Add sht21 relative humidity and temperature sensor driver. There already exists an in-kernel driver under hwmon but with limited functionality like humidity and temperature always measured together at predefined resolutions, etc.
New iio driver comes without limitations of predecessor, uses non-blocking i2c communication mode and adds triggered buffer support thus is suited for more use cases. Device datasheet can be found under: https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/ \ Dokumente/2_Humidity_Sensors/Sensirion_Humidity_Sensors_SHT21_Datasheet_V4.pdf Signed-off-by: Tomasz Duszynski <tdusz...@gmail.com> --- drivers/iio/humidity/Kconfig | 10 + drivers/iio/humidity/Makefile | 1 + drivers/iio/humidity/sht21.c | 519 ++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 530 insertions(+) create mode 100644 drivers/iio/humidity/sht21.c diff --git a/drivers/iio/humidity/Kconfig b/drivers/iio/humidity/Kconfig index 866dda133336..93247ecc9324 100644 --- a/drivers/iio/humidity/Kconfig +++ b/drivers/iio/humidity/Kconfig @@ -35,6 +35,16 @@ config HTU21 This driver can also be built as a module. If so, the module will be called htu21. +config SHT21 + tristate "Sensirion SHT21 relative humidity and temperature sensor" + depends on I2C + help + Say yes here to build support for the Sensirion SHT21 relative + humidity and temperature sensor. + + To compile this driver as a module, choose M here: the module + will be called sht21. + config SI7005 tristate "SI7005 relative humidity and temperature sensor" depends on I2C diff --git a/drivers/iio/humidity/Makefile b/drivers/iio/humidity/Makefile index c9f089a9a6b8..f2472fd2cc44 100644 --- a/drivers/iio/humidity/Makefile +++ b/drivers/iio/humidity/Makefile @@ -5,5 +5,6 @@ obj-$(CONFIG_DHT11) += dht11.o obj-$(CONFIG_HDC100X) += hdc100x.o obj-$(CONFIG_HTU21) += htu21.o +obj-$(CONFIG_SHT21) += sht21.o obj-$(CONFIG_SI7005) += si7005.o obj-$(CONFIG_SI7020) += si7020.o diff --git a/drivers/iio/humidity/sht21.c b/drivers/iio/humidity/sht21.c new file mode 100644 index 000000000000..199933b87297 --- /dev/null +++ b/drivers/iio/humidity/sht21.c @@ -0,0 +1,519 @@ +/* + * Sensirion SHT21 relative humidity and temperature sensor driver + * + * Copyright (C) 2017 Tomasz Duszynski <tdusz...@gmail.com> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * 7-bit I2C slave address: 0x40 + */ + +#include <linux/bitops.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/module.h> +#include <linux/mutex.h> +#include <linux/of.h> + +#define SHT21_DRV_NAME "sht21" + +#define SHT21_TRIGGER_T_MEASUREMENT 0xF3 +#define SHT21_TRIGGER_RH_MEASUREMENT 0xF5 + +#define SHT21_WRITE_USER_REG 0xE6 +#define SHT21_READ_USER_REG 0xE7 +#define SHT21_SOFT_RESET 0xFE + +#define SHT21_USER_REG_RES_8_12 BIT(0) +#define SHT21_USER_REG_RES_10_13 BIT(7) +#define SHT21_USER_REG_RES_11_11 (BIT(7) | BIT(0)) + +#define SHT21_USER_REG_ENABLE_HEATER BIT(2) + +enum { + RES_12_14, + RES_8_12, + RES_10_13, + RES_11_11, +}; + +/* + * Combined sampling frequency i.e measuring RH and T together, which seems + * to be common case for pressure/humidity sensors, was chosen so that sensor + * is active for only 10% of time thus avoiding self-heating effect. + * + * Note that sampling frequencies are higher when measuring RH or T separately. + * + * Following table shows how available resolutions, combined sampling frequency + * and frequencies for RH and T when measured separately are related. + * + * +-------------------+-------------+---------+--------+ + * | RH / T resolution | RH + T [Hz] | RH [Hz] | T [Hz] | + * +-------------------+-------------+---------+--------+ + * | 12 / 14 | 0.88 | 3.45 | 1.18 | + * +-------------------+-------------+---------+--------+ + * | 8 / 12 | 3.85 | 25 | 4.55 | + * +-------------------+-------------+---------+--------+ + * | 10 / 13 | 1.93 | 11.11 | 2.33 | + * +-------------------+-------------+---------+--------+ + * | 11 / 11 | 2.28 | 6.67 | 9.09 | + * +-------------------+-------------+---------+--------+ + */ +static const struct { + int freq; + int freq2; + + int rh_meas_time; + int t_meas_time; +} sht21_freq_meas_time_tbl[] = { + [RES_12_14] = { 0, 880000, 29000, 85000 }, + [RES_8_12] = { 3, 850000, 4000, 22000 }, + [RES_10_13] = { 1, 930000, 9000, 43000 }, + [RES_11_11] = { 2, 280000, 15000, 11000 } +}; + +struct sht21_state { + struct i2c_client *client; + struct mutex lock; + int res; +}; + +static int sht21_verify_crc(const u8 *data, int len) +{ + int i, j; + u8 crc = 0; + + for (i = 0; i < len; i++) { + crc ^= data[i]; + + for (j = 0; j < 8; j++) { + if (crc & 0x80) + crc = (crc << 1) ^ 0x31; + else + crc = crc << 1; + } + } + + return crc == 0; +} + +/* every chunk of data read from sensor has crc byte appended */ +static int sht21_read_data(struct sht21_state *state, int cmd, int *data) +{ + int delay, ret = 0; + __be32 tmp = 0; + + switch (cmd) { + case SHT21_READ_USER_REG: + ret = i2c_smbus_read_i2c_block_data(state->client, cmd, + 2, (u8 *)&tmp); + break; + case SHT21_TRIGGER_RH_MEASUREMENT: + case SHT21_TRIGGER_T_MEASUREMENT: + ret = i2c_smbus_write_byte(state->client, cmd); + if (ret) + break; + + delay = cmd == SHT21_TRIGGER_RH_MEASUREMENT ? + sht21_freq_meas_time_tbl[state->res].rh_meas_time : + sht21_freq_meas_time_tbl[state->res].t_meas_time; + + usleep_range(delay, delay + 1000); + + ret = i2c_master_recv(state->client, (u8 *)&tmp, 3); + if (ret < 0) + break; + + /* + * Sensor should not be active more that 10% of time + * otherwise it heats up and returns biased measurements. + */ + delay *= 9; + usleep_range(delay, delay + 1000); + + break; + } + + if (ret < 0) + return ret; + + if (!sht21_verify_crc((u8 *)&tmp, ret)) { + dev_err(&state->client->dev, "Data integrity check failed\n"); + return -EINVAL; + } + + /* crc byte no longer needed so drop it here */ + *data = be32_to_cpu(tmp) >> ((sizeof(tmp) - ret + 1) * 8); + + return 0; +} + +static int sht21_write_data(struct sht21_state *state, int cmd, int *data) +{ + int ret; + + if (!data) + ret = i2c_smbus_write_byte(state->client, cmd); + else + ret = i2c_smbus_write_byte_data(state->client, cmd, *data); + + return ret; +} + +static int sht21_trigger_measurement(struct sht21_state *state, int cmd, int *data) +{ + int ret; + + mutex_lock(&state->lock); + ret = sht21_read_data(state, cmd, data); + if (ret) { + mutex_unlock(&state->lock); + return ret; + } + mutex_unlock(&state->lock); + + return 0; +} + +static int sht21_trigger_rh_measurement(struct sht21_state *state, int *data) +{ + int ret = sht21_trigger_measurement(state, SHT21_TRIGGER_RH_MEASUREMENT, data); + if (ret) + return ret; + + *data >>= 2; + *data = (((s64)*data * 125000) >> 14) - 6000; + + return 0; +} + +static int sht21_trigger_t_measurement(struct sht21_state *state, int *data) +{ + int ret = sht21_trigger_measurement(state, SHT21_TRIGGER_T_MEASUREMENT, data); + if (ret) + return ret; + + *data >>= 2; + *data = (((s64)*data * 175720) >> 14) - 46850; + + return 0; +} + +static int sht21_set_resolution(struct sht21_state *state, int res) +{ + int ret, data; + + ret = sht21_read_data(state, SHT21_READ_USER_REG, &data); + if (ret) + return ret; + + data &= ~SHT21_USER_REG_RES_11_11; + + switch (res) { + case RES_12_14: + break; + case RES_8_12: + data |= SHT21_USER_REG_RES_8_12; + break; + case RES_10_13: + data |= SHT21_USER_REG_RES_10_13; + break; + case RES_11_11: + data |= SHT21_USER_REG_RES_11_11; + break; + } + + ret = sht21_write_data(state, SHT21_WRITE_USER_REG, &data); + if (ret) + return ret; + + state->res = res; + + return 0; +} + +static int sht21_soft_reset(struct sht21_state *state) +{ + int ret = sht21_write_data(state, SHT21_SOFT_RESET, NULL); + if (ret) { + dev_err(&state->client->dev, "Failed to reset device\n"); + return ret; + } + + msleep(15); + + return 0; +} + +static irqreturn_t sht21_trigger_handler(int irq, void *p) +{ + struct iio_poll_func *pf = p; + struct iio_dev *indio_dev = pf->indio_dev; + struct sht21_state *state = iio_priv(indio_dev); + int buf[4], ret, i, j = 0; + + for_each_set_bit(i, indio_dev->active_scan_mask, indio_dev->masklength) { + ret = i == 0 ? sht21_trigger_rh_measurement(state, &buf[j++]) : + sht21_trigger_t_measurement(state, &buf[j++]); + if (ret) + goto out; + } + + iio_push_to_buffers_with_timestamp(indio_dev, buf, + iio_get_time_ns(indio_dev)); +out: + iio_trigger_notify_done(indio_dev->trig); + + return IRQ_HANDLED; +} + +static int sht21_read_raw(struct iio_dev *indio_dev, + struct iio_chan_spec const *channel, int *val, + int *val2, long mask) +{ + struct sht21_state *state = iio_priv(indio_dev); + int ret; + + switch (mask) { + case IIO_CHAN_INFO_PROCESSED: + if (iio_buffer_enabled(indio_dev)) + return -EBUSY; + + switch (channel->type) { + case IIO_HUMIDITYRELATIVE: + ret = sht21_trigger_rh_measurement(state, val); + if (ret) + return ret; + + return IIO_VAL_INT; + case IIO_TEMP: + ret = sht21_trigger_t_measurement(state, val); + if (ret) + return ret; + + return IIO_VAL_INT; + default: + return -EINVAL; + } + case IIO_CHAN_INFO_SAMP_FREQ: + *val = sht21_freq_meas_time_tbl[state->res].freq; + *val2 = sht21_freq_meas_time_tbl[state->res].freq2; + + return IIO_VAL_INT_PLUS_MICRO; + default: + return -EINVAL; + } +} + +static int sht21_write_raw(struct iio_dev *indio_dev, + struct iio_chan_spec const *chan, + int val, int val2, long mask) +{ + struct sht21_state *state = iio_priv(indio_dev); + int i, ret; + + switch (mask) { + case IIO_CHAN_INFO_SAMP_FREQ: + for (i = 0; i < ARRAY_SIZE(sht21_freq_meas_time_tbl); i++) + if (val == sht21_freq_meas_time_tbl[i].freq && + val2 == sht21_freq_meas_time_tbl[i].freq2) + break; + + if (i == ARRAY_SIZE(sht21_freq_meas_time_tbl)) + return -EINVAL; + + ret = iio_device_claim_direct_mode(indio_dev); + if (ret) + return ret; + + mutex_lock(&state->lock); + ret = sht21_set_resolution(state, i); + mutex_unlock(&state->lock); + + iio_device_release_direct_mode(indio_dev); + + return ret; + default: + return -EINVAL; + } +} + +static ssize_t sht21_show_heater(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct iio_dev *indio_dev = dev_to_iio_dev(dev); + struct sht21_state *state = iio_priv(indio_dev); + int data, ret; + + ret = sht21_read_data(state, SHT21_READ_USER_REG, &data); + if (ret) + return ret; + + return sprintf(buf, "%d\n", !!