diff --git a/drivers/ata/ata_piix.c b/drivers/ata/ata_piix.c
index 7409f98..3971bc0 100644
--- a/drivers/ata/ata_piix.c
+++ b/drivers/ata/ata_piix.c
@@ -158,6 +158,7 @@ struct piix_map_db {
 struct piix_host_priv {
 	const int *map;
 	u32 saved_iocfg;
+	spinlock_t sidpr_lock;	/* FIXME: remove once locking in EH is fixed */
 	void __iomem *sidpr;
 };
 
@@ -951,12 +952,15 @@ static int piix_sidpr_scr_read(struct ata_link *link,
 			       unsigned int reg, u32 *val)
 {
 	struct piix_host_priv *hpriv = link->ap->host->private_data;
+	unsigned long flags;
 
 	if (reg >= ARRAY_SIZE(piix_sidx_map))
 		return -EINVAL;
 
+	spin_lock_irqsave(&hpriv->sidpr_lock, flags);
 	piix_sidpr_sel(link, reg);
 	*val = ioread32(hpriv->sidpr + PIIX_SIDPR_DATA);
+	spin_unlock_irqrestore(&hpriv->sidpr_lock, flags);
 	return 0;
 }
 
@@ -964,12 +968,15 @@ static int piix_sidpr_scr_write(struct ata_link *link,
 				unsigned int reg, u32 val)
 {
 	struct piix_host_priv *hpriv = link->ap->host->private_data;
+	unsigned long flags;
 
 	if (reg >= ARRAY_SIZE(piix_sidx_map))
 		return -EINVAL;
 
+	spin_lock_irqsave(&hpriv->sidpr_lock, flags);
 	piix_sidpr_sel(link, reg);
 	iowrite32(val, hpriv->sidpr + PIIX_SIDPR_DATA);
+	spin_unlock_irqrestore(&hpriv->sidpr_lock, flags);
 	return 0;
 }
 
@@ -1566,6 +1573,7 @@ static int __devinit piix_init_one(struct pci_dev *pdev,
 	hpriv = devm_kzalloc(dev, sizeof(*hpriv), GFP_KERNEL);
 	if (!hpriv)
 		return -ENOMEM;
+	spin_lock_init(&hpriv->sidpr_lock);
 
 	/* Save IOCFG, this will be used for cable detection, quirk
 	 * detection and restoration on detach.  This is necessary