[PATCH] iio: Add driver for Infineon DPS310

[Joel Stanley]

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>
---
 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>
+
+#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)
+#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];
+}
+
+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):
+	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 */
+	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);
+
+	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
+	 */
+	r = dps310_get_temp_coef(data);
+	if (r == -EAGAIN)
+		return -EPROBE_DEFER;
+	if (r < 0)
+		return r;
+
+	r = devm_iio_device_register(&client->dev, iio);
+	if (r)
+		return r;
+
+	i2c_set_clientdata(client, iio);
+
+	dev_info(&client->dev, "%s: sensor '%s'\n", dev_name(&iio->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 = {
+	.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");
-- 
2.11.0