blob: a601c76bc34bbe6e7b241fab7ddb9566bf947496 [file] [log] [blame]
/*
* Copyright (c) 2016 Wind River Systems, Inc.
*
* SPDX-License-Identifier: Apache-2.0
*/
#include <kernel.h>
#include <toolchain.h>
#include <linker/sections.h>
#include <drivers/timer/system_timer.h>
#include <wait_q.h>
#include <pm/pm.h>
#include <stdbool.h>
#include <logging/log.h>
#include <ksched.h>
#include <kswap.h>
LOG_MODULE_DECLARE(os, CONFIG_KERNEL_LOG_LEVEL);
/**
* @brief Indicate that kernel is idling in tickless mode
*
* Sets the kernel data structure idle field to either a positive value or
* K_FOREVER.
*/
static void pm_save_idle(void)
{
#ifdef CONFIG_PM
int32_t ticks = z_get_next_timeout_expiry();
_kernel.idle = ticks;
/*
* Call the suspend hook function of the soc interface to allow
* entry into a low power state. The function returns
* PM_STATE_ACTIVE if low power state was not entered, in which
* case, kernel does normal idle processing.
*
* This function is entered with interrupts disabled. If a low power
* state was entered, then the hook function should enable inerrupts
* before exiting. This is because the kernel does not do its own idle
* processing in those cases i.e. skips k_cpu_idle(). The kernel's
* idle processing re-enables interrupts which is essential for
* the kernel's scheduling logic.
*/
if (pm_system_suspend(ticks) == PM_STATE_ACTIVE) {
k_cpu_idle();
}
#endif
}
void z_pm_save_idle_exit(int32_t ticks)
{
#ifdef CONFIG_PM
/* Some CPU low power states require notification at the ISR
* to allow any operations that needs to be done before kernel
* switches task or processes nested interrupts.
* This can be simply ignored if not required.
*/
pm_system_resume();
#endif /* CONFIG_PM */
sys_clock_idle_exit();
}
void idle(void *unused1, void *unused2, void *unused3)
{
ARG_UNUSED(unused1);
ARG_UNUSED(unused2);
ARG_UNUSED(unused3);
__ASSERT_NO_MSG(_current->base.prio >= 0);
while (true) {
/* SMP systems without a working IPI can't
* actual enter an idle state, because they
* can't be notified of scheduler changes
* (i.e. threads they should run). They just
* spin in a yield loop. This is intended as
* a fallback configuration for new platform
* bringup.
*/
if ((IS_ENABLED(CONFIG_SMP)) &&
!(IS_ENABLED(CONFIG_SCHED_IPI_SUPPORTED))) {
k_busy_wait(100);
k_yield();
continue;
}
/* Note weird API: k_cpu_idle() is called with local
* CPU interrupts masked, and returns with them
* unmasked. It does not take a spinlock or other
* higher level construct.
*/
(void) arch_irq_lock();
if (IS_ENABLED(CONFIG_PM)) {
pm_save_idle();
} else {
k_cpu_idle();
}
#if !defined(CONFIG_PREEMPT_ENABLED)
# if !defined(CONFIG_USE_SWITCH) || defined(CONFIG_SPARC)
/* A legacy mess: the idle thread is by definition
* preemptible as far as the modern scheduler is
* concerned, but older platforms use
* CONFIG_PREEMPT_ENABLED=n as an optimization hint
* that interrupt exit always returns to the
* interrupted context. So in that setup we need to
* explicitly yield in the idle thread otherwise
* nothing else will run once it starts.
*/
if (_kernel.ready_q.cache != _current) {
z_swap_unlocked();
}
# endif
#endif
}
}