diff --git a/drivers/ata/ata_piix.c b/drivers/ata/ata_piix.c
index 56b8a3ff12865041af813ca0bcfa49db143e5169..9ac4e378992ef60d71634121379b91479c8660f2 100644
--- a/drivers/ata/ata_piix.c
+++ b/drivers/ata/ata_piix.c
@@ -664,6 +664,8 @@ static int piix_pata_prereset(struct ata_link *link, unsigned long deadline)
 	return ata_sff_prereset(link, deadline);
 }
 
+static DEFINE_SPINLOCK(piix_lock);
+
 /**
  *	piix_set_piomode - Initialize host controller PATA PIO timings
  *	@ap: Port whose timings we are configuring
@@ -677,8 +679,9 @@ static int piix_pata_prereset(struct ata_link *link, unsigned long deadline)
 
 static void piix_set_piomode(struct ata_port *ap, struct ata_device *adev)
 {
-	unsigned int pio	= adev->pio_mode - XFER_PIO_0;
 	struct pci_dev *dev	= to_pci_dev(ap->host->dev);
+	unsigned long flags;
+	unsigned int pio	= adev->pio_mode - XFER_PIO_0;
 	unsigned int is_slave	= (adev->devno != 0);
 	unsigned int master_port= ap->port_no ? 0x42 : 0x40;
 	unsigned int slave_port	= 0x44;
@@ -708,6 +711,8 @@ static void piix_set_piomode(struct ata_port *ap, struct ata_device *adev)
 	if (adev->class == ATA_DEV_ATA)
 		control |= 4;	/* PPE enable */
 
+	spin_lock_irqsave(&piix_lock, flags);
+
 	/* PIO configuration clears DTE unconditionally.  It will be
 	 * programmed in set_dmamode which is guaranteed to be called
 	 * after set_piomode if any DMA mode is available.
@@ -747,6 +752,8 @@ static void piix_set_piomode(struct ata_port *ap, struct ata_device *adev)
 		udma_enable &= ~(1 << (2 * ap->port_no + adev->devno));
 		pci_write_config_byte(dev, 0x48, udma_enable);
 	}
+
+	spin_unlock_irqrestore(&piix_lock, flags);
 }
 
 /**
@@ -764,6 +771,7 @@ static void piix_set_piomode(struct ata_port *ap, struct ata_device *adev)
 static void do_pata_set_dmamode(struct ata_port *ap, struct ata_device *adev, int isich)
 {
 	struct pci_dev *dev	= to_pci_dev(ap->host->dev);
+	unsigned long flags;
 	u8 master_port		= ap->port_no ? 0x42 : 0x40;
 	u16 master_data;
 	u8 speed		= adev->dma_mode;
@@ -777,6 +785,8 @@ static void do_pata_set_dmamode(struct ata_port *ap, struct ata_device *adev, in
 			    { 2, 1 },
 			    { 2, 3 }, };
 
+	spin_lock_irqsave(&piix_lock, flags);
+
 	pci_read_config_word(dev, master_port, &master_data);
 	if (ap->udma_mask)
 		pci_read_config_byte(dev, 0x48, &udma_enable);
@@ -867,6 +877,8 @@ static void do_pata_set_dmamode(struct ata_port *ap, struct ata_device *adev, in
 	/* Don't scribble on 0x48 if the controller does not support UDMA */
 	if (ap->udma_mask)
 		pci_write_config_byte(dev, 0x48, udma_enable);
+
+	spin_unlock_irqrestore(&piix_lock, flags);
 }
 
 /**