All,
I would like to put an end to the rumors and questions about the network
hangups.
Martin: There is a known issue with the Cavium CPU, this bug causes link to
drop and re-establish. Unfortunately Cavium has no idea why our hardware does
not work, and has provided us with numerous kernel tweaks (all of which poke
magical undocumented registers that they will not tell us about) that either
have no effect or adverse side effects. At best, we have attributed this to a
combination of their driver, the magic register values not being "tuned" to our
hardware, as well as our hardware layout. Since this bug was first discovered
we have made a few hardware tweaks specifically that have made the problem
better, but it has not fully gone away. Unfortunately, this bug appears to be
very random, some boards always get link and keep it, others will constantly
lose link at 10m cable, but be perfect at 100m. We do our best to not ship
boards that show this issue, but the randomness of this makes it hard to track.
The big saving grace is that ethernet will usually re-establish link quickly.
As soon as we have a good working solution from Cavium we will be doing an
update on this matter. As Drew said, see this errata:
http://www.embeddedarm.com/about/resource.php?item=420#workaround03
I also want to clarify that the SBUS has _NO_ impact on this bug. All SBUS
related processes can be stopped and this will still occur.
Tom: You are correct, the TS-7370 (and all devices that share that same sdcard
driver codebase, includes TS-7260 running linux 2.6) has a small bug that the
kernel stalls while waiting for the SD card to be done being busy. It is
unfortunate, but due to legacy reasons it will likely stay where it is as we
have a few large customers using the TS-73x0 boards. As you said we have
gotten NBD working with that driver and that will correct that issue. The bug
that Martin is seeing on his TS-75xx boards are not related to SD or the SBUS
as these remain in userspace. The ethenet issue as we know it is mostly a
hardware issue with the Cavium MAC+PHY.
-Kris Bahnsen
Technologic Systems
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