1 files changed, 143 insertions, 49 deletions

diff --git a/init/calibrate.c b/init/calibrate.c
index 6eb48e53d61c..aae2f40fea4c 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 )
@@ -66,7 +69,7 @@ static unsigned long __cpuinit calibrate_delay_direct(void)
                 pre_start = 0;
                 read_current_timer(&start);
                 start_jiffies = jiffies;
-                while (jiffies <= (start_jiffies + 1)) {
+                while (time_before_eq(jiffies, start_jiffies + 1)) {
                         pre_start = start;
                         read_current_timer(&start);
                 }
@@ -74,8 +77,8 @@ static unsigned long __cpuinit calibrate_delay_direct(void)
 
                 pre_end = 0;
                 end = post_start;
-                while (jiffies <=
-                       (start_jiffies + 1 + DELAY_CALIBRATION_TICKS)) {
+                while (time_before_eq(jiffies, start_jiffies + 1 +
+                                               DELAY_CALIBRATION_TICKS)) {
                         pre_end = end;
                         read_current_timer(&end);
                 }
@@ -90,18 +93,75 @@ 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 &&
+                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
@@ -110,8 +170,8 @@ static unsigned long __cpuinit calibrate_delay_direct(void) {return 0;}
 
 /*
  * This is the number of bits of precision for the loops_per_jiffy.  Each
- * bit takes on average 1.5/HZ seconds.  This (like the original) is a little
- * better than 1%
+ * time we refine our estimate after the first takes 1.5/HZ seconds, so try
+ * to start with a good estimate.
  * For the boot cpu we can skip the delay calibration and assign it a value
  * calculated based on the timer frequency.
  * For the rest of the CPUs we cannot assume that the timer frequency is same as
@@ -119,64 +179,98 @@ static unsigned long __cpuinit calibrate_delay_direct(void) {return 0;}
  */
 #define LPS_PREC 8
 
+static unsigned long __cpuinit calibrate_delay_converge(void)
+{
+        /* First stage - slowly accelerate to find initial bounds */
+        unsigned long lpj, lpj_base, ticks, loopadd, loopadd_base, chop_limit;
+        int trials = 0, band = 0, trial_in_band = 0;
+
+        lpj = (1<<12);
+
+        /* wait for "start of" clock tick */
+        ticks = jiffies;
+        while (ticks == jiffies)
+                ; /* nothing */
+        /* Go .. */
+        ticks = jiffies;
+        do {
+                if (++trial_in_band == (1<<band)) {
+                        ++band;
+                        trial_in_band = 0;
+                }
+                __delay(lpj * band);
+                trials += band;
+        } while (ticks == jiffies);
+        /*
+         * We overshot, so retreat to a clear underestimate. Then estimate
+         * the largest likely undershoot. This defines our chop bounds.
+         */
+        trials -= band;
+        loopadd_base = lpj * band;
+        lpj_base = lpj * trials;
+
+recalibrate:
+        lpj = lpj_base;
+        loopadd = loopadd_base;
+
+        /*
+         * Do a binary approximation to get lpj set to
+         * equal one clock (up to LPS_PREC bits)
+         */
+        chop_limit = lpj >> LPS_PREC;
+        while (loopadd > chop_limit) {
+                lpj += loopadd;
+                ticks = jiffies;
+                while (ticks == jiffies)
+                        ; /* nothing */
+                ticks = jiffies;
+                __delay(lpj);
+                if (jiffies != ticks)   /* longer than 1 tick */
+                        lpj -= loopadd;
+                loopadd >>= 1;
+        }
+        /*
+         * If we incremented every single time possible, presume we've
+         * massively underestimated initially, and retry with a higher
+         * start, and larger range. (Only seen on x86_64, due to SMIs)
+         */
+        if (lpj + loopadd * 2 == lpj_base + loopadd_base * 2) {
+                lpj_base = lpj;
+                loopadd_base <<= 2;
+                goto recalibrate;
+        }
+
+        return lpj;
+}
+
 void __cpuinit calibrate_delay(void)
 {
-        unsigned long ticks, loopbit;
-        int lps_precision = LPS_PREC;
+        unsigned long lpj;
         static bool printed;
 
         if (preset_lpj) {
-                loops_per_jiffy = preset_lpj;
+                lpj = preset_lpj;
                 if (!printed)
                         pr_info("Calibrating delay loop (skipped) "
                                 "preset value.. ");
         } else if ((!printed) && lpj_fine) {
-                loops_per_jiffy = lpj_fine;
+                lpj = lpj_fine;
                 pr_info("Calibrating delay loop (skipped), "
                         "value calculated using timer frequency.. ");
-        } else if ((loops_per_jiffy = calibrate_delay_direct()) != 0) {
+        } else if ((lpj = calibrate_delay_direct()) != 0) {
                 if (!printed)
                         pr_info("Calibrating delay using timer "
                                 "specific routine.. ");
         } else {
-                loops_per_jiffy = (1<<12);
-
                 if (!printed)
                         pr_info("Calibrating delay loop... ");
-                while ((loops_per_jiffy <<= 1) != 0) {
-                        /* wait for "start of" clock tick */
-                        ticks = jiffies;
-                        while (ticks == jiffies)
-                                /* nothing */;
-                        /* Go .. */
-                        ticks = jiffies;
-                        __delay(loops_per_jiffy);
-                        ticks = jiffies - ticks;
-                        if (ticks)
-                                break;
-                }
-
-                /*
-                 * Do a binary approximation to get loops_per_jiffy set to
-                 * equal one clock (up to lps_precision bits)
-                 */
-                loops_per_jiffy >>= 1;
-                loopbit = loops_per_jiffy;
-                while (lps_precision-- && (loopbit >>= 1)) {
-                        loops_per_jiffy |= loopbit;
-                        ticks = jiffies;
-                        while (ticks == jiffies)
-                                /* nothing */;
-                        ticks = jiffies;
-                        __delay(loops_per_jiffy);
-                        if (jiffies != ticks)   /* longer than 1 tick */
-                                loops_per_jiffy &= ~loopbit;
-                }
+                lpj = calibrate_delay_converge();
         }
         if (!printed)
                 pr_cont("%lu.%02lu BogoMIPS (lpj=%lu)\n",
-                        loops_per_jiffy/(500000/HZ),
-                        (loops_per_jiffy/(5000/HZ)) % 100, loops_per_jiffy);
+                        lpj/(500000/HZ),
+                        (lpj/(5000/HZ)) % 100, lpj);
 
+        loops_per_jiffy = lpj;
         printed = true;
 }