Message-Id: <20240710-ens21x-v3-2-4e3fbcf2a7fb@thegoodpenguin.co.uk>
Date: Wed, 10 Jul 2024 14:24:05 +0100
From: Joshua Felmeden <jfelmeden@...goodpenguin.co.uk>
To: Jonathan Cameron <jic23@...nel.org>, 
 Lars-Peter Clausen <lars@...afoo.de>, Rob Herring <robh@...nel.org>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, 
 Joshua Felmeden <jfelmeden@...goodpenguin.co.uk>
Cc: linux-iio@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org
Subject: [PATCH v3 2/2] iio: humidity: Add support for ENS21x

Add support for ENS210/ENS210A/ENS211/ENS212/ENS213A/ENS215.

The ENS21x is a family of temperature and relative humidity sensors with
accuracies tailored to the needs of specific applications.

Signed-off-by: Joshua Felmeden <jfelmeden@...goodpenguin.co.uk>
---
 drivers/iio/humidity/Kconfig  |  11 ++
 drivers/iio/humidity/Makefile |   1 +
 drivers/iio/humidity/ens21x.c | 346 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 358 insertions(+)

diff --git a/drivers/iio/humidity/Kconfig b/drivers/iio/humidity/Kconfig
index b15b7a3b66d5..ff62abf730d1 100644
--- a/drivers/iio/humidity/Kconfig
+++ b/drivers/iio/humidity/Kconfig
@@ -25,6 +25,17 @@ config DHT11
 	  Other sensors should work as well as long as they speak the
 	  same protocol.
 
+config ENS21X
+	tristate "ENS21X temperature and humidity sensor"
+	depends on I2C
+	help
+	  Say yes here to get support for the ScioSense ENS21X family of
+	  humidity and temperature sensors.
+
+	  This driver can also be built as a module. If so, the module will be
+	  called ens21x.
+
+
 config HDC100X
 	tristate "TI HDC100x relative humidity and temperature sensor"
 	depends on I2C
diff --git a/drivers/iio/humidity/Makefile b/drivers/iio/humidity/Makefile
index 5fbeef299f61..26590d06d11f 100644
--- a/drivers/iio/humidity/Makefile
+++ b/drivers/iio/humidity/Makefile
@@ -5,6 +5,7 @@
 
