[PATCH v4 5/8] dt-bindings: iio: adc: add ti,ads122c14

[David Lechner (TI)]

Add new bindings for ti,ads122c14 and similar devices.

This is an ADC that is primarily intended for use with resistive sensors
(RTD, thermocouple, Wheatstone bridge, etc.). There are a few unusual
properties because of this. In particular, the reference voltage source
and current output requirements can be different for each measurement,
so these are included in the channel bindings.

The REFP/REFN reference voltage is usually just connected to a resistor
that is being driven by the ADC's current outputs, so there is special
property for this case rather than requiring a regulator to be defined
to represent that.

Reviewed-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
Signed-off-by: David Lechner (TI) <dlechner@xxxxxxxxxxxx>
---
v4 changes:
* Generalize temperature sensors to resistive sensors in commit message
  and bindings description.
* Remove leftover paragraph from v1 in commit message.
* Added if to make clocks and drdy interrupts mutually exclusive.

v3 changes:
* Fixed channel@ pattern.
* Adapted to input-chopping property rename.
* Made sure to use items: on array properties.
* Added reg to required list.
* Fixed missing space in example comment.

v2 changes:
* Added ti, vendor prefix when appropriate.
* Others are now standardized properties from adc.yaml.
* Moved top-level unevaluatedProperties.
* Fixed some issues with the channel@ matching and reg property.
* Dropped description on bipolar property.
* Renamed current-chopping to input-channel-rotation.
* Drop header file and use string enum instead for reference-sources.
* Added burn-out-current-nanoamp property.
* Drop allOf: and just use oneOf: directly.
* Fix inconsistent indentation in the examples.
---
 .../devicetree/bindings/iio/adc/ti,ads112c14.yaml  | 217 +++++++++++++++++++++
 MAINTAINERS                                        |   6 +
 2 files changed, 223 insertions(+)

