Re: Serial terminal issues

On Jun 5, 2013, at 2:59, Jeremy Chadwick <jdc@koitsu.org> wrote:

> On Tue, Jun 04, 2013 at 11:32:48PM +0200, Alban Hertroys wrote:
>> I can't seem to get my serial terminal to work with my new system.
>> =

>> I had a serial terminal connected to my old system that worked great
>> and copied /boot.config, /boot/loader.conf and /etc/ttys settings over
>> from it.
>> =

>> The new system has a Gigabyte GA970A-UD3 board with just a serial
>> header on the board. I bought a serial connector backplate in an
>> electronics store and connected it to the board. Could the pinout be
>> different or something?
> =

> It is very possible.  You should have asked Gigabyte what exact product
> (specifically part number) to purchase that provided a
> header-to-backplane DB9 port, or if they could send you one (many will
> for free).  Always use what the mainboard vendor tells you.  Always.

I contacted Gigabyte, but haven't heard from them yet.

For the Dutch readers: their website is at gigabyte.co.nl. You absolutely d=
on't want to go to gigabyte.nl - not safe for work, not at all (guess where=
 I was=85).

> It's also very possible the cable you're using to connect from the
> Gigabyte board to something (you didn't disclose what) is wired wrong.

I doubt that. It has worked fine before in the same setup with the previous=
 PC and only stopped working once I connected it to the new PC. The new PC =
is the only variable, I expect that's where the problem is.

The other end of the serial cable is connected to a Bull serial terminal (T=
WSH004/A). The cable has been that same serial cable for the last 10 years =
or so.

>>> cat /boot.config =

>> -D -S19200
> =

> Please try using "-S19200 -Dh" (please read carefully).  The order of
> the arguments may matter as well (there has been some speculation on the
> lists about this, and I do not care to do the analysis; just passing
> information on blindly).

That's interesting, I didn't expect that. I'll test that when I get around =
to playing with the serial port again.
That said, these settings worked in the old PC. I copied boot.config straig=
ht over from my backups.

>>> cat /boot/loader.conf =

>> boot_multicons=3D"YES"
>> boot_serial=3D"YES"
>> comconsole_speed=3D"19200"
>> console=3D"comconsole,vidconsole"
> =

> You do not need any of this given what /boot.config contains.  Please
> remove it all.

Good to know, I never liked having this information in duplicate.

>>> From /var/log/messages:
>> Jun  4 21:28:50 solfertje kernel: uart0: <16550 or compatible> port 0x3f=
8-0x3ff irq =

>> 4 flags 0x10 on acpi0
>> Jun  4 21:28:50 solfertje kernel: uart0: console (19200,n,8,1)
>> Jun  4 21:28:50 solfertje kernel: orm0: <ISA Option ROMs> at iomem 0xd50=
00-0xd67ff,0xd7000-0xd7fff on isa0
>> Jun  4 21:28:50 solfertje kernel: sc0: <System console> at flags 0x100 o=
n isa0
>> Jun  4 21:28:50 solfertje kernel: sc0: VGA <16 virtual consoles, flags=
=3D0x300>
>> Jun  4 21:28:50 solfertje kernel: vga0: <Generic ISA VGA> at port 0x3c0-=
0x3df iomem 0xa0000-0xbffff on isa0
>> Jun  4 21:28:50 solfertje kernel: atkbdc0: <Keyboard controller (i8042)>=
 at port 0x60,0x64 on isa0
>> Jun  4 21:28:50 solfertje kernel: atkbd0: <AT Keyboard> irq 1 on atkbdc0
>> Jun  4 21:28:50 solfertje kernel: kbd0 at atkbd0
>> Jun  4 21:28:50 solfertje kernel: atkbd0: [GIANT-LOCKED]
> =

> Okay, so what's the problem?  You're not seeing any I/O on the serial
> port?

I get a blank screen with just a cursor. It's not blinking because blinking=
 cursors get on my nerves.

Whether that means no I/O at all or the wrong kind of I/O I can't tell. I h=
aven't set up a terminal like this in 10 years as the previous setup always=
 just worked once set up. It's quite possible that I forgot some important =
detail.

> How do you have your serial device connected to something on the
> other end?  Meaning: solfertje has a serial port, and it's connected to
> what exactly?

The Bull terminal mentioned above.

> Are you sure the device its connected to is working?

Well, it was still working great a few days ago before I replaced the PC it=
 was connected to, so I assume it still does.

(snipped useful information that doesn't apply to my case as my cable has p=
roven to be correct)

> =

>> I didn't see any options in the BIOS to set the console speed (just
>> address and IRQ, those are in the above). ISTR that my old mobo did
>> allow to set that information, but then again, that board (Tyan Tiger)
>> gave me access to the BIOS through the serial console.
> =

> This has absolutely no relevancy.

I thought as much, but it is one obvious difference between the old and new=
 situation...

> Serial port speed settings in a BIOS pertain to BIOS-level console
> redirection -- that redirection is lost the instant anything (boot
> loader, kernel, etc.) touches SMI and/or interrupts and starts
> "fiddling" with the serial port.

That's the bit I wasn't entirely certain of - that there is no possible int=
eraction from having a BIOS console to the point where the OS takes over. T=
hat's why I mentioned it.

I assumed that if the BIOS had set up the serial port to 19200 baud and the=
 OS didn't specify it, that it would be possible that the speed set up in t=
he BIOS would still be in effect and that the serial terminal just incident=
ally worked for the last 10 years because of that. Far-fetched, I know.

That's another theory shot down.

> What you're adjusting in FreeBSD is 1) the FreeBSD boot loader touching
> the serial port, and 2) the FreeBSD kernel outputting to a serial port
> (it also initialises/sets the serial port), and 3) getty et al spawning
> a login prompt on the serial port.

Regarding 2). I found some references on the internet pertaining settings i=
n the kernel config file to adjust serial console settings. Could that be w=
hat I'm missing?

I'm fairly certain the last kernel I used on the old PC was the GENERIC i38=
6 kernel. I don't think there are any significant differences regarding ser=
ial console between STABLE-i386 (of a few months ago) and STABLE-amd64?

> I would point you to my "FreeBSD via serial console and PXE" document,
> except there are one-offs specific to the PXE portions that are not
> relevant to your situation.  The important part is that I've used
> FreeBSD serial console for almost 16 years and have a very good
> understanding of what works (including vs. what some developers say
> "should" work; i.e. reality vs. pragmatism).

True, but there's relatively much interaction between the different parts t=
hat you need to get right before a serial console works at all. Such as hav=
ing everything on the same baud-rate, for an obvious example.

My guess is that the problem is indeed the connection from the motherboard =
header to the bracket on the case. I'll verify the cabling of that part som=
etime this weekend.

Thanks for the help so far.

Alban Hertroys
--
If you can't see the forest for the trees,
cut the trees and you'll find there is no forest.

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