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