Re: [PATCH 1/2] dt-bindings: iio: temperature: Add ADT7604 support to adi,ltc2983

[Conor Dooley <conor@kernel.org>]

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On Mon, Apr 27, 2026 at 04:25:07PM +0300, Liviu Stan wrote:
> 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.

I have to wonder if this is the right approach, if it's the same device
just with a different label and advertised purpose.

> 
> 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 standard (> 1 ohm, optional adi,custom-rtd
>   table). Primary output is resistance in mOhm.
> 
> - leak-detector@: maps to the custom thermistor sensor type (27).
>   Takes an optional adi,custom-leak-detector lookup table encoding
>   resistance (uOhm) against coverage data (P + 273.15 in uK).
>   Primary output is resistance in Ohm; when a table is provided,
>   IIO_TEMP reports coverage percentage (raw / 1024).
> 
> 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.
> 
> Signed-off-by: Liviu Stan <liviu.stan@analog.com>
> ---
>  .../bindings/iio/temperature/adi,ltc2983.yaml | 170 +++++++++++++++++-
>  1 file changed, 167 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..e777b37d588d 100644
> --- a/Documentation/devicetree/bindings/iio/temperature/adi,ltc2983.yaml
> +++ b/Documentation/devicetree/bindings/iio/temperature/adi,ltc2983.yaml
> @@ -4,14 +4,14 @@
>  $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, LTC2986, LTM2985, ADT7604 Multi-sensor Temperature system
>  
>  maintainers:
>    - Nuno Sá <nuno.sa@analog.com>
>  
>  description: |
> -  Analog Devices LTC2983, LTC2984, LTC2986, LTM2985 Multi-Sensor Digital
> -  Temperature Measurement Systems
> +  Analog Devices LTC2983, LTC2984, LTC2986, LTM2985, ADT7604 Multi-Sensor
> +  Digital Temperature Measurement Systems
>  
>    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 +43,7 @@ properties:
>    compatible:
>      oneOf:
>        - enum:
> +          - adi,adt7604
>            - adi,ltc2983
>            - adi,ltc2986
>            - adi,ltm2985
> @@ -436,6 +437,96 @@ patternProperties:
>      required:
>        - adi,custom-temp
>  
> +  '^copper-trace@':

Pedantry perhaps, but isn't this an "ohmmeter"?

> +    $ref: '#/$defs/sensor-node'
> +    unevaluatedProperties: false
> +    description: |
> +      Copper trace resistance sensor (ADT7604 only). Uses the custom RTD
> +      sensor type (18). Two variants exist: sub-ohm (< 1 ohm, no custom
> +      table allowed) and standard (> 1 ohm, optional 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: 18
> +
> +      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,custom-rtd:
> +        description:
> +          Optional resistance-to-temperature table for copper trace sensors
> +          with resistance > 1 ohm. See Page 62 of the datasheet.

I want to look into this property, where is 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-rtd: false
> +
> +  '^leak-detector@':
> +    $ref: '#/$defs/sensor-node'
> +    unevaluatedProperties: false
> +    description: |
> +      Leak detector sensor (ADT7604 only). Uses the custom thermistor sensor
> +      type (27). Outputs resistance in ohms and, when a custom table is
> +      provided, a coverage percentage via IIO_TEMP (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: 27
> +
> +      adi,rsense-handle:
> +        description: Associated sense resistor sensor.
> +        $ref: /schemas/types.yaml#/definitions/phandle
> +
> +      adi,custom-leak-detector:
> +        description: |
> +          Lookup table mapping resistance to coverage data. Entries must be
> +          in ascending resistance order. The coverage data field encodes the
> +          coverage percentage P as (P + 273.15) expressed in uK, i.e.
> +          (P * 1000000 + 273150000).
> +        $ref: /schemas/types.yaml#/definitions/uint64-matrix
> +        minItems: 3
> +        maxItems: 64
> +        items:
> +          items:
> +            - description: Resistance point in uOhms.
> +            - description: Coverage data point (P + 273150000) in uK.
> +
> +    required:
> +      - adi,rsense-handle
> +
>    '^rsense@':
>      $ref: '#/$defs/sensor-node'
>      unevaluatedProperties: false
> @@ -477,6 +568,22 @@ 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 +663,61 @@ 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 = <18>;
> +                adi,rsense-handle = <&trace_rsense>;

Are these ever linked in a different way?

> +                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 = <27>;
> +                adi,rsense-handle = <&r_sense>;

Ditto here and in the rtd node. Are these fixed linkages or actually
dynamic?

Cheers,
Conor.

> +                adi,custom-leak-detector =
> +                    /bits/ 64 <          0 373150000>,
> +                    /bits/ 64 <  202020000 372150000>,
> +                    /bits/ 64 < 1000000000 293150000>;
> +            };
> +
> +            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
> 

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