diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index dce6565..ad8e2c6 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -870,7 +870,11 @@
 		 * the PIO timing number for the maximum. Turn it into
 		 * a mask.
 		 */
-		pio_mask = (2 << (id[ATA_ID_OLD_PIO_MODES] & 0xFF)) - 1 ;
+		u8 mode = id[ATA_ID_OLD_PIO_MODES] & 0xFF;
+		if (mode < 5)	/* Valid PIO range */
+                	pio_mask = (2 << mode) - 1;
+		else
+			pio_mask = 1;
 
 		/* But wait.. there's more. Design your standards by
 		 * committee and you too can get a free iordy field to