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
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
|
/*
* 8253/PIT functions
*
*/
#include <linux/clockchips.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/jiffies.h>
#include <linux/module.h>
#include <linux/timex.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/io.h>
#include <asm/i8253.h>
#include <asm/hpet.h>
#include <asm/smp.h>
DEFINE_RAW_SPINLOCK(i8253_lock);
EXPORT_SYMBOL(i8253_lock);
/*
* HPET replaces the PIT, when enabled. So we need to know, which of
* the two timers is used
*/
struct clock_event_device *global_clock_event;
/*
* Initialize the PIT timer.
*
* This is also called after resume to bring the PIT into operation again.
*/
static void init_pit_timer(enum clock_event_mode mode,
struct clock_event_device *evt)
{
raw_spin_lock(&i8253_lock);
switch (mode) {
case CLOCK_EVT_MODE_PERIODIC:
/* binary, mode 2, LSB/MSB, ch 0 */
outb_pit(0x34, PIT_MODE);
outb_pit(LATCH & 0xff , PIT_CH0); /* LSB */
outb_pit(LATCH >> 8 , PIT_CH0); /* MSB */
break;
case CLOCK_EVT_MODE_SHUTDOWN:
case CLOCK_EVT_MODE_UNUSED:
if (evt->mode == CLOCK_EVT_MODE_PERIODIC ||
evt->mode == CLOCK_EVT_MODE_ONESHOT) {
outb_pit(0x30, PIT_MODE);
outb_pit(0, PIT_CH0);
outb_pit(0, PIT_CH0);
}
break;
case CLOCK_EVT_MODE_ONESHOT:
/* One shot setup */
outb_pit(0x38, PIT_MODE);
break;
case CLOCK_EVT_MODE_RESUME:
/* Nothing to do here */
break;
}
raw_spin_unlock(&i8253_lock);
}
/*
* Program the next event in oneshot mode
*
* Delta is given in PIT ticks
*/
static int pit_next_event(unsigned long delta, struct clock_event_device *evt)
{
raw_spin_lock(&i8253_lock);
outb_pit(delta & 0xff , PIT_CH0); /* LSB */
outb_pit(delta >> 8 , PIT_CH0); /* MSB */
raw_spin_unlock(&i8253_lock);
return 0;
}
/*
* On UP the PIT can serve all of the possible timer functions. On SMP systems
* it can be solely used for the global tick.
*
* The profiling and update capabilities are switched off once the local apic is
* registered. This mechanism replaces the previous #ifdef LOCAL_APIC -
* !using_apic_timer decisions in do_timer_interrupt_hook()
*/
static struct clock_event_device pit_ce = {
.name = "pit",
.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
.set_mode = init_pit_timer,
.set_next_event = pit_next_event,
.irq = 0,
};
/*
* Initialize the conversion factor and the min/max deltas of the clock event
* structure and register the clock event source with the framework.
*/
void __init setup_pit_timer(void)
{
/*
* Start pit with the boot cpu mask and make it global after the
* IO_APIC has been initialized.
*/
pit_ce.cpumask = cpumask_of(smp_processor_id());
clockevents_config_and_register(&pit_ce, CLOCK_TICK_RATE, 0xF, 0x7FFF);
global_clock_event = &pit_ce;
}
#ifndef CONFIG_X86_64
static int __init init_pit_clocksource(void)
{
/*
* Several reasons not to register PIT as a clocksource:
*
* - On SMP PIT does not scale due to i8253_lock
* - when HPET is enabled
* - when local APIC timer is active (PIT is switched off)
*/
if (num_possible_cpus() > 1 || is_hpet_enabled() ||
pit_ce.mode != CLOCK_EVT_MODE_PERIODIC)
return 0;
return clocksource_i8253_init();
}
arch_initcall(init_pit_clocksource);
#endif /* !CONFIG_X86_64 */
|
