atrtc.c is a repocopy of the RTC device driver from i386/isa/clock.c

In addition to the device driver functionality, it exposes a number of
functions which various other bits of code use to fondle the RTC chip.

2 files changed, 40 insertions, 599 deletions

diff --git a/sys/isa/atrtc.c b/sys/isa/atrtc.c
index 6573b373f1f1..87d03a5f2875 100644
--- a/sys/isa/atrtc.c
+++ b/sys/isa/atrtc.c
@@ -1,10 +1,7 @@
 /*-
- * Copyright (c) 1990 The Regents of the University of California.
+ * Copyright (c) 2008 Poul-Henning Kamp
  * All rights reserved.
  *
- * This code is derived from software contributed to Berkeley by
- * William Jolitz and Don Ahn.
- *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
@@ -13,14 +10,11 @@
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
- * 4. Neither the name of the University nor the names of its contributors
- *    may be used to endorse or promote products derived from this software
- *    without specific prior written permission.
  *
- * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
@@ -29,53 +23,22 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	from: @(#)clock.c	7.2 (Berkeley) 5/12/91
+ * $FreeBSD$
  */
 
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
-/*
- * Routines to handle clock hardware.
- */
-
-/*
- * inittodr, settodr and support routines written
- * by Christoph Robitschko <chmr@edvz.tu-graz.ac.at>
- *
- * reintroduced and updated by Chris Stenton <chris@gnome.co.uk> 8/10/94
- */
-
-#include "opt_apic.h"
-#include "opt_clock.h"
 #include "opt_isa.h"
-#include "opt_mca.h"
-#include "opt_xbox.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/bus.h>
 #include <sys/clock.h>
 #include <sys/lock.h>
-#include <sys/kdb.h>
 #include <sys/mutex.h>
-#include <sys/proc.h>
-#include <sys/timetc.h>
 #include <sys/kernel.h>
 #include <sys/module.h>
-#include <sys/sched.h>
-#include <sys/sysctl.h>
-
-#include <machine/clock.h>
-#include <machine/cpu.h>
-#include <machine/frame.h>
-#include <machine/intr_machdep.h>
-#include <machine/md_var.h>
-#ifdef DEV_APIC
-#include <machine/apicvar.h>
-#endif
-#include <machine/ppireg.h>
-#include <machine/timerreg.h>
 
 #include <isa/rtc.h>
 #ifdef DEV_ISA
@@ -83,313 +46,13 @@ __FBSDID("$FreeBSD$");
 #include <isa/isavar.h>
 #endif
 
-#ifdef DEV_MCA
-#include <i386/bios/mca_machdep.h>
-#endif
-
-#define	TIMER_DIV(x) ((i8254_freq + (x) / 2) / (x))
-
-int	clkintr_pending;
-static int pscnt = 1;
-static int psdiv = 1;
-int	statclock_disable;
-#ifndef TIMER_FREQ
-#define TIMER_FREQ   1193182
-#endif
-u_int	i8254_freq = TIMER_FREQ;
-TUNABLE_INT("hw.i8254.freq", &i8254_freq);
-int	i8254_max_count;
-static int i8254_real_max_count;
 #define	RTC_LOCK	mtx_lock_spin(&clock_lock)
 #define	RTC_UNLOCK	mtx_unlock_spin(&clock_lock)
 
-static	struct mtx clock_lock;
-static	struct intsrc *i8254_intsrc;
-static	u_int32_t i8254_lastcount;
-static	u_int32_t i8254_offset;
-static	int	(*i8254_pending)(struct intsrc *);
-static	int	i8254_ticked;
-static	int	using_lapic_timer;
 static	int	rtc_reg = -1;
 static	u_char	rtc_statusa = RTCSA_DIVIDER | RTCSA_NOPROF;
 static	u_char	rtc_statusb = RTCSB_24HR;
 
