Re: Reset on Beaglebone Black has become unreliable/broken

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hello Konstantin,

On 28.11.24 10:07, Konstantin Kletschke wrote:
> Dear barebox community and hackers,
> 
> we use barebox 022.04.0-dirty from 

I assume this should be v2022.04? -dirty means you have local patches
on top. Do any of them touch SoC-specific, board-specific parts
like clock or power?

> https://github.com/menschel-d/meta-barebox.git in our yocto kirkstone project.
> This worked for ages in up to hundreds of BBBs without any issue.
> 
> Since last week I have the problem, that the system is not able to
> reboot (linux userspace issuing reboot command) or reset (command reset
> at barebox prompt) anymore in _some_ of the BBBs we got delivered from
> SEEED (we get a couple of hundreds a couple of times per year). Speaking
> of some one digit percentage.

What changed over the last week on the software side? I understand barebox
stayed the same? Is the kernel still the same?

> Linux userspace running, issuing reboot command:
> 
> systemd-shutdown[1]: Rebooting.
> reboot: Restarting system
> -> Then gets stuck

On affected hardware: Does this happen always or only some times?

> Barebox prompt, issuing reset command:
> 
> Hit m for menu or ctrl-c to stop autoboot:    3
> barebox@TI AM335x BeagleBone black:/ reset
> -> Then gets stuck
> 
> This also applies to triggering the barebox's watchdog to trigger reset
> and also the hardware line on the BBB S2 is not working on those BBBs
> too! The S2 button is connected to CPU's NRESET_INOUT ball A10.

This sounds very similar to the issue fixed in commit 9c1a78f959dd
("Revert "ARM: beaglebone: init MPU speed to 800Mhz""), but that's already
included in v2022.04.0, hence the question if you have patches that
do anything similar.

> If I test those use cases with stock u-boot delivered with the BBB the
> reset/reboot works each time.
> 
> From the symptoms I guess the barebox is not able to start in each case
> when it should.

Yes, but it sounds strange that only now these problems pop up?

> Where can I start to investigate such an error, what could cause the
> hardware glitching away that something is on the edge which does not
> work anymore?

Besides checking what changed, you should check if Linux is playing
around with the voltages powering the SoC and if it does, disable that
to see if it improves the situation.

Afterwards, we can look into how you can make barebox resilient against
this.

> I learned it is something like a soft reset which is done in software,
> where can I look in the sourcetree for this special part?

Your barebox restart handler is probably am33xx_restart_soc (named
"soc" in reset -l output).

Cheers,
Ahmad

> 
> Kind Regards
> Konstantin 
> Kletschke


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