dt-bindings: hwmon: Add nct7802 bindings

This change allows LTD and RTD inputs to be configured via device tree bindings. If the DT bindings are not present or invalid, the input configuration is not modified and left at HW defaults.

Signed-off-by Oskar Senft <[email protected]>

Reviewed-by Guenter Roeck <[email protected]>

---
Changes from PATCH v6 and v7:
- None (resubmitted due to changes in nuvoton,nct7802.yaml).

Changes from PATCH v5:
- Removed unused "found_channel_config" variable.
- Initialize mode_mask and mode_val to defaults.

---
 drivers/hwmon/nct7802.c | 129 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 125 insertions(+), 4 deletions(-)

drivers/hwmon/nct7802.c +125 -4

index 604af2f6103a..d56f78327619 100644
@@ -51,6 +51,23 @@ 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 RTD_MODE_CURRENT	0x1
+#define RTD_MODE_THERMISTOR	0x2
+#define RTD_MODE_VOLTAGE	0x3
+
+#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
  */

@@ -1038,7 +1055,112 @@ 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_get_channel_config(struct device *dev,
+				      struct device_node *node, u8 *mode_mask,
+				      u8 *mode_val)
+{
+	u32 reg;
+	const char *type_str, *md_str;
+	u8 md;
+
+	if (!node->name || of_node_cmp(node->name, "channel"))
+		return 0;
+
+	if (of_property_read_u32(node, "reg", &reg)) {
+		dev_err(dev, "Could not read reg value for '%s'\n",
+			node->full_name);
+		return -EINVAL;
+	}
+
+	if (reg > 3) {
+		dev_err(dev, "Invalid reg (%u) in '%s'\n", reg,
+			node->full_name);
+		return -EINVAL;
+	}
+
+	if (reg == 0) {
+		if (!of_device_is_available(node))
+			*mode_val &= ~MODE_LTD_EN;
+		else
+			*mode_val |= MODE_LTD_EN;
+		*mode_mask |= MODE_LTD_EN;
+		return 0;
+	}
+
+	/* At this point we have reg >= 1 && reg <= 3 */
+
+	if (!of_device_is_available(node)) {
+		*mode_val &= ~(MODE_RTD_MASK << MODE_BIT_OFFSET_RTD(reg - 1));
+		*mode_mask |= MODE_RTD_MASK << MODE_BIT_OFFSET_RTD(reg - 1);
+		return 0;
+	}
+
+	if (of_property_read_string(node, "sensor-type", &type_str)) {
+		dev_err(dev, "No type for '%s'\n", node->full_name);
+		return -EINVAL;
+	}
+
+	if (!strcmp(type_str, "voltage")) {
+		*mode_val |= (RTD_MODE_VOLTAGE & MODE_RTD_MASK)
+			     << MODE_BIT_OFFSET_RTD(reg - 1);
+		*mode_mask |= MODE_RTD_MASK << MODE_BIT_OFFSET_RTD(reg - 1);
+		return 0;
+	}
+
+	if (strcmp(type_str, "temperature")) {
+		dev_err(dev, "Invalid type '%s' for '%s'\n", type_str,
+			node->full_name);
+		return -EINVAL;
+	}
+
+	if (reg == 3) {
+		/* RTD3 only supports thermistor mode */
+		md = RTD_MODE_THERMISTOR;
+	} else {
+		if (of_property_read_string(node, "temperature-mode",
+					    &md_str)) {
+			dev_err(dev, "No mode for '%s'\n", node->full_name);
+			return -EINVAL;
+		}
+
+		if (!strcmp(md_str, "thermal-diode"))
+			md = RTD_MODE_CURRENT;
+		else if (!strcmp(md_str, "thermistor"))
+			md = RTD_MODE_THERMISTOR;
+		else {
+			dev_err(dev, "Invalid mode '%s' for '%s'\n", md_str,
+				node->full_name);
+			return -EINVAL;
+		}
+	}
+
+	*mode_val |= (md & MODE_RTD_MASK) << MODE_BIT_OFFSET_RTD(reg - 1);
+	*mode_mask |= MODE_RTD_MASK << MODE_BIT_OFFSET_RTD(reg - 1);
+
+	return 0;
+}
+
+static int nct7802_configure_channels(struct device *dev,
+				      struct nct7802_data *data)
+{
+	/* Enable local temperature sensor by default */
+	u8 mode_mask = MODE_LTD_EN, mode_val = MODE_LTD_EN;
+	struct device_node *node;
+	int err;
+
+	if (dev->of_node) {
+		for_each_child_of_node(dev->of_node, node) {
+			err = nct7802_get_channel_config(dev, node, &mode_mask,
+							 &mode_val);
+			if (err)
+				return err;
+		}
+	}
+
+	return regmap_update_bits(data->regmap, REG_MODE, mode_mask, mode_val);
+}
+
+static int nct7802_init_chip(struct device *dev, struct nct7802_data *data)
 {
 	int err;
 

@@ -1047,8 +1169,7 @@ 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);
+	err = nct7802_configure_channels(dev, data);
 	if (err)
 		return err;
 

@@ -1074,7 +1195,7 @@ 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;
 

This change documents the device tree bindings for the Nuvoton NCT7802Y driver.

