diff --git a/drivers/ide/ide-lib.c b/drivers/ide/ide-lib.c
index 850ef63..8237d89 100644
--- a/drivers/ide/ide-lib.c
+++ b/drivers/ide/ide-lib.c
@@ -71,75 +71,96 @@
 /**
  *	ide_dma_speed	-	compute DMA speed
  *	@drive: drive
- *	@mode; intended mode
+ *	@mode:	modes available
  *
  *	Checks the drive capabilities and returns the speed to use
- *	for the transfer. Returns -1 if the requested mode is unknown
- *	(eg PIO)
+ *	for the DMA transfer.  Returns 0 if the drive is incapable
+ *	of DMA transfers.
  */
  
 u8 ide_dma_speed(ide_drive_t *drive, u8 mode)
 {
 	struct hd_driveid *id   = drive->id;
 	ide_hwif_t *hwif	= HWIF(drive);
+	u8 ultra_mask, mwdma_mask, swdma_mask;
 	u8 speed = 0;
 
 	if (drive->media != ide_disk && hwif->atapi_dma == 0)
 		return 0;
 
-	switch(mode) {
-		case 0x04:
-			if ((id->dma_ultra & 0x0040) &&
-			    (id->dma_ultra & hwif->ultra_mask))
-				{ speed = XFER_UDMA_6; break; }
-		case 0x03:
-			if ((id->dma_ultra & 0x0020) &&
-			    (id->dma_ultra & hwif->ultra_mask))
-				{ speed = XFER_UDMA_5; break; }
-		case 0x02:
-			if ((id->dma_ultra & 0x0010) &&
-			    (id->dma_ultra & hwif->ultra_mask))
-				{ speed = XFER_UDMA_4; break; }
-			if ((id->dma_ultra & 0x0008) &&
-			    (id->dma_ultra & hwif->ultra_mask))
-				{ speed = XFER_UDMA_3; break; }
-		case 0x01:
-			if ((id->dma_ultra & 0x0004) &&
-			    (id->dma_ultra & hwif->ultra_mask))
-				{ speed = XFER_UDMA_2; break; }
-			if ((id->dma_ultra & 0x0002) &&
-			    (id->dma_ultra & hwif->ultra_mask))
-				{ speed = XFER_UDMA_1; break; }
-			if ((id->dma_ultra & 0x0001) &&
-			    (id->dma_ultra & hwif->ultra_mask))
-				{ speed = XFER_UDMA_0; break; }
-		case 0x00:
-			if ((id->dma_mword & 0x0004) &&
-			    (id->dma_mword & hwif->mwdma_mask))
-				{ speed = XFER_MW_DMA_2; break; }
-			if ((id->dma_mword & 0x0002) &&
-			    (id->dma_mword & hwif->mwdma_mask))
-				{ speed = XFER_MW_DMA_1; break; }
-			if ((id->dma_mword & 0x0001) &&
-			    (id->dma_mword & hwif->mwdma_mask))
-				{ speed = XFER_MW_DMA_0; break; }
-			if ((id->dma_1word & 0x0004) &&
-			    (id->dma_1word & hwif->swdma_mask))
-				{ speed = XFER_SW_DMA_2; break; }
-			if ((id->dma_1word & 0x0002) &&
-			    (id->dma_1word & hwif->swdma_mask))
-				{ speed = XFER_SW_DMA_1; break; }
-			if ((id->dma_1word & 0x0001) &&
-			    (id->dma_1word & hwif->swdma_mask))
-				{ speed = XFER_SW_DMA_0; break; }
-	}
+	/* Capable of UltraDMA modes? */
+	ultra_mask = id->dma_ultra & hwif->ultra_mask;
 
-//	printk("%s: %s: mode 0x%02x, speed 0x%02x\n",
-//		__FUNCTION__, drive->name, mode, speed);
+	if (!(id->field_valid & 4))
+		mode = 0;	/* fallback to MW/SW DMA if no UltraDMA */
+
+	switch (mode) {
+	case 4:
+		if (ultra_mask & 0x40) {
+			speed = XFER_UDMA_6;
+			break;
+		}
+	case 3:
+		if (ultra_mask & 0x20) {
+			speed = XFER_UDMA_5;
+			break;
+		}
+	case 2:
+		if (ultra_mask & 0x10) {
+			speed = XFER_UDMA_4;
+			break;
+		}
+		if (ultra_mask & 0x08) {
+			speed = XFER_UDMA_3;
+			break;
+		}
+	case 1:
+		if (ultra_mask & 0x04) {
+			speed = XFER_UDMA_2;
+			break;
+		}
+		if (ultra_mask & 0x02) {
+			speed = XFER_UDMA_1;
+			break;
+		}
+		if (ultra_mask & 0x01) {
+			speed = XFER_UDMA_0;
+			break;
+		}
+	case 0:
+		mwdma_mask = id->dma_mword & hwif->mwdma_mask;
+
+		if (mwdma_mask & 0x04) {
+			speed = XFER_MW_DMA_2;
+			break;
+		}
+		if (mwdma_mask & 0x02) {
+			speed = XFER_MW_DMA_1;
+			break;
+		}
+		if (mwdma_mask & 0x01) {
+			speed = XFER_MW_DMA_0;
+			break;
+		}
+
+		swdma_mask = id->dma_1word & hwif->swdma_mask;
+
+		if (swdma_mask & 0x04) {
+			speed = XFER_SW_DMA_2;
+			break;
+		}
+		if (swdma_mask & 0x02) {
+			speed = XFER_SW_DMA_1;
+			break;
+		}
+		if (swdma_mask & 0x01) {
+			speed = XFER_SW_DMA_0;
+			break;
+		}
+	}
 
 	return speed;
 }
-
 EXPORT_SYMBOL(ide_dma_speed);