• Introduction
• License
• Features
• Getting the Code
• System Requirements
  • Linux Kernel Support
  • Ethtool Support
  • Driver Support Matrix
    • Hardware Timestamping - PHY
    • Hardware Timestamping - MAC
    • Software Timestamping
• Installation
  • Linux kernel
  • PTP stack
• Getting Involved
  • Reporting Bugs
  • Development
• 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 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.

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, 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).

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.

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.

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.

Hardware Timestamping - PHY

Driver	Hardware	Version
dp83640	National Semiconductor PHYTER	3.0

Hardware Timestamping - MAC

Driver	Hardware	Version
bfin_mac	Analog Blackfin	3.8
cpts	Texas Instruments am335x	3.8
e1000e	Intel 82574, 82583	3.9
fec	Freescale i.mx6	3.8
gianfar	Freescale eTSEC PowerPC	3.0
igb	Intel 82576, 82580	3.5
ixgbe	Intel 82599	3.5
ptp_ixp46x	Intel IXP465	3.0
ptp_phc	Lapis EG20T PCH	3.5
sfc	Solarflare SFC9000	3.7

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
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
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
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

Installation

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 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_PPS	Required
CONFIG_NETWORK_PHY_TIMESTAMPING	Timestamping in PHY devices
PTP_1588_CLOCK	PTP clock support

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.

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.

https://lists.sourceforge.net/lists/listinfo/linuxptp-users

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

Thanks

Thanks to AudioScience Inc for sponsoring the 8021.AS support.

• http://www.audioscience.com

Thanks to Intel Corporation for donating four NICs, the 82574, 82580, 82599, and the i210.

• http://www.intel.com
• http://e1000.sourceforge.net

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

• http://www.omicron-lab.com/ptp