This is just a heads-up that I encountered this problem on my VIA 82C* IDE-controller as well.
ide-generic/disk hijacked the ide-interfaces first and wouldn't let via82cxxx near them, and thus
no dma and a crawling system on large disk-operations.
Adding via82cxxx to /etc/mkinitramfs/modules so it was loaded first, fixed it for me as well.
Cheers.
