[mirror_ubuntu-artful-kernel.git] / arch / x86 / lib / delay_32.c

/*
 *	Precise Delay Loops for i386
 *
 *	Copyright (C) 1993 Linus Torvalds
 *	Copyright (C) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
 *
 *	The __delay function must _NOT_ be inlined as its execution time
 *	depends wildly on alignment on many x86 processors. The additional
 *	jump magic is needed to get the timing stable on all the CPU's
 *	we have to worry about.
 */

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/timex.h>
#include <linux/preempt.h>
#include <linux/delay.h>
#include <linux/init.h>

#include <asm/processor.h>
#include <asm/delay.h>
#include <asm/timer.h>

#ifdef CONFIG_SMP
# include <asm/smp.h>
#endif

/* simple loop based delay: */
static void delay_loop(unsigned long loops)
{
	int d0;

	__asm__ __volatile__(
		"\tjmp 1f\n"
		".align 16\n"
		"1:\tjmp 2f\n"
		".align 16\n"
		"2:\tdecl %0\n\tjns 2b"
		:"=&a" (d0)
		:"0" (loops));
}

/* TSC based delay: */
static void delay_tsc(unsigned long loops)
{
	unsigned long bclock, now;
	int cpu;

	preempt_disable();
	cpu = smp_processor_id();
	rdtscl(bclock);
	for (;;) {
		rdtscl(now);
		if ((now - bclock) >= loops)
			break;

		/* Allow RT tasks to run */
		preempt_enable();
		rep_nop();
		preempt_disable();

		/*
		 * It is possible that we moved to another CPU, and
		 * since TSC's are per-cpu we need to calculate
		 * that. The delay must guarantee that we wait "at
		 * least" the amount of time. Being moved to another
		 * CPU could make the wait longer but we just need to
		 * make sure we waited long enough. Rebalance the
		 * counter for this CPU.
		 */
		if (unlikely(cpu != smp_processor_id())) {
			loops -= (now - bclock);
			cpu = smp_processor_id();
			rdtscl(bclock);
		}
	}
	preempt_enable();
}

/*
 * Since we calibrate only once at boot, this
 * function should be set once at boot and not changed
 */
static void (*delay_fn)(unsigned long) = delay_loop;

void use_tsc_delay(void)
{
	delay_fn = delay_tsc;
}

int __devinit read_current_timer(unsigned long *timer_val)
{
	if (delay_fn == delay_tsc) {
		rdtscl(*timer_val);
		return 0;
	}
	return -1;
}

void __delay(unsigned long loops)
{
	delay_fn(loops);
}

inline void __const_udelay(unsigned long xloops)
{
	int d0;

	xloops *= 4;
	__asm__("mull %0"
		:"=d" (xloops), "=&a" (d0)
		:"1" (xloops), "0"
		(cpu_data(raw_smp_processor_id()).loops_per_jiffy * (HZ/4)));

	__delay(++xloops);
}

void __udelay(unsigned long usecs)
{
	__const_udelay(usecs * 0x000010c7); /* 2**32 / 1000000 (rounded up) */
}

void __ndelay(unsigned long nsecs)
{
	__const_udelay(nsecs * 0x00005); /* 2**32 / 1000000000 (rounded up) */
}

