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linuxptp/ptp4l.8
Jacob Keller 76e10e95fb ptp4l: Use poll() instead of a try-again loop 
This patch modifies sk_receive in order to use poll() on POLLERR instead of the
tryagain loop as this resolves issues with drivers who do not return timestamps
quickly enough. It also resolves the issue of wasting time repeating every
microsecond. It lets the kernel sleep our application until the data or timeout arrives.

This change also replaces the old tx_timestamp_retries config value with
tx_timestamp_timeout specified in milliseconds (the smallest length of time poll
accepts). This does have the side effect of increasing the minimum delay before
missing a timestamp by up to 1ms, but the poll should return sooner in the
normal case where a packet timestamp was not dropped.

This change vastly improves some devices and cleans the code up by simplifying a
race condition window due to drivers returning tx timestamp on the error queue.

[ RC - removed the unused 'try_again' variable. ]

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
2013-04-05 20:43:33 +02:00

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.TH PTP4l 8 "November 2012" "linuxptp"
.SH NAME
ptp4l \- PTP Boundary/Ordinary Clock
.SH SYNOPSIS
.B ptp4l
[
.B \-A
|
.B \-E
|
.B \-P
] [
.B \-2
|
.B \-4
|
.B \-6
] [
.B \-H
|
.B \-S
|
.B \-L
] [
.BI \-f " config"
] [
.BI \-p " phc-device"
] [
.B \-s
] [
.BI \-l " print-level"
] [
.B \-m
] [
.B \-q
] [
.B \-v
]
[
.BI \-i " interface"
]
.I .\|.\|.
.SH DESCRIPTION
.B ptp4l
is an implementation of the Precision Time Protocol (PTP) according to IEEE
standard 1588 for Linux. It implements Boundary Clock (BC) and Ordinary Clock
(OC).
.SH OPTIONS
.TP
.B \-A
Select the delay mechanism automatically. Start with E2E and switch to P2P when
a peer delay request is received.
.TP
.B \-E
Select the delay request-response (E2E) mechanism. This is the default
mechanism.
.TP
.B \-P
Select the peer delay (P2P) mechanism.
.TP
.B \-2
Select the IEEE 802.3 network transport.
.TP
.B \-4
Select the UDP IPv4 network transport. This is the default transport.
.TP
.B \-6
Select the UDP IPv6 network transport.
.TP
.B \-H
Select the hardware time stamping. All ports specified by the
.B \-i
option and in the configuration file must be attached to the same PTP hardware
clock (PHC). This is the default time stamping.
.TP
.B \-S
Select the software time stamping.
.TP
.B \-L
Select the legacy hardware time stamping.
.TP
.BI \-f " config"
Read configuration from the specified file. No configuration file is read by
default.
.TP
.BI \-i " interface"
Specify a PTP port, it may be used multiple times. At least one port must be
specified by this option or in the configuration file.
.TP
.BI \-p " phc-device"
With hardware time stamping, force which PHC device (e.g. /dev/ptp0) should be
used.
.TP
.B \-s
Enable the slaveOnly mode.
.TP
.BI \-l " print-level"
Set the maximum syslog level of messages which should be printed or sent to
the system logger. The default is 6 (LOG_INFO).
.TP
.B \-m
Print messages to the standard output.
.TP
.B \-q
Don't send messages to the system logger.
.TP
.B \-v
Prints the software version and exits.
.TP
.BI \-h
Display a help message.
.SH CONFIGURATION FILE
The configuration file is divided into sections. Each section starts with a
line containing its name enclosed in brackets and it follows with settings.
Each setting is placed on a separate line, it contains the name of the
option and the value separated by whitespace characters. Empty lines and lines
starting with # are ignored.
The global section (indicated as
.BR [global] )
sets the program options, clock options and default port options. Other
sections are port specific sections and they override the default port options.
The name of the section is the name of the configured port (e.g.
.BR [eth0] ).
Ports specified in the configuration file don't need to be
specified by the
.B \-i
option. An empty port section can be used to replace the command line option.
