linux-kernel - Re: [PATCH 06/10] arm64: allwinner: a64: Add devicetree binding for DMA controller

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Date:   Tue, 12 Sep 2017 11:52:20 -0500
From:   Rob Herring <robh@...nel.org>
To:     Stefan Brüns <stefan.bruens@...h-aachen.de>
Cc:     linux-sunxi@...glegroups.com, devicetree@...r.kernel.org,
        dmaengine@...r.kernel.org, Vinod Koul <vinod.koul@...el.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Code Kipper <codekipper@...il.com>,
        Andre Przywara <andre.przywara@....com>
Subject: Re: [PATCH 06/10] arm64: allwinner: a64: Add devicetree binding for
 DMA controller

On Mon, Sep 04, 2017 at 12:40:57AM +0200, Stefan Brüns wrote:
> The A64 is register compatible with the H3, but has a different number
> of dma channels and request ports.
> 
> Attach additional properties to the node to allow future reuse of the
> compatible for controllers with different number of channels/requests.
> 
> If dma-requests is not specified, the register layout defined maximum
> of 32 is used.

This belongs in the binding.

> 
> Signed-off-by: Stefan Brüns <stefan.bruens@...h-aachen.de>
> ---
>  .../devicetree/bindings/dma/sun6i-dma.txt          | 26 ++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/dma/sun6i-dma.txt b/Documentation/devicetree/bindings/dma/sun6i-dma.txt
> index 6b267045f522..66195fb31296 100644
> --- a/Documentation/devicetree/bindings/dma/sun6i-dma.txt
> +++ b/Documentation/devicetree/bindings/dma/sun6i-dma.txt
> @@ -26,6 +26,32 @@ Example:
>  		#dma-cells = <1>;
>  	};
>  
> +------------------------------------------------------------------------------
> +For A64 DMA controller:
> +
> +Required properties:
> +- compatible:	"allwinner,sun50i-a64-dma"
> +- dma-channels: Number of DMA channels supported by the controller.
> +		Refer to Documentation/devicetree/bindings/dma/dma.txt

dma.txt already explains what these properties are. You just need to 
state what are valid values.

> +- all properties above, i.e. reg, interrupts, clocks, resets and #dma-cells
> +
> +Optional properties:
> +- dma-requests: Number of DMA request signals supported by the controller.
> +		Refer to Documentation/devicetree/bindings/dma/dma.txt
> +
> +Example:
> +	dma: dma-controller@...02000 {

Drop the leading 0. Building dtbs with W=2 will tell you this.

> +		compatible = "allwinner,sun50i-a64-dma";
> +		reg = <0x01c02000 0x1000>;
> +		interrupts = <GIC_SPI 50 IRQ_TYPE_LEVEL_HIGH>;
> +		clocks = <&ccu CLK_BUS_DMA>;
> +		dma-channels = <8>;
> +		dma-requests = <27>;
> +		resets = <&ccu RST_BUS_DMA>;
> +		#dma-cells = <1>;
> +	};
> +------------------------------------------------------------------------------
> +
>  Clients:
>  
>  DMA clients connected to the A31 DMA controller must use the format
> -- 
> 2.14.1
>