Re: RFC: New bus_space routine: bus_space_sync

[Frank Zerangue <frank.zerangue%gmail.com@localhost>]

Matt,

Aren't frame buffers generally mapped using bus_space_map() with cache 
disabled? 

On Jan 19, 2012, at 12:59 PM, 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.

--
Frank Zerangue
frank.zerangue%gmail.com@localhost