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@xxxxxxxxx>
Cc: Alessandro Zummo <a.zummo@xxxxxxxxxxxx>
Cc: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx>
Cc: rtc-linux@xxxxxxxxxxxxxxxx
Cc: Jean Delvare <jdelvare@xxxxxxxx>
Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
Cc: lm-sensors@xxxxxxxxxxxxxx
---
* v3 (all changes are suggested by Guenter Roeck)
- add RTC_DRV_DS1307_HWMON config option to fix an issue when the ds1307
driver is built into the kernel but hwmon is built as module.
- don't start user-initiated temperature conversion when reading temperature,
just relying on internal/automatic conversions.
drivers/rtc/Kconfig | 9 +++++
drivers/rtc/rtc-ds1307.c | 93 ++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 102 insertions(+)
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 2a52424..73a7e51 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -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
diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index aa705bb..3712fb3 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -19,6 +19,9 @@
#include <linux/rtc.h>
#include <linux/slab.h>
#include <linux/string.h>
+#include <linux/delay.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
/*
* We can't determine type by probing, but if we expect pre-Linux code
@@ -851,6 +854,94 @@ 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;
+ s32 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 int ds1307_hwmon_register(struct ds1307 *ds1307)
+{
+ struct device *dev;
+
+ if (ds1307->type != ds_3231)
+ return 0;
+
+ 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));
+ return PTR_ERR(dev);
+ }
+
+ return 0;
+}
+
+#else
+
+static int ds1307_hwmon_register(struct ds1307 *ds1307)
+{
+ return 0;
+}
+
+#endif
+
static int ds1307_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
@@ -1191,6 +1282,8 @@ read_rtc:
}
}
+ ds1307_hwmon_register(ds1307);
+
return 0;
exit:
--
2.5.0
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