diff --git a/drivers/ata/pata_efar.c b/drivers/ata/pata_efar.c
index 2a6412f5d117..540c36426303 100644
--- a/drivers/ata/pata_efar.c
+++ b/drivers/ata/pata_efar.c
@@ -2,6 +2,7 @@
  *    pata_efar.c - EFAR PIIX clone controller driver
  *
  *	(C) 2005 Red Hat
+ *	(C) 2009 Bartlomiej Zolnierkiewicz
  *
  *    Some parts based on ata_piix.c by Jeff Garzik and others.
  *
@@ -118,12 +119,12 @@ static void efar_set_piomode (struct ata_port *ap, struct ata_device *adev)
 		int shift = 4 * ap->port_no;
 		u8 slave_data;
 
-		idetm_data &= 0xCC0F;
+		idetm_data &= 0xFF0F;
 		idetm_data |= (control << 4);
 
 		/* Slave timing in separate register */
 		pci_read_config_byte(dev, 0x44, &slave_data);
-		slave_data &= 0x0F << shift;
+		slave_data &= ap->port_no ? 0x0F : 0xF0;
 		slave_data |= ((timings[pio][0] << 2) | timings[pio][1]) << shift;
 		pci_write_config_byte(dev, 0x44, slave_data);
 	}