e0580929f4
When synchronizing a PHC to the Linux system clock (CLOCK_REALTIME),
the phc2sys uses the sysoff method, reversing the master and slave
roles.
The offset between a master clock and a slave clock is given by
offset = slave_ts - master_ts,
and the call to sysoff_measure() provides the 'offset' and 'slave_ts'
values. The needed local time stamp on the 'master' is given by
master_ts = slave_ts - offset,
but the code calcuates
master_ts = slave_ts + offset.
When passed to the servo, the local time stamp is used to estimate the
frequency offset between the two clocks before starting the main
synchronization loop. The effect of the bug may be seen with a simple
test. Here is a sample output with the existing code.
$ sudo testptp -d /dev/ptp1 -f 62400000
frequency adjustment okay
$ sudo ./phc2sys -m -q -c eth6 -s CLOCK_REALTIME -O0
phc2sys[90221.239]: eth6 sys offset 191001318 s0 freq -62400000 delay 5547
phc2sys[90222.239]: eth6 sys offset 253380897 s1 freq +8265884 delay 5507
phc2sys[90223.239]: eth6 sys offset -8301685 s2 freq -35801 delay 5487
phc2sys[90224.239]: eth6 sys offset -8297136 s2 freq -2521757 delay 5531
phc2sys[90225.239]: eth6 sys offset -5806117 s2 freq -2519879 delay 5542
phc2sys[90226.239]: eth6 sys offset -3317009 s2 freq -1772606 delay 5495
phc2sys[90227.240]: eth6 sys offset -1575231 s2 freq -1025931 delay 5505
phc2sys[90228.240]: eth6 sys offset -580249 s2 freq -503518 delay 5524
phc2sys[90229.240]: eth6 sys offset -107770 s2 freq -205114 delay 5519
phc2sys[90230.240]: eth6 sys offset 66298 s2 freq -63377 delay 5490
phc2sys[90230.881]: eth6 sys offset 86942 s2 freq -22844 delay 5495
And this is the output with the bug fix in place.
$ sudo testptp -d /dev/ptp1 -f 62400000
frequency adjustment okay
$ sudo ./phc2sys -m -q -c eth6 -s CLOCK_REALTIME -O0
phc2sys[90365.624]: eth6 sys offset 311912675 s0 freq -62400000 delay 5490
phc2sys[90366.624]: eth6 sys offset 374292766 s1 freq -31098 delay 5642
phc2sys[90367.624]: eth6 sys offset -3825 s2 freq -34923 delay 5617
phc2sys[90368.625]: eth6 sys offset 6 s2 freq -32240 delay 5564
phc2sys[90369.625]: eth6 sys offset 1241 s2 freq -31003 delay 5605
phc2sys[90370.625]: eth6 sys offset 1131 s2 freq -30741 delay 5600
phc2sys[90371.625]: eth6 sys offset 801 s2 freq -30732 delay 5621
phc2sys[90372.625]: eth6 sys offset 458 s2 freq -30834 delay 5640
phc2sys[90373.626]: eth6 sys offset 186 s2 freq -30969 delay 5598
phc2sys[90374.626]: eth6 sys offset 134 s2 freq -30965 delay 5599
phc2sys[90375.626]: eth6 sys offset 43 s2 freq -31016 delay 5595
phc2sys[90375.681]: eth6 sys offset -32 s2 freq -31078 delay 5541
This patch fixes the issue by correcting the calculation of the local
time stamp value.
Fixes: 8142da41b61f ("phc2sys: Use reversed sysoff when synchronizing to system clock.")
Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Reported-by: Cliff Spradlin <cspradlin@google.com>
Tested-by: Vladimir Oltean <olteanv@gmail.com>
- Introduction
- License
- Features
- Getting the Code
- System Requirements
- Installation
- Getting Involved
- Thanks
Introduction
This software is an implementation of the Precision Time Protocol (PTP) according to IEEE standard 1588 for Linux. The dual design goals are to provide a robust implementation of the standard and to use the most relevant and modern Application Programming Interfaces (API) offered by the Linux kernel. Supporting legacy APIs and other platforms is not a goal.
License
The software is copyrighted by the authors and is licensed under the GNU General Public License. See the file, COPYING, for details of the license terms.
Features
- Supports hardware and software time stamping via the Linux SO_TIMESTAMPING socket option.
- Supports the Linux PTP Hardware Clock (PHC) subsystem by using the clock_gettime family of calls, including the clock_adjtimex system call.
- Implements Boundary Clock (BC), Ordinary Clock (OC) and Transparent Clock (TC).
- Transport over UDP/IPv4, UDP/IPv6, and raw Ethernet (Layer 2).
- Supports IEEE 802.1AS-2011 in the role of end station.
- Modular design allowing painless addition of new transports and clock servos.
- Implements unicast operation.
-
Supports a number of profiles, including:
- The automotive profile
- The default 1588 profile.
- The enterprise profile.
- The telecom profiles G.8265.1, G.8275.1, and G.8275.2.
- Supports the NetSync Monitor protocol.
- Implements Peer to peer one-step.
- Supports bonded, IPoIB, and vlan interfaces.
Getting the Code
You can download the latest released version at Source Forge.
http://sourceforge.net/projects/linuxptp/files/latest/download
The source code is managed using the git version control system. To get your own copy of the project sources, use the following command.
git clone git://git.code.sf.net/p/linuxptp/code linuxptp
If the git protocol is blocked by your local area network, then you can use the alternative HTTP protocol instead.
git clone http://git.code.sf.net/p/linuxptp/code linuxptp
System Requirements
In order to run this software, you need Linux kernel version 3.0 or newer. Check whether your network interface supports PTP with the following command.
ethtool -T eth0
This command shows whether a MAC supports hardware or software time stamping. The following example output indicates support for hardware time stamping.
Time stamping parameters for eth6:
Capabilities:
hardware-transmit (SOF_TIMESTAMPING_TX_HARDWARE)
software-transmit (SOF_TIMESTAMPING_TX_SOFTWARE)
hardware-receive (SOF_TIMESTAMPING_RX_HARDWARE)
software-receive (SOF_TIMESTAMPING_RX_SOFTWARE)
software-system-clock (SOF_TIMESTAMPING_SOFTWARE)
hardware-raw-clock (SOF_TIMESTAMPING_RAW_HARDWARE)
PTP Hardware Clock: 1
Hardware Transmit Timestamp Modes:
off (HWTSTAMP_TX_OFF)
on (HWTSTAMP_TX_ON)
Hardware Receive Filter Modes:
none (HWTSTAMP_FILTER_NONE)
all (HWTSTAMP_FILTER_ALL)
The next example shows the case where the MAC only supports software
time stamping. The ptp4l program requires either the -S command
line argument or the time_stamping software configuration option
when using such interfaces.
Time stamping parameters for enp6s0:
Capabilities:
software-transmit (SOF_TIMESTAMPING_TX_SOFTWARE)
software-receive (SOF_TIMESTAMPING_RX_SOFTWARE)
software-system-clock (SOF_TIMESTAMPING_SOFTWARE)
PTP Hardware Clock: none
Hardware Transmit Timestamp Modes: none
Hardware Receive Filter Modes: none
Note the software-transmit (SOF_TIMESTAMPING_TX_SOFTWARE)
capability. If this is lacking, then the MAC cannot be used at
all. However, adding this capability entails adding a single line
of code to the device driver.
Installation
- Just type 'make'
- If you compiled your own kernel (and the headers are not installed into the system path), then you should set the KBUILD_OUTPUT environment variable as in the example, above.
- In order to install the programs and man pages into /usr/local, run the 'make install' target. You can change the installation directories by setttings the variables prefix, sbindir, mandir, and man8dir on the make command line.
Getting Involved
The software development is hosted at Source Forge.
https://sourceforge.net/projects/linuxptp/
Reporting Bugs
Please report any bugs or other issues with the software to the linuxptp-users mailing list.
Development
If you would like to get involved in improving the software, please join the linuxptp-devel mailing list.
https://lists.sourceforge.net/lists/listinfo/linuxptp-devel
Submitting Patches
- Before submitting patches, please make sure that you are starting your work on the current HEAD of the git repository.
- Please checkout the
CODING_STYLE.orgfile for guidelines on how to properly format your code. - Describe your changes. Each patch will be reviewed, and the reviewers need to understand why you did what you did.
-
Sign-Off each commit, so the changes can be properly attributed to you and you explicitely give your agreement for distribution under linuxptp's license. Signing-off is as simple as:
git commit -s
or by adding the following line (replace your real name and email) to your patch:
Signed-off-by: Random J Developer <random@developer.example.org>
-
Finally, send your patches via email to the linuxptp-devel mailing list, where they will be reviewed, and eventually be included in the official code base.
git send-email --to linuxptp-devel@lists.sourceforge.net origin/master
Thanks
Thanks to AudioScience Inc for sponsoring the 8021.AS support.
Thanks to Exablaze for donating an ExaNIC X10
Thanks to Intel Corporation for donating four NICs, the 82574, 82580, 82599, and the i210.
Thanks to Meinberg Funkuhren for donating a LANTIME M1000.
Thanks to Moser Baer for sponsoring the Telecom Profiles and unicast support.
For testing I use an OTMC 100 grandmaster clock donated by OMICRON Lab.