path: root/drivers/iio/chemical/scd4x.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Sensirion SCD4X carbon dioxide sensor i2c driver
 *
 * Copyright (C) 2021 Protonic Holland
 * Author: Roan van Dijk <roan@protonic.nl>
 *
 * I2C slave address: 0x62
 *
 * Datasheets:
 * https://www.sensirion.com/file/datasheet_scd4x
 */

#include <linux/unaligned.h>
#include <linux/crc8.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/i2c.h>
#include <linux/iio/buffer.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <linux/iio/trigger.h>
#include <linux/iio/trigger_consumer.h>
#include <linux/iio/triggered_buffer.h>
#include <linux/iio/types.h>
#include <linux/kernel.h>
#include <linux/mutex.h>
#include <linux/string.h>
#include <linux/sysfs.h>
#include <linux/types.h>

#define SCD4X_CRC8_POLYNOMIAL 0x31
#define SCD4X_TIMEOUT_ERR 1000
#define SCD4X_READ_BUF_SIZE 9
#define SCD4X_COMMAND_BUF_SIZE 2
#define SCD4X_WRITE_BUF_SIZE 5
#define SCD4X_FRC_MIN_PPM 0
#define SCD4X_FRC_MAX_PPM 2000
#define SCD4X_PRESSURE_COMP_MIN_MBAR 700
#define SCD4X_PRESSURE_COMP_MAX_MBAR 1200
#define SCD4X_READY_MASK 0x01

/*Commands SCD4X*/
enum scd4x_cmd {
	CMD_START_MEAS          = 0x21b1,
	CMD_READ_MEAS           = 0xec05,
	CMD_STOP_MEAS           = 0x3f86,
	CMD_SET_TEMP_OFFSET     = 0x241d,
	CMD_GET_TEMP_OFFSET     = 0x2318,
	CMD_SET_AMB_PRESSURE	= 0xe000,
	CMD_GET_AMB_PRESSURE	= 0xe000,
	CMD_FRC                 = 0x362f,
	CMD_SET_ASC             = 0x2416,
	CMD_GET_ASC             = 0x2313,
	CMD_GET_DATA_READY      = 0xe4b8,
};

enum scd4x_channel_idx {
	SCD4X_CO2,
	SCD4X_TEMP,
	SCD4X_HR,
};

struct scd4x_state {
	struct i2c_client *client;
	/* maintain access to device, to prevent concurrent reads/writes */
	struct mutex lock;
	struct regulator *vdd;
};

DECLARE_CRC8_TABLE(scd4x_crc8_table);

static int scd4x_i2c_xfer(struct scd4x_state *state, char *txbuf, int txsize,
				char *rxbuf, int rxsize)
{
	struct i2c_client *client = state->client;
	int ret;

	ret = i2c_master_send(client, txbuf, txsize);

	if (ret < 0)
		return ret;
	if (ret != txsize)
		return -EIO;

	if (rxsize == 0)
		return 0;

	ret = i2c_master_recv(client, rxbuf, rxsize);
	if (ret < 0)
		return ret;
	if (ret != rxsize)
		return -EIO;

	return 0;
}

static int scd4x_send_command(struct scd4x_state *state, enum scd4x_cmd cmd)
{
	char buf[SCD4X_COMMAND_BUF_SIZE];
	int ret;

	/*
	 * Measurement needs to be stopped before sending commands.
	 * Except stop and start command.
	 */
	if ((cmd != CMD_STOP_MEAS) && (cmd != CMD_START_MEAS)) {

		ret = scd4x_send_command(state, CMD_STOP_MEAS);
		if (ret)
			return ret;

		/* execution time for stopping measurement */
		msleep_interruptible(500);
	}

	put_unaligned_be16(cmd, buf);
	ret = scd4x_i2c_xfer(state, buf, 2, buf, 0);
	if (ret)
		return ret;

	if ((cmd != CMD_STOP_MEAS) && (cmd != CMD_START_MEAS)) {
		ret = scd4x_send_command(state, CMD_START_MEAS);
		if (ret)
			return ret;
	}

	return 0;
}

static int scd4x_read(struct scd4x_state *state, enum scd4x_cmd cmd,
			void *response, int response_sz)
{
	struct i2c_client *client = state->client;
	char buf[SCD4X_READ_BUF_SIZE];
	char *rsp = response;
	int i, ret;
	char crc;

