iio: chemical: Add support for Bosch BME680 sensor

Bosch BME680 is a 4-in-1 sensor with temperature, pressure, humidity
and gas sensing capability. It supports both I2C and SPI communication
protocol for effective data communication.

The device supports two modes:

1. Sleep mode
2. Forced mode

The measurements only takes place when forced mode is triggered and a
single TPHG cycle is performed by the sensor. The sensor automatically
goes to sleep after afterwards.

The device has various calibration constants/parameters programmed into
devices' non-volatile memory(NVM) during production and can't be altered
by the user. These constants are used in the compensation functions to
get the required compensated readings along with the raw data. The
compensation functions/algorithms are provided by Bosch Sensortec GmbH
via their API[1]. As these don't change during the measurement cycle,
therefore we read and store them at the probe. The default configs
supplied by Bosch are also set at probe.

0-day tested with build success.

GSoC-2018: https://summerofcode.withgoogle.com/projects/#6691473790074880
Mentor: Daniel Baluta
[1] https://github.com/BoschSensortec/BME680_driver
Datasheet:
https://ae-bst.resource.bosch.com/media/_tech/media/datasheets/BST-BME680-DS001-00.pdf

Note from Jonathan: The compensation functions are 'interesting' and
could do with a tidy up in future.  However, they work so we can leave that
for another day.

Cc: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Himanshu Jha <himanshujha199640@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

1 files changed, 85 insertions, 0 deletions

diff --git a/drivers/iio/chemical/bme680_i2c.c b/drivers/iio/chemical/bme680_i2c.c
new file mode 100644
index 000000000000..06d4be539d2e
--- /dev/null
+++ b/drivers/iio/chemical/bme680_i2c.c
@@ -0,0 +1,85 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * BME680 - I2C Driver
+ *
+ * Copyright (C) 2018 Himanshu Jha <himanshujha199640@gmail.com>
+ *
+ * 7-Bit I2C slave address is:
+ *	- 0x76 if SDO is pulled to GND
+ *	- 0x77 if SDO is pulled to VDDIO
+ *
+ * Note: SDO pin cannot be left floating otherwise I2C address
+ *	 will be undefined.
+ */
+#include <linux/acpi.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#include "bme680.h"
+
+static int bme680_i2c_probe(struct i2c_client *client,
+			    const struct i2c_device_id *id)
+{
+	struct regmap *regmap;
+	const char *name = NULL;
+	unsigned int val;
+	int ret;
+
+	regmap = devm_regmap_init_i2c(client, &bme680_regmap_config);
+	if (IS_ERR(regmap)) {
+		dev_err(&client->dev, "Failed to register i2c regmap %d\n",
+				(int)PTR_ERR(regmap));
+		return PTR_ERR(regmap);
+	}
+
+	ret = regmap_write(regmap, BME680_REG_SOFT_RESET_I2C,
+			   BME680_CMD_SOFTRESET);
+	if (ret < 0) {
+		dev_err(&client->dev, "Failed to reset chip\n");
+		return ret;
+	}
+
+	ret = regmap_read(regmap, BME680_REG_CHIP_I2C_ID, &val);
+	if (ret < 0) {
+		dev_err(&client->dev, "Error reading I2C chip ID\n");
+		return ret;
+	}
+
+	if (val != BME680_CHIP_ID_VAL) {
+		dev_err(&client->dev, "Wrong chip ID, got %x expected %x\n",
+				val, BME680_CHIP_ID_VAL);
+		return -ENODEV;
+	}
+
+	if (id)
+		name = id->name;
+
+	return bme680_core_probe(&client->dev, regmap, name);
+}
+
+static const struct i2c_device_id bme680_i2c_id[] = {
+	{"bme680", 0},
+	{},
+};
+MODULE_DEVICE_TABLE(i2c, bme680_i2c_id);
+
+static const struct acpi_device_id bme680_acpi_match[] = {
+	{"BME0680", 0},
+	{},
+};
+MODULE_DEVICE_TABLE(acpi, bme680_acpi_match);
+
+static struct i2c_driver bme680_i2c_driver = {
+	.driver = {
+		.name			= "bme680_i2c",
+		.acpi_match_table       = ACPI_PTR(bme680_acpi_match),
+	},
+	.probe = bme680_i2c_probe,
+	.id_table = bme680_i2c_id,
+};
+module_i2c_driver(bme680_i2c_driver);
+
+MODULE_AUTHOR("Himanshu Jha <himanshujha199640@gmail.com>");
+MODULE_DESCRIPTION("BME680 I2C driver");
+MODULE_LICENSE("GPL v2");