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authorWill Deacon <will@kernel.org>2021-05-24 23:18:17 +0100
committerThomas Gleixner <tglx@linutronix.de>2021-05-31 17:04:46 +0200
commitea5c7f1b9aa1a7c9d1bb9440084ac1256789fadb (patch)
tree3ca52d1974644872549ea613d546ca0c3b0e698e /kernel/time
parenttick/broadcast: Prefer per-cpu oneshot wakeup timers to broadcast (diff)
downloadlinux-dev-ea5c7f1b9aa1a7c9d1bb9440084ac1256789fadb.tar.xz
linux-dev-ea5c7f1b9aa1a7c9d1bb9440084ac1256789fadb.zip
tick/broadcast: Program wakeup timer when entering idle if required
When configuring the broadcast timer on entry to and exit from deep idle states, prefer a per-CPU wakeup timer if one exists. On entry to idle, stop the tick device and transfer the next event into the oneshot wakeup device, which will serve as the wakeup from idle. To avoid the overhead of additional hardware accesses on exit from idle, leave the timer armed and treat the inevitable interrupt as a (possibly spurious) tick event. Signed-off-by: Will Deacon <will@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20210524221818.15850-5-will@kernel.org
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/tick-broadcast.c44
1 files changed, 43 insertions, 1 deletions
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 0e9e06d6cc5c..9b845212430b 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -96,6 +96,15 @@ static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
return per_cpu(tick_oneshot_wakeup_device, cpu);
}
+static void tick_oneshot_wakeup_handler(struct clock_event_device *wd)
+{
+ /*
+ * If we woke up early and the tick was reprogrammed in the
+ * meantime then this may be spurious but harmless.
+ */
+ tick_receive_broadcast();
+}
+
static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
int cpu)
{
@@ -121,6 +130,7 @@ static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
if (!try_module_get(newdev->owner))
return false;
+ newdev->event_handler = tick_oneshot_wakeup_handler;
set_device:
clockevents_exchange_device(curdev, newdev);
per_cpu(tick_oneshot_wakeup_device, cpu) = newdev;
@@ -909,16 +919,48 @@ out:
return ret;
}
+static int tick_oneshot_wakeup_control(enum tick_broadcast_state state,
+ struct tick_device *td,
+ int cpu)
+{
+ struct clock_event_device *dev, *wd;
+
+ dev = td->evtdev;
+ if (td->mode != TICKDEV_MODE_ONESHOT)
+ return -EINVAL;
+
+ wd = tick_get_oneshot_wakeup_device(cpu);
+ if (!wd)
+ return -ENODEV;
+
+ switch (state) {
+ case TICK_BROADCAST_ENTER:
+ clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT_STOPPED);
+ clockevents_switch_state(wd, CLOCK_EVT_STATE_ONESHOT);
+ clockevents_program_event(wd, dev->next_event, 1);
+ break;
+ case TICK_BROADCAST_EXIT:
+ /* We may have transitioned to oneshot mode while idle */
+ if (clockevent_get_state(wd) != CLOCK_EVT_STATE_ONESHOT)
+ return -ENODEV;
+ }
+
+ return 0;
+}
+
int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
{
struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
int cpu = smp_processor_id();
+ if (!tick_oneshot_wakeup_control(state, td, cpu))
+ return 0;
+
if (tick_broadcast_device.evtdev)
return ___tick_broadcast_oneshot_control(state, td, cpu);
/*
- * If there is no broadcast device, tell the caller not
+ * If there is no broadcast or wakeup device, tell the caller not
* to go into deep idle.
*/
return -EBUSY;