From ace9429bb58fd418f0c81d4c2835699bddf6bde6 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Thu, 11 Apr 2024 10:27:49 +0200 Subject: Adding upstream version 6.6.15. Signed-off-by: Daniel Baumann --- drivers/iio/chemical/sgp40.c | 378 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 378 insertions(+) create mode 100644 drivers/iio/chemical/sgp40.c (limited to 'drivers/iio/chemical/sgp40.c') diff --git a/drivers/iio/chemical/sgp40.c b/drivers/iio/chemical/sgp40.c new file mode 100644 index 0000000000..7f0de14a19 --- /dev/null +++ b/drivers/iio/chemical/sgp40.c @@ -0,0 +1,378 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * sgp40.c - Support for Sensirion SGP40 Gas Sensor + * + * Copyright (C) 2021 Andreas Klinger + * + * I2C slave address: 0x59 + * + * Datasheet can be found here: + * https://www.sensirion.com/file/datasheet_sgp40 + * + * There are two functionalities supported: + * + * 1) read raw logarithmic resistance value from sensor + * --> useful to pass it to the algorithm of the sensor vendor for + * measuring deteriorations and improvements of air quality. + * + * 2) calculate an estimated absolute voc index (0 - 500 index points) for + * measuring the air quality. + * For this purpose the value of the resistance for which the voc index + * will be 250 can be set up using calibbias. + * + * Compensation values of relative humidity and temperature can be set up + * by writing to the out values of temp and humidityrelative. + */ + +#include +#include +#include +#include +#include +#include + +/* + * floating point calculation of voc is done as integer + * where numbers are multiplied by 1 << SGP40_CALC_POWER + */ +#define SGP40_CALC_POWER 14 + +#define SGP40_CRC8_POLYNOMIAL 0x31 +#define SGP40_CRC8_INIT 0xff + +DECLARE_CRC8_TABLE(sgp40_crc8_table); + +struct sgp40_data { + struct device *dev; + struct i2c_client *client; + int rht; + int temp; + int res_calibbias; + /* Prevent concurrent access to rht, tmp, calibbias */ + struct mutex lock; +}; + +struct sgp40_tg_measure { + u8 command[2]; + __be16 rht_ticks; + u8 rht_crc; + __be16 temp_ticks; + u8 temp_crc; +} __packed; + +struct sgp40_tg_result { + __be16 res_ticks; + u8 res_crc; +} __packed; + +static const struct iio_chan_spec sgp40_channels[] = { + { + .type = IIO_CONCENTRATION, + .channel2 = IIO_MOD_VOC, + .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), + }, + { + .type = IIO_RESISTANCE, + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | + BIT(IIO_CHAN_INFO_CALIBBIAS), + }, + { + .type = IIO_TEMP, + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), + .output = 1, + }, + { + .type = IIO_HUMIDITYRELATIVE, + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), + .output = 1, + }, +}; + +/* + * taylor approximation of e^x: + * y = 1 + x + x^2 / 2 + x^3 / 6 + x^4 / 24 + ... + x^n / n! + * + * Because we are calculating x real value multiplied by 2^power we get + * an additional 2^power^n to divide for every element. For a reasonable + * precision this would overflow after a few iterations. Therefore we + * divide the x^n part whenever its about to overflow (xmax). + */ + +static u32 sgp40_exp(int exp, u32 power, u32 rounds) +{ + u32 x, y, xp; + u32 factorial, divider, xmax; + int sign = 1; + int i; + + if (exp == 