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) <jcdra1@gmail.com>
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 <linux@roeck-us.net>
This commit is contained in:
Johannes Cornelis Draaijer (datdenkikniet) 2021-01-07 20:40:14 +01:00 committed by Guenter Roeck
parent 0bf6a1e85d
commit 8c78f0dee4
5 changed files with 404 additions and 0 deletions

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@ -0,0 +1,46 @@
.. SPDX-License-Identifier: GPL-2.0
Kernel driver aht10
=====================
Supported chips:
* Aosong AHT10
Prefix: 'aht10'
Addresses scanned: None
Datasheet:
Chinese: http://www.aosong.com/userfiles/files/media/AHT10%E4%BA%A7%E5%93%81%E6%89%8B%E5%86%8C%20A3%2020201210.pdf
English: https://server4.eca.ir/eshop/AHT10/Aosong_AHT10_en_draft_0c.pdf
Author: Johannes Cornelis Draaijer <jcdra1@gmail.com>
Description
-----------
The AHT10 is a Temperature and Humidity sensor
The address of this i2c device may only be 0x38
Usage Notes
-----------
This driver does not probe for AHT10 devices, as there is no reliable
way to determine if an i2c chip is or isn't an AHT10. The device has
to be instantiated explicitly with the address 0x38. See
Documentation/i2c/instantiating-devices.rst for details.
Sysfs entries
-------------
=============== ============================================
temp1_input Measured temperature in millidegrees Celcius
humidity1_input Measured humidity in %H
update_interval The minimum interval for polling the sensor,
in milliseconds. Writable. Must be at
least 2000.
=============== ============================================

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@ -37,6 +37,7 @@ Hardware Monitoring Kernel Drivers
adt7462
adt7470
adt7475
aht10
amc6821
amd_energy
asb100

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@ -244,6 +244,16 @@ config SENSORS_ADT7475
This driver can also be built as a module. If so, the module
will be called adt7475.
config SENSORS_AHT10
tristate "Aosong AHT10"
depends on I2C
help
If you say yes here, you get support for the Aosong AHT10
temperature and humidity sensors
This driver can also be built as a module. If so, the module
will be called aht10.
config SENSORS_AS370
tristate "Synaptics AS370 SoC hardware monitoring driver"
help

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@ -44,6 +44,7 @@ obj-$(CONFIG_SENSORS_ADT7411) += adt7411.o
obj-$(CONFIG_SENSORS_ADT7462) += adt7462.o
obj-$(CONFIG_SENSORS_ADT7470) += adt7470.o
obj-$(CONFIG_SENSORS_ADT7475) += adt7475.o
obj-$(CONFIG_SENSORS_AHT10) += aht10.o
obj-$(CONFIG_SENSORS_AMD_ENERGY) += amd_energy.o
obj-$(CONFIG_SENSORS_APPLESMC) += applesmc.o
obj-$(CONFIG_SENSORS_ARM_SCMI) += scmi-hwmon.o

346
drivers/hwmon/aht10.c Normal file
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// 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 <linux/delay.h>
#include <linux/hwmon.h>
#include <linux/i2c.h>
#include <linux/ktime.h>
#include <linux/module.h>
#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 <jcdra1@gmail.com>");
MODULE_DESCRIPTION("AHT10 Temperature and Humidity sensor driver");
MODULE_VERSION("1.0");
MODULE_LICENSE("GPL v2");