-/* Values for timerX_state: */
-#define	RELEASED	0
-#define	RELEASE_PENDING	1
-#define	ACQUIRED	2
-#define	ACQUIRE_PENDING	3
-
-static	u_char	timer2_state;
-
-static	unsigned i8254_get_timecount(struct timecounter *tc);
-static	unsigned i8254_simple_get_timecount(struct timecounter *tc);
-static	void	set_i8254_freq(u_int freq, int intr_freq);
-
-static struct timecounter i8254_timecounter = {
-	i8254_get_timecount,	/* get_timecount */
-	0,			/* no poll_pps */
-	~0u,			/* counter_mask */
-	0,			/* frequency */
-	"i8254",		/* name */
-	0			/* quality */
-};
-
-static int
-clkintr(struct trapframe *frame)
-{
-
-	if (timecounter->tc_get_timecount == i8254_get_timecount) {
-		mtx_lock_spin(&clock_lock);
-		if (i8254_ticked)
-			i8254_ticked = 0;
-		else {
-			i8254_offset += i8254_max_count;
-			i8254_lastcount = 0;
-		}
-		clkintr_pending = 0;
-		mtx_unlock_spin(&clock_lock);
-	}
-	KASSERT(!using_lapic_timer, ("clk interrupt enabled with lapic timer"));
-	hardclock(TRAPF_USERMODE(frame), TRAPF_PC(frame));
-#ifdef DEV_MCA
-	/* Reset clock interrupt by asserting bit 7 of port 0x61 */
-	if (MCA_system)
-		outb(0x61, inb(0x61) | 0x80);
-#endif
-	return (FILTER_HANDLED);
-}
-
-int
-timer_spkr_acquire(void)
-{
-	int mode;
-
-	mode = TIMER_SEL2 | TIMER_SQWAVE | TIMER_16BIT;
-
-	if (timer2_state != RELEASED)
-		return (-1);
-	timer2_state = ACQUIRED;
-
-	/*
-	 * This access to the timer registers is as atomic as possible
-	 * because it is a single instruction.  We could do better if we
-	 * knew the rate.  Use of splclock() limits glitches to 10-100us,
-	 * and this is probably good enough for timer2, so we aren't as
-	 * careful with it as with timer0.
-	 */
-	outb(TIMER_MODE, TIMER_SEL2 | (mode & 0x3f));
-	ppi_spkr_on();		/* enable counter2 output to speaker */
-	return (0);
-}
-
-int
-timer_spkr_release(void)
-{
-
-	if (timer2_state != ACQUIRED)
-		return (-1);
-	timer2_state = RELEASED;
-	outb(TIMER_MODE, TIMER_SEL2 | TIMER_SQWAVE | TIMER_16BIT);
-	ppi_spkr_off();		/* disable counter2 output to speaker */
-	return (0);
-}
-
-void
-timer_spkr_setfreq(int freq)
-{
-
-	freq = i8254_freq / freq;
-	mtx_lock_spin(&clock_lock);
-	outb(TIMER_CNTR2, freq & 0xff);
-	outb(TIMER_CNTR2, freq >> 8);
-	mtx_unlock_spin(&clock_lock);
-}
-
-/*
- * This routine receives statistical clock interrupts from the RTC.
- * As explained above, these occur at 128 interrupts per second.
- * When profiling, we receive interrupts at a rate of 1024 Hz.
- *
- * This does not actually add as much overhead as it sounds, because
- * when the statistical clock is active, the hardclock driver no longer
- * needs to keep (inaccurate) statistics on its own.  This decouples
- * statistics gathering from scheduling interrupts.
- *
- * The RTC chip requires that we read status register C (RTC_INTR)
- * to acknowledge an interrupt, before it will generate the next one.
- * Under high interrupt load, rtcintr() can be indefinitely delayed and
- * the clock can tick immediately after the read from RTC_INTR.  In this
- * case, the mc146818A interrupt signal will not drop for long enough
- * to register with the 8259 PIC.  If an interrupt is missed, the stat
- * clock will halt, considerably degrading system performance.  This is
- * why we use 'while' rather than a more straightforward 'if' below.
- * Stat clock ticks can still be lost, causing minor loss of accuracy
- * in the statistics, but the stat clock will no longer stop.
- */
-static int
-rtcintr(struct trapframe *frame)
-{
-
-	while (rtcin(RTC_INTR) & RTCIR_PERIOD) {
-		if (profprocs != 0) {
-			if (--pscnt == 0)
-				pscnt = psdiv;
-			profclock(TRAPF_USERMODE(frame), TRAPF_PC(frame));
-		}
-		if (pscnt == psdiv)
-			statclock(TRAPF_USERMODE(frame));
-	}
-	return (FILTER_HANDLED);
-}
-
-#include "opt_ddb.h"
