diff --git a/drivers/rtc/rtc-s3c.c b/drivers/rtc/rtc-s3c.c
index e2636ff..bb88027 100644
--- a/drivers/rtc/rtc-s3c.c
+++ b/drivers/rtc/rtc-s3c.c
@@ -82,12 +82,14 @@ static int s3c_rtc_setaie(struct device *dev, unsigned int enabled)
 
 	pr_debug("%s: aie=%d\n", __func__, enabled);
 
+	spin_lock_irq(&s3c_rtc_pie_lock);
 	tmp = readb(s3c_rtc_base + S3C2410_RTCALM) & ~S3C2410_RTCALM_ALMEN;
 
 	if (enabled)
 		tmp |= S3C2410_RTCALM_ALMEN;
 
 	writeb(tmp, s3c_rtc_base + S3C2410_RTCALM);
+	spin_unlock_irq(&s3c_rtc_pie_lock);
 
 	return 0;
 }