Help getting started with modifying the Device Tree

[Daniel Block]

Can anyone give me some good web links and/or documents that would get me started working with and modifying the Device Tree for both the BeagleBone AI and BeagleBoard X15?  (Or probably for BeagleBone Black would also help a bunch)  I have been monitoring these Beagleboard Google groups for a while now and I believe I have some idea of what needs to be done but if there is a "how to" out there it would save me time.  From what I have gathered, it sounds like the modified device tree can be modified and recompiled on the BeagleBoard X15 (or AI) itself not requiring a separate cross compiling computer.  (If I need to, I can setup a cross compiling system).  I come at these TI processors looking at the DSP cores first when it comes to I/O and peripherals and then Linux comes second.  I am switching from the OMAPL138 processor to these AM5729 processors.  Because I come at these processors from the DSP end I find it much easier to perform I/O and peripheral setup from Linux using dev/mem like this discussion https://groups.google.com/forum/#!category-topic/beagleboard/beaglebone-ai/uKoSJUQaXH4  During this time of COVID-19 shutdown I thought I could figure out how to doing things the correct Linux way and device trees is the first step.    

[Robert Nelson]

On Mon, Apr 6, 2020 at 9:19 AM Daniel Block <dbloc...@gmail.com> wrote:
>
> Can anyone give me some good web links and/or documents that would get me started working with and modifying the Device Tree for both the BeagleBone AI and BeagleBoard X15? (Or probably for BeagleBone Black would also help a bunch) I have been monitoring these Beagleboard Google groups for a while now and I believe I have some idea of what needs to be done but if there is a "how to" out there it would save me time. From what I have gathered, it sounds like the modified device tree can be modified and recompiled on the BeagleBoard X15 (or AI) itself not requiring a separate cross compiling computer. (If I need to, I can setup a cross compiling system). I come at these TI processors looking at the DSP cores first when it comes to I/O and peripherals and then Linux comes second. I am switching from the OMAPL138 processor to these AM5729 processors. Because I come at these processors from the DSP end I find it much easier to perform I/O and peripheral setup from Linux using dev/mem like this discussion https://groups.google.com/forum/#!category-topic/beagleboard/beaglebone-ai/uKoSJUQaXH4 During this time of COVID-19 shutdown I thought I could figure out how to doing things the correct Linux way and device trees is the first step.

Hi Daniel,

So we've split all our Device Tree's into a separate repo, this allows
you to independently update and build the device tree's independent of
the kernel.

https://github.com/beagleboard/BeagleBoard-DeviceTrees

For the BBAI/BBX15 branches to look at are: v4.14.x-ti/v4.19.x-ti

https://github.com/beagleboard/BeagleBoard-DeviceTrees/tree/v4.14.x-ti

https://github.com/beagleboard/BeagleBoard-DeviceTrees/tree/v4.19.x-ti

To build and install the device tree's just run:

make
sudo make install


Specific branches of this repo is also shipped on your device under:

/opt/source/

but depends on the date of image creation..

Regards,

--
Robert Nelson
https://rcn-ee.com/

[Daniel Block]

Thanks Robert I will look at this repository.  

Dan

[Daniel Block]

Just want to confirm the correct way to proceed.  What I did was login to my BB-X15 in a terminal.  I changed directory to

/opt/source/dtb-4.14-ti/ and then I typed  

make

and it performed the build.

I did not do a, sudo make install, because I did not make any changes to the .dts files

So now that I know how to do that, what is my next step when I want to make changes?  Do I find the .dts file that has the I/O pins I need to change or add and then in a text editor make my changes and then build?  Or is it recommended that I clone the repository over top of the files in the /opt/source/dtb-4.14-ti/ folder and then make modifications to those files in a text editor and build, doing this all on the BB-X15?    

Also which dts files are used by the BB-X15 and BBAI?  The obvious ones are the AM57xx-bealge-x15- files but are any of the dra7 and OMAP5 files used for the BBX15?  Finally if I find an I/O pin that is not set in any of the .dts files how do I determine the best file to modify to add that pin?  

Thanks  

On Monday, April 6, 2020 at 9:19:06 AM UTC-5, Daniel Block wrote: