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

[Tom Rini]

On Thu, Jun 19, 2025 at 04:04:00PM -0700, Tony Dinh wrote:
> Hi Tom,
> 
> On Thu, Jun 19, 2025 at 2:27 PM Tom Rini <trini at konsulko.com> wrote:
> >
> > 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.
> 
> I recalled we added support for Thumb-1 from way back and a few people
> have helped porting more changes from the Linux kernel.
> 
> U-boot has grown larger and larger over the years, especially with
> bootstd enabled (I know you have been watching closely for size
> growth). Built without CONFIG_SYS_THUMB_BUILD, the sheevaplug board is
> about 107K over the CONFIG_BOARD_SIZE_LIMIT of 512K. And it would be
> an unpleasant surprise to see size growth for other downstream
> projects still supporting Kirkwood SoCs.

Even with LTO enabled we would still be over limit? Oh no... That said,
I think we'll have something to try tomorrow to fix the regression.

-- 
Tom
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