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linuxptp/README.org

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* 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.
* Goals and 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).
- Modular design allowing painless addition of new transports and
clock servos.
* Getting the Code
The source code is managed using the git version control system. To
get your own copy of the project sources, use the following command.
#+BEGIN_EXAMPLE
git clone git://git.code.sf.net/p/linuxptp/code linuxptp
#+END_EXAMPLE
If the git protocol is blocked by your local area network, then you
can use the alternative HTTP protocol instead.
#+BEGIN_EXAMPLE
git clone http://git.code.sf.net/p/linuxptp/code linuxptp
#+END_EXAMPLE
* 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.
** Driver Support Matrix
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.
1. RAW: Supports time stamping using the PHC time values.
2. SW: Supports software time stamping using the system time.
3. 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.
*** Hardware Timestamping
|------------+-------------------------+------+-----+-----+---------|
| Driver | Hardware | SOTS | PHC | PHY | VER |
|------------+-------------------------+------+-----+-----+---------|
| bfin_mac | Analog Blackfin | SYS | N | NA | pre 3.0 |
| igb | Intel 82576, 82580 | SYS | N | NA | pre 3.0 |
| 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 |
|------------+-------------------------+------+-----+-----+---------|
*** Software Timestamping
|--------------+--------------------------+------+-----+-----+-----|
| Driver | Hardware | SOTS | PHC | PHY | VER |
|--------------+--------------------------+------+-----+-----+-----|
| davinci_emac | TI DaVinci, Sitara | SW | N | Y | 3.1 |
| dnet | Dave Ethernet MAC | SW | N | Y | 3.1 |
| 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 |
| 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 |
|--------------+--------------------------+------+-----+-----+-----|
* 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.
#+BEGIN_EXAMPLE
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
#+END_EXAMPLE
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 |
|---------------------------------+-----------------------------|
** 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. There is no install target. You can run the program in place or
copy it into the system path, like /usr/local/bin.
* 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
* Other PTP Applications
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
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