RE: Power PC 440GX Jumbo Packets EMAC2/3

On Thursday 24 February 2005 12:46, zDL Linux PPC wrote:

quoted

I have been doing some experiments with Jumbo packets (MTU 

9000) and have

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noticed that once you exceed the 2KB fifo size, I end up 

with no response

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from the box.

I can ping the box with no problem at all at sizes greater 

than 2KB, however

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upon further investigation I noticed packets of size 2006 

bytes causes no

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further packet to be transmitted (adding debug prints to 

ibm_emac_core.c,

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the driver believes the packet has been transmitted), after 

adding a further

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42 bytes of header information this comes to the exact size 

of the Transmit

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Fifo 2048 (2KB). I have also changed the Transmit Fifo 

Register to 1024

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bytes, this solves the problem at 2006 bytes however now it 

has moved to 982

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bytes of data (+42bytes of header = 1024)

Has anyone else experienced this problem while either using 

a smaller

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transmit fifo (512 or 1024 bytes) and  MTU 1500 or a larger 

MTU (>2033) and

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EMAC transmit fifo of 2048. I guess this will really apply 

to people with

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larger MTU not many will decrease the Tx fifo, and I am 

further guessing

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that not many are using 9000 MTU as not much hardware seems 

to support it, I

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can only use it through a direct connection between PC's 

and not through a

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switch!

Any suggestions on how to overcome this problem??? My only 

idea is to either

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add data to the packet (don't think this will work) or 

forceably fragment

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the packet (if it is 2K in size) to ensure that it never 

uses the exact size

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of the tx fifo.....

Have you applied Matt Porters patch? It has been submitted at 
the beginning
of this month?

No I haven't seen it on either of these lists, do you know where I can find
it 

Thanks

On Thursday 24 February 2005 14:12, zDL Linux PPC wrote:
[SNIPSNAP]

quoted

quoted

Any suggestions on how to overcome this problem??? My only 

idea is to either

quoted

add data to the packet (don't think this will work) or 

forceably fragment

quoted

the packet (if it is 2K in size) to ensure that it never 

uses the exact size

quoted

of the tx fifo.....

Have you applied Matt Porters patch? It has been submitted at 
the beginning
of this month?

No I haven't seen it on either of these lists, do you know where I can find
it 

Thanks

Browse the linuxpp-embedded archive list, I think it was around the 9th
of february...
or try this one
http://ozlabs.org/pipermail/linuxppc-embedded/2005-February/001260.html

Gerhard

-- 
Gerhard Jaeger [off-list ref]            
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