.SH PORT OPTIONS
.TP
.B delayAsymmetry
The time difference in nanoseconds of the transmit and receive
paths. This value should be positive when the master-to-slave
propagation time is longer and negative when the slave-to-master time
is longer. The default is 0 nanoseconds.
.TP
.B logAnnounceInterval
The mean time interval between Announce messages. A shorter interval makes
ptp4l react faster to the changes in the master-slave hierarchy. The interval
should be the same in the whole domain. It's specified as a power of two in
seconds.
The default is 1 (2 seconds).
.TP
.B logSyncInterval
The mean time interval between Sync messages. A shorter interval may improve
accuracy of the local clock. It's specified as a power of two in seconds.
The default is 0 (1 second).
.TP
.B logMinDelayReqInterval
The minimum permitted mean time interval between Delay_Req messages. A shorter
interval makes ptp4l react faster to the changes in the path delay. It's
specified as a power of two in seconds.
The default is 0 (1 second).
.TP
.B logMinPdelayReqInterval
The minimum permitted mean time interval between Pdelay_Req messages. It's
specified as a power of two in seconds.
The default is 0 (1 second).
.TP
.B announceReceiptTimeout
The number of missed Announce messages before the last Announce messages
expires.
The default is 3.
.TP
.B transportSpecific
The transport specific field. Must be in the range 0 to 255.
The default is 0.
.TP
.B path_trace_enabled
Enable the mechanism used to trace the route of the Announce messages.
The default is 0 (disabled).
.TP
.B follow_up_info
Include the 802.1AS data in the Follow_Up messages if enabled.
The default is 0 (disabled).
.TP
.B fault_reset_interval
The time in seconds between the detection of a port's fault and the fault
being reset. This value is expressed as a power of two. Setting this
value to -128 or to the special key word "ASAP" will let the fault be
reset immediately.
The default is 4 (16 seconds).
.TP
.B fault_badpeernet_interval
The time in seconds between the detection of a peer network misconfiguration
and the fault being reset. The port is disabled for the duration of the
interval. The value is in seconds and the special key word ASAP will let
the fault be reset immediately.
The default is 16 seconds.
.TP
.B delay_mechanism
Select the delay mechanism. Possible values are E2E, P2P and Auto.
The default is E2E.
.TP
.B network_transport
Select the network transport. Possible values are UDPv4, UDPv6 and L2.
The default is UDPv4.
.TP
.B neighborPropDelayThresh
Upper limit for peer delay in nanoseconds. If the estimated peer delay is
greater than this value the port is marked as not 802.1AS capable.
.SH PROGRAM AND CLOCK OPTIONS
.TP
.B twoStepFlag
Enable two-step mode for sync messages. One-step mode can be used only with
hardware time stamping.
The default is 1 (enabled).
.TP
.B slaveOnly
The local clock is a slave-only clock if enabled.
The default is 0 (disabled).
.TP
.B priority1
The priority1 attribute of the local clock. It is used in the best master
selection algorithm, lower values take precedence. Must be in the range 0 to
255.
The default is 128.
.TP
.B priority2
The priority2 attribute of the local clock. It is used in the best master
selection algorithm, lower values take precedence. Must be in the range 0 to
255.
The default is 128.
.TP
.B clockClass
The clockClass attribute of the local clock. It denotes the traceability of the
time distributed by the grandmaster clock.
The default is 248.
.TP
.B clockAccuracy
The clockAccuracy attribute of the local clock. It is used in the best master
selection algorithm.
The default is 0xFE.
.TP
.B offsetScaledLogVariance
The offsetScaledLogVariance attribute of the local clock. It characterizes the
stability of the clock.
The default is 0xFFFF.
.TP
.B domainNumber
The domain attribute of the local clock.
The default is 0.
.TP
.B free_running
Don't adjust the local clock if enabled.
The default is 0 (disabled).
.TP
.B freq_est_interval
