Re: RFC: New bus_space routine: bus_space_sync

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

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 ?

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--