diff --git a/drivers/media/pci/cobalt/cobalt-driver.c b/drivers/media/pci/cobalt/cobalt-driver.c
index 839503e654f4..16af58f2f93c 100644
--- a/drivers/media/pci/cobalt/cobalt-driver.c
+++ b/drivers/media/pci/cobalt/cobalt-driver.c
@@ -667,6 +667,7 @@ static int cobalt_probe(struct pci_dev *pci_dev,
 		return -ENOMEM;
 	cobalt->pci_dev = pci_dev;
 	cobalt->instance = i;
+	mutex_init(&cobalt->pci_lock);
 
 	retval = v4l2_device_register(&pci_dev->dev, &cobalt->v4l2_dev);
 	if (retval) {
diff --git a/drivers/media/pci/cobalt/cobalt-driver.h b/drivers/media/pci/cobalt/cobalt-driver.h
index bca68572b324..12c33e035904 100644
--- a/drivers/media/pci/cobalt/cobalt-driver.h
+++ b/drivers/media/pci/cobalt/cobalt-driver.h
@@ -251,6 +251,8 @@ struct cobalt {
 	int instance;
 	struct pci_dev *pci_dev;
 	struct v4l2_device v4l2_dev;
+	/* serialize PCI access in cobalt_s_bit_sysctrl() */
+	struct mutex pci_lock;
 
 	void __iomem *bar0, *bar1;
 
@@ -320,10 +322,13 @@ static inline u32 cobalt_g_sysctrl(struct cobalt *cobalt)
 static inline void cobalt_s_bit_sysctrl(struct cobalt *cobalt,
 					int bit, int val)
 {
-	u32 ctrl = cobalt_read_bar1(cobalt, COBALT_SYS_CTRL_BASE);
+	u32 ctrl;
 
+	mutex_lock(&cobalt->pci_lock);
+	ctrl = cobalt_read_bar1(cobalt, COBALT_SYS_CTRL_BASE);
 	cobalt_write_bar1(cobalt, COBALT_SYS_CTRL_BASE,
 			(ctrl & ~(1UL << bit)) | (val << bit));
+	mutex_unlock(&cobalt->pci_lock);
 }
 
 static inline u32 cobalt_g_sysstat(struct cobalt *cobalt)