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Ethernet packets dropped



Hi,

I'm currently using Redboot on my own ARM/SA11x0 platform,
which is quite similar to Assabet/Neponset, including the
ethernet chip SMC-91C96. 

After writing the specific adapters between the generic 
LAN91CXX driver and the target platform, I notice that 
there are many dropped packets, even without pinging
the machine :

...
eth_drv_recv: packet of 263 bytes dropped
eth_drv_recv: packet of 263 bytes dropped
eth_drv_recv: packet of 95 bytes dropped
eth_drv_recv: packet of 95 bytes dropped
eth_drv_recv: packet of 94 bytes dropped
eth_drv_recv: packet of 95 bytes dropped
...

The default number of network buffers is 4, which is
enough for the original Assabet redboot that uses 
the LP-E CF ethernet adapter. Increasing the number
of buffers up to 32 (the maximum allowed) solves
the problem (16 buffers are not enough, though the
drop rate decreases).

This makes me wonder if :

1. Is this the correct tuning, or 4 packet buffers should
be enough and there is another problem hidden ?

2. Is the SMSC/LAN91CXX driver tested in any
platforms ? It seems that my platform-specific adapter
code can't cause this sort of problems.

The platform-specific code only does the following :

1. Set up the GPIO interrupt (falling-edge)
2. Shift the chip addresses by two bits, because in the
Neponset board the SMC A0 line is wired to the SA-1110's
A2 line (double-word alignment).
3. Set the chip base address.

Thank you

Jordi Colomer


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