-#ifdef DDB
-#include <ddb/ddb.h>
-
-DB_SHOW_COMMAND(rtc, rtc)
-{
-	printf("%02x/%02x/%02x %02x:%02x:%02x, A = %02x, B = %02x, C = %02x\n",
-	       rtcin(RTC_YEAR), rtcin(RTC_MONTH), rtcin(RTC_DAY),
-	       rtcin(RTC_HRS), rtcin(RTC_MIN), rtcin(RTC_SEC),
-	       rtcin(RTC_STATUSA), rtcin(RTC_STATUSB), rtcin(RTC_INTR));
-}
-#endif /* DDB */
-
-static int
-getit(void)
-{
-	int high, low;
-
-	mtx_lock_spin(&clock_lock);
-
-	/* Select timer0 and latch counter value. */
-	outb(TIMER_MODE, TIMER_SEL0 | TIMER_LATCH);
-
-	low = inb(TIMER_CNTR0);
-	high = inb(TIMER_CNTR0);
-
-	mtx_unlock_spin(&clock_lock);
-	return ((high << 8) | low);
-}
-
-/*
- * Wait "n" microseconds.
- * Relies on timer 1 counting down from (i8254_freq / hz)
- * Note: timer had better have been programmed before this is first used!
- */
-void
-DELAY(int n)
-{
-	int delta, prev_tick, tick, ticks_left;
-
-#ifdef DELAYDEBUG
-	int getit_calls = 1;
-	int n1;
-	static int state = 0;
-#endif
-
-	if (tsc_freq != 0 && !tsc_is_broken) {
-		uint64_t start, end, now;
-
-		sched_pin();
-		start = rdtsc();
-		end = start + (tsc_freq * n) / 1000000;
-		do {
-			cpu_spinwait();
-			now = rdtsc();
-		} while (now < end || (now > start && end < start));
-		sched_unpin();
-		return;
-	}
-#ifdef DELAYDEBUG
-	if (state == 0) {
-		state = 1;
-		for (n1 = 1; n1 <= 10000000; n1 *= 10)
-			DELAY(n1);
-		state = 2;
-	}
-	if (state == 1)
-		printf("DELAY(%d)...", n);
-#endif
-	/*
-	 * Read the counter first, so that the rest of the setup overhead is
-	 * counted.  Guess the initial overhead is 20 usec (on most systems it
-	 * takes about 1.5 usec for each of the i/o's in getit().  The loop
-	 * takes about 6 usec on a 486/33 and 13 usec on a 386/20.  The
-	 * multiplications and divisions to scale the count take a while).
-	 *
-	 * However, if ddb is active then use a fake counter since reading
-	 * the i8254 counter involves acquiring a lock.  ddb must not do
-	 * locking for many reasons, but it calls here for at least atkbd
-	 * input.
-	 */
-#ifdef KDB
-	if (kdb_active)
-		prev_tick = 1;
-	else
-#endif
-		prev_tick = getit();
-	n -= 0;			/* XXX actually guess no initial overhead */
-	/*
-	 * Calculate (n * (i8254_freq / 1e6)) without using floating point
-	 * and without any avoidable overflows.
-	 */
-	if (n <= 0)
-		ticks_left = 0;
-	else if (n < 256)
-		/*
-		 * Use fixed point to avoid a slow division by 1000000.
-		 * 39099 = 1193182 * 2^15 / 10^6 rounded to nearest.
-		 * 2^15 is the first power of 2 that gives exact results
-		 * for n between 0 and 256.
-		 */
-		ticks_left = ((u_int)n * 39099 + (1 << 15) - 1) >> 15;
-	else
-		/*
-		 * Don't bother using fixed point, although gcc-2.7.2
-		 * generates particularly poor code for the long long
-		 * division, since even the slow way will complete long
-		 * before the delay is up (unless we're interrupted).
-		 */
-		ticks_left = ((u_int)n * (long long)i8254_freq + 999999)
-			     / 1000000;
-
-	while (ticks_left > 0) {
-#ifdef KDB
-		if (kdb_active) {
-			inb(0x84);
-			tick = prev_tick - 1;
-			if (tick <= 0)
-				tick = i8254_max_count;
-		} else
-#endif
-			tick = getit();
-#ifdef DELAYDEBUG
-		++getit_calls;
-#endif
-		delta = prev_tick - tick;
-		prev_tick = tick;
-		if (delta < 0) {
-			delta += i8254_max_count;
-			/*
-			 * Guard against i8254_max_count being wrong.
-			 * This shouldn't happen in normal operation,
-			 * but it may happen if set_i8254_freq() is
-			 * traced.
-			 */
-			if (delta < 0)
-				delta = 0;
-		}
-		ticks_left -= delta;
-	}
-#ifdef DELAYDEBUG
-	if (state == 1)
-		printf(" %d calls to getit() at %d usec each\n",
-		       getit_calls, (n + 5) / getit_calls);
-#endif
-}
-
 /*
  * RTC support routines
  */
@@ -433,287 +96,43 @@ readrtc(int port)
 	return(bcd2bin(rtcin(port)));
 }
 
