diff --git a/chip/lm4/clock.c b/chip/lm4/clock.c
index bc4b865403..99c83422f7 100644
--- a/chip/lm4/clock.c
+++ b/chip/lm4/clock.c
@@ -140,8 +140,8 @@ void clock_enable_pll(int enable, int notify)
 
 void clock_wait_cycles(uint32_t cycles)
 {
-	asm("1: subs %0, #1\n"
-	    "   bne 1b\n" :: "r"(cycles));
+	asm volatile("1: subs %0, #1\n"
+		     "   bne 1b\n" : "+r"(cycles));
 }
 
 int clock_get_freq(void)
diff --git a/chip/mec1322/clock.c b/chip/mec1322/clock.c
index c305b16ffc..d86f1bc5a7 100644
--- a/chip/mec1322/clock.c
+++ b/chip/mec1322/clock.c
@@ -49,8 +49,8 @@ static int freq = 48000000;
 
 void clock_wait_cycles(uint32_t cycles)
 {
-	asm("1: subs %0, #1\n"
-	    "   bne 1b\n" :: "r"(cycles));
+	asm volatile("1: subs %0, #1\n"
+		     "   bne 1b\n" : "+r"(cycles));
 }
 
 int clock_get_freq(void)
diff --git a/chip/npcx/clock.c b/chip/npcx/clock.c
index 196248c592..34a9b6a726 100644
--- a/chip/npcx/clock.c
+++ b/chip/npcx/clock.c
@@ -227,8 +227,8 @@ int clock_get_apb2_freq(void)
  */
 void clock_wait_cycles(uint32_t cycles)
 {
-	asm("1: subs %0, #1\n"
-	"   bne 1b\n" : : "r"(cycles));
+	asm volatile("1: subs %0, #1\n"
+		     "   bne 1b\n" : "+r"(cycles));
 }
 
 #ifdef CONFIG_LOW_POWER_IDLE