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From: "tip-bot2 for Will Deacon" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Will Deacon <will@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: timers/core] tick/broadcast: Program wakeup timer when entering idle if required
Date: Mon, 31 May 2021 15:06:59 -0000	[thread overview]
Message-ID: <162247361903.29796.16135245441223506210.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20210524221818.15850-5-will@kernel.org>

The following commit has been merged into the timers/core branch of tip:

Commit-ID:     ea5c7f1b9aa1a7c9d1bb9440084ac1256789fadb
Gitweb:        https://git.kernel.org/tip/ea5c7f1b9aa1a7c9d1bb9440084ac1256789fadb
Author:        Will Deacon <will@kernel.org>
AuthorDate:    Mon, 24 May 2021 23:18:17 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Mon, 31 May 2021 17:04:46 +02:00

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

---
 kernel/time/tick-broadcast.c | 44 ++++++++++++++++++++++++++++++++++-
 1 file changed, 43 insertions(+), 1 deletion(-)

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 0e9e06d..9b84521 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;

  reply	other threads:[~2021-05-31 17:07 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-24 22:18 [PATCH v2 0/5] tick/broadcast: Allow per-cpu timers to be used instead of broadcast Will Deacon
2021-05-24 22:18 ` [PATCH v2 1/5] tick/broadcast: Drop unneeded CONFIG_GENERIC_CLOCKEVENTS_BROADCAST guard Will Deacon
2021-05-31 15:07   ` [tip: timers/core] " tip-bot2 for Will Deacon
2021-05-24 22:18 ` [PATCH v2 2/5] tick/broadcast: Split __tick_broadcast_oneshot_control() into a helper Will Deacon
2021-05-27  7:23   ` Xin Hao
2021-05-27  8:22     ` Will Deacon
2021-05-27 11:35       ` Xin Hao
2021-05-27 11:55         ` Will Deacon
2021-05-27 11:56         ` Will Deacon
2021-05-31 14:29           ` Thomas Gleixner
2021-06-01 12:13             ` Will Deacon
2021-06-01 18:14               ` Thomas Gleixner
2021-05-31 15:06   ` [tip: timers/core] " tip-bot2 for Will Deacon
2021-05-24 22:18 ` [PATCH v2 3/5] tick/broadcast: Prefer per-cpu oneshot wakeup timers to broadcast Will Deacon
2021-05-31 15:06   ` [tip: timers/core] " tip-bot2 for Will Deacon
2021-05-24 22:18 ` [PATCH v2 4/5] tick/broadcast: Program wakeup timer when entering idle if required Will Deacon
2021-05-31 15:06   ` tip-bot2 for Will Deacon [this message]
2021-05-24 22:18 ` [PATCH v2 5/5] timer_list: Print name of per-cpu wakeup device Will Deacon
2021-05-31 15:06   ` [tip: timers/core] " tip-bot2 for Will Deacon

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