Message-ID: <d151568e-d456-d37e-b7f6-bb1f38ab7f07@kernel.org>
Date:   Thu, 27 Apr 2017 07:19:45 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Guenter Roeck <linux@...ck-us.net>, Joel Stanley <joel@....id.au>
Cc:     Jean Delvare <jdelvare@...e.com>, linux-kernel@...r.kernel.org,
        linux-hwmon@...r.kernel.org, linux-iio@...r.kernel.org,
        openbmc@...ts.ozlabs.org
Subject: Re: [RFC PATCH] hwmon: Add driver for Infineon DPS310

On 26/04/17 16:13, Guenter Roeck wrote:
> Hi Joel,
> 
> On Thu, Apr 27, 2017 at 12:03:21AM +0930, Joel Stanley wrote:
>> Hi Guenter,
>>
>> Below is a work in progress hwmon driver for the DPS310[1]. The device does
>> both pressure and temperature monitoring over either I2C or SPI. There's a
>> public datasheet available on Infineon's website.
>>
>> I require a driver that reads the temperature data over I2C and exposes it to
>> userspace as a hwmon device. I wanted your opinion weather this should be an
>> IIO driver (and we could then use the IIO HWMON bridge in our application), or
>> if it should be a native HWMON driver?
>>
> 
> IIO, I think. Pressure isn't really for hardware monitoring, and we would have
> a hard time supporting it. IIO already has the necessary infrastructure for it.
> 
> Jonathan, any thoughts/comments ?
> 
Agree with you.  Pressure doesn't really fit in hwmon, so IIO is best location.
> Thanks,
> Guenter
> 
>> Once we've agreed on a subsystem I will clean the driver up and submit it
>> properly.
>>
>> Cheers,
>>
>> Joel
>>
>> [1] https://www.infineon.com/cms/en/product/sensor/capacitive-pressure-sensor-for-consumer-applications/channel.html
>>
>> ---
>>
>> The DPS310 is a temperature and pressure sensor. It can be accessed over
>> i2c and SPI.
>>
>> This driver supports continual measurement of temperature over i2c only.
>>
>> Signed-off-by: Joel Stanley <joel@....id.au>
>> ---
>>  drivers/hwmon/Kconfig  |  12 ++
>>  drivers/hwmon/Makefile |   1 +
>>  drivers/hwmon/dps310.c | 331 +++++++++++++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 344 insertions(+)
>>  create mode 100644 drivers/hwmon/dps310.c
>>
>> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
>> index 190d270b20a2..8229b2f8c591 100644
>> --- a/drivers/hwmon/Kconfig
>> +++ b/drivers/hwmon/Kconfig
>> @@ -1349,6 +1349,18 @@ config SENSORS_DME1737
>>  	  This driver can also be built as a module.  If so, the module
>>  	  will be called dme1737.
>>  
>> +config SENSORS_DPS310
>> +	tristate "Infineon DPS310"
>> +	depends on I2C
>> +	select HWMON_VID
>> +	select REGMAP_I2C
>> +	help
>> +	  If you say yes here you get support for the hardware monitoring
>> +	  features of 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 SENSORS_EMC1403
>>  	tristate "SMSC EMC1403/23 thermal sensor"
>>  	depends on I2C
>> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
>> index d2cb7e804a0f..3a5ad06d6d89 100644
>> --- a/drivers/hwmon/Makefile
>> +++ b/drivers/hwmon/Makefile
>> @@ -52,6 +52,7 @@ obj-$(CONFIG_SENSORS_DA9052_ADC)+= da9052-hwmon.o
>>  obj-$(CONFIG_SENSORS_DA9055)+= da9055-hwmon.o
>>  obj-$(CONFIG_SENSORS_DELL_SMM)	+= dell-smm-hwmon.o
>>  obj-$(CONFIG_SENSORS_DME1737)	+= dme1737.o
>> +obj-$(CONFIG_SENSORS_DPS310)	+= dps310.o
>>  obj-$(CONFIG_SENSORS_DS620)	+= ds620.o
>>  obj-$(CONFIG_SENSORS_DS1621)	+= ds1621.o
>>  obj-$(CONFIG_SENSORS_EMC1403)	+= emc1403.o
>> diff --git a/drivers/hwmon/dps310.c b/drivers/hwmon/dps310.c
>> new file mode 100644
>> index 000000000000..b014f01d0d3f
>> --- /dev/null
>> +++ b/drivers/hwmon/dps310.c
>> @@ -0,0 +1,331 @@
>> +/*
>> + * Copyright 2017 IBM Corporation
>> + *
>> + * Joel Stanley <joel@....id.au>
>> + *
>> + * The DPS310 is a barometric pressure and temperature sensor.
>> + *
>> + * 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.
>> + */
>> +
>> +#include <linux/i2c.h>
>> +#include <linux/regmap.h>
>> +#include <linux/hwmon.h>
>> +#include <linux/module.h>
>> +
>> +#define PRS_B2		0x00
>> +#define PRS_B1		0x01
>> +#define PRS_B0		0x02
>> +#define TMP_B2		0x03
>> +#define TMP_B1		0x04
>> +#define TMP_B0		0x05
>> +#define PRS_CFG		0x06
>> +#define TMP_CFG		0x07
>> +#define  TMP_RATE_BITS	GENMASK(6, 4)
>> +#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 RESET		0x0c
>> +#define  RESET_MAGIC	(BIT(0) | BIT(3))
>> +#define COEF_BASE	0x10
>> +
>> +#define TMP_BASE	TMP_B2
>> +#define PRS_BASE	PRS_B2
>> +
>> +#define TMP_RATE(_n)	ilog2(_n)
>> +#define TMP_PRC(_n)	ilog2(_n)
>> +
>> +const int scale_factor[] = {
>> +	 524288,
>> +	1572864,
>> +	3670016,
>> +	7864320,
>> +	 253952,
>> +	 516096,
>> +	1040384,
>> +	2088960,
>> +};
>> +
>> +struct dps310_data {
>> +	struct regmap *regmap;
>> +	int interval;
>> +	s32 c0, c1;
>> +};
>> +
>> +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_scale_factor(struct device *dev)
>> +{
>> +	struct dps310_data *data = dev_get_drvdata(dev);
>> +	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 */
>> +	val = val & GENMASK(3, 0);
>> +	if (val < 0 || val > ARRAY_SIZE(scale_factor))
>> +		return -EINVAL;
>> +
>> +	return scale_factor[val];
>> +}
>> +
>> +static int dps310_read_temp(struct device *dev, u32 attr, int channel,
>> +			     long *temp)
>> +{
>> +	struct dps310_data *data = dev_get_drvdata(dev);
>> +	struct regmap *regmap = data->regmap;
>> +	uint8_t val[3] = {0};
>> +	int r, ready;
>> +	int kT, T_raw;
>> +
>> +	switch (attr) {
>> +	case hwmon_temp_input:
>> +		r = regmap_read(regmap, MEAS_CFG, &ready);
>> +		if (r < 0)
>> +			return r;
>> +		if (!(ready & TMP_RDY)) {
>> +			dev_err(dev, "tmp not ready\n");
>> +			return -EAGAIN;
>> +		}
>> +
>> +		/* Choose scaling factor kT based on chosen precision rate */
>> +		kT = dps310_get_scale_factor(dev);
>> +
>> +		r = regmap_bulk_read(regmap, TMP_BASE, val, 3);
>> +		if (r < 0)
>> +			return r;
>> +		T_raw = (val[0] << 16) | (val[1] << 8) | val[2];
>> +		T_raw = dps310_twos_compliment(T_raw, 24);
>> +
>> +		/* (c0 * 0.5 + c1 * T_raw / kT) * 1000 m°C */
>> +		*temp = ((data->c0 >> 1) + (data->c1 * T_raw) / kT) * 1000;
>> +
>> +		return 0;
>> +	default:
>> +		return -EOPNOTSUPP;
>> +	}
>> +}
>> +
>> +static int dps310_read(struct device *dev, enum hwmon_sensor_types type,
>> +			u32 attr, int channel, long *val)
>> +{
>> +	switch (type) {
>> +	case hwmon_temp:
>> +		return dps310_read_temp(dev, attr, channel, val);
>> +	default:
>> +		return -EOPNOTSUPP;
>> +	}
>> +}
>> +
>> +static int dps310_write(struct device *dev, enum hwmon_sensor_types type,
>> +			 u32 attr, int channel, long val)
>> +{
>> +	switch (type) {
>> +	case hwmon_temp:
>> +		/* Fall through */
>> +	default:
>> +		return -EOPNOTSUPP;
>> +	}
>> +}
>> +
>> +static umode_t dps310_is_visible(const void *data,
>> +				  enum hwmon_sensor_types type,
>> +				  u32 attr, int channel)
>> +{
>> +	switch (type) {
>> +	case hwmon_temp:
>> +		switch (attr) {
