> +	if (r < 0)
> +		return r;
> +
> +	/* Turn on temperature measurement in the background */
> +	r = regmap_write_bits(data->regmap, MEAS_CFG, MEAS_CTRL_BITS,
> +			TEMP_EN | BACKGROUND);
> +	if (r < 0)
> +		return r;
> +
> +	/*
> +	 * Calibration coefficients required for reporting temperature.
> +	 * They are availalbe 40ms after the device has started
available
> +	 */
> +	r = dps310_get_temp_coef(data);
> +	if (r == -EAGAIN)
> +		return -EPROBE_DEFER;
Deferred why?  If you need 40ms then sleep for 40ms to be sure it
has woken up. Or even better, loop with a sleep.

Deferred will only result in it being probed if something changes
such as another driver being loaded (which might provide
some resource we are waiting for).
> +	if (r < 0)
> +		return r;
> +
> +	r = devm_iio_device_register(&client->dev, iio);
> +	if (r)
> +		return r;
With the two lines below removed, just
return devm_iio...
> +
> +	i2c_set_clientdata(client, iio);
Used?
> +
> +	dev_info(&client->dev, "%s: sensor '%s'\n", dev_name(&iio->dev),
> +			client->name);
Provides little useful information and just spams the log so
I would prefer this was dropped.
> +
> +	return 0;
> +}
> +
> +static const struct i2c_device_id dps310_id[] = {
> +	{ "dps310", 0 },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(i2c, dps310_id);
> +
> +static const unsigned short normal_i2c[] = {
> +	0x77, 0x76, I2C_CLIENT_END
> +};
> +
> +static struct i2c_driver dps310_driver = {
> +	.driver = {
> +		.name = "dps310",
> +	},
> +	.probe = dps310_probe,
> +	.address_list = normal_i2c,
> +	.id_table = dps310_id,
> +};
> +module_i2c_driver(dps310_driver);
> +
> +MODULE_AUTHOR("Joel Stanley <joel@xxxxxxxxx>");
> +MODULE_DESCRIPTION("Infineon DPS310 pressure and temperature sensor");
> +MODULE_LICENSE("GPL");
>