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rtc: ds1307: add temperature sensor support for ds3231 

DS3231 has the temperature registers with a resolution of 0.25
degree celsius.  This enables to get the value through hwmon.

	# cat /sys/class/i2c-adapter/i2c-2/2-0068/hwmon/hwmon0/temp1_input
	21000

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
This commit is contained in:
Akinobu Mita 2016-01-25 00:22:16 +09:00 committed by Alexandre Belloni
parent 8bc2a40730
commit 445c02076f
2 changed files with 97 additions and 0 deletions
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9
drivers/rtc/Kconfig
View File

@ -212,6 +212,15 @@ config RTC_DRV_DS1307
This driver can also be built as a module. If so, the module
will be called rtc-ds1307.
config RTC_DRV_DS1307_HWMON
bool "HWMON support for rtc-ds1307"
depends on RTC_DRV_DS1307 && HWMON
depends on !(RTC_DRV_DS1307=y && HWMON=m)
default y
help
Say Y here if you want to expose temperature sensor data on
rtc-ds1307 (only DS3231)
config RTC_DRV_DS1374
tristate "Dallas/Maxim DS1374"
help

88
drivers/rtc/rtc-ds1307.c
View File

@ -19,6 +19,8 @@
#include <linux/rtc.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
/*
* We can't determine type by probing, but if we expect pre-Linux code
@ -842,6 +844,90 @@ out:
return;
}
/*----------------------------------------------------------------------*/
#ifdef CONFIG_RTC_DRV_DS1307_HWMON
/*
* Temperature sensor support for ds3231 devices.
*/
#define DS3231_REG_TEMPERATURE 0x11
/*
* A user-initiated temperature conversion is not started by this function,
* so the temperature is updated once every 64 seconds.
*/
static int ds3231_hwmon_read_temp(struct device *dev, s16 *mC)
{
struct ds1307 *ds1307 = dev_get_drvdata(dev);
u8 temp_buf[2];
s16 temp;
int ret;
ret = ds1307->read_block_data(ds1307->client, DS3231_REG_TEMPERATURE,
sizeof(temp_buf), temp_buf);
if (ret < 0)
return ret;
if (ret != sizeof(temp_buf))
return -EIO;
/*
* Temperature is represented as a 10-bit code with a resolution of
* 0.25 degree celsius and encoded in two's complement format.
*/
temp = (temp_buf[0] << 8) | temp_buf[1];
temp >>= 6;
*mC = temp * 250;
return 0;
}
static ssize_t ds3231_hwmon_show_temp(struct device *dev,
struct device_attribute *attr, char *buf)
{
int ret;
s16 temp;
ret = ds3231_hwmon_read_temp(dev, &temp);
if (ret)
return ret;
return sprintf(buf, "%d\n", temp);
}
static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, ds3231_hwmon_show_temp,
NULL, 0);
static struct attribute *ds3231_hwmon_attrs[] = {
&sensor_dev_attr_temp1_input.dev_attr.attr,
NULL,
};
ATTRIBUTE_GROUPS(ds3231_hwmon);
static void ds1307_hwmon_register(struct ds1307 *ds1307)
{
struct device *dev;
if (ds1307->type != ds_3231)
return;
dev = devm_hwmon_device_register_with_groups(&ds1307->client->dev,
ds1307->client->name,
ds1307, ds3231_hwmon_groups);
if (IS_ERR(dev)) {
dev_warn(&ds1307->client->dev,
"unable to register hwmon device %ld\n", PTR_ERR(dev));
}
}
#else
static void ds1307_hwmon_register(struct ds1307 *ds1307)
{
}
#endif
static int ds1307_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
@ -1207,6 +1293,8 @@ read_rtc:
}
}
ds1307_hwmon_register(ds1307);
return 0;
exit: