diff --git a/lib/efi_selftest/Makefile b/lib/efi_selftest/Makefile
index a71c8bf..ddf304e 100644
--- a/lib/efi_selftest/Makefile
+++ b/lib/efi_selftest/Makefile
@@ -13,8 +13,11 @@
 CFLAGS_REMOVE_efi_selftest_console.o := $(CFLAGS_NON_EFI)
 CFLAGS_efi_selftest_events.o := $(CFLAGS_EFI)
 CFLAGS_REMOVE_efi_selftest_events.o := $(CFLAGS_NON_EFI)
+CFLAGS_efi_selftest_tpl.o := $(CFLAGS_EFI)
+CFLAGS_REMOVE_efi_selftest_tpl.o := $(CFLAGS_NON_EFI)
 
 obj-$(CONFIG_CMD_BOOTEFI_SELFTEST) += \
 efi_selftest.o \
 efi_selftest_console.o \
-efi_selftest_events.o
+efi_selftest_events.o \
+efi_selftest_tpl.o
diff --git a/lib/efi_selftest/efi_selftest_tpl.c b/lib/efi_selftest/efi_selftest_tpl.c
new file mode 100644
index 0000000..90ace0f
--- /dev/null
+++ b/lib/efi_selftest/efi_selftest_tpl.c
@@ -0,0 +1,214 @@
+/*
+ * efi_selftest_events
+ *
+ * Copyright (c) 2017 Heinrich Schuchardt <xypron.glpk@gmx.de>
+ *
+ * SPDX-License-Identifier:     GPL-2.0+
+ *
+ * This unit test uses timer events to check the handling of
+ * task priority levels.
+ */
+
+#include <efi_selftest.h>
+
+static struct efi_event *event_notify;
+static struct efi_event *event_wait;
+static unsigned int counter;
+static struct efi_boot_services *boottime;
+
+/*
+ * Notification function, increments a counter.
+ *
+ * @event	notified event
+ * @context	pointer to the counter
+ */
+static void EFIAPI notify(struct efi_event *event, void *context)
+{
+	if (!context)
+		return;
+	++*(unsigned int *)context;
+}
+
+/*
+ * Setup unit test.
+ *
+ * Create two timer events.
+ * One with EVT_NOTIFY_SIGNAL, the other with EVT_NOTIFY_WAIT.
+ *
+ * @handle:	handle of the loaded image
+ * @systable:	system table
+ */
+static int setup(const efi_handle_t handle,
+		 const struct efi_system_table *systable)
+{
+	efi_status_t ret;
+
+	boottime = systable->boottime;
+
+	ret = boottime->create_event(EVT_TIMER | EVT_NOTIFY_SIGNAL,
+				     TPL_CALLBACK, notify, (void *)&counter,
+				     &event_notify);
+	if (ret != EFI_SUCCESS) {
+		efi_st_error("could not create event\n");
+		return 1;
+	}
+	ret = boottime->create_event(EVT_TIMER | EVT_NOTIFY_WAIT,
+				     TPL_HIGH_LEVEL, notify, NULL, &event_wait);
+	if (ret != EFI_SUCCESS) {
+		efi_st_error("could not create event\n");
+		return 1;
+	}
+	return 0;
+}
+
+/*
+ * Tear down unit test.
+ *
+ * Close the events created in setup.
+ */
+static int teardown(void)
+{
+	efi_status_t ret;
+
+	if (event_notify) {
+		ret = boottime->close_event(event_notify);
+		event_notify = NULL;
+		if (ret != EFI_SUCCESS) {
+			efi_st_error("could not close event\n");
+			return 1;
+		}
+	}
+	if (event_wait) {
+		ret = boottime->close_event(event_wait);
+		event_wait = NULL;
+		if (ret != EFI_SUCCESS) {
+			efi_st_error("could not close event\n");
+			return 1;
+		}
+	}
+	boottime->restore_tpl(TPL_APPLICATION);
+	return 0;
+}
+
+/*
+ * Execute unit test.
+ *
+ * Run a 10 ms periodic timer and check that it is called 10 times
+ * while waiting for 100 ms single shot timer.
+ *
+ * Raise the TPL level to the level of the 10 ms timer and observe
+ * that the notification function is not called again.
+ *
+ * Lower the TPL level and check that the queued notification
+ * function is called.