-static void
-set_i8254_freq(u_int freq, int intr_freq)
-{
-	int new_i8254_real_max_count;
-
-	i8254_timecounter.tc_frequency = freq;
-	mtx_lock_spin(&clock_lock);
-	i8254_freq = freq;
-	if (using_lapic_timer)
-		new_i8254_real_max_count = 0x10000;
-	else
-		new_i8254_real_max_count = TIMER_DIV(intr_freq);
-	if (new_i8254_real_max_count != i8254_real_max_count) {
-		i8254_real_max_count = new_i8254_real_max_count;
-		if (i8254_real_max_count == 0x10000)
-			i8254_max_count = 0xffff;
-		else
-			i8254_max_count = i8254_real_max_count;
-		outb(TIMER_MODE, TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
-		outb(TIMER_CNTR0, i8254_real_max_count & 0xff);
-		outb(TIMER_CNTR0, i8254_real_max_count >> 8);
-	}
-	mtx_unlock_spin(&clock_lock);
-}
-
-static void
-i8254_restore(void)
-{
-
-	mtx_lock_spin(&clock_lock);
-	outb(TIMER_MODE, TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
-	outb(TIMER_CNTR0, i8254_real_max_count & 0xff);
-	outb(TIMER_CNTR0, i8254_real_max_count >> 8);
-	mtx_unlock_spin(&clock_lock);
-}
-
-static void
-rtc_restore(void)
-{
-
-	/* Restore all of the RTC's "status" (actually, control) registers. */
-	/* XXX locking is needed for RTC access. */
-	rtc_reg = -1;
-	writertc(RTC_STATUSB, RTCSB_24HR);
-	writertc(RTC_STATUSA, rtc_statusa);
-	writertc(RTC_STATUSB, rtc_statusb);
-	rtcin(RTC_INTR);
-}
-
-/*
- * Restore all the timers non-atomically (XXX: should be atomically).
- *
- * This function is called from pmtimer_resume() to restore all the timers.
- * This should not be necessary, but there are broken laptops that do not
- * restore all the timers on resume.
- */
 void
-timer_restore(void)
-{
-
-	i8254_restore();		/* restore i8254_freq and hz */
-	rtc_restore();			/* reenable RTC interrupts */
-}
-
-/* This is separate from startrtclock() so that it can be called early. */
-void
-i8254_init(void)
-{
-
-	mtx_init(&clock_lock, "clk", NULL, MTX_SPIN | MTX_NOPROFILE);
-	set_i8254_freq(i8254_freq, hz);
-}
-
-void
-startrtclock()
+atrtc_start(void)
 {
 
