diff --git a/drivers/ata/pata_efar.c b/drivers/ata/pata_efar.c
index 5556163c80de..1617421f7e76 100644
--- a/drivers/ata/pata_efar.c
+++ b/drivers/ata/pata_efar.c
@@ -68,6 +68,8 @@ static int efar_cable_detect(struct ata_port *ap)
 	return ATA_CBL_PATA80;
 }
 
+static DEFINE_SPINLOCK(efar_lock);
+
 /**
  *	efar_set_piomode - Initialize host controller PATA PIO timings
  *	@ap: Port whose timings we are configuring
@@ -84,7 +86,9 @@ static void efar_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 int idetm_port= ap->port_no ? 0x42 : 0x40;
+	unsigned long flags;
 	u16 idetm_data;
+	u8 udma_enable;
 	int control = 0;
 
 	/*
@@ -107,6 +111,8 @@ static void efar_set_piomode (struct ata_port *ap, struct ata_device *adev)
 	if (adev->class == ATA_DEV_ATA)
 		control |= 4;	/* PPE */
 
+	spin_lock_irqsave(&efar_lock, flags);
+
 	pci_read_config_word(dev, idetm_port, &idetm_data);
 
 	/* Set PPE, IE, and TIME as appropriate */
@@ -131,6 +137,11 @@ static void efar_set_piomode (struct ata_port *ap, struct ata_device *adev)
 
 	idetm_data |= 0x4000;	/* Ensure SITRE is set */
 	pci_write_config_word(dev, idetm_port, idetm_data);
+
+	pci_read_config_byte(dev, 0x48, &udma_enable);
+	udma_enable &= ~(1 << (2 * ap->port_no + adev->devno));
+	pci_write_config_byte(dev, 0x48, udma_enable);
+	spin_unlock_irqrestore(&efar_lock, flags);
 }
 
 /**
@@ -151,6 +162,7 @@ static void efar_set_dmamode (struct ata_port *ap, struct ata_device *adev)
 	u16 master_data;
 	u8 speed		= adev->dma_mode;
 	int devid		= adev->devno + 2 * ap->port_no;
+	unsigned long flags;
 	u8 udma_enable;
 
 	static const	 /* ISP  RTC */
@@ -160,6 +172,8 @@ static void efar_set_dmamode (struct ata_port *ap, struct ata_device *adev)
 			    { 2, 1 },
 			    { 2, 3 }, };
 
+	spin_lock_irqsave(&efar_lock, flags);
+
 	pci_read_config_word(dev, master_port, &master_data);
 	pci_read_config_byte(dev, 0x48, &udma_enable);
 
@@ -217,6 +231,7 @@ static void efar_set_dmamode (struct ata_port *ap, struct ata_device *adev)
 		pci_write_config_word(dev, master_port, master_data);
 	}
 	pci_write_config_byte(dev, 0x48, udma_enable);
+	spin_unlock_irqrestore(&efar_lock, flags);
 }
 
 static struct scsi_host_template efar_sht = {