 obj-$(CONFIG_AM2315) += am2315.o
 obj-$(CONFIG_DHT11) += dht11.o
+obj-$(CONFIG_ENS21X) += ens21x.o
 obj-$(CONFIG_HDC100X) += hdc100x.o
 obj-$(CONFIG_HDC2010) += hdc2010.o
 obj-$(CONFIG_HDC3020) += hdc3020.o
diff --git a/drivers/iio/humidity/ens21x.c b/drivers/iio/humidity/ens21x.c
new file mode 100644
index 000000000000..7b2e279d1559
--- /dev/null
+++ b/drivers/iio/humidity/ens21x.c
@@ -0,0 +1,346 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * ens21x.c - Support for ScioSense ens21x
+ *           temperature & humidity sensor
+ *
+ * (7-bit I2C slave address 0x43 ENS210)
+ * (7-bit I2C slave address 0x43 ENS210A)
+ * (7-bit I2C slave address 0x44 ENS211)
+ * (7-bit I2C slave address 0x45 ENS212)
+ * (7-bit I2C slave address 0x46 ENS213A)
+ * (7-bit I2C slave address 0x47 ENS215)
+ *
+ * Datasheet:
+ *  https://www.sciosense.com/wp-content/uploads/2024/04/ENS21x-Datasheet.pdf
+ *  https://www.sciosense.com/wp-content/uploads/2023/12/ENS210-Datasheet.pdf
+ */
+
+#include <linux/types.h>
+#include <linux/i2c.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/crc7.h>
+
+/* register definitions */
+#define ENS21X_REG_PART_ID		0x00
+#define ENS21X_REG_DIE_REV		0x02
+#define ENS21X_REG_UID			0x04
+#define ENS21X_REG_SYS_CTRL		0x10
+#define ENS21X_REG_SYS_STAT		0x11
+#define ENS21X_REG_SENS_RUN		0x21
+#define ENS21X_REG_SENS_START		0x22
+#define ENS21X_REG_SENS_STOP		0x23
+#define ENS21X_REG_SENS_STAT		0x24
+#define ENS21X_REG_T_VAL		0x30
+#define ENS21X_REG_H_VAL		0x33
+
+/* value definitions */
+#define ENS21X_SENS_START_T_START		BIT(0)
+#define ENS21X_SENS_START_H_START		BIT(1)
+
+#define ENS21X_SENS_STAT_T_ACTIVE		BIT(0)
+#define ENS21X_SENS_STAT_H_ACTIVE		BIT(1)
+
+#define ENS21X_SYS_CTRL_LOW_POWER_ENABLE	BIT(0)
+#define ENS21X_SYS_CTRL_SYS_RESET		BIT(7)
+
+#define ENS21X_SYS_STAT_SYS_ACTIVE		BIT(0)
+
+/* magic constants */
+#define ENS21X_CONST_TEMP_SCALE_INT 15 /* integer part of temperature scale (1/64) */
+#define ENS21X_CONST_TEMP_SCALE_DEC 625000 /* decimal part of temperature scale */
+#define ENS21X_CONST_HUM_SCALE_INT 1 /* integer part of humidity scale (1/512) */
+#define ENS21X_CONST_HUM_SCALE_DEC 953125 /* decimal part of humidity scale */
+#define ENS21X_CONST_TEMP_OFFSET_INT -17481 /* temperature offset (64 * -273.15) */
+#define ENS21X_CONST_TEMP_OFFSET_DEC 600000 /* decimal part of offset */
+#define ENS210_CONST_CONVERSION_TIME 130
+#define ENS212_CONST_CONVERSION_TIME 32
+#define ENS215_CONST_CONVERSION_TIME 132
+
+static const struct of_device_id ens21x_of_match[];
+
+struct ens21x_dev {
+	struct i2c_client *client;
+	struct mutex lock;
+	int part_id;
+};
+
+enum ens21x_partnumber {
+	ENS210	= 0x0210,
+	ENS210A	= 0xa210,
+	ENS211	= 0x0211,
+	ENS212	= 0x0212,
+	ENS213A	= 0xa213,
+	ENS215	= 0x0215,
+};
+
+/* calculate 17-bit crc7 */
+static u8 ens21x_crc7(u32 val)
+{
+	u32 val_be = (htonl(val & 0x1ffff) >> 0x8);
+
+	return crc7_be(0xde, (u8 *)&val_be, 3) >> 1;
+}
+
+static int ens21x_get_measurement(struct iio_dev *indio_dev, bool temp, int *val)
+{
+	u32 regval, regval_le;
+	int ret, tries;
+	struct ens21x_dev *dev_data = iio_priv(indio_dev);
+
+	/* assert read */
+	i2c_smbus_write_byte_data(dev_data->client, ENS21X_REG_SENS_START,
+				  temp ? ENS21X_SENS_START_T_START :
