Message-ID: <alpine.DEB.2.21.1905062304280.717@vps.pmeerw.net>
Date:   Mon, 6 May 2019 23:18:41 +0200 (CEST)
From:   Peter Meerwald-Stadler <pmeerw@...erw.net>
To:     Eddie James <eajames@...ux.ibm.com>
cc:     linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        joel@....id.au, jic23@...nel.org
Subject: Re: [PATCH 1/3] iio: Add driver for Infineon DPS310

On Mon, 6 May 2019, Eddie James wrote:

> From: Joel Stanley <joel@....id.au>

some comments below
 
> The DPS310 is a temperature and pressure sensor. It can be accessed over
> i2c and SPI.
> 
> Signed-off-by: Eddie James <eajames@...ux.ibm.com>
> ---
>  MAINTAINERS                   |   6 +
>  drivers/iio/pressure/Kconfig  |  10 +
>  drivers/iio/pressure/Makefile |   1 +
>  drivers/iio/pressure/dps310.c | 429 ++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 446 insertions(+)
>  create mode 100644 drivers/iio/pressure/dps310.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index c61c49d..a91dfa9 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -7743,6 +7743,12 @@ W:	http://industrypack.sourceforge.net
>  S:	Maintained
>  F:	drivers/ipack/
>  
> +INFINEON DPS310 Driver
> +M:	Eddie James <eajames@...ux.ibm.com>
> +L:	linux-iio@...r.kernel.org
> +F:	drivers/iio/pressure/dps310.c
> +S:	Maintained
> +
>  INFINIBAND SUBSYSTEM
>  M:	Doug Ledford <dledford@...hat.com>
>  M:	Jason Gunthorpe <jgg@...lanox.com>
> diff --git a/drivers/iio/pressure/Kconfig b/drivers/iio/pressure/Kconfig
> index efeb89f..681a1cc 100644
> --- a/drivers/iio/pressure/Kconfig
> +++ b/drivers/iio/pressure/Kconfig
> @@ -52,6 +52,16 @@ config IIO_CROS_EC_BARO
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called cros_ec_baro.
>  
> +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 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 c2058d7..d8f5ace 100644
> --- a/drivers/iio/pressure/Makefile
> +++ b/drivers/iio/pressure/Makefile
> @@ -9,6 +9,7 @@ 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-$(CONFIG_IIO_CROS_EC_BARO) += cros_ec_baro.o
>  obj-$(CONFIG_HID_SENSOR_PRESS)   += hid-sensor-press.o
>  obj-$(CONFIG_HP03) += hp03.o
> diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
> new file mode 100644
> index 0000000..21d5dcb
> --- /dev/null
> +++ b/drivers/iio/pressure/dps310.c
> @@ -0,0 +1,429 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +// Copyright IBM Corp 2019
> +/*
> + * The DPS310 is a barometric pressure and temperature sensor.
> + * Currently only reading a single temperature is supported by
> + * this driver.
> + *
> + * https://www.infineon.com/dgdl/?fileId=5546d462576f34750157750826c42242
> + *
> + * Temperature calculation:
> + *   c0 * 0.5 + c1 * T_raw / kT °C
> + *
> + * TODO:
> + *  - Pressure sensor readings
> + *  - Optionally support the FIFO
> + */
> +
> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +#include <linux/regmap.h>
> +
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +
> +#define DPS310_PRS_B0		0x00
> +#define DPS310_PRS_B1		0x01
> +#define DPS310_PRS_B2		0x02
> +#define DPS310_TMP_B0		0x03
> +#define DPS310_TMP_B1		0x04
> +#define DPS310_TMP_B2		0x05
> +#define DPS310_PRS_CFG		0x06
> +#define DPS310_TMP_CFG		0x07
> +#define  DPS310_TMP_RATE_BITS	GENMASK(6, 4)
> +#define  DPS310_TMP_PRC_BITS	GENMASK(3, 0)
> +#define  DPS310_TMP_EXT		BIT(7)
> +#define DPS310_MEAS_CFG		0x08
> +#define  DPS310_MEAS_CTRL_BITS	GENMASK(2, 0)
> +#define   DPS310_PRS_EN		BIT(0)
> +#define   DPS310_TEMP_EN	BIT(1)
> +#define   DPS310_BACKGROUND	BIT(2)
> +#define  DPS310_PRS_RDY		BIT(4)
> +#define  DPS310_TMP_RDY		BIT(5)
> +#define  DPS310_SENSOR_RDY	BIT(6)
> +#define  DPS310_COEF_RDY	BIT(7)
> +#define DPS310_CFG_REG		0x09
> +#define  DPS310_INT_HL		BIT(7)
> +#define  DPS310_TMP_SHIFT_EN	BIT(3)
> +#define  DPS310_PRS_SHIFT_EN	BIT(4)
> +#define  DPS310_FIFO_EN		BIT(5)
> +#define  DPS310_SPI_EN		BIT(6)
> +#define DPS310_RESET		0x0c
> +#define  DPS310_RESET_MAGIC	(BIT(0) | BIT(3))
> +#define DPS310_COEF_BASE	0x10
> +
> +#define DPS310_PRS_BASE		DPS310_PRS_B0
> +#define DPS310_TMP_BASE		DPS310_TMP_B0
> +
> +#define DPS310_CALC_RATE(_n)	ilog2(_n)
> +#define DPS310_CALC_PRC(_n)	ilog2(_n)
> +
> +const int scale_factor[] = {

