Garbage on serial console after serial driver loads

Garbage on serial console after serial driver loads

[Luca]

Hi,
I attached a null modem cable to my notebook and I'm seeing garbage as
soon as the serial driver is loaded. I tried booting with init=/bin/bash
to be sure that it's not some rc script doing strange things to the
serial port, but this didn't solve the problem.

This is the relevant part of .config:

#
# Serial drivers
#
CONFIG_SERIAL_8250=y
CONFIG_SERIAL_8250_CONSOLE=y
# CONFIG_SERIAL_8250_CS is not set
# CONFIG_SERIAL_8250_ACPI is not set
CONFIG_SERIAL_8250_NR_UARTS=4
# CONFIG_SERIAL_8250_EXTENDED is not set


I also tried with ACPI discovery (just in case) without success:

#
# Serial drivers
#
CONFIG_SERIAL_8250=y
CONFIG_SERIAL_8250_CONSOLE=y
# CONFIG_SERIAL_8250_CS is not set
CONFIG_SERIAL_8250_ACPI=y
CONFIG_SERIAL_8250_NR_UARTS=4
CONFIG_SERIAL_8250_EXTENDED=y
# CONFIG_SERIAL_8250_MANY_PORTS is not set
# CONFIG_SERIAL_8250_SHARE_IRQ is not set
CONFIG_SERIAL_8250_DETECT_IRQ=y
# CONFIG_SERIAL_8250_MULTIPORT is not set
# CONFIG_SERIAL_8250_RSA is not set

This is kernel command line:

Kernel command line: BOOT_IMAGE=linux-2.6.12rc1 ro root=305 video=sisfb:mode:1024x768x16 console=tty0 console=ttyS0,38400n8 init=/bin/bash

And this is where garbage appears:

PNP: PS/2 Controller [PNP0303:PS2K,PNP0f13:PS2M] at 0x60,0x64 irq 1,12
i8042.c: Detected active multiplexing controller, rev 1.1.
serio: i8042 AUX0 port at 0x60,0x64 irq 12
serio: i8042 AUX1 port at 0x60,0x64 irq 12
serio: i8042 AUX2 port at 0x60,0x64 irq 12
serio: i8042 AUX3 port at 0x60,0x64 irq 12
serio: i8042 KBD port at 0x60,0x64 irq 1
Serial: 8250/16550 driver $Revision: 1.90 $ 8 ports, IRQ sharing disabled
[garbage]

Once I get the shell using 'clear' cures the problem. The log (from
dmesg) should be:

Serial: 8250/16550 driver $Revision: 1.90 $ 8 ports, IRQ sharing disabled
ttyS0 at I/O 0x3f8 (irq = 4) is a NS16550A
ttyS1 at I/O 0x2f8 (irq = 3) is a NS16550A
ttyS0 at I/O 0x3f8 (irq = 4) is a NS16550A

This is the first time that I use serial console with the notebook, but
I've done this before with other machines and never saw this problem.

Googling aroung I found another user with the same problem:
http://www.ussg.iu.edu/hypermail/linux/kernel/0503.1/0442.html
but no answer :(

Any suggestion?

Luca
-- 
Home: http://kronoz.cjb.net
Un apostolo vedendo Gesu` camminare sulle acque:
- Cazzo se e` buono 'sto fumo!!!

Re: Garbage on serial console after serial driver loads

[Russell King]

On Fri, Mar 25, 2005 at 09:24:15PM +0100, Luca wrote:
> I attached a null modem cable to my notebook and I'm seeing garbage as
> soon as the serial driver is loaded. I tried booting with init=/bin/bash
> to be sure that it's not some rc script doing strange things to the
> serial port, but this didn't solve the problem.

I'm uncertain how this problem can occur, unless you have one of:

* serial debugging enabled (which isn't compatible with serial console)
* a NS16550A, in which case dwmw2 needs to rework his autodetect code to
  adjust the baud rate appropriately.

I suspect your case is the latter.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core

Re: Garbage on serial console after serial driver loads

[Luca]

Il Fri, Mar 25, 2005 at 08:38:53PM +0000, Russell King ha scritto: 
> On Fri, Mar 25, 2005 at 09:24:15PM +0100, Luca wrote:
> > I attached a null modem cable to my notebook and I'm seeing garbage as
> > soon as the serial driver is loaded. I tried booting with init=/bin/bash
> > to be sure that it's not some rc script doing strange things to the
> > serial port, but this didn't solve the problem.
> 
> I'm uncertain how this problem can occur, unless you have one of:
> 
> * serial debugging enabled (which isn't compatible with serial console)

Do you mean #define DEBUG in serial_core.c? No.

> * a NS16550A, in which case dwmw2 needs to rework his autodetect code to
>   adjust the baud rate appropriately.

Well, serial_core seems to think so:

Serial: 8250/16550 driver $Revision: 1.90 $ 8 ports, IRQ sharing disabled
ttyS0 at I/O 0x3f8 (irq = 4) is a NS16550A
ttyS1 at I/O 0x2f8 (irq = 3) is a NS16550A
ttyS0 at I/O 0x3f8 (irq = 4) is a NS16550A

Luca
-- 
Home: http://kronoz.cjb.net
La mia opinione puo` essere cambiata, ma non il fatto che ho ragione.

Re: Garbage on serial console after serial driver loads

[Luca]

Il Sat, Mar 26, 2005 at 11:16:09AM +0100, Jan Engelhardt ha scritto: 
> >Well, serial_core seems to think so:
> >
> >Serial: 8250/16550 driver $Revision: 1.90 $ 8 ports, IRQ sharing disabled
> >ttyS0 at I/O 0x3f8 (irq = 4) is a NS16550A
> >ttyS1 at I/O 0x2f8 (irq = 3) is a NS16550A
> >ttyS0 at I/O 0x3f8 (irq = 4) is a NS16550A
> 
> Does it work if you set the baud rate manually, as a bootloader option?

I'm using console=ttyS0,38400n8. But it also happens with 9600, 57600
and 115200.

Luca
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Home: http://kronoz.cjb.net
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Mi piace essere il peggiore della compagnia.