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Message-ID: <a83b48a4-76ba-48df-9aba-adb018949914@roeck-us.net>
Date: Thu, 5 Feb 2026 11:18:25 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Marius Cristea <marius.cristea@...rochip.com>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>,
Jonathan Corbet <corbet@....net>, linux-hwmon@...r.kernel.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-doc@...r.kernel.org,
Conor Dooley <conor.dooley@...rochip.com>
Subject: Re: [PATCH v5 1/2] dt-bindings: hwmon: temperature: add support for
EMC1812
On Thu, Feb 05, 2026 at 09:09:03AM +0200, Marius Cristea wrote:
> This is the devicetree schema for Microchip EMC1812/13/14/15/33
> Multichannel Low-Voltage Remote Diode Sensor Family.
>
> EMC1812 has one external remote temperature monitoring channel.
> EMC1813 has two external remote temperature monitoring channels.
> EMC1814 has three external remote temperature monitoring channels and
> channels 2 and 3 supports anti parallel diode.
> EMC1815 has four external remote temperature monitoring channels and
> channels 1/2 and 3/4 supports anti parallel diode.
> EMC1833 has two external remote temperature monitoring channels and
> channels 1 and 2 supports anti parallel diode.
>
> Signed-off-by: Marius Cristea <marius.cristea@...rochip.com>
> Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>
> ---
> .../bindings/hwmon/microchip,emc1812.yaml | 182 +++++++++++++++++++++
> MAINTAINERS | 6 +
> 2 files changed, 188 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/hwmon/microchip,emc1812.yaml b/Documentation/devicetree/bindings/hwmon/microchip,emc1812.yaml
> new file mode 100644
> index 0000000000000000000000000000000000000000..759e004eafdfc0772e110fe484767eb66a623294
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/hwmon/microchip,emc1812.yaml
> @@ -0,0 +1,182 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/hwmon/microchip,emc1812.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Microchip EMC1812/13/14/15/33 multichannel temperature sensor
> +
> +maintainers:
> + - Marius Cristea <marius.cristea@...rochip.com>
> +
> +description: |
> + The Microchip EMC1812/13/14/15/33 is a high-accuracy 2-wire multichannel
> + low-voltage remote diode temperature monitor.
> +
> + The datasheet can be found here:
> + https://ww1.microchip.com/downloads/aemDocuments/documents/MSLD/ProductDocuments/DataSheets/EMC1812-3-4-5-33-Data-Sheet-DS20005751.pdf
> +
> + EMC1812 has one external remote temperature monitoring channel
> + EMC1813 has two external remote temperature monitoring channels
> + EMC1814 has three external remote temperature monitoring channels and
> + channels 2 and 3 supports anti parallel diode
> + EMC1815 has four external remote temperature monitoring channels and
> + channels 1/2 and 3/4 supports anti parallel diode
> + EMC1833 has two external remote temperature monitoring channels and
> + channels 1 and 2 supports anti parallel diode
> +
> +properties:
> + compatible:
> + enum:
> + - microchip,emc1812
> + - microchip,emc1813
> + - microchip,emc1814
> + - microchip,emc1815
> + - microchip,emc1833
> +
> + reg:
> + maxItems: 1
> +
> + interrupts:
> + items:
> + - description: alert-therm2 asserts when the ALERT limit is exceeded.
> + - description: therm-addr asserts when the THERM limit is exceeded.
> + minItems: 1
> +
> + interrupt-names:
> + items:
> + - enum: [alert-therm2, therm-addr]
AI feedback:
If interrupt names are being used to identify the interrupts, should
the interrupts property be less restrictive?
Currently, the items list in interrupts enforces a strict order:
the first interrupt must match the first description (alert-therm2),
and the second must match the second description (therm-addr).
However, the interrupt-names definition for the first item allows it
to be "therm-addr".
If the intention is to support providing only the second interrupt (therm-addr)
as the first item in the list, then the interrupts property definition
prevents that by enforcing the first item to be alert-therm2.
2nd feedback:
The interrupts property description lists two possible interrupts ("alert-therm2"
and "therm-addr"), but this definition restricts interrupt-names to a single
item.
Should this be updated to allow providing names for both interrupts if the
device is configured with both?
[ I don't know how this is supposed to work, so the feedback needs to be taken
with two grains of salt. ]
> +
> + "#address-cells":
> + const: 1
> +
> + "#size-cells":
> + const: 0
> +
> + 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]$":
> + description:
> + Represents the external temperature channels to which
> + a remote diode is connected.
> + type: object
> +
> + properties:
> + reg:
> + items:
> + minimum: 1
> + maximum: 4
I (or, rather, AI review) asked this before:
Does this reg property need maxItems: 1?
Without it, the schema might allow reg properties with multiple items,
provided the first item is within the minimum/maximum range.
[ Presumably the _values_ should be 1..4, not the number of items ]
> +
> + label:
> + description: Unique name to identify which channel this is.
> +
> + required:
> + - reg
> +
> + additionalProperties: false
> +
> +required:
> + - compatible
> + - reg
> + - vdd-supply
> +
> +allOf:
> + - if:
> + properties:
> + compatible:
> + contains:
> + enum:
> + - microchip,emc1812
> + - microchip,emc1813
> + - microchip,emc1833
> + then:
> + properties:
> + microchip,parasitic-res-on-channel3-4: false
> + - if:
> + properties:
> + compatible:
> + contains:
> + enum:
> + - microchip,emc1812
> + then:
> + properties:
> + channel@1:
> + properties:
> + reg:
> + items:
> + const: 1
> + patternProperties:
> + "^channel@[2-4]$": false
> + - if:
> + properties:
> + compatible:
> + pattern: "^microchip,emc18[13]3"
> + then:
> + patternProperties:
> + "^channel@[12]$":
> + properties:
> + reg:
> + items:
> + maximum: 2
> + "^channel@[34]$": false
> + - if:
> + properties:
> + compatible:
> + pattern: "^microchip,emc1814"
> + then:
> + patternProperties:
> + "^channel@[1-3]$":
> + properties:
> + reg:
> + items:
> + maximum: 3
> + properties:
> + channel@4: false
> +
> +additionalProperties: false
> +
> +examples:
> + - |
> + i2c {
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + temperature-sensor@4c {
> + compatible = "microchip,emc1813";
> + reg = <0x4c>;
> +
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + microchip,parasitic-res-on-channel1-2;
> +
> + vdd-supply = <&vdd>;
> +
> + channel@1 {
> + reg = <1>;
> + label = "External CH1 Temperature";
> + };
> +
> + channel@2 {
> + reg = <2>;
> + label = "External CH2 Temperature";
> + };
> + };
> + };
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 6d7b697bfdba16e4f0ee5f4f0195b9d7da06dae5..85c236df781e47c78deeb7ef4d80bc94bba604c4 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -16646,6 +16646,12 @@ S: Supported
> F: Documentation/devicetree/bindings/interrupt-controller/microchip,sama7g5-eic.yaml
> F: drivers/irqchip/irq-mchp-eic.c
>
> +MICROCHIP EMC1812 DRIVER
> +M: Marius Cristea <marius.cristea@...rochip.com>
> +L: linux-hwmon@...r.kernel.org
> +S: Supported
> +F: Documentation/devicetree/bindings/hwmon/microchip,emc1812.yaml
> +
> MICROCHIP I2C DRIVER
> M: Codrin Ciubotariu <codrin.ciubotariu@...rochip.com>
> L: linux-i2c@...r.kernel.org
>
> --
> 2.51.0
>
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