Signed-off-by Oskar Senft <[email protected]>

---
Changes from PATCH v7:
- Implemented review comments:
- Added blank lines to increase readability.
- Moved "additionalProperties" up to increase readability.

Changes from PATCH v6:
- Fixed formatting error reported by yamllint

Changes from PATCH v5:
- Refactored to use patternProperties.
- Added validation for sensor-type and temperature-mode.

---
 .../bindings/hwmon/nuvoton,nct7802.yaml       | 145 ++++++++++++++++++
 1 file changed, 145 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/nuvoton,nct7802.yaml

This change documents the device tree bindings for the Nuvoton NCT7802Y driver.

Signed-off-by Oskar Senft <[email protected]>

Reviewed-by Rob Herring <[email protected]>

---
Changes from PATCH v7:
- Implemented review comments:
- Added blank lines to increase readability.
- Moved "additionalProperties" up to increase readability.

Changes from PATCH v6:
- Fixed formatting error reported by yamllint

Changes from PATCH v5:
- Refactored to use patternProperties.
- Added validation for sensor-type and temperature-mode.

---
 .../bindings/hwmon/nuvoton,nct7802.yaml       | 145 ++++++++++++++++++
 1 file changed, 145 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/nuvoton,nct7802.yaml

Documentation/devicetree/bindings/hwmon/nuvoton,nct7802.yaml new file +145 -0

new file mode 100644
index 000000000000..2f0620ecccc9
@@ -0,0 +1,145 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+
+$id: http://devicetree.org/schemas/hwmon/nuvoton,nct7802.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Nuvoton NCT7802Y Hardware Monitoring IC
+
+maintainers:
+  - Guenter Roeck <[email protected]>
+
+description: |
+  The NCT7802Y is a hardware monitor IC which supports one on-die and up to
+  5 remote temperature sensors with SMBus interface.
+
+  Datasheets:
+    https://www.nuvoton.com/export/resource-files/Nuvoton_NCT7802Y_Datasheet_V12.pdf
+
+additionalProperties: false
+
+properties:
+  compatible:
+    enum:
+      - nuvoton,nct7802
+
+  reg:
+    maxItems: 1
+
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    const: 0
+
+patternProperties:
+  "^channel@[0-3]$":
+    type: object
+
+    additionalProperties: false
+
+    properties:
+      reg:
+        items:
+          - enum:
+              - 0    # Local Temperature Sensor ("LTD")
+              - 1    # Remote Temperature Sensor or Voltage Sensor 1 ("RTD1")
+              - 2    # Remote Temperature Sensor or Voltage Sensor 2 ("RTD2")
+              - 3    # Remote Temperature Sensor or Voltage Sensor 3 ("RTD3")
+
+      sensor-type:
+        items:
+          - enum:
+              - temperature
+              - voltage
+
+      temperature-mode:
+        items:
+          - enum:
+              - thermistor
+              - thermal-diode
+
+    required:
+      - reg
+
+    allOf:
+      # For channels RTD1, RTD2 and RTD3, require sensor-type to be set.
+      # Otherwise (for all other channels), do not allow temperature-mode to be
+      # set.
+      - if:
+          properties:
+            reg:
+              items:
+                - enum:
+                    - 1
+                    - 2
+                    - 3
+        then:
+          required:
+            - sensor-type
+        else:
+          not:
+            required:
+              - sensor-type
+
+      # For channels RTD1 and RTD2 and if sensor-type is "temperature", require
+      # temperature-mode to be set. Otherwise (for all other channels or
+      # sensor-type settings), do not allow temperature-mode to be set
+      - if:
+          properties:
+            reg:
+              items:
+                - enum:
+                    - 1
+                    - 2
+            sensor-type:
+              items:
+                - enum:
+                    - temperature
+        then:
+          required:
+            - temperature-mode
+        else:
+          not:
+            required:
+              - temperature-mode
+
+required:
+  - compatible
+  - reg
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        nct7802@28 {
+            compatible = "nuvoton,nct7802";
+            reg = <0x28>;
+
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            channel@0 { /* LTD */
+              reg = <0>;
+            };
+
+            channel@1 { /* RTD1 */
+              reg = <1>;
+              sensor-type = "voltage";
+            };
+
+            channel@2 { /* RTD2 */
+              reg = <2>;
+              sensor-type = "temperature";
+              temperature-mode = "thermal-diode";
+            };
+
+            channel@3 { /* RTD3 */
+              reg = <3>;
+              sensor-type = "temperature";
+            };
+        };
+    };