LAN966x Overlays

1. Introduction

This document describes how to enable different overlays. The overlays are enabled when booting the fit image. And it is required for the u-boot to have support for this.

In u-boot it is required to enabled the config option:

OF_LIBFDT_OVERLAY=y

Then in the fit image that is booted, it is required to have each overlay like a configuration node, for example:

/dts-v1/;
/ {
    images {
           ...
           fdt_lan9668_ung8385_sb_lan8840_0_at_lan966x {
                  data = /incbin/("./lan966x_pcb8385_sb_lan8840.dtbo");
                  type = "flat_dt";
                  arch = "arm";
                  load = <0x67e80000>;
                  compression = "none";
           };
           ...
    };
    configurations {
           ...
           lan9668_ung8385_sa_lan8840_0_at_lan966x {
                  fdt = "fdt_lan9668_ung8385_sa_lan8840_0_at_lan966x";
           };
           ...
    };
};

And then in u-boot, the env variable pcb can be changed to contain all the overlays and the base configuration node. For example:

pcb=conf-1#lan9668_ung8385_sa_lan8840_0_at_lan966x#conf-2#conf-3

It is the user responsability to know which overlays need to apply.