The time interval over which is estimated the ratio of the local and
peer clock frequencies. It is specified as a power of two in seconds.
The default is 1 (2 seconds).
.TP
.B assume_two_step
Treat one-step responses as two-step if enabled. It is used to work around
buggy 802.1AS switches.
The default is 0 (disabled).
.TP
.B tx_timestamp_timeout
The number of milliseconds to poll waiting for the tx time stamp from the kernel
when a message has recently been sent.
The default is 1.
.TP
.B clock_servo
The servo which is used to synchronize the local clock. Currently only one
servo is implemented, a PI controller.
The default is pi.
.TP
.B pi_proportional_const
The proportional constant of the PI controller. When set to 0.0, the value will
be selected from 0.7 and 0.1 for the hardware and software time stamping
respectively.
The default is 0.0.
.TP
.B pi_integral_const
The integral constant of the PI controller. When set to 0.0, the value will be
selected from 0.3 and 0.001 for the hardware and software time stamping
respectively.
The default is 0.0.
.TP
.B pi_offset_const
The maximum offset the PI controller will correct by changing the clock
frequency instead of stepping the clock. When set to 0.0, the controller will
never step the clock.
The default is 0.0.
.TP
.B ptp_dst_mac
The MAC address where should be PTP messages sent.
Relevant only with L2 transport. The default is 01:1B:19:00:00:00.
.TP
.B p2p_dst_mac
The MAC address where should be peer delay messages the PTP peer.
Relevant only with L2 transport. The default is 01:80:C2:00:00:0E.
.TP
.B udp6_scope
Specifies the desired scope for the IPv6 multicast messages. This
will be used as the second byte of the primary address. This option
is only relevant with IPv6 transport. See RFC 4291. The default is
0x0E for the global scope.
.TP
.B logging_level
The maximum logging level of messages which should be printed.
The default is 6 (LOG_INFO).
.TP
.B verbose
Print messages to the standard output if enabled.
The default is 0 (disabled).
.TP
.B use_syslog
Print messages to the system log if enabled.
The default is 1 (enabled).
.TP
.B summary_interval
The time interval in which are printed summary statistics of the clock. It is
specified as a power of two in seconds. The statistics include offset root mean
square (RMS), maximum absolute offset, frequency offset mean and standard
deviation, and path delay mean and standard deviation. The units are
nanoseconds and parts per billion (ppb). If there is only one clock update in
the interval, the sample will be printed instead of the statistics. The
messages are printed at the LOG_INFO level.
The default is 0 (1 second).
.TP
.B time_stamping
The time stamping method. The allowed values are hardware, software and legacy.
The default is hardware.
.TP
.B productDescription
The product description string. Allowed values must be of the form
manufacturerName;modelNumber;instanceIdentifier and contain at most 64
utf8 symbols. The default is ";;".
.TP
.B revisionData
The revision description string which contains the revisions for node
hardware (HW), firmware (FW), and software (SW). Allowed values are of
the form HW;FW;SW and contain at most 32 utf8 symbols. The default is
an ";;".
.TP
.B userDescription
The user description string. Allowed values are of the form
name;location and contain at most 128 utf8 symbols. The default is an
empty string.
.TP
.B manufacturerIdentity
The manufacturer id which should be an OUI owned by the manufacturer.
The default is 00:00:00.
.TP
.B kernel_leap
When a leap second is announced, let the kernel apply it by stepping the clock
instead of correcting the one-second offset with servo, which would correct the
one-second offset slowly by changing the clock frequency (unless the
.B pi_offset_const
option is set to correct such offset by stepping).
Relevant only with software time stamping. The default is 1 (enabled).
.SH SEE ALSO
.BR pmc (8),
.BR phc2sys (8)
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