Re: [PATCH v5 1/2] dt-bindings: mux: gpio-mux: Add enable-gpios

[Alvin Šipraga]

On Thu, Nov 05, 2026 at 10:11:04AM +0000, Tapio Reijonen wrote:
> Analog multiplexers have an enable input besides the address inputs. On a
> 74HC4051 it is the E input: with E high, all eight switches are in the
> high-impedance off state, independent of S0 to S2. A 74HC4067 works the
> same way with four address inputs.
> 
> Two things need that input. The mux-controller binding describes an idle
> state of disconnect, which a gpio-mux cannot reach today because the
> address inputs always select a channel. And the address inputs are plain
> gpios that may live on different gpio controllers, so they are not
> updated in one go and the mux passes through the intermediate addresses
> on every channel change unless it is disabled meanwhile.
> 
> Add enable-gpios to describe the enable input, and require it for an idle
> state of disconnect.
> 
> Signed-off-by: Tapio Reijonen <tapio.reijonen@xxxxxxxxxxx>
> Acked-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>

Reviewed-by: Alvin Šipraga <alvin.sipraga@xxxxxxxxxx>

> ---
>  .../devicetree/bindings/mux/gpio-mux.yaml          | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/mux/gpio-mux.yaml b/Documentation/devicetree/bindings/mux/gpio-mux.yaml
> index ef7e33ec85d479ce57c5fe4a780f81a08a6ab6ba..2dd94704fd7bde238af4e84af87c2ad8e955eb14 100644
> --- a/Documentation/devicetree/bindings/mux/gpio-mux.yaml
> +++ b/Documentation/devicetree/bindings/mux/gpio-mux.yaml
> @@ -29,6 +29,14 @@ properties:
>      description:
>        Regulator to power on the multiplexer.
>  
> +  enable-gpios:
> +    maxItems: 1
> +    description:
> +      Enable input of the multiplexer, which disconnects all channels when
> +      deasserted, independent of mux-gpios. Deasserted while the mux-gpios
> +      are updated and for an idle state of disconnect, which cannot be
> +      reached with the mux-gpios alone and thus requires this gpio.
> +
>    '#mux-control-cells':
>      enum: [ 0, 1 ]
>  
> @@ -47,11 +55,23 @@ anyOf:
>    - required:
>        - "#mux-state-cells"
>  
> +allOf:
> +  - if:
> +      properties:
> +        idle-state:
> +          const: -2
> +      required:
> +        - idle-state
> +    then:
> +      required:
> +        - enable-gpios
> +
>  additionalProperties: false
>  
>  examples:
>    - |
>      #include <dt-bindings/gpio/gpio.h>
> +    #include <dt-bindings/mux/mux.h>
>  
>      mux: mux-controller {
>          compatible = "gpio-mux";
> @@ -59,6 +79,8 @@ examples:
>  
>          mux-gpios = <&pioA 0 GPIO_ACTIVE_HIGH>,
>                <&pioA 1 GPIO_ACTIVE_HIGH>;
> +        enable-gpios = <&pioA 2 GPIO_ACTIVE_LOW>;
> +        idle-state = <MUX_IDLE_DISCONNECT>;
>      };
>  
>      adc-mux {
> 
> -- 
> 2.47.3
>