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
---
* v2
- convert to use hwmon framework, suggested by Alexandre Belloni
drivers/rtc/rtc-ds1307.c | 122 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 122 insertions(+)
diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index aa705bb..e0d4ce5 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
@@ -75,6 +78,7 @@ enum ds_type {
# define DS1337_BIT_nEOSC 0x80
# define DS1339_BIT_BBSQI 0x20
# define DS3231_BIT_BBSQW 0x40 /* same as BBSQI */
+# define DS3231_BIT_CONV 0x20
# define DS1337_BIT_RS2 0x10
# define DS1337_BIT_RS1 0x08
# define DS1337_BIT_INTCN 0x04
@@ -89,6 +93,7 @@ enum ds_type {
# define DS1340_BIT_OSF 0x80
#define DS1337_REG_STATUS 0x0f
# define DS1337_BIT_OSF 0x80
+# define DS3231_BIT_BSY 0x04
# define DS1337_BIT_A2I 0x02
# define DS1337_BIT_A1I 0x01
#define DS1339_REG_ALARM1_SECS 0x07
@@ -851,6 +856,121 @@ out:
return;
}
+/*----------------------------------------------------------------------*/
+
+#if IS_ENABLED(CONFIG_HWMON)
+
+/*
+ * Temperature sensor support for ds3231 devices.
+ */
+
+#define DS3231_REG_TEMPERATURE 0x11
+
+static ssize_t ds3231_hwmon_show_temp(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct ds1307 *ds1307 = dev_get_drvdata(dev);
+ struct i2c_client *client = ds1307->client;
+ u8 temp_buf[2];
+ s16 temp;
+ int control;
+ int status;
+ s32 ret;
+ unsigned long timeout;
+
+ status = i2c_smbus_read_byte_data(client, DS1337_REG_STATUS);
+ if (status < 0)
+ return status;
+
+ /*
+ * Start user-initiated temperature conversion
+ */
+ if (!(status & DS3231_BIT_BSY)) {
+ struct mutex *lock = &ds1307->rtc->ops_lock;
+
+ mutex_lock(lock);
+
+ control = i2c_smbus_read_byte_data(client, DS1337_REG_CONTROL);
+ if (control < 0) {
+ mutex_unlock(lock);
+ return control;
+ }
+ ret = i2c_smbus_write_byte_data(client, DS1337_REG_CONTROL,
+ control | DS3231_BIT_CONV);
+ if (ret)
+ return ret;
+
+ mutex_unlock(lock);
+
+ /*
+ * A user-initiated temperature conversion does not affect
+ * the BSY bit for approximately 2ms.
+ */
+ usleep_range(2000, 3000);
+ }
+
+ /*
+ * Wait until the conversion is finished
+ */
+ timeout = jiffies + HZ;
+
+ do {
+ control = i2c_smbus_read_byte_data(client, DS1337_REG_CONTROL);
+ if (control < 0)
+ return control;
+ if (!(control & DS3231_BIT_CONV))
+ break;
+ if (time_after(jiffies, timeout))
+ return -EIO;
+ usleep_range(2000, 3000);
+ } while (1);
+
+ 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;
+
+ return sprintf(buf, "%d\n", temp * 250);
+}
+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)
+{
+ if (ds1307->type != ds_3231)
+ return 0;
+
+ devm_hwmon_device_register_with_groups(&ds1307->client->dev,
+ ds1307->client->name,
+ ds1307, ds3231_hwmon_groups);
+
+ 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 +1311,8 @@ read_rtc:
}
}
+ ds1307_hwmon_register(ds1307);
+
return 0;
exit:
--
2.5.0
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