VIM2 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

https://github.com/khadas/khadas-linux-kernel-dt-overlays

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
VIM3	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
VIM3L	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
Edge1	4.4	/boot/dtb/rockchip/overlays/edgev	overlays	/boot/env.txt

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 overlays list variable value: uart3 pwm_f i2c3 os08a10
If you want to disable pwm_f you can remove pwm_f from overlays list variable
If you want to enable onewire, you can add onewire to overlays list 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**