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348 lines
8.2 KiB
348 lines
8.2 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* aht10.c - Linux hwmon driver for AHT10 Temperature and Humidity sensor |
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* Copyright (C) 2020 Johannes Cornelis Draaijer |
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*/ |
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#include <linux/delay.h> |
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#include <linux/hwmon.h> |
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#include <linux/i2c.h> |
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#include <linux/ktime.h> |
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#include <linux/module.h> |
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#define AHT10_MEAS_SIZE 6 |
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/* |
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* Poll intervals (in milliseconds) |
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*/ |
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#define AHT10_DEFAULT_MIN_POLL_INTERVAL 2000 |
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#define AHT10_MIN_POLL_INTERVAL 2000 |
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/* |
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* I2C command delays (in microseconds) |
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*/ |
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#define AHT10_MEAS_DELAY 80000 |
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#define AHT10_CMD_DELAY 350000 |
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#define AHT10_DELAY_EXTRA 100000 |
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/* |
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* Command bytes |
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*/ |
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#define AHT10_CMD_INIT 0b11100001 |
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#define AHT10_CMD_MEAS 0b10101100 |
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#define AHT10_CMD_RST 0b10111010 |
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/* |
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* Flags in the answer byte/command |
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*/ |
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#define AHT10_CAL_ENABLED BIT(3) |
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#define AHT10_BUSY BIT(7) |
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#define AHT10_MODE_NOR (BIT(5) | BIT(6)) |
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#define AHT10_MODE_CYC BIT(5) |
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#define AHT10_MODE_CMD BIT(6) |
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#define AHT10_MAX_POLL_INTERVAL_LEN 30 |
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/** |
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* struct aht10_data - All the data required to operate an AHT10 chip |
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* @client: the i2c client associated with the AHT10 |
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* @lock: a mutex that is used to prevent parallel access to the |
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* i2c client |
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* @min_poll_interval: the minimum poll interval |
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* While the poll rate limit is not 100% necessary, |
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* the datasheet recommends that a measurement |
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* is not performed too often to prevent |
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* the chip from warming up due to the heat it generates. |
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* If it's unwanted, it can be ignored setting it to |
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* it to 0. Default value is 2000 ms |
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* @previous_poll_time: the previous time that the AHT10 |
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* was polled |
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* @temperature: the latest temperature value received from |
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* the AHT10 |
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* @humidity: the latest humidity value received from the |
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* AHT10 |
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*/ |
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struct aht10_data { |
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struct i2c_client *client; |
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/* |
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* Prevent simultaneous access to the i2c |
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* client and previous_poll_time |
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*/ |
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struct mutex lock; |
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ktime_t min_poll_interval; |
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ktime_t previous_poll_time; |
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int temperature; |
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int humidity; |
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}; |
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/** |
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* aht10_init() - Initialize an AHT10 chip |
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* @client: the i2c client associated with the AHT10 |
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* @data: the data associated with this AHT10 chip |
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* Return: 0 if succesfull, 1 if not |
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*/ |
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static int aht10_init(struct aht10_data *data) |
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{ |
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const u8 cmd_init[] = {AHT10_CMD_INIT, AHT10_CAL_ENABLED | AHT10_MODE_CYC, |
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0x00}; |
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int res; |
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u8 status; |
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struct i2c_client *client = data->client; |
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res = i2c_master_send(client, cmd_init, 3); |
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if (res < 0) |
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return res; |
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usleep_range(AHT10_CMD_DELAY, AHT10_CMD_DELAY + |
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AHT10_DELAY_EXTRA); |
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res = i2c_master_recv(client, &status, 1); |
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if (res != 1) |
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return -ENODATA; |
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if (status & AHT10_BUSY) |
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return -EBUSY; |
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return 0; |
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} |
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/** |
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* aht10_polltime_expired() - check if the minimum poll interval has |
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* expired |
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* @data: the data containing the time to compare |
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* Return: 1 if the minimum poll interval has expired, 0 if not |
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*/ |
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static int aht10_polltime_expired(struct aht10_data *data) |
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{ |
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ktime_t current_time = ktime_get_boottime(); |
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ktime_t difference = ktime_sub(current_time, data->previous_poll_time); |
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return ktime_after(difference, data->min_poll_interval); |
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} |
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/** |
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* aht10_read_values() - read and parse the raw data from the AHT10 |
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* @aht10_data: the struct aht10_data to use for the lock |
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* Return: 0 if succesfull, 1 if not |
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*/ |
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static int aht10_read_values(struct aht10_data *data) |
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{ |
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const u8 cmd_meas[] = {AHT10_CMD_MEAS, 0x33, 0x00}; |
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u32 temp, hum; |
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int res; |
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u8 raw_data[AHT10_MEAS_SIZE]; |
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struct i2c_client *client = data->client; |
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mutex_lock(&data->lock); |
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if (aht10_polltime_expired(data)) { |
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res = i2c_master_send(client, cmd_meas, sizeof(cmd_meas)); |
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if (res < 0) { |
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mutex_unlock(&data->lock); |
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return res; |
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} |
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usleep_range(AHT10_MEAS_DELAY, |
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AHT10_MEAS_DELAY + AHT10_DELAY_EXTRA); |
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res = i2c_master_recv(client, raw_data, AHT10_MEAS_SIZE); |
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if (res != AHT10_MEAS_SIZE) { |
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mutex_unlock(&data->lock); |
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if (res >= 0) |
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return -ENODATA; |
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else |
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return res; |
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} |
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hum = ((u32)raw_data[1] << 12u) | |
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((u32)raw_data[2] << 4u) | |
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((raw_data[3] & 0xF0u) >> 4u); |
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temp = ((u32)(raw_data[3] & 0x0Fu) << 16u) | |
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((u32)raw_data[4] << 8u) | |
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raw_data[5]; |
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temp = ((temp * 625) >> 15u) * 10; |
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hum = ((hum * 625) >> 16u) * 10; |
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data->temperature = (int)temp - 50000; |
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data->humidity = hum; |
