1 files changed, 40 insertions, 37 deletions

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index c18d7efa1b4b..e0980f0d9a0a 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -113,7 +113,7 @@ EXPORT_SYMBOL_GPL(timecounter_cyc2time);
  * @shift:      pointer to shift variable
  * @from:       frequency to convert from
  * @to:         frequency to convert to
- * @minsec:     guaranteed runtime conversion range in seconds
+ * @maxsec:     guaranteed runtime conversion range in seconds
  *
  * The function evaluates the shift/mult pair for the scaled math
  * operations of clocksources and clockevents.
@@ -122,7 +122,7 @@ EXPORT_SYMBOL_GPL(timecounter_cyc2time);
  * NSEC_PER_SEC == 1GHz and @from is the counter frequency. For clock
  * event @to is the counter frequency and @from is NSEC_PER_SEC.
  *
- * The @minsec conversion range argument controls the time frame in
+ * The @maxsec conversion range argument controls the time frame in
  * seconds which must be covered by the runtime conversion with the
  * calculated mult and shift factors. This guarantees that no 64bit
  * overflow happens when the input value of the conversion is
@@ -131,7 +131,7 @@ EXPORT_SYMBOL_GPL(timecounter_cyc2time);
  * factors.
  */
 void
-clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec)
+clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 maxsec)
 {
         u64 tmp;
         u32 sft, sftacc= 32;
@@ -140,7 +140,7 @@ clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec)
          * Calculate the shift factor which is limiting the conversion
          * range:
          */
-        tmp = ((u64)minsec * from) >> 32;
+        tmp = ((u64)maxsec * from) >> 32;
         while (tmp) {
                 tmp >>=1;
                 sftacc--;
@@ -152,6 +152,7 @@ clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec)
          */
         for (sft = 32; sft > 0; sft--) {
                 tmp = (u64) to << sft;
+                tmp += from / 2;
                 do_div(tmp, from);
                 if ((tmp >> sftacc) == 0)
                         break;
@@ -184,7 +185,6 @@ static struct clocksource *watchdog;
 static struct timer_list watchdog_timer;
 static DECLARE_WORK(watchdog_work, clocksource_watchdog_work);
 static DEFINE_SPINLOCK(watchdog_lock);
-static cycle_t watchdog_last;
 static int watchdog_running;
 
 static int clocksource_watchdog_kthread(void *data);
@@ -253,11 +253,6 @@ static void clocksource_watchdog(unsigned long data)
         if (!watchdog_running)
                 goto out;
 
-        wdnow = watchdog->read(watchdog);
-        wd_nsec = clocksource_cyc2ns((wdnow - watchdog_last) & watchdog->mask,
-                                     watchdog->mult, watchdog->shift);
-        watchdog_last = wdnow;
-
         list_for_each_entry(cs, &watchdog_list, wd_list) {
 
                 /* Clocksource already marked unstable? */
@@ -267,19 +262,28 @@ static void clocksource_watchdog(unsigned long data)
                         continue;
                 }
 
+                local_irq_disable();
                 csnow = cs->read(cs);
+                wdnow = watchdog->read(watchdog);
+                local_irq_enable();
 
                 /* Clocksource initialized ? */
                 if (!(cs->flags & CLOCK_SOURCE_WATCHDOG)) {
                         cs->flags |= CLOCK_SOURCE_WATCHDOG;
-                        cs->wd_last = csnow;
+                        cs->wd_last = wdnow;
+                        cs->cs_last = csnow;
                         continue;
                 }
 
