pcppi-keep-at-halt.patch -- NetBSD 11.0: keep pcppi0's timer at halt, so
the "options BEEP_ONHALT" beep is a tone rather than 18 Hz silence.
Needs sysbeep-keep-at-halt.patch as well.  Apply in usr/src with:
patch -p0

Author: Royce Williams
License: the same terms as each NetBSD source file it modifies.

--- sys/dev/isa/pcppi.c.orig
+++ sys/dev/isa/pcppi.c
@@ -63,9 +63,22 @@
 void	pcppi_childdet(device_t, device_t);
 int	pcppi_rescan(device_t, const char *, const int *);
 
+/*
+ * PCPPI_KEEP_AT_HALT -- NOT DVF_DETACH_SHUTDOWN.  With that flag,
+ * config_detach_all() calls pcppi_detach() during an ordinary
+ * "shutdown -h".  Its first act is pcppi_detach_speaker(), which sets
+ * sc_timer = NULL; it then fails at config_detach_children() because
+ * spkr0 declares no shutdown flag, so pcppi0 stays attached with its
+ * timer already gone.  A later BEEP_ONHALT then skips
+ * attimer_set_pitch() and gates the speaker on over an unprogrammed
+ * PIT channel 2: measured at 18 Hz, which is silence on a real speaker.
+ *
+ * Companion to SYSBEEP_KEEP_AT_HALT in sys/arch/x86/isa/clock.c.
+ * Neither is sufficient alone.
+ */
 CFATTACH_DECL3_NEW(pcppi, sizeof(struct pcppi_softc),
     pcppi_match, pcppi_isa_attach, pcppi_detach, NULL, pcppi_rescan,
-    pcppi_childdet, DVF_DETACH_SHUTDOWN);
+    pcppi_childdet, 0);
 
 static int pcppisearch(device_t, cfdata_t, const int *, void *);
 static void pcppi_bell_stop(struct pcppi_softc *);