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1#ifndef _ASM_X86_TIMER_H
2#define _ASM_X86_TIMER_H
3#include <linux/init.h>
4#include <linux/pm.h>
5#include <linux/percpu.h>
6#include <linux/interrupt.h>
7
8#define TICK_SIZE (tick_nsec / 1000)
9
10unsigned long long native_sched_clock(void);
11unsigned long native_calibrate_tsc(void);
12
13#ifdef CONFIG_X86_32
14extern int timer_ack;
15extern irqreturn_t timer_interrupt(int irq, void *dev_id);
16#endif /* CONFIG_X86_32 */
17extern int recalibrate_cpu_khz(void);
18
19extern int no_timer_check;
20
21#ifndef CONFIG_PARAVIRT
22#define calibrate_tsc() native_calibrate_tsc()
23#endif
24
25/* Accelerators for sched_clock()
26 * convert from cycles(64bits) => nanoseconds (64bits)
27 * basic equation:
28 * ns = cycles / (freq / ns_per_sec)
29 * ns = cycles * (ns_per_sec / freq)
30 * ns = cycles * (10^9 / (cpu_khz * 10^3))
31 * ns = cycles * (10^6 / cpu_khz)
32 *
33 * Then we use scaling math (suggested by george@mvista.com) to get:
34 * ns = cycles * (10^6 * SC / cpu_khz) / SC
35 * ns = cycles * cyc2ns_scale / SC
36 *
37 * And since SC is a constant power of two, we can convert the div
38 * into a shift.
39 *
40 * We can use khz divisor instead of mhz to keep a better precision, since
41 * cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
42 * (mathieu.desnoyers@polymtl.ca)
43 *
44 * -johnstul@us.ibm.com "math is hard, lets go shopping!"
45 */
46
47DECLARE_PER_CPU(unsigned long, cyc2ns);
48
49#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
50
51static inline unsigned long long __cycles_2_ns(unsigned long long cyc)
52{
53 return cyc * per_cpu(cyc2ns, smp_processor_id()) >> CYC2NS_SCALE_FACTOR;
54}
55
56static inline unsigned long long cycles_2_ns(unsigned long long cyc)
57{
58 unsigned long long ns;
59 unsigned long flags;
60
61 local_irq_save(flags);
62 ns = __cycles_2_ns(cyc);
63 local_irq_restore(flags);
64
65 return ns;
66}
67
68#endif /* _ASM_X86_TIMER_H */