On Wed, Apr 16, 2014 at 06:48:43PM +0200, Gerd Hoffmann wrote:
That said, CONFIG_ATA_DMA is very fragile and it may be worth just removing at some point.
Why is it fragile?
On PATA you're supposed to do all these weird controller specific stuff to make sure DMA works, to set what level of DMA to use, and to tell the drive that DMA will be used. The SeaBIOS code does none of that. This is why CONFIG_ATA_DMA is disabled by default.
Now that I think about it though, the code is likely okay for SATA drives attached to SATA controllers that use ATA emulation.