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Commit 445c0207 authored by Akinobu Mita's avatar Akinobu Mita Committed by Alexandre Belloni
Browse files

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: default avatarAkinobu Mita <akinobu.mita@gmail.com>
Acked-by: default avatarGuenter Roeck <linux@roeck-us.net>
Signed-off-by: default avatarAlexandre Belloni <alexandre.belloni@free-electrons.com>
parent 8bc2a407

drivers/rtc/Kconfig

+9 −0
Original line number Diff line number Diff line
@@ -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

drivers/rtc/rtc-ds1307.c

+88 −0
Original line number Diff line number Diff line
@@ -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 @@ static void ds1307_trickle_of_init(struct i2c_client *client, 
	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 @@ static int ds1307_probe(struct i2c_client *client, 
		}

	}



	ds1307_hwmon_register(ds1307);



	return 0;



exit: