From 4c3d3d24ddc40acc3204e1225a53eb95db2893e7 Mon Sep 17 00:00:00 2001
From: "J. Avila" <elavila@google.com>
Date: Mon, 20 Jul 2020 19:30:36 +0000
Subject: [PATCH] ANDROID: GKI: kernel: tick-sched: Add an API for wakeup
 callbacks

Some modules perform actions on wake, as checked in tick-sched. Add a
function to register callbacks and export it.

Bug: 161415027
Bug: 161414381
Signed-off-by: J. Avila <elavila@google.com>
Change-Id: I7e1da4aea9e78ad2a7f0c407d4162fabc0e368a7
---
 include/linux/tick.h     |  2 ++
 kernel/time/tick-sched.c | 22 +++++++++++++++++++++-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/include/linux/tick.h b/include/linux/tick.h
index 535f528eaa97..9e99133a6000 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -111,6 +111,8 @@ enum tick_dep_bits {
 #define TICK_DEP_MASK_SCHED		(1 << TICK_DEP_BIT_SCHED)
 #define TICK_DEP_MASK_CLOCK_UNSTABLE	(1 << TICK_DEP_BIT_CLOCK_UNSTABLE)
 
+extern void register_tick_sched_wakeup_callback(void (*cb)(void));
+
 #ifdef CONFIG_NO_HZ_COMMON
 extern bool tick_nohz_enabled;
 extern bool tick_nohz_tick_stopped(void);
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 95c62850d9a4..f8256bb66bfa 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -26,6 +26,7 @@
 #include <linux/module.h>
 #include <linux/irq_work.h>
 #include <linux/posix-timers.h>
+#include <linux/timer.h>
 #include <linux/context_tracking.h>
 #include <linux/mm.h>
 
@@ -1258,6 +1259,9 @@ void tick_irq_enter(void)
  * High resolution timer specific code
  */
 #ifdef CONFIG_HIGH_RES_TIMERS
+
+static void (*wake_callback)(void);
+
 /*
  * We rearm the timer until we get disabled by the idle code.
  * Called with interrupts disabled.
@@ -1275,8 +1279,15 @@ static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
 	 * Do not call, when we are not in irq context and have
 	 * no valid regs pointer
 	 */
-	if (regs)
+	if (regs) {
 		tick_sched_handle(ts, regs);
+		if (wake_callback && tick_do_timer_cpu == smp_processor_id()) {
+			/*
+			 * wakeup user if needed
+			 */
+			wake_callback();
+		}
+	}
 	else
 		ts->next_tick = 0;
 
@@ -1393,6 +1404,15 @@ int tick_check_oneshot_change(int allow_nohz)
 	return 0;
 }
 
+void register_tick_sched_wakeup_callback(void (*cb)(void))
+{
+	if (!wake_callback)
+		wake_callback = cb;
+	else
+		pr_warn("tick-sched wake cb already exists; skipping.\n");
+}
+EXPORT_SYMBOL_GPL(register_tick_sched_wakeup_callback);
+
 ktime_t *get_next_event_cpu(unsigned int cpu)
 {
 	return &(per_cpu(tick_cpu_device, cpu).evtdev->next_event);