Comment 62 for bug 110636

I've experienced as well this dma problem under ubuntu hardy, with kernel 2.6.24.x series. The second fix suggested by C. Cooke worked like a charm on my system. I've added "combined_mode=libata" option to /boot/grub/menu.lst file and ran update-grub to permanently boot the system with this option on.

In particular:
    * Recommended (where BIOS permits): Change BIOS IDE mode from "legacy" or "combined" mode to "AHCI" (recommended), "RAID" or "native". (UNAPPLICABLE)
    * Boot with the kernel commandline parameter "combined_mode=libata" or "combined_mode=ide" to allow the specified driver to claim all IDE ports. (WORKS!!!)
    * Disable libata (CONFIG_ATA) entirely, and enable CONFIG_BLK_DEV_IDE_SATA. (NOT TESTED)
    * (newer choice, with less field testing) Disable CONFIG_IDE, and permit libata to run all your IDE and SATA ports. (NOT TESTED)

My System configuration is:
cla@cla-desktop:~$ lspci
00:00.0 Host bridge: Intel Corporation 82845 845 [Brookdale] Chipset Host Bridge (rev 03)
00:01.0 PCI bridge: Intel Corporation 82845 845 [Brookdale] Chipset AGP Bridge (rev 03)
00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev 12)
00:1f.0 ISA bridge: Intel Corporation 82801BA ISA Bridge (LPC) (rev 12)
00:1f.1 IDE interface: Intel Corporation 82801BA IDE U100 Controller (rev 12)
00:1f.2 USB Controller: Intel Corporation 82801BA/BAM USB Controller #1 (rev 12)
00:1f.3 SMBus: Intel Corporation 82801BA/BAM SMBus Controller (rev 12)
00:1f.4 USB Controller: Intel Corporation 82801BA/BAM USB Controller #1 (rev 12)
01:00.0 VGA compatible controller: nVidia Corporation NV11 [GeForce2 MX/MX 400] (rev b2)
02:01.0 Ethernet controller: VIA Technologies, Inc. VT6102 [Rhine-II] (rev 42)
02:02.0 Modem: PCTel Inc HSP MicroModem 56 (rev 02)
02:06.0 Multimedia audio controller: Creative Labs SB Live! EMU10k1 (rev 07)
02:06.1 Input device controller: Creative Labs SB Live! Game Port (rev 07)

hdparm output
Without fix:
cla@cla-desktop:~$ sudo hdparm -tT /dev/sda1

/dev/sda1:
 Timing cached reads: 402 MB in 2.01 seconds = 200.20 MB/sec
 Timing buffered disk reads: 72 MB in 3.00 seconds = 10.98 MB/sec

With fix:
cla@cla-desktop:~$ sudo hdparm -tT /dev/sda1

/dev/sda1:
 Timing cached reads: 402 MB in 2.01 seconds = 200.20 MB/sec
 Timing buffered disk reads: 72 MB in 3.00 seconds = 23.98 MB/sec