> What I found was that even though this may have been the case, profiling
> revealed a slight advantage to using DMA_COHERENT mappings since the
> overhead of the bus_dma calls whittled away any advantage gained by the
> above.

Your analysis and explaination are helpful for my understanding, thanks.

KS8695 Ethernet is very simple, no frill.  My impression is Cirrus EP
Ethernet is a bit more complicated, at least for device driver programmers.
Kendin/Micrel designers are aware of how to make device driver simpler.
They are apparently conscious of descriptor bit assignment to avoid extra
bit manipulation for each transfer.  Having variable flag bits in lower order
makes instrunction count smaller since lower 16bit or less constants are
occationally more effecient for CPU instruction to handle  .

Toru Nishimura/ALKYL Technology, NetBSD values engineering talents.