Re: [PATCH v3 1/7] dt-bindings: mfd: add NXP MC33978/MC34978 MSDI

[Krzysztof Kozlowski]

On Mon, Mar 09, 2026 at 02:49:12PM +0100, Oleksij Rempel wrote:
> Add device tree binding documentation for the NXP MC33978 and MC34978
> Multiple Switch Detection Interface (MSDI) devices.
> 
> These ICs monitor up to 22 mechanical switch contacts in automotive and
> industrial environments. They provide configurable wetting currents to
> break through contact oxidation and feature extensive hardware
> protection against thermal overload and voltage transients (load
> dumps/brown-outs).
> 
> The device interfaces via SPI and provides multiple functions. To
> accurately represent the hardware without unnecessary DT overhead, the
> binding is structured as follows:
> - pinctrl: A dedicated child node managing the 22 switch inputs (SG/SP
>   pins) and their GPIO configurations.
> - hwmon: Integrated into the parent node, exposing critical hardware
>   faults (OT, OV, UV) and static voltage/temperature thresholds.
> - mux: Integrated into the parent node, controlling the 24-to-1 analog
>   multiplexer to route pin voltages, internal temperature, or battery
>   voltage to an external SoC ADC.
> 
> Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
> ---
> changes v3:
> - Drop regular expression pattern from pinctrl child node and define
>   it as a standard property
> - Reorder required properties list in MFD binding
> - Remove stray blank line from the MFD binding devicetree example
> - Replace unevaluatedProperties with additionalProperties in the pinctrl
>   binding
> changes v2:
> - Squashed MFD, pinctrl, hwmon, and mux bindings into a single patch
> - Removed the empty hwmon child node
> - Folded the mux-controller node into the parent MFD node
> - Added vbatp-supply and vddq-supply to the required properties block
> - Changed the example node name from mc33978@0 to gpio@0
> - Removed unnecessary literal block scalars (|) from descriptions
> - Documented SG, SP, and SB pin acronyms in the pinctrl description
> - Added consumer polarity guidance (GPIO_ACTIVE_LOW/HIGH) for SG/SB
>   inputs, with a note on output circuit dependency
> - Updated commit message
> ---
>  .../devicetree/bindings/mfd/nxp,mc33978.yaml  | 112 ++++++++++++++++++
>  .../bindings/pinctrl/nxp,mc33978-pinctrl.yaml |  82 +++++++++++++
>  2 files changed, 194 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mfd/nxp,mc33978.yaml
>  create mode 100644 Documentation/devicetree/bindings/pinctrl/nxp,mc33978-pinctrl.yaml
> 
> diff --git a/Documentation/devicetree/bindings/mfd/nxp,mc33978.yaml b/Documentation/devicetree/bindings/mfd/nxp,mc33978.yaml
> new file mode 100644
> index 000000000000..23520315d484
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mfd/nxp,mc33978.yaml
> @@ -0,0 +1,112 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/mfd/nxp,mc33978.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: NXP MC33978/MC34978 Multiple Switch Detection Interface
> +
> +maintainers:
> +  - David Jander <david@xxxxxxxxxxx>
> +  - Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
> +
> +description:
> +  The MC33978 and MC34978 are Multiple Switch Detection Interface (MSDI)
> +  devices with 22 switch inputs, integrated fault detection, and analog
> +  multiplexer (AMUX) for voltage/temperature monitoring.
> +
> +allOf:
> +  - $ref: /schemas/spi/spi-peripheral-props.yaml#
> +
> +properties:
> +  $nodename:
> +    pattern: "^gpio(@.*)?$"

@.+, because it is not optional, or just drop the nodename completely.

