path: root/drivers/iio/chemical/sps30.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Sensirion SPS30 particulate matter sensor driver
 *
 * Copyright (c) Tomasz Duszynski <tduszyns@gmail.com>
 *
 * I2C slave address: 0x69
 */

#include <asm/unaligned.h>
#include <linux/crc8.h>
#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/iio/buffer.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <linux/iio/trigger_consumer.h>
#include <linux/iio/triggered_buffer.h>
#include <linux/kernel.h>
#include <linux/module.h>

#define SPS30_CRC8_POLYNOMIAL 0x31
/* max number of bytes needed to store PM measurements or serial string */
#define SPS30_MAX_READ_SIZE 48
/* sensor measures reliably up to 3000 ug / m3 */
#define SPS30_MAX_PM 3000
/* minimum and maximum self cleaning periods in seconds */
#define SPS30_AUTO_CLEANING_PERIOD_MIN 0
#define SPS30_AUTO_CLEANING_PERIOD_MAX 604800

/* SPS30 commands */
#define SPS30_START_MEAS 0x0010
#define SPS30_STOP_MEAS 0x0104
#define SPS30_RESET 0xd304
#define SPS30_READ_DATA_READY_FLAG 0x0202
#define SPS30_READ_DATA 0x0300
#define SPS30_READ_SERIAL 0xd033
#define SPS30_START_FAN_CLEANING 0x5607
#define SPS30_AUTO_CLEANING_PERIOD 0x8004
/* not a sensor command per se, used only to distinguish write from read */
#define SPS30_READ_AUTO_CLEANING_PERIOD 0x8005

enum {
	PM1,
	PM2P5,
	PM4,
	PM10,
};

enum {
	RESET,
	MEASURING,
};

struct sps30_state {
	struct i2c_client *client;
	/*
	 * Guards against concurrent access to sensor registers.
	 * Must be held whenever sequence of commands is to be executed.
	 */
	struct mutex lock;
	int state;
};

DECLARE_CRC8_TABLE(sps30_crc8_table);

static int sps30_write_then_read(struct sps30_state *state, u8 *txbuf,
				 int txsize, u8 *rxbuf, int rxsize)
{
	int ret;

	/*
	 * Sensor does not support repeated start so instead of
	 * sending two i2c messages in a row we just send one by one.
	 */
	ret = i2c_master_send(state->client, txbuf, txsize);
	if (ret != txsize)
		return ret < 0 ? ret : -EIO;

	if (!rxbuf)
		return 0;

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

	return 0;
}

static int sps30_do_cmd(struct sps30_state *state, u16 cmd, u8 *data, int size)
{
	/*
	 * Internally sensor stores measurements in a following manner:
	 *
	 * PM1: upper two bytes, crc8, lower two bytes, crc8
	 * PM2P5: upper two bytes, crc8, lower two bytes, crc8
	 * PM4: upper two bytes, crc8, lower two bytes, crc8
	 * PM10: upper two bytes, crc8, lower two bytes, crc8
	 *
	 * What follows next are number concentration measurements and
	 * typical particle size measurement which we omit.
	 */
	u8 buf[SPS30_MAX_READ_SIZE] = { cmd >> 8, cmd };
	int i, ret = 0;

	switch (cmd) {
	case SPS30_START_MEAS:
		buf[2] = 0x03;
		buf[3] = 0x00;
		buf[4] = crc8(sps30_crc8_table, &buf[2], 2, CRC8_INIT_VALUE);
		ret = sps30_write_then_read(state, buf, 5, NULL, 0);
		break;
	case SPS30_STOP_MEAS:
	case SPS30_RESET:
	case SPS30_START_FAN_CLEANING:
		ret = sps30_write_then_read(state, buf, 2, NULL, 0);
		break;
	case SPS30_READ_AUTO_CLEANING_PERIOD:
		buf[0] = SPS30_AUTO_CLEANING_PERIOD >> 8;
		buf[1] = (u8)(SPS30_AUTO_CLEANING_PERIOD & 0xff);
		/* fall through */
	case SPS30_READ_DATA_READY_FLAG:
	case SPS30_READ_DATA:
	case SPS30_READ_SERIAL:
		/* every two data bytes are checksummed */
		size += size / 2;
		ret = sps30_write_then_read(state, buf, 2, buf, size);
		break;
	case SPS30_AUTO_CLEANING_PERIOD:
		buf[2] = data[0];
		buf[3] = data[1];
		buf[4] = crc8(sps30_crc8_table, &buf[2], 2, CRC8_INIT_VALUE);
		buf[5] = data[2];
		buf[6] = data[3];
		buf[7] = crc8(sps30_crc8_table, &buf[5], 2, CRC8_INIT_VALUE);
		ret = sps30_write_then_read(state, buf, 8, NULL, 0);
		break;
	}

	if (ret)
		return ret;

	/* validate received data and strip off crc bytes */
	for (i = 0; i < size; i += 3) {
		u8 crc = crc8(sps30_crc8_table, &buf[i], 2, CRC8_INIT_VALUE);

		if (crc != buf[i + 2]) {
			dev_err(&state->client->dev,
				"data integrity check failed\n");
			return -EIO;
		}

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

	return 0;
}

static s32 sps30_float_to_int_clamped(const u8 *fp)
{
	int val = get_unaligned_be32(fp);
	int mantissa = val & GENMASK(22, 0);
	/* this is fine since passed float is always non-negative */
	int exp = val >> 23;
	int fraction, shift;

	/* special case 0 */
	if (!exp && !mantissa)
		return 0;

	exp -= 127;
	if (exp < 0) {
		/* return values ranging from 1 to 99 */
		return ((((1 << 23) + mantissa) * 100) >> 23) >> (-exp);
	}

	/* return values ranging from 100 to 300000 */
	shift = 23 - exp;
	val = (1 << exp) + (mantissa >> shift);
	if (val >= SPS30_MAX_PM)
		return SPS30_MAX_PM * 100;

	fraction = mantissa & GENMASK(shift - 1, 0);

	return val * 100 + ((fraction * 100) >> shift);
}

static int sps30_do_meas(struct sps30_state *state, s32 *data, int size)
{
	int i, ret, tries = 5;
	u8 tmp[16];

	if (state->state == RESET) {
		ret = sps30_do_cmd(state, SPS30_START_MEAS, NULL, 0);
		if (ret)
			return ret;

		state->state = MEASURING;
	}

	while (tries--) {
		ret = sps30_do_cmd(state, SPS30_READ_DATA_READY_FLAG, tmp, 2);
		if (ret)
			return -EIO;

		/* new measurements ready to be read */
		if (tmp[1] == 1)
			break;

		msleep_interruptible(300);
	}

	if (tries == -1)
		return -ETIMEDOUT;

	ret = sps30_do_cmd(state, SPS30_READ_DATA, tmp, sizeof(int) * size);
	if (ret)
		return ret;

	for (i = 0; i < size; i++)
		data[i] = sps30_float_to_int_clamped(&tmp[4 * i]);

	return 0;
}

static irqreturn_t sps30_trigger_handler(int irq, void *p)
{
	struct iio_poll_func *pf = p;
	struct iio_dev *indio_dev = pf->indio_dev;
	struct sps30_state *state = iio_priv(indio_dev);
	int ret;
	s32 data[4 + 2];