/*
 * Copyright (c) 2010-2015 Wind River Systems, Inc.
 * Copyright (c) 2017 Oticon A/S
 *
 * SPDX-License-Identifier: Apache-2.0
 */

/**
 * @file
 * @brief Kernel swapper code for POSIX
 *
 * This module implements the arch_swap() routine for the POSIX architecture.
 *
 */

#include <zephyr/kernel.h>
#include <zephyr/kernel_structs.h>
#include "posix_core.h"
#include <zephyr/irq.h>
#include "kswap.h"
#include <zephyr/pm/pm.h>

int arch_swap(unsigned int key)
{
	/*
	 * struct k_thread * _current is the currently running thread
	 * struct k_thread * _kernel.ready_q.cache contains the next thread to
	 * run (cannot be NULL)
	 *
	 * Here a "real" arch would save all processor registers, stack pointer
	 * and so forth.  But we do not need to do so because we use posix
	 * threads => those are all nicely kept by the native OS kernel
	 */
#if CONFIG_INSTRUMENT_THREAD_SWITCHING
	z_thread_mark_switched_out();
#endif
	_current->callee_saved.key = key;
	_current->callee_saved.retval = -EAGAIN;

	/* retval may be modified with a call to
	 * arch_thread_return_value_set()
	 */

	posix_thread_status_t *ready_thread_ptr =
		(posix_thread_status_t *)
		_kernel.ready_q.cache->callee_saved.thread_status;

	posix_thread_status_t *this_thread_ptr  =
		(posix_thread_status_t *)
		_current->callee_saved.thread_status;


	_current = _kernel.ready_q.cache;
#if CONFIG_INSTRUMENT_THREAD_SWITCHING
	z_thread_mark_switched_in();
#endif

	/*
	 * Here a "real" arch would load all processor registers for the thread
	 * to run. In this arch case, we just block this thread until allowed
	 * to run later, and signal to whomever is allowed to run to
	 * continue.
	 */
	posix_swap(ready_thread_ptr->thread_idx,
		this_thread_ptr->thread_idx);

	/* When we continue, _kernel->current points back to this thread */

	irq_unlock(_current->callee_saved.key);

	return _current->callee_saved.retval;
}


#ifdef CONFIG_ARCH_HAS_CUSTOM_SWAP_TO_MAIN
/* This is just a version of arch_swap() in which we do not save anything
 * about the current thread.
 *
 * Note that we will never come back to this thread: posix_main_thread_start()
 * does never return.
 */
void arch_switch_to_main_thread(struct k_thread *main_thread, char *stack_ptr,
				k_thread_entry_t _main)
{
	ARG_UNUSED(stack_ptr);
	ARG_UNUSED(_main);

	posix_thread_status_t *ready_thread_ptr =
			(posix_thread_status_t *)
			_kernel.ready_q.cache->callee_saved.thread_status;

#ifdef CONFIG_INSTRUMENT_THREAD_SWITCHING
	z_thread_mark_switched_out();
#endif

	_current = _kernel.ready_q.cache;

#ifdef CONFIG_INSTRUMENT_THREAD_SWITCHING
	z_thread_mark_switched_in();
#endif

	posix_main_thread_start(ready_thread_ptr->thread_idx);
} /* LCOV_EXCL_LINE */
#endif

#ifdef CONFIG_PM
/**
 * If the kernel is in idle mode, take it out
 */
void posix_irq_check_idle_exit(void)
{
	if (_kernel.idle) {
		_kernel.idle = 0;
		z_pm_save_idle_exit();
	}
}
#endif