>> +		case hwmon_temp_input:
>> +			return 0444;
>> +		default:
>> +			return 0;
>> +		}
>> +	default:
>> +		return 0;
>> +	}
>> +}
>> +
>> +
>> +static const u32 dps310_temp_config[] = {
>> +	HWMON_T_INPUT,
>> +	0
>> +};
>> +
>> +static const struct hwmon_channel_info dps310_temp = {
>> +	.type = hwmon_temp,
>> +	.config = dps310_temp_config,
>> +};
>> +
>> +static const struct hwmon_channel_info *dps310_info[] = {
>> +	&dps310_temp,
>> +	NULL
>> +};
>> +
>> +static const struct hwmon_ops dps310_hwmon_ops = {
>> +	.is_visible = dps310_is_visible,
>> +	.read = dps310_read,
>> +	.write = dps310_write,
>> +};
>> +
>> +static const struct hwmon_chip_info dps310_chip_info = {
>> +	.ops = &dps310_hwmon_ops,
>> +	.info = dps310_info,
>> +};
>> +
>> +static bool dps310_is_writeable_reg(struct device *dev, unsigned int reg)
>> +{
>> +	switch (reg) {
>> +	case PRS_CFG:
>> +	case TMP_CFG:
>> +	case MEAS_CFG:
>> +	case RESET:
>> +		return true;
>> +	default:
>> +		return false;
>> +	}
>> +}
>> +
>> +static bool dps310_is_volatile_reg(struct device *dev, unsigned int reg)
>> +{
>> +	switch (reg) {
>> +	case PRS_B2:
>> +	case PRS_B1:
>> +	case PRS_B0:
>> +	case TMP_B2:
>> +	case TMP_B1:
>> +	case TMP_B0:
>> +	case MEAS_CFG:
>> +		return true;
>> +	default:
>> +		return false;
>> +	}
>> +}
>> +
>> +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,
>> +	.use_single_rw = true,
>> +};
>> +
>> +static int dps310_probe(struct i2c_client *client,
>> +			const struct i2c_device_id *id)
>> +{
>> +	struct dps310_data *data;
>> +	struct device *hwmon_dev;
>> +	int r;
>> +
>> +	data = devm_kzalloc(&client->dev,  sizeof(*data), GFP_KERNEL);
>> +	if (!data)
>> +		return -ENOMEM;
>> +
>> +	data->regmap = devm_regmap_init_i2c(client, &dps310_regmap_config);
>> +	if (IS_ERR(data->regmap))
>> +		return PTR_ERR(data->regmap);
>> +
>> +	r = regmap_write(data->regmap, TMP_CFG, TMP_EXT | TMP_PRC(128));
>> +	if (r < 0)
>> +		return r;
>> +
>> +	/* Turn on background temperature measurement */
>> +	r = regmap_update_bits(data->regmap, MEAS_CFG, MEAS_CTRL_BITS,
>> +			TEMP_EN);
>> +	if (r < 0)
>> +		return r;
>> +
>> +	/* Get calibration coefficients required for reporting temperature */
>> +	r = dps310_get_temp_coef(data);
>> +	if (r == -EAGAIN)
>> +		return -EPROBE_DEFER;
>> +	if (r < 0)
>> +		return r;
>> +
>> +	hwmon_dev = devm_hwmon_device_register_with_info(&client->dev,
>> +			client->name, data, &dps310_chip_info, NULL);
>> +
>> +	if (IS_ERR(hwmon_dev))
>> +		return PTR_ERR(hwmon_dev);
>> +
>> +	dev_info(&client->dev, "%s: sensor '%s'\n", dev_name(hwmon_dev),
>> +			client->name);
>> +
>> +	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 = {
>> +	.class = I2C_CLASS_HWMON,
>> +	.driver = {
>> +		.name = "dps310",
>> +	},
>> +	.probe = dps310_probe,
>> +	.address_list = normal_i2c,
>> +	.id_table = dps310_id,
>> +};
>> +module_i2c_driver(dps310_driver);
>> +
>> +MODULE_AUTHOR("Joel Stanley <joel@....id.au>");
>> +MODULE_DESCRIPTION("Infineon DPS310 driver");
>> +MODULE_LICENSE("GPL");
>> -- 
>> 2.11.0
>>
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