linux/drivers/hwmon/aht10.c
Kirill Yatsenko d2abcb5cc8 hwmon: (aht10) Add support for compatible aht20
Add support for compatible AHT20 temperature/humidity sensor. The only
difference between the two is that AHT20 has additional crc8 byte.

It seems like AHT15 is also supported by the driver but it wasn't
verified and tested yet.

Tested on Beaglebone black rev C.

Signed-off-by: Kirill Yatsenko <kiriyatsenko@gmail.com>
Link: https://lore.kernel.org/r/20230524201912.815993-1-kiriyatsenko@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
2023-06-08 06:41:18 -07:00

395 lines
9.3 KiB
C

// 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)
{
const struct i2c_device_id *id = i2c_match_id(aht10_id, client);
enum aht10_variant variant = id->driver_data;
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 <jcdra1@gmail.com>");
MODULE_DESCRIPTION("AHT10/AHT20 Temperature and Humidity sensor driver");
MODULE_VERSION("1.0");
MODULE_LICENSE("GPL v2");