[PATCH 6/6] rtc: isl12022: add support for temperature sensor

[Rasmus Villemoes <linux@rasmusvillemoes.dk>]

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
 drivers/rtc/rtc-isl12022.c | 81 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)

diff --git a/drivers/rtc/rtc-isl12022.c b/drivers/rtc/rtc-isl12022.c
index b295ec92ee17..1bd72f436318 100644
--- a/drivers/rtc/rtc-isl12022.c
+++ b/drivers/rtc/rtc-isl12022.c
@@ -17,6 +17,8 @@
 #include <linux/of.h>
 #include <linux/of_device.h>
 #include <linux/regmap.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
 
 /* ISL register offsets */
 #define ISL12022_REG_SC		0x00
@@ -30,6 +32,9 @@
 #define ISL12022_REG_SR		0x07
 #define ISL12022_REG_INT	0x08
 
+#define ISL12022_REG_BETA	0x0d
+#define ISL12022_REG_TEMP_L	0x28
+
 /* ISL register bits */
 #define ISL12022_HR_MIL		(1 << 7)	/* military or 24 hour time */
 
@@ -38,6 +43,7 @@
 
 #define ISL12022_INT_WRTC	(1 << 6)
 
+#define ISL12022_BETA_TSE	(1 << 7)
 
 static struct i2c_driver isl12022_driver;
 
@@ -48,6 +54,79 @@ struct isl12022 {
 	bool write_enabled;	/* true if write enable is set */
 };
 
+/*
+ * A user-initiated temperature conversion is not started by this function,
+ * so the temperature is updated once every ~60 seconds.
+ */
+static int isl12022_hwmon_read_temp(struct device *dev, s32 *mC)
+{
+	struct isl12022 *isl12022 = dev_get_drvdata(dev);
+	struct regmap *regmap = isl12022->regmap;
+	u8 temp_buf[2];
+	s32 temp;
+	int ret;
+
+	ret = regmap_bulk_read(regmap, ISL12022_REG_TEMP_L,
+			       temp_buf, sizeof(temp_buf));
+	if (ret)
+		return ret;
+	/*
+	 * Temperature is represented as a 10-bit number, unit half-Kelvins.
+	 */
+	temp = (temp_buf[1] << 8) | temp_buf[0];
+	temp *= 500;
+	temp -= 273000;
+
+	*mC = temp;
+
+	return 0;
+}
+
+static ssize_t
+isl12022_hwmon_show_temp(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	int ret;
+	s32 temp;
+
+	ret = isl12022_hwmon_read_temp(dev, &temp);
+	if (ret)
+		return ret;
+
+	return sprintf(buf, "%d\n", temp);
+}
+static SENSOR_DEVICE_ATTR(temp1_input, 0444, isl12022_hwmon_show_temp,
+			  NULL, 0);
+
+static struct attribute *isl12022_hwmon_attrs[] = {
+	&sensor_dev_attr_temp1_input.dev_attr.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(isl12022_hwmon);
+
+static void isl12022_hwmon_register(struct device *dev)
+{
+	struct isl12022 *isl12022;
+	struct device *hwmon;
+	int ret;
+
+	if (!IS_REACHABLE(CONFIG_HWMON))
+		return;
+
+	isl12022 = dev_get_drvdata(dev);
+
+	ret = regmap_update_bits(isl12022->regmap, ISL12022_REG_BETA,
+				 ISL12022_BETA_TSE, ISL12022_BETA_TSE);
+	if (ret) {
+		dev_warn(dev, "unable to enable temperature sensor\n");
+		return;
+	}
+
+	hwmon = devm_hwmon_device_register_with_groups(dev, "isl12022", isl12022,
+						       isl12022_hwmon_groups);
+	if (IS_ERR(hwmon))
+		dev_warn(dev, "unable to register hwmon device: %pe\n", hwmon);
+}
+
 /*
  * In the routines that deal directly with the isl12022 hardware, we use
  * rtc_time -- month 0-11, hour 0-23, yr = calendar year-epoch.
@@ -179,6 +258,8 @@ static int isl12022_probe(struct i2c_client *client)
 		return PTR_ERR(isl12022->regmap);
 	}
 
+	isl12022_hwmon_register(&client->dev);
+
 	isl12022->rtc = devm_rtc_allocate_device(&client->dev);
 	if (IS_ERR(isl12022->rtc))
 		return PTR_ERR(isl12022->rtc);
-- 
2.37.2