0) + return 1 << power; + else if (exp < 0) { + sign = -1; + exp *= -1; + } + + xmax = 0x7FFFFFFF / exp; + x = exp; + xp = 1; + factorial = 1; + y = 1 << power; + divider = 0; + + for (i = 1; i <= rounds; i++) { + xp *= x; + factorial *= i; + y += (xp >> divider) / factorial; + divider += power; + /* divide when next multiplication would overflow */ + if (xp >= xmax) { + xp >>= power; + divider -= power; + } + } + + if (sign == -1) + return (1 << (power * 2)) / y; + else + return y; +} + +static int sgp40_calc_voc(struct sgp40_data *data, u16 resistance_raw, int *voc) +{ + int x; + u32 exp = 0; + + /* we calculate as a multiple of 16384 (2^14) */ + mutex_lock(&data->lock); + x = ((int)resistance_raw - data->res_calibbias) * 106; + mutex_unlock(&data->lock); + + /* voc = 500 / (1 + e^x) */ + exp = sgp40_exp(x, SGP40_CALC_POWER, 18); + *voc = 500 * ((1 << (SGP40_CALC_POWER * 2)) / ((1<dev, "raw: %d res_calibbias: %d x: %d exp: %d voc: %d\n", + resistance_raw, data->res_calibbias, x, exp, *voc); + + return 0; +} + +static int sgp40_measure_resistance_raw(struct sgp40_data *data, u16 *resistance_raw) +{ + int ret; + struct i2c_client *client = data->client; + u32 ticks; + u16 ticks16; + u8 crc; + struct sgp40_tg_measure tg = {.command = {0x26, 0x0F}}; + struct sgp40_tg_result tgres; + + mutex_lock(&data->lock); + + ticks = (data->rht / 10) * 65535 / 10000; + ticks16 = (u16)clamp(ticks, 0u, 65535u); /* clamp between 0 .. 100 %rH */ + tg.rht_ticks = cpu_to_be16(ticks16); + tg.rht_crc = crc8(sgp40_crc8_table, (u8 *)&tg.rht_ticks, 2, SGP40_CRC8_INIT); + + ticks = ((data->temp + 45000) / 10 ) * 65535 / 17500; + ticks16 = (u16)clamp(ticks, 0u, 65535u); /* clamp between -45 .. +130 °C */ + tg.temp_ticks = cpu_to_be16(ticks16); + tg.temp_crc = crc8(sgp40_crc8_table, (u8 *)&tg.temp_ticks, 2, SGP40_CRC8_INIT); + + mutex_unlock(&data->lock); + + ret = i2c_master_send(client, (const char *)&tg, sizeof(tg)); + if (ret != sizeof(tg)) { + dev_warn(data->dev, "i2c_master_send ret: %d sizeof: %zu\n", ret, sizeof(tg)); + return -EIO; + } + msleep(30); + + ret = i2c_master_recv(client, (u8 *)&tgres, sizeof(tgres)); + if (ret < 0) + return ret; + if (ret != sizeof(tgres)) { + dev_warn(data->dev, "i2c_master_recv ret: %d sizeof: %zu\n", ret, sizeof(tgres)); + return -EIO; + } + + crc = crc8(sgp40_crc8_table, (u8 *)&tgres.res_ticks, 2, SGP40_CRC8_INIT); + if (crc != tgres.res_crc) { + dev_err(data->dev, "CRC error while measure-raw\n"); + return -EIO; + } + + *resistance_raw = be16_to_cpu(tgres.res_ticks); + + return 0; +} + +static int sgp40_read_raw(struct iio_dev *indio_dev, + struct iio_chan_spec const *chan, int *val, + int *val2, long mask) +{ + struct sgp40_data *data = iio_priv(indio_dev); + int ret, voc; + u16 resistance_raw; + + switch (mask) { + case IIO_CHAN_INFO_RAW: + switch (chan->type) { + case IIO_RESISTANCE: + ret = sgp40_measure_resistance_raw(data, &resistance_raw); + if (ret) + return ret; + + *val = resistance_raw; + return IIO_VAL_INT; + case IIO_TEMP: + mutex_lock(&data->lock); + *val = data->temp; + mutex_unlock(&data->lock); + return IIO_VAL_INT; + case IIO_HUMIDITYRELATIVE: + mutex_lock(&data->lock); + *val = data->rht; + mutex_unlock(&data->lock); + return IIO_VAL_INT; + default: + return -EINVAL; + } + case