Linux 2.6.26.3
[linux/fpc-iii.git] / arch / x86 / lib / delay_32.c
blobd710f2d167bb49505e56ed4c0e9c5cc91a52546e
1 /*
2 * Precise Delay Loops for i386
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. The additional
9 * jump magic is needed to get the timing stable on all the CPU's
10 * we have to worry about.
13 #include <linux/module.h>
14 #include <linux/sched.h>
15 #include <linux/timex.h>
16 #include <linux/preempt.h>
17 #include <linux/delay.h>
18 #include <linux/init.h>
20 #include <asm/processor.h>
21 #include <asm/delay.h>
22 #include <asm/timer.h>
24 #ifdef CONFIG_SMP
25 # include <asm/smp.h>
26 #endif
28 /* simple loop based delay: */
29 static void delay_loop(unsigned long loops)
31 int d0;
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));
43 /* TSC based delay: */
44 static void delay_tsc(unsigned long loops)
46 unsigned long bclock, now;
47 int cpu;
49 preempt_disable();
50 cpu = smp_processor_id();
51 rdtscl(bclock);
52 for (;;) {
53 rdtscl(now);
54 if ((now - bclock) >= loops)
55 break;
57 /* Allow RT tasks to run */
58 preempt_enable();
59 rep_nop();
60 preempt_disable();
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.
71 if (unlikely(cpu != smp_processor_id())) {
72 loops -= (now - bclock);
73 cpu = smp_processor_id();
74 rdtscl(bclock);
77 preempt_enable();
81 * Since we calibrate only once at boot, this
82 * function should be set once at boot and not changed
84 static void (*delay_fn)(unsigned long) = delay_loop;
86 void use_tsc_delay(void)
88 delay_fn = delay_tsc;
91 int __devinit read_current_timer(unsigned long *timer_val)
93 if (delay_fn == delay_tsc) {
94 rdtscl(*timer_val);
95 return 0;
97 return -1;
100 void __delay(unsigned long loops)
102 delay_fn(loops);
105 inline void __const_udelay(unsigned long xloops)
107 int d0;
109 xloops *= 4;
110 __asm__("mull %0"
111 :"=d" (xloops), "=&a" (d0)
112 :"1" (xloops), "0"
113 (cpu_data(raw_smp_processor_id()).loops_per_jiffy * (HZ/4)));
115 __delay(++xloops);
118 void __udelay(unsigned long usecs)
120 __const_udelay(usecs * 0x000010c7); /* 2**32 / 1000000 (rounded up) */
123 void __ndelay(unsigned long nsecs)
125 __const_udelay(nsecs * 0x00005); /* 2**32 / 1000000000 (rounded up) */
128 EXPORT_SYMBOL(__delay);
129 EXPORT_SYMBOL(__const_udelay);
130 EXPORT_SYMBOL(__udelay);
131 EXPORT_SYMBOL(__ndelay);