[SLL] trouble with extra serial ports. doesn't look like irq problems...

[Ben Johnson]

On Mon, May 02, 2005 at 10:39:56AM -0700, Chuck Wolber wrote:
...
> I'm *ASSUMING* you're doing this on a Linux system (you didn't explicitly 
> say so and /dev/ttyS0 can be found on other *IX systems). If so, you need 
> to ensure that you've compiled support for extra serial ports into your 
> kernel.

it is a Linux system.  yep.  I'm using a standard Debian 2.6.8 kernel,
which appears to have support for extra serial ports built in.

#from dmesg:
Serial: 8250/16550 driver $Revision: 1.90 $ 48 ports, IRQ sharing enabled
ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A
ttyS2 at I/O 0x3e8 (irq = 4) is a 16550A
ttyS3 at I/O 0x2e8 (irq = 3) is a 16550A


#from /boot/config-2.6.8-2-686 (corresponds to the running kernel)

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

I'm thinking the "48 ports" bit in the dmesg output is telling me the
kernel should be able to support up to device /dev/ttyS47.  I think I've
eliminate IRQ sharing issues by assigning the first two ports different
IRQs and letting the last two have exclusive ownership of some known
working IRQs.

I don't know how to tell what kind of bus these ports are on.  (ISA or
PCI?)  they're soldered onto the main board, which makes me think ISA.
even so, I think all my IRQ debugging would have taken care of the
typical ISA issues.

I ordered two identical system and I'm going to try out the second one
today.  That should make for an interesting test.

Thanks for the input.

- Ben