[LinuxPPS] kernel does not see PPS on serial port

[Cirilo Bernardo]

On Fri, Mar 7, 2008 at 7:20 PM, LICHTENBERGER Janos <lityi at sas.elte.hu> wrote:
[snip]
>  > If you look into /proc/interrupts do you see that the interrupts
>  > counter of the serial line is increasing?
>  >
>  No, not at all. I booted with the old 2.6.15.7 kernel and in this case the
>  interrupt counter steadily increased. May it mean that something is wrong
>  with serial port? The port itself is working, I tried with an app reading
>  and writing data through the port (it does not use pin 1 howvever).
>
[snip]

Do you mean you booted your new computer with the older kernel to
check that PPS works and it does work?

Rodolfo suggested the "cat /dev/ttyS0" because the serial port drivers
are designed to disable the UART interrupts unless someone opens the
device for communication.  This makes sense for the usual case -
unless you are expecting data, why even watch the serial port.  The
result of course is that you will not get the DCD interrupt unless you
open the serial port - even if you never actually use the serial port
data.

I'm asking if you used the older kernel on the same hardware because
some hardware only implements the Rx/Tx lines and not the DCD and
other lines, so if you tested on two different machines then that is
not a valid test.

Another problem I encounter is that the 8250 driver in particular
tries to work around faults in numerous UART hardware which claims to
be compatible with the old 8250.  Sometimes hardware is not identified
correctly and the wrong driver is loaded.  In such a case, you can see
what driver is associated with your serial port in your old kernel and
in your new kernel.

Yet another problem I encounter is with power management features on
some boards and in some BIOSes.  Recently I found that with one board
I have, I need to check the BIOS settings and turn off the "power
management features active on boot" feature.  If it is active, then
some peripherals are shut down on boot and Linux does not realize this
or have any obvious mechanism for turning these peripherals on.  Well,
maybe it is possible to turn on via the ACPI or APM interface, but for
my purpose I don't even see the point in disabling these peripherals.