• Olof Johansson's avatar
    [PATCH] powerpc: Lower threshold for DART enablement to 1GB · 28897731
    Olof Johansson authored
    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: default avatarOlof Johansson <olof@lixom.net>
    Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
    28897731
dart_iommu.c 9.24 KB