From 95c5af053f5ea363033a65a3d007ea84b10fc313 Mon Sep 17 00:00:00 2001 From: Pranav Prasad Date: Mon, 29 Jan 2024 21:31:48 +0000 Subject: [PATCH 2/3] alarmtimer, PM: suspend: Expose a function from alarmtimer to perform check at the beginning of the suspend flow in enter_state() The alarmtimer driver currently fails suspend attempts when there is an alarm pending within the next suspend_check_duration_ns nanoseconds, since the system is expected to wake up soon anyway. The entire suspend process is initiated even though the system will immediately awaken. This process includes substantial work before the suspend fails and additional work afterwards to undo the failed suspend that was attempted. Therefore on battery-powered devices that initiate suspend attempts from userspace, it may be advantageous to be able to fail the suspend earlier in the suspend flow to avoid power consumption instead of unnecessarily doing extra work. As one data point, an analysis of a subset of Android devices showed that imminent alarms account for roughly 40% of all suspend failures on average leading to unnecessary power wastage. To facilitate this, expose function time_check_suspend_fail() from alarmtimer to be used by the power subsystem to perform the check earlier in the suspend flow. Perform the check in enter_state() and return early if an alarm is to be fired in the next suspend_check_duration_ns nanoseconds, failing suspend. Change-Id: I02d7853d0b05d93b121988818f8a80461b4a358c Signed-off-by: Pranav Prasad Signed-off-by: Kelly Rossmoyer --- include/linux/time.h | 1 + kernel/power/suspend.c | 3 ++ kernel/time/alarmtimer.c | 113 ++++++++++++++++++++++++++++----------- 3 files changed, 87 insertions(+), 30 deletions(-) diff --git a/include/linux/time.h b/include/linux/time.h index 16cf4522d6f3..aab7c4e51e11 100644 --- a/include/linux/time.h +++ b/include/linux/time.h @@ -56,6 +56,7 @@ struct tm { }; void time64_to_tm(time64_t totalsecs, int offset, struct tm *result); +int time_check_suspend_fail(void); # include diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c index fa3bf161d13f..7a0175dae0d9 100644 --- a/kernel/power/suspend.c +++ b/kernel/power/suspend.c @@ -26,6 +26,7 @@ #include #include #include +#include #include #include #include @@ -564,6 +565,8 @@ static int enter_state(suspend_state_t state) #endif } else if (!valid_state(state)) { return -EINVAL; + } else if (time_check_suspend_fail()) { + return -ETIME; } if (!mutex_trylock(&system_transition_mutex)) return -EBUSY; diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c index e5d2e560b4c1..085b1ace0c31 100644 --- a/kernel/time/alarmtimer.c +++ b/kernel/time/alarmtimer.c @@ -115,6 +115,84 @@ static int alarmtimer_sysfs_add(void) return ret; } +/** + * alarmtimer_init_soonest - Initializes parameters to find soonest alarm. + * @min: ptr to relative time to the soonest alarm to expire + * @expires: ptr to absolute time of the soonest alarm to expire + * @type: ptr to alarm type + * + */ +static void alarmtimer_init_soonest(ktime_t *min, ktime_t *expires, int *type) +{ + unsigned long flags; + + spin_lock_irqsave(&freezer_delta_lock, flags); + *min = freezer_delta; + *expires = freezer_expires; + *type = freezer_alarmtype; + freezer_delta = 0; + spin_unlock_irqrestore(&freezer_delta_lock, flags); +} + +/** + * alarmtimer_get_soonest - Finds the soonest alarm to expire among the alarm bases. + * @min: ptr to relative time to the soonest alarm to expire + * @expires: ptr to absolute time of the soonest alarm to expire + * @type: ptr to alarm type + * + */ +static void alarmtimer_get_soonest(ktime_t *min, ktime_t *expires, int *type) +{ + int i; + unsigned long flags; + + /* Find the soonest timer to expire */ + for (i = 0; i < ALARM_NUMTYPE; i++) { + struct alarm_base *base = &alarm_bases[i]; + struct timerqueue_node *next; + ktime_t delta; + + spin_lock_irqsave(&base->lock, flags); + next = timerqueue_getnext(&base->timerqueue); + spin_unlock_irqrestore(&base->lock, flags); + if (!next) + continue; + delta = ktime_sub(next->expires, base->get_ktime()); + if (!(*min) || (delta < *min)) { + *expires = next->expires; + *min = delta; + *type = i; + } + } +} + +/** + * time_check_suspend_fail - Check if suspend should be failed due to an + * alarm within the next suspend_check_duration nanoseconds. + * + * Returns error if suspend should be failed, else returns 0. + */ +int time_check_suspend_fail(void) +{ + ktime_t min, expires; + int type; + + /* Initialize parameters to find soonest timer */ + alarmtimer_init_soonest(&min, &expires, &type); + + /* Find the soonest timer to expire */ + alarmtimer_get_soonest(&min, &expires, &type); + + if (min == 0) + return 0; + + if (ktime_to_ns(min) < suspend_check_duration_ns) + return -EBUSY; + + return 0; +} +EXPORT_SYMBOL(time_check_suspend_fail); + /** * alarmtimer_get_rtcdev - Return selected rtcdevice * @@ -296,49 +374,24 @@ EXPORT_SYMBOL_GPL(alarm_expires_remaining); static int alarmtimer_suspend(struct device *dev) { ktime_t min, now, expires; - int i, ret, type; + int ret, type; struct rtc_device *rtc; - unsigned long flags; struct rtc_time tm; - spin_lock_irqsave(&freezer_delta_lock, flags); - min = freezer_delta; - expires = freezer_expires; - type = freezer_alarmtype; - freezer_delta = 0; - spin_unlock_irqrestore(&freezer_delta_lock, flags); + /* Initialize parameters to find soonest timer */ + alarmtimer_init_soonest(&min, &expires, &type); rtc = alarmtimer_get_rtcdev(); /* If we have no rtcdev, just return */ if (!rtc) return 0; - /* Find the soonest timer to expire*/ - for (i = 0; i < ALARM_NUMTYPE; i++) { - struct alarm_base *base = &alarm_bases[i]; - struct timerqueue_node *next; - ktime_t delta; + /* Find the soonest timer to expire */ + alarmtimer_get_soonest(&min, &expires, &type); - spin_lock_irqsave(&base->lock, flags); - next = timerqueue_getnext(&base->timerqueue); - spin_unlock_irqrestore(&base->lock, flags); - if (!next) - continue; - delta = ktime_sub(next->expires, base->get_ktime()); - if (!min || (delta < min)) { - expires = next->expires; - min = delta; - type = i; - } - } if (min == 0) return 0; - if (ktime_to_ns(min) < suspend_check_duration_ns) { - pm_wakeup_event(dev, suspend_check_duration_ns/NSEC_PER_MSEC); - return -EBUSY; - } - trace_alarmtimer_suspend(expires, type); /* Setup an rtc timer to fire that far in the future */ -- 2.43.0.429.g432eaa2c6b-goog