diff options
Diffstat (limited to 'src/stm32f1/timer.c')
| -rw-r--r-- | src/stm32f1/timer.c | 188 |
1 files changed, 188 insertions, 0 deletions
diff --git a/src/stm32f1/timer.c b/src/stm32f1/timer.c new file mode 100644 index 00000000..76b683b3 --- /dev/null +++ b/src/stm32f1/timer.c @@ -0,0 +1,188 @@ +// STM32F1 timer interrupt scheduling code. +// +// Copyright (C) 2018 Grigori Goronzy <greg@kinoho.net> +// +// This file may be distributed under the terms of the GNU GPLv3 license. + +#include "autoconf.h" +#include "board/misc.h" // timer_from_us +#include "stm32f1xx.h" +#include "stm32f1xx.h" +#include "stm32f1xx_ll_bus.h" +#include "stm32f1xx_ll_tim.h" +#include "command.h" // shutdown +#include "board/irq.h" // irq_save +#include "sched.h" // sched_timer_dispatch + + +/**************************************************************** + * Low level timer code + ****************************************************************/ + +DECL_CONSTANT(CLOCK_FREQ, CONFIG_CLOCK_FREQ); + +union u32_u { + struct { uint8_t b0, b1, b2, b3; }; + struct { uint16_t lo, hi; }; + uint32_t val; +}; + +static inline uint16_t +timer_get(void) +{ + return LL_TIM_GetCounter(TIM2); +} + +static inline void +timer_set(uint16_t next) +{ + LL_TIM_OC_SetCompareCH1(TIM2, next); +} + +static inline void +timer_repeat_set(uint16_t next) +{ + LL_TIM_OC_SetCompareCH2(TIM2, next); + LL_TIM_ClearFlag_CC2(TIM2); +} + +// Activate timer dispatch as soon as possible +void +timer_kick(void) +{ + timer_set(timer_get() + 50); + LL_TIM_ClearFlag_CC1(TIM2); +} + +static struct timer wrap_timer; + +void +timer_reset(void) +{ + sched_add_timer(&wrap_timer); +} +DECL_SHUTDOWN(timer_reset); + +void +timer_init(void) +{ + irqstatus_t flag = irq_save(); + LL_APB1_GRP1_EnableClock(LL_APB1_GRP1_PERIPH_TIM2); + LL_TIM_SetPrescaler(TIM2, __LL_TIM_CALC_PSC(SystemCoreClock, CONFIG_CLOCK_FREQ)); + LL_TIM_SetCounter(TIM2, 0); + LL_TIM_SetAutoReload(TIM2, 0xFFFF); + LL_TIM_EnableIT_CC1(TIM2); + LL_TIM_CC_EnableChannel(TIM2, LL_TIM_CHANNEL_CH1); + LL_TIM_CC_EnableChannel(TIM2, LL_TIM_CHANNEL_CH2); + NVIC_EnableIRQ(TIM2_IRQn); + NVIC_SetPriority(TIM2_IRQn, 0); + timer_kick(); + timer_repeat_set(timer_get() + 50); + timer_reset(); + LL_TIM_EnableCounter(TIM2); + irq_restore(flag); +} +DECL_INIT(timer_init); + + +/**************************************************************** + * 32bit timer wrappers + ****************************************************************/ + +static uint16_t timer_high; + +// Return the current time (in absolute clock ticks). +uint32_t +timer_read_time(void) +{ + irqstatus_t flag = irq_save(); + union u32_u calc = { .val = timer_get() }; + calc.hi = timer_high; + if (unlikely(LL_TIM_IsActiveFlag_UPDATE(TIM2))) { + irq_restore(flag); + if (calc.b1 < 0xff) + calc.hi++; + return calc.val; + } + irq_restore(flag); + return calc.val; +} + +// Timer that runs every cycle - allows 16bit comparison optimizations +static uint_fast8_t +timer_event(struct timer *t) +{ + union u32_u *nextwake = (void*)&wrap_timer.waketime; + if (LL_TIM_IsActiveFlag_UPDATE(TIM2)) { + // Hardware timer has overflowed - update overflow counter + LL_TIM_ClearFlag_UPDATE(TIM2); + timer_high++; + *nextwake = (union u32_u){ .hi = timer_high, .lo = 0x8000 }; + } else { + *nextwake = (union u32_u){ .hi = timer_high + 1, .lo = 0x0000 }; + } + return SF_RESCHEDULE; +} +static struct timer wrap_timer = { + .func = timer_event, + .waketime = 0x8000, +}; + +#define TIMER_IDLE_REPEAT_TICKS timer_from_us(500) +#define TIMER_REPEAT_TICKS timer_from_us(100) + +#define TIMER_MIN_TRY_TICKS timer_from_us(1) +#define TIMER_DEFER_REPEAT_TICKS timer_from_us(5) + +// Hardware timer IRQ handler - dispatch software timers +void __visible __aligned(16) +TIM2_IRQHandler(void) +{ + irq_disable(); + LL_TIM_ClearFlag_CC1(TIM2); + uint16_t next; + for (;;) { + // Run the next software timer + next = sched_timer_dispatch(); + + for (;;) { + int16_t diff = timer_get() - next; + if (likely(diff >= 0)) { + // Another timer is pending - briefly allow irqs and then run it + irq_enable(); + if (unlikely(LL_TIM_IsActiveFlag_CC2(TIM2))) + goto check_defer; + irq_disable(); + break; + } + + if (likely(diff <= -TIMER_MIN_TRY_TICKS)) + // Schedule next timer normally + goto done; + + irq_enable(); + if (unlikely(LL_TIM_IsActiveFlag_CC2(TIM2))) + goto check_defer; + irq_disable(); + continue; + + check_defer: + // Check if there are too many repeat timers + irq_disable(); + uint16_t now = timer_get(); + if ((int16_t)(next - now) < (int16_t)(-timer_from_us(1000))) + try_shutdown("Rescheduled timer in the past"); + if (sched_tasks_busy()) { + timer_repeat_set(now + TIMER_REPEAT_TICKS); + next = now + TIMER_DEFER_REPEAT_TICKS; + goto done; + } + timer_repeat_set(now + TIMER_IDLE_REPEAT_TICKS); + timer_set(now); + } + } + +done: + timer_set(next); + irq_enable(); +} |