This introduces the '-a' option in ts2phc, an option inspired from
phc2sys that puts the clocks in "automatic" mode. In this mode, ts2phc
listens, as a PMC, to port state change events from ptp4l, and detects
which port state machine, if any, has transitioned to PS_SLAVE. That
port's clock will become the synchronization master for the hierarchy
described by ts2phc.
The use case is a multi-switch DSA setup with boundary_clock_jbod, where
there is only one grandmaster, connected to one switch's port. The other
switches, connected together through a PPS signal, must adapt themselves
to this new source of time, while the switch connected to the GM must
not be synchronized by ts2phc because it is already synchronized by
ptp4l.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
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>
Slaves in ts2phc are PHC devices that implement the extts kernel API.
They are slaves just in the sense that they timestamp a pulse emitted by
somebody else.
Currently in ts2phc, PPS slaves are also the only candidates for the
clocks that get synchronized. There are 2 aspects that make this too
restrictive:
- Not all PPS slaves may be synchronization slaves. Consider a dynamic
environment of multiple DSA switches using boundary_clock_jbod, and
only one port is in the PS_SLAVE state. In that case, the clock of
that port should be the synchronization master (called the "source
clock" from now on, as far as ts2phc is concerned), regardless of
whether it supports the extts API or not.
- Not all synchronization slaves may be PPS slaves. Specifically, the
"PHC" type of PPS master in ts2phc can also be, fundamentally,
disciplined. The code should be prepared to handle this by recognizing
that things that can be disciplined by a servo should be represented
by a "struct clock", and things that can timestamp external events
should be represented by a "struct ts2phc_slave".
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Eliminate the ad-hoc use of global variables in the ts2phc program by
introducing one data structure that incorporates them. This might make
the code more understandable to people coming from a kernel background,
since it resembles the type of data organization used there. It is also
now closer to the data organization of phc2sys, a similar program in
both purpose and implementation.
The reason why this is needed has to do with the ts2phc polymorphism for
a PPS master.
In the next patches, PPS masters will expose a struct clock, which will
be synchronized from the main ts2phc.c.
Not all PPS masters will expose a clock, only the PHC kind will. So the
current object encapsulation model needs to be loosened up little bit,
because the main ts2phc.c needs to synchronize a list of clocks, list
which is populated by the slaves and the masters which are capable of
being synchronized.
So instead of having the translation modules of ts2phc communicate
through global variables, let's make struct ts2phc_private the common
working space for the entire program, which is a paradigm that is more
natural.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Many GPS radios provide both a 1-PPS and time of day information via
NMEA sentences. This patch introduces a ts2phc master that decodes
the "recommended minimum data" sentence, RMC, which provides UTC time
and a validity flag. Together with the file based leap second table,
this sentence provides adequate time of day for determining the time
of the PPS edge.
Signed-off-by: Richard Cochran <richardcochran@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>
Some PTP Hardware Clocks have input pins that can generate time stamps
on the edges of external signals. This functionality can be used in
various ways. For example, one can synchronize a PHC device to a
global time source by taking a Pulse Per Second signal from the source
into the PHC. This patch adds support for synchronizing one or more
PHC slaves to a given master clock.
The implementation follows a modular design that allows adding
different kinds of master clocks in the future. This patch starts off
with a single "generic" PPS master, meaning a PPS signal that lacks
and time or date information. The generic master assumes that the
Linux system time is approximately correct (by NTP or RTC for example)
in order to calculate the time of the incoming PPS edges.
Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Balint Ferencz <fernya@gmail.com>
Vladimir Oltean
Richard Cochran