[PATCH 2/3] dt-bindings: arm: stm32: allow TAMP nvram child node for syscon

[Rob Herring]

On Thu, Sep 10, 2026 at 04:11:23PM +0200, Patrice Chotard wrote:
> The STM32 TAMP node (compatible "st,stm32-tamp", "syscon", "simple-mfd")
> exposes its backup registers through an nvram child node described by
> nvmem/st,stm32-tamp-nvram.yaml. That requires the TAMP node to carry
> "#address-cells", "#size-cells", "ranges" and an "nvram at ..." child.
> 
> st,stm32-syscon.yaml uses "additionalProperties: false" and only allowed
> reg/clocks/#clock-cells, so wiring the nvram provider into the DTSI made
> "make dtbs_check" fail on every STM32MP TAMP node:
> 
>   tamp at 5c00a000 (st,stm32-tamp): '#address-cells', '#size-cells',
>   'nvram at 5c00a100', 'ranges' do not match any of the regexes:
>   '^pinctrl-[0-9]+$'
> 
> Allow the addressing properties and the nvram child, gated on the
> st,stm32-tamp compatible so the other syscon variants stay strict.
> "#size-cells" may be 1 or 2: the STM32MP21 soc bus uses two size cells
> (an empty "ranges" requires the node to match its parent) while the
> other STM32MP SoCs use one.
> 
> Signed-off-by: Patrice Chotard <patrice.chotard at foss.st.com>
> ---
>  .../bindings/arm/stm32/st,stm32-syscon.yaml        | 28 ++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/arm/stm32/st,stm32-syscon.yaml b/Documentation/devicetree/bindings/arm/stm32/st,stm32-syscon.yaml
> index 95d2319afe23..8a0e751591f6 100644
> --- a/Documentation/devicetree/bindings/arm/stm32/st,stm32-syscon.yaml
> +++ b/Documentation/devicetree/bindings/arm/stm32/st,stm32-syscon.yaml
> @@ -39,6 +39,21 @@ properties:
>    "#clock-cells":
>      const: 0
>  
> +  "#address-cells":
> +    const: 1
> +
> +  "#size-cells":
> +    enum: [1, 2]
> +
> +  ranges: true
> +
> +patternProperties:
> +  "^nvram@[0-9a-f]+$":
> +    type: object
> +    description:
> +      TAMP backup registers exposed as an NVMEM provider. See
> +      nvmem/st,stm32-tamp-nvram.yaml.

To ensure the node matches a schema:

       required:
         - compatible

Rob