Edit device tree at run time
Introduction
Sometimes, when we are working on an embedded device adding a new module or debugging an existing one, we need to constantly modify the device tree. This wiki page explains an easy way of doing it from the same target board without the need of going to the source code. For this purpose we'll use a tool called devocet-tree-compitler
Using the tool
Install the tool
sudo apt-get install device-tree-compiler
After this should have these tools installed: fdtdump fdtget fdtput
Dumping the dtb
To dump the dtb you can use fdtdump as follows:
fdtdump [options] <file>
For instance:
fdtdump /boot/tegra186-quill-p3310-1000-c03-00-base.dtb
Getting a property
To get a property you can use fdtget as follows:
fdtget <options> <dt file> [<node> <property>]...
For instance, to get the clock frequency for i2c0:
fdtget /boot/tegra186-quill-p3310-1000-c03-00-base.dtb i2c0 clock-frequency
Setting a property
To set a property you can use fdtput as follows:
fdtput <options> <dt file> <node> <property> [<value>...]
So for example, to set the clock frequency for i2c0:
sudo fdtput -t i /boot/tegra186-quill-p3310-1000-c03-00-base.dtb i2c0 clock-frequency 100000
After this you should restart your board for the changes to take effect.
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