395 lines
9.3 KiB
C
395 lines
9.3 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* aht10.c - Linux hwmon driver for AHT10/AHT20 Temperature and Humidity sensors
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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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#include <linux/crc8.h>
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#define AHT10_MEAS_SIZE 6
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#define AHT20_MEAS_SIZE 7
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#define AHT20_CRC8_POLY 0x31
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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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enum aht10_variant { aht10, aht20 };
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static const struct i2c_device_id aht10_id[] = {
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{ "aht10", aht10 },
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{ "aht20", aht20 },
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{ },
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};
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MODULE_DEVICE_TABLE(i2c, aht10_id);
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/**
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* struct aht10_data - All the data required to operate an AHT10/AHT20 chip
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* @client: the i2c client associated with the AHT10/AHT20
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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/AHT20
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* was polled
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* @temperature: the latest temperature value received from
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* the AHT10/AHT20
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* @humidity: the latest humidity value received from the
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* AHT10/AHT20
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* @crc8: crc8 support flag
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* @meas_size: measurements data size
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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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bool crc8;
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unsigned int meas_size;
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};
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/**
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* aht10_init() - Initialize an AHT10/AHT20 chip
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* @data: the data associated with this AHT10/AHT20 chip
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* Return: 0 if successful, 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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DECLARE_CRC8_TABLE(crc8_table);
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/**
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* crc8_check() - check crc of the sensor's measurements
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* @raw_data: data frame received from sensor(including crc as the last byte)
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* @count: size of the data frame
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* Return: 0 if successful, 1 if not
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*/
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static int crc8_check(u8 *raw_data, int count)
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{
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/*
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* crc calculated on the whole frame(including crc byte) should yield
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* zero in case of correctly received bytes
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*/
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return crc8(crc8_table, raw_data, count, CRC8_INIT_VALUE);
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}
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/**
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* aht10_read_values() - read and parse the raw data from the AHT10/AHT20
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* @data: the struct aht10_data to use for the lock
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* Return: 0 if successful, 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[AHT20_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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mutex_unlock(&data->lock);
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return 0;
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}
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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, AHT10_MEAS_DELAY + AHT10_DELAY_EXTRA);
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res = i2c_master_recv(client, raw_data, data->meas_size);
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if (res != data->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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return res;
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}
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if (data->crc8 && crc8_check(raw_data, data->meas_size)) {
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mutex_unlock(&data->lock);
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return -EIO;
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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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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 * const 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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{
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const struct i2c_device_id *id = i2c_match_id(aht10_id, client);
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enum aht10_variant variant = id->driver_data;
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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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switch (variant) {
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case aht20:
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data->meas_size = AHT20_MEAS_SIZE;
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data->crc8 = true;
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crc8_populate_msb(crc8_table, AHT20_CRC8_POLY);
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break;
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default:
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data->meas_size = AHT10_MEAS_SIZE;
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break;
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}
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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 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 <jcdra1@gmail.com>");
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MODULE_DESCRIPTION("AHT10/AHT20 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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