static
maybe plural, scale_factors?
maybe some comment would be good what these values relate to

> +	 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),
> +	},
> +};
> +
> +/* To be called after checking the TMP_RDY bit in MEAS_CFG */
> +static int dps310_get_temp_coef(struct dps310_data *data)
> +{
> +	struct regmap *regmap = data->regmap;
> +	u8 coef[3] = {0};

initialization needed?

> +	int r;
> +	u32 c0, c1;
> +
> +	/*
> +	 * 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, DPS310_COEF_BASE, coef, 3);

sizeof(coef) instead of 3

> +	if (r < 0)
> +		return r;
> +
> +	c0 = (coef[0] << 4) | (coef[1] >> 4);
> +	data->c0 = sign_extend32(c0, 11);
> +
> +	c1 = ((coef[1] & GENMASK(3, 0)) << 8) | coef[2];
> +	data->c1 = sign_extend32(c1, 11);
> +
> +	return 0;
> +}
> +
> +static int dps310_get_temp_precision(struct dps310_data *data)
> +{
> +	int val, r;
> +
> +	r = regmap_read(data->regmap, DPS310_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 ? DPS310_TMP_SHIFT_EN : 0;
> +	ret = regmap_write_bits(data->regmap, DPS310_CFG_REG,
> +				DPS310_TMP_SHIFT_EN, shift_en);
> +	if (ret)
> +		return ret;
> +
> +	return regmap_update_bits(data->regmap, DPS310_TMP_CFG,
> +				  DPS310_TMP_PRC_BITS, DPS310_CALC_PRC(val));
> +}
> +
> +static int dps310_set_temp_samp_freq(struct dps310_data *data, int freq)
> +{
> +	u8 val;
> +
> +	if (freq < 0 || freq > 128)
> +		return -EINVAL;
> +
> +	val = DPS310_CALC_RATE(freq) << 4;
> +
> +	return regmap_update_bits(data->regmap, DPS310_TMP_CFG,
> +				  DPS310_TMP_RATE_BITS, val);
> +}
> +
> +static int dps310_get_temp_samp_freq(struct dps310_data *data)
> +{
> +	int val, r;
> +
> +	r = regmap_read(data->regmap, DPS310_TMP_CFG, &val);
> +	if (r < 0)
> +		return r;
> +
> +	return BIT((val & DPS310_TMP_RATE_BITS) >> 4);
> +}
> +
> +static int dps310_get_temp_k(struct dps310_data *data)
> +{
> +	int r = dps310_get_temp_precision(data);
> +
> +	if (r < 0)
> +		return r;
> +
> +	return scale_factor[DPS310_CALC_PRC(r)];
> +}
> +
> +static int dps310_read_temp(struct dps310_data *data)
> +{
> +	struct device *dev = &data->client->dev;
> +	struct regmap *regmap = data->regmap;
> +	u8 val[3] = {0};

initialization needed?

