blob: 6c4afb43f160f8b9807329bd4cfb4890f0f00367 [file] [log] [blame]
/* system clock support */
/*
* Copyright (c) 1997-2015 Wind River Systems, Inc.
*
* SPDX-License-Identifier: Apache-2.0
*/
#include <kernel_structs.h>
#include <toolchain.h>
#include <linker/sections.h>
#include <wait_q.h>
#include <drivers/system_timer.h>
#include <syscall_handler.h>
#ifdef CONFIG_SYS_CLOCK_EXISTS
#ifdef _NON_OPTIMIZED_TICKS_PER_SEC
#warning "non-optimized system clock frequency chosen: performance may suffer"
#endif
#endif
#ifdef CONFIG_SYS_CLOCK_EXISTS
int sys_clock_us_per_tick = 1000000 / sys_clock_ticks_per_sec;
int sys_clock_hw_cycles_per_tick =
CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC / sys_clock_ticks_per_sec;
#if defined(CONFIG_TIMER_READS_ITS_FREQUENCY_AT_RUNTIME)
int sys_clock_hw_cycles_per_sec = CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC;
#endif
#else
/* don't initialize to avoid division-by-zero error */
int sys_clock_us_per_tick;
int sys_clock_hw_cycles_per_tick;
#if defined(CONFIG_TIMER_READS_ITS_FREQUENCY_AT_RUNTIME)
int sys_clock_hw_cycles_per_sec;
#endif
#endif
/* updated by timer driver for tickless, stays at 1 for non-tickless */
s32_t _sys_idle_elapsed_ticks = 1;
volatile u64_t _sys_clock_tick_count;
#ifdef CONFIG_TICKLESS_KERNEL
/*
* If this flag is set, system clock will run continuously even if
* there are no timer events programmed. This allows using the
* system clock to track passage of time without interruption.
* To save power, this should be turned on only when required.
*/
int _sys_clock_always_on;
static u32_t next_ts;
#endif
/**
*
* @brief Return the lower part of the current system tick count
*
* @return the current system tick count
*
*/
u32_t _tick_get_32(void)
{
#ifdef CONFIG_TICKLESS_KERNEL
return (u32_t)_get_elapsed_clock_time();
#else
return (u32_t)_sys_clock_tick_count;
#endif
}
FUNC_ALIAS(_tick_get_32, sys_tick_get_32, u32_t);
u32_t _impl_k_uptime_get_32(void)
{
#ifdef CONFIG_TICKLESS_KERNEL
__ASSERT(_sys_clock_always_on,
"Call k_enable_sys_clock_always_on to use clock API");
#endif
return __ticks_to_ms(_tick_get_32());
}
#ifdef CONFIG_USERSPACE
Z_SYSCALL_HANDLER(k_uptime_get_32)
{
#ifdef CONFIG_TICKLESS_KERNEL
Z_OOPS(Z_SYSCALL_VERIFY(_sys_clock_always_on));
#endif
return _impl_k_uptime_get_32();
}
#endif
/**
*
* @brief Return the current system tick count
*
* @return the current system tick count
*
*/
s64_t _tick_get(void)
{
s64_t tmp_sys_clock_tick_count;
/*
* Lock the interrupts when reading _sys_clock_tick_count 64-bit
* variable. Some architectures (x86) do not handle 64-bit atomically,
* so we have to lock the timer interrupt that causes change of
* _sys_clock_tick_count
*/
unsigned int imask = irq_lock();
#ifdef CONFIG_TICKLESS_KERNEL
tmp_sys_clock_tick_count = _get_elapsed_clock_time();
#else
tmp_sys_clock_tick_count = _sys_clock_tick_count;
#endif
irq_unlock(imask);
return tmp_sys_clock_tick_count;
}
FUNC_ALIAS(_tick_get, sys_tick_get, s64_t);
s64_t _impl_k_uptime_get(void)
{
#ifdef CONFIG_TICKLESS_KERNEL
__ASSERT(_sys_clock_always_on,
"Call k_enable_sys_clock_always_on to use clock API");
#endif
return __ticks_to_ms(_tick_get());
}
#ifdef CONFIG_USERSPACE
Z_SYSCALL_HANDLER(k_uptime_get, ret_p)
{
u64_t *ret = (u64_t *)ret_p;
Z_OOPS(Z_SYSCALL_MEMORY_WRITE(ret, sizeof(*ret)));
*ret = _impl_k_uptime_get();
return 0;
}
#endif
s64_t k_uptime_delta(s64_t *reftime)
{
s64_t uptime, delta;
uptime = k_uptime_get();
delta = uptime - *reftime;
*reftime = uptime;
return delta;
}
u32_t k_uptime_delta_32(s64_t *reftime)
{
return (u32_t)k_uptime_delta(reftime);
}
/* handle the expired timeouts in the nano timeout queue */
#ifdef CONFIG_SYS_CLOCK_EXISTS
/*
* Handle timeouts by dequeuing the expired ones from _timeout_q and queue
* them on a local one, then doing the real handling from that queue. This
* allows going through the second queue without needing to have the
* interrupts locked since it is a local queue. Each expired timeout is marked
* as _EXPIRED so that an ISR preempting us and releasing an object on which
* a thread was timing out and expired will not give the object to that thread.
