No DMA on IDE Harddisk

[nyk]

I just successfully installed gentoo on my new AMD64 system. The only problem is, I can't activate DMA transfer mode for the IDE harddisk. I tried to activate it at kernel menuconfig or with hdparm, but it doesn't work.

I guess it has something to do with using a generic IDE driver, instead of the correct one for my IDE chip.
The PC has a Gigabyte K8VNXP AMD64 board with the Via 8237 South Bridge chipset.

How can I find the correct driver for this chipset and compile it into the kernel, so the DMA will work?

I use gentoo-dev-sources 2.6.7-gentoo-r14 kernel.

Here some info about the harddisk:
# hdparm -i /dev/hda
/dev/hda:
Model=Maxtor 6Y120P0, FwRev=YAR41BW0, SerialNo=Y44SWERE
Config={ Fixed }
RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=57
BuffType=DualPortCache, BuffSize=7936kB, MaxMultSect=16, MultSect=off
CurCHS=4047/16/255, CurSects=16511760, LBA=yes, LBAsects=240121728
IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
PIO modes: pio0 pio1 pio2 pio3 pio4
DMA modes: mdma0 mdma1 mdma2
UDMA modes: udma0 udma1 udma2 udma3 udma4 udma5 *udma6
AdvancedPM=yes: disabled (255) WriteCache=enabled
Drive conforms to: (null):
* signifies the current active mode

Here is the the output from startup, where it activates the HDD:
Uniform Multi-Platform E-IDE driver Revision: 7.00alpha2
ide: Assuming 33MHz system bus speed for PIO modes; override with idebus=xx
VP_IDE: IDE controller at PCI slot 0000:00:0f.0
VP_IDE: chipset revision 6
VP_IDE: not 100% native mode: will probe irqs later
VP_IDE: VIA vt8237 (rev 00) IDE UDMA133 controller on pci0000:00:0f.0
ide0: BM-DMA at 0xd400-0xd407, BIOS settings: hda:DMA, hdb:pio
ide1: BM-DMA at 0xd408-0xd40f, BIOS settings: hdc:DMA, hdd:pio
hda: Maxtor 6Y120P0, ATA DISK drive

The Problem:
# hdparm /dev/hda
using_dma = 0 (off)[/b]

[nyk]

Ok, found the answer myself, via google in another forum.
Here: http://forums.viaarena.com/messageview.cfm?catid=20&threadid=48737&STARTPAGE=1

In short, I think the important thing is to turn off the SCSI SATA drivers in kernel config while leaving on the VIA82CXX driver and Auto-DMA. Now that the SATA driver is not interfering (in a way I don't understand) with the IDE DMA, it suddently works!