interference between scc serial and ethernet: more information

interference between scc serial and ethernet: more information

[Brown, David (dbrown03)]

The target is a custom board similar to the EST8XX configuration, with an
860 and an LXT908 PHY.  I ultimately need to run PPP on SCC3.  When ethernet
receives data, it messes up SCC3's configuration somehow.  I briefly tested
with SCC2 and saw the same thing, but I have concentrated on SCC3.

It's a 50MHz MPC860, identified by 8xxrom as XPC860xxZPnnC1 and actually
stamped as XPC860ENCZP50C1.  Running at 50MHz.

Three nodes on the ethernet: the target, the Abatron BDI2000, and the
development host.

Case 1) Linux boots with default parameters, no IP address.  I use SCC3
serial, no problem.  Then, on the development host, I ping a non-existent
address (causing an ARP request broadcast).  After that, the SCC3 serial is
not working.  Sometimes, when I write to SCC3, garbled characters come out
(like it's the wrong baud rate).  Other times, nothing comes out at all.

Case 2) Linux boots with IP address parameters.  I use SCC3 serial, no
problem.  Then, on the target, I ping a non-existent address.  Serial still
works fine.  I get "neighbour table overflow" messages.

Case 3) In enet.c, in cpm_enet_rx(), I commented out code so that all
received frames get tossed.  Again, SCC3 serial stops working when the
development host pings an unknown address.

I tried activating kgdb to debug this, but kgdb stops working as soon as the
init shell starts.  It seems to be a fight over which process gets the input
data.  I'm looking at it with BDM, but that's quite slow since I have to
translate memory references.

I see four potential possibilities.
a) A bug in the enet or serial driver.  Not likely, since others report that
Ethernet and SCC serial ports work simultaneously for them.
b) A hardware problem on my board.  My co-worker says that's unlikely, since
his low-level test software exercises Ethernet RX and uses SCC3 as the
console.
c) A blatant configuration error in my setup of Linux.  Not likely, since
Ethernet and Serial each work independently.
d) My board violates some assumptions made by Linux and/or the drivers.
That seems to me to be the most probable, but I can't think of what it might
be.

Please feel free to throw out random ideas as to what I should look for.

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Re: interference between scc serial and ethernet: more information

[Dan Malek]

"Brown, David (dbrown03)" wrote:

> It's a 50MHz MPC860, identified by 8xxrom as XPC860xxZPnnC1 and actually
> stamped as XPC860ENCZP50C1.  Running at 50MHz.

There shouldn't be any trouble with that part.

Since this is a custom board, what software changes have you made?
What board configuration file are you using?  What changes did
you make to commproc.h to support your Ethernet configuration?

Send me all of your changes (i.e. diff the sources), or post them
or something.  This kernel on something like the Embedded Planet CLLF
runs just fine with Ethernet and PPP on multiple serial ports.  Show
the changes and maybe we can help.  I certainly can't guess any more.


	-- Dan

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