[SeaBIOS] IDE DMA initialization

[Kevin O'Connor]

On Thu, Jan 14, 2010 at 10:48:33AM +0100, Magnus Christensson wrote:
> Hi,
> 
> The recently introduced DMA support in Seabios fails to work on
> Virtutech Simics. The reason is that DMA has not enabled in the
> disk. I'm trying to figure out if this is a bug in my setup of
> Simics, or a bug in Seabios. Shouldn't Seabios enable DMA in the
> disk through the SET FEATURES command?

My read of the spec was that the set_features command was only needed
to specify which dma mode was desired, and that the drive would
default into mwdma mode by default.  I'll take a closer look through
the spec this weekend.  The current code does seem to work with the
real drives I have.

In either case though, we probably should have a CONFIG_ATA_DMA
define to manually disable that support.

-Kevin