tree 702e9668705fcf96c0e1d6423a83f22d57e1c3fb
parent 7daa411b810d7eadfaabe3765ec5f827893dbb30
author Olof Johansson <olof@lixom.net> 1144896753 -0500
committer Paul Mackerras <paulus@samba.org> 1145622577 +1000

[PATCH] powerpc: Lower threshold for DART enablement to 1GB

Turn on the DART already at 1GB. This is needed because of crippled
devices in some systems, i.e. Airport Extreme cards, only supporting
30-bit DMA addresses.

Otherwise, users with between 1 and 2GB of memory will need to manually
enable it with iommu=force, and that's no good.

Some simple performance tests show that there's a slight impact of
enabling DART, but it's in the 1-3% range (kernel build with disk I/O
as well as over NFS).

iommu=off can still be used for those who don't want to deal with the
overhead (and don't need it for any devices).

Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>