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Device Tree Overlay
We can use DT overlays to enable or disable the peripherals without recompiling the kernel source code.
| DT Overlays Directory | DT Overlays Node | DT Overlays Configuration File | |
|---|---|---|---|
| VIM1 | /boot/dtb/overlays/kvim | overlays | /boot/env.txt |
| VIM2 | /boot/dtb/overlays/kvim2 | ||
| VIM3 | /boot/dtb/overlays/kvim3 | ||
| VIM3L | /boot/dtb/overlays/kvim3l | ||
| VIM1S | /boot/dtb/amlogic/kvim1s.dtb.overlays | fdt_overlays | /boot/dtb/amlogic/kvim1s.dtb.overlay.env |
| VIM4 | /boot/dtb/amlogic/kvim4.dtb.overlays | /boot/dtb/amlogic/kvim4.dtb.overlay.env | |
| Edge2 | /boot/dtb/rockchip/rk3588s-khadas-edge2.dtb.overlays | /boot/dtb/rockchip/rk3588s-khadas-edge2.dtb.overlay.env | |
| Edge1 | /boot/dtb/rockchip/overlays/caption | overlays | /boot/env.txt |
| /boot/dtb/rockchip/overlays/edgev |
VIM1/2/3/3L/Edge1
This page takes VIM3 as an example, which can be different from yours but the structure is the same.
DT-overlays dtbo directory: /boot/dtb/overlays/BOARD
khadas@Khadas:~$ ls -l1 /boot/dtb/overlays/kvim3
total 40
-rw-r--r-- 1 root root 352 Jan 29 09:35 disable-ts050.dtbo
-rw-r--r-- 1 root root 223 Jan 29 09:35 i2c3.dtbo
-rw-r--r-- 1 root root 277 Jan 29 09:35 m2x-eth.dtbo
-rw-r--r-- 1 root root 472 Jan 29 09:35 onewire.dtbo
-rw-r--r-- 1 root root 1072 Jan 29 09:35 os08a10.dtbo
-rw-r--r-- 1 root root 345 Jan 29 09:35 pwm_f.dtbo
-rw-r--r-- 1 root root 447 Jan 29 09:35 spi1.dtbo
-rw-r--r-- 1 root root 225 Jan 29 09:35 uart3.dtbo
BOARD should be vim1, vim2, vim3, vim3l or edge.
DT-overlays configuration file: /boot/env.txt.
# Device Tree Overlays # uart3 -- Enable UART3 (uart_C, GPIO Header PIN15 & PIN16) # pwm_f -- Enable PWM_F (GPIO Header PIN35) # i2c3 -- Enable i2c3 (GPIO Header PIN22 & PIN23) # spi1 -- Enable SPI1 (GPIO Header PIN15 & PIN16 & PIN35 & PIN37), pwm_f need to be removed # os08a10 -- Enable OS08A10 Camera # onewire -- Enable onewire bus (PIO Header PIN15) # disable-ts050 -- Disable TS050 LCD # m2x-eth -- Enable M2X 100M ethernet. Note: 1G ethernet will be disabled. # otg-device -- Enable USB OTG Device overlays=uart3 pwm_f i2c3 os08a10
- default
overlayslist variable value:uart3 pwm_f i2c3 os08a10 - If you want to disable
pwm_fyou can removepwm_ffromoverlayslist variable - If you want to enable
onewire, you can addonewiretooverlayslist variable
VIM4
The dtbo files are stored in directory /boot/dtb/amlogic/kvim4.dtb.overlays:
khadas@Khadas:~$ ls -l1 /boot/dtb/amlogic/kvim4.dtb.overlays/
total 28
-rwxr-xr-x 1 root root 462 Jul 6 14:55 ext_board.dtbo
-rwxr-xr-x 1 root root 223 Jul 6 14:55 i2cm_a.dtbo
-rwxr-xr-x 1 root root 223 Jul 6 14:55 i2cm_f.dtbo
-rwxr-xr-x 1 root root 225 Jul 6 14:55 pwm_f.dtbo
-rwxr-xr-x 1 root root 225 Jul 6 14:55 uart_e.dtbo
DT-overlays configuration file is /boot/dtb/amlogic/kvim4.dtb.overlay.env.
VIM1S
The dtbo files are stored in directory /boot/dtb/amlogic/kvim1s.dtb.overlays:
khadas@Khadas:~$ ls -l1 /boot/dtb/amlogic/kvim1s.dtb.overlays/
total 28
-rw-rw-r-- 1 root root 223 Aug 12 10:59 i2cm_b.dtbo
-rw-rw-r-- 1 root root 223 Aug 12 10:59 i2cm_e.dtbo
-rw-rw-r-- 1 root root 345 Aug 12 10:59 pwm_f.dtbo
-rw-rw-r-- 1 root root 225 Aug 12 10:59 uart_c.dtbo
DT-overlays configuration file is /boot/dtb/amlogic/kvim1s.dtb.overlay.env.
Edge2
The dtbo files are stored in directory /boot/dtb/rockchip/rk3588s-khadas-edge2.dtb.overlays:
khadas@Khadas:~$ ls /boot/dtb/rockchip/rk3588s-khadas-edge2.dtb.overlays
mipi-panel.dtbo
The releated dtbo configuration file is /boot/dtb/rockchip/rk3588s-khadas-edge2.dtb.overlay.env.
Configuration
If you want to enable the peripherals, you can edit the DT-overlays configuration file and add the dtbo name to list.
Make custom DT overlays
There are some preparations steps DT overlays dtbo files, you can also add custom DT overlays to enable or disable the peripherals.
Write DT overlay source
Basic example:
- example.dts
/dts-v1/; /plugin/; / { fragment@0 { target = <&i2c3>; __overlay__ { status = "okay"; }; }; };
Compile DT overlay source
dtc -I dts -O dtb -o example.dtbo example.dts
Copy DT overlays to special folder
- VIM4 is
/boot/dtb/amlogic/kvim4.dtb.overlays - VIM1S is
/boot/dtb/amlogic/kvim1s.dtb.overlays - Edge2 is
/boot/dtb/rockchip/rk3588s-khadas-edge2.dtb.overlays - VIM1/2/3/3L/Edge1 is
/boot/dtb/overlays/BOARD
BOARD should be vim1, vim2, vim3, vim3l or edge
Edit DT overlays configuration
Add new custom overlay names to DT overlay configuration
- VIM1/2/3/3L/Edge1 is
/boot/env.txt - VIM4 is
/boot/dtb/amlogic/kvim4.dtb.overlay.env - VIM1S is
/boot/dtb/amlogic/kvim4.dtb.overlay.env - Edge2 is
/boot/dtb/rockchip/rk3588s-khadas-edge2.dtb.overlay.env
Reboot
Need to reboot the board to take effect.