linux-kernel - Re: [PATCH v2 1/2] dt-bindings: dmaengine: Add UniPhier external DMA controller bindings

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Message-ID: <20200206175458.GA12845@bogus>
Date:   Thu, 6 Feb 2020 17:54:58 +0000
From:   Rob Herring <robh@...nel.org>
To:     Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
Cc:     Vinod Koul <vkoul@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Mark Rutland <mark.rutland@....com>, dmaengine@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        Masami Hiramatsu <masami.hiramatsu@...aro.org>,
        Jassi Brar <jaswinder.singh@...aro.org>
Subject: Re: [PATCH v2 1/2] dt-bindings: dmaengine: Add UniPhier external DMA
 controller bindings

On Thu, Jan 30, 2020 at 02:27:27PM +0900, Kunihiko Hayashi wrote:
> Add devicetree binding documentation for external DMA controller
> implemented on Socionext UniPhier SoCs.
> 
> Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
> ---
>  .../bindings/dma/socionext,uniphier-xdmac.yaml     | 57 ++++++++++++++++++++++
>  1 file changed, 57 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/dma/socionext,uniphier-xdmac.yaml
> 
> diff --git a/Documentation/devicetree/bindings/dma/socionext,uniphier-xdmac.yaml b/Documentation/devicetree/bindings/dma/socionext,uniphier-xdmac.yaml
> new file mode 100644
> index 00000000..32abf18
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/dma/socionext,uniphier-xdmac.yaml
> @@ -0,0 +1,57 @@
> +# SPDX-License-Identifier: GPL-2.0

Dual license new bindings:

(GPL-2.0-only OR BSD-2-Clause)

> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/dma/socionext,uniphier-xdmac.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Socionext UniPhier external DMA controller
> +
> +description: |
> +  This describes the devicetree bindings for an external DMA engine to perform
> +  memory-to-memory or peripheral-to-memory data transfer capable of supporting
> +  16 channels, implemented in Socionext UniPhier SoCs.
> +
> +maintainers:
> +  - Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
> +
> +allOf:
> +  - $ref: "dma-controller.yaml#"
> +
> +properties:
> +  compatible:
> +    items:
> +      - const: socionext,uniphier-xdmac

You can drop 'items' for a single item.

> +
> +  reg:
> +    minItems: 1
> +    maxItems: 2

You need to say what each entry is:

items:
  - description: ...
  - description: ...

> +
> +  interrupts:
> +    maxItems: 1
> +
> +  "#dma-cells":
> +    const: 2
> +    description: |
> +      DMA request from clients consists of 2 cells:
> +        1. Channel index
> +        2. Transfer request factor number, If no transfer factor, use 0.
> +           The number is SoC-specific, and this should be specified with
> +           relation to the device to use the DMA controller.
> +
> +required:
> +  - compatible
> +  - reg
> +  - interrupts
> +  - "#dma-cells"

Add:

additionalProperties: false

> +
> +examples:
> +  - |
> +    xdmac: dma-controller@...10000 {
> +        compatible = "socionext,uniphier-xdmac";
> +        reg = <0x5fc10000 0x1000>, <0x5fc20000 0x800>;
> +        interrupts = <0 188 4>;
> +        #dma-cells = <2>;
> +        dma-channels = <16>;

Not documented. You need at least 'dma-channels: true' to indicate 
you're using this. But you should be able to have some constraints such 
as 'maximum: 16'.

Rob