Scott Wood [off-list ref] wrote on 30/03/2009 19:45:17:

Joakim Tjernlund wrote:

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Scott Wood [off-list ref] wrote on 30/03/2009 19:22:03:

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Joakim Tjernlund wrote:

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gianfar does not seem to use in_/out_ functions for the BDs. Works 

just

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fine that too it seems.

It does now that it has explicit barriers in a few places.  Before 

they

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In 2.6.29 or later?

No, it was earlier.

Ah, I see now. The eieio() stuff.

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were added, it would sometimes fail under load.  That was due to a 
compiler reordering, but CPU reordering was possible as well.

Does not the CPU skip reordering if the guarded bit is set?

The guarded bit is typically not set for DMA buffers.  ucc_geth is a bit 

different since descriptors are in MURAM which is ioremap()ed -- though 
switching to a cacheable mapping with barriers should be a performance 
improvement.

I always thought that MURAM was very fast. The whole reason to have BDs in
MURAM is that it is faster than normal RAM, at least that is what I 
thought.

 Jocke