linux-kernel - Re: [PATCH] dt-bindings: dma: Convert mtk-uart-apdma to DT schema

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Message-ID: <79a47f67-bb66-bad4-b6bc-c6a8c0ef25dc@canonical.com>
Date:   Wed, 16 Feb 2022 14:26:14 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>, vkoul@...nel.org
Cc:     robh+dt@...nel.org, sean.wang@...iatek.com, matthias.bgg@...il.com,
        long.cheng@...iatek.com, dmaengine@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH] dt-bindings: dma: Convert mtk-uart-apdma to DT schema

On 16/02/2022 12:40, AngeloGioacchino Del Regno wrote:
> Convert the MediaTek UART APDMA Controller binding to DT schema.
> 
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> ---
>  .../bindings/dma/mediatek,uart-dma.yaml       | 112 ++++++++++++++++++
>  .../bindings/dma/mtk-uart-apdma.txt           |  56 ---------
>  2 files changed, 112 insertions(+), 56 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/dma/mediatek,uart-dma.yaml
>  delete mode 100644 Documentation/devicetree/bindings/dma/mtk-uart-apdma.txt
> 
> diff --git a/Documentation/devicetree/bindings/dma/mediatek,uart-dma.yaml b/Documentation/devicetree/bindings/dma/mediatek,uart-dma.yaml
> new file mode 100644
> index 000000000000..4583c8f535b2
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/dma/mediatek,uart-dma.yaml
> @@ -0,0 +1,112 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/dma/mediatek,uart-dma.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: MediaTek UART APDMA controller
> +
> +maintainers:
> +  - Long Cheng <long.cheng@...iatek.com>
> +
> +description: |
> +  The MediaTek UART APDMA controller provides DMA capabilities
> +  for the UART peripheral bus.
> +
> +allOf:
> +  - $ref: "dma-controller.yaml#"
> +
> +properties:
> +  compatible:
> +    oneOf:
> +      - items:
> +          - enum:
> +              - mediatek,mt2712-uart-dma
> +              - mediatek,mt8516-uart-dma
> +          - const: mediatek,mt6577-uart-dma
> +      - enum:
> +          - mediatek,mt6577-uart-dma
> +
> +  reg:
> +    minItems: 1
> +    maxItems: 16
> +
> +  interrupts:
> +    description: |
> +      TX, RX interrupt lines for each UART APDMA channel
> +    minItems: 1

It would be useful to have an "if:" block constraining the interrupts
(and reg array?), if the dma-requests is missing. If you need an
example, see length of "max8997,pmic-buck1-dvs-voltage" array in
relation to presence of max8997,pmic-buck1-uses-gpio-dvs.
https://elixir.bootlin.com/linux/v5.17-rc2/source/Documentation/devicetree/bindings/regulator/maxim,max8997.yaml#L259

The best would be to restrict number of interrupts to number of
requests, but I think dtschema cannot express this.

> +    maxItems: 32
> +
> +  clocks:
> +    description: Must contain one entry for the APDMA main clock
> +    maxItems: 1
> +
> +  clock-names:
> +    const: apdma
> +
> +  "#dma-cells":
> +    const: 1
> +    description: |
> +      The first cell specifies the UART APDMA channel number
> +
> +  dma-requests:
> +    description: |
> +      Number of virtual channels of the UART APDMA controller
> +    maximum: 16
> +
> +  mediatek,dma-33bits:
> +    type: boolean
> +    description: Enable 33-bits UART APDMA support
> +
> +required:
> +  - compatible
> +  - reg
> +  - interrupts
> +  - "#dma-cells"

No need for requiring dma-cells. It is coming from dma-common.yaml.

> +

Best regards,
Krzysztof