diff options
Diffstat (limited to 'init')
| -rw-r--r-- | init/calibrate.c | 75 |
1 files changed, 69 insertions, 6 deletions
diff --git a/init/calibrate.c b/init/calibrate.c index 76ac9194cbc4..cfd7000c9d71 100644 --- a/init/calibrate.c +++ b/init/calibrate.c @@ -38,6 +38,9 @@ static unsigned long __cpuinit calibrate_delay_direct(void) unsigned long timer_rate_min, timer_rate_max; unsigned long good_timer_sum = 0; unsigned long good_timer_count = 0; + unsigned long measured_times[MAX_DIRECT_CALIBRATION_RETRIES]; + int max = -1; /* index of measured_times with max/min values or not set */ + int min = -1; int i; if (read_current_timer(&pre_start) < 0 ) @@ -90,18 +93,78 @@ static unsigned long __cpuinit calibrate_delay_direct(void) * If the upper limit and lower limit of the timer_rate is * >= 12.5% apart, redo calibration. */ - if (pre_start != 0 && pre_end != 0 && + printk(KERN_DEBUG "calibrate_delay_direct() timer_rate_max=%lu " + "timer_rate_min=%lu pre_start=%lu pre_end=%lu\n", + timer_rate_max, timer_rate_min, pre_start, pre_end); + if (start >= post_end) + printk(KERN_NOTICE "calibrate_delay_direct() ignoring " + "timer_rate as we had a TSC wrap around" + " start=%lu >=post_end=%lu\n", + start, post_end); + if (start < post_end && pre_start != 0 && pre_end != 0 && (timer_rate_max - timer_rate_min) < (timer_rate_max >> 3)) { good_timer_count++; good_timer_sum += timer_rate_max; - } + measured_times[i] = timer_rate_max; + if (max < 0 || timer_rate_max > measured_times[max]) + max = i; + if (min < 0 || timer_rate_max < measured_times[min]) + min = i; + } else + measured_times[i] = 0; + } - if (good_timer_count) - return (good_timer_sum/good_timer_count); + /* + * Find the maximum & minimum - if they differ too much throw out the + * one with the largest difference from the mean and try again... + */ + while (good_timer_count > 1) { + unsigned long estimate; + unsigned long maxdiff; + + /* compute the estimate */ + estimate = (good_timer_sum/good_timer_count); + maxdiff = estimate >> 3; + + /* if range is within 12% let's take it */ + if ((measured_times[max] - measured_times[min]) < maxdiff) + return estimate; + + /* ok - drop the worse value and try again... */ + good_timer_sum = 0; + good_timer_count = 0; + if ((measured_times[max] - estimate) < + (estimate - measured_times[min])) { + printk(KERN_NOTICE "calibrate_delay_direct() dropping " + "min bogoMips estimate %d = %lu\n", + min, measured_times[min]); + measured_times[min] = 0; + min = max; + } else { + printk(KERN_NOTICE "calibrate_delay_direct() dropping " + "max bogoMips estimate %d = %lu\n", + max, measured_times[max]); + measured_times[max] = 0; + max = min; + } + + for (i = 0; i < MAX_DIRECT_CALIBRATION_RETRIES; i++) { + if (measured_times[i] == 0) + continue; + good_timer_count++; + good_timer_sum += measured_times[i]; + if (measured_times[i] < measured_times[min]) + min = i; + if (measured_times[i] > measured_times[max]) + max = i; + } + + } - printk(KERN_WARNING "calibrate_delay_direct() failed to get a good " - "estimate for loops_per_jiffy.\nProbably due to long platform interrupts. Consider using \"lpj=\" boot option.\n"); + printk(KERN_NOTICE "calibrate_delay_direct() failed to get a good " + "estimate for loops_per_jiffy.\nProbably due to long platform " + "interrupts. Consider using \"lpj=\" boot option.\n"); return 0; } #else |