[PATCH v1 2/2] rtc: cmos: Do not require IRQ if ACPI alarm is used

From: Rafael J. Wysocki

Date: Sat Mar 14 2026 - 08:15:28 EST


From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

If the ACPI RTC fixed event is used, a dedicated IRQ is not required
for the CMOS RTC alarm to work, so allow the driver to use the alarm
without a valid IRQ in that case.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
---
drivers/rtc/rtc-cmos.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)

--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -216,6 +216,11 @@ static inline void cmos_write_bank2(unsi

/*----------------------------------------------------------------*/

+static bool cmos_no_alarm(struct cmos_rtc *cmos)
+{
+ return !is_valid_irq(cmos->irq) && !cmos_use_acpi_alarm();
+}
+
static int cmos_read_time(struct device *dev, struct rtc_time *t)
{
int ret;
@@ -287,7 +292,7 @@ static int cmos_read_alarm(struct device
};

/* This not only a rtc_op, but also called directly */
- if (!is_valid_irq(cmos->irq))
+ if (cmos_no_alarm(cmos))
return -ETIMEDOUT;

/* Basic alarms only support hour, minute, and seconds fields.
@@ -520,7 +525,7 @@ static int cmos_set_alarm(struct device
int ret;

/* This not only a rtc_op, but also called directly */
- if (!is_valid_irq(cmos->irq))
+ if (cmos_no_alarm(cmos))
return -EIO;

ret = cmos_validate_alarm(dev, t);
@@ -1096,7 +1101,7 @@ cmos_do_probe(struct device *dev, struct
dev_dbg(dev, "IRQ %d is already in use\n", rtc_irq);
goto cleanup1;
}
- } else {
+ } else if (!cmos_use_acpi_alarm()) {
clear_bit(RTC_FEATURE_ALARM, cmos_rtc.rtc->features);
}

@@ -1121,7 +1126,7 @@ cmos_do_probe(struct device *dev, struct
acpi_rtc_event_setup(dev);

dev_info(dev, "%s%s, %d bytes nvram%s\n",
- !is_valid_irq(rtc_irq) ? "no alarms" :
+ cmos_no_alarm(&cmos_rtc) ? "no alarms" :
cmos_rtc.mon_alrm ? "alarms up to one year" :
cmos_rtc.day_alrm ? "alarms up to one month" :
"alarms up to one day",
@@ -1147,7 +1152,7 @@ cleanup0:
static void cmos_do_shutdown(int rtc_irq)
{
spin_lock_irq(&rtc_lock);
- if (is_valid_irq(rtc_irq))
+ if (!cmos_no_alarm(&cmos_rtc))
cmos_irq_disable(&cmos_rtc, RTC_IRQMASK);
spin_unlock_irq(&rtc_lock);
}