// SPDX-License-Identifier: GPL-2.0-only
/*
* aht10.c - Linux hwmon driver for AHT10/AHT20 Temperature and Humidity sensors
* Copyright (C) 2020 Johannes Cornelis Draaijer
*/
#include <linux/delay.h>
#include <linux/hwmon.h>
#include <linux/i2c.h>
#include <linux/ktime.h>
#include <linux/module.h>
#include <linux/crc8.h>
#define AHT10_MEAS_SIZE 6
#define AHT20_MEAS_SIZE 7
#define AHT20_CRC8_POLY 0x31
/*
* 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
enum aht10_variant { aht10, aht20 };
static const struct i2c_device_id aht10_id[] = {
{ "aht10", aht10 },
{ "aht20", aht20 },
{ },
};
MODULE_DEVICE_TABLE(i2c, aht10_id);
/**
* struct aht10_data - All the data required to operate an AHT10/AHT20 chip
* @client: the i2c client associated with the AHT10/AHT20
* @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/AHT20
* was polled
* @temperature: the latest temperature value received from
* the AHT10/AHT20
* @humidity: the latest humidity value received from the
* AHT10/AHT20
* @crc8: crc8 support flag
* @meas_size: measurements data size
*/
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;
bool crc8;
unsigned int meas_size;
};
/**
* aht10_init() - Initialize an AHT10/AHT20 chip
* @data: the data associated with this AHT10/AHT20 chip
* Return: 0 if successful, 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);
}
DECLARE_CRC8_TABLE(crc8_table);
/**
* crc8_check() - check crc of the sensor's measurements
* @raw_data: data frame received from sensor(including crc as the last byte)
* @count: size of the data frame
* Return: 0 if successful, 1 if not
*/
static int crc8_check(u8 *raw_data, int count)
{
/*
* crc calculated on the whole frame(including crc byte) should yield
* zero in case of correctly received bytes
*/
return crc8(crc8_table, raw_data, count, CRC8_INIT_VALUE);
}
/**
* aht10_read_values() - read and parse the raw data from the AHT10/AHT20
* @data: the struct aht10_data to use for the lock
* Return: 0 if successful, 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[AHT20_MEAS_SIZE];
struct i2c_client *client = data->client;
mutex_lock(&data->lock);
if (!aht10_polltime_expired(data)) {
mutex_unlock(&data->lock);
return 0;
}
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, data->meas_size);
if (res != data->meas_size) {
mutex_unlock(&data->lock);
if (res >= 0)
return -ENODATA;
return res;
}
if (data->crc8 && crc8_check(raw_data, data->meas_size)) {
mutex_unlock(&data->lock);
return -EIO;
}
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 * const 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)
{
enum aht10_variant variant = (uintptr_t)i2c_get_match_data(client);
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;
switch (variant) {
case aht20:
data->meas_size = AHT20_MEAS_SIZE;
data->crc8 = true;
crc8_populate_msb(crc8_table, AHT20_CRC8_POLY);
break;
default:
data->meas_size = AHT10_MEAS_SIZE;
break;
}
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 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 <[email protected]>");
MODULE_DESCRIPTION("AHT10/AHT20 Temperature and Humidity sensor driver");
MODULE_VERSION("1.0");
MODULE_LICENSE("GPL v2");
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