The Linux PTP Project

1 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.

2 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.

3 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 new clock_adjtimex system call.
  • Implements Boundary Clock (BC) and Ordinary Clock (OC).
  • 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.

4 Getting the Code

You can download the latest released version at Source Forge.

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:// linuxptp

If the git protocol is blocked by your local area network, then you can use the alternative HTTP protocol instead.

git clone linuxptp

5 System Requirements

In order to run this software, you need Linux kernel version 3.0 or newer, and the kernel header files must available at compile time.

In addition, you will also need to have either:

  1. A supported Ethernet MAC device.
  2. A supported PHY device paired with a MAC that allows time stamping in the PHY (indicated by PHY=Y in the table below).

5.1 Linux Kernel Support

In order to support PTP, the operating system needs to provide two services: network packet time stamping and clock control. In 2009, Patrick Ohly added a new socket option called SO_TIMESTAMPING for packet time stamping, especially for PTP. This work appeared in Linux version 2.6.30.

In July of 2011, the PTP Hardware Clock (PHC) subsystem was merged into Linux version 3.0. The PHC code provides a driver framework and the user space API for clock control.

5.2 Ethtool Support

Starting with version 3.5 of the Linux kernel, you can query the time stamping capabilities of a network interface using the ETHTOOL_GET_TS_INFO ioctl. Using ethtool version 3.4 or later, you can check your system's time stamping support as shown in the following example.

ethtool -T eth0

If the ethtool ioctl is available, then the ptp4l program will use it in order to discover the proper PHC device.

5.3 Driver Support Matrix

The following two tables list the drivers that support the PHC subsystem and the Linux kernel version when they first appeared. These drivers will create a PHC device for controlling the hardware clock.

5.3.1 Hardware Timestamping - PHY

Driver Hardware Version
dp83640 National Semiconductor PHYTER 3.0

5.3.2 Hardware Timestamping - MAC

Driver Hardware Version
amd-xgbe AMD 10GbE Ethernet Soc 3.17
bfin_mac Analog Blackfin 3.8
bnx2x Broadcom NetXtremeII 10G 3.18
cpts Texas Instruments am335x 3.8
e1000e Intel 82574, 82583 3.9
fm10k Intel FM10000 3.18
fec Freescale i.mx6 3.8
gianfar Freescale eTSEC PowerPC 3.0
i40e Intel XL710 Family 3.14
igb Intel 82576, 82580 3.5
ixgbe Intel 82599 3.5
mlx4 Mellanox 40G PCI 3.14
ptp_ixp46x Intel IXP465 3.0
ptp_phc Lapis EG20T PCH 3.5
sfc Solarflare SFC9000 3.7
stmmac STM Synopsys IP Core 3.10
tg3 Broadcom Tigon3 PCI 3.8
tilegx Tilera GBE/XGBE 3.12

5.3.3 Software Timestamping

The table below shows the Linux drivers that support software time stamping. In addition, the 'PHY' column indicates whether the Ethernet MAC driver can support a PTP Hardware Clock in an external PHY. The letter 'Y' in this column means that if you design a mother board that combines such a MAC with a PTP capable PHY, then it will work with the Linux PHC subsystem.

Driver Hardware Version PHY
3c59x 3Com EtherLink PCI 3.14 N
altera_tse Altera Triple-Speed MAC 3.15 Y
bna Brocade 1010/1020 10Gb 3.14 N
bnx2x Broadcom Everest 3.5 N
davinci_emac TI DaVinci, Sitara 3.1 Y
dnet Dave Ethernet MAC 3.1 Y
e100 Intel PRO/100 3.5 N
e1000 Intel PRO/1000 PCI/PCI-X 3.5 N
e1000e Intel PRO/1000 PCIe 3.5 N
emaclite Xilinx Ethernet Lite 3.1 Y
ethoc OpenCores 10/100 MAC 3.1 Y
fec Freescale Coldfire 3.1 Y
fec_mpc52xx Freescale MPC5200 3.1 Y
forcedeth NVIDIA nForce 3.5 N
fs_enet Freescale MPC512x 3.1 Y
genet Broadcom GENET 3.15 Y
ixp4xx_eth Intel IXP4xx 3.0 Y
lib8390 Asix AX88796 3.1 Y
lib8390 Various 8390 based HW 3.1 N
ll_temac Xilinx LL TEMAC 3.1 Y
macb Atmel AT32, AT91 3.1 Y
mv643xx_eth Marvell Discovery, Orion 3.1 Y
pxa168_eth Marvell pxa168 3.1 Y
r6040 RDC Ethernet MAC 3.1 Y
r8169 Realtek 8169/8168/8101 3.4 N
samsun-sxgbe Samsung SXGBE 10G 3.15 Y
smsc911x SMSC LAN911x, LAN921x 3.1 Y
smsc9420 SMSC LAN9420 PCI 3.1 Y
stmmac STM Synopsys IP Core 3.1 Y
tg3 Broadcom Tigon3 PCI 3.1 Y
ucc_geth Freescale QE Gigabit 3.1 Y
usbnet USB network devices 3.2 Y/N
xgene-enet APM X-Gene SoC 3.17 Y

6 Installation

6.1 Linux kernel

There are many ways of getting a precompiled Linux kernel or compiling your own, so this section is only meant as an example. It is important to have the kernel headers available when compiling the Linux PTP stack.

export ARCH=x86
export KBUILD_OUTPUT=/home/richard/kernel/ptp_debian
cp /boot/config-2.6.38-bpo.2-686 $KBUILD_OUTPUT/.config
make oldnoconfig
make menuconfig
time make -j4
make headers_install

Here is a table of kernel configuration options needed for PTP support. In addtion to these, you should enable the specific Ethernet MAC and PHY drivers for your hardware.

Option Description
PTP_1588_CLOCK PTP clock support

6.2 PTP stack

  1. Just type 'make'
  2. 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.
  3. 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.

7 Getting Involved

The software development is hosted at Source Forge.

7.1 Reporting Bugs

Please report any bugs or other issues with the software to the linuxptp-users mailing list.

7.2 Development

If you would like to get involved in improving the software, please join the linuxptp-devel mailing list.

7.2.1 Submitting Patches

  1. Before submitting patches, please make sure that you are starting your work on the current HEAD of the git repository.
  2. Please checkout the file for guidelines on how to properly format your code.
  3. Describe your changes. Each patch will be reviewed, and the reviewers need to understand why you did what you did.
  4. 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 <>
  5. 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 origin/master

8 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.

For testing I use an OTMC 100 grandmaster clock donated by OMICRON Lab.