[PATCH] hwmon: (nct7802) Make RTD modes configurable.

[Oskar Senft]

This change allows the RTD modes to be configurable via device tree
bindings. When the setting is not present via device tree, the driver
still defaults to the previous behavior where the RTD modes are left
alone.

Signed-off-by: Oskar Senft <osk@xxxxxxxxxx>
---
 drivers/hwmon/nct7802.c | 94 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 92 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/nct7802.c b/drivers/hwmon/nct7802.c
index 604af2f6103a..6a6ab529bdd3 100644
--- a/drivers/hwmon/nct7802.c
+++ b/drivers/hwmon/nct7802.c
@@ -51,6 +51,24 @@ static const u8 REG_VOLTAGE_LIMIT_MSB_SHIFT[2][5] = {
 #define REG_CHIP_ID		0xfe
 #define REG_VERSION_ID		0xff
 
+/*
+ * Sensor modes according to 7.2.32 Mode Selection Register
+ */
+#define RTD_MODE_CLOSED		0x0
+#define RTD_MODE_CURRENT	0x1
+#define RTD_MODE_THERMISTOR	0x2
+#define RTD_MODE_VOLTAGE	0x3
+#define RTD_MODE_UNDEFINED	0xf
+
+#define MODE_BITS_MASK		0x3
+
+/*
+ * Bit offsets for sensors modes in REG_MODE
+ */
+#define MODE_OFFSET_RTD1	0
+#define MODE_OFFSET_RTD2	2
+#define MODE_OFFSET_RTD3	4
+
 /*
  * Data structures and manipulation thereof
  */
@@ -1038,7 +1056,9 @@ static const struct regmap_config nct7802_regmap_config = {
 	.volatile_reg = nct7802_regmap_is_volatile,
 };
 
-static int nct7802_init_chip(struct nct7802_data *data)
+static int nct7802_init_chip(struct nct7802_data *data,
+	unsigned char rtd1_mode, unsigned char rtd2_mode,
+	unsigned char rtd3_mode)
 {
 	int err;
 
@@ -1052,15 +1072,57 @@ static int nct7802_init_chip(struct nct7802_data *data)
 	if (err)
 		return err;
 
+	/* Configure sensor modes */
+	if ((rtd1_mode & MODE_BITS_MASK) == rtd1_mode) {
+		err = regmap_update_bits(data->regmap, REG_MODE,
+			MODE_BITS_MASK << MODE_OFFSET_RTD1,
+			rtd1_mode << MODE_OFFSET_RTD1);
+		if (err)
+			return err;
+	}
+	if ((rtd2_mode & MODE_BITS_MASK) == rtd2_mode) {
+		err = regmap_update_bits(data->regmap, REG_MODE,
+			MODE_BITS_MASK << MODE_OFFSET_RTD2,
+			rtd2_mode << MODE_OFFSET_RTD2);
+		if (err)
+			return err;
+	}
+	if ((rtd3_mode & MODE_BITS_MASK) == rtd3_mode) {
+		err = regmap_update_bits(data->regmap, REG_MODE,
+			MODE_BITS_MASK << MODE_OFFSET_RTD3,
+			rtd3_mode << MODE_OFFSET_RTD3);
+		if (err)
+			return err;
+	}
+
 	/* Enable Vcore and VCC voltage monitoring */
 	return regmap_update_bits(data->regmap, REG_VMON_ENABLE, 0x03, 0x03);
 }
 
+static unsigned char rtd_mode_from_string(const char *value)
+{
+	if (!strcmp(value, "closed"))
+		return RTD_MODE_CLOSED;
+	if (!strcmp(value, "current"))
+		return RTD_MODE_CURRENT;
+	if (!strcmp(value, "thermistor"))
+		return RTD_MODE_THERMISTOR;
+	if (!strcmp(value, "voltage"))
+		return RTD_MODE_VOLTAGE;
+
+	return RTD_MODE_UNDEFINED;
+}
+
 static int nct7802_probe(struct i2c_client *client)
 {
 	struct device *dev = &client->dev;
 	struct nct7802_data *data;
 	struct device *hwmon_dev;
+	int rtd_mode_count;
+	unsigned char rtd1_mode = RTD_MODE_UNDEFINED;
+	unsigned char rtd2_mode = RTD_MODE_UNDEFINED;
+	unsigned char rtd3_mode = RTD_MODE_UNDEFINED;
+	const char *prop_value;
 	int ret;
 
 	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
@@ -1074,7 +1136,25 @@ static int nct7802_probe(struct i2c_client *client)
 	mutex_init(&data->access_lock);
 	mutex_init(&data->in_alarm_lock);
 
-	ret = nct7802_init_chip(data);
+	if (dev->of_node) {
+		rtd_mode_count = of_property_count_strings(dev->of_node,
+			"nuvoton,rtd-modes");
+
+		if (rtd_mode_count > 0)
+			if (!of_property_read_string_index(dev->of_node,
+				"nuvoton,rtd-modes", 0, &prop_value))
+				rtd1_mode = rtd_mode_from_string(prop_value);
+		if (rtd_mode_count > 1)
+			if (!of_property_read_string_index(dev->of_node,
+				"nuvoton,rtd-modes", 1, &prop_value))
+				rtd2_mode = rtd_mode_from_string(prop_value);
+		if (rtd_mode_count > 2)
+			if (!of_property_read_string_index(dev->of_node,
+				"nuvoton,rtd-modes", 2, &prop_value))
+				rtd3_mode = rtd_mode_from_string(prop_value);
+	}
+
+	ret = nct7802_init_chip(data, rtd1_mode, rtd2_mode, rtd3_mode);
 	if (ret < 0)
 		return ret;
 
@@ -1094,10 +1174,20 @@ static const struct i2c_device_id nct7802_idtable[] = {
 };
 MODULE_DEVICE_TABLE(i2c, nct7802_idtable);
 
+static const struct of_device_id __maybe_unused nct7802_of_match[] = {
+	{
+		.compatible = "nuvoton,nct7802",
+		.data = 0
+	},
+	{ },
+};
+MODULE_DEVICE_TABLE(of, nct7802_of_match);
+
 static struct i2c_driver nct7802_driver = {
 	.class = I2C_CLASS_HWMON,
 	.driver = {
 		.name = DRVNAME,
+		.of_match_table = of_match_ptr(nct7802_of_match),
 	},
 	.detect = nct7802_detect,
 	.probe_new = nct7802_probe,
-- 
2.33.0.309.g3052b89438-goog