iio: pressure: hp03: Add Hope RF HP03 sensor support

Add support for HopeRF pressure and temperature sensor.

This device uses two fixed I2C addresses, one for storing
calibration coefficients and another for accessing the ADC.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Matt Ranostay <mranostay@gmail.com>
Cc: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

Documentation/devicetree/bindings/iio/pressure/hp03.txt

@@ -0,0 +1,17 @@
+HopeRF HP03 digital pressure/temperature sensors
+
+Required properties:
+- compatible: must be "hoperf,hp03"
+- xclr-gpio: must be device tree identifier of the XCLR pin.
+             The XCLR pin is a reset of the ADC in the chip,
+             it must be pulled HI before the conversion and
+             readout of the value from the ADC registers and
+             pulled LO afterward.
+
+Example:
+
+hp03@0x77 {
+	compatible = "hoperf,hp03";
+	reg = <0x77>;
+	xclr-gpio = <&portc 0 0x0>;
+};

drivers/iio/pressure/Kconfig

@@ -30,6 +30,17 @@ config HID_SENSOR_PRESS
 	  To compile this driver as a module, choose M here: the module
 	  will be called hid-sensor-press.
 
+config HP03
+	tristate "Hope RF HP03 temperature and pressure sensor driver"
+	depends on I2C
+	select REGMAP_I2C
+	help
+	  Say yes here to build support for Hope RF HP03 pressure and
+	  temperature sensor.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called hp03.
+
 config MPL115
 	tristate
 

drivers/iio/pressure/Makefile

@@ -5,6 +5,7 @@
 # When adding new entries keep the list in alphabetical order
 obj-$(CONFIG_BMP280) += bmp280.o
 obj-$(CONFIG_HID_SENSOR_PRESS)   += hid-sensor-press.o
+obj-$(CONFIG_HP03) += hp03.o
 obj-$(CONFIG_MPL115) += mpl115.o
 obj-$(CONFIG_MPL115_I2C) += mpl115_i2c.o
 obj-$(CONFIG_MPL115_SPI) += mpl115_spi.o

