linux-kernel - Re: [PATCH v3 1/2] dt-bindings: iio: temperature: add support for MCP998X

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Message-ID: <20250613-undergo-reviving-a97dca8f3b69@spud>
Date: Fri, 13 Jun 2025 15:40:21 +0100
From: Conor Dooley <conor@...nel.org>
To: victor.duicu@...rochip.com
Cc: jic23@...nel.org, dlechner@...libre.com, nuno.sa@...log.com,
	andy@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
	conor+dt@...nel.org, marius.cristea@...rochip.com,
	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v3 1/2] dt-bindings: iio: temperature: add support for
 MCP998X

On Fri, Jun 13, 2025 at 04:02:06PM +0300, victor.duicu@...rochip.com wrote:
> From: Victor Duicu <victor.duicu@...rochip.com>
> 
> This is the devicetree schema for Microchip MCP998X/33 and
> MCP998XD/33D Automotive Temperature Monitor Family.
> 
> Signed-off-by: Victor Duicu <victor.duicu@...rochip.com>
> ---
>  .../iio/temperature/microchip,mcp9982.yaml    | 211 ++++++++++++++++++
>  1 file changed, 211 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..ec939d463612
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/temperature/microchip,mcp9982.yaml
> @@ -0,0 +1,211 @@
> +# 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@...rochip.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
> +
> +  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.
> +    items:
> +      - const: alert-therm
> +      - const: therm-addr
> +      - const: sys-shutdown
> +
> +  "#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,beta1:
> +    description:
> +      Set beta compensation value for external channel 1.
> +      <0> 0.050
> +      <1> 0.066
> +      <2> 0.087
> +      <3> 0.114
> +      <4> 0.150
> +      <5> 0.197
> +      <6> 0.260
> +      <7> 0.342
> +      <8> 0.449
> +      <9> 0.591
> +      <10> 0.778
> +      <11> 1.024
> +      <12> 1.348
> +      <13> 1.773
> +      <14> 2.333
> +      <15> Diode_Mode
> +      <16> Auto
> +      - Diode_Mode is used when measuring a discrete thermal diode
> +      or a CPU diode that functions like a discrete thermal diode.
> +      - Auto enables beta auto-detection. The chip monitors
> +      external diode/transistor and determines the optimum
> +      setting.
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    default: 16

Missing max/min constraints on the property.

> +
> +  microchip,beta2:
> +    description:
> +      Set beta compensation value for external channel 2.
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    default: 16
> +
> +  microchip,resistance-comp-ch1-2-enable:
> +    description:
> +      Enable resistance error correction(REC) for external channels 1 and 2.
> +      The chip internal hardware counterbalances the parasitic resistance in
> +      series with the external diodes. The compensation can be activated or
> +      disabled in hardware for both channels 1 and 2 at the same time.
> +    type: boolean

On the previous version I objected to this wording for the property,
where it is being used as an enable, and instead said that it should
indicate the presence of the parasitic resistance. Did I miss some sort
of new justification for it still talking about being an enable?


> +  microchip,resistance-comp-ch3-4-enable:
> +    description:
> +      Enable resistance error correction(REC) for external channels 3 and 4.
> +      The chip internal hardware counterbalances the parasitic resistance in
> +      series with the external diodes. The compensation can be activated or
> +      disabled in hardware for both channels 3 and 4 at the same time.
> +    type: boolean

Cheers,
Conor.

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