tests/benchmarks/latency_measure/src/int_to_thread.c

/*
 * Copyright (c) 2012-2014 Wind River Systems, Inc.
 * Copyright (c) 2017 Intel Corporation.
 *
 * SPDX-License-Identifier: Apache-2.0
 */

/**
 * @file
 *
 * @brief Measure time from ISR back to interrupted thread
 *
 * This file contains test that measures time to switch from the interrupt
 * handler back to the interrupted thread.
 */

#include "utils.h"
#include "timing_info.h"

#include <arch/cpu.h>
#include <irq_offload.h>

static volatile int flag_var;

static u32_t timestamp_start;
static u32_t timestamp_end;

/**
 *
 * @brief Test ISR used to measure best case interrupt latency
 *
 * The interrupt handler gets the second timestamp.
 *
 * @return N/A
 */
static void latency_test_isr(void *unused)
{
	ARG_UNUSED(unused);

	flag_var = 1;

	TIMING_INFO_PRE_READ();
	timestamp_start = TIMING_INFO_OS_GET_TIME();
}

/**
 *
 * @brief Interrupt preparation function
 *
 * Function makes all the test preparations: registers the interrupt handler,
 * gets the first timestamp and invokes the software interrupt.
 *
 * @return N/A
 */
static void make_int(void)
{
	flag_var = 0;
	irq_offload(latency_test_isr, NULL);
	if (flag_var != 1) {
		PRINT_FORMAT(" Flag variable has not changed. FAILED\n");
	} else {
		TIMING_INFO_PRE_READ();
		timestamp_end = TIMING_INFO_OS_GET_TIME();
	}
}

/**
 *
 * @brief The test main function
 *
 * @return 0 on success
 */
int int_to_thread(void)
{
	u32_t diff;

	PRINT_FORMAT(" 1 - Measure time to switch from ISR back to"
		     " interrupted thread");
	benchmark_timer_start();
	TICK_SYNCH();
	make_int();
	if (flag_var == 1) {
		diff = TIMING_INFO_GET_DELTA(timestamp_start, timestamp_end);
		PRINT_FORMAT(" switching time is %u tcs = %u nsec",
			     diff, CYCLES_TO_NS(diff));
	}
	benchmark_timer_stop();
	return 0;
}