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// Handling of timers on linux systems
//
// Copyright (C) 2017 Kevin O'Connor <kevin@koconnor.net>
//
// This file may be distributed under the terms of the GNU GPLv3 license.
#include <time.h> // struct timespec
#include "autoconf.h" // CONFIG_CLOCK_FREQ
#include "board/misc.h" // timer_from_us
#include "board/irq.h" // irq_disable
#include "basecmd.h" // stats_note_sleep
#include "command.h" // DECL_CONSTANT
#include "generic/timer_irq.h" // timer_dispatch_many
#include "internal.h" // console_sleep
#include "sched.h" // DECL_INIT
/****************************************************************
* Timespec helpers
****************************************************************/
static uint32_t last_read_time_counter;
static struct timespec last_read_time, next_wake_time;
static time_t start_sec;
#define NSECS 1000000000
#define NSECS_PER_TICK (NSECS / CONFIG_CLOCK_FREQ)
// Compare two 'struct timespec' times
static inline uint8_t
timespec_is_before(struct timespec ts1, struct timespec ts2)
{
return (ts1.tv_sec < ts2.tv_sec
|| (ts1.tv_sec == ts2.tv_sec && ts1.tv_nsec < ts2.tv_nsec));
}
// Convert a 'struct timespec' to a counter value
static inline uint32_t
timespec_to_time(struct timespec ts)
{
return ((ts.tv_sec - start_sec) * CONFIG_CLOCK_FREQ
+ ts.tv_nsec / NSECS_PER_TICK);
}
// Convert an internal time counter to a 'struct timespec'
static inline struct timespec
timespec_from_time(uint32_t time)
{
int32_t counter_diff = time - last_read_time_counter;
struct timespec ts;
ts.tv_sec = last_read_time.tv_sec;
ts.tv_nsec = last_read_time.tv_nsec + counter_diff * NSECS_PER_TICK;
if ((unsigned long)ts.tv_nsec >= NSECS) {
if (ts.tv_nsec < 0) {
ts.tv_sec--;
ts.tv_nsec += NSECS;
} else {
ts.tv_sec++;
ts.tv_nsec -= NSECS;
}
}
return ts;
}
// Add a given number of nanoseconds to a 'struct timespec'
static inline struct timespec
timespec_add(struct timespec ts, long ns)
{
ts.tv_nsec += ns;
if (ts.tv_nsec >= NSECS) {
ts.tv_sec++;
ts.tv_nsec -= NSECS;
}
return ts;
}
// Return the current time
static struct timespec
timespec_read(void)
{
struct timespec ts;
clock_gettime(CLOCK_MONOTONIC, &ts);
return ts;
}
// Periodically update last_read_time / last_read_time_counter
void
timespec_update(void)
{
last_read_time = timespec_read();
last_read_time_counter = timespec_to_time(last_read_time);
}
DECL_TASK(timespec_update);
// Check if a given time has past
int
timer_check_periodic(struct timespec *ts)
{
if (timespec_is_before(next_wake_time, *ts))
return 0;
*ts = next_wake_time;
ts->tv_sec += 2;
return 1;
}
/****************************************************************
* Timers
****************************************************************/
DECL_CONSTANT(CLOCK_FREQ, CONFIG_CLOCK_FREQ);
// Return the number of clock ticks for a given number of microseconds
uint32_t
timer_from_us(uint32_t us)
{
return us * (CONFIG_CLOCK_FREQ / 1000000);
}
// Return true if time1 is before time2. Always use this function to
// compare times as regular C comparisons can fail if the counter
// rolls over.
uint8_t
timer_is_before(uint32_t time1, uint32_t time2)
{
return (int32_t)(time1 - time2) < 0;
}
// Return the current time (in clock ticks)
uint32_t
timer_read_time(void)
{
return timespec_to_time(timespec_read());
}
// Activate timer dispatch as soon as possible
void
timer_kick(void)
{
next_wake_time = last_read_time;
}
static struct timespec timer_repeat_until;
#define TIMER_IDLE_REPEAT_NS 500000
#define TIMER_REPEAT_NS 100000
#define TIMER_MIN_TRY_NS 1000
#define TIMER_DEFER_REPEAT_NS 5000
// Invoke timers
static void
timer_dispatch(void)
{
struct timespec tru = timer_repeat_until;
for (;;) {
// Run the next software timer
uint32_t next = sched_timer_dispatch();
struct timespec nt = timespec_from_time(next);
struct timespec now = timespec_read();
if (!timespec_is_before(nt, timespec_add(now, TIMER_MIN_TRY_NS))) {
// Schedule next timer normally.
next_wake_time = nt;
return;
}
if (unlikely(timespec_is_before(tru, now))) {
// Check if there are too many repeat timers
if (unlikely(timespec_is_before(timespec_add(nt, 100000000), now)))
try_shutdown("Rescheduled timer in the past");
if (sched_tasks_busy()) {
timer_repeat_until = timespec_add(now, TIMER_REPEAT_NS);
next_wake_time = timespec_add(now, TIMER_DEFER_REPEAT_NS);
return;
}
timer_repeat_until = timespec_add(now, TIMER_IDLE_REPEAT_NS);
}
// Next timer in the past or near future - wait for it to be ready
while (unlikely(timespec_is_before(now, nt)))
now = timespec_read();
}
}
void
timer_init(void)
{
start_sec = timespec_read().tv_sec;
timer_repeat_until.tv_sec = start_sec + 2;
timespec_update();
timer_kick();
}
DECL_INIT(timer_init);
/****************************************************************
* Interrupt wrappers
****************************************************************/
void
irq_disable(void)
{
}
void
irq_enable(void)
{
}
irqstatus_t
irq_save(void)
{
return 0;
}
void
irq_restore(irqstatus_t flag)
{
}
void
irq_wait(void)
{
console_sleep(next_wake_time);
}
void
irq_poll(void)
{
if (!timespec_is_before(timespec_read(), next_wake_time))
timer_dispatch();
}
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