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rtc: interface: Add rtc_read_next_alarm() to read next expiring timer

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Add a new function rtc_read_next_alarm() that reads the next expiring
alarm from the RTC timerqueue. This is different from rtc_read_alarm(),
which only reads the aie_timer.

The wakealarm sysfs file programs the rtc->aie_timer, whereas the
alarmtimer suspend routine programs its own timer into the RTC timerqueue.
Both timers end up in the RTC's timerqueue, and the first expiring timer
is what gets armed in the hardware.

This new function allows code to query which alarm will actually fire
next, regardless of which subsystem programmed it. This is needed by
platform code that needs to program secondary timers based on the
actual next wakeup time.

Link: https://lore.kernel.org/all/87ed50z0le.ffs@tglx
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://patch.msgid.link/20260521043714.1022930-2-mario.limonciello@amd.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
This commit is contained in:
Mario Limonciello 2026-05-20 23:37:13 -05:00 committed by Alexandre Belloni
parent 1afe4f19d6
commit 947d7ea6f6
2 changed files with 42 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
drivers/rtc/interface.c
View File

@ -384,6 +384,46 @@ int __rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
return err;
}
/**
* rtc_read_next_alarm - read the next expiring alarm
* @rtc: RTC device
* @alarm: storage for the alarm information
*
* Read the next expiring alarm from the RTC timerqueue. This returns
* the alarm that will actually fire next, which may be different from
* rtc_read_alarm() if multiple timers are queued (e.g., alarmtimer
* and wakealarm sysfs both active).
*
* Returns: 0 on success, -ENOENT if no alarm is pending, or other error.
*/
int rtc_read_next_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
{
struct timerqueue_node *next;
int err;
if (!rtc || !alarm)
return -EINVAL;
err = mutex_lock_interruptible(&rtc->ops_lock);
if (err)
return err;
next = timerqueue_getnext(&rtc->timerqueue);
if (!next) {
err = -ENOENT;
goto unlock;
}
memset(alarm, 0, sizeof(struct rtc_wkalrm));
alarm->time = rtc_ktime_to_tm(next->expires);
alarm->enabled = 1;
unlock:
mutex_unlock(&rtc->ops_lock);
return err;
}
EXPORT_SYMBOL_GPL(rtc_read_next_alarm);
int rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
{
int err;

2
include/linux/rtc.h
View File

@ -190,6 +190,8 @@ extern int rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm);
int __rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm);
extern int rtc_read_alarm(struct rtc_device *rtc,
struct rtc_wkalrm *alrm);
extern int rtc_read_next_alarm(struct rtc_device *rtc,
struct rtc_wkalrm *alrm);
extern int rtc_set_alarm(struct rtc_device *rtc,
struct rtc_wkalrm *alrm);
extern int rtc_initialize_alarm(struct rtc_device *rtc,