linux-kernel - Re: [RFC 1/3] dt-binding: soc: qcom: Add binding for RFSA

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Date:   Fri, 28 Apr 2017 12:42:39 -0500
From:   Rob Herring <robh@...nel.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Frank Rowand <frowand.list@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC 1/3] dt-binding: soc: qcom: Add binding for RFSA

On Sat, Apr 22, 2017 at 10:35:17AM -0700, Bjorn Andersson wrote:
> This adds the binding for describing shared memory buffers for
> implementing the remote filesystem protocol.
> 
> Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> ---
> 
> My initial attempt was to mimic the ramoops of just adding the compatible to
> the reserved-memory node, but I have not been able to figure out a sane way of
> getting hold of the base address in the case that the memory region is
> described my a "size" only (done on some platforms).

I prefer the ramoops way.

> The problem is that we create the reserved_mem objects (and remove the
> memblocks) while we're still operating on the flattened representation, so
> without a phandle it doesn't seem like we have anything to perform the
> comparison with later on.

I'm not sure I follow.

> 
>  .../devicetree/bindings/soc/qcom/qcom,rfsa.txt     | 43 ++++++++++++++++++++++
>  1 file changed, 43 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/soc/qcom/qcom,rfsa.txt
> 
> diff --git a/Documentation/devicetree/bindings/soc/qcom/qcom,rfsa.txt b/Documentation/devicetree/bindings/soc/qcom/qcom,rfsa.txt
> new file mode 100644
> index 000000000000..b4de0de74e46
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/soc/qcom/qcom,rfsa.txt
> @@ -0,0 +1,43 @@
> +Qualcomm Remote File System Access binding
> +
> +This binding describes the Qualcomm RFSA, which serves the purpose of managing
> +the shared memory region used for remote processors to access block device data
> +using the Remote Filesystem protocol.
> +
> +- compatible:
> +	Usage: required
> +	Value type: <stringlist>
> +	Definition: must be:
> +		    "qcom,rfsa"

No versioning?

> +
> +- memory-region:
> +	Usage: required
> +	Value type: <prop-encoded-array>
> +	Definition: handle to memory reservation the associated rfsa region.
> +
> +- qcom,client-id:
> +	Usage: required
> +	Value type: <u32>
> +	Definition: identifier of the client to use this region for buffers.

What determines these numbers?

> +
> += EXAMPLE
> +The following example shows the RFSA setup for APQ8016, with the RFSA region
> +for the Hexagon DSP (id #1) located at 0x86700000.
> +
> +	reserved-memory {
> +		#address-cells = <2>;
> +		#size-cells = <2>;
> +		ranges;
> +
> +		rmtfs: rmtfs@...00000 {

I think you should have a compatible here even with the 2 node approach.

> +			reg = <0x0 0x86700000 0x0 0xe0000>;
> +			no-map;
> +		};
> +	};
> +
> +	hexagon-rfsa {
> +		compatible = "qcom,rfsa";
> +		memory-region = <&rmtfs>;
> +
> +		qcom,client-id = <1>;
> +	};
> -- 
> 2.12.0
>