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Method for RapidIO System Discovery

IP.com Disclosure Number: IPCOM000131948D
Publication Date: 2005-Nov-22
Document File: 2 page(s) / 36K

Publishing Venue

The IP.com Prior Art Database

Related People

Jeffrey A. Wilcox: AUTHOR [+2]

Abstract

In a RapidIO fabric, it is possible that the RapidIO host or hosts responsible for system discovery, and the boot ROM from which the host CPUs performing discovery fetch their instructions may be located in different RapidIO endpoints. This leads to the requirement that during RapidIO system discovery, all switches incorporated in the fabric must be able to route the read requests issued to fetch these instructions to the endpoint wherein the boot ROM resides. Likewise, response packets from that endpoint must be routed back to the requestor. While the RapidIO specification provides a mechanism for routing the request, no such mechanism is provided for returning the response.

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Method for RapidIO System Discovery

Jeffrey A. Wilcox, Ron L. Swartzentruber

Abstract

In a RapidIO fabric, it is possible that the RapidIO host or hosts responsible for system discovery, and the boot ROM from which the host CPUs performing discovery fetch their instructions may be located in different RapidIO endpoints.  This leads to the requirement that during RapidIO system discovery, all switches incorporated in the fabric must be able to route the read requests issued to fetch these instructions to the endpoint wherein the boot ROM resides.  Likewise, response packets from that endpoint must be routed back to the requestor.  While the RapidIO specification provides a mechanism for routing the request, no such mechanism is provided for returning the response.

The present invention provides a mechanism which allows the switch to record the port by which the requests arrived, thereby allowing the response to be returned to the same port.  This recording mechanism remains in operation so long as the switch’s routing table is not programmed, acting as a Device ID specific default routing option during the discovery period.

Problem

RapidIO defines a discovery process that allows for one or two Endpoints to perform system disc overy.  This process is intended to determine the structure of the overall fabric, assign deviceIDs to each endpoint in the fabric and program the routing tables in each switch in the fabric.  Prior to the discovery process, the following rules are defined for the fabric:

1)       The endpoint containing the primary host shall have a deviceID of 0x00.

2)       If there is an endpoint containing a secondary host, it shall have a deviceID of 0x01.

3)       An endpoint containing the boot ROM shall have a device ID of 0xFE.

4)       All other endpoints shall have a deviceID of 0xFF.

5)       Any switch in the fabric shall know which of its ports leads to the endpoint with the boot ROM, and shall route all traffic with a Destination ID of 0xFE to that port.

6)       Any switch in the fabric shall route otherwise un-routable packets to its lowest numbered port.

A simple fabric in such initial state is depicted in the following diagram.  Note that in this diagram, the default for un-routable packets would result in their being delivered to the boot

ROM.

Figure 1 Simple RapidIO Fabric

Consider the initial instruction fetches of the two host devices in such a fabric.  The host at deviceID 0x00 issues an NREAD targeting deviceID 0xFE.  This arrives at the switch on port1, and is delivered to the boot ROM device via port 0.  The boot ROM device sends a RESPONSE packet with the requested instructions targeting deviceID 0x00, which arrives at the switch on port 0.  However, as the routing table in the switch is yet to be programmed, this response packet is routed to the default port, which is port 0, thereby returning the response to the boot

ROM.

  Any request originating from the Host at deviceID 0x01 will suffer the same problem.  From this, it should...