MFC r269206, r269207, r269208, r269209, r269210, r269211, r269212, r269213,
r269214, r269215, r269216, r269217, r269221:
busdma-v6 improvements, primarily:
- Allocate the temporary segments array per-map rather than per-tag.
- Avoid needlessly bouncing IO for mbufs and buffers allocated by
bus_dmamem_alloc() (in both situations we known they're allocated
on cacheline boundaries and don't need bouncing).
- Various minor reformatting and cleanups.
git-svn-id: svn://svn.freebsd.org/base/stable/10@269794
ccf9f872-aa2e-dd11-9fc8-
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