[PATCH] ramips: fix Unifi 6 Lite boot failure with v5.15 kernels

[Jonas Gorski]

On Sun, 6 Nov 2022 at 12:50, Bjørn Mork <bjorn at mork.no> wrote:
>
> Jonas Gorski <jonas.gorski at gmail.com> writes:
>
> > An option is also to set a load address for the dtb in the FIT image,
> > then U-Boot will relocate it before passing it to the kernel.
>
> Yes, that is worth trying.  I thought this would be part of the fdt
> relocation step, but I see that the "load" property is used before the
> final relocation.
>
> I'll test this when I have console again.  Or earlier if someone can
> tell me how to calculate a semi-safe load address.  Will the kernel
> $loadaddr + aligned(8, 32, 512. 4096?) kernelsize be ok?

You'll probably then have the chance to land in the .bss section,
which gets zeroed on boot.

Safest might be a static address like RAMSTART + 16MiB. This is what
e.g. DentOS does.

Not sure if 16 MiB is enough for ramdisk kernels.

> And how do I figure out where in memory the fdt ended up, without seeing
> the console output from u-boot?  Can't see anything obvious in dmesg or
> in sysfs.  Do I need to enable a memory debug device, or is this address
> directly available somewhere?

I don't think so, at least I don't see anything obvious.

So I guess you'll need to sprinkle some debug printks there (e.g.
fw_arg0 or argument passed to __dt_setup_arch()).

Jonas