On 01/14/2010 02:48 PM, Kevin O'Connor wrote:
On Thu, Jan 14, 2010 at 10:48:33AM +0100, Magnus
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.
The spec does suggest that mwdma mode is default after power-up. I'll
change Simics' device model.
In either case though, we probably should have a
define to manually disable that support.
Good. CONFIG_ATA_DMA does work now with Simics, and we'll keep it on
since it provides a significant performance improvement (rep
i/o-operations are not handled very efficiently in Simics).