In the old days, device drivers passed NULL for the parent tag when creating
a new tag, and on arm platforms that resulted in a global tag representing
overall platform constraints being substituted in the busdma code. Now all
drivers use bus_get_dma_tag() and if there is a need to represent overall
platform constraints they will be inherited from a tag supplied by nexus or
some bus driver in the hierarchy.
The only arm platforms still relying on the old global-tag scheme were some
xscale boards with special PCI-bus constraints. This change provides those
constraints through a tag supplied by the xscale PCI bus driver, and
eliminates the few remaining references to the old global var.
Reviewed by: cognet
- Add a default parent dma tag, similar to what has been done for sparc64.
- Before invalidating the dcache in POSTREAD, save the bits which are in the
same cachelines than our buffers, but not part of it, and restore them after
the invalidation.
sys/bus_dma.h instead of being copied in every single arch. This slightly
reorders a flag that was specific to AXP and thus changes the ABI there.
The interface still relies on bus_space definitions found in <machine/bus.h>
so it cannot be included on its own yet, but that will be fixed at a later
date. Add an MD <machine/bus_dma.h> for ever arch for consistency and to
allow for future MD augmentation of the API. sparc64 makes heavy use of
this right now due to its different bus_dma implemenation.