drivers/iio/pressure/hp03.c

@@ -0,0 +1,312 @@
+/*
+ * Copyright (c) 2016 Marek Vasut <marex@denx.de>
+ *
+ * Driver for Hope RF HP03 digital temperature and pressure sensor.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#define pr_fmt(fmt) "hp03: " fmt
+
+#include <linux/module.h>
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/regmap.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+/*
+ * The HP03 sensor occupies two fixed I2C addresses:
+ *  0x50 ... read-only EEPROM with calibration data
+ *  0x77 ... read-write ADC for pressure and temperature
+ */
+#define HP03_EEPROM_ADDR		0x50
+#define HP03_ADC_ADDR			0x77
+
+#define HP03_EEPROM_CX_OFFSET		0x10
+#define HP03_EEPROM_AB_OFFSET		0x1e
+#define HP03_EEPROM_CD_OFFSET		0x20
+
+#define HP03_ADC_WRITE_REG		0xff
+#define HP03_ADC_READ_REG		0xfd
+#define HP03_ADC_READ_PRESSURE		0xf0	/* D1 in datasheet */
+#define HP03_ADC_READ_TEMP		0xe8	/* D2 in datasheet */
+
+struct hp03_priv {
+	struct i2c_client	*client;
+	struct mutex		lock;
+	struct gpio_desc	*xclr_gpio;
+
+	struct i2c_client	*eeprom_client;
+	struct regmap		*eeprom_regmap;
+
+	s32			pressure;	/* kPa */
+	s32			temp;		/* Deg. C */
+};
+
+static const struct iio_chan_spec hp03_channels[] = {
+	{
+		.type = IIO_PRESSURE,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
+	},
+	{
+		.type = IIO_TEMP,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
+	},
+};
+
+static bool hp03_is_writeable_reg(struct device *dev, unsigned int reg)
+{
+	return false;
+}
+
+static bool hp03_is_volatile_reg(struct device *dev, unsigned int reg)
+{
+	return false;
+}
+
+static const struct regmap_config hp03_regmap_config = {
+	.reg_bits	= 8,
+	.val_bits	= 8,
+
+	.max_register	= HP03_EEPROM_CD_OFFSET + 1,
+	.cache_type	= REGCACHE_RBTREE,
+
+	.writeable_reg	= hp03_is_writeable_reg,
+	.volatile_reg	= hp03_is_volatile_reg,
+};
+
+static int hp03_get_temp_pressure(struct hp03_priv *priv, const u8 reg)
+{
+	int ret;
+
+	ret = i2c_smbus_write_byte_data(priv->client, HP03_ADC_WRITE_REG, reg);
+	if (ret < 0)
+		return ret;
+
+	msleep(50);	/* Wait for conversion to finish */
+
+	return i2c_smbus_read_word_data(priv->client, HP03_ADC_READ_REG);
+}
+
+static int hp03_update_temp_pressure(struct hp03_priv *priv)
+{
+	struct device *dev = &priv->client->dev;
+	u8 coefs[18];
+	u16 cx_val[7];
+	int ab_val, d1_val, d2_val, diff_val, dut, off, sens, x;
+	int i, ret;
+
+	/* Sample coefficients from EEPROM */
+	ret = regmap_bulk_read(priv->eeprom_regmap, HP03_EEPROM_CX_OFFSET,
+			       coefs, sizeof(coefs));
+	if (ret < 0) {
+		dev_err(dev, "Failed to read EEPROM (reg=%02x)\n",
+			HP03_EEPROM_CX_OFFSET);
+		return ret;
+	}
+
+	/* Sample Temperature and Pressure */
+	gpiod_set_value_cansleep(priv->xclr_gpio, 1);
+
+	ret = hp03_get_temp_pressure(priv, HP03_ADC_READ_PRESSURE);
+	if (ret < 0) {
+		dev_err(dev, "Failed to read pressure\n");
+		goto err_adc;
+	}
+	d1_val = ret;
+
+	ret = hp03_get_temp_pressure(priv, HP03_ADC_READ_TEMP);
+	if (ret < 0) {
+		dev_err(dev, "Failed to read temperature\n");
+		goto err_adc;
+	}
+	d2_val = ret;
+
+	gpiod_set_value_cansleep(priv->xclr_gpio, 0);
+
+	/* The Cx coefficients and Temp/Pressure values are MSB first. */
+	for (i = 0; i < 7; i++)
+		cx_val[i] = (coefs[2 * i] << 8) | (coefs[(2 * i) + 1] << 0);
+	d1_val = ((d1_val >> 8) & 0xff) | ((d1_val & 0xff) << 8);
+	d2_val = ((d2_val >> 8) & 0xff) | ((d2_val & 0xff) << 8);
+
+	/* Coefficient voodoo from the HP03 datasheet. */
+	if (d2_val >= cx_val[4])
+		ab_val = coefs[14];	/* A-value */
+	else
+		ab_val = coefs[15];	/* B-value */
+
+	diff_val = d2_val - cx_val[4];
+	dut = (ab_val * (diff_val >> 7) * (diff_val >> 7)) >> coefs[16];
+	dut = diff_val - dut;
+
+	off = (cx_val[1] + (((cx_val[3] - 1024) * dut) >> 14)) * 4;
+	sens = cx_val[0] + ((cx_val[2] * dut) >> 10);
