busdma problem

[Mark Tinguely]

>  On Fri, Jan 30, 2009 at 02:07:14PM -0800, Andrew Thompson wrote:
>  > On Fri, Jan 30, 2009 at 09:31:47AM -0800, Andrew Thompson wrote:
>  > > >> I am having an issue with busdma when bounce buffers are used. I have
>  > > >> patched _bus_dmamap_sync_bp() to print out the details when a bounce
>  > > >> happens and also print the driver buffer before and after.
>  > > >> 
>  > > >> During normal dma everything is fine,

	[Deleted items]

>  > As suggested by Sam, this works properly when the buffer is malloc'd
>  > instead of taken from the stack. So is this now a bug or a feature??
>
>  As a test I removed the checking of KENTER_CACHE in
>  arm/arm/pmap.c:pmap_kenter_internal() so all memory is uncached and now
>  dma bounces to a stack variable work.
>
>  busdma remaps the address nocache into vaddr_nocache pointer and uses
>  that for the bcopy, obviously arm_remap_nocache() is not working
>  correctly.
>
>  Andrew

I suspected this was another occurrance of the same cache problem that
has been mentioned starting about 3 weeks ago. I even was going to ask
you if it was using arm_remap_nocache().

I have a new concept patch for the kernel caching issue at:

	http://www.casselton.net/~tinguely/arm_pmap_unmanaged.diff

I am still waiting for a drive to build a -current machine. I will also
look at any other caching ideas that others have.

--Mark Tinguely.