Kernel-4.18.0-80.el8_fixed-link

Fixed link Device Tree binding

Some Ethernet MACs have a “fixed link”, and are not connected to a
normal MDIO-managed PHY device. For those situations, a Device Tree
binding allows to describe a “fixed link”.

Such a fixed link situation is described by creating a ‘fixed-link’
sub-node of the Ethernet MAC device node, with the following
properties:

• ‘speed’ (integer, mandatory), to indicate the link speed. Accepted
  values are 10, 100 and 1000
• ‘full-duplex’ (boolean, optional), to indicate that full duplex is
  used. When absent, half duplex is assumed.
• ‘pause’ (boolean, optional), to indicate that pause should be
  enabled.
• ‘asym-pause’ (boolean, optional), to indicate that asym_pause should
  be enabled.
• ‘link-gpios’ (‘gpio-list’, optional), to indicate if a gpio can be read
  to determine if the link is up.

Old, deprecated ‘fixed-link’ binding:

• A ‘fixed-link’ property in the Ethernet MAC node, with 5 cells, of the
  form with the following accepted values:
  • a: emulated PHY ID, choose any but but unique to the all specified
    fixed-links, from 0 to 31
  • b: duplex configuration: 0 for half duplex, 1 for full duplex
  • c: link speed in Mbits/sec, accepted values are: 10, 100 and 1000
  • d: pause configuration: 0 for no pause, 1 for pause
  • e: asymmetric pause configuration: 0 for no asymmetric pause, 1 for
    asymmetric pause

Examples:

ethernet@0 {
…
fixed-link {
speed = <1000>;
full-duplex;
};
…
};

ethernet@1 {
…
fixed-link {
speed = <1000>;
pause;
link-gpios = <&gpio0 12 GPIO_ACTIVE_HIGH>;
};
…
};