+					 ENS21X_SENS_START_H_START);
+
+	/* wait for conversion to be ready */
+	switch (dev_data->part_id) {
+	case ENS210:
+	case ENS210A:
+		msleep(ENS210_CONST_CONVERSION_TIME);
+		break;
+	case ENS211:
+	case ENS212:
+		msleep(ENS212_CONST_CONVERSION_TIME);
+		break;
+	case ENS213A:
+	case ENS215:
+		msleep(ENS215_CONST_CONVERSION_TIME);
+		break;
+	default:
+		dev_err(&dev_data->client->dev, "unrecognised device");
+		return -ENODEV;
+	}
+
+	tries = 10;
+	while (tries-- > 0) {
+		usleep_range(4000, 5000);
+		ret = i2c_smbus_read_byte_data(dev_data->client,
+					       ENS21X_REG_SENS_STAT);
+		if (ret < 0)
+			continue;
+		if (!(ret & (temp ? ENS21X_SENS_STAT_T_ACTIVE :
+				    ENS21X_SENS_STAT_H_ACTIVE)))
+			break;
+	}
+	if (tries < 0) {
+		dev_err(&indio_dev->dev, "timeout waiting for sensor reading\n");
+		return -EIO;
+	}
+
+	/* perform read */
+	ret = i2c_smbus_read_i2c_block_data(
+		dev_data->client, temp ? ENS21X_REG_T_VAL : ENS21X_REG_H_VAL, 3,
+		(u8 *)&regval_le);
+	if (ret < 0) {
+		dev_err(&dev_data->client->dev, "failed to read register");
+		return -EIO;
+	} else if (ret == 3) {
+		regval = le32_to_cpu(regval_le);
+		if (ens21x_crc7(regval) == ((regval >> 17) & 0x7f)) {
+			*val = regval & 0xffff;
+			return IIO_VAL_INT;
+		}
+		/* crc fail */
+		dev_err(&indio_dev->dev, "ens invalid crc\n");
+		return -EIO;
+	}
+
+	dev_err(&indio_dev->dev, "expected 3 bytes, received %d\n", ret);
+	return -EIO;
+}
+
+static int ens21x_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *channel, int *val,
+			   int *val2, long mask)
+{
+	struct ens21x_dev *dev_data = iio_priv(indio_dev);
+	int ret = -EINVAL;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		mutex_lock(&dev_data->lock);
+		ret = ens21x_get_measurement(
+			indio_dev, channel->type == IIO_TEMP, val);
+		mutex_unlock(&dev_data->lock);
+		break;
+	case IIO_CHAN_INFO_SCALE:
+		if (channel->type == IIO_TEMP) {
+			*val = ENS21X_CONST_TEMP_SCALE_INT;
+			*val2 = ENS21X_CONST_TEMP_SCALE_DEC;
+		} else {
+			*val = ENS21X_CONST_HUM_SCALE_INT;
+			*val2 = ENS21X_CONST_HUM_SCALE_DEC;
+		}
+		ret = IIO_VAL_INT_PLUS_MICRO;
+		break;
+	case IIO_CHAN_INFO_OFFSET:
+		if (channel->type == IIO_TEMP) {
+			*val = ENS21X_CONST_TEMP_OFFSET_INT;
+			*val2 = ENS21X_CONST_TEMP_OFFSET_DEC;
+			ret = IIO_VAL_INT_PLUS_MICRO;
+			break;
+		}
+		*val = 0;
+		ret =  IIO_VAL_INT;
+		break;
+	default:
+		break;
+	}
+	return ret;
+}
+
+static const struct iio_chan_spec ens21x_channels[] = {
+	/* Temperature channel */
+	{
+		.type = IIO_TEMP,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+				      BIT(IIO_CHAN_INFO_SCALE) |
+				      BIT(IIO_CHAN_INFO_OFFSET),
+	},
+	/* Humidity channel */
+	{
+		.type = IIO_HUMIDITYRELATIVE,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+				      BIT(IIO_CHAN_INFO_SCALE) |
+				      BIT(IIO_CHAN_INFO_OFFSET),
+	}
+};
+
+static const struct iio_info ens21x_info = {
+	.read_raw = ens21x_read_raw,
+};
+
+static int ens21x_probe(struct i2c_client *client)
+{
+	const struct i2c_device_id *id = i2c_client_get_device_id(client);
+	const struct of_device_id *match;
+	struct ens21x_dev *dev_data;
+	struct iio_dev *indio_dev;
+	uint16_t part_id_le, part_id;
+	int ret, tries;
+
+	if (!i2c_check_functionality(client->adapter,
