[PATCH] [RFC] ppc32 (linux-2.6.11.4): remove the limitation of 2MB consistent DMA memory on ppc440

[Shawn Jin]

Hi,

This patch removes the limitation of 2MB consistent DMA memory on
ppc440. Originally consistent_pte was allocated only one page no
matter what value of CONFIG_CONSISTENT_SIZE is set. By default
CONFIG_CONSISTENT_SIZE is 0x200000. This causes some troubles on high
performance I/O applications which may require more than 2MB
consistent DMA memory.

The modifications allocate multiple pages for consistent pte table
according to CONFIG_CONSISTENT_SIZE. For example if
CONFIG_CONSISTENT_SIZE is set to 4MB, 2 pages are allocated for
consistent pte table. Please note that CONFIG_CONSISTENT_SIZE cannot
be any value. You have to find a free continuous memory space on your
system memory mapping.

The patch was tested successfully on Ocotea board. But I'm not sure if
it works on other systems. Use it at your own risk. However feedback
is more than welcome. :)

Regards,
-Shawn.
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