+	x = ((sens * (d1_val - 7168)) >> 14) - off;
+
+	priv->pressure = ((x * 100) >> 5) + (cx_val[6] * 10);
+	priv->temp = 250 + ((dut * cx_val[5]) >> 16) - (dut >> coefs[17]);
+
+	return 0;
+
+err_adc:
+	gpiod_set_value_cansleep(priv->xclr_gpio, 0);
+	return ret;
+}
+
+static int hp03_read_raw(struct iio_dev *indio_dev,
+			 struct iio_chan_spec const *chan,
+			 int *val, int *val2, long mask)
+{
+	struct hp03_priv *priv = iio_priv(indio_dev);
+	int ret;
+
+	mutex_lock(&priv->lock);
+	ret = hp03_update_temp_pressure(priv);
+	mutex_unlock(&priv->lock);
+
+	if (ret)
+		return ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		switch (chan->type) {
+		case IIO_PRESSURE:
+			*val = priv->pressure;
+			return IIO_VAL_INT;
+		case IIO_TEMP:
+			*val = priv->temp;
+			return IIO_VAL_INT;
+		default:
+			return -EINVAL;
+		}
+		break;
+	case IIO_CHAN_INFO_SCALE:
+		switch (chan->type) {
+		case IIO_PRESSURE:
+			*val = 0;
+			*val2 = 1000;
+			return IIO_VAL_INT_PLUS_MICRO;
+		case IIO_TEMP:
+			*val = 10;
+			return IIO_VAL_INT;
+		default:
+			return -EINVAL;
+		}
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return -EINVAL;
+}
+
+static const struct iio_info hp03_info = {
+	.driver_module	= THIS_MODULE,
+	.read_raw	= &hp03_read_raw,
+};
+
+static int hp03_probe(struct i2c_client *client,
+		      const struct i2c_device_id *id)
+{
+	struct device *dev = &client->dev;
+	struct iio_dev *indio_dev;
+	struct hp03_priv *priv;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*priv));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	priv = iio_priv(indio_dev);
+	priv->client = client;
+	mutex_init(&priv->lock);
+
+	indio_dev->dev.parent = dev;
+	indio_dev->name = id->name;
+	indio_dev->channels = hp03_channels;
+	indio_dev->num_channels = ARRAY_SIZE(hp03_channels);
+	indio_dev->info = &hp03_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+
+	priv->xclr_gpio = devm_gpiod_get_index(dev, "xclr", 0, GPIOD_OUT_HIGH);
+	if (IS_ERR(priv->xclr_gpio)) {
+		dev_err(dev, "Failed to claim XCLR GPIO\n");
+		ret = PTR_ERR(priv->xclr_gpio);
+		return ret;
+	}
+
+	/*
+	 * Allocate another device for the on-sensor EEPROM,
+	 * which has it's dedicated I2C address and contains
+	 * the calibration constants for the sensor.
+	 */
+	priv->eeprom_client = i2c_new_dummy(client->adapter, HP03_EEPROM_ADDR);
+	if (!priv->eeprom_client) {
+		dev_err(dev, "New EEPROM I2C device failed\n");
+		return -ENODEV;
+	}
+
+	priv->eeprom_regmap = regmap_init_i2c(priv->eeprom_client,
+					      &hp03_regmap_config);
+	if (IS_ERR(priv->eeprom_regmap)) {
+		dev_err(dev, "Failed to allocate EEPROM regmap\n");
+		ret = PTR_ERR(priv->eeprom_regmap);
+		goto err_cleanup_eeprom_client;
+	}
+
+	ret = iio_device_register(indio_dev);
+	if (ret) {
+		dev_err(dev, "Failed to register IIO device\n");
+		goto err_cleanup_eeprom_regmap;
+	}
+
+	i2c_set_clientdata(client, indio_dev);
+
+	return 0;
+
+err_cleanup_eeprom_regmap:
+	regmap_exit(priv->eeprom_regmap);
+
+err_cleanup_eeprom_client:
+	i2c_unregister_device(priv->eeprom_client);
+	return ret;
+}
+
+static int hp03_remove(struct i2c_client *client)
+{
+	struct iio_dev *indio_dev = i2c_get_clientdata(client);
+	struct hp03_priv *priv = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+	regmap_exit(priv->eeprom_regmap);
+	i2c_unregister_device(priv->eeprom_client);
+
+	return 0;
+}
+
+static const struct i2c_device_id hp03_id[] = {
+	{ "hp03", 0 },
+	{ },
+};
+MODULE_DEVICE_TABLE(i2c, hp03_id);
+
+static struct i2c_driver hp03_driver = {
+	.driver = {
+		.name	= "hp03",
+	},
+	.probe		= hp03_probe,
+	.remove		= hp03_remove,
+	.id_table	= hp03_id,
+};
+module_i2c_driver(hp03_driver);
+
+MODULE_AUTHOR("Marek Vasut <marex@denx.de>");
+MODULE_DESCRIPTION("Driver for Hope RF HP03 pressure and temperature sensor");
+MODULE_LICENSE("GPL v2");