Device tree FAQ discussion

General Discussion
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#1

Continuing the discussion from Device tree FAQ:

I’m trying to improve the FAQ section of the forums. Any thoughts on resources to help people understand device tree usage on Beagle?

Also, we are starting a blog series on device tree usage. See Improving usage of device trees – BeagleBoard.org Blog.

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#2

Looking forward to learning about the improvements!

The above link results in the following for me:

image

#3

Grrr… I thought these were live. I thought the permission limitation was only regarding posting. Hey @fwbarber, can you help me fix?

#4

OK, check now. I think I fixed it.

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#5

Hello @cbrake ,

Seth here. I also found that the DT info. from beagleboard.org and their BeagleBoard-DeviceTrees link in the above link has tons of info.

I have learned how to associate many items w/in the am335x/am5729 to DT and actually see how things are done instead of just theory on DT.

Seth

P.S. For instance, https://github.com/beagleboard/BeagleBoard-DeviceTrees/blob/v4.19.x-ti-overlays/src/arm/bbai-bone-buses.dtsi#L8 , shows some include of another file. This file is the actual file one would work on, presumably. I will also list this file, https://github.com/beagleboard/BeagleBoard-DeviceTrees/blob/v4.19.x-ti-overlays/src/arm/am572x-bone-common-univ.dtsi#L6 , which has this elusive file that I have not found yet. Anyway, for am5729 on the BBAI, these are good resources to review and learn from my perspective.

#6

I’m currently working on using the BBB in a project, and it would be convenient to use a newer u-boot/kernel for various reasons. Is the overlay mechanism usable in recent u-boot/kernels?

Will the overlay mechanism stay in u-boot, or will it be moving to the kernel? I see a kernel link referenced in the blog post, but if I understand correctly, the BBB overlay mechanism has historically been entirely in u-boot.

#7

So mainline u-boot has overlay support and ‘expansion’ support now.

Someday, the kernel land might support something like overlays, but someday is not useful for us, thus u-boot is the best way today.

Edit, bootlin’s post is now public: Using Device Tree Overlays, example on BeagleBone boards

Regards,

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#8

Hello @RobertCNelson ,

Thank you for bringing this up. I cannot wait to sink my teeth into this article. I saw the Cape…

Seth

P.S. Seriously, thank you for posting the link.

#9

It is also posted on the BeagleBoard.org blog Using Device Tree Overlays, example on BeagleBone Cape add-on boards – BeagleBoard.org Blog

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