PPC64 & DMA zone

Hi,

Is there a way to reduce/limit DMA zone with PPC64 kernel (3.6-rcX)
on G5 Mac? I have tried to search Kconfig or command line options,
but can't find anything.

The problem I have is that b43 driver (wireless chip) insists a 30-bit
DMA mask, but I have 1.5 GB physical memory. So the only way I can get
the wireless connection to work is to boot with "mem=1024MB". And as a
result my bloaty applications will loose much needed memory...

Thanks,

A.