linux-kernel - Re: [PATCH 1/3] dt-bindings: bus: Add documentation for Tegra210 ACONNECT

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Message-ID: <20160503182215.GA4341@rob-hp-laptop>
Date:	Tue, 3 May 2016 13:22:15 -0500
From:	Rob Herring <robh@...nel.org>
To:	Jon Hunter <jonathanh@...dia.com>
Cc:	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Alexandre Courbot <gnurou@...il.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>, linux-tegra@...r.kernel.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 1/3] dt-bindings: bus: Add documentation for Tegra210
 ACONNECT

On Fri, Apr 29, 2016 at 02:53:45PM +0100, Jon Hunter wrote:
> Add binding documentation for the Tegra ACONNECT bus that is part of the
> Audio Processing Engine (APE) on Tegra210. The ACONNECT bus is used to
> access devices within the APE subsystem. The APE is located in a
> separate power domain and so accesses made to the ACONNECT require the
> power domain to be enabled as well as some platform specific clocks.
> 
> Signed-off-by: Jon Hunter <jonathanh@...dia.com>
> ---
>  .../bindings/bus/nvidia,tegra210-aconnect.txt      | 45 ++++++++++++++++++++++
>  1 file changed, 45 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/bus/nvidia,tegra210-aconnect.txt
> 
> diff --git a/Documentation/devicetree/bindings/bus/nvidia,tegra210-aconnect.txt b/Documentation/devicetree/bindings/bus/nvidia,tegra210-aconnect.txt
> new file mode 100644
> index 000000000000..e5e915f8fca7
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/bus/nvidia,tegra210-aconnect.txt
> @@ -0,0 +1,45 @@
> +NVIDIA Tegra ACONNECT Bus
> +
> +The Tegra ACONNECT bus is an AXI switch which is used to connnect various
> +components inside the Audio Processing Engine (APE). All CPU accesses to
> +the APE subsystem go through the ACONNECT via an APB to AXI wrapper.
> +
> +Required properties:
> +- compatible: Must be "nvidia,tegra210-aconnect".
> +- clocks: Must contain the entries for the APE clock (TEGRA210_CLK_APE),
> +  and APE interface clock (TEGRA210_CLK_APB2APE).
> +- clock-names: Must contain the names "ape" and "apb2ape" for the corresponding
> +  'clocks' entries.
> +- power-domains: Must contain a phandle that points to the audio powergate
> +  (namely 'aud') for Tegra210.
> +- #address-cells: The number of cells used to represent physical base addresses
> +  in the host1x address space. Should be 2.
> +- #size-cells: The number of cells used to represent the size of an address
> +  range in the host1x address space. Should be 2.

Do you really need >4GB of child addresses?

> +- ranges: 1:1 mapping of the aconnect address space to the CPU address space.

Why 1:1 for 256KB of address space?

> +
> +All devices accessed via the ACONNNECT are described by child-nodes.
> +
> +Example:
> +
> +	aconnect@...c0000 {
> +		compatible = "nvidia,tegra210-aconnect";
> +		clocks = <&tegra_car TEGRA210_CLK_APE>,
> +			 <&tegra_car TEGRA210_CLK_APB2APE>;
> +		clock-names = "ape", "apb2ape";
> +		power-domains = <&pd_audio>;
> +
> +		#address-cells = <2>;
> +		#size-cells = <2>;
> +		ranges = <0x0 0x702c0000 0x0 0x702c0000 0x0 0x00040000>;
> +
> +		status = "disabled";
> +
> +		child1 {
> +			...
> +		};
> +
> +		child2 {
> +			...
> +		};
> +	};
> -- 
> 2.1.4
>