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/* Copyright (c) 2022 Intel corporation
* SPDX-License-Identifier: Apache-2.0
*/
#include <zephyr/kernel.h>
#include <zephyr/kernel_structs.h>
#include <zephyr/kernel/smp.h>
#include <zephyr/spinlock.h>
#include <kswap.h>
#include <kernel_internal.h>
static atomic_t global_lock;
/**
* Flag to tell recently powered up CPU to start
* initialization routine.
*
* 0 to tell powered up CPU to wait.
* 1 to tell powered up CPU to continue initialization.
*/
static atomic_t cpu_start_flag;
/**
* Flag to tell caller that the target CPU is now
* powered up and ready to be initialized.
*
* 0 if target CPU is not yet ready.
* 1 if target CPU has powered up and ready to be initialized.
*/
static atomic_t ready_flag;
/**
* Struct holding the function to be called before handing off
* to schedule and its argument.
*/
static struct cpu_start_cb {
/**
* Function to be called before handing off to scheduler.
* Can be NULL.
*/
smp_init_fn fn;
/** Argument to @ref cpu_start_fn.fn. */
void *arg;
/** Invoke scheduler after CPU has started if true. */
bool invoke_sched;
#ifdef CONFIG_SYS_CLOCK_EXISTS
/** True if smp_timer_init() needs to be called. */
bool reinit_timer;
#endif /* CONFIG_SYS_CLOCK_EXISTS */
} cpu_start_fn;
static struct k_spinlock cpu_start_lock;
unsigned int z_smp_global_lock(void)
{
unsigned int key = arch_irq_lock();
if (!_current->base.global_lock_count) {
while (!atomic_cas(&global_lock, 0, 1)) {
arch_spin_relax();
}
}
_current->base.global_lock_count++;
return key;
}
void z_smp_global_unlock(unsigned int key)
{
if (_current->base.global_lock_count != 0U) {
_current->base.global_lock_count--;
if (!_current->base.global_lock_count) {
(void)atomic_clear(&global_lock);
}
}
arch_irq_unlock(key);
}
/* Called from within z_swap(), so assumes lock already held */
void z_smp_release_global_lock(struct k_thread *thread)
{
if (!thread->base.global_lock_count) {
(void)atomic_clear(&global_lock);
}
}
/* Tiny delay that relaxes bus traffic to avoid spamming a shared
* memory bus looking at an atomic variable
*/
static inline void local_delay(void)
{
for (volatile int i = 0; i < 1000; i++) {
}
}
static void wait_for_start_signal(atomic_t *start_flag)
{
/* Wait for the signal to begin scheduling */
while (!atomic_get(start_flag)) {
local_delay();
}
}
static inline void smp_init_top(void *arg)
{
struct cpu_start_cb csc = arg ? *(struct cpu_start_cb *)arg : (struct cpu_start_cb){0};
/* Let start_cpu() know that this CPU has powered up. */
(void)atomic_set(&ready_flag, 1);
/* Wait for the CPU start caller to signal that
* we can start initialization.
*/
wait_for_start_signal(&cpu_start_flag);
if ((arg == NULL) || csc.invoke_sched) {
/* Initialize the dummy thread struct so that
* the scheduler can schedule actual threads to run.
*/
z_dummy_thread_init(&_thread_dummy);
}
#ifdef CONFIG_SYS_CLOCK_EXISTS
if ((arg == NULL) || csc.reinit_timer) {
smp_timer_init();
}
#endif /* CONFIG_SYS_CLOCK_EXISTS */
/* Do additional initialization steps if needed. */
if (csc.fn != NULL) {
csc.fn(csc.arg);
}
if ((arg != NULL) && !csc.invoke_sched) {
/* Don't invoke scheduler. */
return;
}
/* Let scheduler decide what thread to run next. */
z_swap_unlocked();
CODE_UNREACHABLE; /* LCOV_EXCL_LINE */
}
static void start_cpu(int id, struct cpu_start_cb *csc)
{
/* Clear the ready flag so the newly powered up CPU can
* signal that it has powered up.
*/
(void)atomic_clear(&ready_flag);
/* Power up the CPU */
arch_cpu_start(id, z_interrupt_stacks[id], CONFIG_ISR_STACK_SIZE,
smp_init_top, csc);
/* Wait until the newly powered up CPU to signal that
* it has powered up.
*/
while (!atomic_get(&ready_flag)) {
local_delay();
}
}
void k_smp_cpu_start(int id, smp_init_fn fn, void *arg)
{
k_spinlock_key_t key = k_spin_lock(&cpu_start_lock);
cpu_start_fn.fn = fn;
cpu_start_fn.arg = arg;
cpu_start_fn.invoke_sched = true;
#ifdef CONFIG_SYS_CLOCK_EXISTS
cpu_start_fn.reinit_timer = true;
#endif /* CONFIG_SYS_CLOCK_EXISTS */
/* We are only starting one CPU so we do not need to synchronize
* across all CPUs using the start_flag. So just set it to 1.
*/
(void)atomic_set(&cpu_start_flag, 1); /* async, don't care */
/* Initialize various CPU structs related to this CPU. */
z_init_cpu(id);
/* Start the CPU! */
start_cpu(id, &cpu_start_fn);
k_spin_unlock(&cpu_start_lock, key);
}
void k_smp_cpu_resume(int id, smp_init_fn fn, void *arg,
bool reinit_timer, bool invoke_sched)
{
k_spinlock_key_t key = k_spin_lock(&cpu_start_lock);
cpu_start_fn.fn = fn;
cpu_start_fn.arg = arg;
cpu_start_fn.invoke_sched = invoke_sched;
#ifdef CONFIG_SYS_CLOCK_EXISTS
cpu_start_fn.reinit_timer = reinit_timer;
#else
ARG_UNUSED(reinit_timer);
#endif /* CONFIG_SYS_CLOCK_EXISTS */
/* We are only starting one CPU so we do not need to synchronize
* across all CPUs using the start_flag. So just set it to 1.
*/
(void)atomic_set(&cpu_start_flag, 1);
/* Start the CPU! */
start_cpu(id, &cpu_start_fn);
k_spin_unlock(&cpu_start_lock, key);
}
void z_smp_init(void)
{
/* We are powering up all CPUs and we want to synchronize their
* entry into scheduler. So set the start flag to 0 here.
*/
(void)atomic_clear(&cpu_start_flag);
/* Just start CPUs one by one. */
unsigned int num_cpus = arch_num_cpus();
for (int i = 1; i < num_cpus; i++) {
z_init_cpu(i);
start_cpu(i, NULL);
}
/* Let loose those CPUs so they can start scheduling
* threads to run.
*/
(void)atomic_set(&cpu_start_flag, 1);
}
bool z_smp_cpu_mobile(void)
{
unsigned int k = arch_irq_lock();
bool pinned = arch_is_in_isr() || !arch_irq_unlocked(k);
arch_irq_unlock(k);
return !pinned;
}