diff --git a/sys/kern/kern_cpu.c b/sys/kern/kern_cpu.c
index 524ffc1e3420..247b5f6c150a 100644
--- a/sys/kern/kern_cpu.c
+++ b/sys/kern/kern_cpu.c
@@ -1,1151 +1,1159 @@
 /*-
  * SPDX-License-Identifier: BSD-2-Clause
  *
  * Copyright (c) 2004-2007 Nate Lawson (SDG)
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 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.
  *
  * 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 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)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
 
 #include <sys/cdefs.h>
 #include <sys/param.h>
 #include <sys/bus.h>
 #include <sys/cpu.h>
 #include <sys/eventhandler.h>
 #include <sys/kernel.h>
 #include <sys/lock.h>
 #include <sys/malloc.h>
 #include <sys/module.h>
 #include <sys/proc.h>
 #include <sys/queue.h>
 #include <sys/sbuf.h>
 #include <sys/sched.h>
 #include <sys/smp.h>
 #include <sys/sysctl.h>
 #include <sys/systm.h>
 #include <sys/sx.h>
 #include <sys/timetc.h>
 #include <sys/taskqueue.h>
 
 #include "cpufreq_if.h"
 
 /*
  * Common CPU frequency glue code.  Drivers for specific hardware can
  * attach this interface to allow users to get/set the CPU frequency.
  */
 
 /*
  * Number of levels we can handle.  Levels are synthesized from settings
  * so for M settings and N drivers, there may be M*N levels.
  */
 #define CF_MAX_LEVELS	256
 
 struct cf_saved_freq {
 	struct cf_level			level;
 	int				priority;
 	SLIST_ENTRY(cf_saved_freq)	link;
 };
 
 struct cpufreq_softc {
 	struct sx			lock;
 	struct cf_level			curr_level;
 	int				curr_priority;
 	SLIST_HEAD(, cf_saved_freq)	saved_freq;
 	struct cf_level_lst		all_levels;
 	int				all_count;
 	int				max_mhz;
 	device_t			dev;
 	device_t			cf_drv_dev;
 	struct sysctl_ctx_list		sysctl_ctx;
 	struct task			startup_task;
 	struct cf_level			*levels_buf;
 };
 
 struct cf_setting_array {
 	struct cf_setting		sets[MAX_SETTINGS];
 	int				count;
 	TAILQ_ENTRY(cf_setting_array)	link;
 };
 
 TAILQ_HEAD(cf_setting_lst, cf_setting_array);
 
 #define CF_MTX_INIT(x)		sx_init((x), "cpufreq lock")
 #define CF_MTX_LOCK(x)		sx_xlock((x))
 #define CF_MTX_UNLOCK(x)	sx_xunlock((x))
 #define CF_MTX_ASSERT(x)	sx_assert((x), SX_XLOCKED)
 
 #define CF_DEBUG(msg...)	do {		\
 	if (cf_verbose)				\
 		printf("cpufreq: " msg);	\
 	} while (0)
 
+static int	cpufreq_probe(device_t dev);
 static int	cpufreq_attach(device_t dev);
 static void	cpufreq_startup_task(void *ctx, int pending);
 static int	cpufreq_detach(device_t dev);
 static int	cf_set_method(device_t dev, const struct cf_level *level,
 		    int priority);
 static int	cf_get_method(device_t dev, struct cf_level *level);
 static int	cf_levels_method(device_t dev, struct cf_level *levels,
 		    int *count);
 static int	cpufreq_insert_abs(struct cpufreq_softc *sc,
 		    struct cf_setting *sets, int count);
 static int	cpufreq_expand_set(struct cpufreq_softc *sc,
 		    struct cf_setting_array *set_arr);
 static struct cf_level *cpufreq_dup_set(struct cpufreq_softc *sc,
 		    struct cf_level *dup, struct cf_setting *set);
 static int	cpufreq_curr_sysctl(SYSCTL_HANDLER_ARGS);
 static int	cpufreq_levels_sysctl(SYSCTL_HANDLER_ARGS);
 static int	cpufreq_settings_sysctl(SYSCTL_HANDLER_ARGS);
 
 static device_method_t cpufreq_methods[] = {
-	DEVMETHOD(device_probe,		bus_generic_probe),
+	DEVMETHOD(device_probe,		cpufreq_probe),
 	DEVMETHOD(device_attach,	cpufreq_attach),
 	DEVMETHOD(device_detach,	cpufreq_detach),
 
