RapidIO Connections Newsletter - Summer 2005

Executive Director’s Perspective Transitions: RapidIO® technology forms the critical foundation for new and emerging applications in the midst of a world of change.
Design It Fault-Tolerant Systems and RapidIOŽ
Insights What are some of the benefits to having an open standard?
Member Connections • Debugging/Analyzing Serial Rapid IO High-Speed Serial Lanes by Chris Shelsky, Project Manager, Nexus Technology, Inc.

• RapidIO and Linux by Matt Porter of MontaVista Software, Inc.
RapidIO Product News New RapidIO-based solutions continue to debut in multiple market segments from silicon to board-level products.
The RapidIO Trade Association at Work Munich and Boston Developer Summits, Freescale Technology Forum, Supercomm
In the Spotlight The RapidIO Trade Association and standard continue to be sought after news in the industry.
Where to Network Visit with RapidIO Trade Association members, learn about products and see live demonstrations.
RapidIO Hall of Fame "Did You Know?" email campaign a success!
Changes Some parting thoughts from Dan Bouvier as he steps down from the RapidIO Steering Committee.
RapidIO Reflections: Significant interest in RapidIO technology from a wide cross section of customers

Member Connections:

RapidIO® Technology and Linux by Matt Porter of MontaVista Software, Inc.

RapidIO® technology has come of age yet its support for Linux has only been available for a short time. Even so, many silicon vendors are already planning to use Linux to validate their new parts, thus ensuring early support for Linux on emerging silicon. The combination of standards based RapidIO devices with Open Source Linux provides an ideal platform for new designs.

Background

RapidIO technology has come of age. It has reached critical mass with numerous vendors announcing or shipping Serial RapidIO devices. Parallel RapidIO devices have now been available for more than a year, and vendors have stepped up to produce off the shelf systems incorporating these devices.

Like many member companies, MontaVista Software has been very involved with the RapidIO standardization process for several years. MontaVista's strong supports for Carrier Grade Linux (CGL) solutions are a good match with the emergence of RapidIO as a solid telecom and communications technology. As silicon and OEM vendors committed to support RapidIO, MontaVista joined with a determination to enable RapidIO on Linux.

Project

In late 2004, MontaVista Engineering approved a project proposal to design and implement Linux kernel support for RapidIO. In the process of development, the engineers running the Linux RapidIO project set a series of specific requirements, such as:

  • Work openly within the Linux community>
  • Create a code base that is acceptable for the mainline kernel
  • Target the 2.6 kernel
  • Provide an abstraction of RapidIO facilities to encapsulate future silicon
  • Provide a standard Linux network driver for Ethernet encapsulation in RapidIO messages

The project reached a major milestone when the initial requirements were met, and a full code release was submitted to the Linux kernel community. After incorporating comments from community members, the release was accepted into the -mm staging tree. RapidIO support is now expected to merge into the mainline Linux kernel for the 2.6.13 release.

Subsystem

The Linux RapidIO subsystem provides support for:

  • Enumeration and discovery of devices
  • Device driver interface
  • Abstraction layer for hardware specific portions of endpoints and switches
  • Integration with the Linux Device Model

Enumeration and discovery is supported with a complete implementation of the recommended algorithm documented in Annex I of the RapidIO Interconnect Specification. Enumeration is performed by a single winning host, while all other endpoints perform passive discovery to catalog devices in the system.

The device driver interface is defined to abstract all access to hardware that is required by a RapidIO device driver. Driver interfaces manage access to mailboxes, doorbells and transmission/reception of messages. An abstraction layer for endpoints and switches exists to separate common functionality from hardware specific operations. Such specific operations include switch specific routing table access and management of mailbox and doorbell queues.

Finally, all of this support is integrated into the standard Linux Device Model (LDM). The LDM provides a standard interface to register devices and drivers with the kernel. Once all devices have been discovered by the RapidIO subsystem, they are registered as RapidIO devices with the LDM. A RapidIO driver then provides a table with vendor/device info specifying devices it should claim, and registered devices are then matched with the appropriate driver via the vendor/device info.

Network Driver

RapidIO messaging uses transmission and receiving queues for data packets, which are similar to the mechanisms found on common network controllers. This similarity in operation makes it convenient to realize messaging in a standard Linux network driver. By carrying Ethernet frames in RapidIO messages, Linux provides a standard network interface to user applications. This approach opens up a wealth of applications, which communicate via TCP/IP. Users are immediately able to validate the interconnect using familiar tools like ping, telnet and FTP. Any protocol carried over TCP/IP can be leveraged immediately and complex routing configurations can be utilized

Future

The future is very bright for Linux and RapidIO. Work is progressing on expanding and improving the RapidIO support in many ways. Support for Memory Mapped I/O regions and a Port Write event is currently in development. As new RapidIO silicon is produced, Linux will also be enhanced to support these devices.

RapidIO support for Linux has only been available for a short time, however increasing interest from OEMs and silicon vendors has been very encouraging. Silicon vendors are already planning to use Linux to validate their new parts, thus ensuring early support for Linux on emerging silicon. The combination of standards based RapidIO devices with Open Source Linux provides an ideal platform for new designs—opening new opportunities. For more information, visit MontaVista’s web site at http://www.mvista.com/

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