[PATCH v2 2/2] hwmon: (nct7802) Make temperature sensors configurable.

[Oskar Senft]

This change allows the temperature sensors (both LTD and RTD) to be
configurable via device tree bindings. When the new settings are not
present, the driver defaults to the previous behavior where the RTDs
are left alone and LTD is explicitly enabled.

Signed-off-by: Oskar Senft <osk@xxxxxxxxxx>
---
 drivers/hwmon/nct7802.c | 141 ++++++++++++++++++++++++++++++++++++----
 1 file changed, 127 insertions(+), 14 deletions(-)

diff --git a/drivers/hwmon/nct7802.c b/drivers/hwmon/nct7802.c
index 604af2f6103a..ac2299b110a1 100644
--- a/drivers/hwmon/nct7802.c
+++ b/drivers/hwmon/nct7802.c
@@ -51,6 +51,20 @@ static const u8 REG_VOLTAGE_LIMIT_MSB_SHIFT[2][5] = {
 #define REG_CHIP_ID		0xfe
 #define REG_VERSION_ID		0xff
 
+/*
+ * Resistance temperature detector (RTD) modes according to 7.2.32 Mode
+ * Selection Register
+ */
+
+#define MODE_RTD_MASK		0x3
+#define MODE_LTD_EN		0x40
+
+/*
+ * Bit offset for sensors modes in REG_MODE.
+ * Valid for index 0..2, indicating RTD1..3.
+ */
+#define MODE_BIT_OFFSET_RTD(index) ((index) * 2)
+
 /*
  * Data structures and manipulation thereof
  */
@@ -74,7 +88,9 @@ static ssize_t temp_type_show(struct device *dev,
 	if (ret < 0)
 		return ret;
 
-	return sprintf(buf, "%u\n", (mode >> (2 * sattr->index) & 3) + 2);
+	return sprintf(buf, "%u\n",
+			((mode >> MODE_BIT_OFFSET_RTD(sattr->index)) &
+				MODE_RTD_MASK) + 2);
 }
 
 static ssize_t temp_type_store(struct device *dev,
@@ -94,7 +110,8 @@ static ssize_t temp_type_store(struct device *dev,
 	if (type < 3 || type > 4)
 		return -EINVAL;
 	err = regmap_update_bits(data->regmap, REG_MODE,
-			3 << 2 * sattr->index, (type - 2) << 2 * sattr->index);
+			MODE_RTD_MASK << MODE_BIT_OFFSET_RTD(sattr->index),
+			(type - 2) << MODE_BIT_OFFSET_RTD(sattr->index));
 	return err ? : count;
 }
 
@@ -688,18 +705,18 @@ static umode_t nct7802_temp_is_visible(struct kobject *kobj,
 	if (err < 0)
 		return 0;
 
-	if (index < 10 &&
-	    (reg & 03) != 0x01 && (reg & 0x03) != 0x02)		/* RD1 */
+	if (index >= 0 && index < 20 &&				/* RD1, RD 2*/
+	    ((reg >> MODE_BIT_OFFSET_RTD(index / 10)) & MODE_RTD_MASK) != 0x01 &&
+	    ((reg >> MODE_BIT_OFFSET_RTD(index / 10)) & MODE_RTD_MASK) != 0x02)
 		return 0;
 
-	if (index >= 10 && index < 20 &&
-	    (reg & 0x0c) != 0x04 && (reg & 0x0c) != 0x08)	/* RD2 */
-		return 0;
-	if (index >= 20 && index < 30 && (reg & 0x30) != 0x20)	/* RD3 */
+	if (index >= 20 && index < 30 &&			/* RD3 */
+	    (reg >> MODE_BIT_OFFSET_RTD(index / 10) & MODE_RTD_MASK != 0x02))
 		return 0;
 
-	if (index >= 30 && index < 38)				/* local */
-		return attr->mode;
+	if (index >= 30 && index < 38 &&			/* local */
+	    (reg & MODE_LTD_EN) != MODE_LTD_EN)
+		return 0;
 
 	err = regmap_read(data->regmap, REG_PECI_ENABLE, &reg);
 	if (err < 0)
@@ -1038,8 +1055,97 @@ static const struct regmap_config nct7802_regmap_config = {
 	.volatile_reg = nct7802_regmap_is_volatile,
 };
 
