157 lines
3.8 KiB
C
157 lines
3.8 KiB
C
/*
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* Timer and PWM functions for STM32F042 boards.
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* Also replacement for 'generic/armcm_timer.c', which not compatible
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* with Cortex-M0 CPUs
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*
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* Copyright (C) 2019 Eug Krashtan <eug.krashtan@gmail.com>
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* This file may be distributed under the terms of the GNU GPLv3 license.
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*
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* DO NOT USE HAL! (Timer HAL extremely fat)
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*/
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#include "autoconf.h" // CONFIG_CLOCK_FREQ
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#include "board/internal.h" // SysTick
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#include "board/irq.h" // irq_disable
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#include "stm32f0xx.h"
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#include "log.h"
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#include "sched.h" // DECL_INIT
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#include "command.h" // shutdown
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DECL_CONSTANT("CLOCK_FREQ", CONFIG_CLOCK_FREQ);
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// Return the number of clock ticks for a given number of microseconds
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uint32_t
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timer_from_us(uint32_t us)
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{
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return us * (CONFIG_CLOCK_FREQ / 1000000);
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}
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// Return true if time1 is before time2. Always use this function to
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// compare times as regular C comparisons can fail if the counter
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// rolls over.
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uint8_t
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timer_is_before(uint32_t time1, uint32_t time2)
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{
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return (int32_t)(time1 - time2) < 0;
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}
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// Set the next irq time
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static void
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timer_set_diff(uint32_t value)
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{
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SysTick->LOAD = value;
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SysTick->VAL = 0;
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SysTick->LOAD = 0;
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}
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// Activate timer dispatch as soon as possible
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void
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timer_kick(void)
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{
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SysTick->LOAD = 0;
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SysTick->VAL = 0;
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SCB->ICSR = SCB_ICSR_PENDSTSET_Msk;
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}
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/*
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* TIM2 (32bit) used instead of DWT->CYCCNT in original variant
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*/
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void TimerInit(void)
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{
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RCC->APB1ENR |= RCC_APB1ENR_TIM2EN;
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TIM2->PSC = 0;
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//TIM2->ARR = 0xFFFFFFFF; reset value
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TIM2->DIER = TIM_DIER_UIE;
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TIM2->CR1 = TIM_CR1_CEN;
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NVIC_EnableIRQ(TIM2_IRQn);
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// Enable SysTick
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irqstatus_t flag = irq_save();
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NVIC_SetPriority(SysTick_IRQn, 2);
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SysTick->CTRL = (SysTick_CTRL_CLKSOURCE_Msk | SysTick_CTRL_TICKINT_Msk
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| SysTick_CTRL_ENABLE_Msk);
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timer_kick();
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irq_restore(flag);
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}
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DECL_INIT(TimerInit);
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uint32_t
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timer_read_time(void)
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{
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return TIM2->CNT;
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}
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static uint32_t timer_repeat_until;
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#define TIMER_IDLE_REPEAT_TICKS timer_from_us(500)
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#define TIMER_REPEAT_TICKS timer_from_us(100)
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#define TIMER_MIN_TRY_TICKS timer_from_us(2)
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#define TIMER_DEFER_REPEAT_TICKS timer_from_us(5)
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// Invoke timers
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static uint32_t
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timer_dispatch_many(void)
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{
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uint32_t tru = timer_repeat_until;
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for (;;) {
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// Run the next software timer
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uint32_t next = sched_timer_dispatch();
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uint32_t now = timer_read_time();
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int32_t diff = next - now;
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if (diff > (int32_t)TIMER_MIN_TRY_TICKS)
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// Schedule next timer normally.
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return diff;
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if (unlikely(timer_is_before(tru, now))) {
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// Check if there are too many repeat timers
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if (diff < (int32_t)(-timer_from_us(1000)))
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try_shutdown("Rescheduled timer in the past");
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if (sched_tasks_busy()) {
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timer_repeat_until = now + TIMER_REPEAT_TICKS;
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return TIMER_DEFER_REPEAT_TICKS;
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}
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timer_repeat_until = tru = now + TIMER_IDLE_REPEAT_TICKS;
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}
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// Next timer in the past or near future - wait for it to be ready
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irq_enable();
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while (unlikely(diff > 0))
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diff = next - timer_read_time();
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irq_disable();
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}
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}
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// IRQ handler
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void __visible __aligned(16) // aligning helps stabilize perf benchmarks
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SysTick_Handler(void)
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{
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irq_disable();
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uint32_t diff = timer_dispatch_many();
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timer_set_diff(diff);
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irq_enable();
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}
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// Make sure timer_repeat_until doesn't wrap 32bit comparisons
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void
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timer_task(void)
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{
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uint32_t now = timer_read_time();
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irq_disable();
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if (timer_is_before(timer_repeat_until, now))
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timer_repeat_until = now;
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irq_enable();
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}
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DECL_TASK(timer_task);
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void TIM2_IRQHandler(void)
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{
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if(TIM2->SR & TIM_SR_UIF) {
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TIM2->SR &= ~TIM_SR_UIF; // clear UIF flag
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}
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}
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