[mirror_ubuntu-jammy-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;

	preempt_disable();		/* TSC's are per-cpu */
	rdtscl(bclock);
	do {
		rep_nop();
		rdtscl(now);
	} while ((now-bclock) < loops);
	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;
	47
35d5d08a	48	preempt_disable(); /* TSC's are per-cpu */
6f84fa2f JS	49	rdtscl(bclock);
	50	do {
	51	rep_nop();
	52	rdtscl(now);
	53	} while ((now-bclock) < loops);
35d5d08a	54	preempt_enable();
6f84fa2f JS	55	}
	56
	57	/*
	58	* Since we calibrate only once at boot, this
	59	* function should be set once at boot and not changed
	60	*/
	61	static void (*delay_fn)(unsigned long) = delay_loop;
	62
	63	void use_tsc_delay(void)
	64	{
	65	delay_fn = delay_tsc;
	66	}
	67
941e492b	68	int __devinit read_current_timer(unsigned long *timer_val)
6f84fa2f JS	69	{
	70	if (delay_fn == delay_tsc) {
	71	rdtscl(*timer_val);
	72	return 0;
	73	}
	74	return -1;
	75	}
1da177e4 LT	76
	77	void __delay(unsigned long loops)
	78	{
6f84fa2f	79	delay_fn(loops);
1da177e4 LT	80	}
	81
	82	inline void __const_udelay(unsigned long xloops)
	83	{
	84	int d0;
6f84fa2f	85
1da177e4 LT	86	xloops *= 4;
	87	__asm__("mull %0"
	88	:"=d" (xloops), "=&a" (d0)
6f84fa2f	89	:"1" (xloops), "0"
92cb7612	90	(cpu_data(raw_smp_processor_id()).loops_per_jiffy * (HZ/4)));
6f84fa2f JS	91
6f84fa2f JS	92	__delay(++xloops);
1da177e4 LT	93	}
	94
	95	void __udelay(unsigned long usecs)
	96	{
6f84fa2f	97	__const_udelay(usecs * 0x000010c7); /* 2*32 / 1000000 (rounded up) /
1da177e4 LT	98	}
	99
	100	void __ndelay(unsigned long nsecs)
	101	{
6f84fa2f	102	__const_udelay(nsecs * 0x00005); /* 2*32 / 1000000000 (rounded up) /
1da177e4	103	}
129f6946 AD	104
	105	EXPORT_SYMBOL(__delay);
	106	EXPORT_SYMBOL(__const_udelay);
	107	EXPORT_SYMBOL(__udelay);
	108	EXPORT_SYMBOL(__ndelay);