*
* Always called from interrupt level, and always only from the system clock
* interrupt.
*/
volatile int _handling_timeouts;
static inline void handle_timeouts(s32_t ticks)
{
sys_dlist_t expired;
unsigned int key;
/* init before locking interrupts */
sys_dlist_init(&expired);
key = irq_lock();
sys_dnode_t *next = sys_dlist_peek_head(&_timeout_q);
struct _timeout *timeout = (struct _timeout *)next;
K_DEBUG("head: %p, delta: %d\n",
timeout, timeout ? timeout->delta_ticks_from_prev : -2112);
if (!next) {
irq_unlock(key);
return;
}
/*
* Dequeue all expired timeouts from _timeout_q, relieving irq lock
* pressure between each of them, allowing handling of higher priority
* interrupts. We know that no new timeout will be prepended in front
* of a timeout which delta is 0, since timeouts of 0 ticks are
* prohibited.
*/
_handling_timeouts = 1;
while (next) {
/*
* In the case where ticks number is greater than the first
* timeout delta of the list, the lag produced by this initial
* difference must also be applied to others timeouts in list
* until it was entirely consumed.
*/
s32_t tmp = timeout->delta_ticks_from_prev;
if (timeout->delta_ticks_from_prev < ticks) {
timeout->delta_ticks_from_prev = 0;
} else {
timeout->delta_ticks_from_prev -= ticks;
}
ticks -= tmp;
next = sys_dlist_peek_next(&_timeout_q, next);
if (timeout->delta_ticks_from_prev == 0) {
sys_dnode_t *node = &timeout->node;
sys_dlist_remove(node);
/*
* Reverse the order that that were queued in the
* timeout_q: timeouts expiring on the same ticks are
* queued in the reverse order, time-wise, that they are
* added to shorten the amount of time with interrupts
* locked while walking the timeout_q. By reversing the
* order _again_ when building the expired queue, they
* end up being processed in the same order they were
* added, time-wise.
*/
sys_dlist_prepend(&expired, node);
timeout->delta_ticks_from_prev = _EXPIRED;
} else if (ticks <= 0) {
break;
}
irq_unlock(key);
key = irq_lock();
timeout = (struct _timeout *)next;
}
irq_unlock(key);
_handle_expired_timeouts(&expired);
_handling_timeouts = 0;
}
#else
#define handle_timeouts(ticks) do { } while ((0))
#endif
#ifdef CONFIG_TIMESLICING
s32_t _time_slice_elapsed;
s32_t _time_slice_duration = CONFIG_TIMESLICE_SIZE;
int _time_slice_prio_ceiling = CONFIG_TIMESLICE_PRIORITY;
/*
* Always called from interrupt level, and always only from the system clock
* interrupt, thus:
* - _current does not have to be protected, since it only changes at thread
* level or when exiting a non-nested interrupt
* - _time_slice_elapsed does not have to be protected, since it can only change
* in this function and at thread level
* - _time_slice_duration does not have to be protected, since it can only
* change at thread level
*/
static void handle_time_slicing(s32_t ticks)
{
#ifdef CONFIG_TICKLESS_KERNEL
next_ts = 0;
#endif
if (!_is_thread_time_slicing(_current)) {
return;
}
_time_slice_elapsed += __ticks_to_ms(ticks);
if (_time_slice_elapsed >= _time_slice_duration) {
unsigned int key;
_time_slice_elapsed = 0;
key = irq_lock();
_move_thread_to_end_of_prio_q(_current);
irq_unlock(key);
}
#ifdef CONFIG_TICKLESS_KERNEL
next_ts =
_ms_to_ticks(_time_slice_duration - _time_slice_elapsed);
#endif
}
#else
#define handle_time_slicing(ticks) do { } while (0)
#endif
/**
*
* @brief Announce a tick to the kernel
*
* This function is only to be called by the system clock timer driver when a
* tick is to be announced to the kernel. It takes care of dequeuing the
* timers that have expired and wake up the threads pending on them.
*
* @return N/A
*/
void _nano_sys_clock_tick_announce(s32_t ticks)
{
#ifdef CONFIG_SMP
/* sys_clock timekeeping happens only on the main CPU */
if (_arch_curr_cpu()->id) {
return;
}
#endif
#ifndef CONFIG_TICKLESS_KERNEL
unsigned int key;
K_DEBUG("ticks: %d\n", ticks);
/* 64-bit value, ensure atomic access with irq lock */
key = irq_lock();
_sys_clock_tick_count += ticks;
irq_unlock(key);
#endif
handle_timeouts(ticks);
/* time slicing is basically handled like just yet another timeout */
handle_time_slicing(ticks);
#ifdef CONFIG_TICKLESS_KERNEL
u32_t next_to = _get_next_timeout_expiry();
next_to = next_to == K_FOREVER ? 0 : next_to;
next_to = !next_to || (next_ts
&& next_to) > next_ts ? next_ts : next_to;
u32_t remaining = _get_remaining_program_time();
if ((!remaining && next_to) || (next_to < remaining)) {
/* Clears current program if next_to = 0 and remaining > 0 */
_set_time(next_to);
}
#endif
}