[PATCH v3 7/8] dt-bindings: iio: temperature: Add ADT7604 support to adi,ltc2983

[Liviu Stan]

The ADT7604 shares the same die as the LTC2984. It repurposes the
custom RTD sensor type (18) as a copper trace resistance sensor
and the custom thermistor type (27) as a leak detector, and
removes thermocouple, diode and direct ADC sensor types.

Add adi,adt7604 to the compatible list and introduce two new
sensor node types specific to this device:

- copper-trace@: maps to the custom RTD sensor type (18). Two
variants: sub-ohm (< 1 ohm, adi,copper-trace-sub-ohm boolean,
no custom table and excitation current) and standard (> 1 ohm,
required adi,custom-copper-trace table, optional excitation current
defaulting to the datasheet recommended value). Primary output
is resistance in ohms. For > 1 ohm copper traces with a custom table,
the chip also outputs temperature in millidegrees Celsius.

- leak-detector@: maps to the custom thermistor sensor type (27).
Takes a required adi,custom-leak-detector lookup table encoding
resistance (uOhm) against coverage data (%). Two outputs:
resistance in ohms and coverage in percent.

Separate node types are used rather than extending the existing
rtd@ and thermistor@ nodes because adi,custom-rtd is required
for sensor type 18, and several properties (adi,number-of-wires,
adi,rtd-curve, adi,rsense-share, adi,single-ended,
adi,current-rotate) have no meaning for the new sensor types, since
the configuration is hardcoded, and would need to be explicitly
forbidden or ignored in the driver.

allOf conditions are added to restrict thermocouple, diode, direct
ADC and active temperature nodes to non-ADT7604 devices, and to
restrict copper-trace and leak-detector nodes to the ADT7604
(some parts only).

Signed-off-by: Liviu Stan <liviu.stan@xxxxxxxxxx>
---
Changes in v3:
- Changed the custom leak detector table encoding, users now specify
  plain coverage percentage values (0-100) in the device tree and the
  driver applies the +273.15 C offset internally before writing the
  hardware table
- Changed custom-rtd to custom-copper-trace to better represent the
  copper trace custom table, and made it required for > 1 ohm variants
- Made custom-leak-detector required for leak detector sensors
- Updated commit message to reflect the changes
- Updated leak detector node description
- Updated adi,custom-leak-detector description
- Modified the example leak detector custom table to match the datasheet

 .../bindings/iio/temperature/adi,ltc2983.yaml | 207 +++++++++++++++++-
 1 file changed, 204 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/iio/temperature/adi,ltc2983.yaml b/Documentation/devicetree/bindings/iio/temperature/adi,ltc2983.yaml
index a22725f7619b..14cfa28809ed 100644
--- a/Documentation/devicetree/bindings/iio/temperature/adi,ltc2983.yaml
+++ b/Documentation/devicetree/bindings/iio/temperature/adi,ltc2983.yaml
@@ -4,14 +4,18 @@
 $id: http://devicetree.org/schemas/iio/temperature/adi,ltc2983.yaml#
 $schema: http://devicetree.org/meta-schemas/core.yaml#
 
-title: Analog Devices LTC2983, LTC2986, LTM2985 Multi-sensor Temperature system
+title: Analog Devices LTC2983 and similar Multi-sensor Temperature systems
 
 maintainers:
   - Nuno Sá <nuno.sa@xxxxxxxxxx>
 
 description: |
-  Analog Devices LTC2983, LTC2984, LTC2986, LTM2985 Multi-Sensor Digital
-  Temperature Measurement Systems
+  Analog Devices Multi-Sensor Digital Temperature Measurement Systems:
+    - ADT7604
+    - LTC2983
+    - LTC2984
+    - LTC2986
+    - LTM2985
 
   https://www.analog.com/media/en/technical-documentation/data-sheets/2983fc.pdf
   https://www.analog.com/media/en/technical-documentation/data-sheets/2984fb.pdf
@@ -43,6 +47,7 @@ properties:
   compatible:
     oneOf:
       - enum:
+          - adi,adt7604
           - adi,ltc2983
           - adi,ltc2986
           - adi,ltm2985
@@ -436,6 +441,121 @@ patternProperties:
     required:
       - adi,custom-temp
 
