diff options
Diffstat (limited to 'arch/x86/kernel/i8253.c')
-rw-r--r-- | arch/x86/kernel/i8253.c | 208 |
1 files changed, 208 insertions, 0 deletions
diff --git a/arch/x86/kernel/i8253.c b/arch/x86/kernel/i8253.c new file mode 100644 index 000000000000..ac15e4cbd9c1 --- /dev/null +++ b/arch/x86/kernel/i8253.c | |||
@@ -0,0 +1,208 @@ | |||
1 | /* | ||
2 | * i8253.c 8253/PIT functions | ||
3 | * | ||
4 | */ | ||
5 | #include <linux/clockchips.h> | ||
6 | #include <linux/init.h> | ||
7 | #include <linux/interrupt.h> | ||
8 | #include <linux/jiffies.h> | ||
9 | #include <linux/module.h> | ||
10 | #include <linux/spinlock.h> | ||
11 | |||
12 | #include <asm/smp.h> | ||
13 | #include <asm/delay.h> | ||
14 | #include <asm/i8253.h> | ||
15 | #include <asm/io.h> | ||
16 | |||
17 | DEFINE_SPINLOCK(i8253_lock); | ||
18 | EXPORT_SYMBOL(i8253_lock); | ||
19 | |||
20 | /* | ||
21 | * HPET replaces the PIT, when enabled. So we need to know, which of | ||
22 | * the two timers is used | ||
23 | */ | ||
24 | struct clock_event_device *global_clock_event; | ||
25 | |||
26 | /* | ||
27 | * Initialize the PIT timer. | ||
28 | * | ||
29 | * This is also called after resume to bring the PIT into operation again. | ||
30 | */ | ||
31 | static void init_pit_timer(enum clock_event_mode mode, | ||
32 | struct clock_event_device *evt) | ||
33 | { | ||
34 | unsigned long flags; | ||
35 | |||
36 | spin_lock_irqsave(&i8253_lock, flags); | ||
37 | |||
38 | switch(mode) { | ||
39 | case CLOCK_EVT_MODE_PERIODIC: | ||
40 | /* binary, mode 2, LSB/MSB, ch 0 */ | ||
41 | outb_p(0x34, PIT_MODE); | ||
42 | outb_p(LATCH & 0xff , PIT_CH0); /* LSB */ | ||
43 | outb(LATCH >> 8 , PIT_CH0); /* MSB */ | ||
44 | break; | ||
45 | |||
46 | case CLOCK_EVT_MODE_SHUTDOWN: | ||
47 | case CLOCK_EVT_MODE_UNUSED: | ||
48 | if (evt->mode == CLOCK_EVT_MODE_PERIODIC || | ||
49 | evt->mode == CLOCK_EVT_MODE_ONESHOT) { | ||
50 | outb_p(0x30, PIT_MODE); | ||
51 | outb_p(0, PIT_CH0); | ||
52 | outb_p(0, PIT_CH0); | ||
53 | } | ||
54 | break; | ||
55 | |||
56 | case CLOCK_EVT_MODE_ONESHOT: | ||
57 | /* One shot setup */ | ||
58 | outb_p(0x38, PIT_MODE); | ||
59 | break; | ||
60 | |||
61 | case CLOCK_EVT_MODE_RESUME: | ||
62 | /* Nothing to do here */ | ||
63 | break; | ||
64 | } | ||
65 | spin_unlock_irqrestore(&i8253_lock, flags); | ||
66 | } | ||
67 | |||
68 | /* | ||
69 | * Program the next event in oneshot mode | ||
70 | * | ||
71 | * Delta is given in PIT ticks | ||
72 | */ | ||
73 | static int pit_next_event(unsigned long delta, struct clock_event_device *evt) | ||
74 | { | ||
75 | unsigned long flags; | ||
76 | |||
77 | spin_lock_irqsave(&i8253_lock, flags); | ||
78 | outb_p(delta & 0xff , PIT_CH0); /* LSB */ | ||
79 | outb(delta >> 8 , PIT_CH0); /* MSB */ | ||
80 | spin_unlock_irqrestore(&i8253_lock, flags); | ||
81 | |||
82 | return 0; | ||
83 | } | ||
84 | |||
85 | /* | ||
86 | * On UP the PIT can serve all of the possible timer functions. On SMP systems | ||
87 | * it can be solely used for the global tick. | ||
88 | * | ||
89 | * The profiling and update capabilites are switched off once the local apic is | ||
90 | * registered. This mechanism replaces the previous #ifdef LOCAL_APIC - | ||
91 | * !using_apic_timer decisions in do_timer_interrupt_hook() | ||
92 | */ | ||
93 | struct clock_event_device pit_clockevent = { | ||
94 | .name = "pit", | ||
95 | .features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT, | ||
96 | .set_mode = init_pit_timer, | ||
97 | .set_next_event = pit_next_event, | ||
98 | .shift = 32, | ||
99 | .irq = 0, | ||
100 | }; | ||
101 | |||
102 | /* | ||
103 | * Initialize the conversion factor and the min/max deltas of the clock event | ||
104 | * structure and register the clock event source with the framework. | ||
105 | */ | ||
106 | void __init setup_pit_timer(void) | ||
107 | { | ||
108 | /* | ||
109 | * Start pit with the boot cpu mask and make it global after the | ||
