Re: new NTP/PPS patch available

Markus Gutschke (
9 Dec 1996 17:39:10 +0100

"Theodore Y. Ts'o" <> writes:
> I'm assuming here that the irq isn't being shared with any other serial
> port, and is only being used for the radio clock. In that case, you're
> going to be have to read the time from the counter, etc. in any case.
> The only question is where you do it. You might as well do it as close
> to the beginning of the interrupt processing as possible.
> Note that this is on a per-IRQ basis only! And I think it's reasonable
> to assume that you won't be trying to share the serial port with any
> other ports, since that's when you get into lots of problems with
> variable amounts of time needed to poll several UARTs.

Actually, sharing interrupts is exactly what I do here. Due to lack of
free interrupts, my system has an AST 4-port card for its serial
lines. As my mainboard's clock is off by several seconds a day, I
installed a radio controlled PPS signal that adjusts the system
time. I currently use Harald's patches for generating time-stamped
events and I installed his "dcf" program for evaluating the data. I do
not care very much about absolute accuracy, but I would be very
annoyed if the system load was increased because of time-stamping each
event on any of my four serial ports. Please consider this
application, when designing the new code for the serial ports.


Markus Gutschke            Internet:
Schlage 5a
D-48268 Greven-Gimbte