[GitHub/mt8127/android_kernel_alcatel_ttab.git] / arch / x86 / include / asm / timer.h

#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);
extern int recalibrate_cpu_khz(void);

extern int no_timer_check;

/* 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!"
 *
 * In:
 *
 * ns = cycles * cyc2ns_scale / SC
 *
 * Although we may still have enough bits to store the value of ns,
 * in some cases, we may not have enough bits to store cycles * cyc2ns_scale,
 * leading to an incorrect result.
 *
 * To avoid this, we can decompose 'cycles' into quotient and remainder
 * of division by SC.  Then,
 *
 * ns = (quot * SC + rem) * cyc2ns_scale / SC
 *    = quot * cyc2ns_scale + (rem * cyc2ns_scale) / SC
 *
 *			- sqazi@google.com
 */

DECLARE_PER_CPU(unsigned long, cyc2ns);
DECLARE_PER_CPU(unsigned long long, cyc2ns_offset);

#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */

static inline unsigned long long __cycles_2_ns(unsigned long long cyc)
{
	unsigned long long quot;
	unsigned long long rem;
	int cpu = smp_processor_id();
	unsigned long long ns = per_cpu(cyc2ns_offset, cpu);
	quot = (cyc >> CYC2NS_SCALE_FACTOR);
	rem = cyc & ((1ULL << CYC2NS_SCALE_FACTOR) - 1);
	ns += quot * per_cpu(cyc2ns, cpu) +
		((rem * per_cpu(cyc2ns, cpu)) >> CYC2NS_SCALE_FACTOR);
	return ns;
}

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 */
Commit	Line	Data
1965aae3 PA	1	#ifndef _ASM_X86_TIMER_H
1965aae3 PA	2	#define _ASM_X86_TIMER_H
1da177e4	3	#include <linux/init.h>
c3c433e4	4	#include <linux/pm.h>
53d517cd	5	#include <linux/percpu.h>
8e6dafd6	6	#include <linux/interrupt.h>
1da177e4	7
1da177e4	8	#define TICK_SIZE (tick_nsec / 1000)
6cb9a835	9
6cb9a835	10	unsigned long long native_sched_clock(void);
64fcbac1	11	extern int recalibrate_cpu_khz(void);
6cb9a835	12
cc038491	13	extern int no_timer_check;
1da177e4	14
53d517cd	15	/* Accelerators for sched_clock()
688340ea JF	16	* convert from cycles(64bits) => nanoseconds (64bits)
	17	* basic equation:
	18	* ns = cycles / (freq / ns_per_sec)
	19	* ns = cycles * (ns_per_sec / freq)
	20	* ns = cycles * (10^9 / (cpu_khz * 10^3))
	21	* ns = cycles * (10^6 / cpu_khz)
	22	*
	23	* Then we use scaling math (suggested by george@mvista.com) to get:
	24	* ns = cycles * (10^6 * SC / cpu_khz) / SC
	25	* ns = cycles * cyc2ns_scale / SC
	26	*
	27	* And since SC is a constant power of two, we can convert the div
	28	* into a shift.
	29	*
53d517cd	30	* We can use khz divisor instead of mhz to keep a better precision, since
688340ea JF	31	* cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
	32	* (mathieu.desnoyers@polymtl.ca)
	33	*
	34	* -johnstul@us.ibm.com "math is hard, lets go shopping!"
4cecf6d4 SQ	35	*
	36	* In:
	37	*
	38	* ns = cycles * cyc2ns_scale / SC
	39	*
	40	* Although we may still have enough bits to store the value of ns,
	41	* in some cases, we may not have enough bits to store cycles * cyc2ns_scale,
	42	* leading to an incorrect result.
	43	*
	44	* To avoid this, we can decompose 'cycles' into quotient and remainder
	45	* of division by SC. Then,
	46	*
	47	* ns = (quot * SC + rem) * cyc2ns_scale / SC
	48	* = quot * cyc2ns_scale + (rem * cyc2ns_scale) / SC
	49	*
	50	* - sqazi@google.com
688340ea	51	*/
53d517cd GC	52
53d517cd GC	53	DECLARE_PER_CPU(unsigned long, cyc2ns);
84599f8a	54	DECLARE_PER_CPU(unsigned long long, cyc2ns_offset);
688340ea JF	55
	56	#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
	57
53d517cd	58	static inline unsigned long long __cycles_2_ns(unsigned long long cyc)
688340ea	59	{
4cecf6d4 SQ	60	unsigned long long quot;
4cecf6d4 SQ	61	unsigned long long rem;
84599f8a PZ	62	int cpu = smp_processor_id();
84599f8a PZ	63	unsigned long long ns = per_cpu(cyc2ns_offset, cpu);
4cecf6d4 SQ	64	quot = (cyc >> CYC2NS_SCALE_FACTOR);
	65	rem = cyc & ((1ULL << CYC2NS_SCALE_FACTOR) - 1);
	66	ns += quot * per_cpu(cyc2ns, cpu) +
	67	((rem * per_cpu(cyc2ns, cpu)) >> CYC2NS_SCALE_FACTOR);
84599f8a	68	return ns;
688340ea JF	69	}
688340ea JF	70
53d517cd GC	71	static inline unsigned long long cycles_2_ns(unsigned long long cyc)
	72	{
	73	unsigned long long ns;
	74	unsigned long flags;
	75
	76	local_irq_save(flags);
	77	ns = __cycles_2_ns(cyc);
	78	local_irq_restore(flags);
	79
	80	return ns;
	81	}
688340ea	82
1965aae3	83	#endif /* _ASM_X86_TIMER_H */