From febe294a9d27380abecfe973a1a6186df83bf4b3 Mon Sep 17 00:00:00 2001
From: Jose Miguel Ochoa <josemiguelo.ochoa@gmail.com>
Date: Thu, 3 Sep 2026 21:15:15 -0500
Subject: [PATCH] t2linux-config: Sync the hardware clock at shutdown

T2 Macs have one real RTC, in the EC, exposed to Linux twice: rtc0
through the legacy CMOS ports and rtc1 through the ACPI Time and Alarm
Device. Only _SRT on the ACPI side actually writes it. The kernel's
11-minute NTP writeback targets the hctosys device, rtc0, and the
firmware discards those writes into a volatile shadow that reads back
correctly and then forgets on reboot.

Nothing therefore ever sets the clock. Every boot reads a counter
ticking since the last cold power-on (1970-01-28), systemd bumps that to
its own build date, and the machine runs weeks in the past until chrony
syncs. Journal timestamps are wrong on every boot, and PackageKit's
reboot-to-install offline updates abort before rpm opens the database,
because that boot has no network to correct the clock first.

Add a oneshot unit that writes system time to the ACPI TAD RTC at
shutdown. rtc0 reads the same EC clock, so hctosys picks the value up on
the next boot. The RTC is located by ACPI000E in its name rather than
hardcoded to rtc1, and the unit is a no-op on machines without one.

Tested on MacBookPro16,1 (Fedora 44, kernel 7.1.9-200.t2): the boot log
goes from "setting system clock to 1970-01-28T03:04:49 UTC" to the
correct time, and an offline update that had failed twice completes.
---
 t2linux-config/t2linux-config.spec | 36 +++++++++++++++++++++++++++++-
 1 file changed, 35 insertions(+), 1 deletion(-)

diff --git a/t2linux-config/t2linux-config.spec b/t2linux-config/t2linux-config.spec
index c633d62..68ffbaa 100644
--- a/t2linux-config/t2linux-config.spec
+++ b/t2linux-config/t2linux-config.spec
@@ -1,11 +1,14 @@
 Name: t2linux-config
-Version: 16.0.0
+Version: 17.0.0
 Release: 1%{?dist}
 Summary: System configuration for linux on t2 macs.
 License: MIT
 URL: https://t2linux.org
 
 BuildRequires: systemd
+BuildRequires: systemd-rpm-macros
+
+Requires: util-linux
 
 %description
 System configuration for linux on T2 macs.
@@ -26,9 +29,28 @@ cat << EOF > 90-network-t2-ncm.conf
 no-auto-default=t2_ncm
 EOF
 
+cat << 'EOF' > t2linux-hwclock.service
+[Unit]
+Description=Save system time to the hardware clock at shutdown
+DefaultDependencies=no
+After=local-fs.target
+Before=shutdown.target
+Conflicts=shutdown.target
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+ExecStart=/usr/bin/true
+ExecStop=/bin/sh -c 'for r in /sys/class/rtc/rtc*; do grep -q ACPI000E "$r/name" 2>/dev/null && exec /usr/sbin/hwclock --rtc="/dev/${r##*/}" --systohc; done'
+
+[Install]
+WantedBy=multi-user.target
+EOF
+
 cat << EOF > 91-t2linux.preset
 enable get-apple-firmware.service
 enable t2fanrd.service
+enable t2linux-hwclock.service
 EOF
 
 %install
@@ -42,7 +64,19 @@ install -D -m 644 90-network-t2-ncm.conf %{buildroot}/usr/lib/NetworkManager/con
 
 install -D -m 644 91-t2linux.preset %{buildroot}/usr/lib/systemd/system-preset/91-t2linux.preset
 
+install -D -m 644 t2linux-hwclock.service %{buildroot}%{_unitdir}/t2linux-hwclock.service
+
+%post
+%systemd_post t2linux-hwclock.service
+
+%preun
+%systemd_preun t2linux-hwclock.service
+
+%postun
+%systemd_postun t2linux-hwclock.service
+
 %files
+%{_unitdir}/t2linux-hwclock.service
 /usr/lib/modules-load.d/t2linux-modules.conf
 /usr/lib/dracut/dracut.conf.d/t2linux-modules-install.conf
 %{_udevrulesdir}/90-network-t2-ncm.rules