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Device Tree Overlay
We can use DT overlays to enable/disable or change configuration for peripherals without recompiling the DT kernel source code.
DT collections
Device Reference Table
| Kernel Version | DT overlays folder | DT overlays list variable | DT overlays config file | |
|---|---|---|---|---|
| VIM1 | 4.9/mainline | /boot/dtb/overlays/kvim | overlays | /boot/env.txt |
| VIM2 | 4.9/mainline | /boot/dtb/overlays/kvim2 | ||
| VIM3 | 4.9/mainline | /boot/dtb/overlays/kvim3 | ||
| 5.15 | /boot/dtb/amlogic/kvim3.dtb.overlays | fdt_overlays | /boot/dtb/amlogic/kvim3l.dtb.overlay.env | |
| VIM3L | 4.9/mainline | /boot/dtb/overlays/kvim3l | overlays | /boot/env.txt |
| 5.15 | /boot/dtb/amlogic/kvim3l.dtb.overlays | fdt_overlays | /boot/dtb/amlogic/kvim3l.dtb.overlay.env | |
| VIM1S | 5.4/5.15 | /boot/dtb/amlogic/kvim1s.dtb.overlays | /boot/dtb/amlogic/kvim1s.dtb.overlay.env | |
| VIM4 | 5.4/5.15 | /boot/dtb/amlogic/kvim4.dtb.overlays | /boot/dtb/amlogic/kvim4.dtb.overlay.env | |
| Edge2 | 5.10 | /boot/dtb/rockchip/rk3588s-khadas-edge2.dtb.overlays | /boot/dtb/rockchip/rk3588s-khadas-edge2.dtb.overlay.env | |
| Edge1 | 4.4 | /boot/dtb/rockchip/overlays/captain | overlays | /boot/env.txt |
| /boot/dtb/rockchip/overlays/edgev |
Device Configurations
VIM1/2/3/3L/Edge1
DT-overlays dtbo directory: /boot/dtb/overlays/BOARD
BOARD should be kvim1, kvim2, kvim3, kvim3l or edgev.
Next example for VIM3 device, which can be different for other device, but the structure is the same.
khadas@Khadas:~$ ls -1 /boot/dtb/overlays/kvim3/
disable-ts050.dtbo
i2c3.dtbo
m2x-eth.dtbo
onewire.dtbo
os08a10.dtbo
pwm_f.dtbo
spi1.dtbo
uart3.dtbo
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
VIM3 with 5.15 kernel
DT-overlays dtbo directory: /boot/dtb/amlogic/kvim3.dtb.overlays.
khadas@Khadas:~$ ls -1 /boot/dtb/amlogic/kvim3.dtb.overlays/
uart3.dtbo
pwm_f.dtbo
i2c3.dtbo
spi1.dtbo
os08a10.dtbo
onewire.dtbo
disable-ts050.dtbo
m2x-eth.dtbo
otg-device.dtbo
DT-overlays configuration file: /boot/dtb/amlogic/kvim3.dtb.overlay.env.
VIM3L with 5.15 kernel
DT-overlays dtbo directory: /boot/dtb/amlogic/kvim3l.dtb.overlays.
khadas@Khadas:~$ ls -1 /boot/dtb/amlogic/kvim3.dtb.overlays/
uart3.dtbo
pwm_f.dtbo
i2c3.dtbo
spi1.dtbo
os08a10.dtbo
onewire.dtbo
disable-ts050.dtbo
m2x-eth.dtbo
otg-device.dtbo
DT-overlays configuration file: /boot/dtb/amlogic/kvim3l.dtb.overlay.env.
VIM4
DT-overlays dtbo directory: /boot/dtb/amlogic/kvim4.dtb.overlays.
khadas@Khadas:~$ ls -1 /boot/dtb/amlogic/kvim4.dtb.overlays/
ext_board.dtbo
i2cm_a.dtbo
i2cm_f.dtbo
pwm_f.dtbo
uart_e.dtbo
DT-overlays configuration file: /boot/dtb/amlogic/kvim4.dtb.overlay.env.
VIM1S
DT-overlays dtbo directory: /boot/dtb/amlogic/kvim1s.dtb.overlays
khadas@Khadas:~$ ls -1 /boot/dtb/amlogic/kvim1s.dtb.overlays/
i2cm_b.dtbo
i2cm_e.dtbo
pwm_f.dtbo
uart_c.dtbo
DT-overlays configuration file is /boot/dtb/amlogic/kvim1s.dtb.overlay.env.
Edge2
DT-overlays dtbo directory: /boot/dtb/rockchip/rk3588s-khadas-edge2.dtb.overlays
khadas@Khadas:~$ ls /boot/dtb/rockchip/rk3588s-khadas-edge2.dtb.overlays
mipi-panel.dtbo
DT-overlays configuration file: /boot/dtb/rockchip/rk3588s-khadas-edge2.dtb.overlay.env
Configuration DT Overlays
You need to edit the DT overlays configuration file and add custom DT overlays dtbo files to special folder.
Make custom DT Overlays
There are some preparations 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 = "okay"; }; }; };
Compile DT Overlay Source
dtc -I dts -O dtb -o example.dtbo example.dts
Copy DT Overlays to Special Folder
- VIM3 with 5.15 kernel is
/boot/dtb/amlogic/kvim3.dtb.overlays - VIM3L with 5.15 kernel is
/boot/dtb/amlogic/kvim3l.dtb.overlays - 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 kvim1, kvim2, kvim3, kvim3l or edgev.
Edit DT Overlays Configuration
Edit list variable value inside DT overlay configuration file:
- VIM1/2/3/3L/Edge1 is
/boot/env.txt - VIM3 with 5.15 kernel is
/boot/dtb/amlogic/kvim3.dtb.overlay.env - VIM3L with 5.15 kernel is
/boot/dtb/amlogic/kvim3l.dtb.overlay.env - 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 reboot board to take effect.