// SPDX-License-Identifier: GPL-2.0-only /* * aht10.c - Linux hwmon driver for AHT10 Temperature and Humidity sensor * Copyright (C) 2020 Johannes Cornelis Draaijer */ #include #include #include #include #include #define AHT10_MEAS_SIZE 6 /* * Poll intervals (in milliseconds) */ #define AHT10_DEFAULT_MIN_POLL_INTERVAL 2000 #define AHT10_MIN_POLL_INTERVAL 2000 /* * I2C command delays (in microseconds) */ #define AHT10_MEAS_DELAY 80000 #define AHT10_CMD_DELAY 350000 #define AHT10_DELAY_EXTRA 100000 /* * Command bytes */ #define AHT10_CMD_INIT 0b11100001 #define AHT10_CMD_MEAS 0b10101100 #define AHT10_CMD_RST 0b10111010 /* * Flags in the answer byte/command */ #define AHT10_CAL_ENABLED BIT(3) #define AHT10_BUSY BIT(7) #define AHT10_MODE_NOR (BIT(5) | BIT(6)) #define AHT10_MODE_CYC BIT(5) #define AHT10_MODE_CMD BIT(6) #define AHT10_MAX_POLL_INTERVAL_LEN 30 /** * struct aht10_data - All the data required to operate an AHT10 chip * @client: the i2c client associated with the AHT10 * @lock: a mutex that is used to prevent parallel access to the * i2c client * @min_poll_interval: the minimum poll interval * While the poll rate limit is not 100% necessary, * the datasheet recommends that a measurement * is not performed too often to prevent * the chip from warming up due to the heat it generates. * If it's unwanted, it can be ignored setting it to * it to 0. Default value is 2000 ms * @previous_poll_time: the previous time that the AHT10 * was polled * @temperature: the latest temperature value received from * the AHT10 * @humidity: the latest humidity value received from the * AHT10 */ struct aht10_data { struct i2c_client *client; /* * Prevent simultaneous access to the i2c * client and previous_poll_time */ struct mutex lock; ktime_t min_poll_interval; ktime_t previous_poll_time; int temperature; int humidity; }; /** * aht10_init() - Initialize an AHT10 chip * @client: the i2c client associated with the AHT10 * @data: the data associated with this AHT10 chip * Return: 0 if succesfull, 1 if not */ static int aht10_init(struct aht10_data *data) { const u8 cmd_init[] = {AHT10_CMD_INIT, AHT10_CAL_ENABLED | AHT10_MODE_CYC, 0x00}; int res; u8 status; struct i2c_client *client = data->client; res = i2c_master_send(client, cmd_init, 3); if (res < 0) return res; usleep_range(AHT10_CMD_DELAY, AHT10_CMD_DELAY + AHT10_DELAY_EXTRA); res = i2c_master_recv(client, &status, 1); if (res != 1) return -ENODATA; if (status & AHT10_BUSY) return -EBUSY; return 0; } /** * aht10_polltime_expired() - check if the minimum poll interval has * expired * @data: the data containing the time to compare * Return: 1 if the minimum poll interval has expired, 0 if not */ static int aht10_polltime_expired(struct aht10_data *data) { ktime_t current_time = ktime_get_boottime(); ktime_t difference = ktime_sub(current_time, data->previous_poll_time); return ktime_after(difference, data->min_poll_interval); } /** * aht10_read_values() - read and parse the raw data from the AHT10 * @aht10_data: the struct aht10_data to use for the lock * Return: 0 if succesfull, 1 if not */ static int aht10_read_values(struct aht10_data *data) { const u8 cmd_meas[] = {AHT10_CMD_MEAS, 0x33, 0x00}; u32 temp, hum; int res; u8 raw_data[AHT10_MEAS_SIZE]; struct i2c_client *client = data->client; mutex_lock(&data->lock); if (aht10_polltime_expired(data)) { res = i2c_master_send(client, cmd_meas, sizeof(cmd_meas)); if (res < 0) { mutex_unlock(&data->lock); return res; } usleep_range(AHT10_MEAS_DELAY, AHT10_MEAS_DELAY + AHT10_DELAY_EXTRA); res = i2c_master_recv(client, raw_data, AHT10_MEAS_SIZE); if (res != AHT10_MEAS_SIZE) { mutex_unlock(&data->lock); if (res >= 0) return -ENODATA; else return res; } hum = ((u32)raw_data[1] << 12u) | ((u32)raw_data[2] << 4u) | ((raw_data[3] & 0xF0u) >> 4u); temp = ((u32)(raw_data[3] & 0x0Fu) << 16u) | ((u32)raw_data[4] << 8u) | raw_data[5]; temp = ((temp * 625) >> 15u) * 10; hum = ((hum * 625) >> 16u) * 10; data->temperature = (int)temp - 50000; data->humidity = hum; data->previous_poll_time = ktime_get_boottime(); } mutex_unlock(&data->lock); return 0; } /** * aht10_interval_write() - store the given minimum poll interval. * Return: 0 on success, -EINVAL if a value lower than the * AHT10_MIN_POLL_INTERVAL is given */ static ssize_t aht10_interval_write(struct aht10_data *data, long val) { data->min_poll_interval = ms_to_ktime(clamp_val(val, 2000, LONG_MAX)); return 0; } /** * aht10_interval_read() - read the minimum poll interval * in milliseconds */ static ssize_t aht10_interval_read(struct aht10_data *data, long *val) { *val = ktime_to_ms(data->min_poll_interval); return 0; } /** * aht10_temperature1_read() - read the temperature in millidegrees */ static int aht10_temperature1_read(struct aht10_data *data, long *val) { int res; res = aht10_read_values(data); if (res < 0) return res; *val = data->temperature; return 0; } /** * aht10_humidity1_read() - read the relative humidity in millipercent */ static int aht10_humidity1_read(struct aht10_data *data, long *val) { int res; res = aht10_read_values(data); if (res < 0) return res; *val = data->humidity; return 0; } static umode_t aht10_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 aht10_hwmon_read(struct device *dev, enum hwmon_sensor_types type, u32 attr, int channel, long *val) { struct aht10_data *data = dev_get_drvdata(dev); switch (type) { case hwmon_temp: return aht10_temperature1_read(data, val); case hwmon_humidity: return aht10_humidity1_read(data, val); case hwmon_chip: return aht10_interval_read(data, val); default: return -EOPNOTSUPP; } } static int aht10_hwmon_write(struct device *dev, enum hwmon_sensor_types type, u32 attr, int channel, long val) { struct aht10_data *data = dev_get_drvdata(dev); switch (type) { case hwmon_chip: return aht10_interval_write(data, val); default: return -EOPNOTSUPP; } } static const struct hwmon_channel_info *aht10_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 aht10_hwmon_ops = { .is_visible = aht10_hwmon_visible, .read = aht10_hwmon_read, .write = aht10_hwmon_write, }; static const struct hwmon_chip_info aht10_chip_info = { .ops = &aht10_hwmon_ops, .info = aht10_info, }; static int aht10_probe(struct i2c_client *client, const struct i2c_device_id *aht10_id) { struct device *device = &client->dev; struct device *hwmon_dev; struct aht10_data *data; int res; if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) return -ENOENT; data = devm_kzalloc(device, sizeof(*data), GFP_KERNEL); if (!data) return -ENOMEM; data->min_poll_interval = ms_to_ktime(AHT10_DEFAULT_MIN_POLL_INTERVAL); data->client = client; mutex_init(&data->lock); res = aht10_init(data); if (res < 0) return res; res = aht10_read_values(data); if (res < 0) return res; hwmon_dev = devm_hwmon_device_register_with_info(device, client->name, data, &aht10_chip_info, NULL); return PTR_ERR_OR_ZERO(hwmon_dev); } static const struct i2c_device_id aht10_id[] = { { "aht10", 0 }, { }, }; MODULE_DEVICE_TABLE(i2c, aht10_id); static struct i2c_driver aht10_driver = { .driver = { .name = "aht10", }, .probe = aht10_probe, .id_table = aht10_id, }; module_i2c_driver(aht10_driver); MODULE_AUTHOR("Johannes Cornelis Draaijer "); MODULE_DESCRIPTION("AHT10 Temperature and Humidity sensor driver"); MODULE_VERSION("1.0"); MODULE_LICENSE("GPL v2");