2 * Precise Delay Loops for x86-64
4 * Copyright (C) 1993 Linus Torvalds
5 * Copyright (C) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
7 * The __delay function must _NOT_ be inlined as its execution time
8 * depends wildly on alignment on many x86 processors.
11 #include <linux/module.h>
12 #include <linux/sched.h>
13 #include <linux/preempt.h>
14 #include <linux/delay.h>
16 #include <asm/delay.h>
23 int read_current_timer(unsigned long *timer_value)
25 rdtscll(*timer_value);
29 void __delay(unsigned long loops)
33 preempt_disable(); /* TSC's are pre-cpu */
39 while ((now-bclock) < loops);
42 EXPORT_SYMBOL(__delay);
44 inline void __const_udelay(unsigned long xloops)
46 __delay(((xloops * HZ *
47 cpu_data(raw_smp_processor_id()).loops_per_jiffy) >> 32) + 1);
49 EXPORT_SYMBOL(__const_udelay);
51 void __udelay(unsigned long usecs)
53 __const_udelay(usecs * 0x000010c7); /* 2**32 / 1000000 (rounded up) */
55 EXPORT_SYMBOL(__udelay);
57 void __ndelay(unsigned long nsecs)
59 __const_udelay(nsecs * 0x00005); /* 2**32 / 1000000000 (rounded up) */
61 EXPORT_SYMBOL(__ndelay);