110 | * IO_APIC has been initialized. | ||
111 | */ | ||
112 | pit_clockevent.cpumask = cpumask_of_cpu(smp_processor_id()); | ||
113 | pit_clockevent.mult = div_sc(CLOCK_TICK_RATE, NSEC_PER_SEC, 32); | ||
114 | pit_clockevent.max_delta_ns = | ||
115 | clockevent_delta2ns(0x7FFF, &pit_clockevent); | ||
116 | pit_clockevent.min_delta_ns = | ||
117 | clockevent_delta2ns(0xF, &pit_clockevent); | ||
118 | clockevents_register_device(&pit_clockevent); | ||
119 | global_clock_event = &pit_clockevent; | ||
120 | } | ||
121 | |||
122 | #ifndef CONFIG_X86_64 | ||
123 | /* | ||
124 | * Since the PIT overflows every tick, its not very useful | ||
125 | * to just read by itself. So use jiffies to emulate a free | ||
126 | * running counter: | ||
127 | */ | ||
128 | static cycle_t pit_read(void) | ||
129 | { | ||
130 | unsigned long flags; | ||
131 | int count; | ||
132 | u32 jifs; | ||
133 | static int old_count; | ||
134 | static u32 old_jifs; | ||
135 | |||
136 | spin_lock_irqsave(&i8253_lock, flags); | ||
137 | /* | ||
138 | * Although our caller may have the read side of xtime_lock, | ||
139 | * this is now a seqlock, and we are cheating in this routine | ||
140 | * by having side effects on state that we cannot undo if | ||
141 | * there is a collision on the seqlock and our caller has to | ||
142 | * retry. (Namely, old_jifs and old_count.) So we must treat | ||
143 | * jiffies as volatile despite the lock. We read jiffies | ||
144 | * before latching the timer count to guarantee that although | ||
145 | * the jiffies value might be older than the count (that is, | ||
146 | * the counter may underflow between the last point where | ||
147 | * jiffies was incremented and the point where we latch the | ||
148 | * count), it cannot be newer. | ||
149 | */ | ||
150 | jifs = jiffies; | ||
151 | outb_p(0x00, PIT_MODE); /* latch the count ASAP */ | ||
152 | count = inb_p(PIT_CH0); /* read the latched count */ | ||
153 | count |= inb_p(PIT_CH0) << 8; | ||
154 | |||
155 | /* VIA686a test code... reset the latch if count > max + 1 */ | ||
156 | if (count > LATCH) { | ||
157 | outb_p(0x34, PIT_MODE); | ||
158 | outb_p(LATCH & 0xff, PIT_CH0); | ||
159 | outb(LATCH >> 8, PIT_CH0); | ||
160 | count = LATCH - 1; | ||
161 | } | ||
162 | |||
163 | /* | ||
164 | * It's possible for count to appear to go the wrong way for a | ||
165 | * couple of reasons: | ||
166 | * | ||
167 | * 1. The timer counter underflows, but we haven't handled the | ||
168 | * resulting interrupt and incremented jiffies yet. | ||
169 | * 2. Hardware problem with the timer, not giving us continuous time, | ||
170 | * the counter does small "jumps" upwards on some Pentium systems, | ||
171 | * (see c't 95/10 page 335 for Neptun bug.) | ||
172 | * | ||
173 | * Previous attempts to handle these cases intelligently were | ||
174 | * buggy, so we just do the simple thing now. | ||
175 | */ | ||
176 | if (count > old_count && jifs == old_jifs) { | ||
177 | count = old_count; | ||
178 | } | ||
179 | old_count = count; | ||
180 | old_jifs = jifs; | ||
181 | |||
182 | spin_unlock_irqrestore(&i8253_lock, flags); | ||
183 | |||
184 | count = (LATCH - 1) - count; | ||
185 | |||
186 | return (cycle_t)(jifs * LATCH) + count; | ||
187 | } | ||
188 | |||
189 | static struct clocksource clocksource_pit = { | ||
190 | .name = "pit", | ||
191 | .rating = 110, | ||
192 | .read = pit_read, | ||
193 | .mask = CLOCKSOURCE_MASK(32), | ||
194 | .mult = 0, | ||
195 | .shift = 20, | ||
196 | }; | ||
197 | |||
198 | static int __init init_pit_clocksource(void) | ||
199 | { | ||
200 | if (num_possible_cpus() > 1) /* PIT does not scale! */ | ||
201 | return 0; | ||
202 | |||
203 | clocksource_pit.mult = clocksource_hz2mult(CLOCK_TICK_RATE, 20); | ||
204 | return clocksource_register(&clocksource_pit); | ||
205 | } | ||
206 | arch_initcall(init_pit_clocksource); | ||
207 | |||
208 | #endif | ||