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| 1 | /* calibrate.c: default delay calibration | |||
| 2 | * | |||
| 3 | * Excised from init/main.c | |||
| 4 | * Copyright (C) 1991, 1992 Linus Torvalds | |||
| 5 | */ | |||
| 6 | ||||
| 7 | #include <linux/sched.h> | |||
| 8 | #include <linux/delay.h> | |||
| 9 | #include <linux/init.h> | |||
| 10 | ||||
| 11 | #include <asm/timex.h> | |||
| 12 | ||||
| 13 | static unsigned long preset_lpj; | |||
| 0 | 0 | - | 14 | static int __init lpj_setup(char *str) |
| 15 | { | |||
| 16 | preset_lpj = simple_strtoul(str,NULL,0); | |||
| 0 | - | 17 | return 1; | |
| 18 | } | |||
| 19 | ||||
| 20 | __setup("lpj=", lpj_setup); | |||
| 21 | ||||
| 22 | #ifdef ARCH_HAS_READ_CURRENT_TIMER | |||
| 23 | ||||
| 24 | /* This routine uses the read_current_timer() routine and gets the | |||
| 25 | * loops per jiffy directly, instead of guessing it using delay(). | |||
| 26 | * Also, this code tries to handle non-maskable asynchronous events | |||
| 27 | * (like SMIs) | |||
| 28 | */ | |||
| 29 | #define DELAY_CALIBRATION_TICKS ((HZ < 100) ? 1 : (HZ/100)) | |||
| 30 | #define MAX_DIRECT_CALIBRATION_RETRIES 5 | |||
| 31 | ||||
| 3 | 0 | 32 | static unsigned long __devinit calibrate_delay_direct(void) | |
| 33 | { | |||
| 34 | unsigned long pre_start, start, post_start; | |||
| 35 | unsigned long pre_end, end, post_end; | |||
| 36 | unsigned long start_jiffies; | |||
| 37 | unsigned long tsc_rate_min, tsc_rate_max; | |||
| 38 | unsigned long good_tsc_sum = 0; | |||
| 39 | unsigned long good_tsc_count = 0; | |||
| 40 | int i; | |||
| 41 | ||||
| 0 | 3 | - | 42 | if (read_current_timer(&pre_start) < 0 ) |
| 0 | - | 43 | return 0; | |
| 44 | ||||
| 45 | /* | |||
| 46 | * A simple loop like | |||
| 47 | * while ( jiffies < start_jiffies+1) | |||
| 48 | * start = read_current_timer(); | |||
| 49 | * will not do. As we don't really know whether jiffy switch | |||
| 50 | * happened first or timer_value was read first. And some asynchronous | |||
| 51 | * event can happen between these two events introducing errors in lpj. | |||
| 52 | * | |||
| 53 | * So, we do | |||
| 54 | * 1. pre_start <- When we are sure that jiffy switch hasn't happened | |||
| 55 | * 2. check jiffy switch | |||
| 56 | * 3. start <- timer value before or after jiffy switch | |||
| 57 | * 4. post_start <- When we are sure that jiffy switch has happened | |||
| 58 | * | |||
| 59 | * Note, we don't know anything about order of 2 and 3. | |||
| 60 | * Now, by looking at post_start and pre_start difference, we can | |||
| 61 | * check whether any asynchronous event happened or not | |||
| 62 | */ | |||
| 63 | ||||
| 15 | 3 | 64 | for (i = 0; i < MAX_DIRECT_CALIBRATION_RETRIES; i++) { | |
| 65 | pre_start = 0; | |||
| 66 | read_current_timer(&start); | |||
| 67 | start_jiffies = jiffies; | |||
| 7688E3 | 15 | 68 | while (jiffies <= (start_jiffies + 1)) { | |
| 69 | pre_start = start; | |||
| 70 | read_current_timer(&start); | |||
| 71 | } | |||
| 72 | read_current_timer(&post_start); | |||
| 73 | ||||
| 74 | pre_end = 0; | |||
| 75 | end = post_start; | |||
| 76 | while (jiffies <= | |||
| 6948E3 | 15 | 77 | (start_jiffies + 1 + DELAY_CALIBRATION_TICKS)) { | |
| 0 | 6948E3 | - | 77 | ternary-?: ( 250 < 100 ) |
| 78 | pre_end = end; | |||
| 79 | read_current_timer(&end); | |||
| 80 | } | |||
| 81 | read_current_timer(&post_end); | |||
| 82 | ||||
| 83 | tsc_rate_max = (post_end - pre_start) / DELAY_CALIBRATION_TICKS; | |||
| 0 | 15 | - | 83 | ternary-?: ( 250 < 100 ) |
| 84 | tsc_rate_min = (pre_end - post_start) / DELAY_CALIBRATION_TICKS; | |||
| 0 | 15 | - | 84 | ternary-?: ( 250 < 100 ) |
| 85 | ||||
| 86 | /* | |||
| 87 | * If the upper limit and lower limit of the tsc_rate is | |||
