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.
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.
- 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.
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
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:
- A supported Ethernet MAC device.
- A supported PHY device paired with a MAC that allows time stamping in the PHY (indicated by PHY=Y in the table below).
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.
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.
The table below shows the Linux drivers that support the new API. The meaning of the column abbreviations is as follows.
- SOTS: SO_TIMESTAMPING support. This comes in three flavors.
- RAW: Supports time stamping using the PHC time values.
- SW: Supports software time stamping using the system time.
- SYS: Supports time stamping using PHC time values scaled to the system time. This is a legacy mode and its use in new drivers is discouraged.
- PHC: PTP Hardware Clock support. These drivers will offer a character device that allows direct control of the hardware clock.
- PHY: Supports time stamping in the PHY. This indicates an Ethernet MAC driver supporting SO_TIMESTAMPING and PHC in the PHY. If you have or build a computer that combines this MAC with a PTP capable PHY, then it will work with the Linux PHC subsystem.
- VER: Linux kernel version when the PTP API support was added.
| Driver | Hardware | SOTS | PHC | PHY | VER |
|---|---|---|---|---|---|
| bfin_mac | Analog Blackfin | SYS | N | NA | pre 3.0 |
| igb | Intel 82576, 82580 | RAW | Y | NA | 3.5 |
| ixgbe | Intel 82599 | RAW | Y | NA | 3.5 |
| dp83640 | Nat Semi PHYTER | RAW | Y | NA | 3.0 |
| gianfar | Freescale eTSEC PowerPC | RAW | Y | NA | 3.0 |
| ptp_ixp46x | Intel IXP465 | RAW | Y | NA | 3.0 |
| ptp_phc | Lapis EG20T PCH | RAW | Y | NA | 3.5 |
| Driver | Hardware | SOTS | PHC | PHY | VER |
|---|---|---|---|---|---|
| bnx2x | Broadcom Everest | SW | N | N | 3.5 |
| davinci_emac | TI DaVinci, Sitara | SW | N | Y | 3.1 |
| dnet | Dave Ethernet MAC | SW | N | Y | 3.1 |
| e100 | Intel PRO/100 | SW | N | N | 3.5 |
| e1000 | Intel PRO/1000 PCI/PCI-X | SW | N | N | 3.5 |
| e1000e | Intel PRO/1000 PCIe | SW | N | N | 3.5 |
| emaclite | Xilinx Ethernet Lite | SW | N | Y | 3.1 |
| ethoc | OpenCores 10/100 MAC | SW | N | Y | 3.1 |
| fec | Freescale Coldfire | SW | N | Y | 3.1 |
| fec_mpc52xx | Freescale MPC5200 | SW | N | Y | 3.1 |
| forcedeth | NVIDIA nForce | SW | N | N | 3.5 |
| fs_enet | Freescale MPC512x | SW | N | Y | 3.1 |
| ixp4xx_eth | Intel IXP4xx | SW | N | Y | 3.0 |
| lib8390 | Asix AX88796 | SW | N | Y | 3.1 |
| lib8390 | Various 8390 based HW | SW | N | N | 3.1 |
| ll_temac | Xilinx LL TEMAC | SW | N | Y | 3.1 |
| macb | Atmel AT32, AT91 | SW | N | Y | 3.1 |
| mv643xx_eth | Marvell Discovery, Orion | SW | N | Y | 3.1 |
| pxa168_eth | Marvell pxa168 | SW | N | Y | 3.1 |
| r6040 | RDC Ethernet MAC | SW | N | Y | 3.1 |
| r8169 | Realtek 8169/8168/8101 | SW | N | N | 3.4 |
| smsc911x | SMSC LAN911x, LAN921x | SW | N | Y | 3.1 |
| smsc9420 | SMSC LAN9420 PCI | SW | N | Y | 3.1 |
| stmmac | STM Synopsys IP Core | SW | N | Y | 3.1 |
| tg3 | Broadcom Tigon3 PCI | SW | N | Y | 3.1 |
| ucc_geth | Freescale QE Gigabit | SW | N | Y | 3.1 |
| usbnet | USB network devices | SW | N | Y/N | 3.2 |
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 CROSS_COMPILE= export KBUILD_OUTPUT=/home/richard/kernel/ptp_debian mkdir -p $KBUILD_OUTPUT 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 |
|---|---|
| CONFIG_EXPERIMENTAL | Required |
| CONFIG_PPS | Required |
| CONFIG_NETWORK_PHY_TIMESTAMPING | Timestamping in PHY devices |
| PTP_1588_CLOCK | PTP clock support |
- 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.
- There is no install target. You can run the program in place or copy it into the system path, like /usr/local/bin.
The software development is hosted at Source Forge.
https://sourceforge.net/projects/linuxptp/
Please report any bugs or other issues with the software to the linuxptp-users mailing list.
https://lists.sourceforge.net/lists/listinfo/linuxptp-users
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
As of yet there are no other open source applications making use of the new Linux APIs for PTP. However, patches are available for the ptpd program adapting it to the new calls. These patches do not really turn the ptpd into a perfect solution for hardware time stamping under Linux. Instead, they merely illustrate how the newer APIs work.
You can get the patches over at github. There are two branches, phc1 and phc2, for PTP versions 1 and 2, respectively.
- git://github.com/richardcochran/ptpd-phc.git
- https://github.com/richardcochran/ptpd-phc
Thanks to Intel Corporation for donating three NICs, the 82574, 82580, and the 82599.
For testing I use an OTMC 100 grandmaster clock donated by OMICRON Lab.