diff --git a/drivers/ata/pata_ali.c b/drivers/ata/pata_ali.c
index 3c55a5ff74c761ac8cf9e00d5056146458cae1ee..75e95bdbe02fec28c84183cdcedcd6be942d8eb0 100644
--- a/drivers/ata/pata_ali.c
+++ b/drivers/ata/pata_ali.c
@@ -550,22 +550,22 @@ static int ali_init_one(struct pci_dev *pdev, const struct pci_device_id *id)
 		.udma_mask = 0x1f,
 		.port_ops = &ali_c2_port_ops
 	};
-	/* Revision 0xC3 is UDMA100 */
+	/* Revision 0xC3 is UDMA66 for now */
 	static const struct ata_port_info info_c3 = {
 		.sht = &ali_sht,
 		.flags = ATA_FLAG_SLAVE_POSS | ATA_FLAG_SRST | ATA_FLAG_PIO_LBA48,
 		.pio_mask = 0x1f,
 		.mwdma_mask = 0x07,
-		.udma_mask = 0x3f,
+		.udma_mask = 0x1f,
 		.port_ops = &ali_c2_port_ops
 	};
-	/* Revision 0xC4 is UDMA133 */
+	/* Revision 0xC4 is UDMA100 */
 	static const struct ata_port_info info_c4 = {
 		.sht = &ali_sht,
 		.flags = ATA_FLAG_SLAVE_POSS | ATA_FLAG_SRST | ATA_FLAG_PIO_LBA48,
 		.pio_mask = 0x1f,
 		.mwdma_mask = 0x07,
-		.udma_mask = 0x7f,
+		.udma_mask = 0x3f,
 		.port_ops = &ali_c2_port_ops
 	};
 	/* Revision 0xC5 is UDMA133 with LBA48 DMA */