blob: 69f4e64a270f04ad907d1ba7050771508c1b0ea6 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
|
// Generic interrupt based timer helper functions
//
// Copyright (C) 2017 Kevin O'Connor <kevin@koconnor.net>
//
// This file may be distributed under the terms of the GNU GPLv3 license.
#include "autoconf.h" // CONFIG_CLOCK_FREQ
#include "board/irq.h" // irq_disable
#include "board/misc.h" // timer_from_us
#include "board/timer_irq.h" // timer_dispatch_many
#include "command.h" // shutdown
#include "sched.h" // sched_timer_kick
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;
}
// Called by main code once every millisecond. (IRQs disabled.)
void
timer_periodic(void)
{
}
static uint32_t timer_repeat_until;
#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)
// Reschedule timers after a brief pause to prevent task starvation
static uint32_t noinline
force_defer(uint32_t next)
{
uint32_t now = timer_read_time();
if (timer_is_before(next + timer_from_us(1000), now))
shutdown("Rescheduled timer in the past");
timer_repeat_until = now + TIMER_REPEAT_TICKS;
return now + TIMER_DEFER_REPEAT_TICKS;
}
// Invoke timers - called from board irq code.
uint32_t
timer_dispatch_many(void)
{
uint32_t tru = timer_repeat_until;
for (;;) {
// Run the next software timer
uint32_t next = sched_timer_dispatch();
uint32_t now = timer_read_time();
int32_t diff = next - now;
if (diff > (int32_t)TIMER_MIN_TRY_TICKS)
// Schedule next timer normally.
return next;
if (unlikely(timer_is_before(tru, now)))
// Too many repeat timers from a single interrupt - force a pause
return force_defer(next);
// Next timer in the past or near future - wait for it to be ready
irq_enable();
while (unlikely(diff > 0))
diff = next - timer_read_time();
irq_disable();
}
}
// Periodic background task that temporarily boosts priority of
// timers. This helps prioritize timers when tasks are idling.
static void
timer_task(void)
{
irq_disable();
timer_repeat_until = timer_read_time() + TIMER_IDLE_REPEAT_TICKS;
irq_enable();
}
DECL_TASK(timer_task);
static void
timer_irq_shutdown(void)
{
timer_repeat_until = timer_read_time() + TIMER_IDLE_REPEAT_TICKS;
}
DECL_SHUTDOWN(timer_irq_shutdown);
|
