arm: mvebu: Kirkwood boards are broken by commit 6fe50e3

[Tom Rini]

On Thu, Jun 19, 2025 at 01:37:53PM -0700, Tony Dinh wrote:
> Hi Jerome,
> 
> While fixing some ext4 file system problems on 2025.07-rc4, I ran into
> a problem booting a few Kirkwood boards. kwboot loaded the u-boot
> image,
> and then u-boot execution was frozen without anything going to the
> serial console. I did a bisect and found the commit that caused it.
> 
> https://github.com/trini/u-boot/commit/6fe50e39508043f386fc1bd40bbc02b8a75c1940
> 
> When I tried to reverse this commit, I had a build error like this
> "{standard input}:24246: Error: selected processor does not support
> `mrc p15,1,r3,c15,c1,0' in Thumb mode"
> 
> Currently, the only way to boot Kirkwood boards is to disable either
> CONFIG_LTO or CONFIG_SYS_THUMB_BUILD or both.
> 
> I'm using the pogo_v4 and nsa325 boards as test beds. Please let me
> know if I can help with testing to troubleshoot this regression.

I wonder if the right answer is that CONFIG_SYS_THUMB_BUILD should be
off? A quick look around and this (and sheevaplug) are ARM926EJ-S which
is Thumb-1 not Thumb-2 and it looks like the kernel for example only
supports building itself with thumb2 on armv7/v7m. I know that this was
working, so we should dig more too, but I'm not sure what the best
answer here is.

-- 
Tom
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