Re: [PATCH net-next 1/3] net: nixge: Add support for fixed-link subnodes

Andrew Lunn
2018-08-30T03:04:29Z

On Wed, Aug 29, 2018 at 05:40:44PM -0700, Moritz Fischer wrote:
> Add support for fixed-link cases where no MDIO is
> actually required to run the device.
> In that case no MDIO bus is instantiated since the
> actual registers are not available in hardware.

Hi Moritz

There are a few different use cases here:

The hardware is missing MDIO - You need fixed-link.

The hardware has MDIO, but you don't have a PHY connected on it, and
use fixed link.

The hardware has MDIO, and it is used e.g. for an Ethernet switch, or
a PHY for another Ethernet interface. Plus you need fixed link.

The binding typically looks like:

&fec1 {
phy-mode = "rmii";
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_fec1>;
status = "okay";

fixed-link {
speed = <100>;
full-duplex;
};

mdio1: mdio {
#address-cells = <1>;
#size-cells = <0>;
status = "okay";

switch0: switch0@0 {
compatible = "marvell,mv88e6085";
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_switch>;
reg = <0>;
eeprom-length = <512>;
interrupt-parent = <&gpio3>;

It is important you have the mdio subnode, with PHYs and switches as
children. The driver currently gets this wrong, it uses
pdev->dev.of_node.

So the first patch should be to extend this behaviour. Look for a
child node called mdio. If it exists, call nixge_mdio_setup() passing
that child. Otherwise continue using pdev->dev.of_node, so you don't
break backwards compatibility.

Then a patch adding support for fixed-link. If the mdio child node
exists, you still need to register the MDIO bus. If there is no child
node, but there is a fixed-link, skip registering the mdio bus with
pdev->dev.of_node.

Andrew