This source file includes following definitions.
- i8253_read
- clocksource_i8253_init
- pit_shutdown
- pit_set_oneshot
- pit_set_periodic
- pit_next_event
- clockevent_i8253_init
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5 #include <linux/clockchips.h>
6 #include <linux/init.h>
7 #include <linux/io.h>
8 #include <linux/spinlock.h>
9 #include <linux/timex.h>
10 #include <linux/module.h>
11 #include <linux/i8253.h>
12 #include <linux/smp.h>
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19
20 DEFINE_RAW_SPINLOCK(i8253_lock);
21 EXPORT_SYMBOL(i8253_lock);
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28 bool i8253_clear_counter_on_shutdown __ro_after_init = true;
29
30 #ifdef CONFIG_CLKSRC_I8253
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35
36 static u64 i8253_read(struct clocksource *cs)
37 {
38 static int old_count;
39 static u32 old_jifs;
40 unsigned long flags;
41 int count;
42 u32 jifs;
43
44 raw_spin_lock_irqsave(&i8253_lock, flags);
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58 jifs = jiffies;
59 outb_p(0x00, PIT_MODE);
60 count = inb_p(PIT_CH0);
61 count |= inb_p(PIT_CH0) << 8;
62
63
64 if (count > PIT_LATCH) {
65 outb_p(0x34, PIT_MODE);
66 outb_p(PIT_LATCH & 0xff, PIT_CH0);
67 outb_p(PIT_LATCH >> 8, PIT_CH0);
68 count = PIT_LATCH - 1;
69 }
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83
84 if (count > old_count && jifs == old_jifs)
85 count = old_count;
86
87 old_count = count;
88 old_jifs = jifs;
89
90 raw_spin_unlock_irqrestore(&i8253_lock, flags);
91
92 count = (PIT_LATCH - 1) - count;
93
94 return (u64)(jifs * PIT_LATCH) + count;
95 }
96
97 static struct clocksource i8253_cs = {
98 .name = "pit",
99 .rating = 110,
100 .read = i8253_read,
101 .mask = CLOCKSOURCE_MASK(32),
102 };
103
104 int __init clocksource_i8253_init(void)
105 {
106 return clocksource_register_hz(&i8253_cs, PIT_TICK_RATE);
107 }
108 #endif
109
110 #ifdef CONFIG_CLKEVT_I8253
111 static int pit_shutdown(struct clock_event_device *evt)
112 {
113 if (!clockevent_state_oneshot(evt) && !clockevent_state_periodic(evt))
114 return 0;
115
116 raw_spin_lock(&i8253_lock);
117
118 outb_p(0x30, PIT_MODE);
119
120 if (i8253_clear_counter_on_shutdown) {
121 outb_p(0, PIT_CH0);
122 outb_p(0, PIT_CH0);
123 }
124
125 raw_spin_unlock(&i8253_lock);
126 return 0;
127 }
128
129 static int pit_set_oneshot(struct clock_event_device *evt)
130 {
131 raw_spin_lock(&i8253_lock);
132 outb_p(0x38, PIT_MODE);
133 raw_spin_unlock(&i8253_lock);
134 return 0;
135 }
136
137 static int pit_set_periodic(struct clock_event_device *evt)
138 {
139 raw_spin_lock(&i8253_lock);
140
141
142 outb_p(0x34, PIT_MODE);
143 outb_p(PIT_LATCH & 0xff, PIT_CH0);
144 outb_p(PIT_LATCH >> 8, PIT_CH0);
145
146 raw_spin_unlock(&i8253_lock);
147 return 0;
148 }
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154
155 static int pit_next_event(unsigned long delta, struct clock_event_device *evt)
156 {
157 raw_spin_lock(&i8253_lock);
158 outb_p(delta & 0xff , PIT_CH0);
159 outb_p(delta >> 8 , PIT_CH0);
160 raw_spin_unlock(&i8253_lock);
161
162 return 0;
163 }
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168
169 struct clock_event_device i8253_clockevent = {
170 .name = "pit",
171 .features = CLOCK_EVT_FEAT_PERIODIC,
172 .set_state_shutdown = pit_shutdown,
173 .set_state_periodic = pit_set_periodic,
174 .set_next_event = pit_next_event,
175 };
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180
181 void __init clockevent_i8253_init(bool oneshot)
182 {
183 if (oneshot) {
184 i8253_clockevent.features |= CLOCK_EVT_FEAT_ONESHOT;
185 i8253_clockevent.set_state_oneshot = pit_set_oneshot;
186 }
187
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190
191 i8253_clockevent.cpumask = cpumask_of(smp_processor_id());
192
193 clockevents_config_and_register(&i8253_clockevent, PIT_TICK_RATE,
194 0xF, 0x7FFF);
195 }
196 #endif