--- /dev/null
+I think that I've found and fixed the problem. There is a copy/paste bug in
+vt6421_set_dma_mode() function which causes wrong values to be written to
+PATA_UDMA_TIMING register.
+
+
+This patch fixes a copy/paste bug that breaks DMA modes on VT6421 PATA port.
+
+Signed-off-by: Ondrej Zary <linux@rain...>
+diff -Nur linux-2.6.21.6/drivers/ata/sata_via.c linux-2.6.21.6-new/drivers/ata/sata_via.c
+--- linux-2.6.21.6/drivers/ata/sata_via.c 2007-07-07 06:47:55.000000000 +0200
++++ linux-2.6.21.6-new/drivers/ata/sata_via.c 2007-09-29 11:05:07.000000000 +0200
+@@ -380,6 +380,6 @@
+ {
+ struct pci_dev *pdev = to_pci_dev(ap->host->dev);
+ static const u8 udma_bits[] = { 0xEE, 0xE8, 0xE6, 0xE4, 0xE2, 0xE1, 0xE0, 0xE0 };
+- pci_write_config_byte(pdev, PATA_UDMA_TIMING, udma_bits[adev->pio_mode - XFER_UDMA_0]);
++ pci_write_config_byte(pdev, PATA_UDMA_TIMING, udma_bits[adev->dma_mode - XFER_UDMA_0]);
+ }
+