git: c592a3b0ae98 - stable/13 - atrtc: expose power loss as sysctl

The branch stable/13 has been updated by corvink:

URL: https://cgit.FreeBSD.org/src/commit/?id=c592a3b0ae98ca90c09f300afde6d705b84ff0d7

commit c592a3b0ae98ca90c09f300afde6d705b84ff0d7
Author:     Corvin Köhne <corvink@FreeBSD.org>
AuthorDate: 2022-12-08 07:28:42 +0000
Commit:     Corvin Köhne <corvink@FreeBSD.org>
CommitDate: 2023-02-09 07:03:59 +0000

    atrtc: expose power loss as sysctl
    
    Exposing the a power loss of the rtc as an sysctl makes it easier to
    detect an empty cmos battery.
    
    Reviewed by:            manu
    MFC after:              1 week
    Sponsored by:           Beckhoff Automation GmbH & Co. KG
    Differential Revision:  https://reviews.freebsd.org/D38325
    
    (cherry picked from commit 55f1ca209d37d7b5a6faf57b23c7341cb7f84ee6)
---
 sys/x86/isa/atrtc.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/sys/x86/isa/atrtc.c b/sys/x86/isa/atrtc.c
index aff838c53851..167e7cfbf8fd 100644
--- a/sys/x86/isa/atrtc.c
+++ b/sys/x86/isa/atrtc.c
@@ -62,6 +62,11 @@ __FBSDID("$FreeBSD$");
 #include <machine/md_var.h>
 #endif
 
+/* tunable to detect a power loss of the rtc */
+static bool atrtc_power_lost = false;
+SYSCTL_BOOL(_machdep, OID_AUTO, atrtc_power_lost, CTLFLAG_RD, &atrtc_power_lost,
+    false, "RTC lost power on last power cycle (probably caused by an emtpy cmos battery)");
+
 /*
  * atrtc_lock protects low-level access to individual hardware registers.
  * atrtc_time_lock protects the entire sequence of accessing multiple registers
@@ -597,6 +602,7 @@ atrtc_gettime(device_t dev, struct timespec *ts)
 
 	/* Look if we have a RTC present and the time is valid */
 	if (!(rtcin(RTC_STATUSD) & RTCSD_PWR)) {
+		atrtc_power_lost = true;
 		device_printf(dev, "WARNING: Battery failure indication\n");
 		return (EINVAL);
 	}