4 files changed, 167 insertions, 4 deletions

diff --git a/include/linux/clockchips.h b/include/linux/clockchips.h
index e0c5a6c418de..dbe9e1457168 100644
--- a/include/linux/clockchips.h
+++ b/include/linux/clockchips.h
@@ -62,6 +62,11 @@ enum clock_event_mode {
 #define CLOCK_EVT_FEAT_DYNIRQ           0x000020
 #define CLOCK_EVT_FEAT_PERCPU           0x000040
 
+/*
+ * Clockevent device is based on a hrtimer for broadcast
+ */
+#define CLOCK_EVT_FEAT_HRTIMER          0x000080
+
 /**
  * struct clock_event_device - clock event device descriptor
  * @event_handler:      Assigned by the framework to be called by the low
@@ -83,6 +88,7 @@ enum clock_event_mode {
  * @name:               ptr to clock event name
  * @rating:             variable to rate clock event devices
  * @irq:                IRQ number (only for non CPU local devices)
+ * @bound_on:           Bound on CPU
  * @cpumask:            cpumask to indicate for which CPUs this device works
  * @list:               list head for the management code
  * @owner:              module reference
@@ -113,6 +119,7 @@ struct clock_event_device {
         const char              *name;
         int                     rating;
         int                     irq;
+        int                     bound_on;
         const struct cpumask    *cpumask;
         struct list_head        list;
         struct module           *owner;
@@ -180,9 +187,11 @@ extern int tick_receive_broadcast(void);
 #endif
 
 #if defined(CONFIG_GENERIC_CLOCKEVENTS_BROADCAST) && defined(CONFIG_TICK_ONESHOT)
+extern void tick_setup_hrtimer_broadcast(void);
 extern int tick_check_broadcast_expired(void);
 #else
 static inline int tick_check_broadcast_expired(void) { return 0; }
+static void tick_setup_hrtimer_broadcast(void) {};
 #endif
 
 #ifdef CONFIG_GENERIC_CLOCKEVENTS
diff --git a/kernel/time/Makefile b/kernel/time/Makefile
index 9250130646f5..06151ef4a744 100644
--- a/kernel/time/Makefile
+++ b/kernel/time/Makefile
@@ -3,7 +3,7 @@ obj-y += timeconv.o posix-clock.o alarmtimer.o
 
 obj-$(CONFIG_GENERIC_CLOCKEVENTS_BUILD)         += clockevents.o
 obj-$(CONFIG_GENERIC_CLOCKEVENTS)               += tick-common.o
-obj-$(CONFIG_GENERIC_CLOCKEVENTS_BROADCAST)     += tick-broadcast.o
+obj-$(CONFIG_GENERIC_CLOCKEVENTS_BROADCAST)     += tick-broadcast.o tick-broadcast-hrtimer.o
 obj-$(CONFIG_GENERIC_SCHED_CLOCK)               += sched_clock.o
 obj-$(CONFIG_TICK_ONESHOT)                      += tick-oneshot.o
 obj-$(CONFIG_TICK_ONESHOT)                      += tick-sched.o
diff --git a/kernel/time/tick-broadcast-hrtimer.c b/kernel/time/tick-broadcast-hrtimer.c
new file mode 100644
index 000000000000..92425279312b
--- /dev/null
+++ b/kernel/time/tick-broadcast-hrtimer.c
@@ -0,0 +1,106 @@
+/*
+ * linux/kernel/time/tick-broadcast-hrtimer.c
+ * This file emulates a local clock event device
+ * via a pseudo clock device.
+ */
+#include <linux/cpu.h>
+#include <linux/err.h>
+#include <linux/hrtimer.h>
+#include <linux/interrupt.h>
+#include <linux/percpu.h>
+#include <linux/profile.h>
+#include <linux/clockchips.h>
+#include <linux/sched.h>
+#include <linux/smp.h>
+#include <linux/module.h>
+
+#include "tick-internal.h"
+
+static struct hrtimer bctimer;
+
+static void bc_set_mode(enum clock_event_mode mode,
+                        struct clock_event_device *bc)
+{
+        switch (mode) {
+        case CLOCK_EVT_MODE_SHUTDOWN:
+                /*
+                 * Note, we cannot cancel the timer here as we might
+                 * run into the following live lock scenario:
+                 *
+                 * cpu 0                cpu1
+                 * lock(broadcast_lock);
+                 *                      hrtimer_interrupt()
+                 *                      bc_handler()
+                 *                         tick_handle_oneshot_broadcast();
+                 *                          lock(broadcast_lock);
+                 * hrtimer_cancel()
+                 *  wait_for_callback()
+                 */
+                hrtimer_try_to_cancel(&bctimer);
+                break;
+        default:
+                break;
+        }
+}
+
+/*
+ * This is called from the guts of the broadcast code when the cpu
+ * which is about to enter idle has the earliest broadcast timer event.
+ */
+static int bc_set_next(ktime_t expires, struct clock_event_device *bc)
+{
+        /*
+         * We try to cancel the timer first. If the callback is on
+         * flight on some other cpu then we let it handle it. If we
+         * were able to cancel the timer nothing can rearm it as we
+         * own broadcast_lock.
+         *
+         * However we can also be called from the event handler of
+         * ce_broadcast_hrtimer itself when it expires. We cannot
+         * restart the timer because we are in the callback, but we
+         * can set the expiry time and let the callback return
+         * HRTIMER_RESTART.
+         */
+        if (hrtimer_try_to_cancel(&bctimer) >= 0) {
+                hrtimer_start(&bctimer, expires, HRTIMER_MODE_ABS_PINNED);
+                /* Bind the "device" to the cpu */
+                bc->bound_on = smp_processor_id();
+        } else if (bc->bound_on == smp_processor_id()) {
+                hrtimer_set_expires(&bctimer, expires);
+        }
+        return 0;
+}
+
+static struct clock_event_device ce_broadcast_hrtimer = {
+        .set_mode               = bc_set_mode,
+        .set_next_ktime         = bc_set_next,
+        .features               = CLOCK_EVT_FEAT_ONESHOT |
+                                  CLOCK_EVT_FEAT_KTIME |
+                                  CLOCK_EVT_FEAT_HRTIMER,
+        .rating                 = 0,
+        .bound_on               = -1,
+        .min_delta_ns           = 1,
+        .max_delta_ns           = KTIME_MAX,
+        .min_delta_ticks        = 1,
+        .max_delta_ticks        = KTIME_MAX,
+        .mult                   = 1,
+        .shift                  = 0,
+        .cpumask                = cpu_all_mask,
+};
+
+static enum hrtimer_restart bc_handler(struct hrtimer *t)
+{
+        ce_broadcast_hrtimer.event_handler(&ce_broadcast_hrtimer);
+
+        if (ce_broadcast_hrtimer.next_event.tv64 == KTIME_MAX)
+                return HRTIMER_NORESTART;
+
+        return HRTIMER_RESTART;
+}
+
+void tick_setup_hrtimer_broadcast(void)
+{
+        hrtimer_init(&bctimer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+        bctimer.function = bc_handler;
+        clockevents_register_device(&ce_broadcast_hrtimer);
+}
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 84c8fd91d744..63c7b2d9ed8e 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -643,6 +643,42 @@ again:
         raw_spin_unlock(&tick_broadcast_lock);
 }
 
