Boot does not work when changing default dts

[Mauro Salvini]

Hi,

I also wrote on RPI forums [1] to discuss about this problem.

I'm using a CM4 module on CMIO board, with an image built by Yocto 
(dunfell version) and containing u-boot version 2020.01.

When I add some overlays via config.txt file, or I change the original 
Linux dts and rebuild its dtb, often occours that the boot stops with 
this error message:

libfdt fdt_check_header(): FDT_ERR_BADMAGIC

generated by the "fdt addr" command in boot.scr script, executed by u-boot.

If I delete the env file (that boot.scr saves in FAT partition), boot 
restarts to work without errors. If I modify another time the devicetree 
(for example undoing the last modification), error happens again. Then, 
the problem is not related to dts errors.

This behavior seems to occour when a overlay (or a dts modification) 
adds or removes some pieces of dts: if overlay/modification overwrites 
existing properties values, error does not happen.

In fact, it seems that u-boot always uses fdt_addr saved in environment 
(when an env is saved), instead of the value passed by the RPI firmware, 
that changes if a modification (via dts rebuild or via overlay 
addition/remove) happens since the last loaded devicetree.

Is this the expected behavior (delete .env when there is a devicetree 
mdoification) or could be a bug?

Thanks in advance, regards

[1] https://www.raspberrypi.org/forums/viewtopic.php?f=107&t=307300
-- 
Mauro S. | KOAN sas | Bergamo - Italia
embedded software engineering
http://KoanSoftware.com