 	writertc(RTC_STATUSA, rtc_statusa);
 	writertc(RTC_STATUSB, RTCSB_24HR);
-
-	set_i8254_freq(i8254_freq, hz);
-	tc_init(&i8254_timecounter);
-
-	init_TSC();
 }
 
-/*
- * Start both clocks running.
- */
 void
-cpu_initclocks()
+atrtc_rate(unsigned rate)
 {
-	int diag;
 
-#ifdef DEV_APIC
-	using_lapic_timer = lapic_setup_clock();
-#endif
-	/*
-	 * If we aren't using the local APIC timer to drive the kernel
-	 * clocks, setup the interrupt handler for the 8254 timer 0 so
-	 * that it can drive hardclock().  Otherwise, change the 8254
-	 * timecounter to user a simpler algorithm.
-	 */
-	if (!using_lapic_timer) {
-		intr_add_handler("clk", 0, (driver_filter_t *)clkintr, NULL,
-		    NULL, INTR_TYPE_CLK, NULL);
-		i8254_intsrc = intr_lookup_source(0);
-		if (i8254_intsrc != NULL)
-			i8254_pending =
-			    i8254_intsrc->is_pic->pic_source_pending;
-	} else {
-		i8254_timecounter.tc_get_timecount =
-		    i8254_simple_get_timecount;
-		i8254_timecounter.tc_counter_mask = 0xffff;
-		set_i8254_freq(i8254_freq, hz);
-	}
-
-	/* Initialize RTC. */
+	rtc_statusa = RTCSA_DIVIDER | rate;
 	writertc(RTC_STATUSA, rtc_statusa);
-	writertc(RTC_STATUSB, RTCSB_24HR);
-
-	/*
-	 * If the separate statistics clock hasn't been explicility disabled
-	 * and we aren't already using the local APIC timer to drive the
-	 * kernel clocks, then setup the RTC to periodically interrupt to
-	 * drive statclock() and profclock().
-	 */
-	if (!statclock_disable && !using_lapic_timer) {
-		diag = rtcin(RTC_DIAG);
-		if (diag != 0)
-			printf("RTC BIOS diagnostic error %b\n",
-			    diag, RTCDG_BITS);
-
-	        /* Setting stathz to nonzero early helps avoid races. */
-		stathz = RTC_NOPROFRATE;
-		profhz = RTC_PROFRATE;
-
-		/* Enable periodic interrupts from the RTC. */
-		rtc_statusb |= RTCSB_PINTR;
-		intr_add_handler("rtc", 8,
-		    (driver_filter_t *)rtcintr, NULL, NULL,
-		    INTR_TYPE_CLK, NULL);
-
-		writertc(RTC_STATUSB, rtc_statusb);
-		rtcin(RTC_INTR);
-	}
-
-	init_TSC_tc();
 }
 
 void
-cpu_startprofclock(void)
+atrtc_enable_intr(void)
 {
 
-	if (using_lapic_timer)
-		return;
-	rtc_statusa = RTCSA_DIVIDER | RTCSA_PROF;
-	writertc(RTC_STATUSA, rtc_statusa);
-	psdiv = pscnt = psratio;
+	rtc_statusb |= RTCSB_PINTR;
+	writertc(RTC_STATUSB, rtc_statusb);
+	rtcin(RTC_INTR);
 }
 
 void
-cpu_stopprofclock(void)
+atrtc_restore(void)
 {
 
-	if (using_lapic_timer)
-		return;
-	rtc_statusa = RTCSA_DIVIDER | RTCSA_NOPROF;
+	/* Restore all of the RTC's "status" (actually, control) registers. */
+	rtcin(RTC_STATUSA);	/* dummy to get rtc_reg set */
+	writertc(RTC_STATUSB, RTCSB_24HR);
 	writertc(RTC_STATUSA, rtc_statusa);
-	psdiv = pscnt = 1;
-}
-
-static int
-sysctl_machdep_i8254_freq(SYSCTL_HANDLER_ARGS)
-{
-	int error;
-	u_int freq;
-
-	/*
-	 * Use `i8254' instead of `timer' in external names because `timer'
-	 * is is too generic.  Should use it everywhere.
-	 */
-	freq = i8254_freq;
-	error = sysctl_handle_int(oidp, &freq, 0, req);
-	if (error == 0 && req->newptr != NULL)
-		set_i8254_freq(freq, hz);
-	return (error);
-}
-
-SYSCTL_PROC(_machdep, OID_AUTO, i8254_freq, CTLTYPE_INT | CTLFLAG_RW,
-    0, sizeof(u_int), sysctl_machdep_i8254_freq, "IU", "");
-
-static unsigned
-i8254_simple_get_timecount(struct timecounter *tc)
-{
-
-	return (i8254_max_count - getit());
-}
-
-static unsigned
-i8254_get_timecount(struct timecounter *tc)
-{
-	u_int count;
-	u_int high, low;
-	u_int eflags;
-
-	eflags = read_eflags();
-	mtx_lock_spin(&clock_lock);
-
-	/* Select timer0 and latch counter value. */
-	outb(TIMER_MODE, TIMER_SEL0 | TIMER_LATCH);
-
-	low = inb(TIMER_CNTR0);
-	high = inb(TIMER_CNTR0);
-	count = i8254_max_count - ((high << 8) | low);
-	if (count < i8254_lastcount ||
-	    (!i8254_ticked && (clkintr_pending ||
-	    ((count < 20 || (!(eflags & PSL_I) &&
-	    count < i8254_max_count / 2u)) &&
-	    i8254_pending != NULL && i8254_pending(i8254_intsrc))))) {
-		i8254_ticked = 1;
-		i8254_offset += i8254_max_count;
-	}
-	i8254_lastcount = count;
-	count += i8254_offset;
-	mtx_unlock_spin(&clock_lock);
-	return (count);
-}
-
-#ifdef DEV_ISA
-/*
- * Attach to the ISA PnP descriptors for the timer
- */
-static struct isa_pnp_id attimer_ids[] = {
-	{ 0x0001d041 /* PNP0100 */, "AT timer" },
-	{ 0 }
-};
-
-static int
-attimer_probe(device_t dev)
-{
-	int result;
-	
-	result = ISA_PNP_PROBE(device_get_parent(dev), dev, attimer_ids);
-	if (result <= 0)
-		device_quiet(dev);
-	return(result);
-}
-
-static int
-attimer_attach(device_t dev)
-{
-	return(0);
+	writertc(RTC_STATUSB, rtc_statusb);
+	rtcin(RTC_INTR);
 }
 
