Updating the TBC DTB File

[teebr]

I'm working with an Orin AGX on r35.3.1, and unfortunately I need to have a slightly different device tree for the bootloader versus the OS. With L4T I can do this by setting the TBCDTB_FILE variable. But from looking at flashvars and tegra234-flash-helper.sh it seems like it's hard-coded to use the Linux device tree. I can see this line in the flash helper: tbcdtbfilename="$dtb_file" but then tbcdtbfilename seems to not be used. So my questions are:

• could someone point me to exactly what would need to change in tegra234-flash-helper.sh in order to optionally have a different device tree for the bootloader? I'm a bit lost with exactly where uefi_jetson_with_dtb.bin gets generated. Should TBCDTB_FILE be added to flashvars and propagate it through that way, or just modify the flash helper?
• I presume a similar process for adding the device tree to the bootloader binary occurs for generating the BUP/ Capsule? I can't see if/ how the device tree for bootloader feeds into that stuff`

Thanks!

[madisongh]

I can see this line in the flash helper: tbcdtbfilename="$dtb_file" but then tbcdtbfilename seems to not be used.

It's used in the signing functions in odmsign.func.

I'm a bit lost with exactly where uefi_jetson_with_dtb.bin gets generated.

That concatenation happens in the python scripts - specifically, tegraflash_impl_t234.py, I think.

Should TBCDTB_FILE be added to flashvars and propagate it through that way, or just modify the flash helper?

Adding it as a flashvar and updating the helper to use it if it's present (and perhaps defaulting to using the kernel DTB if not) sounds like the right approach. I think that will cover both the flashing case and the BUP generation case.

[teebr]

Thanks Matt, I'll give that a go.