377 lines
9.6 KiB
C
377 lines
9.6 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 <sections.h>
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#include <wait_q.h>
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#include <drivers/system_timer.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 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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/**
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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 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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/**
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*
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* @brief Return number of ticks since a reference time
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*
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* This function is meant to be used in contained fragments of code. The first
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* call to it in a particular code fragment fills in a reference time variable
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* which then gets passed and updated every time the function is called. From
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* the second call on, the delta between the value passed to it and the current
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* tick count is the return value. Since the first call is meant to only fill in
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* the reference time, its return value should be discarded.
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*
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* Since a code fragment that wants to use sys_tick_delta() passes in its
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* own reference time variable, multiple code fragments can make use of this
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* function concurrently.
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*
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* e.g.
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* u64_t reftime;
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* (void) sys_tick_delta(&reftime); /# prime it #/
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* [do stuff]
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* x = sys_tick_delta(&reftime); /# how long since priming #/
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* [do more stuff]
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* y = sys_tick_delta(&reftime); /# how long since [do stuff] #/
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*
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* @return tick count since reference time; undefined for first invocation
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*
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* NOTE: We use inline function for both 64-bit and 32-bit functions.
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* Compiler optimizes out 64-bit result handling in 32-bit version.
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*/
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static ALWAYS_INLINE s64_t _nano_tick_delta(s64_t *reftime)
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{
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s64_t delta;
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s64_t saved;
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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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saved = _get_elapsed_clock_time();
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#else
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saved = _sys_clock_tick_count;
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#endif
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irq_unlock(imask);
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delta = saved - (*reftime);
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*reftime = saved;
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return delta;
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}
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/**
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*
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* @brief Return number of ticks since a reference time
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*
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* @return tick count since reference time; undefined for first invocation
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*/
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s64_t sys_tick_delta(s64_t *reftime)
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{
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return _nano_tick_delta(reftime);
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}
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u32_t sys_tick_delta_32(s64_t *reftime)
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{
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return (u32_t)_nano_tick_delta(reftime);
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}
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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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#include <wait_q.h>
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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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volatile int _handling_timeouts;
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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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struct _timeout *head =
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(struct _timeout *)sys_dlist_peek_head(&_timeout_q);
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K_DEBUG("head: %p, delta: %d\n",
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head, head ? head->delta_ticks_from_prev : -2112);
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if (!head) {
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irq_unlock(key);
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return;
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}
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head->delta_ticks_from_prev -= ticks;
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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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sys_dnode_t *next = &head->node;
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struct _timeout *timeout = (struct _timeout *)next;
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_handling_timeouts = 1;
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while (timeout && timeout->delta_ticks_from_prev == 0) {
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sys_dlist_remove(next);
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/*
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* Reverse the order that that were queued in the timeout_q:
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* timeouts expiring on the same ticks are queued in the
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* reverse order, time-wise, that they are added to shorten the
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* amount of time with interrupts locked while walking the
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* timeout_q. By reversing the order _again_ when building the
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* expired queue, they end up being processed in the same order
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* they were added, time-wise.
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*/
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sys_dlist_prepend(&expired, next);
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timeout->delta_ticks_from_prev = _EXPIRED;
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irq_unlock(key);
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key = irq_lock();
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next = sys_dlist_peek_head(&_timeout_q);
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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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_handling_timeouts = 0;
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}
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#else
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#define handle_timeouts(ticks) do { } while ((0))
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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 = CONFIG_TIMESLICE_SIZE;
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int _time_slice_prio_ceiling = CONFIG_TIMESLICE_PRIORITY;
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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_to_ms(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 =
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_ms_to_ticks(_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 (0)
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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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#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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