Some ia64 platforms may not support write combining on all type of memory,

    so we need to consult the EFI memory map before we try to set the write
    combine attribute of a page. This patch will try to map a page write
    combined if it's not an AGP page and the EFI memory map says it's ok,
    otherwise it falls back to a regular, uncached mapping. Can someone
    please apply this to the drm tree?
From: Jesse Barnes