blob: a81195eaa2b3dc3d4378d523ee79c256ca752e52 (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
|
#ifndef _ASM_X86_TIMER_H
#define _ASM_X86_TIMER_H
#include <linux/init.h>
#include <linux/pm.h>
#include <linux/percpu.h>
#include <linux/interrupt.h>
#define TICK_SIZE (tick_nsec / 1000)
unsigned long long native_sched_clock(void);
unsigned long native_calibrate_tsc(void);
#ifdef CONFIG_X86_32
extern int timer_ack;
extern int recalibrate_cpu_khz(void);
extern irqreturn_t timer_interrupt(int irq, void *dev_id);
#endif /* CONFIG_X86_32 */
extern int no_timer_check;
#ifndef CONFIG_PARAVIRT
#define calibrate_tsc() native_calibrate_tsc()
#endif
/* Accelerators for sched_clock()
* convert from cycles(64bits) => nanoseconds (64bits)
* basic equation:
* ns = cycles / (freq / ns_per_sec)
* ns = cycles * (ns_per_sec / freq)
* ns = cycles * (10^9 / (cpu_khz * 10^3))
* ns = cycles * (10^6 / cpu_khz)
*
* Then we use scaling math (suggested by george@mvista.com) to get:
* ns = cycles * (10^6 * SC / cpu_khz) / SC
* ns = cycles * cyc2ns_scale / SC
*
* And since SC is a constant power of two, we can convert the div
* into a shift.
*
* We can use khz divisor instead of mhz to keep a better precision, since
* cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
* (mathieu.desnoyers@polymtl.ca)
*
* -johnstul@us.ibm.com "math is hard, lets go shopping!"
*/
DECLARE_PER_CPU(unsigned long, cyc2ns);
#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
static inline unsigned long long __cycles_2_ns(unsigned long long cyc)
{
return cyc * per_cpu(cyc2ns, smp_processor_id()) >> CYC2NS_SCALE_FACTOR;
}
static inline unsigned long long cycles_2_ns(unsigned long long cyc)
{
unsigned long long ns;
unsigned long flags;
local_irq_save(flags);
ns = __cycles_2_ns(cyc);
local_irq_restore(flags);
return ns;
}
#endif /* _ASM_X86_TIMER_H */
|