-                /* Check the deviation from the watchdog clocksource. */
-                cs_nsec = clocksource_cyc2ns((csnow - cs->wd_last) &
+                wd_nsec = clocksource_cyc2ns((wdnow - cs->wd_last) & watchdog->mask,
+                                             watchdog->mult, watchdog->shift);
+
+                cs_nsec = clocksource_cyc2ns((csnow - cs->cs_last) &
                                              cs->mask, cs->mult, cs->shift);
-                cs->wd_last = csnow;
+                cs->cs_last = csnow;
+                cs->wd_last = wdnow;
+
+                /* Check the deviation from the watchdog clocksource. */
                 if (abs(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD) {
                         clocksource_unstable(cs, cs_nsec - wd_nsec);
                         continue;
@@ -317,7 +321,6 @@ static inline void clocksource_start_watchdog(void)
                 return;
         init_timer(&watchdog_timer);
         watchdog_timer.function = clocksource_watchdog;
-        watchdog_last = watchdog->read(watchdog);
         watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
         add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask));
         watchdog_running = 1;
@@ -625,19 +628,6 @@ static void clocksource_enqueue(struct clocksource *cs)
         list_add(&cs->list, entry);
 }
 
-
-/*
- * Maximum time we expect to go between ticks. This includes idle
- * tickless time. It provides the trade off between selecting a
- * mult/shift pair that is very precise but can only handle a short
- * period of time, vs. a mult/shift pair that can handle long periods
- * of time but isn't as precise.
- *
- * This is a subsystem constant, and actual hardware limitations
- * may override it (ie: clocksources that wrap every 3 seconds).
- */
-#define MAX_UPDATE_LENGTH 5 /* Seconds */
-
 /**
  * __clocksource_updatefreq_scale - Used update clocksource with new freq
  * @t:          clocksource to be registered
@@ -651,15 +641,28 @@ static void clocksource_enqueue(struct clocksource *cs)
  */
 void __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq)
 {
+        u64 sec;
+
         /*
-         * Ideally we want to use  some of the limits used in
-         * clocksource_max_deferment, to provide a more informed
-         * MAX_UPDATE_LENGTH. But for now this just gets the
-         * register interface working properly.
+         * Calc the maximum number of seconds which we can run before
+         * wrapping around. For clocksources which have a mask > 32bit
+         * we need to limit the max sleep time to have a good
+         * conversion precision. 10 minutes is still a reasonable
+         * amount. That results in a shift value of 24 for a
+         * clocksource with mask >= 40bit and f >= 4GHz. That maps to
+         * ~ 0.06ppm granularity for NTP. We apply the same 12.5%
+         * margin as we do in clocksource_max_deferment()
          */
+        sec = (cs->mask - (cs->mask >> 5));
+        do_div(sec, freq);
+        do_div(sec, scale);
+        if (!sec)
+                sec = 1;
+        else if (sec > 600 && cs->mask > UINT_MAX)
+                sec = 600;
+
         clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
-                                      NSEC_PER_SEC/scale,
-                                      MAX_UPDATE_LENGTH*scale);
+                               NSEC_PER_SEC / scale, sec * scale);
         cs->max_idle_ns = clocksource_max_deferment(cs);
 }
 EXPORT_SYMBOL_GPL(__clocksource_updatefreq_scale);
@@ -678,14 +681,14 @@ EXPORT_SYMBOL_GPL(__clocksource_updatefreq_scale);
 int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
 {
 
-        /* Intialize mult/shift and max_idle_ns */
+        /* Initialize mult/shift and max_idle_ns */
         __clocksource_updatefreq_scale(cs, scale, freq);
 
         /* Add clocksource to the clcoksource list */
         mutex_lock(&clocksource_mutex);
         clocksource_enqueue(cs);
-        clocksource_select();
         clocksource_enqueue_watchdog(cs);
+        clocksource_select();
         mutex_unlock(&clocksource_mutex);
         return 0;
 }
@@ -705,8 +708,8 @@ int clocksource_register(struct clocksource *cs)
 
         mutex_lock(&clocksource_mutex);
         clocksource_enqueue(cs);
-        clocksource_select();
         clocksource_enqueue_watchdog(cs);
+        clocksource_select();
         mutex_unlock(&clocksource_mutex);
         return 0;
 }