Re: [PATCH 4/6] dt-bindings: clock: st,stm32-rcc: support spread spectrum clocking

[Rob Herring <robh@kernel.org>]

On Sun, Jan 05, 2025 at 07:14:16PM +0100, Dario Binacchi wrote:
> The addition of DT bindings for enabling and tuning spread spectrum
> clocking generation is available only for the main PLL.
> 
> Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
> ---
> 
>  .../bindings/clock/st,stm32-rcc.yaml          | 27 +++++++++++++++++++
>  1 file changed, 27 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/clock/st,stm32-rcc.yaml b/Documentation/devicetree/bindings/clock/st,stm32-rcc.yaml
> index ae9e5b26d876..c345d3ff3fc4 100644
> --- a/Documentation/devicetree/bindings/clock/st,stm32-rcc.yaml
> +++ b/Documentation/devicetree/bindings/clock/st,stm32-rcc.yaml
> @@ -77,6 +77,26 @@ properties:
>        Phandle to system configuration controller. It can be used to control the
>        power domain circuitry.
>  
> +  st,ssc-modfreq-hz:
> +    description:
> +      The modulation frequency for main PLL (in Hz)

No constraints?

> +
> +  st,ssc-moddepth-permyriad:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      The modulation rate for main PLL (in permyriad, i.e. 0.01%)
> +    minimum: 25
> +    maximum: 200
> +
> +  st,ssc-modmethod:
> +    $ref: /schemas/types.yaml#/definitions/non-unique-string-array
> +    description:
> +      The modulation techniques for main PLL.
> +    items:
> +      enum:
> +        - center-spread
> +        - down-spread

What's the default? If there's only 2 possibilities, then you can use a 
boolean instead. Though I assume you want to support spread-spectrum 
disabled.

Are there dependencies between these properties? 

> +
>  required:
>    - compatible
>    - reg
> @@ -97,6 +117,10 @@ allOf:
>            const: 1
>            description: |
>              The clock index for the specified type.
> +        st,ssc-modfreq-hz: false
> +        st,ssc-moddepth-permyriad: false
> +        st,ssc-modmethod: false
> +
>      else:
>        properties:
>          '#clock-cells':
> @@ -118,6 +142,9 @@ examples:
>          reg = <0x40023800 0x400>;
>          clocks = <&clk_hse>, <&clk_i2s_ckin>;
>          st,syscfg = <&pwrcfg>;
> +        st,ssc-modfreq-hz = <10000>;
> +        st,ssc-moddepth-permyriad = <200>;
> +        st,ssc-modmethod = "center-spread";
>      };
>  
>    - |
> -- 
> 2.43.0
>