| 88 | * >= 12.5% apart, redo calibration. | |||
| 89 | */ | |||
| 90 | if (pre_start != 0 && pre_end != 0 && | |||
| 15 | 0 | - | 91 | (tsc_rate_max - tsc_rate_min) < (tsc_rate_max >> 3)) { |
| 15 | 91 | T && T && T | ||
| 0 | - | 91 | T && T && F | |
| 0 | - | 91 | T && F && _ | |
| 0 | - | 91 | F && _ && _ | |
| 92 | good_tsc_count++; | |||
| 93 | good_tsc_sum += tsc_rate_max; | |||
| 94 | } | |||
| 95 | } | |||
| 96 | ||||
| 3 | 0 | - | 97 | if (good_tsc_count) |
| 3 | 98 | return (good_tsc_sum/good_tsc_count); | ||
| 99 | ||||
| 100 | printk(KERN_WARNING "calibrate_delay_direct() failed to get a good " | |||
| 101 | "estimate for loops_per_jiffy.\nProbably due to long platform interrupts. Consider using \"lpj=\" boot option.\n"); | |||
| 0 | - | 102 | return 0; | |
| 103 | } | |||
| 104 | #else | |||
| 105 | static unsigned long __devinit calibrate_delay_direct(void) {return 0;} | |||
| 106 | #endif | |||
| 107 | ||||
| 108 | /* | |||
| 109 | * This is the number of bits of precision for the loops_per_jiffy. Each | |||
| 110 | * bit takes on average 1.5/HZ seconds. This (like the original) is a little | |||
| 111 | * better than 1% | |||
| 112 | */ | |||
| 113 | #define LPS_PREC 8 | |||
| 114 | ||||
| 3 | 3 | 115 | void __devinit calibrate_delay(void) | |
| 116 | { | |||
| 117 | unsigned long ticks, loopbit; | |||
| 118 | int lps_precision = LPS_PREC; | |||
| 119 | ||||
| 0 | 3 | - | 120 | if (preset_lpj) { |
| 121 | loops_per_jiffy = preset_lpj; | |||
| 122 | printk("Calibrating delay loop (skipped)... " | |||
| 123 | "%lu.%02lu BogoMIPS preset\n", | |||
| 124 | loops_per_jiffy/(500000/HZ), | |||
| 125 | (loops_per_jiffy/(5000/HZ)) % 100); | |||
| 3 | 0 | - | 126 | } else if ((loops_per_jiffy = calibrate_delay_direct()) != 0) { |
| 127 | printk("Calibrating delay using timer specific routine.. "); | |||
| 128 | printk("%lu.%02lu BogoMIPS (lpj=%lu)\n", | |||
| 129 | loops_per_jiffy/(500000/HZ), | |||
| 130 | (loops_per_jiffy/(5000/HZ)) % 100, | |||
| 131 | loops_per_jiffy); | |||
| 132 | } else { | |||
| 133 | loops_per_jiffy = (1<<12); | |||
| 134 | ||||
| 135 | printk(KERN_DEBUG "Calibrating delay loop... "); | |||
| 0 | 0 | - | 136 | while ((loops_per_jiffy <<= 1) != 0) { |
| 137 | /* wait for "start of" clock tick */ | |||
| 138 | ticks = jiffies; | |||
| 0 | 0 | - | 139 | while (ticks == jiffies) |
| 140 | /* nothing */; | |||
| 141 | /* Go .. */ | |||
| 142 | ticks = jiffies; | |||
| 143 | __delay(loops_per_jiffy); | |||
| 144 | ticks = jiffies - ticks; | |||
| 0 | 0 | - | 145 | if (ticks) |
| 0 | - | 146 | break; | |
| 147 | } | |||
| 148 | ||||
| 149 | /* | |||
| 150 | * Do a binary approximation to get loops_per_jiffy set to | |||
| 151 | * equal one clock (up to lps_precision bits) | |||
| 152 | */ | |||
| 153 | loops_per_jiffy >>= 1; | |||
| 154 | loopbit = loops_per_jiffy; | |||
| 0 | 0 | - | 155 | while (lps_precision-- && (loopbit >>= 1)) { |
| 0 | - | 155 | T && (T) | |
| 0 | - | 155 | T && (F) | |
| 0 | - | 155 | F && (_) | |
| 156 | loops_per_jiffy |= loopbit; | |||
| 157 | ticks = jiffies; | |||
| 0 | 0 | - | 158 | while (ticks == jiffies) |
| 159 | /* nothing */; | |||
| 160 | ticks = jiffies; | |||
| 161 | __delay(loops_per_jiffy); | |||
| 0 | 0 | - | 162 | if (jiffies != ticks) /* longer than 1 tick */ |
| 163 | loops_per_jiffy &= ~loopbit; | |||
| 164 | } | |||
| 165 | ||||
| 166 | /* Round the value and print it */ | |||
| 167 | printk("%lu.%02lu BogoMIPS (lpj=%lu)\n", | |||
| 168 | loops_per_jiffy/(500000/HZ), | |||
| 169 | (loops_per_jiffy/(5000/HZ)) % 100, | |||
| 170 | loops_per_jiffy); | |||
| 171 | } | |||
| 172 | ||||
| 173 | } | |||
| ***TER 37% (18/49) of SOURCE FILE calibrate.c | ||||