Subject: MPC5200B panics with high ethernet rx traffic

From: "Asier Llano Palacios" <[email-masked]>
Date: Wed, 14 Oct 2009 18:35:54 +0200

Hi,

I've found a very simple way to create a kernel panic, that's happening
to our MPC5200B based boards. The issue was that when our boards
received a burst of ethernet packets had a kernel panic.

It does also happen to a lite5200b evaluation board, and it is really
simple to reproduce:
 Step 1: Configure the jumpers of the board as:
    CFG 4: L
    CFG 3: L
    CFG 2: H
    CFG 1: L
    CFG 0: L
    --------
    XLB:   L
    SYS:   L
    FVCO:  L
    MG:    L
    LF:    L
    HI/LO: L (but it depends on where do you have the bootloader)
    WAIT:  H
    SWAP:  L
    WIDE:  L
    MUXED: L
 Step 2: Connect an ethernet cable from the board to a 100Mbit
         ethernet switch.
 Step 3: Make a loop in the switch connecting two other ports together
         (I know this is weird but it is the simplest way I know
          to generate an intensive traffic).
 Step 4: Power up the board
 Step 5: ifconfig 192.168.0.1
 Step 6: ping 192.168.0.123

The ping generates an ARP packet (which is broadcast), then with the
loop of the switch the board will receive a storm of ARP packets
(probably near 100Mbits). Then the board configured with 266MHz core
will panic.

It happens to me in Linux versions from 2.6.22 to 2.6.28, with
bootloaders from 1.1.6 to 2009.08. It doesn't happen if you change the
jumpers (CFG 3: H, CFG 1: H) increasing the Core frequency. I'm planning
to test it with 2.6.31 but I still have another issues to test this.

I provide a log with the kernel panic.

We could assume that the CPU usage goes really high. We could also
assume that the packets that cannot be processed are dropped. We cannot
assume a kernel panic because during one second the reception traffic in
the ethernet was too high.

If you want more information or want us to perform more testing I would
gladly try to help. Maybe you can test it with your versions of software
and your board.

Your help would be greatly appreciated,
Asier 
 
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