+			I2C_FUNC_SMBUS_WRITE_BYTE_DATA |
+			I2C_FUNC_SMBUS_WRITE_BYTE |
+			I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
+		dev_err(&client->dev,
+			"adapter does not support some i2c transactions\n");
+		return -EOPNOTSUPP;
+	}
+
+	match = i2c_of_match_device(ens21x_of_match, client);
+	if (!match)
+		return -ENODEV;
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*dev_data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	dev_data = iio_priv(indio_dev);
+	i2c_set_clientdata(client, indio_dev);
+	dev_data->client = client;
+	mutex_init(&dev_data->lock);
+
+	/* reset device */
+	ret = i2c_smbus_write_byte_data(client, ENS21X_REG_SYS_CTRL,
+					ENS21X_SYS_CTRL_SYS_RESET);
+	if (ret)
+		return ret;
+
+	/* wait for device to become active */
+	usleep_range(4000, 5000);
+
+	/* disable low power mode */
+	ret = i2c_smbus_write_byte_data(client, ENS21X_REG_SYS_CTRL, 0x00);
+	if (ret)
+		return ret;
+
+	/* wait for device to become active */
+	tries = 10;
+	while (tries-- > 0) {
+		msleep(20);
+		ret = i2c_smbus_read_byte_data(client, ENS21X_REG_SYS_STAT);
+		if (ret < 0)
+			return ret;
+		if (ret & ENS21X_SYS_STAT_SYS_ACTIVE)
+			break;
+	}
+	if (tries < 0) {
+		dev_err(&client->dev,
+			"timeout waiting for ens21x to become active\n");
+		return -EIO;
+	}
+
+	/* get part_id */
+	part_id_le = i2c_smbus_read_word_data(client, ENS21X_REG_PART_ID);
+	if (part_id_le < 0)
+		return part_id_le;
+	part_id = le16_to_cpu(part_id_le);
+
+	if (part_id != id->driver_data) {
+		dev_err(&client->dev,
+			"Part ID does not match (0x%04x != 0x%04lx)\n", part_id,
+			id->driver_data);
+		return -ENODEV;
+	}
+
+	/* reenable low power */
+	ret = i2c_smbus_write_byte_data(client, ENS21X_REG_SYS_CTRL,
+					ENS21X_SYS_CTRL_LOW_POWER_ENABLE);
+	if (ret)
+		return ret;
+
+	dev_data->part_id = part_id;
+
+	indio_dev->name = id->name;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = ens21x_channels;
+	indio_dev->num_channels = ARRAY_SIZE(ens21x_channels);
+	indio_dev->info = &ens21x_info;
+
+	return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+
+static const struct of_device_id ens21x_of_match[] = {
+	{ .compatible = "sciosense,ens210", .data = (void *)ENS210},
+	{ .compatible = "sciosense,ens210a", .data = (void *)ENS210A },
+	{ .compatible = "sciosense,ens211", .data = (void *)ENS211},
+	{ .compatible = "sciosense,ens212", .data = (void *)ENS212},
+	{ .compatible = "sciosense,ens213a", .data = (void *)ENS213A },
+	{ .compatible = "sciosense,ens215", .data = (void *)ENS215},
+	{},
+};
+MODULE_DEVICE_TABLE(of, ens21x_of_match);
+
+static const struct i2c_device_id ens21x_id[] = {
+	{"ens210", ENS210},
+	{"ens210a", ENS210A},
+	{"ens211", ENS211},
+	{"ens212", ENS212},
+	{"ens213a", ENS213A},
+	{"ens215", ENS215},
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, ens21x_id);
+
+static struct i2c_driver ens21x_driver = {
+	.probe = ens21x_probe,
+	.id_table = ens21x_id,
+	.driver = {
+		.name = "ens21x",
+		.of_match_table = ens21x_of_match,
+	},
+};
+
+module_i2c_driver(ens21x_driver);
+
+MODULE_DESCRIPTION("ScioSense ENS21x temperature and humidity sensor driver");
+MODULE_AUTHOR("Joshua Felmeden <jfelmeden@...goodpenguin.co.uk>");
+MODULE_LICENSE("GPL");
+

-- 
2.39.2

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