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Android Device Tree Overlay
We can use DT overlays to enable/disable or change the configuration of peripherals without recompiling the kernel source code.
Device Reference Table
| Android Version | DT overlays folder | DT overlays list variable | DT overlays config file | |
|---|---|---|---|---|
| Edge2 | 14 | /vendor/custom/boot/dtb/rockchip/rk3588s-khadas-edge2.dtb.overlays | fdt_overlays | /vendor/custom/boot/dtb/rockchip/rk3588s-khadas-edge2.dtb.overlay.env |
| VIM4 | 11,14 | /mnt/vendor/odm_ext/custom/overlays/kvim4.dtb.overlays | fdt_overlays | /mnt/vendor/odm_ext/custom/overlays/kvim4.dtb.overlays/kvim4.dtb.overlay.env |
Device Configurations
Edge2
DT-overlays dtbo directory: /vendor/custom/boot/dtb/rockchip/rk3588s-khadas-edge2.dtb.overlays
khadas@Khadas:~$ ls vendor/custom/boot/dtb/rockchip/rk3588s-khadas-edge2.dtb.overlays
edge2-io-spi.dtbo
DT-overlays configuration file: /mnt/vendor/odm_ext/custom/overlays/kvim4.dtb.overlays/kvim4.dtb.overlay.env
Enable：
$ echo fdt_overlays=edge2-io-spi > /vendor/custom/boot/dtb/rockchip/rk3588s-khadas-edge2.dtb.overlay.env
$ cat rk3588s-khadas-edge2.dtb.overlay.env
fdt_overlays=edge2-io-spi
Disable：
$ echo fdt_overlays= > /vendor/custom/boot/dtb/rockchip/rk3588s-khadas-edge2.dtb.overlay.env
$ cat rk3588s-khadas-edge2.dtb.overlay.env
fdt_overlays=
VIM4
DT-overlays dtbo directory: /mnt/vendor/odm_ext/custom/overlays/kvim4.dtb.overlays.
khadas@Khadas:~$ ls -1 /mnt/vendor/odm_ext/custom/overlays/kvim4.dtb.overlays
i2s.dtbo
pwm_f.dtbo
spdifout.dtbo
uart_e.dtbo
DT-overlays configuration file: /mnt/vendor/odm_ext/custom/overlays/kvim4.dtb.overlay.env
Enable：
$ echo fdt_overlays=i2s > /mnt/vendor/odm_ext/custom/overlays/kvim4.dtb.overlay.env
$ cat kvim4.dtb.overlay.env
fdt_overlays=i2s
Disable：
$ echo fdt_overlays= > /mnt/vendor/odm_ext/custom/overlays/kvim4.dtb.overlay.env
$ cat kvim4.dtb.overlay.env
fdt_overlays=
Configuration DT Overlays
You need to edit the DT overlays configuration file and add custom DT overlays dtbo files to a special folder.
Make custom DT Overlays
There are some preparation steps for DT overlays dtbo files, you can also add custom DT overlays.
Write DT Overlay Source
Basic DT overlay source example:
- example.dts
/dts-v1/; /plugin/; / { fragment@0 { target = <&i2c3>; __overlay__ { status = "disabled"; }; }; };
Compile DT Overlay Source
dtc -I dts -O dtb -o example.dtbo example.dts
Reboot
Need reboot board to take effect.