-static int nct7802_init_chip(struct nct7802_data *data)
+static bool nct7802_configure_temperature_sensors_from_device_tree(
+	struct device *dev, unsigned char *mode_mask, unsigned char *mode_val)
 {
+	struct device_node *sensors, *sensor;
+	int err;
+	u8 idx;
+	u32 type;
+
+	if (!dev->of_node)
+		return false;
+
+	sensors = of_get_child_by_name(dev->of_node, "temperature-sensors");
+	if (!sensors)
+		return false;
+
+	for_each_child_of_node(sensors, sensor) {
+		if (!strcmp(sensor->name, "ltd")) {
+			if (!of_device_is_available(sensor)) {
+				*mode_val &= ~MODE_LTD_EN;
+				*mode_mask |= MODE_LTD_EN;
+			} else {
+				*mode_val |= MODE_LTD_EN;
+				*mode_mask |= MODE_LTD_EN;
+			}
+			continue;
+		}
+
+		/* Check for rtdX, with X being the sensor number */
+		if (strcmp(sensor->name, "rtd") > 0) {
+			err = kstrtou8(
+				sensor->name + strlen("rdt"), 10, &idx);
+			if (err) {
+				dev_err(dev,
+					"Unparseable sensor number in '%s'\n",
+					sensor->name);
+				continue;
+			}
+
+			if (idx < 1 || idx > 3) {
+				dev_err(dev,
+					"Invalid sensor number in '%s'\n",
+					sensor->name);
+				continue;
+			}
+
+			if (!of_device_is_available(sensor)) {
+				*mode_val &= ~(MODE_RTD_MASK
+					<< MODE_BIT_OFFSET_RTD(idx-1));
+				*mode_mask |= MODE_RTD_MASK
+					<< MODE_BIT_OFFSET_RTD(idx-1);
+				continue;
+			}
+
+			if (idx == 3) {
+				/* RTD3 only supports thermistor mode */
+				type = 4;
+			} else if (of_property_count_u32_elems(sensor, "type")
+				> 0) {
+				if (of_property_read_u32_index(
+					sensor, "type", 0, &type)) {
+					dev_err(dev,
+						"Could not read type property for '%s'\n",
+						sensor->name);
+					continue;
+				}
+
+				/* Only current and thermistor modes are valid
+				 * for temperature sensors.
+				 */
+				if (type < 3 || type > 4) {
+					dev_err(dev,
+						"Type %u not supported for '%s'\n",
+						type, sensor->name);
+					continue;
+				}
+			}
+
+			/* Everything ok, so write sensor configuration */
+			*mode_val |= ((type - 2) & MODE_RTD_MASK)
+				<< MODE_BIT_OFFSET_RTD(idx-1);
+			*mode_mask |= MODE_RTD_MASK
+				<< MODE_BIT_OFFSET_RTD(idx-1);
+		}
+	}
+
+	return true;
+}
+
+static int nct7802_init_chip(struct device *dev, struct nct7802_data *data)
+{
+	unsigned char mode_val = 0, mode_mask = 0;
 	int err;
 
 	/* Enable ADC */
@@ -1047,8 +1153,15 @@ static int nct7802_init_chip(struct nct7802_data *data)
 	if (err)
 		return err;
 
-	/* Enable local temperature sensor */
-	err = regmap_update_bits(data->regmap, REG_MODE, 0x40, 0x40);
+	if (!nct7802_configure_temperature_sensors_from_device_tree(dev,
+			&mode_mask, &mode_val)) {
+		/* Enable local temperature sensor by default */
+		mode_val |= MODE_LTD_EN;
+		mode_mask |= MODE_LTD_EN;
+	}
+
+	err = regmap_update_bits(data->regmap, REG_MODE, mode_mask,
+		mode_val);
 	if (err)
 		return err;
 
@@ -1074,7 +1187,7 @@ static int nct7802_probe(struct i2c_client *client)
 	mutex_init(&data->access_lock);
 	mutex_init(&data->in_alarm_lock);
 
-	ret = nct7802_init_chip(data);
+	ret = nct7802_init_chip(dev, data);
 	if (ret < 0)
 		return ret;
 
-- 
2.33.0.464.g1972c5931b-goog