Module Name: src
Committed By: imil
Date: Mon Feb 24 07:18:02 UTC 2025
Modified Files:
src/sys/arch/x86/isa: clock.c
Log Message:
Check for RTC presence to avoid hang with QEMU microvm and rtc=off
parameter.
Test bits 0-6 of MC146818's Register D, which must be 0 according to
the specification. This prevents a later hang in rtcget() when no RTC
is present.
To generate a diff of this commit:
cvs rdiff -u -r1.41 -r1.42 src/sys/arch/x86/isa/clock.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/arch/x86/isa/clock.c
diff -u src/sys/arch/x86/isa/clock.c:1.41 src/sys/arch/x86/isa/clock.c:1.42
--- src/sys/arch/x86/isa/clock.c:1.41 Wed Jan 25 15:54:52 2023
+++ src/sys/arch/x86/isa/clock.c Mon Feb 24 07:18:02 2025
@@ -1,4 +1,4 @@
-/* $NetBSD: clock.c,v 1.41 2023/01/25 15:54:52 riastradh Exp $ */
+/* $NetBSD: clock.c,v 1.42 2025/02/24 07:18:02 imil Exp $ */
/*-
* Copyright (c) 1990 The Regents of the University of California.
@@ -121,7 +121,7 @@ WITH THE USE OR PERFORMANCE OF THIS SOFT
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: clock.c,v 1.41 2023/01/25 15:54:52 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: clock.c,v 1.42 2025/02/24 07:18:02 imil Exp $");
/* #define CLOCKDEBUG */
/* #define CLOCK_PARANOIA */
@@ -327,6 +327,14 @@ startrtclock(void)
{
int s;
+ /*
+ * Check that RTC is present, bits 0 to 6 of register D are
+ * read-only and must be 0. At least on QEMU/microvm, when
+ * rtc=off, all bits are set to 1
+ */
+ if ((mc146818_read(NULL, MC_REGD) & 0x7f) != 0)
+ return;
+
if (!rtclock_init)
initrtclock(TIMER_FREQ);
