diff options
Diffstat (limited to 'drivers/hwmon/sht4x.c')
| -rw-r--r-- | drivers/hwmon/sht4x.c | 451 |
1 files changed, 451 insertions, 0 deletions
diff --git a/drivers/hwmon/sht4x.c b/drivers/hwmon/sht4x.c new file mode 100644 index 000000000000..5abe1227e109 --- /dev/null +++ b/drivers/hwmon/sht4x.c @@ -0,0 +1,451 @@ +// SPDX-License-Identifier: GPL-2.0-only + +/* + * Copyright (c) Linumiz 2021 + * + * sht4x.c - Linux hwmon driver for SHT4x Temperature and Humidity sensor + * + * Author: Navin Sankar Velliangiri <navin@linumiz.com> + */ + +#include <linux/crc8.h> +#include <linux/delay.h> +#include <linux/hwmon.h> +#include <linux/hwmon-sysfs.h> +#include <linux/i2c.h> +#include <linux/jiffies.h> +#include <linux/module.h> + +/* + * Poll intervals (in milliseconds) + */ +#define SHT4X_MIN_POLL_INTERVAL 2000 + +/* + * I2C command delays (in microseconds) + */ +#define SHT4X_MEAS_DELAY_HPM 8200 /* see t_MEAS,h in datasheet */ +#define SHT4X_DELAY_EXTRA 10000 + +/* + * Command Bytes + */ +#define SHT4X_CMD_MEASURE_HPM 0b11111101 +#define SHT4X_CMD_RESET 0b10010100 +#define SHT4X_CMD_HEATER_20_1 0b00011110 +#define SHT4X_CMD_HEATER_20_01 0b00010101 +#define SHT4X_CMD_HEATER_110_1 0b00101111 +#define SHT4X_CMD_HEATER_110_01 0b00100100 +#define SHT4X_CMD_HEATER_200_1 0b00111001 +#define SHT4X_CMD_HEATER_200_01 0b00110010 + +#define SHT4X_CMD_LEN 1 +#define SHT4X_CRC8_LEN 1 +#define SHT4X_WORD_LEN 2 +#define SHT4X_RESPONSE_LENGTH 6 +#define SHT4X_CRC8_POLYNOMIAL 0x31 +#define SHT4X_CRC8_INIT 0xff +#define SHT4X_MIN_TEMPERATURE -45000 +#define SHT4X_MAX_TEMPERATURE 125000 +#define SHT4X_MIN_HUMIDITY 0 +#define SHT4X_MAX_HUMIDITY 100000 + +DECLARE_CRC8_TABLE(sht4x_crc8_table); + +/** + * struct sht4x_data - All the data required to operate an SHT4X chip + * @client: the i2c client associated with the SHT4X + * @heating_complete: the time that the last heating finished + * @data_pending: true if and only if there are measurements to retrieve after heating + * @heater_power: the power at which the heater will be started + * @heater_time: the time for which the heater will remain turned on + * @valid: validity of fields below + * @update_interval: the minimum poll interval + * @last_updated: the previous time that the SHT4X was polled + * @temperature: the latest temperature value received from the SHT4X + * @humidity: the latest humidity value received from the SHT4X + */ +struct sht4x_data { + struct i2c_client *client; + unsigned long heating_complete; /* in jiffies */ + bool data_pending; + u32 heater_power; /* in milli-watts */ + u32 heater_time; /* in milli-seconds */ + bool valid; /* validity of fields below */ + long update_interval; /* in milli-seconds */ + long last_updated; /* in jiffies */ + s32 temperature; + s32 humidity; +}; + +/** + * sht4x_read_values() - read and parse the raw data from the SHT4X + * @data: the struct sht4x_data to use for the lock + * Return: 0 if successful, -ERRNO if not + */ +static int sht4x_read_values(struct sht4x_data *data) +{ + int ret; + u16 t_ticks, rh_ticks; + unsigned long next_update; + struct i2c_client *client = data->client; + u8 crc; + u8 cmd[SHT4X_CMD_LEN] = {SHT4X_CMD_MEASURE_HPM}; + u8 raw_data[SHT4X_RESPONSE_LENGTH]; + unsigned long curr_jiffies; + + curr_jiffies = jiffies; + if (time_before(curr_jiffies, data->heating_complete)) + msleep(jiffies_to_msecs(data->heating_complete - curr_jiffies)); + + if (data->data_pending && + time_before(jiffies, data->heating_complete + data->update_interval)) { + data->data_pending = false; + } else { + next_update = data->last_updated + + msecs_to_jiffies(data->update_interval); + + if (data->valid && time_before_eq(jiffies, next_update)) + return 0; + + ret = i2c_master_send(client, cmd, SHT4X_CMD_LEN); + if (ret < 0) + return ret; + + usleep_range(SHT4X_MEAS_DELAY_HPM, SHT4X_MEAS_DELAY_HPM + SHT4X_DELAY_EXTRA); + } + + ret = i2c_master_recv(client, raw_data, SHT4X_RESPONSE_LENGTH); + if (ret != SHT4X_RESPONSE_LENGTH) { + if (ret >= 0) + ret = -ENODATA; + return ret; + } + + t_ticks = raw_data[0] << 8 | raw_data[1]; + rh_ticks = raw_data[3] << 8 | raw_data[4]; + + crc = crc8(sht4x_crc8_table, &raw_data[0], SHT4X_WORD_LEN, CRC8_INIT_VALUE); + if (crc != raw_data[2]) { + dev_err(&client->dev, "data integrity check failed\n"); + return -EIO; + } + + crc = crc8(sht4x_crc8_table, &raw_data[3], SHT4X_WORD_LEN, CRC8_INIT_VALUE); + if (crc != raw_data[5]) { + dev_err(&client->dev, "data integrity check failed\n"); + return -EIO; + } + + data->temperature = ((21875 * (int32_t)t_ticks) >> 13) - 45000; + data->humidity = ((15625 * (int32_t)rh_ticks) >> 13) - 6000; + data->last_updated = jiffies; + data->valid = true; + return 0; +} + +static ssize_t sht4x_interval_write(struct sht4x_data *data, long val) +{ + data->update_interval = clamp_val(val, SHT4X_MIN_POLL_INTERVAL, INT_MAX); + + return 0; +} + +/* sht4x_interval_read() - read the minimum poll interval in milliseconds */ +static size_t sht4x_interval_read(struct sht4x_data *data, long *val) +{ + *val = data->update_interval; + return 0; +} + +/* sht4x_temperature1_read() - read the temperature in millidegrees */ +static int sht4x_temperature1_read(struct sht4x_data *data, long *val) +{ + int ret; + + ret = sht4x_read_values(data); + if (ret < 0) + return ret; + + *val = data->temperature; + + return 0; +} + +/* sht4x_humidity1_read() - read a relative humidity in millipercent */ +static int sht4x_humidity1_read(struct sht4x_data *data, long *val) +{ + int ret; + + ret = sht4x_read_values(data); + if (ret < 0) + return ret; + + *val = data->humidity; + + return 0; +} + +static umode_t sht4x_hwmon_visible(const void *data, + enum hwmon_sensor_types type, + u32 attr, int channel) +{ + switch (type) { + case hwmon_temp: + case hwmon_humidity: + return 0444; + case hwmon_chip: + return 0644; + default: + return 0; + } +} + +static int sht4x_hwmon_read(struct device *dev, enum hwmon_sensor_types type, + u32 attr, int channel, long *val) +{ + struct sht4x_data *data = dev_get_drvdata(dev); + + switch (type) { + case hwmon_temp: + return sht4x_temperature1_read(data, val); + case hwmon_humidity: + return sht4x_humidity1_read(data, val); + case hwmon_chip: + return sht4x_interval_read(data, val); + default: + return -EOPNOTSUPP; + } +} + +static int sht4x_hwmon_write(struct device *dev, enum hwmon_sensor_types type, + u32 attr, int channel, long val) +{ + struct sht4x_data *data = dev_get_drvdata(dev); + + switch (type) { + case hwmon_chip: + return sht4x_interval_write(data, val); + default: + return -EOPNOTSUPP; + } +} + +static ssize_t heater_enable_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct sht4x_data *data = dev_get_drvdata(dev); + + return sysfs_emit(buf, "%u\n", time_before(jiffies, data->heating_complete)); +} + +static ssize_t heater_enable_store(struct device *dev, + struct device_attribute *attr, + const char *buf, + size_t count) +{ + struct sht4x_data *data = dev_get_drvdata(dev); + bool status; + ssize_t ret; + u8 cmd; + u32 heating_time_bound; + + ret = kstrtobool(buf, &status); + if (ret) + return ret; + if (!status) + return -EINVAL; + + if (data->heater_time == 100) { + if (data->heater_power == 20) + cmd = SHT4X_CMD_HEATER_20_01; + else if (data->heater_power == 110) + cmd = SHT4X_CMD_HEATER_110_01; + else /* data->heater_power == 200 */ + cmd = SHT4X_CMD_HEATER_200_01; + + heating_time_bound = 110; + } else { /* data->heater_time == 1000 */ + if (data->heater_power == 20) + cmd = SHT4X_CMD_HEATER_20_1; + else if (data->heater_power == 110) + cmd = SHT4X_CMD_HEATER_110_1; + else /* data->heater_power == 200 */ + cmd = SHT4X_CMD_HEATER_200_1; + + heating_time_bound = 1100; + } + + if (time_before(jiffies, data->heating_complete)) + return -EBUSY; + + ret = i2c_master_send(data->client, &cmd, SHT4X_CMD_LEN); + if (ret < 0) + return ret; + + data->heating_complete = jiffies + msecs_to_jiffies(heating_time_bound); + data->data_pending = true; + return 0; +} + +static ssize_t heater_power_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct sht4x_data *data = dev_get_drvdata(dev); + + return sysfs_emit(buf, "%u\n", data->heater_power); +} + +static ssize_t heater_power_store(struct device *dev, + struct device_attribute *attr, + const char *buf, + size_t count) +{ + struct sht4x_data *data = dev_get_drvdata(dev); + u32 power; + ssize_t ret; + + ret = kstrtou32(buf, 10, &power); + if (ret) + return ret; + + if (power != 20 && power != 110 && power != 200) + return -EINVAL; + + data->heater_power = power; + + return count; +} + +static ssize_t heater_time_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct sht4x_data *data = dev_get_drvdata(dev); + + return sysfs_emit(buf, "%u\n", data->heater_time); +} + +static ssize_t heater_time_store(struct device *dev, + struct device_attribute *attr, + const char *buf, + size_t count) +{ + struct sht4x_data *data = dev_get_drvdata(dev); + u32 time; + ssize_t ret; + + ret = kstrtou32(buf, 10, &time); + if (ret) + return ret; + + if (time != 100 && time != 1000) + return -EINVAL; + + data->heater_time = time; + + return count; +} + +static DEVICE_ATTR_RW(heater_enable); +static DEVICE_ATTR_RW(heater_power); +static DEVICE_ATTR_RW(heater_time); + +static struct attribute *sht4x_attrs[] = { + &dev_attr_heater_enable.attr, + &dev_attr_heater_power.attr, + &dev_attr_heater_time.attr, + NULL +}; + +ATTRIBUTE_GROUPS(sht4x); + +static const struct hwmon_channel_info * const sht4x_info[] = { + HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL), + HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT), + HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT), + NULL, +}; + +static const struct hwmon_ops sht4x_hwmon_ops = { + .is_visible = sht4x_hwmon_visible, + .read = sht4x_hwmon_read, + .write = sht4x_hwmon_write, +}; + +static const struct hwmon_chip_info sht4x_chip_info = { + .ops = &sht4x_hwmon_ops, + .info = sht4x_info, +}; + +static int sht4x_probe(struct i2c_client *client) +{ + struct device *device = &client->dev; + struct device *hwmon_dev; + struct sht4x_data *data; + u8 cmd[] = {SHT4X_CMD_RESET}; + int ret; + + /* + * we require full i2c support since the sht4x uses multi-byte read and + * writes as well as multi-byte commands which are not supported by + * the smbus protocol + */ + if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) + return -EOPNOTSUPP; + + data = devm_kzalloc(device, sizeof(*data), GFP_KERNEL); + if (!data) + return -ENOMEM; + + data->update_interval = SHT4X_MIN_POLL_INTERVAL; + data->client = client; + data->heater_power = 200; + data->heater_time = 1000; + data->heating_complete = jiffies; + + crc8_populate_msb(sht4x_crc8_table, SHT4X_CRC8_POLYNOMIAL); + + ret = i2c_master_send(client, cmd, SHT4X_CMD_LEN); + if (ret < 0) + return ret; + if (ret != SHT4X_CMD_LEN) + return -EIO; + + hwmon_dev = devm_hwmon_device_register_with_info(device, + client->name, + data, + &sht4x_chip_info, + sht4x_groups); + + return PTR_ERR_OR_ZERO(hwmon_dev); +} + +static const struct i2c_device_id sht4x_id[] = { + { "sht4x" }, + { }, +}; +MODULE_DEVICE_TABLE(i2c, sht4x_id); + +static const struct of_device_id sht4x_of_match[] = { + { .compatible = "sensirion,sht4x" }, + { } +}; +MODULE_DEVICE_TABLE(of, sht4x_of_match); + +static struct i2c_driver sht4x_driver = { + .driver = { + .name = "sht4x", + .of_match_table = sht4x_of_match, + }, + .probe = sht4x_probe, + .id_table = sht4x_id, +}; + +module_i2c_driver(sht4x_driver); + +MODULE_AUTHOR("Navin Sankar Velliangiri <navin@linumiz.com>"); +MODULE_DESCRIPTION("Sensirion SHT4x humidity and temperature sensor driver"); +MODULE_LICENSE("GPL v2"); |