The Fuchsia Authors
131 linhas
3.0 KiB
C
131 linhas
3.0 KiB
C
// Copyright 2016 The Fuchsia Authors
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// Copyright (c) 2012-2014 Travis Geiselbrecht
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//
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// Use of this source code is governed by a MIT-style
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// license that can be found in the LICENSE file or at
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// https://opensource.org/licenses/MIT
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/*
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* Generic systick timer support for providing system time (current_time(), current_time_hires()),
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* and a monotonic timer for the kernel.
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*/
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#include <sys/types.h>
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#include <string.h>
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#include <stdlib.h>
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#include <debug.h>
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#include <assert.h>
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#include <trace.h>
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#include <err.h>
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#include <kernel/thread.h>
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#include <arch/arm.h>
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#include <arch/arm/cm.h>
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#include <platform.h>
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#include <platform/timer.h>
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#define LOCAL_TRACE 0
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static volatile uint64_t ticks;
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static uint32_t tick_rate = 0;
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static uint32_t tick_rate_mhz = 0;
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static lk_time_t tick_interval_ms;
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static lk_bigtime_t tick_interval_us;
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static platform_timer_callback cb;
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static void *cb_args;
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static void arm_cm_systick_set_periodic(lk_time_t period)
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{
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LTRACEF("clk_freq %u, period %u\n", tick_rate, (uint)period);
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uint32_t ticks = tick_rate / (1000 / period);
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LTRACEF("ticks %d\n", ticks);
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SysTick->LOAD = (ticks & SysTick_LOAD_RELOAD_Msk) - 1;
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SysTick->VAL = 0;
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SysTick->CTRL = SysTick_CTRL_CLKSOURCE_Msk | SysTick_CTRL_TICKINT_Msk | SysTick_CTRL_ENABLE_Msk;
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}
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static void arm_cm_systick_cancel_periodic(void)
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{
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SysTick->CTRL &= ~SysTick_CTRL_ENABLE_Msk;
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}
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/* main systick irq handler */
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void _systick(void)
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{
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ticks++;
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arm_cm_irq_entry();
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bool resched = false;
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if (cb) {
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lk_time_t now = current_time();
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if (cb(cb_args, now) == INT_RESCHEDULE)
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resched = true;
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}
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arm_cm_irq_exit(resched);
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}
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status_t platform_set_periodic_timer(platform_timer_callback callback, void *arg, lk_time_t interval)
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{
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LTRACEF("callback %p, arg %p, interval %u\n", callback, arg, interval);
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DEBUG_ASSERT(tick_rate != 0 && tick_rate_mhz != 0);
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cb = callback;
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cb_args = arg;
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tick_interval_ms = interval;
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tick_interval_us = interval * 1000;
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arm_cm_systick_set_periodic(interval);
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return NO_ERROR;
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}
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lk_time_t current_time(void)
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{
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uint32_t reload = SysTick->LOAD & SysTick_LOAD_RELOAD_Msk;
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uint64_t t;
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uint32_t delta;
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do {
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t = ticks;
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delta = (volatile uint32_t)SysTick->VAL;
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DMB;
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} while (ticks != t);
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/* convert ticks to msec */
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delta = (reload - delta) / (tick_rate_mhz * 1000);
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lk_time_t res = (t * tick_interval_ms) + delta;
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return res;
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}
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lk_bigtime_t current_time_hires(void)
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{
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uint32_t reload = SysTick->LOAD & SysTick_LOAD_RELOAD_Msk;
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uint64_t t;
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uint32_t delta;
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do {
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t = ticks;
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delta = (volatile uint32_t)SysTick->VAL;
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DMB;
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} while (ticks != t);
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/* convert ticks to usec */
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delta = (reload - delta) / tick_rate_mhz;
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lk_bigtime_t res = (t * tick_interval_us) + delta;
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return res;
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}
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void arm_cm_systick_init(uint32_t mhz)
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{
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tick_rate = mhz;
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tick_rate_mhz = mhz / 1000000;
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}
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