1
2
3
4#include <linux/clockchips.h>
5#include <linux/init.h>
6#include <linux/io.h>
7#include <linux/spinlock.h>
8#include <linux/timex.h>
9#include <linux/module.h>
10#include <linux/i8253.h>
11#include <linux/smp.h>
12
13
14
15
16
17
18
19DEFINE_RAW_SPINLOCK(i8253_lock);
20EXPORT_SYMBOL(i8253_lock);
21
22#ifdef CONFIG_CLKSRC_I8253
23
24
25
26
27
28static u64 i8253_read(struct clocksource *cs)
29{
30 static int old_count;
31 static u32 old_jifs;
32 unsigned long flags;
33 int count;
34 u32 jifs;
35
36 raw_spin_lock_irqsave(&i8253_lock, flags);
37
38
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45
46
47
48
49
50 jifs = jiffies;
51 outb_p(0x00, PIT_MODE);
52 count = inb_p(PIT_CH0);
53 count |= inb_p(PIT_CH0) << 8;
54
55
56 if (count > PIT_LATCH) {
57 outb_p(0x34, PIT_MODE);
58 outb_p(PIT_LATCH & 0xff, PIT_CH0);
59 outb_p(PIT_LATCH >> 8, PIT_CH0);
60 count = PIT_LATCH - 1;
61 }
62
63
64
65
66
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68
69
70
71
72
73
74
75
76 if (count > old_count && jifs == old_jifs)
77 count = old_count;
78
79 old_count = count;
80 old_jifs = jifs;
81
82 raw_spin_unlock_irqrestore(&i8253_lock, flags);
83
84 count = (PIT_LATCH - 1) - count;
85
86 return (u64)(jifs * PIT_LATCH) + count;
87}
88
89static struct clocksource i8253_cs = {
90 .name = "pit",
91 .rating = 110,
92 .read = i8253_read,
93 .mask = CLOCKSOURCE_MASK(32),
94};
95
96int __init clocksource_i8253_init(void)
97{
98 return clocksource_register_hz(&i8253_cs, PIT_TICK_RATE);
99}
100#endif
101
102#ifdef CONFIG_CLKEVT_I8253
103static int pit_shutdown(struct clock_event_device *evt)
104{
105 if (!clockevent_state_oneshot(evt) && !clockevent_state_periodic(evt))
106 return 0;
107
108 raw_spin_lock(&i8253_lock);
109
110 outb_p(0x30, PIT_MODE);
111 outb_p(0, PIT_CH0);
112 outb_p(0, PIT_CH0);
113
114 raw_spin_unlock(&i8253_lock);
115 return 0;
116}
117
118static int pit_set_oneshot(struct clock_event_device *evt)
119{
120 raw_spin_lock(&i8253_lock);
121 outb_p(0x38, PIT_MODE);
122 raw_spin_unlock(&i8253_lock);
123 return 0;
124}
125
126static int pit_set_periodic(struct clock_event_device *evt)
127{
128 raw_spin_lock(&i8253_lock);
129
130
131 outb_p(0x34, PIT_MODE);
132 outb_p(PIT_LATCH & 0xff, PIT_CH0);
133 outb_p(PIT_LATCH >> 8, PIT_CH0);
134
135 raw_spin_unlock(&i8253_lock);
136 return 0;
137}
138
139
140
141
142
143
144static int pit_next_event(unsigned long delta, struct clock_event_device *evt)
145{
146 raw_spin_lock(&i8253_lock);
147 outb_p(delta & 0xff , PIT_CH0);
148 outb_p(delta >> 8 , PIT_CH0);
149 raw_spin_unlock(&i8253_lock);
150
151 return 0;
152}
153
154
155
156
157
158struct clock_event_device i8253_clockevent = {
159 .name = "pit",
160 .features = CLOCK_EVT_FEAT_PERIODIC,
161 .set_state_shutdown = pit_shutdown,
162 .set_state_periodic = pit_set_periodic,
163 .set_next_event = pit_next_event,
164};
165
166
167
168
169
170void __init clockevent_i8253_init(bool oneshot)
171{
172 if (oneshot) {
173 i8253_clockevent.features |= CLOCK_EVT_FEAT_ONESHOT;
174 i8253_clockevent.set_state_oneshot = pit_set_oneshot;
175 }
176
177
178
179
180 i8253_clockevent.cpumask = cpumask_of(smp_processor_id());
181
182 clockevents_config_and_register(&i8253_clockevent, PIT_TICK_RATE,
183 0xF, 0x7FFF);
184}
185#endif
186