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Message-ID: <1aa4d7d1-be47-471a-8411-1adaffc1659f@baylibre.com>
Date: Fri, 29 Aug 2025 12:39:31 -0500
From: David Lechner <dlechner@...libre.com>
To: victor.duicu@...rochip.com, jic23@...nel.org, nuno.sa@...log.com,
andy@...nel.org, robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org
Cc: marius.cristea@...rochip.com, linux-iio@...r.kernel.org,
linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v4 1/2] dt-bindings: iio: temperature: add support for
MCP998X
On 8/29/25 9:34 AM, victor.duicu@...rochip.com wrote:
> From: Victor Duicu <victor.duicu@...rochip.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@...rochip.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@...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
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";
> + };
> + };
> + };
> +
> +...
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