IIO_CHAN_INFO_PROCESSED: + ret = sgp40_measure_resistance_raw(data, &resistance_raw); + if (ret) + return ret; + + ret = sgp40_calc_voc(data, resistance_raw, &voc); + if (ret) + return ret; + + *val = voc / (1 << SGP40_CALC_POWER); + /* + * calculation should fit into integer, where: + * voc <= (500 * 2^SGP40_CALC_POWER) = 8192000 + * (with SGP40_CALC_POWER = 14) + */ + *val2 = ((voc % (1 << SGP40_CALC_POWER)) * 244) / (1 << (SGP40_CALC_POWER - 12)); + dev_dbg(data->dev, "voc: %d val: %d.%06d\n", voc, *val, *val2); + return IIO_VAL_INT_PLUS_MICRO; + case IIO_CHAN_INFO_CALIBBIAS: + mutex_lock(&data->lock); + *val = data->res_calibbias; + mutex_unlock(&data->lock); + return IIO_VAL_INT; + default: + return -EINVAL; + } +} + +static int sgp40_write_raw(struct iio_dev *indio_dev, + struct iio_chan_spec const *chan, int val, + int val2, long mask) +{ + struct sgp40_data *data = iio_priv(indio_dev); + + switch (mask) { + case IIO_CHAN_INFO_RAW: + switch (chan->type) { + case IIO_TEMP: + if ((val < -45000) || (val > 130000)) + return -EINVAL; + + mutex_lock(&data->lock); + data->temp = val; + mutex_unlock(&data->lock); + return 0; + case IIO_HUMIDITYRELATIVE: + if ((val < 0) || (val > 100000)) + return -EINVAL; + + mutex_lock(&data->lock); + data->rht = val; + mutex_unlock(&data->lock); + return 0; + default: + return -EINVAL; + } + case IIO_CHAN_INFO_CALIBBIAS: + if ((val < 20000) || (val > 52768)) + return -EINVAL; + + mutex_lock(&data->lock); + data->res_calibbias = val; + mutex_unlock(&data->lock); + return 0; + } + return -EINVAL; +} + +static const struct iio_info sgp40_info = { + .read_raw = sgp40_read_raw, + .write_raw = sgp40_write_raw, +}; + +static int sgp40_probe(struct i2c_client *client) +{ + const struct i2c_device_id *id = i2c_client_get_device_id(client); + struct device *dev = &client->dev; + struct iio_dev *indio_dev; + struct sgp40_data *data; + int ret; + + indio_dev = devm_iio_device_alloc(dev, sizeof(*data)); + if (!indio_dev) + return -ENOMEM; + + data = iio_priv(indio_dev); + data->client = client; + data->dev = dev; + + crc8_populate_msb(sgp40_crc8_table, SGP40_CRC8_POLYNOMIAL); + + mutex_init(&data->lock); + + /* set default values */ + data->rht = 50000; /* 50 % */ + data->temp = 25000; /* 25 °C */ + data->res_calibbias = 30000; /* resistance raw value for voc index of 250 */ + + indio_dev->info = &sgp40_info; + indio_dev->name = id->name; + indio_dev->modes = INDIO_DIRECT_MODE; + indio_dev->channels = sgp40_channels; + indio_dev->num_channels = ARRAY_SIZE(sgp40_channels); + + ret = devm_iio_device_register(dev, indio_dev); + if (ret) + dev_err(dev, "failed to register iio device\n"); + + return ret; +} + +static const struct i2c_device_id sgp40_id[] = { + { "sgp40" }, + { } +}; + +MODULE_DEVICE_TABLE(i2c, sgp40_id); + +static const struct of_device_id sgp40_dt_ids[] = { + { .compatible = "sensirion,sgp40" }, + { } +}; + +MODULE_DEVICE_TABLE(of, sgp40_dt_ids); + +static struct i2c_driver sgp40_driver = { + .driver = { + .name = "sgp40", + .of_match_table = sgp40_dt_ids, + }, + .probe = sgp40_probe, + .id_table = sgp40_id, +}; +module_i2c_driver(sgp40_driver); + +MODULE_AUTHOR("Andreas Klinger "); +MODULE_DESCRIPTION("Sensirion SGP40 gas sensor"); +MODULE_LICENSE("GPL v2"); -- cgit v1.2.3