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

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

drivers/iio/chemical/Kconfig

@@ -21,6 +21,31 @@ config ATLAS_PH_SENSOR
 	 To compile this driver as module, choose M here: the
 	 module will be called atlas-ph-sensor.
 
+config BME680
+	tristate "Bosch Sensortec BME680 sensor driver"
+	depends on (I2C || SPI)
+	select REGMAP
+	select BME680_I2C if (I2C)
+	select BME680_SPI if (SPI)
+	help
+	  Say yes here to build support for Bosch Sensortec BME680 sensor with
+	  temperature, pressure, humidity and gas sensing capability.
+
+	  This driver can also be built as a module. If so, the module for I2C
+	  would be called bme680_i2c and bme680_spi for SPI support.
+
+config BME680_I2C
+	tristate
+	depends on BME680
+	depends on I2C
+	select REGMAP_I2C
+
+config BME680_SPI
+	tristate
+	depends on BME680
+	depends on SPI
+	select REGMAP_SPI
+
 config CCS811
 	tristate "AMS CCS811 VOC sensor"
 	depends on I2C

drivers/iio/chemical/Makefile

@@ -4,6 +4,9 @@
 
 # When adding new entries keep the list in alphabetical order
 obj-$(CONFIG_ATLAS_PH_SENSOR)	+= atlas-ph-sensor.o
+obj-$(CONFIG_BME680) += bme680_core.o
+obj-$(CONFIG_BME680_I2C) += bme680_i2c.o
+obj-$(CONFIG_BME680_SPI) += bme680_spi.o
 obj-$(CONFIG_CCS811)		+= ccs811.o
 obj-$(CONFIG_IAQCORE)		+= ams-iaq-core.o
 obj-$(CONFIG_VZ89X)		+= vz89x.o

drivers/iio/chemical/bme680.h

@@ -0,0 +1,99 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef BME680_H_
+#define BME680_H_
+
+#define BME680_REG_CHIP_I2C_ID			0xD0
+#define BME680_REG_CHIP_SPI_ID			0x50
+#define BME680_CHIP_ID_VAL			0x61
+#define BME680_REG_SOFT_RESET			0xE0
+#define BME680_CMD_SOFTRESET			0xB6
+#define BME680_REG_STATUS			0x73
+#define   BME680_SPI_MEM_PAGE_BIT		BIT(4)
+#define   BME680_SPI_MEM_PAGE_1_VAL		1
+
+#define BME680_OSRS_TEMP_X(osrs_t)		((osrs_t) << 5)
+#define BME680_OSRS_PRESS_X(osrs_p)		((osrs_p) << 2)
+#define BME680_OSRS_HUMID_X(osrs_h)		((osrs_h) << 0)
+
+#define BME680_REG_TEMP_MSB			0x22
+#define BME680_REG_PRESS_MSB			0x1F
+#define BM6880_REG_HUMIDITY_MSB			0x25
+#define BME680_REG_GAS_MSB			0x2A
+#define BME680_REG_GAS_R_LSB			0x2B
+#define   BME680_GAS_STAB_BIT			BIT(4)
+
+#define BME680_REG_CTRL_HUMIDITY		0x72
+#define   BME680_OSRS_HUMIDITY_MASK		GENMASK(2, 0)
+
+#define BME680_REG_CTRL_MEAS			0x74
+#define   BME680_OSRS_TEMP_MASK			GENMASK(7, 5)
+#define   BME680_OSRS_PRESS_MASK		GENMASK(4, 2)
+#define   BME680_MODE_MASK			GENMASK(1, 0)
+
+#define BME680_MODE_FORCED			BIT(0)
+#define BME680_MODE_SLEEP			0
+
+#define BME680_REG_CONFIG			0x75
+#define   BME680_FILTER_MASK			GENMASK(4, 2)
+#define   BME680_FILTER_COEFF			BIT(1)
+
+/* TEMP/PRESS/HUMID reading skipped */
+#define BME680_MEAS_SKIPPED			0x8000
+
+#define BME680_MAX_OVERFLOW_VAL			0x40000000
+#define BME680_HUM_REG_SHIFT_VAL		4
+#define BME680_BIT_H1_DATA_MSK			0x0F
+
+#define BME680_REG_RES_HEAT_RANGE		0x02
+#define BME680_RHRANGE_MSK			0x30
+#define BME680_REG_RES_HEAT_VAL			0x00
+#define BME680_REG_RANGE_SW_ERR			0x04
+#define BME680_RSERROR_MSK			0xF0
+#define BME680_REG_RES_HEAT_0			0x5A
+#define BME680_REG_GAS_WAIT_0			0x64
+#define BME680_GAS_RANGE_MASK			0x0F
+#define BME680_ADC_GAS_RES_SHIFT		6
+#define BME680_AMB_TEMP				25
+
+#define BME680_REG_CTRL_GAS_1			0x71
+#define   BME680_RUN_GAS_MASK			BIT(4)
+#define   BME680_NB_CONV_MASK			GENMASK(3, 0)
+#define	BME680_RUN_GAS_EN			BIT(4)
+#define BME680_NB_CONV_0			0
+
+#define BME680_REG_MEAS_STAT_0			0x1D
+#define   BME680_GAS_MEAS_BIT			BIT(6)
+
+/* Calibration Parameters */
+#define BME680_T2_LSB_REG	0x8A
+#define BME680_T3_REG		0x8C
+#define BME680_P1_LSB_REG	0x8E
+#define BME680_P2_LSB_REG	0x90
+#define BME680_P3_REG		0x92
+#define BME680_P4_LSB_REG	0x94
+#define BME680_P5_LSB_REG	0x96
+#define BME680_P7_REG		0x98
+#define BME680_P6_REG		0x99
+#define BME680_P8_LSB_REG	0x9C
+#define BME680_P9_LSB_REG	0x9E
+#define BME680_P10_REG		0xA0
+#define BME680_H2_LSB_REG	0xE2
+#define BME680_H2_MSB_REG	0xE1
+#define BME680_H1_MSB_REG	0xE3
+#define BME680_H1_LSB_REG	0xE2
+#define BME680_H3_REG		0xE4
+#define BME680_H4_REG		0xE5
+#define BME680_H5_REG		0xE6
+#define BME680_H6_REG		0xE7
+#define BME680_H7_REG		0xE8
+#define BME680_T1_LSB_REG	0xE9
+#define BME680_GH2_LSB_REG	0xEB
+#define BME680_GH1_REG		0xED
+#define BME680_GH3_REG		0xEE
+
+extern const struct regmap_config bme680_regmap_config;
+
+int bme680_core_probe(struct device *dev, struct regmap *regmap,
+		      const char *name);
+
+#endif  /* BME680_H_ */