[U-Boot] Using Uboot to communicate a PCI device.

[dwh at ovro.caltech.edu]

Hi Darshan,

Let me summarize your hardware and request:
 - Cavium Octeon host-processor
 - Wintegra Winpath Network slave processors
 - Devices connected via the PCI bus
 - You want to create a U-Boot application to boot the
   processors and then communicate over the PCI bus.

However, before we discuss U-Boot coding, it would be
useful if you could provide a more detailed system-level
description, so that we can provide suggestions.
For example;

 - I assume the Cavium processor boots U-Boot, and performs
   some initialization of the NPs, and then boots its OS.
   What is the OS?

   Does the Cavium instance of U-Boot have to boot the NPs?
   Can the Cavium processor U-Boot initialize the PCI
   interfaces on the NPs and then boot its OS, and then
   the Cavium OS can boot the NPs.

   U-Boot is a bootloader. More complex features/control
   may be easier to deal with inside a complete OS such as
   Linux.

 - What OS will the NPs be running? Is there any need for
   the NPs to run U-Boot? Can the NPs have their OS image
   copied into their local memory, and then the processors
   boot directly into their OS - no bootloader necessary?
   Can the Cavium processor perform all device initialization
   that U-Boot running on an NP would normally perform?

 - Does the NP need to communicate with the Cavium via
   the PCI bus, or would it be just as efficient for
   them to communicate over the network?

   Ira Snyder has worked on a PCI-to-PCI network driver
   that might work for your processors, however, I'd
   need to look at the datasheets for the Cavium and
   NPs to see if they have the right features for this
   type of interface.

Try and get the system-level design described first, and
then the software requirements for the lower-levels will
become clearer, or others will suggest solutions that you
may not have considered.

Cheers,
Dave