1 files changed, 115 insertions, 14 deletions

diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index e4c699dfa4e8..1ecd6ba36d6c 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -94,42 +94,143 @@ void clockevents_shutdown(struct clock_event_device *dev)
         dev->next_event.tv64 = KTIME_MAX;
 }
 
+#ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST
+
+/* Limit min_delta to a jiffie */
+#define MIN_DELTA_LIMIT         (NSEC_PER_SEC / HZ)
+
+/**
+ * clockevents_increase_min_delta - raise minimum delta of a clock event device
+ * @dev:       device to increase the minimum delta
+ *
+ * Returns 0 on success, -ETIME when the minimum delta reached the limit.
+ */
+static int clockevents_increase_min_delta(struct clock_event_device *dev)
+{
+        /* Nothing to do if we already reached the limit */
+        if (dev->min_delta_ns >= MIN_DELTA_LIMIT) {
+                printk(KERN_WARNING "CE: Reprogramming failure. Giving up\n");
+                dev->next_event.tv64 = KTIME_MAX;
+                return -ETIME;
+        }
+
+        if (dev->min_delta_ns < 5000)
+                dev->min_delta_ns = 5000;
+        else
+                dev->min_delta_ns += dev->min_delta_ns >> 1;
+
+        if (dev->min_delta_ns > MIN_DELTA_LIMIT)
+                dev->min_delta_ns = MIN_DELTA_LIMIT;
+
+        printk(KERN_WARNING "CE: %s increased min_delta_ns to %llu nsec\n",
+               dev->name ? dev->name : "?",
+               (unsigned long long) dev->min_delta_ns);
+        return 0;
+}
+
+/**
+ * clockevents_program_min_delta - Set clock event device to the minimum delay.
+ * @dev:        device to program
+ *
+ * Returns 0 on success, -ETIME when the retry loop failed.
+ */
+static int clockevents_program_min_delta(struct clock_event_device *dev)
+{
+        unsigned long long clc;
+        int64_t delta;
+        int i;
+
+        for (i = 0;;) {
+                delta = dev->min_delta_ns;
+                dev->next_event = ktime_add_ns(ktime_get(), delta);
+
+                if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
+                        return 0;
+
+                dev->retries++;
+                clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
+                if (dev->set_next_event((unsigned long) clc, dev) == 0)
+                        return 0;
+
+                if (++i > 2) {
+                        /*
+                         * We tried 3 times to program the device with the
+                         * given min_delta_ns. Try to increase the minimum
+                         * delta, if that fails as well get out of here.
+                         */
+                        if (clockevents_increase_min_delta(dev))
+                                return -ETIME;
+                        i = 0;
+                }
+        }
+}
+
+#else  /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
+
+/**
+ * clockevents_program_min_delta - Set clock event device to the minimum delay.
+ * @dev:        device to program
+ *
+ * Returns 0 on success, -ETIME when the retry loop failed.
+ */
+static int clockevents_program_min_delta(struct clock_event_device *dev)
+{
+        unsigned long long clc;
+        int64_t delta;
+
+        delta = dev->min_delta_ns;
+        dev->next_event = ktime_add_ns(ktime_get(), delta);
+
+        if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
+                return 0;
+
+        dev->retries++;
+        clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
+        return dev->set_next_event((unsigned long) clc, dev);
+}
+
+#endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
+
 /**
  * clockevents_program_event - Reprogram the clock event device.
+ * @dev:        device to program
  * @expires:    absolute expiry time (monotonic clock)
+ * @force:      program minimum delay if expires can not be set
  *
  * Returns 0 on success, -ETIME when the event is in the past.
  */
 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
-                              ktime_t now)
+                              bool force)
 {
         unsigned long long clc;
         int64_t delta;
+        int rc;
 
         if (unlikely(expires.tv64 < 0)) {
                 WARN_ON_ONCE(1);
                 return -ETIME;
         }
 
-        delta = ktime_to_ns(ktime_sub(expires, now));
-
-        if (delta <= 0)
-                return -ETIME;
-
         dev->next_event = expires;
 
         if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
                 return 0;
 
-        if (delta > dev->max_delta_ns)
-                delta = dev->max_delta_ns;
-        if (delta < dev->min_delta_ns)
-                delta = dev->min_delta_ns;
+        /* Shortcut for clockevent devices that can deal with ktime. */
+        if (dev->features & CLOCK_EVT_FEAT_KTIME)
+                return dev->set_next_ktime(expires, dev);
+
+        delta = ktime_to_ns(ktime_sub(expires, ktime_get()));
+        if (delta <= 0)
+                return force ? clockevents_program_min_delta(dev) : -ETIME;
 
-        clc = delta * dev->mult;
-        clc >>= dev->shift;
+        delta = min(delta, (int64_t) dev->max_delta_ns);
+        delta = max(delta, (int64_t) dev->min_delta_ns);
 
-        return dev->set_next_event((unsigned long) clc, dev);
+        clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
+        rc = dev->set_next_event((unsigned long) clc, dev);
+
+        return (rc && force) ? clockevents_program_min_delta(dev) : rc;
 }
 
 /**
@@ -258,7 +359,7 @@ int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
         if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
                 return 0;
 
-        return clockevents_program_event(dev, dev->next_event, ktime_get());
+        return clockevents_program_event(dev, dev->next_event, false);
 }
 
 /*