	/*
	 * Measurement needs to be stopped before sending commands.
	 * Except for reading measurement and data ready command.
	 */
	if ((cmd != CMD_GET_DATA_READY) && (cmd != CMD_READ_MEAS) &&
	    (cmd != CMD_GET_AMB_PRESSURE)) {
		ret = scd4x_send_command(state, CMD_STOP_MEAS);
		if (ret)
			return ret;

		/* execution time for stopping measurement */
		msleep_interruptible(500);
	}

	/* CRC byte for every 2 bytes of data */
	response_sz += response_sz / 2;

	put_unaligned_be16(cmd, buf);
	ret = scd4x_i2c_xfer(state, buf, 2, buf, response_sz);
	if (ret)
		return ret;

	for (i = 0; i < response_sz; i += 3) {
		crc = crc8(scd4x_crc8_table, buf + i, 2, CRC8_INIT_VALUE);
		if (crc != buf[i + 2]) {
			dev_err(&client->dev, "CRC error\n");
			return -EIO;
		}

		*rsp++ = buf[i];
		*rsp++ = buf[i + 1];
	}

	/* start measurement */
	if ((cmd != CMD_GET_DATA_READY) && (cmd != CMD_READ_MEAS) &&
	    (cmd != CMD_GET_AMB_PRESSURE)) {
		ret = scd4x_send_command(state, CMD_START_MEAS);
		if (ret)
			return ret;
	}

	return 0;
}

static int scd4x_write(struct scd4x_state *state, enum scd4x_cmd cmd, uint16_t arg)
{
	char buf[SCD4X_WRITE_BUF_SIZE];
	int ret;
	char crc;

	put_unaligned_be16(cmd, buf);
	put_unaligned_be16(arg, buf + 2);

	crc = crc8(scd4x_crc8_table, buf + 2, 2, CRC8_INIT_VALUE);
	buf[4] = crc;

	/* measurement needs to be stopped before sending commands */
	if (cmd != CMD_SET_AMB_PRESSURE) {
		ret = scd4x_send_command(state, CMD_STOP_MEAS);
		if (ret)
			return ret;
	}

	/* execution time */
	msleep_interruptible(500);

	ret = scd4x_i2c_xfer(state, buf, SCD4X_WRITE_BUF_SIZE, buf, 0);
	if (ret)
		return ret;

	/* start measurement, except for forced calibration command */
	if ((cmd != CMD_FRC) && (cmd != CMD_SET_AMB_PRESSURE)) {
		ret = scd4x_send_command(state, CMD_START_MEAS);
		if (ret)
			return ret;
	}

	return 0;
}

static int scd4x_write_and_fetch(struct scd4x_state *state, enum scd4x_cmd cmd,
				uint16_t arg, void *response, int response_sz)
{
	struct i2c_client *client = state->client;
	char buf[SCD4X_READ_BUF_SIZE];
	char *rsp = response;
	int i, ret;
	char crc;

	ret = scd4x_write(state, CMD_FRC, arg);
	if (ret)
		goto err;

	/* execution time */
	msleep_interruptible(400);

	/* CRC byte for every 2 bytes of data */
	response_sz += response_sz / 2;

	ret = i2c_master_recv(client, buf, response_sz);
	if (ret < 0)
		goto err;
	if (ret != response_sz) {
		ret = -EIO;
		goto err;
	}

	for (i = 0; i < response_sz; i += 3) {
		crc = crc8(scd4x_crc8_table, buf + i, 2, CRC8_INIT_VALUE);
		if (crc != buf[i + 2]) {
			dev_err(&client->dev, "CRC error\n");
			ret = -EIO;
			goto err;
		}

		*rsp++ = buf[i];
		*rsp++ = buf[i + 1];
	}

	return scd4x_send_command(state, CMD_START_MEAS);

err:
	/*
	 * on error try to start the measurement,
	 * puts sensor back into continuous measurement
	 */
	scd4x_send_command(state, CMD_START_MEAS);

	return ret;
}

static int scd4x_read_meas(struct scd4x_state *state, uint16_t *meas)
{
	int i, ret;
	__be16 buf[3];

	ret = scd4x_read(state, CMD_READ_MEAS, buf, sizeof(buf));
	if (ret)
		return ret;

	for (i = 0; i < ARRAY_SIZE(buf); i++)
		meas[i] = be16_to_cpu(buf[