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>
diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index bfedeb5..2462d5a 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -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 @@
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 @@
}
}
+ ds1307_hwmon_register(ds1307);
+
return 0;
exit: