From 8c78f0dee4371ab3b0422edf08597525c6219512 Mon Sep 17 00:00:00 2001 From: "Johannes Cornelis Draaijer (datdenkikniet)" Date: Thu, 7 Jan 2021 20:40:14 +0100 Subject: hwmon: Add AHT10 Temperature and Humidity Sensor Driver This patch adds a hwmon driver for the AHT10 Temperature and Humidity sensor. It has a maximum sample rate, as the datasheet states that the chip may heat up if it is sampled more than once every two seconds. Has been tested a to work on a raspberrypi0w Signed-off-by: Johannes Cornelis Draaijer (datdenkikniet) Link: https://lore.kernel.org/r/20210107194014.GA88780@desktop [groeck: dropped AHT10_ADDR (unused) and use AHT10_MEAS_SIZE where appropriate; dropped change log] Signed-off-by: Guenter Roeck --- drivers/hwmon/aht10.c | 346 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 346 insertions(+) create mode 100644 drivers/hwmon/aht10.c (limited to 'drivers/hwmon/aht10.c') diff --git a/drivers/hwmon/aht10.c b/drivers/hwmon/aht10.c new file mode 100644 index 000000000000..c70d8c2d0c1f --- /dev/null +++ b/drivers/hwmon/aht10.c @@ -0,0 +1,346 @@ +// 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) + 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"); -- cgit v1.2.3