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/* system clock support */
/*
* Copyright (c) 1997-2015 Wind River Systems, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <kernel_structs.h>
#include <toolchain.h>
#include <sections.h>
#include <wait_q.h>
#include <drivers/system_timer.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 */
int32_t _sys_idle_elapsed_ticks = 1;
int64_t _sys_clock_tick_count;
/**
*
* @brief Return the lower part of the current system tick count
*
* @return the current system tick count
*
*/
uint32_t _tick_get_32(void)
{
return (uint32_t)_sys_clock_tick_count;
}
FUNC_ALIAS(_tick_get_32, sys_tick_get_32, uint32_t);
uint32_t k_uptime_get_32(void)
{
return __ticks_to_ms(_tick_get_32());
}
/**
*
* @brief Return the current system tick count
*
* @return the current system tick count
*
*/
int64_t _tick_get(void)
{
int64_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();
tmp_sys_clock_tick_count = _sys_clock_tick_count;
irq_unlock(imask);
return tmp_sys_clock_tick_count;
}
FUNC_ALIAS(_tick_get, sys_tick_get, int64_t);
int64_t k_uptime_get(void)
{
return __ticks_to_ms(_tick_get());
}
/**
*
* @brief Return number of ticks since a reference time
*
* This function is meant to be used in contained fragments of code. The first
* call to it in a particular code fragment fills in a reference time variable
* which then gets passed and updated every time the function is called. From
* the second call on, the delta between the value passed to it and the current
* tick count is the return value. Since the first call is meant to only fill in
* the reference time, its return value should be discarded.
*
* Since a code fragment that wants to use sys_tick_delta() passes in its
* own reference time variable, multiple code fragments can make use of this
* function concurrently.
*
* e.g.
* uint64_t reftime;
* (void) sys_tick_delta(&reftime); /# prime it #/
* [do stuff]
* x = sys_tick_delta(&reftime); /# how long since priming #/
* [do more stuff]
* y = sys_tick_delta(&reftime); /# how long since [do stuff] #/
*
* @return tick count since reference time; undefined for first invocation
*
* NOTE: We use inline function for both 64-bit and 32-bit functions.
* Compiler optimizes out 64-bit result handling in 32-bit version.
*/
static ALWAYS_INLINE int64_t _nano_tick_delta(int64_t *reftime)
{
int64_t delta;
int64_t saved;
/*
* 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();
saved = _sys_clock_tick_count;
irq_unlock(imask);
delta = saved - (*reftime);
*reftime = saved;
return delta;
}
/**
*
* @brief Return number of ticks since a reference time
*
* @return tick count since reference time; undefined for first invocation
*/
int64_t sys_tick_delta(int64_t *reftime)
{
return _nano_tick_delta(reftime);
}
uint32_t sys_tick_delta_32(int64_t *reftime)
{
return (uint32_t)_nano_tick_delta(reftime);
}
int64_t k_uptime_delta(int64_t *reftime)
{
int64_t uptime, delta;
uptime = k_uptime_get();
delta = uptime - *reftime;
*reftime = uptime;
return delta;
}
uint32_t k_uptime_delta_32(int64_t *reftime)
{
return (uint32_t)k_uptime_delta(reftime);
}
/* handle the expired timeouts in the nano timeout queue */
#ifdef CONFIG_SYS_CLOCK_EXISTS
#include <wait_q.h>
/*
* 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 expiredwill 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(int32_t ticks)
{
sys_dlist_t expired;
unsigned int key;
/* init before locking interrupts */
sys_dlist_init(&expired);
key = irq_lock();
struct _timeout *head =
(struct _timeout *)sys_dlist_peek_head(&_timeout_q);
K_DEBUG("head: %p, delta: %d\n",
head, head ? head->delta_ticks_from_prev : -2112);
if (!head) {
irq_unlock(key);
return;
}
head->delta_ticks_from_prev -= ticks;
/*
* 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.
*/
sys_dnode_t *next = &head->node;
struct _timeout *timeout = (struct _timeout *)next;
_handling_timeouts = 1;
while (timeout && timeout->delta_ticks_from_prev == 0) {
sys_dlist_remove(next);
sys_dlist_append(&expired, next);
timeout->delta_ticks_from_prev = _EXPIRED;
irq_unlock(key);
key = irq_lock();
next = sys_dlist_peek_head(&_timeout_q);
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
int32_t _time_slice_elapsed;
int32_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(int32_t ticks)
{
if (_time_slice_duration == 0) {
return;
}
if (_is_prio_higher(_current->base.prio, _time_slice_prio_ceiling)) {
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);
}
}
#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(int32_t ticks)
{
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);
handle_timeouts(ticks);
/* time slicing is basically handled like just yet another timeout */
handle_time_slicing(ticks);
}