[EXTERNAL] Re: Device Tree Overlays and FIT Images - Are they supported together fully?

[Westermann, Oliver]

Hey,

On Fri, 11 Feb 2022 at 08:54, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
> You can pass the name of a configuration and overlays to apply to the
> bootm command. See doc/uImage.FIT/overlay-fdt-boot.txt
> 
> Here are examples of usage:
> 
> * configs/am65x_hs_evm_a53_defconfig
> * include/configs/ti_armv7_common.h

It seems my first mail got lost, I'm not really used to mailinglists :(
My initial mail got send Tue Feb 1 10:50:48, not sure if you can still find it. It's in the archives at least.

I'm following the doc/uImage.FIT/overlay-fdt-boot.txt and it seems my FIT image (and dtbs contained) are okay, but I've issues with the bootm command:

> Which function?

My current setup uses bootm ${loadaddr}#${fit_config} which works fine, fit_config containing a configuration node name. When calling bootm ${loadaddr}#${fit_config}#bar to apply the bar overlay to ${fit_config}, I get the "Overlayed FDT requires relocation" error from boot/image-fit.c#L2341 out of function boot_get_fdt_fit().

I might be doing something wrong, but I did some classic printf debugging to understand the codepath leading up to this location. I could not find any code that would copy the dtb contained in my configuration out of the fit image, which means the check in L2339 should always trigger. I'm wondering if there is some "copy dtb out of FIT" step in overlay-fdt-boot.txt which I'm not seeing, but I feel like I triple checked that document by now ;-) So for me the base dtb sits in the FIT and u-boot declines to apply an overlay. The check itself makes sense to me as we can't check if there is sufficent padding beyond the base-dtb to prevent growing it into the next blob.

> U-Boot relocates itself to the top of memory. The available memory is
> shown by command bdinfo.
> 
> Run 'printenv' to see which other memory addresses are defined.

Thanks, I will check that for my testing, though I'm still wondering what I'm doing wrong.

Best regards, Olli