1.1.6 build fails on FC30

[Hal Murray]

>> If so, you must use the clear edge of the PPS (flag2 1).
> Why is that?

Which edge you should use depends on the device and how you wired it up.

Most PPS devices are setup so you should use the rising/assert edge.  If you 
run it through an RS-232 level shifter, they contain an inverter so you should 
use the other edge.

If the width of the PPS is wide enough, you can figure out which edge to use 
by looking at the output from ntpq -p when the system time is close, probably 
because ntpd is using other NTP servers.  Typical low cost GPS units have a 
100 ms or 500 ms pulse.  If it is off that much, try the other edge.

If you have a high end system with a narrow PPS, I'd try something like:
  $ cat /sys/devices/virtual/pps/pps0/{assert,clear}
You have to do that after setting up the PPS but before running ntpd.  It 
disables the edge it's not using.


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