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Re: RFC: New bus_space routine: bus_space_sync
On Jan 19, 2012, at 11:28 AM, Manuel Bouyer wrote:
> On Thu, Jan 19, 2012 at 10:59:01AM -0800, Matt Thomas wrote:
>> For prefetchable regions (like framebuffers) mapped by bus_space_map, there
>> is a need to able force the contents out of the cache back into memory
>> (especially when the cache is a writeback cache).
>> There is no MI way to do this with the bus_space framework so I'm proposing
>> we add a:
>> void bus_space_sync(bus_space_tag_t bst,
>> bus_space_handle_t bsh,
>> bus_size_t offset,
>> bus_size_t length,
>> int ops);
>> where ops is one of:
>> #define BUS_SPACE_SYNC_WB 1 // defined by MD
>> #define BUS_SPACE_SYNC_WBINV 2 // defined by MD
>> One caveat is that though a BUS_SPACE_SYNC_WB was requested, a platform can
>> perform BUS_SPACE_SYNC_WBINV instead. If the platform can't support just
>> writeback, it is allowed to silently do a writeback-invalidate instead.
> Isn't this what bus_space_barrier(BUS_SPACE_BARRIER_SYNC) is for ?
No. bus_space_barrier controls memory (load/store) ordering and deals with a
completely diffeent problem.
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