diff --git a/sys/dev/tpm/tpm20.c b/sys/dev/tpm/tpm20.c
index 68a30cfb51dd..3f444176732c 100644
--- a/sys/dev/tpm/tpm20.c
+++ b/sys/dev/tpm/tpm20.c
@@ -39,13 +39,13 @@ __FBSDID("$FreeBSD$");
  * we don't want to execute this too often
  * as the chip is likely to be used by others too.
  */
-#define TPM_HARVEST_INTERVAL 10000000
+#define TPM_HARVEST_INTERVAL 10
 
 MALLOC_DEFINE(M_TPM20, "tpm_buffer", "buffer for tpm 2.0 driver");
 
 static void tpm20_discard_buffer(void *arg);
 #ifdef TPM_HARVEST
-static void tpm20_harvest(void *arg);
+static void tpm20_harvest(void *arg, int unused);
 #endif
 static int  tpm20_save_state(device_t dev, bool suspend);
 
@@ -192,11 +192,6 @@ tpm20_init(struct tpm_sc *sc)
 
 	cv_init(&sc->buf_cv, "TPM buffer cv");
 	callout_init(&sc->discard_buffer_callout, 1);
-#ifdef TPM_HARVEST
-	sc->harvest_ticks = TPM_HARVEST_INTERVAL / tick;
-	callout_init(&sc->harvest_callout, 1);
-	callout_reset(&sc->harvest_callout, 0, tpm20_harvest, sc);
-#endif
 	sc->pending_data_length = 0;
 
 	make_dev_args_init(&args);
@@ -209,6 +204,12 @@ tpm20_init(struct tpm_sc *sc)
 	if (result != 0)
 		tpm20_release(sc);
 
+#ifdef TPM_HARVEST
+	TIMEOUT_TASK_INIT(taskqueue_thread, &sc->harvest_task, 0,
+	    tpm20_harvest, sc);
+	taskqueue_enqueue_timeout(taskqueue_thread, &sc->harvest_task, 0);
+#endif
+
 	return (result);
 
 }
@@ -218,7 +219,8 @@ tpm20_release(struct tpm_sc *sc)
 {
 
 #ifdef TPM_HARVEST
-	callout_drain(&sc->harvest_callout);
+	if (device_is_attached(sc->dev))
+		taskqueue_drain_timeout(taskqueue_thread, &sc->harvest_task);
 #endif
 
 	if (sc->buf != NULL)
@@ -243,13 +245,12 @@ tpm20_shutdown(device_t dev)
 }
 
 #ifdef TPM_HARVEST
-
 /*
  * Get TPM_HARVEST_SIZE random bytes and add them
  * into system entropy pool.
  */
 static void
-tpm20_harvest(void *arg)
+tpm20_harvest(void *arg, int unused)
 {
 	struct tpm_sc *sc;
 	unsigned char entropy[TPM_HARVEST_SIZE];
@@ -290,7 +291,8 @@ tpm20_harvest(void *arg)
 	if (entropy_size > 0)
 		random_harvest_queue(entropy, entropy_size, RANDOM_PURE_TPM);
 
-	callout_reset(&sc->harvest_callout, sc->harvest_ticks, tpm20_harvest, sc);
+	taskqueue_enqueue_timeout(taskqueue_thread, &sc->harvest_task,
+	    hz * TPM_HARVEST_INTERVAL);
 }
 #endif	/* TPM_HARVEST */
 
diff --git a/sys/dev/tpm/tpm20.h b/sys/dev/tpm/tpm20.h
index 6911ca0cb6fe..bda4987120b0 100644
--- a/sys/dev/tpm/tpm20.h
+++ b/sys/dev/tpm/tpm20.h
@@ -44,6 +44,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/module.h>
 #include <sys/rman.h>
 #include <sys/sx.h>
+#include <sys/taskqueue.h>
 #include <sys/uio.h>
 
 #include <machine/bus.h>
@@ -125,8 +126,7 @@ struct tpm_sc {
 
 	struct callout 	discard_buffer_callout;
 #ifdef TPM_HARVEST
-	struct callout 	harvest_callout;
-	int		harvest_ticks;
+	struct timeout_task 	harvest_task;
 #endif
 
 	int		(*transmit)(struct tpm_sc *, size_t);