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