beaglebone PPS driver (pulse per second)

[Ian Lepore]

I know a few people here used to use the beaglebone with a PPS signal
(from a GPS or radio clock) for ntpd.  The ability to do that got broken
a few weeks ago with the conversion to vendor-supplied FDT data.

I've rewritten the PPS driver and committed it yesterday.  It's now
separate from the main timecounter driver, and can be loaded as a module
and configured with a loader.conf setting so that you can use it even
with a stock kernel or the downloadable beaglebone images.

To use it as a module, just add to your loader.conf:

   am335x_dmtpps_load="YES"
   hw.am335x_dmtpps.input="P8-7"

And add a devfs rule to symlink /dev/dmtpps to /dev/pps0 for use with
ntpd.  You can set the input pin to any of P8-7 through P8-10, depending
on which pin on the P8 header you want to use for the signal.  The
driver will also continue to work with FDT-based config (it looks for
one of the timer4..timer7 pins to be configured as input).

There is also a manpage for the new driver with more details.

-- Ian