-static device_method_t attimer_methods[] = {
-	/* Device interface */
-	DEVMETHOD(device_probe,		attimer_probe),
-	DEVMETHOD(device_attach,	attimer_attach),
-	DEVMETHOD(device_detach,	bus_generic_detach),
-	DEVMETHOD(device_shutdown,	bus_generic_shutdown),
-	DEVMETHOD(device_suspend,	bus_generic_suspend),
-	DEVMETHOD(device_resume,	bus_generic_resume),
-	{ 0, 0 }
-};
-
-static driver_t attimer_driver = {
-	"attimer",
-	attimer_methods,
-	1,		/* no softc */
-};
-
-static devclass_t attimer_devclass;
-
-DRIVER_MODULE(attimer, isa, attimer_driver, attimer_devclass, 0, 0);
-DRIVER_MODULE(attimer, acpi, attimer_driver, attimer_devclass, 0, 0);
-
-#endif /* DEV_ISA */
-
-#ifdef DEV_ISA
-
 /**********************************************************************
  * RTC driver for subr_rtc
  */
@@ -866,4 +285,15 @@ static devclass_t atrtc_devclass;
 DRIVER_MODULE(atrtc, isa, atrtc_driver, atrtc_devclass, 0, 0);
 DRIVER_MODULE(atrtc, acpi, atrtc_driver, atrtc_devclass, 0, 0);
 
-#endif /* DEV_ISA */
+#include "opt_ddb.h"
+#ifdef DDB
+#include <ddb/ddb.h>
+
+DB_SHOW_COMMAND(rtc, rtc)
+{
+	printf("%02x/%02x/%02x %02x:%02x:%02x, A = %02x, B = %02x, C = %02x\n",
+		rtcin(RTC_YEAR), rtcin(RTC_MONTH), rtcin(RTC_DAY),
+		rtcin(RTC_HRS), rtcin(RTC_MIN), rtcin(RTC_SEC),
+		rtcin(RTC_STATUSA), rtcin(RTC_STATUSB), rtcin(RTC_INTR));
+}
+#endif /* DDB */
diff --git a/sys/isa/rtc.h b/sys/isa/rtc.h
index 35bef94e08e9..c802b0ba923a 100644
--- a/sys/isa/rtc.h
+++ b/sys/isa/rtc.h
@@ -110,4 +110,15 @@
 #define RTC_EXTHI	0x18	/* low byte of extended mem size */
 
 #define	RTC_CENTURY	0x32	/* current century */
+
+#ifdef _KERNEL
+extern  struct mtx clock_lock;
+int	rtcin(int reg);
+void	atrtc_start(void);
+void	atrtc_rate(unsigned rate);
+void	atrtc_enable_intr(void);
+void	atrtc_restore(void);
+void	writertc(int reg, u_char val);
+#endif
+
 #endif /* _I386_ISA_RTC_H_ */