(data & SHT21_USER_REG_ENABLE_HEATER)); +} + +static ssize_t sht21_write_heater(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t len) +{ + struct iio_dev *indio_dev = dev_to_iio_dev(dev); + struct sht21_state *state = iio_priv(indio_dev); + int val, data, ret; + + ret = kstrtoint(buf, 10, &val); + if (ret) + return ret; + if (val != 0 && val != 1) + return -EINVAL; + + mutex_lock(&state->lock); + ret = sht21_read_data(state, SHT21_READ_USER_REG, &data); + if (ret) { + mutex_unlock(&state->lock); + return ret; + } + + if (val) + data |= SHT21_USER_REG_ENABLE_HEATER; + else + data &= ~SHT21_USER_REG_ENABLE_HEATER; + + ret = sht21_write_data(state, SHT21_WRITE_USER_REG, &data); + mutex_unlock(&state->lock); + + return ret ? ret : len; +} + +static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("0.88 1.93 2.28 3.85"); +static IIO_DEVICE_ATTR(heater_enable, S_IRUGO | S_IWUSR, + sht21_show_heater, sht21_write_heater, 0); + +static struct attribute *sht21_attributes[] = { + &iio_const_attr_sampling_frequency_available.dev_attr.attr, + &iio_dev_attr_heater_enable.dev_attr.attr, + NULL +}; + +static const struct attribute_group sht21_attribute_group = { + .attrs = sht21_attributes, +}; + +static const struct iio_info sht21_info = { + .driver_module = THIS_MODULE, + .read_raw = sht21_read_raw, + .write_raw = sht21_write_raw, + .attrs = &sht21_attribute_group, +}; + +#define SHT21_CHANNEL(_type, _index) { \ + .type = _type, \ + .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), \ + .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ), \ + .scan_index = _index, \ + .scan_type = { \ + .sign = 's', \ + .realbits = 32, \ + .storagebits = 32, \ + .endianness = IIO_CPU, \ + }, \ +} + +static const struct iio_chan_spec sht21_channels[] = { + SHT21_CHANNEL(IIO_HUMIDITYRELATIVE, 0), + SHT21_CHANNEL(IIO_TEMP, 1), + IIO_CHAN_SOFT_TIMESTAMP(2), +}; + +static int sht21_probe(struct i2c_client *client, const struct i2c_device_id *id) +{ + struct iio_dev *indio_dev; + struct sht21_state *data; + int ret; + + if (!i2c_check_functionality(client->adapter, + I2C_FUNC_SMBUS_WRITE_BYTE | + I2C_FUNC_SMBUS_BYTE_DATA | + I2C_FUNC_SMBUS_READ_I2C_BLOCK)) + return -ENODEV; + + indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data)); + if (!indio_dev) + return -ENOMEM; + + data = iio_priv(indio_dev); + i2c_set_clientdata(client, indio_dev); + data->client = client; + mutex_init(&data->lock); + + indio_dev->dev.parent = &client->dev; + indio_dev->name = id->name; + indio_dev->modes = INDIO_DIRECT_MODE; + indio_dev->info = &sht21_info; + indio_dev->channels = sht21_channels; + indio_dev->num_channels = ARRAY_SIZE(sht21_channels); + + ret = sht21_soft_reset(data); + if (ret) + return ret; + + ret = iio_triggered_buffer_setup(indio_dev, NULL, + sht21_trigger_handler, NULL); + if (ret) + return ret; + + ret = iio_device_register(indio_dev); + if (ret) + iio_triggered_buffer_cleanup(indio_dev); + + return ret; +} + +static int sht21_remove(struct i2c_client *client) +{ + struct iio_dev *indio_dev = i2c_get_clientdata(client); + + iio_device_unregister(indio_dev); + iio_triggered_buffer_cleanup(indio_dev); + + return 0; +} + +static const struct i2c_device_id sht21_id[] = { + { "sht21", 0 }, + { } +}; +MODULE_DEVICE_TABLE(i2c, sht21_id); + +static const struct of_device_id sht21_of_match[] = { + { .compatible = "sensirion,sht21" }, + { } +}; +MODULE_DEVICE_TABLE(of, sht21_of_match); + +static struct i2c_driver sht21_driver = { + .driver = { + .name = SHT21_DRV_NAME, + .of_match_table = of_match_ptr(sht21_of_match), + }, + .id_table = sht21_id, + .probe = sht21_probe, + .remove = sht21_remove, +}; +module_i2c_driver(sht21_driver); + +MODULE_DESCRIPTION("Sensirion SHT21 relative humidity and temperature sensor driver"); +MODULE_AUTHOR("Tomasz Duszynski <tdusz...@gmail.com>"); +MODULE_LICENSE("GPL v2"); -- 2.11.1