+static int broadcast_needs_cpu(struct clock_event_device *bc, int cpu)
+{
+        if (!(bc->features & CLOCK_EVT_FEAT_HRTIMER))
+                return 0;
+        if (bc->next_event.tv64 == KTIME_MAX)
+                return 0;
+        return bc->bound_on == cpu ? -EBUSY : 0;
+}
+
+static void broadcast_shutdown_local(struct clock_event_device *bc,
+                                     struct clock_event_device *dev)
+{
+        /*
+         * For hrtimer based broadcasting we cannot shutdown the cpu
+         * local device if our own event is the first one to expire or
+         * if we own the broadcast timer.
+         */
+        if (bc->features & CLOCK_EVT_FEAT_HRTIMER) {
+                if (broadcast_needs_cpu(bc, smp_processor_id()))
+                        return;
+                if (dev->next_event.tv64 < bc->next_event.tv64)
+                        return;
+        }
+        clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
+}
+
+static void broadcast_move_bc(int deadcpu)
+{
+        struct clock_event_device *bc = tick_broadcast_device.evtdev;
+
+        if (!bc || !broadcast_needs_cpu(bc, deadcpu))
+                return;
+        /* This moves the broadcast assignment to this cpu */
+        clockevents_program_event(bc, bc->next_event, 1);
+}
+
 /*
  * Powerstate information: The system enters/leaves a state, where
  * affected devices might stop
@@ -661,7 +697,7 @@ int tick_broadcast_oneshot_control(unsigned long reason)
          * states
          */
         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
-                return;
+                return 0;
 
         /*
          * We are called with preemtion disabled from the depth of the
@@ -672,7 +708,7 @@ int tick_broadcast_oneshot_control(unsigned long reason)
         dev = td->evtdev;
 
         if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
-                return;
+                return 0;
 
         bc = tick_broadcast_device.evtdev;
 
@@ -680,7 +716,7 @@ int tick_broadcast_oneshot_control(unsigned long reason)
         if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
                 if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) {
                         WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask));
-                        clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
+                        broadcast_shutdown_local(bc, dev);
                         /*
                          * We only reprogram the broadcast timer if we
                          * did not mark ourself in the force mask and
@@ -693,6 +729,16 @@ int tick_broadcast_oneshot_control(unsigned long reason)
                             dev->next_event.tv64 < bc->next_event.tv64)
                                 tick_broadcast_set_event(bc, cpu, dev->next_event, 1);
                 }
+                /*
+                 * If the current CPU owns the hrtimer broadcast
+                 * mechanism, it cannot go deep idle and we remove the
+                 * CPU from the broadcast mask. We don't have to go
+                 * through the EXIT path as the local timer is not
+                 * shutdown.
+                 */
+                ret = broadcast_needs_cpu(bc, cpu);
+                if (ret)
+                        cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
         } else {
                 if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_oneshot_mask)) {
                         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
@@ -866,6 +912,8 @@ void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
         cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
         cpumask_clear_cpu(cpu, tick_broadcast_force_mask);
 
+        broadcast_move_bc(cpu);
+
         raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 }