Date:   Tue, 7 May 2019 11:01:36 -0500
From:   Eddie James <eajames@...ux.vnet.ibm.com>
To:     Peter Meerwald-Stadler <pmeerw@...erw.net>,
        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 5/6/19 4:18 PM, Peter Meerwald-Stadler wrote:
> On Mon, 6 May 2019, Eddie James wrote:
>
>> From: Joel Stanley <joel@....id.au>
> some comments below


Thanks for the quick review! Will get these in for v2, I did have a 
couple of questions below though.

Eddie


>   
>> 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\


OK, this may have to wait up to a second then, since the background 
measurement rate can be as low as 1 HZ... I can base the timeout on the 
sample rate. Would that be OK?


>
>> +		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


Don't think it's worth it? Would have to divide the offset by c1 and 
then multiply by c1 again in the scale...


>
>> +		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");
>>

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