Can't enable DMA when using IDE devices on SATA controllers

[Marcelo Magno T. Sales]

Hi,

I have several IBM desktops and some notebooks in which the IDE interface is a 
SATA controller, most of them Intel. Here's lspci output:
-------------
[marcelo.sales at sf002698 ~]$ /sbin/lspci | grep IDE
00:1f.2 IDE interface: Intel Corporation 82801FB/FW (ICH6/ICH6W) SATA 
Controller (rev 03)
-------------
On these machines, I can't enable DMA on IDE devices. hdparm shows:
-------------
[marcelo.sales at sf002698 ~]$ /sbin/hdparm /dev/hdc
/dev/hdc:
 IO_support   =  0 (default 16-bit)
 unmaskirq    =  0 (off)
 using_dma    =  0 (off)
 keepsettings =  0 (off)
 readonly     =  0 (off)
 readahead    = 256 (on)
 HDIO_GETGEO failed: Inappropriate ioctl for device
-------------
When I try to enable DMA, I get:
-------------
[marcelo.sales at sf002698 ~]$ su -c '/sbin/hdparm -d1 /dev/hdc'
/dev/hdc:
 setting using_dma to 1 (on)
 HDIO_SET_DMA failed: Operation not permitted
 using_dma    =  0 (off)
-------------
I thought this was caused by lack of kernel support for the SATA controller, 
but I've compiled the FC kernel and the vanilla kernel several times, with 
different settings, and have got no luck on this. libata is built and loaded, 
as shown by lsmod:
[marcelo.sales at sf002698 ~]$ /sbin/lsmod | grep libata
libata                 58065  1 ata_piix
scsi_mod              129001  3 sg,libata,sd_mod

What needs to be done to enable DMA support? I'm using kernel 
2.6.16-1.2122_FC5smp.

Thanks,

Marcelo