diff --git a/src/drivers/pc80/tpm/tis.c b/src/drivers/pc80/tpm/tis.c
index 2b29acf..c209e5a 100644
--- a/src/drivers/pc80/tpm/tis.c
+++ b/src/drivers/pc80/tpm/tis.c
@@ -22,6 +22,7 @@
 #include <security/tpm/tis.h>
 #include <device/pnp.h>
 #include <drivers/tpm/tpm_ppi.h>
+#include <timer.h>
 #include "chip.h"
 
 #define PREFIX "lpc_tpm: "
@@ -84,7 +85,7 @@
 #define TPM_DRIVER_ERR		(~0)
 
  /* 1 second is plenty for anything TPM does.*/
-#define MAX_DELAY_US	(1000 * 1000)
+#define MAX_DELAY_US	USECS_PER_SEC
 
 /*
  * Structures defined below allow creating descriptions of TPM vendor/device
@@ -238,7 +239,7 @@
 /*
  * tis_wait_sts()
  *
- * Wait for at least a second for a status to change its state to match the
+ * Wait for at most a second for a status to change its state to match the
  * expected state. Normally the transition happens within microseconds.
  *
  * @locality - locality
@@ -249,14 +250,15 @@
  */
 static int tis_wait_sts(int locality, u8 mask, u8 expected)
 {
-	u32 time_us = MAX_DELAY_US;
-	while (time_us > 0) {
+	struct stopwatch sw;
+
+	stopwatch_init_usecs_expire(&sw, MAX_DELAY_US);
+	do {
 		u8 value = tpm_read_status(locality);
 		if ((value & mask) == expected)
 			return 0;
-		udelay(1); /* 1 us */
-		time_us--;
-	}
+		udelay(1);
+	} while (!stopwatch_expired(&sw));
 	return TPM_TIMEOUT_ERR;
 }
 
@@ -291,7 +293,7 @@
 /*
  * tis_wait_access()
  *
- * Wait for at least a second for a access to change its state to match the
+ * Wait for at most a second for a access to change its state to match the
  * expected state. Normally the transition happens within microseconds.
  *
  * @locality - locality
@@ -302,14 +304,15 @@
  */
 static int tis_wait_access(int locality, u8 mask, u8 expected)
 {
-	u32 time_us = MAX_DELAY_US;
-	while (time_us > 0) {
+	struct stopwatch sw;
+
+	stopwatch_init_usecs_expire(&sw, MAX_DELAY_US);
+	do {
 		u8 value = tpm_read_access(locality);
 		if ((value & mask) == expected)
 			return 0;
-		udelay(1); /* 1 us */
-		time_us--;
-	}
+		udelay(1);
+	} while (!stopwatch_expired(&sw));
 	return TPM_TIMEOUT_ERR;
 }
 
@@ -440,7 +443,6 @@
 {
 	u32 offset = 0;
 	u16 burst = 0;
-	u32 max_cycles = 0;
 	u8 locality = 0;
 
 	if (tis_wait_ready(locality)) {
@@ -452,10 +454,12 @@
 
 	while (1) {
 		unsigned int count;
+		struct stopwatch sw;
 
 		/* Wait till the device is ready to accept more data. */
+		stopwatch_init_usecs_expire(&sw, MAX_DELAY_US);
 		while (!burst) {
-			if (max_cycles++ == MAX_DELAY_US) {
+			if (stopwatch_expired(&sw)) {
 				printf("%s:%d failed to feed %d bytes of %d\n",
 				       __FILE__, __LINE__, len - offset, len);
 				return TPM_DRIVER_ERR;
@@ -464,8 +468,6 @@
 			burst = tpm_read_burst_count(locality);
 		}
 
-		max_cycles = 0;
-
 		/*
 		 * Calculate number of bytes the TPM is ready to accept in one
 		 * shot.