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Document PTP time scale usage and provide examples 

Signed-off-by: Libor Pechacek <lpechacek@suse.cz>
master
Libor Pechacek 2013-05-17 10:55:48 +02:00 committed by Richard Cochran
parent 3f8471ea68
commit 6e4734316f
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67
phc2sys.8
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@ -156,5 +156,72 @@ Display a help message.
.B \-v
Prints the software version and exits.
.SH TIME SCALE USAGE
.B Ptp4l
uses either PTP time scale or UTC (Coordinated Universal Time) time
scale. PTP time scale is continuous and shifted against UTC by a few tens of
seconds as PTP time scale does not apply leap seconds.
In hardware time stamping mode,
.B ptp4l
announces use of PTP time scale and PHC
is used for the stamps. That means PHC must follow PTP time scale while system
clock follows UTC. Time offset between these two is maintained by
.BR phc2sys .
.B Phc2sys
acquires the offset value either by reading it from ptp4l when
.B \-w
is in effect or from command line when
.B \-O
is supplied. Failure to maintain the correct offset can result in local system
clock being off some seconds to domain master system clock when in slave mode,
or incorect PTP time announced to the network in case the host is the domain
master.
.SH EXAMPLES
The host is a domain master, PTP clock is synchronized to system clock and the
time offset is obtained from
.BR ptp4l .
.B Phc2sys
waits for
.B ptp4l
to get at least one port in master or slave mode before starting the
synchronization.
.RS
\f(CWphc2sys \-c /dev/ptp0 \-s CLOCK_REALTIME \-w\fP
.RE
Same as above, time offset is provided on command line and
.B phc2sys
does not wait for
.BR ptp4l .
.RS
\f(CWphc2sys \-c /dev/ptp0 \-s CLOCK_REALTIME \-O 35\fP
.RE
The host is in slave mode, system clock is synchronized from PTP clock,
.B phc2sys
waits for
.B ptp4l
and the offset is set automatically.
.RS
\f(CWphc2sys \-s /dev/ptp0 \-w\fP
.RE
Same as above, PTP clock id is read from the network interface, the offset is
provided on command line
.B phc2sys
does not wait.
.RS
\f(CWphc2sys \-s eth0 \-O \-35\fP
.RE
.SH SEE ALSO
.BR ptp4l (8)

16
ptp4l.8
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@ -366,6 +366,22 @@ one-second offset slowly by changing the clock frequency (unless the
option is set to correct such offset by stepping).
Relevant only with software time stamping. The default is 1 (enabled).
.SH TIME SCALE USAGE
.B ptp4l
as domain master either uses PTP or UTC time scale depending on time stamping
mode. In software and legacy time stamping modes it announces Arbitrary time
scale mode, which is effectively UTC here, in hardware time stamping mode it
announces use of PTP time scale.
When
.B ptp4l
is the domain master using hardware time stamping, it is up to
.B phc2sys
to maintain the correct offset between UTC and PTP times. See
.BR phc2sys (8)
manual page for more details.
.SH SEE ALSO
.BR pmc (8),
.BR phc2sys (8)