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1da177e4 LT |
1 | #ifndef _ASMi386_TIMER_H |
2 | #define _ASMi386_TIMER_H | |
3 | #include <linux/init.h> | |
c3c433e4 | 4 | #include <linux/pm.h> |
53d517cd | 5 | #include <linux/percpu.h> |
1da177e4 | 6 | |
1da177e4 | 7 | #define TICK_SIZE (tick_nsec / 1000) |
6cb9a835 | 8 | |
6cb9a835 | 9 | unsigned long long native_sched_clock(void); |
1182d852 | 10 | unsigned long native_calculate_cpu_khz(void); |
6cb9a835 | 11 | |
1da177e4 | 12 | extern int timer_ack; |
7ce0bcfd | 13 | extern int no_timer_check; |
c5d28fb2 | 14 | extern int recalibrate_cpu_khz(void); |
1da177e4 | 15 | |
6cb9a835 | 16 | #ifndef CONFIG_PARAVIRT |
1182d852 | 17 | #define calculate_cpu_khz() native_calculate_cpu_khz() |
6cb9a835 ZA |
18 | #endif |
19 | ||
53d517cd | 20 | /* Accelerators for sched_clock() |
688340ea JF |
21 | * convert from cycles(64bits) => nanoseconds (64bits) |
22 | * basic equation: | |
23 | * ns = cycles / (freq / ns_per_sec) | |
24 | * ns = cycles * (ns_per_sec / freq) | |
25 | * ns = cycles * (10^9 / (cpu_khz * 10^3)) | |
26 | * ns = cycles * (10^6 / cpu_khz) | |
27 | * | |
28 | * Then we use scaling math (suggested by george@mvista.com) to get: | |
29 | * ns = cycles * (10^6 * SC / cpu_khz) / SC | |
30 | * ns = cycles * cyc2ns_scale / SC | |
31 | * | |
32 | * And since SC is a constant power of two, we can convert the div | |
33 | * into a shift. | |
34 | * | |
53d517cd | 35 | * We can use khz divisor instead of mhz to keep a better precision, since |
688340ea JF |
36 | * cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits. |
37 | * (mathieu.desnoyers@polymtl.ca) | |
38 | * | |
39 | * -johnstul@us.ibm.com "math is hard, lets go shopping!" | |
40 | */ | |
53d517cd GC |
41 | |
42 | DECLARE_PER_CPU(unsigned long, cyc2ns); | |
688340ea JF |
43 | |
44 | #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */ | |
45 | ||
53d517cd | 46 | static inline unsigned long long __cycles_2_ns(unsigned long long cyc) |
688340ea | 47 | { |
53d517cd | 48 | return cyc * per_cpu(cyc2ns, smp_processor_id()) >> CYC2NS_SCALE_FACTOR; |
688340ea JF |
49 | } |
50 | ||
53d517cd GC |
51 | static inline unsigned long long cycles_2_ns(unsigned long long cyc) |
52 | { | |
53 | unsigned long long ns; | |
54 | unsigned long flags; | |
55 | ||
56 | local_irq_save(flags); | |
57 | ns = __cycles_2_ns(cyc); | |
58 | local_irq_restore(flags); | |
59 | ||
60 | return ns; | |
61 | } | |
688340ea | 62 | |
1da177e4 | 63 | #endif |