This propagates the use of "struct ts2phc_private" all the way into the
master API, in preparation of a new use case that will be supported
soon: some PPS masters (to be precise, the "PHC" kind) instantiate a
struct clock which could be disciplined by ts2phc.
When a PHC A emits a pulse and another PHC B timestamps it, the offset
between their precise timestamps can be used to synchronize either one
of them. So far in ts2phc, only the slave PHC (the one using extts) has
been synchronized to the master (the one using perout).
This is partly because there is no proper kernel API to report the
precise timestamp of a perout pulse. We only have the periodic API, and
that doesn't report precise timestamps either; we just use vague
approximations of what the PPS master PHC's time was, based on reading
that PHC immediately after a slave extts event was received by the
application. While this is far from ideal, it does work, and does allow
PHC A to be synchronized to B.
This is particularly useful with the yet-to-be-introduced "automatic"
mode of ts2phc (similar to '-a' of phc2sys), and the PPS distribution
tree is fixed in hardware (as opposed to port states, which in
"automatic" mode are dynamic, as the name suggests).
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
This patch introduces a new ts2phc source using a PHC device. There
are multiple use cases for such a master. By connecting pins of two
or more separate PHC devices together, one may act as the source, and
the others may be synchronized to it in hardware. In this way, "just
a bunch of devices" together forms a Transparent Clock. If the master
clock is synchronized to a global time source (like a PPS from a GPS),
then the system becomes a mutli-port Grand Master or a Boundary Clock
with GM capability.
Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Vladimir Oltean
Richard Cochran