x86: Use {push,pop}_cfi in more places
[linux-3.10.git] / 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         rdtsc_barrier();
59         rdtscl(bclock);
60         for (;;) {
61                 rdtsc_barrier();
62                 rdtscl(now);
63                 if ((now - bclock) >= loops)
64                         break;
65
66                 /* Allow RT tasks to run */
67                 preempt_enable();
68                 rep_nop();
69                 preempt_disable();
70
71                 /*
72                  * It is possible that we moved to another CPU, and
73                  * since TSC's are per-cpu we need to calculate
74                  * that. The delay must guarantee that we wait "at
75                  * least" the amount of time. Being moved to another
76                  * CPU could make the wait longer but we just need to
77                  * make sure we waited long enough. Rebalance the
78                  * counter for this CPU.
79                  */
80                 if (unlikely(cpu != smp_processor_id())) {
81                         loops -= (now - bclock);
82                         cpu = smp_processor_id();
83                         rdtsc_barrier();
84                         rdtscl(bclock);
85                 }
86         }
87         preempt_enable();
88 }
89
90 /*
91  * Since we calibrate only once at boot, this
92  * function should be set once at boot and not changed
93  */
94 static void (*delay_fn)(unsigned long) = delay_loop;
95
96 void use_tsc_delay(void)
97 {
98         delay_fn = delay_tsc;
99 }
100
101 int __devinit read_current_timer(unsigned long *timer_val)
102 {
103         if (delay_fn == delay_tsc) {
104                 rdtscll(*timer_val);
105                 return 0;
106         }
107         return -1;
108 }
109
110 void __delay(unsigned long loops)
111 {
112         delay_fn(loops);
113 }
114 EXPORT_SYMBOL(__delay);
115
116 inline void __const_udelay(unsigned long xloops)
117 {
118         int d0;
119
120         xloops *= 4;
121         asm("mull %%edx"
122                 :"=d" (xloops), "=&a" (d0)
123                 :"1" (xloops), "0"
124                 (this_cpu_read(cpu_info.loops_per_jiffy) * (HZ/4)));
125
126         __delay(++xloops);
127 }
128 EXPORT_SYMBOL(__const_udelay);
129
130 void __udelay(unsigned long usecs)
131 {
132         __const_udelay(usecs * 0x000010c7); /* 2**32 / 1000000 (rounded up) */
133 }
134 EXPORT_SYMBOL(__udelay);
135
136 void __ndelay(unsigned long nsecs)
137 {
138         __const_udelay(nsecs * 0x00005); /* 2**32 / 1000000000 (rounded up) */
139 }
140 EXPORT_SYMBOL(__ndelay);