         DEVMETHOD(cpufreq_set,		cf_set_method),
         DEVMETHOD(cpufreq_get,		cf_get_method),
         DEVMETHOD(cpufreq_levels,	cf_levels_method),
 	{0, 0}
 };
 
 static driver_t cpufreq_driver = {
 	"cpufreq", cpufreq_methods, sizeof(struct cpufreq_softc)
 };
 
 DRIVER_MODULE(cpufreq, cpu, cpufreq_driver, 0, 0);
 
 static int		cf_lowest_freq;
 static int		cf_verbose;
 static SYSCTL_NODE(_debug, OID_AUTO, cpufreq, CTLFLAG_RD | CTLFLAG_MPSAFE, NULL,
     "cpufreq debugging");
 SYSCTL_INT(_debug_cpufreq, OID_AUTO, lowest, CTLFLAG_RWTUN, &cf_lowest_freq, 1,
     "Don't provide levels below this frequency.");
 SYSCTL_INT(_debug_cpufreq, OID_AUTO, verbose, CTLFLAG_RWTUN, &cf_verbose, 1,
     "Print verbose debugging messages");
 
+static int
+cpufreq_probe(device_t dev)
+{
+	device_set_desc(dev, "CPU frequency control");
+	return (BUS_PROBE_DEFAULT);
+}
+
 /*
  * This is called as the result of a hardware specific frequency control driver
  * calling cpufreq_register. It provides a general interface for system wide
  * frequency controls and operates on a per cpu basis.
  */
 static int
 cpufreq_attach(device_t dev)
 {
 	struct cpufreq_softc *sc;
 	struct pcpu *pc;
 	device_t parent;
 	uint64_t rate;
 
 	CF_DEBUG("initializing %s\n", device_get_nameunit(dev));
 	sc = device_get_softc(dev);
 	parent = device_get_parent(dev);
 	sc->dev = dev;
 	sysctl_ctx_init(&sc->sysctl_ctx);
 	TAILQ_INIT(&sc->all_levels);
 	CF_MTX_INIT(&sc->lock);
 	sc->curr_level.total_set.freq = CPUFREQ_VAL_UNKNOWN;
 	SLIST_INIT(&sc->saved_freq);
 	/* Try to get nominal CPU freq to use it as maximum later if needed */
 	sc->max_mhz = cpu_get_nominal_mhz(dev);
 	/* If that fails, try to measure the current rate */
 	if (sc->max_mhz <= 0) {
 		CF_DEBUG("Unable to obtain nominal frequency.\n");
 		pc = cpu_get_pcpu(dev);
 		if (cpu_est_clockrate(pc->pc_cpuid, &rate) == 0)
 			sc->max_mhz = rate / 1000000;
 		else
 			sc->max_mhz = CPUFREQ_VAL_UNKNOWN;
 	}
 
 	CF_DEBUG("initializing one-time data for %s\n",
 	    device_get_nameunit(dev));
 	sc->levels_buf = malloc(CF_MAX_LEVELS * sizeof(*sc->levels_buf),
 	    M_DEVBUF, M_WAITOK);
 	SYSCTL_ADD_PROC(&sc->sysctl_ctx,
 	    SYSCTL_CHILDREN(device_get_sysctl_tree(parent)),
 	    OID_AUTO, "freq", CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
 	    sc, 0, cpufreq_curr_sysctl, "I", "Current CPU frequency");
 	SYSCTL_ADD_PROC(&sc->sysctl_ctx,
 	    SYSCTL_CHILDREN(device_get_sysctl_tree(parent)),
 	    OID_AUTO, "freq_levels",
 	    CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_NEEDGIANT, sc, 0,
 	    cpufreq_levels_sysctl, "A", "CPU frequency levels");
 
