iio: chemical: scd30: add core driver

Add Sensirion SCD30 carbon dioxide core driver.
Signed-off-by: Tomasz Duszynski <tomasz.duszynski@octakon.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/ABI/testing/sysfs-bus-iio-scd30

+What:		/sys/bus/iio/devices/iio:deviceX/calibration_auto_enable
+Date:		June 2020
+KernelVersion:	5.8
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Contaminants build-up in the measurement chamber or optical
+		elements deterioration leads to sensor drift.
+
+		One can compensate for sensor drift by using automatic self
+		calibration procedure (asc).
+
+		Writing 1 or 0 to this attribute will respectively activate or
+		deactivate asc.
+
+		Upon reading current asc status is returned.
+
+What:		/sys/bus/iio/devices/iio:deviceX/calibration_forced_value
+Date:		June 2020
+KernelVersion:	5.8
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Contaminants build-up in the measurement chamber or optical
+		elements deterioration leads to sensor drift.
+
+		One can compensate for sensor drift by using forced
+		recalibration (frc). This is useful in case there's known
+		co2 reference available nearby the sensor.
+
+		Picking value from the range [400 1 2000] and writing it to the
+		sensor will set frc.
+
+		Upon reading current frc value is returned. Note that after
+		power cycling default value (i.e 400) is returned even though
+		internally sensor had recalibrated itself.

MAINTAINERS

@@ -15351,6 +15351,12 @@ S:	Maintained
 F:	drivers/misc/phantom.c
 F:	include/uapi/linux/phantom.h
 
+SENSIRION SCD30 CARBON DIOXIDE SENSOR DRIVER
+M:	Tomasz Duszynski <tomasz.duszynski@octakon.com>
+S:	Maintained
+F:	drivers/iio/chemical/scd30.h
+F:	drivers/iio/chemical/scd30_core.c
+
 SENSIRION SPS30 AIR POLLUTION SENSOR DRIVER
 M:	Tomasz Duszynski <tduszyns@gmail.com>
 S:	Maintained

drivers/iio/chemical/Kconfig

@@ -85,6 +85,17 @@ config PMS7003
 	  To compile this driver as a module, choose M here: the module will
 	  be called pms7003.
 
+config SCD30_CORE
+	tristate "SCD30 carbon dioxide sensor driver"
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
+	help
+	  Say Y here to build support for the Sensirion SCD30 sensor with carbon
+	  dioxide, relative humidity and temperature sensing capabilities.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called scd30_core.
+
 config SENSIRION_SGP30
 	tristate "Sensirion SGPxx gas sensors"
 	depends on I2C

drivers/iio/chemical/Makefile

@@ -12,6 +12,7 @@ obj-$(CONFIG_BME680_SPI) += bme680_spi.o
 obj-$(CONFIG_CCS811)		+= ccs811.o
 obj-$(CONFIG_IAQCORE)		+= ams-iaq-core.o
 obj-$(CONFIG_PMS7003) += pms7003.o
+obj-$(CONFIG_SCD30_CORE) += scd30_core.o
 obj-$(CONFIG_SENSIRION_SGP30)	+= sgp30.o
 obj-$(CONFIG_SPS30) += sps30.o
 obj-$(CONFIG_VZ89X)		+= vz89x.o

drivers/iio/chemical/scd30.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _SCD30_H
+#define _SCD30_H
+
+#include <linux/completion.h>
+#include <linux/device.h>
+#include <linux/mutex.h>
+#include <linux/pm.h>
+#include <linux/regulator/consumer.h>
+#include <linux/types.h>
+
+struct scd30_state;
+
+enum scd30_cmd {
+	/* start continuous measurement with pressure compensation */
+	CMD_START_MEAS,
+	/* stop continuous measurement */
+	CMD_STOP_MEAS,
+	/* set/get measurement interval */
+	CMD_MEAS_INTERVAL,
+	/* check whether new measurement is ready */
+	CMD_MEAS_READY,
+	/* get measurement */
+	CMD_READ_MEAS,
+	/* turn on/off automatic self calibration */
+	CMD_ASC,
+	/* set/get forced recalibration value */
+	CMD_FRC,
+	/* set/get temperature offset */
+	CMD_TEMP_OFFSET,
+	/* get firmware version */
+	CMD_FW_VERSION,
+	/* reset sensor */
+	CMD_RESET,
+	/*
+	 * Command for altitude compensation was omitted intentionally because
+	 * the same can be achieved by means of CMD_START_MEAS which takes
+	 * pressure above the sea level as an argument.
+	 */
+};
+
+#define SCD30_MEAS_COUNT 3
+
+typedef int (*scd30_command_t)(struct scd30_state *state, enum scd30_cmd cmd, u16 arg,
+			       void *response, int size);
+
+struct scd30_state {
+	/* serialize access to the device */
+	struct mutex lock;
+	struct device *dev;
+	struct regulator *vdd;
+	struct completion meas_ready;
+	/*
+	 * priv pointer is solely for serdev driver private data. We keep it
+	 * here because driver_data inside dev has been already used for iio and
+	 * struct serdev_device doesn't have one.
+	 */
+	void *priv;
+	int irq;
+	/*
+	 * no way to retrieve current ambient pressure compensation value from
+	 * the sensor so keep one around
+	 */
+	u16 pressure_comp;
+	u16 meas_interval;
+	int meas[SCD30_MEAS_COUNT];
+
+	scd30_command_t command;
+};
+
+int scd30_suspend(struct device *dev);
+int scd30_resume(struct device *dev);
+
+static __maybe_unused SIMPLE_DEV_PM_OPS(scd30_pm_ops, scd30_suspend, scd30_resume);
+
+int scd30_probe(struct device *dev, int irq, const char *name, void *priv, scd30_command_t command);
+
+#endif