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data->previous_poll_time = ktime_get_boottime(); |
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} |
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mutex_unlock(&data->lock); |
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return 0; |
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} |
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/** |
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* aht10_interval_write() - store the given minimum poll interval. |
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* Return: 0 on success, -EINVAL if a value lower than the |
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* AHT10_MIN_POLL_INTERVAL is given |
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*/ |
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static ssize_t aht10_interval_write(struct aht10_data *data, |
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long val) |
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{ |
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data->min_poll_interval = ms_to_ktime(clamp_val(val, 2000, LONG_MAX)); |
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return 0; |
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} |
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/** |
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* aht10_interval_read() - read the minimum poll interval |
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* in milliseconds |
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*/ |
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static ssize_t aht10_interval_read(struct aht10_data *data, |
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long *val) |
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{ |
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*val = ktime_to_ms(data->min_poll_interval); |
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return 0; |
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} |
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/** |
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* aht10_temperature1_read() - read the temperature in millidegrees |
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*/ |
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static int aht10_temperature1_read(struct aht10_data *data, long *val) |
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{ |
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int res; |
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res = aht10_read_values(data); |
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if (res < 0) |
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return res; |
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*val = data->temperature; |
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return 0; |
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} |
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/** |
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* aht10_humidity1_read() - read the relative humidity in millipercent |
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*/ |
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static int aht10_humidity1_read(struct aht10_data *data, long *val) |
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{ |
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int res; |
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res = aht10_read_values(data); |
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if (res < 0) |
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return res; |
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*val = data->humidity; |
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return 0; |
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} |
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static umode_t aht10_hwmon_visible(const void *data, enum hwmon_sensor_types type, |
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u32 attr, int channel) |
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{ |
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switch (type) { |
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case hwmon_temp: |
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case hwmon_humidity: |
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return 0444; |
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case hwmon_chip: |
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return 0644; |
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default: |
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return 0; |
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} |
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} |
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static int aht10_hwmon_read(struct device *dev, enum hwmon_sensor_types type, |
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u32 attr, int channel, long *val) |
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{ |
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struct aht10_data *data = dev_get_drvdata(dev); |
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switch (type) { |
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case hwmon_temp: |
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return aht10_temperature1_read(data, val); |
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case hwmon_humidity: |
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return aht10_humidity1_read(data, val); |
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case hwmon_chip: |
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return aht10_interval_read(data, val); |
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default: |
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return -EOPNOTSUPP; |
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} |
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} |
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static int aht10_hwmon_write(struct device *dev, enum hwmon_sensor_types type, |
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u32 attr, int channel, long val) |
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{ |
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struct aht10_data *data = dev_get_drvdata(dev); |
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switch (type) { |
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case hwmon_chip: |
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return aht10_interval_write(data, val); |
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default: |
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return -EOPNOTSUPP; |
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} |
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} |
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static const struct hwmon_channel_info *aht10_info[] = { |
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HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL), |
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HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT), |
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HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT), |
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NULL, |
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}; |
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static const struct hwmon_ops aht10_hwmon_ops = { |
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.is_visible = aht10_hwmon_visible, |
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.read = aht10_hwmon_read, |
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.write = aht10_hwmon_write, |
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}; |
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static const struct hwmon_chip_info aht10_chip_info = { |
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.ops = &aht10_hwmon_ops, |
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.info = aht10_info, |
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}; |
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static int aht10_probe(struct i2c_client *client, |
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const struct i2c_device_id *aht10_id) |
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{ |
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struct device *device = &client->dev; |
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struct device *hwmon_dev; |
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struct aht10_data *data; |
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int res; |
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if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) |
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return -ENOENT; |
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data = devm_kzalloc(device, sizeof(*data), GFP_KERNEL); |
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if (!data) |
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return -ENOMEM; |
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data->min_poll_interval = ms_to_ktime(AHT10_DEFAULT_MIN_POLL_INTERVAL); |
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data->client = client; |
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mutex_init(&data->lock); |
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res = aht10_init(data); |
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if (res < 0) |
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return res; |
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res = aht10_read_values(data); |
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if (res < 0) |
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return res; |
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hwmon_dev = devm_hwmon_device_register_with_info(device, |
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client->name, |
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data, |
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&aht10_chip_info, |
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NULL); |
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return PTR_ERR_OR_ZERO(hwmon_dev); |
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} |
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static const struct i2c_device_id aht10_id[] = { |
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{ "aht10", 0 }, |
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{ }, |
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}; |
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MODULE_DEVICE_TABLE(i2c, aht10_id); |
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static struct i2c_driver aht10_driver = { |
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.driver = { |
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.name = "aht10", |
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}, |
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.probe = aht10_probe, |
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.id_table = aht10_id, |
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}; |
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module_i2c_driver(aht10_driver); |
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MODULE_AUTHOR("Johannes Cornelis Draaijer <[email protected]>"); |
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MODULE_DESCRIPTION("AHT10 Temperature and Humidity sensor driver"); |
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MODULE_VERSION("1.0"); |
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MODULE_LICENSE("GPL v2");
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