Re: [PATCH v4 1/2] dt-bindings: iio: temperature: add support for MCP998X

[David Lechner <dlechner@baylibre.com>]

On 8/29/25 9:34 AM, victor.duicu@microchip.com wrote:
> From: Victor Duicu <victor.duicu@microchip.com>
> 
> This is the devicetree schema for Microchip MCP998X/33 and MCP998XD/33D
> Multichannel Automotive Temperature Monitor Family.
> 
> Signed-off-by: Victor Duicu <victor.duicu@microchip.com>
> ---
>  .../iio/temperature/microchip,mcp9982.yaml    | 203 ++++++++++++++++++
>  1 file changed, 203 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/temperature/microchip,mcp9982.yaml
> 
> diff --git a/Documentation/devicetree/bindings/iio/temperature/microchip,mcp9982.yaml b/Documentation/devicetree/bindings/iio/temperature/microchip,mcp9982.yaml
> new file mode 100644
> index 000000000000..2f092e376fe8
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/temperature/microchip,mcp9982.yaml
> @@ -0,0 +1,203 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/temperature/microchip,mcp9982.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Microchip MCP998X/33 and MCP998XD/33D Multichannel Automotive
> +       Temperature Monitor Family
> +
> +maintainers:
> +  - Victor Duicu <victor.duicu@microchip.com>
> +
> +description: |
> +  The MCP998X/33 and MCP998XD/33D family is a high-accuracy 2-wire multichannel
> +  automotive temperature monitor.
> +  The datasheet can be found here:
> +    https://ww1.microchip.com/downloads/aemDocuments/documents/MSLD/ProductDocuments/DataSheets/MCP998X-Family-Data-Sheet-DS20006827.pdf
> +
> +properties:
> +  compatible:
> +    enum:
> +      - microchip,mcp9933
> +      - microchip,mcp9933d
> +      - microchip,mcp9982
> +      - microchip,mcp9982d
> +      - microchip,mcp9983
> +      - microchip,mcp9983d
> +      - microchip,mcp9984
> +      - microchip,mcp9984d
> +      - microchip,mcp9985
> +      - microchip,mcp9985d
> +
> +  reg:
> +    maxItems: 1
> +
> +  interrupts:
> +    minItems: 2
> +    maxItems: 2

Why can't we just have one of the interrupt pins wired up?

> +
> +  interrupt-names:
> +    description:
> +      -alert-therm is used to handle a HIGH or LOW limit.
> +      -therm-addr is used to handle a THERM limit on chips
> +      without "D" in the name.
> +      -sys-shutdown is used to handle a THERM limit on chips
> +      with "D" in the name.

Descriptions can be moved below:

> +    items:
> +      - const: alert-therm
           description: Interrupt line connected to the ALERT/THERM pin.
> +      - const: therm-addr
           description: ...
> +      - const: sys-shutdown
           description: ...

The device tree only cares how things are wired, not how they are used
so I suggested a different description.

> +
> +  "#address-cells":
> +    const: 1
> +
> +  "#size-cells":
> +    const: 0
> +
> +  microchip,enable-anti-parallel:
> +    description:
> +      Enable anti-parallel diode mode operation.
> +      MCP9984/84D/85/85D and MCP9933/33D support reading two external diodes
> +      in anti-parallel connection on the same set of pins.
> +    type: boolean
> +
> +  microchip,parasitic-res-on-channel1-2:
> +    description:
> +      Indicates that the chip and the diodes/transistors are sufficiently far
> +      apart that a parasitic resistance is added to the wires, which can affect
> +      the measurements. Due to the anti-parallel diode connections, channels
> +      1 and 2 are affected together.
> +    type: boolean
> +
> +  microchip,parasitic-res-on-channel3-4:
> +    description:
> +      Indicates that the chip and the diodes/transistors are sufficiently far
> +      apart that a parasitic resistance is added to the wires, which can affect
> +      the measurements. Due to the anti-parallel diode connections, channels
> +      3 and 4 are affected together.
> +    type: boolean
> +
> +  vdd-supply: true
> +
> +patternProperties:
> +  "^channel@[1-4]$":
> +    description:
> +      Represents the external temperature channels to which
> +      a remote diode is connected.
> +    type: object
> +
> +    properties:
> +      reg:
> +        items:
> +          minimum: 1
> +          maximum: 4
> +
> +      microchip,ideality-factor:
> +        description:
> +          Each channel has an ideality factor.
> +          Beta compensation and resistance error correction automatically
> +          correct for most ideality errors. So ideality factor does not need
> +          to be adjusted in general.
> +        $ref: /schemas/types.yaml#/definitions/uint32
> +        default: 18

Are there minimum and maximum values?

> +
> +      label:
> +        description: Unique name to identify which channel this is.
> +
> +    required:
> +      - reg
> +
> +    additionalProperties: false
> +
> +required:
> +  - compatible
> +  - reg
> +  - vdd-supply
> +
> +allOf:
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            enum:
> +              - microchip,mcp9982d
> +              - microchip,mcp9983d
> +              - microchip,mcp9984d
> +              - microchip,mcp9985d
> +              - microchip,mcp9933d

Could use a pattern instead of listing all matches.

		pattern: .+d$

> +    then:
> +      properties:
> +        interrupts-names:
> +          items:
> +            - const: alert-therm
> +            - const: sys-shutdown
> +    else:
> +      properties:
> +        interrupts-names:
> +          items:
> +            - const: alert-therm
> +            - const: therm-addr
> +
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            enum:
> +              - microchip,mcp9982
> +              - microchip,mcp9983
> +              - microchip,mcp9982d
> +              - microchip,mcp9983d
> +    then:
> +      properties:
> +        microchip,enable-anti-parallel: false
> +
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            enum:
> +              - microchip,mcp9982d
> +              - microchip,mcp9983d
> +              - microchip,mcp9984d
> +              - microchip,mcp9985d
> +              - microchip,mcp9933d

This looks like the same "if" as above, so could be combined.

> +    then:
> +      properties:
> +        microchip,parasitic-res-on-channel1-2: false
> +        microchip,parasitic-res-on-channel3-4: false

> +        microchip,ideality-factor: false

microchip,ideality-factor is a channel property, so this has no effect.
It needs to be moved to the correct place under patternProperties.

> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    i2c {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        temperature-sensor@4c {
> +            compatible = "microchip,mcp9985";
> +            reg = <0x4c>;
> +
> +            #address-cells = <1>;
> +            #size-cells = <0>;
> +
> +            microchip,enable-anti-parallel;
> +            microchip,parasitic-res-on-channel1-2;
> +            microchip,parasitic-res-on-channel3-4;
> +            vdd-supply = <&vdd>;
> +
> +            channel@1 {
> +                reg = <1>;
> +                label = "CPU Temperature";
> +            };
> +
> +            channel@2 {
> +                reg = <2>;
> +                label = "GPU Temperature";
> +            };
> +        };
> +    };
> +
> +...