rtc_cmos PNP0B00:00: error -ENXIO: IRQ index 0 not found

Is this a new report?

Yes

System Info

Void 6.18.50_1 x86_64 AuthenticAMD uptodate rrrrm

Package(s) Affected

linux6.18-6.18.51_1 linux6.18-6.18.52_1

Does a report exist for this bug with the project's home (upstream) and/or another distro?

Possibly related:

https://ratatoskr.run/linux-acpi/2026/04/3497990
https://github.com/torvalds/linux/blob/master/drivers/rtc/rtc-cmos.c
https://lkml.org/lkml/2026/4/3/1120

Expected behaviour

No kern.err output in syslog

Actual behaviour

Since updating to linux6.18-6.18.51_1, my syslog output has started throwing the following:

2026-09-14T16:29:35.09839 kern.err: [    2.358202] rtc_cmos PNP0B00:00: error -ENXIO: IRQ index 0 not found
2026-09-14T16:29:35.09865 kern.info: [    2.358210] rtc_cmos PNP0B00:00: RTC can wake from S4
2026-09-14T16:29:35.09865 kern.info: [    2.358256] rtc_cmos PNP0B00:00: registered as rtc0
2026-09-14T16:29:35.09865 kern.info: [    2.358277] rtc_cmos PNP0B00:00: setting system clock to 2026-09-14T16:29:28 UTC (1789403368)
2026-09-14T16:29:35.09865 kern.info: [    2.358292] rtc_cmos PNP0B00:00: no alarms, y3k, 114 bytes nvram

By comparison, rebooting with linux6.18-6.18.50_1 delivers no error output:

2026-09-14T16:30:37.09887 kern.info: [    2.370338] rtc_cmos 00:02: RTC can wake from S4
2026-09-14T16:30:37.09887 kern.info: [    2.370481] rtc_cmos 00:02: registered as rtc0
2026-09-14T16:30:37.09887 kern.info: [    2.370502] rtc_cmos 00:02: setting system clock to 2026-09-14T16:30:30 UTC (1789403430)
2026-09-14T16:30:37.09887 kern.info: [    2.370517] rtc_cmos 00:02: alarms up to one month, y3k, 114 bytes nvram

So, wake-on-rtc alarms disabled? I wouldn't know, since I never even utilized that feature

Is it safe to boot into linux6.18.51 if I don't utilize any wake/suspend feature, or are there other concerns tied to Real Time Clock?

Steps to reproduce

1. Probably this only works on some hardware configurations. I'm using am AM5 platform. By comparison, this has not happened on another Intel platform
2. Install package linux6.18-6.18.51_1, generate initramfs and reboot into that installed kernel
3. Take a look at your syslog output. I used sudo svlogtail | grep "rtc"

EDIT: The problem persists even after installing linux6.18-6.18.52_1, while reverting to linux6.18-6.18.50_1 still fixes the error. This may thus be a regression

Start with drivers/rtc/rtc-cmos.c and compare the rtc_cmos logs from linux6.18-6.18.50_1 with 6.18.51_1 and 6.18.52_1. Review the linked upstream Linux and LKML references to determine whether the IRQ error affects RTC or wake functionality. Done means the regression and its impact are established, with the appropriate upstream or package-side action identified.