EXPORT_SYMBOL(__delay);
EXPORT_SYMBOL(__const_udelay);
EXPORT_SYMBOL(__udelay);
EXPORT_SYMBOL(__ndelay);
Commit	Line	Data
1da177e4 LT	1	/*
	2	* Precise Delay Loops for i386
	3	*
	4	* Copyright (C) 1993 Linus Torvalds
	5	* Copyright (C) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
	6	*
	7	* The __delay function must _NOT_ be inlined as its execution time
	8	* depends wildly on alignment on many x86 processors. The additional
	9	* jump magic is needed to get the timing stable on all the CPU's
	10	* we have to worry about.
	11	*/
	12
6f84fa2f	13	#include <linux/module.h>
1da177e4	14	#include <linux/sched.h>
941e492b	15	#include <linux/timex.h>
35d5d08a	16	#include <linux/preempt.h>
1da177e4	17	#include <linux/delay.h>
941e492b	18	#include <linux/init.h>
6f84fa2f	19
1da177e4 LT	20	#include <asm/processor.h>
	21	#include <asm/delay.h>
	22	#include <asm/timer.h>
	23
	24	#ifdef CONFIG_SMP
6f84fa2f	25	# include <asm/smp.h>
1da177e4 LT	26	#endif
1da177e4 LT	27
6f84fa2f JS	28	/* simple loop based delay: */
	29	static void delay_loop(unsigned long loops)
	30	{
	31	int d0;
	32
	33	__asm__ __volatile__(
	34	"\tjmp 1f\n"
	35	".align 16\n"
	36	"1:\tjmp 2f\n"
	37	".align 16\n"
	38	"2:\tdecl %0\n\tjns 2b"
	39	:"=&a" (d0)
	40	:"0" (loops));
	41	}
	42
	43	/* TSC based delay: */
	44	static void delay_tsc(unsigned long loops)
	45	{
	46	unsigned long bclock, now;
5c1ea082	47	int cpu;
6f84fa2f	48
5c1ea082 SR	49	preempt_disable();
5c1ea082 SR	50	cpu = smp_processor_id();
6f84fa2f	51	rdtscl(bclock);
5c1ea082	52	for (;;) {
6f84fa2f	53	rdtscl(now);
5c1ea082 SR	54	if ((now - bclock) >= loops)
	55	break;
	56
	57	/* Allow RT tasks to run */
	58	preempt_enable();
	59	rep_nop();
	60	preempt_disable();
	61
	62	/*
	63	* It is possible that we moved to another CPU, and
	64	* since TSC's are per-cpu we need to calculate
	65	* that. The delay must guarantee that we wait "at
	66	* least" the amount of time. Being moved to another
	67	* CPU could make the wait longer but we just need to
	68	* make sure we waited long enough. Rebalance the
	69	* counter for this CPU.
	70	*/
	71	if (unlikely(cpu != smp_processor_id())) {
	72	loops -= (now - bclock);
	73	cpu = smp_processor_id();
	74	rdtscl(bclock);
	75	}
	76	}
35d5d08a	77	preempt_enable();
6f84fa2f JS	78	}
	79
	80	/*
	81	* Since we calibrate only once at boot, this
	82	* function should be set once at boot and not changed
	83	*/
	84	static void (*delay_fn)(unsigned long) = delay_loop;
	85
	86	void use_tsc_delay(void)
	87	{
	88	delay_fn = delay_tsc;
	89	}
	90
941e492b	91	int __devinit read_current_timer(unsigned long *timer_val)
6f84fa2f JS	92	{
	93	if (delay_fn == delay_tsc) {
	94	rdtscl(*timer_val);
	95	return 0;
	96	}
	97	return -1;
	98	}
1da177e4 LT	99
	100	void __delay(unsigned long loops)
	101	{
6f84fa2f	102	delay_fn(loops);
1da177e4 LT	103	}
	104
	105	inline void __const_udelay(unsigned long xloops)
	106	{
	107	int d0;
6f84fa2f	108
1da177e4 LT	109	xloops *= 4;
	110	__asm__("mull %0"
	111	:"=d" (xloops), "=&a" (d0)
6f84fa2f	112	:"1" (xloops), "0"
92cb7612	113	(cpu_data(raw_smp_processor_id()).loops_per_jiffy * (HZ/4)));
6f84fa2f JS	114
6f84fa2f JS	115	__delay(++xloops);
1da177e4 LT	116	}
	117
	118	void __udelay(unsigned long usecs)
	119	{
6f84fa2f	120	__const_udelay(usecs * 0x000010c7); /* 2*32 / 1000000 (rounded up) /
1da177e4 LT	121	}
	122
	123	void __ndelay(unsigned long nsecs)
	124	{
6f84fa2f	125	__const_udelay(nsecs * 0x00005); /* 2*32 / 1000000000 (rounded up) /
1da177e4	126	}
129f6946 AD	127
	128	EXPORT_SYMBOL(__delay);
	129	EXPORT_SYMBOL(__const_udelay);
	130	EXPORT_SYMBOL(__udelay);
	131	EXPORT_SYMBOL(__ndelay);