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7#include <linux/jiffies.h>
8#include <linux/delay.h>
9#include <linux/init.h>
10#include <linux/timex.h>
11#include <linux/smp.h>
12
13unsigned long lpj_fine;
14unsigned long preset_lpj;
15static int __init lpj_setup(char *str)
16{
17 preset_lpj = simple_strtoul(str,NULL,0);
18 return 1;
19}
20
21__setup("lpj=", lpj_setup);
22
23#ifdef ARCH_HAS_READ_CURRENT_TIMER
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29
30#define DELAY_CALIBRATION_TICKS ((HZ < 100) ? 1 : (HZ/100))
31#define MAX_DIRECT_CALIBRATION_RETRIES 5
32
33static unsigned long __cpuinit calibrate_delay_direct(void)
34{
35 unsigned long pre_start, start, post_start;
36 unsigned long pre_end, end, post_end;
37 unsigned long start_jiffies;
38 unsigned long timer_rate_min, timer_rate_max;
39 unsigned long good_timer_sum = 0;
40 unsigned long good_timer_count = 0;
41 int i;
42
43 if (read_current_timer(&pre_start) < 0 )
44 return 0;
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64
65 for (i = 0; i < MAX_DIRECT_CALIBRATION_RETRIES; i++) {
66 pre_start = 0;
67 read_current_timer(&start);
68 start_jiffies = jiffies;
69 while (time_before_eq(jiffies, start_jiffies + 1)) {
70 pre_start = start;
71 read_current_timer(&start);
72 }
73 read_current_timer(&post_start);
74
75 pre_end = 0;
76 end = post_start;
77 while (time_before_eq(jiffies, start_jiffies + 1 +
78 DELAY_CALIBRATION_TICKS)) {
79 pre_end = end;
80 read_current_timer(&end);
81 }
82 read_current_timer(&post_end);
83
84 timer_rate_max = (post_end - pre_start) /
85 DELAY_CALIBRATION_TICKS;
86 timer_rate_min = (pre_end - post_start) /
87 DELAY_CALIBRATION_TICKS;
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91
92
93 if (pre_start != 0 && pre_end != 0 &&
94 (timer_rate_max - timer_rate_min) < (timer_rate_max >> 3)) {
95 good_timer_count++;
96 good_timer_sum += timer_rate_max;
97 }
98 }
99
100 if (good_timer_count)
101 return (good_timer_sum/good_timer_count);
102
103 printk(KERN_WARNING "calibrate_delay_direct() failed to get a good "
104 "estimate for loops_per_jiffy.\nProbably due to long platform interrupts. Consider using \"lpj=\" boot option.\n");
105 return 0;
106}
107#else
108static unsigned long __cpuinit calibrate_delay_direct(void) {return 0;}
109#endif
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119
120#define LPS_PREC 8
121
122static unsigned long __cpuinit calibrate_delay_converge(void)
123{
124
125 unsigned long lpj, lpj_base, ticks, loopadd, loopadd_base, chop_limit;
126 int trials = 0, band = 0, trial_in_band = 0;
127
128 lpj = (1<<12);
129
130
131 ticks = jiffies;
132 while (ticks == jiffies)
133 ;
134
135 ticks = jiffies;
136 do {
137 if (++trial_in_band == (1<<band)) {
138 ++band;
139 trial_in_band = 0;
140 }
141 __delay(lpj * band);
142 trials += band;
143 } while (ticks == jiffies);
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148 trials -= band;
149 loopadd_base = lpj * band;
150 lpj_base = lpj * trials;
151
152recalibrate:
153 lpj = lpj_base;
154 loopadd = loopadd_base;
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160 chop_limit = lpj >> LPS_PREC;
161 while (loopadd > chop_limit) {
162 lpj += loopadd;
163 ticks = jiffies;
164 while (ticks == jiffies)
165 ;
166 ticks = jiffies;
167 __delay(lpj);
168 if (jiffies != ticks)
169 lpj -= loopadd;
170 loopadd >>= 1;
171 }
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176
177 if (lpj + loopadd * 2 == lpj_base + loopadd_base * 2) {
178 lpj_base = lpj;
179 loopadd_base <<= 2;
180 goto recalibrate;
181 }
182
183 return lpj;
184}
185
186void __cpuinit calibrate_delay(void)
187{
188 static bool printed;
189
190 if (preset_lpj) {
191 loops_per_jiffy = preset_lpj;
192 if (!printed)
193 pr_info("Calibrating delay loop (skipped) "
194 "preset value.. ");
195 } else if ((!printed) && lpj_fine) {
196 loops_per_jiffy = lpj_fine;
197 pr_info("Calibrating delay loop (skipped), "
198 "value calculated using timer frequency.. ");
199 } else if ((loops_per_jiffy = calibrate_delay_direct()) != 0) {
200 if (!printed)
201 pr_info("Calibrating delay using timer "
202 "specific routine.. ");
203 } else {
204 if (!printed)
205 pr_info("Calibrating delay loop... ");
206 loops_per_jiffy = calibrate_delay_converge();
207 }
208 if (!printed)
209 pr_cont("%lu.%02lu BogoMIPS (lpj=%lu)\n",
210 loops_per_jiffy/(500000/HZ),
211 (loops_per_jiffy/(5000/HZ)) % 100, loops_per_jiffy);
212
213 printed = true;
214}
215