linux-kernel - Re: [PATCH 2/5] dt-bindings: dma: ingenic: Support #dma-cells = <3>

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Message-ID: <YW0UFWWNuYNEC8y+@matsya>
Date:   Mon, 18 Oct 2021 11:58:37 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     Rob Herring <robh+dt@...nel.org>, list@...ndingux.net,
        dmaengine@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mips@...r.kernel.org
Subject: Re: [PATCH 2/5] dt-bindings: dma: ingenic: Support #dma-cells = <3>

On 11-10-21, 16:36, Paul Cercueil wrote:
> Extend the binding to support specifying a different request type for
> each direction.
> 
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> ---
>  Documentation/devicetree/bindings/dma/ingenic,dma.yaml | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/dma/ingenic,dma.yaml b/Documentation/devicetree/bindings/dma/ingenic,dma.yaml
> index f45fd5235879..51b41e4795a2 100644
> --- a/Documentation/devicetree/bindings/dma/ingenic,dma.yaml
> +++ b/Documentation/devicetree/bindings/dma/ingenic,dma.yaml
> @@ -44,13 +44,17 @@ properties:
>      maxItems: 1
>  
>    "#dma-cells":
> -    const: 2
> +    enum: [2, 3]
>      description: >
>        DMA clients must use the format described in dma.txt, giving a phandle
> -      to the DMA controller plus the following 2 integer cells:
> +      to the DMA controller plus the following integer cells:
>  
>        - Request type: The DMA request type for transfers to/from the
>          device on the allocated channel, as defined in the SoC documentation.
> +        If "#dma-cells" is 2, the request type is a single cell. If
> +        "#dma-cells" is 3, the request type has two cells; the first one
> +        corresponds to the host to device direction, the second one corresponds
> +        to the device to host direction.

Why would you need the direction here, that should be a runtime
parameter and not a DT one?

>  
>        - Channel: If set to 0xffffffff, any available channel will be allocated
>          for the client. Otherwise, the exact channel specified will be used.
> -- 
> 2.33.0

-- 
~Vinod