Rockpi4/hardware/devtree overlays
ROCK Pi 4 > Hardware > Device Tree Overlays
Contents
Device Tree Overlays
Introduction
This directory contains Device Tree overlays. Device Tree makes it possible to support many hardware configurations with a single kernel and without the need to explicitly load or blacklisr kernel modules.
On Rock Pi, you will find a rockpi-4b-linux.dtb in /boot. This describes the hardware that is part of the Rock Pi board. The loader selects the .dtb file appropriate for the platform by name and pass it to the kernel.
Device Tree Overlays usage is controlled from /boot/hw_intfc.conf. You can do the settings for Rock Pi in your hw_intfc.conf, which should cause your Rock Pi to do your wanted things after a reboot.
In /boot/overlays you will find many .dtbo files. The loader will merge the selected .dtbo files by reading file /boot/hw_intfc.conf.
File Structure
/boot
|--rockpi-4b-linux.dtb
|--hw_intfc.conf
|--overlays
|--at24c02.dtbo
|--console-on-ttyS2.dtbo
|--console-on-ttyS4.dtbo
|--devspi1.dtbo
|--devspi2.dtbo
|--pcie-gen2.dtbo
|--two-color-led.dtbo
Using Overlays
Overlays are loaded using "intfc:" directive. As an example, consider the at24c02 module. Add one line in hw_intfc.conf:
intfc:dtoverlay=at24c02
This causes the file /boot/overlays/at24c02.dtbo to be loaded.
The Overlay and Parameter Reference
N.B. It is recommended to only ebable those bus interfaces that are needed. Leaving all interfaces enabled can lead to unwanted behaviour.
Seeing 40-pin GPIO connector , we find that UART4 and SPI1 share some pins, and I2C6 and SPI2 share some pins.
In order to solve the problem of pin conflicts, we make a convention.
When we set UART4 and SPI1 to "on" at the same, the system will forcibly set UART4 to "on" and SPI1 to "off" (Although you see SPI1 is “on” on file hw_intfc.conf,).
When we set I2C6 and SPI2 to "on" at the same time, the system will forcibly set I2C6 to "on" and SPI2 to "off".
Enabling and disabling BUS
Name: pwm0 Info: Overlay for BUS PWM0 Load: intfc:pwm0=<value> Value: on Set to "on" to enable the pwm0 interface (default "off") off Set to "off" to disable the pwm0 interface Name: pwm1 Info: Overlay for BUS PWM1 Load: intfc:pwm1=<value> Value: on Set to "on" to enable the pwm1 interface (default "off") off Set to "off" to disable the pwm2 interface Name: uart2 Info: Overlay for BUS UART2 Load: intfc:uart2=<value> Value: on Set to "on" to enable the uart2 interface (default "off") off Set to "off" to disable the uart2 interface Name: uart4 Info: Overlay for BUS UART4 Load: intfc:uart4=<value> Value: on Set to "on" to enable the uart4 interface (default "off") off Set to "off" to disable the uart4 interface Name: spi1 Info: Overlay for BUS SPI1 Load: intfc:spi1=<value> Value: on Set to "on" to enable the spi1 interface (default "off") off Set to "off" to disable the spi1 interface Name: spi2 Info: Overlay for BUS SPI2 Load: intfc:spi2=<value> Value: on Set to "on" to enable the spi2 interface (default "off") off Set to "off" to disable the spi2 interface Name: i2c2 Info: Overlay for BUS I2C2 Load: intfc:i2c2=<value> Value: on Set to "on" to enable the i2c2 interface (default "off") off Set to "off" to disable the i2c2 interface Name: i2c6 Info: Overlay for BUS I2C6 Load: intfc:i2c6=<value> Value: on Set to "on" to enable the i2c6 interface (default "off") off Set to "off" to disable the i2c6 interface Name: i2c7 Info: Overlay for BUS I2C7 Load: intfc:i2c7=<value> Value: on Set to "on" to enable the i2c7 interface (default "off") off Set to "off" to disable the i2c7 interface
Loading hardware module
Name: at24c02 Info: Overlay for activation of Atmel AT24C02 over I2C Load: intfc:dtoverlay=at24c02 Name: two-color-led Info: Overlay for activation of two color led module. Load: intfc:dtoverlay=two-color-led Name: console-on-ttyS2 Info: By default, fiq debugger console is disabled. When this dtbo file is loaded, Rock Pi enables fiq debugger console. ttyS2 Pins will output console information. At the same time, it is recommended that you set UART2 to off in file /boot/hw_intfc.conf and do not load console-on-ttyS4.dtbo file. Load: intfc:dtoverlay=console-on-ttyS2 Name: console-on-ttyS4 Info: By default, fiq debugger console is disabled. When this dtbo file is loaded, Rock Pi enables fiq debugger console. ttyS4 Pins will output console information. At the same time, it is recommended that you set UART4 to off in file /boot/hw_intfc.conf and do not load console-on-ttyS2.dtbo file. Load: intfc:dtoverlay=console-on-ttyS4 Name: devspi1 Info: By default, spi1 is disabled. when use spi1, uart4 must be disabled. Load: intfc:dtoverlay=devspi1 Name: devspi2 Info: By default, spi2 is disabled. When use spi2. i2c6 must be disabled. Load: intfc:dtoverlay=devspi2 Name: pcie-gen2 Info: Overlay for activation of pcie running on GEN2 mode. Load: intfc:dtoverlay=pcie-gen2
Installing ROCK Pi 4 dtbo package
Radxa APT provides rockpi4-dtbo package that includes hw_intfc.conf and .dtbo files. To use it, do:
$ sudo apt-get update $ sudo apt-get install rockchip-fstab $ sudo apt-get install rockpi4-dtbo