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-rw-r--r--init/calibrate.c75
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