/*
 * Copyright (c) 2019 Nordic Semiconductor ASA.
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <zephyr/ztest.h>
#include <zephyr/arch/cpu.h>
#include <zephyr/arch/arm/aarch32/cortex_m/cmsis.h>
#include <zephyr/sys/barrier.h>

static volatile int test_flag;

void arm_zero_latency_isr_handler(const void *args)
{
	ARG_UNUSED(args);

	test_flag = 1;
}

ZTEST(arm_irq_advanced_features, test_arm_zero_latency_irqs)
{

	if (!IS_ENABLED(CONFIG_ZERO_LATENCY_IRQS)) {
		TC_PRINT("Skipped (Cortex-M Mainline only)\n");

		return;
	}

	/* Determine an NVIC IRQ line that is not currently in use. */
	int i, key;
	int init_flag, post_flag;

	init_flag = test_flag;

	zassert_false(init_flag, "Test flag not initialized to zero\n");

	for (i = CONFIG_NUM_IRQS - 1; i >= 0; i--) {
		if (NVIC_GetEnableIRQ(i) == 0) {
			/*
			 * Interrupts configured statically with IRQ_CONNECT(.)
			 * are automatically enabled. NVIC_GetEnableIRQ()
			 * returning false, here, implies that the IRQ line is
			 * either not implemented or it is not enabled, thus,
			 * currently not in use by Zephyr.
			 */

			/* Set the NVIC line to pending. */
			NVIC_SetPendingIRQ(i);

			if (NVIC_GetPendingIRQ(i)) {
				/*
				 * If the NVIC line is pending, it is
				 * guaranteed that it is implemented; clear the
				 * line.
				 */
				NVIC_ClearPendingIRQ(i);

				if (!NVIC_GetPendingIRQ(i)) {
					/*
					 * If the NVIC line can be successfully
					 * un-pended, it is guaranteed that it
					 * can be used for software interrupt
					 * triggering. Return the NVIC line
					 * number.
					 */
					break;
				}
			}
		}
	}

	zassert_true(i >= 0,
		"No available IRQ line to configure as zero-latency\n");

	TC_PRINT("Available IRQ line: %u\n", i);

	/* Configure the available IRQ line as zero-latency. */

	arch_irq_connect_dynamic(i, 0 /* Unused */,
		arm_zero_latency_isr_handler,
		NULL,
		IRQ_ZERO_LATENCY);

	NVIC_ClearPendingIRQ(i);
	NVIC_EnableIRQ(i);

	/* Lock interrupts */
	key = irq_lock();

	/* Set the zero-latency IRQ to pending state. */
	NVIC_SetPendingIRQ(i);

	/*
	 * Instruction barriers to make sure the NVIC IRQ is
	 * set to pending state before 'test_flag' is checked.
	 */
	barrier_dsync_fence_full();
	barrier_isync_fence_full();

	/* Confirm test flag is set by the zero-latency ISR handler. */
	post_flag = test_flag;
	zassert_true(post_flag == 1, "Test flag not set by ISR\n");

	irq_unlock(key);
}

/**
 * @}
 */