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Date:   Sat, 11 May 2019 10:52:08 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Eddie James <eajames@...ux.vnet.ibm.com>
Cc:     Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Eddie James <eajames@...ux.ibm.com>, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, joel@....id.au
Subject: Re: [PATCH 1/3] iio: Add driver for Infineon DPS310

On Tue, 7 May 2019 11:01:36 -0500
Eddie James <eajames@...ux.vnet.ibm.com> wrote:

> 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?
Yes. I may be that we actually want to pick a my power hungry and faster
default to avoid any stupid userspace programs wondering why they
don't get an answer for 1 second.

> 
> 
> >  
> >> +		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...

I think you are actually better just reporting as PROCESSED.

> 
> 
> >  
> >> +		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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