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, 125 insertions, 0 deletions

diff --git a/drivers/iio/chemical/bme680_spi.c b/drivers/iio/chemical/bme680_spi.c
new file mode 100644
index 000000000000..c9fb05e8d0b9
--- /dev/null
+++ b/drivers/iio/chemical/bme680_spi.c
@@ -0,0 +1,125 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * BME680 - SPI Driver
+ *
+ * Copyright (C) 2018 Himanshu Jha <himanshujha199640@gmail.com>
+ */
+#include <linux/acpi.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/spi/spi.h>
+
+#include "bme680.h"
+
+static int bme680_regmap_spi_write(void *context, const void *data,
+				   size_t count)
+{
+	struct spi_device *spi = context;
+	u8 buf[2];
+
+	memcpy(buf, data, 2);
+	/*
+	 * The SPI register address (= full register address without bit 7)
+	 * and the write command (bit7 = RW = '0')
+	 */
+	buf[0] &= ~0x80;
+
+	return spi_write_then_read(spi, buf, 2, NULL, 0);
+}
+
+static int bme680_regmap_spi_read(void *context, const void *reg,
+				  size_t reg_size, void *val, size_t val_size)
+{
+	struct spi_device *spi = context;
+
+	return spi_write_then_read(spi, reg, reg_size, val, val_size);
+}
+
+static struct regmap_bus bme680_regmap_bus = {
+	.write = bme680_regmap_spi_write,
+	.read = bme680_regmap_spi_read,
+	.reg_format_endian_default = REGMAP_ENDIAN_BIG,
+	.val_format_endian_default = REGMAP_ENDIAN_BIG,
+};
+
+static int bme680_spi_probe(struct spi_device *spi)
+{
+	const struct spi_device_id *id = spi_get_device_id(spi);
+	struct regmap *regmap;
+	unsigned int val;
+	int ret;
+
+	spi->bits_per_word = 8;
+	ret = spi_setup(spi);
+	if (ret < 0) {
+		dev_err(&spi->dev, "spi_setup failed!\n");
+		return ret;
+	}
+
+	regmap = devm_regmap_init(&spi->dev, &bme680_regmap_bus,
+				  &spi->dev, &bme680_regmap_config);
+	if (IS_ERR(regmap)) {
+		dev_err(&spi->dev, "Failed to register spi regmap %d\n",
+				(int)PTR_ERR(regmap));
+		return PTR_ERR(regmap);
+	}
+
+	ret = regmap_write(regmap, BME680_REG_SOFT_RESET_SPI,
+			   BME680_CMD_SOFTRESET);
+	if (ret < 0) {
+		dev_err(&spi->dev, "Failed to reset chip\n");
+		return ret;
+	}
+
+	/* after power-on reset, Page 0(0x80-0xFF) of spi_mem_page is active */
+	ret = regmap_read(regmap, BME680_REG_CHIP_SPI_ID, &val);
+	if (ret < 0) {
+		dev_err(&spi->dev, "Error reading SPI chip ID\n");
+		return ret;
+	}
+
+	if (val != BME680_CHIP_ID_VAL) {
+		dev_err(&spi->dev, "Wrong chip ID, got %x expected %x\n",
+				val, BME680_CHIP_ID_VAL);
+		return -ENODEV;
+	}
+	/*
+	 * select Page 1 of spi_mem_page to enable access to
+	 * to registers from address 0x00 to 0x7F.
+	 */
+	ret = regmap_write_bits(regmap, BME680_REG_STATUS,
+				BME680_SPI_MEM_PAGE_BIT,
+				BME680_SPI_MEM_PAGE_1_VAL);
+	if (ret < 0) {
+		dev_err(&spi->dev, "failed to set page 1 of spi_mem_page\n");
+		return ret;
+	}
+
+	return bme680_core_probe(&spi->dev, regmap, id->name);
+}
+
+static const struct spi_device_id bme680_spi_id[] = {
+	{"bme680", 0},
+	{},
+};
+MODULE_DEVICE_TABLE(spi, bme680_spi_id);
+
+static const struct acpi_device_id bme680_acpi_match[] = {
+	{"BME0680", 0},
+	{},
+};
+MODULE_DEVICE_TABLE(acpi, bme680_acpi_match);
+
+static struct spi_driver bme680_spi_driver = {
+	.driver = {
+		.name			= "bme680_spi",
+		.acpi_match_table	= ACPI_PTR(bme680_acpi_match),
+	},
+	.probe = bme680_spi_probe,
+	.id_table = bme680_spi_id,
+};
+module_spi_driver(bme680_spi_driver);
+
+MODULE_AUTHOR("Himanshu Jha <himanshujha199640@gmail.com>");
+MODULE_DESCRIPTION("Bosch BME680 SPI driver");
+MODULE_LICENSE("GPL v2");