ep93xx SPI driver v3

[Mika Westerberg]

On Sat, Apr 17, 2010 at 04:23:53AM +0100, Martin Guy wrote:
> Yes, ep93xx DMA engine has two flavours: memory-to-peripheral, used
> for most devices, and memory-to-memory, used for block memcpy and for
> memory-to-SSP/SPI (== SD card).
>
> The easiest route would seem to be to get the M2M stuff working to do
> memcpy fast. Can linux make use of that? I haven't yet seen anything
> that can make use of a memory-to-memory copy DMA engine.

I think that the M2M engine can also perform M2P transfers for
SSPRX, SSPTX, and IDE in addition to memory-to-memory transfers.

There already is dma-m2p support and I guess that it can be extended
to support M2M controller for IDE and SPI.

> If we can get that working, a reasonable second stage would make it
> work for ep93xx-SPI transfers, making SD card access even less
> CPU-intensive

Yes.

MW