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Message-ID: <20250530-dramatize-camisole-0a1aa9a38281@spud>
Date: Fri, 30 May 2025 16:55:16 +0100
From: Conor Dooley <conor@...nel.org>
To: David Lechner <dlechner@...libre.com>
Cc: 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, marius.cristea@...rochip.com,
linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
devicetree@...r.kernel.org
Subject: Re: [PATCH v2 1/2] dt-bindings: iio: temperature: add support for
MCP998X
On Thu, May 29, 2025 at 01:13:38PM -0500, David Lechner wrote:
> On 5/29/25 4:36 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 | 174 ++++++++++++++++++
> > 1 file changed, 174 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..249470c8953b
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/iio/temperature/microchip,mcp9982.yaml
> > @@ -0,0 +1,174 @@
> > +# 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:
> > + maxItems: 2
> > +
> > + interrupt-names:
> > + description:
> > + alert1 indicates a HIGH or LOW limit was exceeded.
> > + alert2 indicates a THERM limit was exceeded.
>
> I think we need minItems: 1 here.
>
> > + items:
> > + - const: alert1
> > + - const: alert2
>
> Typically, interrupts are named after the pin they are wired to, not
> the signal. This is especially true when a single pin can be configured
> for different signals as is the case here.
>
> There is a /ALERT//THERM pin on all chips and a /THERM//ADDR pin on some
> chips.
>
> So I would expect the names to match that:
>
> items:
> - const: alert-therm
> - const: therm-addr
>
> And then extra descriptions probably aren't needed.
>
> If we want to be extra careful, we could also add an -if: below to set
> maxItems: 1 for interrupts and interrupt-names on chips that only have
> the one pin.
>
> And I assume that the /SYS_SHDN pin would never be wired up as an interrupt?
>
> > +
> > + "#address-cells":
> > + const: 1
> > +
> > + "#size-cells":
> > + const: 0
> > +
> > + microchip,apdd-state:
> > + 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.
> > + Omit this tag to disable anti-parallel diode mode.
> > + type: boolean
> > +
> > + microchip,recd12:
> > + description:
> > + Enable resistance error correction for external channels 1 and 2.
> > + Omit this tag to disable REC for channels 1 and 2.
> > + type: boolean
> > +
> > + microchip,recd34:
> > + description:
> > + Enable resistance error correction for external channels 3 and 4.
> > + Omit this tag to disable REC for channels 3 and 4.
Why are these two devicetree properties, rather than runtime controls?
> > + type: boolean
> > +
> > + label:
> > + description: Unique name to identify which device this is.
> > +
> > + 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.
> > + Omit this tag in order to set the default value.
> > + $ref: /schemas/types.yaml#/definitions/uint32
> > + default: 18
> > +
> > + 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,mcp9982
> > + - microchip,mcp9982d
> > + - microchip,mcp9983
> > + - microchip,mcp9983d
> > + then:
> > + properties:
> > + microchip,apdd-state: false
> > + - if:
> > + properties:
> > + compatible:
> > + contains:
> > + enum:
> > + - microchip,mcp9982
> > + - microchip,mcp9982d
> > + - microchip,mcp9933
> > + - microchip,mcp9933d
> > + then:
> > + properties:
> > + microchip,recd34: false
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > + - |
> > + i2c {
> > + #address-cells = <1>;
> > + #size-cells = <0>;
> > +
> > + temperature-sensor@4c {
> > + compatible = "microchip,mcp9985";
> > + reg = <0x4c>;
> > +
> > + #address-cells = <1>;
> > + #size-cells = <0>;
> > +
> > + label = "temperature-sensor";
>
> This is the same as the node name, so probably not the best
> example of a label.
Ye, I'm not convinced this property has any value, when the channels
themselves can have labels.
>
> > +
> > + microchip,apdd-state;
> > + microchip,recd12;
> > + microchip,recd34;
> > + vdd-supply = <&vdd>;
> > +
> > + channel@1 {
> > + reg = <0x1>;
>
> Why 0x here?
>
> > + label = "CPU Temperature";
> > + };
> > +
> > + channel@2 {
> > + reg = <0x2>;
> > + label = "GPU Temperature";
> > + };
> > + };
> > + };
> > +
> > +...
>
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