Serial Ports

Serial Ports

[Stephen Torri]

Should serial ports be assigned interrupts on start up or are they
assigned when they are used? I have been tracking the serial ports on my
Supermicro Dual P3 Board for a few days now. At times I cannot get them to
work so I can syncronize a Palm Pilot via the serial port.

Stephen

Re: Serial Ports

[Stuart MacDonald]

From: "Stephen Torri" <storri@ameritech.net>
> Should serial ports be assigned interrupts on start up or are they
> assigned when they are used? I have been tracking the serial ports on my
> Supermicro Dual P3 Board for a few days now. At times I cannot get them to
> work so I can syncronize a Palm Pilot via the serial port.

On-board serial ports are given either the standard irqs, or the
irqs that you specify in the bios. ISA and other non-self-identifying-
bus-based ports will be given the irqs you specify in the configuration
of the device. PCI and other self-identifying-bus-based ports will
be assigned free or sharable irqs by the bios/os. All serial hardware
is assigned an irq. This is the hardware level.

I think what you're asking is "When I cat /proc/irq, should I see the
serial ports listed at boot, or only after I've used them?" The answer
to that is that the standard serial driver only registers to use the
irq that has been assigned, when it needs to use it. So if you check
before usage, you won't see your ports.

..Stu

Re: Serial Ports

[Stephen Torri]

On Wed, 5 Sep 2001, D. Stimits wrote:

> Make sure your bios is set to "not plug-n-play aware". I have a
> Supermicro Dual P3 board that works fine (actually, 2) with serial mice.
> In the case of the modem serial port, I have to use setserial to get the
> characteristics I want, plus the setserial options seem to require
> speed_normal and skip_test to work correctly. Incidentally, if your
> board is based on the i840 chipset, you'll have to run noapic or it will
> die under some circumstances, such as heavy disk load, or rapid
> mount/umount of any filesystem (even a cdrom).
>
> D. Stimits, stimits@idcomm.com

I have noticed that serial ports change IRQ to either 3 or 4. There is no
reason for this behavior. I have created a perl script to create a log
containing the irqs assigned and their ioports. Is there anything else I
could log that might unmask the problem?

So far if the serials are assigned to IRQ 4 then the sync with the palm
pilot doesn't work (/dev/pilot = /dev/ttyS0). If its IRQ 3 then it does.

Stephen

Re: Serial Ports

[Stuart MacDonald]

From: "Stephen Torri" <storri@ameritech.net>
> I have noticed that serial ports change IRQ to either 3 or 4. There is no
> reason for this behavior. I have created a perl script to create a log
> containing the irqs assigned and their ioports. Is there anything else I
> could log that might unmask the problem?

Try posting the contents of /proc/irqs and /proc/ioports, perhaps
someone here will see something you don't.

..Stu

Re: Serial Ports

[Ian D . Stewart]

On 2001.09.06 16:27:06 -0400 Stephen Torri wrote:

> 
> I have noticed that serial ports change IRQ to either 3 or 4. There is no
> reason for this behavior. I have created a perl script to create a log
> containing the irqs assigned and their ioports. Is there anything else I
> could log that might unmask the problem?
> 
> So far if the serials are assigned to IRQ 4 then the sync with the palm
> pilot doesn't work (/dev/pilot = /dev/ttyS0). If its IRQ 3 then it does.

As I understand it, /dev/ttyS0-3 are set to industry standard values on
startup (they are not probed).  The values can be changed using the
command-line utility setserial.  You can specify non-standard values in an
rc.serial conf file which will be read on startup.

The setserial manpage covers this is some detail.


HTH,
Ian

-- 
"God may have mercy.  We will not."
--Senator John S. McCain (R-AZ)