+ */
+static int execute(void)
+{
+	unsigned long index;
+	efi_status_t ret;
+	UINTN old_tpl;
+
+	/* Set 10 ms timer */
+	counter = 0;
+	ret = boottime->set_timer(event_notify, EFI_TIMER_PERIODIC, 100000);
+	if (ret != EFI_SUCCESS) {
+		efi_st_error("Could not set timer\n");
+		return 1;
+	}
+	/* Set 100 ms timer */
+	ret = boottime->set_timer(event_wait, EFI_TIMER_RELATIVE, 1000000);
+	if (ret != EFI_SUCCESS) {
+		efi_st_error("Could not set timer\n");
+		return 1;
+	}
+	index = 5;
+	ret = boottime->wait_for_event(1, &event_wait, &index);
+	if (ret != EFI_SUCCESS) {
+		efi_st_error("Could not wait for event\n");
+		return 1;
+	}
+	ret = boottime->check_event(event_wait);
+	if (ret != EFI_NOT_READY) {
+		efi_st_error("Signaled state was not cleared.\n");
+		efi_st_printf("ret = %u\n", (unsigned int)ret);
+		return 1;
+	}
+	if (index != 0) {
+		efi_st_error("WaitForEvent returned wrong index\n");
+		return 1;
+	}
+	efi_st_printf("Counter with TPL level TPL_APPLICATION: %u\n", counter);
+	if (counter < 8 || counter > 12) {
+		efi_st_error("Incorrect timing of events\n");
+		return 1;
+	}
+	ret = boottime->set_timer(event_notify, EFI_TIMER_STOP, 0);
+	if (index != 0) {
+		efi_st_error("Could not cancel timer\n");
+		return 1;
+	}
+	/* Raise TPL level */
+	old_tpl = boottime->raise_tpl(TPL_CALLBACK);
+	if (old_tpl != TPL_APPLICATION) {
+		efi_st_error("Initial TPL level was not TPL_APPLICATION");
+		return 1;
+	}
+	/* Set 10 ms timer */
+	counter = 0;
+	ret = boottime->set_timer(event_notify, EFI_TIMER_PERIODIC, 100000);
+	if (index != 0) {
+		efi_st_error("Could not set timer\n");
+		return 1;
+	}
+	/* Set 100 ms timer */
+	ret = boottime->set_timer(event_wait, EFI_TIMER_RELATIVE, 1000000);
+	if (ret != EFI_SUCCESS) {
+		efi_st_error("Could not set timer\n");
+		return 1;
+	}
+	do {
+		ret = boottime->check_event(event_wait);
+	} while (ret == EFI_NOT_READY);
+	if (ret != EFI_SUCCESS) {
+		efi_st_error("Could not check event\n");
+		return 1;
+	}
+	efi_st_printf("Counter with TPL level TPL_CALLBACK: %u\n", counter);
+	if (counter != 0) {
+		efi_st_error("Suppressed timer fired\n");
+		return 1;
+	}
+	/* Set 1 ms timer */
+	ret = boottime->set_timer(event_wait, EFI_TIMER_RELATIVE, 1000);
+	if (ret != EFI_SUCCESS) {
+		efi_st_error("Could not set timer\n");
+		return 1;
+	}
+	/* Restore the old TPL level */
+	boottime->restore_tpl(TPL_APPLICATION);
+	ret = boottime->wait_for_event(1, &event_wait, &index);
+	if (ret != EFI_SUCCESS) {
+		efi_st_error("Could not wait for event\n");
+		return 1;
+	}
+	efi_st_printf("Counter with TPL level TPL_APPLICATION: %u\n", counter);
+	if (counter < 1) {
+		efi_st_error("Queued timer event did not fire\n");
+		return 1;
+	}
+	ret = boottime->set_timer(event_wait, EFI_TIMER_STOP, 0);
+	if (index != 0) {
+		efi_st_error("Could not cancel timer\n");
+		return 1;
+	}
+
+	return 0;
+}
+
+EFI_UNIT_TEST(tpl) = {
+	.name = "task priority levels",
+	.phase = EFI_EXECUTE_BEFORE_BOOTTIME_EXIT,
+	.setup = setup,
+	.execute = execute,
+	.teardown = teardown,
+};