diff --git a/Documentation/devicetree/bindings/iio/adc/ti,ads112c14.yaml b/Documentation/devicetree/bindings/iio/adc/ti,ads112c14.yaml
new file mode 100644
index 000000000000..b11359c9955e
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/adc/ti,ads112c14.yaml
@@ -0,0 +1,217 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/ti,ads112c14.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Texas Instruments' ADS112C14 and similar ADC chips
+
+description: |
+  Supports the following Texas Instruments' ADC chips:
+  - ADS112C14 (16-bit)
+  - ADS122C14 (24-bit)
+
+  https://www.ti.com/lit/ds/symlink/ads122c14.pdf
+
+  These chips are primarily designed for use with resistive sensors such as
+  RTDs, thermocouples, Wheatstone bridges, etc. The channel bindings reflect
+  this in that each channel represents the conditions required to make a
+  measurement rather than strictly just the physical input channels.
+
+maintainers:
+  - David Lechner <dlechner@xxxxxxxxxxxx>
+
+properties:
+  compatible:
+    enum:
+      - ti,ads112c14
+      - ti,ads122c14
+
+  reg:
+    items:
+      - minimum: 0x40
+        maximum: 0x47
+
+  clocks:
+    maxItems: 1
+    description: Optional external clock connected to GPIO3 pin.
+
+  avdd-supply: true
+  dvdd-supply: true
+
+  refp-supply: true
+  refn-supply: true
+
+  ti,refp-refn-resistor-ohms:
+    description:
+      The resistance of the external resistor between REFP and REFN when using
+      resistor bridge driven by current outputs for RTD measurements.
+
+  interrupts:
+    minItems: 1
+    items:
+      - description: /FAULT interrupt (GPIO2 pin)
+      - description: /DRDY interrupt (GPIO3 pin)
+
+  interrupt-names:
+    minItems: 1
+    maxItems: 2
+    items:
+      enum: [fault, drdy]
+
+  gpio-controller: true
+  '#gpio-cells':
+    const: 2
+
+  '#address-cells':
+    const: 1
+
+  '#size-cells':
+    const: 0
+
+patternProperties:
+  ^channel@[0-9a-f]$:
+    $ref: adc.yaml
+
+    unevaluatedProperties: false
+
+    properties:
+      reg:
+        items:
+          - maximum: 15 # arbitrary limit, channel@ can be any combination of AIN0-AIN7
+
+      single-channel:
+        maximum: 7
+
+      diff-channels:
+        items:
+          maximum: 7
+
+      bipolar: true
+
+      input-chopping: true
+
+      excitation-channels:
+        maxItems: 2
+        items:
+          maximum: 7
+
+      excitation-current-nanoamp:
+        maxItems: 2
+        items:
+          enum: [1000, 10000, 20000, 30000, 40000, 50000, 60000, 70000, 80000,
+                 90000, 100000, 200000, 300000, 400000, 500000, 600000, 700000,
+                 800000, 900000, 1000000]
+
+      burn-out-current-nanoamp:
+        items:
+          - enum: [200, 1000, 10000]
+
+      reference-sources:
+        items:
+          - enum: [internal-2.5v, internal-1.25v, external, avdd]
+            default: internal-2.5v
+
+    dependencies:
+      excitation-channels: [ excitation-current-nanoamp ]
+      excitation-current-nanoamp: [ excitation-channels ]
+
+    oneOf:
+      - required: [ single-channel ]
+      - required: [ diff-channels ]
+
+unevaluatedProperties: false
+
+required:
+  - compatible
+  - reg
+  - avdd-supply
+  - dvdd-supply
+
+dependencies:
+  refn-supply: [ refp-supply ]
+
+oneOf:
+  - required: [ refp-supply ]
+  - required: [ "ti,refp-refn-resistor-ohms" ]
+  - properties:
+      refp-supply: false
+      refn-supply: false
+      ti,refp-refn-resistor-ohms: false
+
+# /DRDY out and CLK in use the same AIN7/GPIO3 pin.
+if:
+  properties:
+    interrupt-names:
+      contains:
+        const: drdy
+then:
+  properties:
+    clocks: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        adc@40 {
+            compatible = "ti,ads112c14";
+            reg = <0x40>;
+
+            avdd-supply = <&avdd>;
+            dvdd-supply = <&dvdd>;
+
+            /* 3-Wire RTD: Two IDACs, One Measurement (AIN1-AIN2) */
+
+            ti,refp-refn-resistor-ohms = <500>;
+
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            channel@0 {
+                reg = <0>;
+                diff-channels = <1>, <2>;
+                input-chopping;
+                excitation-channels = <0>, <3>;
+                excitation-current-nanoamp = <500000>, <500000>;
+                reference-sources = "external";
+                label = "rtd";
+            };
+        };
+    };
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        adc@40 {
+            compatible = "ti,ads112c14";
+            reg = <0x40>;
+
+            avdd-supply = <&avdd>;
+            dvdd-supply = <&dvdd>;
+
+            /* Resistive Bridge Measurement With a Thermistor for Temperature Compensation */
+
+            refp-supply = <&avdd>;
+
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            channel@0 {
+                reg = <0>;
+                diff-channels = <6>, <7>;
+                bipolar;
+                reference-sources = "external";
+                label = "bridge";
+            };
+
+            channel@1 {
+                reg = <1>;
+                diff-channels = <1>, <2>;
+                reference-sources = "internal-2.5v";
+                label = "thermistor";
+            };
+        };
+    };
diff --git a/MAINTAINERS b/MAINTAINERS
index 2b1ec46c5919..3e114e0c9c5f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -26958,6 +26958,12 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/iio/adc/ti,ads1119.yaml
 F:	drivers/iio/adc/ti-ads1119.c
 
+TI ADS112C14 ADC DRIVER
+M:	David Lechner <dlechner@xxxxxxxxxxxx>
+L:	linux-iio@xxxxxxxxxxxxxxx
+S:	Maintained
+F:	Documentation/devicetree/bindings/iio/adc/ti,ads112c14.yaml
+
 TI ADS1018 ADC DRIVER
 M:	Kurt Borja <kuurtb@xxxxxxxxx>
 L:	linux-iio@xxxxxxxxxxxxxxx

-- 
2.43.0