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Date:      Tue, 28 Nov 2023 12:35:34 -0800
From:      Mark Millard <marklmi@yahoo.com>
To:        Steve Rikli <sr@genyosha.net>, bob prohaska <fbsd@www.zefox.net>
Cc:        freebsd-arm <freebsd-arm@freebsd.org>
Subject:   Re: reboot hesitation on Pi3 running -current
Message-ID:  <301571AE-130B-4BF7-B703-9458CF524F46@yahoo.com>
In-Reply-To: <ZWZNKECfMEktSphI@dragon.home.genyosha.net>
References:  <ZWYCygMbVO9jFrWH@www.zefox.net> <4078F04C-B4AA-4029-B260-2A075A8832DA@yahoo.com> <ZWYSIlPorvAMVQQT@www.zefox.net> <ZWYd9zRl4F5OfyhC@dragon.home.genyosha.net> <ZWZGyB/yfNHNHhhv@www.zefox.net> <ZWZNKECfMEktSphI@dragon.home.genyosha.net>

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On Nov 28, 2023, at 12:27, Steve Rikli <sr@genyosha.net> wrote:

> On Tue, Nov 28, 2023 at 12:00:08PM -0800, bob prohaska wrote:
>> On Tue, Nov 28, 2023 at 09:05:59AM -0800, Steve Rikli wrote:
>>> On Tue, Nov 28, 2023 at 08:15:30AM -0800, bob prohaska wrote:
>>>> On Tue, Nov 28, 2023 at 07:20:03AM -0800, Mark Millard wrote:
>>>>> On Nov 28, 2023, at 07:10, bob prohaska <fbsd@www.zefox.net> =
wrote:
>>>>>=20
>>>>>> A Pi3 running -current has taken to pausing during a shutdown
>>>>>> -r in a strange way: It gets to:=20
>>>>>>=20
>>>>>> Hit [Enter] to boot immediately, or any other key for command
>>>>>> prompt.  Booting [/boot/kernel/kernel] in 5 second more
>>>>>> detailed help.
>>>>>>=20
>>>>>> It then stops at the OK prompt:
>>>>>>=20
>>>>>> OK boot <---typing boot fails:
>>>>>>=20
>>>>>> unknown command <---this looks strange, the kernel should
>>>>>> already be loaded
>>>>>=20
>>>>> A possibility here is garbage control characters, say before
>>>>> the "boot". YOu might want to type just <return> to the first OK
>>>>> prompt and see if you ever still get "unknown command" once you
>>>>> do type just "boot" (and <return>).
>>>>=20
>>>> IIRC I've done that in the past with the same result, but memory
>>>> is hazy and an attempt at a second shutdown -r came back up
>>>> without hesitation.
>>>>=20
>>>> Another build/install cycle is running now, I'll be more careful
>>>> next time.
>>>>=20
>>>>> The fact that the countdown stopped at 5 (or other early value)
>>>>> suggests such extra text at that point.
>>>>=20
>>>> Rubbish on the serial console is a common occurence, but it usually
>>>> shows up when the USB end is taken down and brought back up. In =
this
>>>> case the USB end remained up throughout the reboot cycle, no stray=20=

>>>> characters were visible.
>>>=20
>>> This topic has come up before here, I believe.
>>>=20
>>> I can confirm the same or very similar behavior on rpi4, and there's =
no
>>> USB-serial to disconnect on the remote end, rather an actual serial
>>> console server which is always-on.
>>=20
>> That's a significant (I think) observation. I couldn't tell where the
>> stray characters were originating and suspected the USB-serial
>> adapter. Your experience suggests very strongly the trouble is local
>> to the serial UART on the Pi or maybe wiring problems.=20
>=20
> I tend to agree. No USB-serial adapters involved in my setup. Wrt
> "wiring problem", fwiw I've tried multiple cables and db9 hoods, with
> both full-pins and 3-wire, no difference. All work as expected on =
other
> systems (NUC, various x86 PC, the occasional network gear etc.).
>=20
>> Is it possible that the serial port of the monitoring devices =
occasionally
>> echos output from the Pi's console back to the Pi? Seems to me it =
shouldn't,
>> but sometimes I see fragments of a login prompt among the rubbish.=20
>=20
> I imagine it's possible but I doubt it's happening. I've swapped ports =
on
> the serial console server as well JIC, again no change, and no other =
systems
> or devices exhibit behavior like this.
>=20
>>> Unfortunately it's not consistent behavior, i.e. sometimes the =
reboot
>>> proceeds uninterrupted. Sometimes typing 'boot' proceeds normally,
>>> sometimes typing 'boot' errors and then typing it again proceeds as
>>> normal.
>>=20
>> Does it sometimes reboot hands-off? Mine does, at least occasionally.
>=20
> Yes, sorry, that's what I meant by "sometimes reboot proceeds =
uninterrupted".
>=20
>>> I too have been thinking it's spurious chars on the serial console =
at
>>> various points, but I've yet to find a common behavior or consistent
>>> method to reproduce. This doesn't happen on my other serial =
consoles,
>>> FreeBSD or Linux. I also don't think it happened early on when this
>>> rpi4 was running raspbian for a brief time, but I didn't play with
>>> that setup very long.
>>>=20
>>> So far I believe it's avoidable by not watching the serial console
>>> during reboot, not necessary (I think) to disconnect the cable. But
>>> obviously that defeats the purpose of the serial console vs. a blind
>>> reboot.
>>=20
>> Hopefully "not watching" means disconnecting Rx and Tx from the GPIO
>> pins. If it means not looking at the display it's a whole 'nother =
story!
>>=20
>> 8-)
>=20
> Nothing is ever physically disconnected from the rpi4, if that's what =
you
> mean. Fyi my rpi4 serial console is via a "Serial Hat" which =
ultimately
> connects the appropriate GPIO pins to a db9 connector accessible =
outside
> the case, which is in-turn connected to my serial console server.
>=20
> "Not watching" in this context means I do not have an active =
connection
> to the serial console server port which communicates with the rpi4 db9
> serial port.
>=20
> Somewhat analagous to not running tip/cu/minicom from your laptop or
> whatever system you use to connect to the rpi4 GPIO pins.
>=20
> Another note JIC: there are no keyboard, mouse, HDMI, or USB devices
> connected to any of the rpi4 ports. Only power, the serial console and
> a network cable. In that regard it is a neat little headless server,
> but unfortunately I don't really want to use it in production due to
> this issue.

I'm going to remind of the known issue with U-Boot on the RPi*'s
sometimes leading to odd serial connection behavior for the
transition from U-Boot based UEFI handling the serial connection
to the FreeBSD UEFI loader handling it.

=3D=3D=3D
Mark Millard
marklmi at yahoo.com




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