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

From: Rob Herring
Date: Thu Mar 26 2020 - 15:41:10 EST


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@xxxxxxx>
> ---
> .../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@xxxxxxx>
> +
> +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
>