> +
> +  compatible:
> +    enum:
> +      - nxp,mc33978
> +      - nxp,mc34978
> +
> +  reg:
> +    maxItems: 1
> +    description: SPI chip select number
> +
> +  spi-max-frequency:
> +    maximum: 8000000
> +    description: Maximum SPI clock frequency (up to 8 MHz)
> +
> +  interrupts:
> +    maxItems: 1
> +    description:
> +      INT_B pin interrupt. Active-low, indicates pin state changes or
> +      fault conditions.
> +
> +  interrupt-controller: true
> +
> +  '#interrupt-cells':
> +    const: 2
> +    description:
> +      First cell is the IRQ number (0-21 for pins, 22 for faults).
> +      Second cell is the trigger type (IRQ_TYPE_* from interrupt-controller.h).
> +
> +  '#mux-control-cells':
> +    const: 0
> +    description:
> +      Present if the device AMUX selector is used as a mux provider.
> +      Consumers (e.g. io-channel-mux) must provide settle-time-us for the
> +      external ADC sampling path.
> +
> +  vddq-supply:
> +    description: Digital supply voltage
> +
> +  vbatp-supply:
> +    description: Battery/power supply
> +
> +  pinctrl:
> +    type: object
> +    $ref: /schemas/pinctrl/nxp,mc33978-pinctrl.yaml#
> +    description:
> +      Pinctrl and GPIO controller child node for the 22 switch inputs.
> +
> +required:
> +  - compatible
> +  - reg
> +  - interrupts
> +  - interrupt-controller
> +  - '#interrupt-cells'
> +  - vddq-supply
> +  - vbatp-supply
> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/interrupt-controller/irq.h>
> +    #include <dt-bindings/gpio/gpio.h>
> +
> +    spi {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        msdi: gpio@0 {
> +            compatible = "nxp,mc33978";
> +            reg = <0>;
> +            spi-max-frequency = <4000000>;
> +
> +            interrupt-parent = <&gpiog>;
> +            interrupts = <9 IRQ_TYPE_LEVEL_LOW>;
> +            interrupt-controller;
> +            #interrupt-cells = <2>;
> +
> +            vddq-supply = <&reg_3v3>;
> +            vbatp-supply = <&reg_12v>;
> +
> +            #mux-control-cells = <0>;
> +
> +            pinctrl {
> +                compatible = "nxp,mc33978-pinctrl";
> +                gpio-controller;
> +                #gpio-cells = <2>;

pin grp nodes should be here


> +            };
> +        };
> +    };
> diff --git a/Documentation/devicetree/bindings/pinctrl/nxp,mc33978-pinctrl.yaml b/Documentation/devicetree/bindings/pinctrl/nxp,mc33978-pinctrl.yaml
> new file mode 100644
> index 000000000000..ba946906557c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pinctrl/nxp,mc33978-pinctrl.yaml
> @@ -0,0 +1,82 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/pinctrl/nxp,mc33978-pinctrl.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: NXP MC33978/MC34978 Pinctrl/GPIO Driver

s/Driver// because otherwise it sounds like "pinctrl driver" and you
cannot drive pin controls.

> +
> +maintainers:
> +  - David Jander <david@xxxxxxxxxxx>
> +  - Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
> +
> +description: |
> +  Pin control and GPIO driver for the MC33978/MC34978 MSDI device.
> +
> +  Pin numbering:
> +  - Pins 0-13: SG0-SG13 (Switch-to-Ground inputs). These pins monitor
> +    contacts closed to ground and typically require GPIO_ACTIVE_LOW
> +    flags when used as digital inputs.
> +  - Pins 14-21: SP0-SP7 (Programmable inputs). These can be configured
> +    as SG (Switch-to-Ground) or SB (Switch-to-Battery) inputs. SB
> +    inputs monitor contacts closed to the battery voltage and typically
> +    require GPIO_ACTIVE_HIGH flags when used as digital inputs.
> +
> +  Output Emulation:
> +  The hardware lacks standard push-pull output drivers. Outputs are emulated
> +  by toggling the programmable wetting current sources (acting as pull-ups or
> +  pull-downs) and the hardware tri-state registers. Because of this physical
> +  constraint:
> +  - Consumers using pins as outputs MUST flag them with GPIO_OPEN_DRAIN or
> +    GPIO_OPEN_SOURCE in the device tree.
> +  - Push-pull configurations are physically unsupported.
> +  - The active polarity depends entirely on the external circuit (e.g., how an
> +    LED is wired) and must be flagged accordingly by the consumer.
> +
> +properties:
> +  compatible:
> +    enum:
> +      - nxp,mc33978-pinctrl
> +      - nxp,mc34978-pinctrl

I did not raise it before, but now I think these compatibles are
pointless. MC33978 is a one, specific (as in fixed) device, so its
pinctrl/gpio part won't be taken and used in some other device. They
should be dropped. That way entire schema would fit parent one, although
its placement is odd - it's not really MFD device.


> +
> +  gpio-controller: true
> +
> +  '#gpio-cells':
> +    const: 2
> +
> +  ngpios:
> +    const: 22
> +
> +patternProperties:
> +  "^.*-grp$":

Keep consistent quotes, either ' or "

Best regards,
Krzysztof