Re: [ECOS] Fwd: Packet size limit on TCP/IP stack ?

["mohanlal jangir" <mohanlaljangir at hotmail dot com>]

> A few things to try. For the moment i'm assuming the software is OK
> and its a hardware/configuration problem. Check to see if there are
> any runt packets on the network. The i82559 does a TX by first
> prefilling the TX fifo with part of the packet. It then starts the TX
> using what it has already in the fifo and getting the rest of the
> packet from memory as quick as it can.
After having a deep eye on document 8255X_OpenSDM.pdf and fiddling with
82559 driver source code, conclusion is that you are absolutely right :-). I
found that on every packet (of length more than 160) transmission, the
counter tx_underrun is incremened by one. My all five packets of length more
than 160 are becoming runt . But I don't know why counter tx_good always
shows 0xFFFFFFFF although five packets (of length equal to 160) are reaching
to other end.

> I've had a problem with a
> broken PCI arbiter which resulted in the transfer from main memory
> being too slow and the i82559 sent all it had in its fifo while the
> rest of the packet was still being DMAed from main memory. The i82559
> then has to abort the packet.
Seems I am also having same problem. So how do I go now? Do I need to look
in PCI arbiter settings?

> There is a register that controls how
> much it should prefill the fifo with. Try increasing the prefill.
In 8255X_OpenSDM.pdf, I could not figure out about prefill. It is talking
about some pre-amble but not prefill (Is it some standard word?). The
pre-amble lengh is set to 7(decimal) and could be max 10. I did try to
change to 10 but that is having no effect. So I am assuming this is
different from prefill, you are talking about. I am still looking in
document to find which register controls prefill value. Any clue?

Regards
Mohanlal

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