linux-kernel - Re: [PATCH 2/2] dmaengine: msm_bam

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Date:	Mon, 28 Oct 2013 23:18:35 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Andy Gross <agross@...eaurora.org>
Cc:	Vinod Koul <vinod.koul@...el.com>, linux-arm-msm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	devicetree@...r.kernel.org,
	Dan Williams <dan.j.williams@...el.com>,
	David Brown <davidb@...eaurora.org>,
	Bryan Huntsman <bryanh@...eaurora.org>
Subject: Re: [PATCH 2/2] dmaengine: msm_bam_dma: Add device tree binding

On 10/25, Andy Gross wrote:
> diff --git a/Documentation/devicetree/bindings/dma/msm_bam_dma.txt b/Documentation/devicetree/bindings/dma/msm_bam_dma.txt
> new file mode 100644
> index 0000000..fe3ed8f
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/dma/msm_bam_dma.txt
> @@ -0,0 +1,49 @@
> +MSM BAM DMA controller
> +
> +Required properties:
> +- compatible: Should be "qcom,bam"
> +- reg: Address range for DMA registers
> +- interrupts: single interrupt for this controller
> +- #dma-cells: must be <3>
> +- clocks: required clock
> +- clock-names: name of clock
> +
> +Example:
> +
> +	dma0: dma@...84000 = {

I imagine it's fine to say 'bam0: dma@...84000' here. The node
name should stay dma though. This way we know that we're talking
about the first bam. Or if there is a more specific name for the
bam we could use that, like system-bam or sdhci-bam.

> +		compatible = "qcom,bam";
> +		reg = <0xf9984000 0x15000>;
> +		interrupts = <0 94 0>;
> +		clocks = <&bam_dma_ahb_cxc>;
> +		clock-names = "bam_clk";
> +		#dma-cells = <3>;
> +	};
> +
> +Client:
> +Required properties:
> +- dmas: List of dma channel requests
> +- dma-names: Names of aforementioned requested channels
> +
> +Clients must use the format described in the dma.txt file, using a four cell
> +specifier for each channel.
> +
> +The four cells in order are:
> +  1. A phandle pointing to the DMA controller
> +  2. The channel number
> +  3. The execution environment value for this channel.
> +  4. Direction of the fixed unidirectional channel
> +     0 - Memory to Device
> +     1 - Device to Memory

Should we add "2 - Device to Device" here? Is there anything more
that needs to be done in the binding for device to device
transfers.

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