+  '^copper-trace@':
+    $ref: '#/$defs/sensor-node'
+    unevaluatedProperties: false
+    description: |
+      Copper trace resistance sensor (some parts only). Two variants exist:
+      sub-ohm (< 1 ohm, no custom table allowed) and standard (> 1 ohm,
+      required custom table).
+
+    properties:
+      reg:
+        minimum: 2
+        maximum: 20
+
+      adi,sensor-type:
+        description: Sensor type for copper trace sensors.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        const: 32
+
+      adi,rsense-handle:
+        description: Associated sense resistor sensor.
+        $ref: /schemas/types.yaml#/definitions/phandle
+
+      adi,copper-trace-sub-ohm:
+        description:
+          Select the sub-ohm (< 1 ohm) copper trace variant. Custom table
+          and excitation current are not allowed in this mode.
+        type: boolean
+
+      adi,excitation-current-microamp:
+        description:
+          Excitation current applied to the copper trace. Not used in
+          sub-ohm mode. The datasheet recommends 1mA for copper trace
+          sensors due to their typically small resistance.
+        enum: [5, 10, 25, 50, 100, 250, 500, 1000]
+        default: 1000
+
+      adi,custom-copper-trace:
+        description:
+          Resistance-to-temperature table for copper trace sensors with
+          resistance > 1 ohm. Required when adi,copper-trace-sub-ohm is not
+          set. See Page 36 of the datasheet.
+        $ref: /schemas/types.yaml#/definitions/uint64-matrix
+        minItems: 3
+        maxItems: 64
+        items:
+          items:
+            - description: Resistance point in uOhms.
+            - description: Temperature point in uK.
+
+    required:
+      - adi,rsense-handle
+
+    allOf:
+      - if:
+          required:
+            - adi,copper-trace-sub-ohm
+        then:
+          properties:
+            adi,custom-copper-trace: false
+            adi,excitation-current-microamp: false
+      - if:
+          not:
+            required:
+              - adi,copper-trace-sub-ohm
+        then:
+          required:
+            - adi,custom-copper-trace
+
+  '^leak-detector@':
+    $ref: '#/$defs/sensor-node'
+    unevaluatedProperties: false
+    description: |
+      Leak detector sensor (some parts only). Outputs resistance in ohms and
+      a coverage percentage via IIO_COVERAGE (raw/1024 = coverage %).
+
+    properties:
+      reg:
+        minimum: 2
+        maximum: 20
+
+      adi,sensor-type:
+        description: Sensor type for leak detector sensors.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        const: 33
+
+      adi,rsense-handle:
+        description: Associated sense resistor sensor.
+        $ref: /schemas/types.yaml#/definitions/phandle
+
+      adi,excitation-current-nanoamp:
+        description:
+          Excitation current applied to the leak detector. The correct value
+          depends on the electrical characteristics of the liquid being sensed.
+          For example, 10000 (10µA) is recommended for PG25 (see datasheet
+          Table 39).
+        enum: [250, 500, 1000, 5000, 10000, 25000, 50000, 100000, 250000,
+               500000, 1000000]
+
+      adi,custom-leak-detector:
+        description: |
+          Lookup table mapping resistance to coverage percentage. Entries must
+          be in ascending resistance order.
+        $ref: /schemas/types.yaml#/definitions/uint64-matrix
+        minItems: 3
+        maxItems: 64
+        items:
+          items:
+            - description: Resistance point in uOhms.
+            - description: Coverage data percentage (0 to 100).
+
+    required:
+      - adi,rsense-handle
+      - adi,excitation-current-nanoamp
+      - adi,custom-leak-detector
+
   '^rsense@':
     $ref: '#/$defs/sensor-node'
     unevaluatedProperties: false
@@ -477,6 +597,22 @@ allOf:
       patternProperties:
         '^temp@': false
 
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: adi,adt7604
+    then:
+      patternProperties:
+        '^thermocouple@': false
+        '^diode@': false
+        '^adc@': false
+        '^temp@': false
+    else:
+      patternProperties:
+        '^copper-trace@': false
+        '^leak-detector@': false
+
 examples:
   - |
     #include <dt-bindings/interrupt-controller/irq.h>
@@ -556,4 +692,69 @@ examples:
             };
         };
     };
+
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        temperature-sensor@0 {
+            compatible = "adi,adt7604";
+            reg = <0>;
+            interrupt-parent = <&gpio>;
+            interrupts = <25 IRQ_TYPE_EDGE_RISING>;
+
+            #address-cells = <1>;
+            #size-cells = <0>;
+            vdd-supply = <&supply>;
+
+            trace_rsense: rsense@2 {
+                reg = <2>;
+                adi,sensor-type = <29>;
+                adi,rsense-val-milli-ohms = <100000>; // 100 ohm
+            };
+
+            copper-trace@4 {
+                reg = <4>;
+                adi,sensor-type = <32>;
+                adi,rsense-handle = <&trace_rsense>;
+                adi,copper-trace-sub-ohm;
+            };
+
+            r_sense: rsense@12 {
+                reg = <12>;
+                adi,sensor-type = <29>;
+                adi,rsense-val-milli-ohms = <1000000>; // 1 kohm
+            };
+
+            leak-detector@14 {
+                reg = <14>;
+                adi,sensor-type = <33>;
+                adi,rsense-handle = <&r_sense>;
+                adi,excitation-current-nanoamp = <10000>;
+                adi,custom-leak-detector =
+                    /bits/ 64 <          0 100>,
+                    /bits/ 64 <  202020000  99>,
+                    /bits/ 64 <  285710000  70>,
+                    /bits/ 64 <  333330000  60>,
+                    /bits/ 64 <  400000000  50>,
+                    /bits/ 64 <  500000000  40>,
+                    /bits/ 64 <  666670000  30>,
+                    /bits/ 64 < 1000000000  20>,
+                    /bits/ 64 < 2000000000  10>,
+                    /bits/ 64 <1000000000000 0>;
+            };
+
+            rtd@18 {
+                reg = <18>;
+                adi,sensor-type = <12>; // PT100
+                adi,rsense-handle = <&r_sense>;
+                adi,number-of-wires = <2>;
+                adi,rsense-share;
+                adi,excitation-current-microamp = <500>;
+                adi,rtd-curve = <0>;
+            };
+        };
+    };
 ...
-- 
2.43.0