Re: [PATCH v6 1/3] dt-bindings: add device tree binding for Arm CryptoCell trng engine

[Rob Herring <robh@kernel.org>]

On Wed, Mar 25, 2020 at 07:41:09AM +0200, Hadar Gat wrote:
> The Arm CryptoCell is a hardware security engine. This patch adds DT
> bindings for its TRNG (True Random Number Generator) engine.
> 
> Signed-off-by: Hadar Gat <hadar.gat@arm.com>
> ---
>  .../devicetree/bindings/rng/arm-cctrng.yaml        | 55 ++++++++++++++++++++++
>  1 file changed, 55 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/rng/arm-cctrng.yaml
> 
> diff --git a/Documentation/devicetree/bindings/rng/arm-cctrng.yaml b/Documentation/devicetree/bindings/rng/arm-cctrng.yaml
> new file mode 100644
> index 0000000..7f70e4b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/rng/arm-cctrng.yaml
> @@ -0,0 +1,55 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/rng/arm-cctrng.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Arm TrustZone CryptoCell TRNG engine
> +
> +maintainers:
> +  - Hadar Gat <hadar.gat@arm.com>
> +
> +description: |+
> +  Arm TrustZone CryptoCell TRNG (True Random Number Generator) engine.
> +
> +properties:
> +  compatible:
> +    enum:
> +      - arm,cryptocell-713-trng
> +      - arm,cryptocell-703-trng
> +
> +  interrupts:
> +    maxItems: 1
> +
> +  reg:
> +    maxItems: 1
> +
> +  arm,rosc-ratio:
> +    description:
> +      Arm TrustZone CryptoCell TRNG engine has 4 ring oscillators.
> +      Sampling ratio values for these 4 ring oscillators. (from calibration)
> +    allOf:
> +      - $ref: /schemas/types.yaml#/definitions/uint32-array
> +      - items:
> +          minItems: 4
> +          maxItems: 4

Aren't there some constraints on the values?

If not, then just this is enough:

- maxItems: 4

> +
> +  clocks:
> +    maxItems: 1
> +
> +required:
> +  - compatible
> +  - interrupts
> +  - reg
> +  - arm,rosc-ratio
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    arm_cctrng: rng@60000000 {
> +        compatible = "arm,cryptocell-713-trng";
> +        interrupts = <0 29 4>;
> +        reg = <0x60000000 0x10000>;
> +        arm,rosc-ratio = <5000 1000 500 0>;
> +    };
> -- 
> 2.7.4
>