diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/stm32f1/timer.c | 86 |
1 files changed, 39 insertions, 47 deletions
diff --git a/src/stm32f1/timer.c b/src/stm32f1/timer.c index c3b13989..a247983d 100644 --- a/src/stm32f1/timer.c +++ b/src/stm32f1/timer.c @@ -1,6 +1,7 @@ // STM32F1 timer interrupt scheduling code. // // Copyright (C) 2018 Grigori Goronzy <greg@kinoho.net> +// Copyright (C) 2018 Kevin O'Connor <kevin@koconnor.net> // // This file may be distributed under the terms of the GNU GPLv3 license. @@ -11,6 +12,7 @@ #include "stm32f1xx_ll_bus.h" #include "stm32f1xx_ll_tim.h" #include "command.h" // shutdown +#include "board/io.h" // readl #include "board/irq.h" // irq_save #include "sched.h" // sched_timer_dispatch @@ -21,12 +23,6 @@ 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 uint32_t timer_get(void) { @@ -54,7 +50,37 @@ timer_kick(void) LL_TIM_ClearFlag_CC1(TIM2); } -static struct timer wrap_timer; + +/**************************************************************** + * 16bit hardware timer to 32bit conversion + ****************************************************************/ + +// High bits of timer (top 17 bits) +static uint32_t timer_high; + +// Return the current time (in absolute clock ticks). +uint32_t +timer_read_time(void) +{ + uint32_t th = readl(&timer_high); + uint32_t cur = timer_get(); + // Combine timer_high (high 17 bits) and current time (low 16 + // bits) using method that handles rollovers correctly. + return (th ^ cur) + (th & 0x8000); +} + +// Update timer_high every 0x8000 clock ticks +static uint_fast8_t +timer_event(struct timer *t) +{ + timer_high += 0x8000; + t->waketime = timer_high + 0x8000; + return SF_RESCHEDULE; +} +static struct timer wrap_timer = { + .func = timer_event, + .waketime = 0x8000, +}; void timer_reset(void) @@ -63,6 +89,11 @@ timer_reset(void) } DECL_SHUTDOWN(timer_reset); + +/**************************************************************** + * Timer init + ****************************************************************/ + void timer_init(void) { @@ -86,48 +117,9 @@ DECL_INIT(timer_init); /**************************************************************** - * 32bit timer wrappers + * Main timer dispatch irq handler ****************************************************************/ -static uint32_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) |