diff --git a/arch/arm/mach-s3c64xx/common.c b/arch/arm/mach-s3c64xx/common.c
index 7c66ce1a6bb6..9843eb4dd04e 100644
--- a/arch/arm/mach-s3c64xx/common.c
+++ b/arch/arm/mach-s3c64xx/common.c
@@ -56,7 +56,8 @@
 #include "watchdog-reset.h"
 
 /* External clock frequency */
-static unsigned long xtal_f = 12000000, xusbxti_f = 48000000;
+static unsigned long xtal_f __ro_after_init = 12000000;
+static unsigned long xusbxti_f __ro_after_init = 48000000;
 
 void __init s3c64xx_set_xtal_freq(unsigned long freq)
 {