Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...
[linux-3.10.git] / init / calibrate.c
index 6eb48e5..fda0a7b 100644 (file)
@@ -9,6 +9,7 @@
 #include <linux/init.h>
 #include <linux/timex.h>
 #include <linux/smp.h>
+#include <linux/percpu.h>
 
 unsigned long lpj_fine;
 unsigned long preset_lpj;
@@ -38,6 +39,9 @@ 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 +70,7 @@ 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 +78,8 @@ 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 +94,75 @@ 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;
 
-       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");
+               /* 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_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 +171,8 @@ 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 +180,122 @@ 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;
+}
+
+static DEFINE_PER_CPU(unsigned long, cpu_loops_per_jiffy) = { 0 };
+
+/*
+ * Check if cpu calibration delay is already known. For example,
+ * some processors with multi-core sockets may have all cores
+ * with the same calibration delay.
+ *
+ * Architectures should override this function if a faster calibration
+ * method is available.
+ */
+unsigned long __attribute__((weak)) __cpuinit calibrate_delay_is_known(void)
+{
+       return 0;
+}
+
 void __cpuinit calibrate_delay(void)
 {
-       unsigned long ticks, loopbit;
-       int lps_precision = LPS_PREC;
+       unsigned long lpj;
        static bool printed;
+       int this_cpu = smp_processor_id();
 
-       if (preset_lpj) {
-               loops_per_jiffy = preset_lpj;
+       if (per_cpu(cpu_loops_per_jiffy, this_cpu)) {
+               lpj = per_cpu(cpu_loops_per_jiffy, this_cpu);
+               if (!printed)
+                       pr_info("Calibrating delay loop (skipped) "
+                               "already calibrated this CPU");
+       } else if (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_is_known())) {
+               ;
+       } 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();
        }
+       per_cpu(cpu_loops_per_jiffy, this_cpu) = lpj;
        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;
 }