2001-11-06 21:54:05

by Patrick Allaire

[permalink] [raw]
Subject: Kernel booting on serial console ... crawling


I tried to boot my kernel using the serial console, using the
console=ttyS0,115200 (it does the same thing with 9600) ... it work great
until :

Freeing unused kernel memory: 36k freed
serial console detected. Disabling virtual terminals.
console=/dev/ttyS0

At this point the output of the serial line slow down dramaticly ... almost
to a halt ... I get 1 line every 30 seconds !!!

why is this slow down occuring ? the part which is 100% kernel is going fast
and ok, but when it become console related ... it slows down ?

thak you

Patrick Allaire
mailto:[email protected]
If you can see it, but it's not there, it's virtual.
If you can't see it, but it is there, it's hidden.
It you can't see it and it isn't there, it's gone.



2001-11-06 22:10:49

by Bradley D. LaRonde

[permalink] [raw]
Subject: Re: Kernel booting on serial console ... crawling

I've seen something like that when my serial driver wasn't getting
interrupts.

Regards,
Brad

"Patrick Allaire" <[email protected]> said:
> I tried to boot my kernel using the serial console, using the
> console=ttyS0,115200 (it does the same thing with 9600) ... it work great
> until :
>
> Freeing unused kernel memory: 36k freed
> serial console detected. Disabling virtual terminals.
> console=/dev/ttyS0
>
> At this point the output of the serial line slow down dramaticly ...
almost
> to a halt ... I get 1 line every 30 seconds !!!

2001-11-08 19:52:52

by Jose Luis Domingo Lopez

[permalink] [raw]
Subject: Re: Kernel booting on serial console ... crawling

On Tuesday, 06 November 2001, at 16:52:18 -0500,
Patrick Allaire wrote:

>
> I tried to boot my kernel using the serial console, using the
> console=ttyS0,115200 (it does the same thing with 9600) ... it work great
> until :
> [...]
> At this point the output of the serial line slow down dramaticly ... almost
> to a halt ... I get 1 line every 30 seconds !!!
>
Same problem seems to have happened here with 2.4.14 twice, but booting
as usual (no serial console, just keyboard + monitor).

First time I didn't care much because booted with "mem=8m" to test
system behaviour with little memory, and just when qmail was being
started from the init scripts, the system seemed to halt (not even
ALT-SysRq worked, just printed the action requested to the screen). But
I was no patient enough, and ended up rebooting the machine the hard way.

Today I booted my machine again, and this time during fsck the problem
appeared again: this time was a bit more patient and after several
seconds the boot process continued. ALT-SysRq didn't work until the
system "unfroze". This temporary "halt" happened several times during
the boot sequence, each time lasting a variable amount of seconds.

It's been 2 hours since that happened, and the machine is working
nicely so far.

Kernel configuration is the same as it was on, among others, 2.4.10,
2.4.12 and 2.4.13, but this problem only have showed with 2.4.14.

--
Jos? Luis Domingo L?pez
Linux Registered User #189436 Debian Linux Woody (P166 64 MB RAM)

jdomingo EN internautas PUNTO org => ? Spam ? Atente a las consecuencias
jdomingo AT internautas DOT org => Spam at your own risk

2001-11-09 09:19:55

by Robert Kaiser

[permalink] [raw]
Subject: Re: Kernel booting on serial console ... crawling

> I tried to boot my kernel using the serial console, using the
> console=ttyS0,115200 (it does the same thing with 9600) ... it work great
> until :
>
> Freeing unused kernel memory: 36k freed
> serial console detected. Disabling virtual terminals.
> console=/dev/ttyS0
>
> At this point the output of the serial line slow down dramaticly ... almost
> to a halt ... I get 1 line every 30 seconds !!!
>

Is this an AMD Elan's built-in serial port, perchance ?

Rob

----------------------------------------------------------------
Robert Kaiser email: [email protected]
SYSGO RTS GmbH
Am Pfaffenstein 14 phone: (49) 6136 9948-762
D-55270 Klein-Winternheim / Germany fax: (49) 6136 9948-10

2001-11-09 13:38:06

by Robert Schwebel

[permalink] [raw]
Subject: Re: Kernel booting on serial console ... crawling

Hi Rob,

On Fri, 9 Nov 2001, Robert Kaiser wrote:
> Is this an AMD Elan's built-in serial port, perchance ?

I got a patch for the Elan's serial port from Jason Sodergren some days
ago, but it's not clear to me what exactly the problem is with this port.
I'm using the serial console on a DIL/Net-PC without any problems so far.
Perhaps it might be a good idea to join forces and try to get a patch for
the Elan series into the main kernel?

However, my current affords can be found on

http://www.schwebel.de/software/dnp/index_en.html

This currently implements a new CPU configuration parameter and a fix for
the clock on the Elan CPUs.

Robert
--
+--------------------------------------------------------+
| Dipl.-Ing. Robert Schwebel |
| Pengutronix - Linux Solutions for Science and Industry |
| Braunschweiger Stra?e 79, 31134 Hildesheim, Germany |
| Phone: +49-5121-28619-0 Fax: +49-5121-28619-4 |
+--------------------------------------------------------+


2001-11-09 16:18:28

by Robert Kaiser

[permalink] [raw]
Subject: Re: Kernel booting on serial console ... crawling

Hi Robert,

Am Freitag, 9. November 2001 13:27 schrieben Sie:
> On Fri, 9 Nov 2001, Robert Kaiser wrote:
> > Is this an AMD Elan's built-in serial port, perchance ?
>
> I got a patch for the Elan's serial port from Jason Sodergren some days
> ago, but it's not clear to me what exactly the problem is with this port.
> I'm using the serial console on a DIL/Net-PC without any problems so far.
> Perhaps it might be a good idea to join forces and try to get a patch for
> the Elan series into the main kernel?
>
> However, my current affords can be found on
>
> http://www.schwebel.de/software/dnp/index_en.html
>
> This currently implements a new CPU configuration parameter and a fix for
> the clock on the Elan CPUs.

This is interesting, I was not aware of the different clock frequency issue.

Anyway, the patch I am using to fix the crawling console output symptom on
the Elan is entirely different (see attachment). It was originally posted by
Anders Larsen <[email protected]> and we have been using
it with good success in our embedded Linux product for quite a while now.
The comments in the source describe the problem. Interestingly, even the
latest AMD Elan product (SC520) seems to have this problem too.

Rob

----------------------------------------------------------------
Robert Kaiser email: [email protected]
SYSGO RTS GmbH
Am Pfaffenstein 14 phone: (49) 6136 9948-762
D-55270 Klein-Winternheim / Germany fax: (49) 6136 9948-10


Attachments:
patch-AMD-elan-serial (3.49 kB)
AMD Elan Workaround