PTP Clock Manager for Linux

Renesas Precision Time Protocol (PTP) Clock Manager for Linux (pcm4l) software supports IEEE 1588 and Synchronous Ethernet communication requirements to meet stringent ITU-T Network synchronization and time distribution. PTP Clock Manager is meant to complement an IEEE 1588-2008/2019 compliant PTP stack and features a clock servo and Packet Delay Variation (PDV) filter to meet the needs of ITU-T standard G.8273.4 and G.8263. While designed for use with the ClockMatrix™ synchronizers from Renesas, which support ITU-T standard G.8273.2 filtering in hardware, it can also be used with older generation devices. The PTP Clock Manager software is provided free of charge (under license) as long as it is paired with a clock synchronization device (such as the 8A34001) from Renesas.

In conjunction with this software, Renesas has developed and helps maintain a PTP kernel driver in mainline Linux, creating a proven solution for managing timestamps and establishing synchronization across the network. Renesas is actively working with TSU vendors to get the PTP kernel drivers included in their software distribution. We expect customers to have the PTP kernel drivers implemented and functioning properly prior to attempting to use the PTP Clock Manager software. For designs based on Xilinx MPSoC or RFSoC, Renesas can provide ZCU102/ZCU111 files based on Vivado/PetaLinux 2018.3 and ZCU102 files based on Vivado/PetaLinux 2020.1. If more hands on assistance is required, customers should engage with sales to discuss fees applicable for such support.

The primary source of the Renesas Clock Synthesizer driver set is from the Linux kernel. Our in-tree drivers can be found in the kernel source under drivers/ptp (for ptp_clockmatrix.c, ptp_clockmatrix.h, ptp_idt82p33.c and ptp_idt82p33.h) and drivers/mfd (for rsmu, rsmu_i2c and rsmu_spi). Since there is a delay to get the most recent version of the drivers accepted into the kernel and additional delay for individual distributions to align with the kernel, we also provide a site for customers to get the most recent (out of tree) version of the driver set at renesas/linux-ptp-driver-package (github.com). This site also provides the source for the rsmu drivers which provides additional interfaces used by pcm4l and user software to access the clock synthesizer.

For processing the ESMC (Ethernet Synchronization Messaging Channel) quality level messages and controlling the SyncE DPLL, Renesas provides the SynceD (Synchronous Ethernet Daemon) software. Please contact the Renesas team to get further help.

Combining the power of the kernel, PTP Clock Manager, and ClockMatrix™ devices, customers can easily deploy the Renesas solution with any vendor’s Time Stamp Unit (TSU) for their telecom and non-telecom applications. Many TSU vendors also offer kernel drivers in Linux, establishing a plug and play development environment.

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Demand for synchronization across the internet and throughout global communications networks is increasing. At the same time, the demand for tighter and tighter synchronization is growing, and networks are adapting to support these demands. Operators are also looking to reduce costs and spur innovation by migrating to O-RAN and White Box network solutions. As new vendors enter the fray, the call for open sourced SW to support the demands of IEEE1588 and Synchronous Ethernet networks is loud. Renesas offers a compelling solution with the first such software – the Precision Time Protocol (PTP) Clock Manager for Linux.

The Linux PTP stack and clocking devices like ClockMatrix™ now give users the ability to develop non-telecom solutions that are entirely open-sourced. Having a tested, proven solution for either Grand Master or slave clock generation establishes an easy launching point for developers that significantly reduces time-to-market to allow focus on innovative, differentiated, winning solutions.

What is PTP?

As noted above, PTP stands for Precision Time Protocol. PTP is used to synchronize the system elements of a network by means of a sophisticated clock synchronization scheme. PTP is a solution that can synchronize networks to a greater degree than is achievable with Network Timing Protocol (NTP), without leveraging access to the GPS system. Accessing GPS can be both challenging and costly. PTP is prevalent in systems that transmit packetized data which can sometimes lead to misstating PTP as Packet Timing Protocol.