> On Mon, 04 Dec 2000, Leo Smiers wrote:
> > Hello
> >
> > Could anyone inform me about the current status of the dma support for the
> > RISC PC? Is there any documentation (beside the man pages) about how to
> > make use of dma on the RISC PC, preferably with some examples.
> 
> I beleive is none, I think we do allocate the DMQ's though.
> 
> I believe it's something that no-one has got around to doing.  That and 
> finding technical docs about the RPC is hard.
> 
> Anyone considering doing DMA may also need to now consider that the kinetic 
> can't to DMA from it's ram, so it can only be done from motherboard ram.
> 
> Chris

I've been intending to work on a generic IOMD dma system for a while; it's 
needed to replace some of the awful hacks that are in my current sound 
driver implementation (soo bad I'm embarrassed by it ;-).

I think I have all the information needed in the RPC's TRM combined with a 
few more hints from the RISC OS PRMs.  Using the bus_dma model it should 
be relatively straight-forward to set up a suitable scatter-gather based 
dma system for IOMD and to also handle kinetic requirements (though that 
may need some pmap hackery).  Can you give me a couple of evenings to try 
and put together a spec (it should be along the lines of the isa_dma 
interface); then I'll post it here for comments.

R.