[U-Boot] [PATCH 2/4 v3] doc: bindings: Add description for MDIO MUX dts nodes

[Bin Meng]

On Tue, Jun 18, 2019 at 10:58 PM Alexandru Marginean
<alexandru.marginean at nxp.com> wrote:
>
> Adds a short bindings document describing the expected structure of a MDIO
> MUX dts node.  This is based on Linux binding and the example is in fact
> copied from there.
>
> Signed-off-by: Alex Marginean <alexm.osslist at gmail.com>
> ---
>
> Changes in v2:
>         - no change
> Changes in v3:
>         - no change, just fighting with the email server
>
>  doc/device-tree-bindings/net/mdio-mux.txt | 61 +++++++++++++++++++++++
>  1 file changed, 61 insertions(+)
>  create mode 100644 doc/device-tree-bindings/net/mdio-mux.txt
>
> diff --git a/doc/device-tree-bindings/net/mdio-mux.txt b/doc/device-tree-bindings/net/mdio-mux.txt
> new file mode 100644
> index 0000000000..fdf817fd93
> --- /dev/null
> +++ b/doc/device-tree-bindings/net/mdio-mux.txt
> @@ -0,0 +1,61 @@
> +The expected structure of an MDIO MUX device tree node is described here.  This
> +is heavily based on current Linux specification.
> +The MDIO buses downstream of the MUX should be described in the device tree as
> +child nodes as indicated below.
> +
> +Required properties:
> +mdio-parent-bus = a phandle to the MDIO bus used to perform actual I/O.  This is
> +                  typically a real MDIO device, unless there are cascaded MUXes.

In Linux, "mdio-parent-bus" is optional, but in U-Boot this is required?

> +#address-cells = <1>, each MDIO group is identified by one 32b value.
> +#size-cells = <0>
> +
> +Other properties:
> +The properties described here are sufficient for MDIO MUX DM class code, but
> +MUX drivers may define additional properties, either required or optional.
> +
> +Required properties in child nodes:
> +reg = value to be configured on the MUX to select the respective downstream
> +      MDIO.
> +
> +Child nodes should normally contain PHY nodes, referenced by phandle from
> +ethernet nodes of the eth interfaces using these PHYs.
> +
> +Example structure, extracted from Linux bindings document:
> +
> +       /* The parent MDIO bus. */
> +       smi1: mdio at 1180000001900 {
> +               compatible = "cavium,octeon-3860-mdio";
> +               #address-cells = <1>;
> +               #size-cells = <0>;
> +               reg = <0x11800 0x00001900 0x0 0x40>;
> +       };
> +
> +       /*
> +          An NXP sn74cbtlv3253 dual 1-of-4 switch controlled by a
> +          pair of GPIO lines.  Child busses 2 and 3 populated with 4
> +          PHYs each.
> +        */

It looks the example is not complete, which makes it hard for people
to understand (ie: only bus 2 is listed below) without reading the
Linux bindings doc.

> +       mdio-mux {
> +               compatible = "mdio-mux-gpio";
> +               gpios = <&gpio1 3 0>, <&gpio1 4 0>;
> +               mdio-parent-bus = <&smi1>;
> +               #address-cells = <1>;
> +               #size-cells = <0>;
> +
> +               mdio at 2 {
> +                       reg = <2>;
> +                       #address-cells = <1>;
> +                       #size-cells = <0>;
> +
> +                       phy11: ethernet-phy at 1 {
> +                               reg = <1>;
> +                               marvell,reg-init = <3 0x10 0 0x5777>,
> +                                       <3 0x11 0 0x00aa>,
> +                                       <3 0x12 0 0x4105>,
> +                                       <3 0x13 0 0x0a60>;
> +                               interrupt-parent = <&gpio>;
> +                               interrupts = <10 8>; /* Pin 10, active low */
> +                       };
> +               };
> +       };
> +

Regards,
Bin