> +	int r, ready;
> +	int T_raw;
> +
> +	r = regmap_read(regmap, DPS310_MEAS_CFG, &ready);
> +	if (r < 0)
> +		return r;
> +	if (!(ready & DPS310_TMP_RDY)) {
> +		dev_dbg(dev, "temperature not ready\n");

most drivers wait for the results to become ready

> +		return -EAGAIN;
> +	}
> +
> +	r = regmap_bulk_read(regmap, DPS310_TMP_BASE, val, 3);

sizeof(val)

> +	if (r < 0)
> +		return r;
> +
> +	T_raw = (val[0] << 16) | (val[1] << 8) | val[2];
> +	data->temp_raw = sign_extend32(T_raw, 23);
> +
> +	return 0;
> +}
> +
> +static bool dps310_is_writeable_reg(struct device *dev, unsigned int reg)
> +{
> +	switch (reg) {
> +	case DPS310_PRS_CFG:
> +	case DPS310_TMP_CFG:
> +	case DPS310_MEAS_CFG:
> +	case DPS310_CFG_REG:
> +	case DPS310_RESET:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
> +static bool dps310_is_volatile_reg(struct device *dev, unsigned int reg)
> +{
> +	switch (reg) {
> +	case DPS310_PRS_B0:
> +	case DPS310_PRS_B1:
> +	case DPS310_PRS_B2:
> +	case DPS310_TMP_B0:
> +	case DPS310_TMP_B1:
> +	case DPS310_TMP_B2:
> +	case DPS310_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;

not needed, dead code

> +}
> +
> +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;
> +
> +	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;

one could try to avoid the multipliation here and somehow mangle it into 
_SCALE/_OFFSET

> +		return IIO_VAL_INT;
> +
> +	case IIO_CHAN_INFO_OFFSET:
> +		ret = dps310_get_temp_k(data);
> +		if (ret < 0)
> +			return ret;
> +
> +		*val = (data->c0 >> 1) * ret;
> +		return IIO_VAL_INT;
> +
> +	case IIO_CHAN_INFO_SCALE:
> +		ret = dps310_get_temp_k(data);
> +		if (ret < 0)
> +			return ret;
> +
> +		*val = 1000; /* milliCelsius per Celsius */
> +		*val2 = ret;
> +		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;

not needed, dead code

> +}
> +
> +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 = {
> +	.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, ready;
> +
> +	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);
> +
> +	/*
> +	 * Set up external (MEMS) temperature sensor in single sample, one
> +	 * measurement per second mode
> +	 */
> +	r = regmap_write(data->regmap, DPS310_TMP_CFG,
> +			 DPS310_TMP_EXT | DPS310_CALC_RATE(1) |
> +			 DPS310_CALC_PRC(1));
> +	if (r < 0)
> +		goto err;
> +
> +	/* Temp shift is disabled when PRC <= 8 */
> +	r = regmap_write_bits(data->regmap, DPS310_CFG_REG,
> +			      DPS310_TMP_SHIFT_EN, 0);
> +	if (r < 0)
> +		goto err;
> +
> +	/* Turn on temperature measurement in the background */
> +	r = regmap_write_bits(data->regmap, DPS310_MEAS_CFG,
> +			      DPS310_MEAS_CTRL_BITS,
> +			      DPS310_TEMP_EN | DPS310_BACKGROUND);
> +	if (r < 0)
> +		goto err;
> +
> +	/*
> +	 * Calibration coefficients required for reporting temperature.
> +	 * They are available 40ms after the device has started
> +	 */
> +	r = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG, ready,
> +				     ready & DPS310_COEF_RDY, 10000, 40000);
> +	if (r < 0)
> +		goto err;
> +
> +	r = dps310_get_temp_coef(data);
> +	if (r < 0)
> +		goto err;
> +
> +	r = devm_iio_device_register(&client->dev, iio);
> +	if (r)
> +		goto err;
> +
> +	i2c_set_clientdata(client, iio);
> +
> +	dev_info(&client->dev, "%s: sensor '%s'\n", dev_name(&iio->dev),
> +		 client->name);

don't clutter the log

> +
> +	return 0;
> +
> +err:
> +	regmap_write(data->regmap, DPS310_RESET, DPS310_RESET_MAGIC);
> +	return r;
> +}
> +
> +static int dps310_remove(struct i2c_client *client)
> +{
> +	struct dps310_data *data = i2c_get_clientdata(client);
> +
> +	return regmap_write(data->regmap, DPS310_RESET, DPS310_RESET_MAGIC);
> +}
> +
> +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,
> +	.remove = dps310_remove,
> +	.address_list = normal_i2c,
> +	.id_table = dps310_id,
> +};
> +module_i2c_driver(dps310_driver);
> +
> +MODULE_AUTHOR("Joel Stanley <joel@....id.au>");
> +MODULE_DESCRIPTION("Infineon DPS310 pressure and temperature sensor");
> +MODULE_LICENSE("GPL v2");
> 

-- 

Peter Meerwald-Stadler
Mobile: +43 664 24 44 418

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