eeprom: More consistent symbol names
[linux-2.6] / arch / x86 / lib / delay.c
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  *      Copyright (C) 2008 Jiri Hladky <hladky _dot_ jiri _at_ gmail _dot_ com>
7  *
8  *      The __delay function must _NOT_ be inlined as its execution time
9  *      depends wildly on alignment on many x86 processors. The additional
10  *      jump magic is needed to get the timing stable on all the CPU's
11  *      we have to worry about.
12  */
13
14 #include <linux/module.h>
15 #include <linux/sched.h>
16 #include <linux/timex.h>
17 #include <linux/preempt.h>
18 #include <linux/delay.h>
19 #include <linux/init.h>
20
21 #include <asm/processor.h>
22 #include <asm/delay.h>
23 #include <asm/timer.h>
24
25 #ifdef CONFIG_SMP
26 # include <asm/smp.h>
27 #endif
28
29 /* simple loop based delay: */
30 static void delay_loop(unsigned long loops)
31 {
32         asm volatile(
33                 "       test %0,%0      \n"
34                 "       jz 3f           \n"
35                 "       jmp 1f          \n"
36
37                 ".align 16              \n"
38                 "1:     jmp 2f          \n"
39
40                 ".align 16              \n"
41                 "2:     dec %0          \n"
42                 "       jnz 2b          \n"
43                 "3:     dec %0          \n"
44
45                 : /* we don't need output */
46                 :"a" (loops)
47         );
48 }
49
50 /* TSC based delay: */
51 static void delay_tsc(unsigned long loops)
52 {
53         unsigned long bclock, now;
54         int cpu;
55
56         preempt_disable();
57         cpu = smp_processor_id();
58         rdtscl(bclock);
59         for (;;) {
60                 rdtscl(now);
61                 if ((now - bclock) >= loops)
62                         break;
63
64                 /* Allow RT tasks to run */
65                 preempt_enable();
66                 rep_nop();
67                 preempt_disable();
68
69                 /*
70                  * It is possible that we moved to another CPU, and
71                  * since TSC's are per-cpu we need to calculate
72                  * that. The delay must guarantee that we wait "at
73                  * least" the amount of time. Being moved to another
74                  * CPU could make the wait longer but we just need to
75                  * make sure we waited long enough. Rebalance the
76                  * counter for this CPU.
77                  */
78                 if (unlikely(cpu != smp_processor_id())) {
79                         loops -= (now - bclock);
80                         cpu = smp_processor_id();
81                         rdtscl(bclock);
82                 }
83         }
84         preempt_enable();
85 }
86
87 /*
88  * Since we calibrate only once at boot, this
89  * function should be set once at boot and not changed
90  */
91 static void (*delay_fn)(unsigned long) = delay_loop;
92
93 void use_tsc_delay(void)
94 {
95         delay_fn = delay_tsc;
96 }
97
98 int __devinit read_current_timer(unsigned long *timer_val)
99 {
100         if (delay_fn == delay_tsc) {
101                 rdtscll(*timer_val);
102                 return 0;
103         }
104         return -1;
105 }
106
107 void __delay(unsigned long loops)
108 {
109         delay_fn(loops);
110 }
111 EXPORT_SYMBOL(__delay);
112
113 inline void __const_udelay(unsigned long xloops)
114 {
115         int d0;
116
117         xloops *= 4;
118         asm("mull %%edx"
119                 :"=d" (xloops), "=&a" (d0)
120                 :"1" (xloops), "0"
121                 (cpu_data(raw_smp_processor_id()).loops_per_jiffy * (HZ/4)));
122
123         __delay(++xloops);
124 }
125 EXPORT_SYMBOL(__const_udelay);
126
127 void __udelay(unsigned long usecs)
128 {
129         __const_udelay(usecs * 0x000010c7); /* 2**32 / 1000000 (rounded up) */
130 }
131 EXPORT_SYMBOL(__udelay);
132
133 void __ndelay(unsigned long nsecs)
134 {
135         __const_udelay(nsecs * 0x00005); /* 2**32 / 1000000000 (rounded up) */
136 }
137 EXPORT_SYMBOL(__ndelay);