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From:   Rob Herring <robh+dt@kernel.org>
Date:   Wed, 13 Mar 2019 14:54:36 -0500
Message-ID: <CAL_JsqLRO8m+voL_6mSpcrGmAT-SPwXhXDSOMEgQW6wmmTxZfQ@mail.gmail.com>
Subject: Re: [PATCH v7 1/2] dt-bindings: misc: aspeed-p2a-ctrl: add support
To:     Patrick Venture <venture@google.com>
Cc:     Mark Rutland <mark.rutland@arm.com>, Joel Stanley <joel@jms.id.au>,
        Andrew Jeffery <andrew@aj.id.au>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        devicetree@vger.kernel.org,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@lists.infradead.org>,
        linux-aspeed@lists.ozlabs.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Tue, Mar 12, 2019 at 11:30 AM Patrick Venture <venture@google.com> wrote:
>
> Document the ast2400, ast2500 PCI-to-AHB bridge control driver bindings.
>
> Signed-off-by: Patrick Venture <venture@google.com>
> ---
> Changes for v7:
> - Moved node under the syscon node it requires
> Changes for v6:
> - None
> Changes for v5:
> - None
> Changes for v4:
> - None
> Changes for v3:
> - None
> Changes for v2:
> - Added comment about syscon required parameter.
> ---
>  .../bindings/misc/aspeed-p2a-ctrl.txt         | 48 +++++++++++++++++++
>  1 file changed, 48 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/misc/aspeed-p2a-ctrl.txt
>
> diff --git a/Documentation/devicetree/bindings/misc/aspeed-p2a-ctrl.txt b/Documentation/devicetree/bindings/misc/aspeed-p2a-ctrl.txt
> new file mode 100644
> index 000000000000..088cc4e3dc54
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/misc/aspeed-p2a-ctrl.txt
> @@ -0,0 +1,48 @@
> +======================================================================
> +Device tree bindings for Aspeed AST2400/AST2500 PCI-to-AHB Bridge Control Driver
> +======================================================================
> +
> +The bridge is available on platforms with the VGA enabled on the Aspeed device.
> +In this case, the host has access to a 64KiB window into all of the BMC's
> +memory.  The BMC can disable this bridge.  If the bridge is enabled, the host
> +has read access to all the regions of memory, however the host only has read
> +and write access depending on a register controlled by the BMC.
> +
> +Required properties:
> +===================
> +
> + - compatible: must be one of:
> +       - "aspeed,ast2400-p2a-ctrl"
> +       - "aspeed,ast2500-p2a-ctrl"
> +
> + - syscon: handle to syscon device node controlling PCI.
> +
> +Optional properties:
> +===================
> +
> +- memory-region: A phandle to a reserved_memory region to be used for the PCI
> +               to AHB mapping
> +
> +The p2a-control node should be the child of a syscon node with the required
> +property:
> +
> +- compatible : Should be one of the following:
> +               "aspeed,ast2400-scu", "syscon", "simple-mfd"
> +               "aspeed,g4-scu", "syscon", "simple-mfd"
> +               "aspeed,ast2500-scu", "syscon", "simple-mfd"
> +               "aspeed,g5-scu", "syscon", "simple-mfd"
> +
> +Example:
> +
> +g4 Example
> +----------
> +
> +syscon: scu@1e6e2000 {
> +       compatible = "aspeed,ast2400-scu", "syscon", "simple-mfd";
> +       reg = <0x1e6e2000 0x1a8>;
> +
> +       p2a: p2a-control {
> +               compatible = "aspeed,ast2400-p2a-ctrl";

If there's a defined register range, then you could add a reg property
(even though Linux doesn't use it).

Either way,

Reviewed-by: Rob Herring <robh@kernel.org>