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