Re: [PATCH 4/6] dt-bindings: clock: st,stm32-rcc: support spread spectrum clocking
From: Rob Herring
Date: Wed Jan 08 2025 - 18:48:18 EST
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@xxxxxxxxxxxxxxxxxxxx>
> ---
>
> .../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
>