 	/*
 	 * Queue a one-shot broadcast that levels have changed.
 	 * It will run once the system has completed booting.
 	 */
 	TASK_INIT(&sc->startup_task, 0, cpufreq_startup_task, dev);
 	taskqueue_enqueue(taskqueue_thread, &sc->startup_task);
 
 	return (0);
 }
 
 /* Handle any work to be done for all drivers that attached during boot. */
 static void 
 cpufreq_startup_task(void *ctx, int pending)
 {
 
 	cpufreq_settings_changed((device_t)ctx);
 }
 
 static int
 cpufreq_detach(device_t dev)
 {
 	struct cpufreq_softc *sc;
 	struct cf_saved_freq *saved_freq;
 
 	CF_DEBUG("shutdown %s\n", device_get_nameunit(dev));
 	sc = device_get_softc(dev);
 	sysctl_ctx_free(&sc->sysctl_ctx);
 
 	while ((saved_freq = SLIST_FIRST(&sc->saved_freq)) != NULL) {
 		SLIST_REMOVE_HEAD(&sc->saved_freq, link);
 		free(saved_freq, M_TEMP);
 	}
 
 	free(sc->levels_buf, M_DEVBUF);
 
 	return (0);
 }
 
 static int
 cf_set_method(device_t dev, const struct cf_level *level, int priority)
 {
 	struct cpufreq_softc *sc;
 	const struct cf_setting *set;
 	struct cf_saved_freq *saved_freq, *curr_freq;
 	struct pcpu *pc;
 	int error, i;
 	u_char pri;
 
 	sc = device_get_softc(dev);
 	error = 0;
 	set = NULL;
 	saved_freq = NULL;
 
 	/* We are going to change levels so notify the pre-change handler. */
 	EVENTHANDLER_INVOKE(cpufreq_pre_change, level, &error);
 	if (error != 0) {
 		EVENTHANDLER_INVOKE(cpufreq_post_change, level, error);
 		return (error);
 	}
 
 	CF_MTX_LOCK(&sc->lock);
 
 #ifdef SMP
 #ifdef EARLY_AP_STARTUP
 	MPASS(mp_ncpus == 1 || smp_started);
 #else
 	/*
 	 * If still booting and secondary CPUs not started yet, don't allow
 	 * changing the frequency until they're online.  This is because we
 	 * can't switch to them using sched_bind() and thus we'd only be
 	 * switching the main CPU.  XXXTODO: Need to think more about how to
 	 * handle having different CPUs at different frequencies.  
 	 */
 	if (mp_ncpus > 1 && !smp_started) {
 		device_printf(dev, "rejecting change, SMP not started yet\n");
 		error = ENXIO;
 		goto out;
 	}
 #endif
 #endif /* SMP */
 
 	/*
 	 * If the requested level has a lower priority, don't allow
 	 * the new level right now.
 	 */
 	if (priority < sc->curr_priority) {
 		CF_DEBUG("ignoring, curr prio %d less than %d\n", priority,
 		    sc->curr_priority);
 		error = EPERM;
 		goto out;
 	}
 
 	/*
 	 * If the caller didn't specify a level and one is saved, prepare to
 	 * restore the saved level.  If none has been saved, return an error.
 	 */
 	if (level == NULL) {
 		saved_freq = SLIST_FIRST(&sc->saved_freq);
 		if (saved_freq == NULL) {
 			CF_DEBUG("NULL level, no saved level\n");
 			error = ENXIO;
 			goto out;
 		}
 		level = &saved_freq->level;
 		priority = saved_freq->priority;
 		CF_DEBUG("restoring saved level, freq %d prio %d\n",
 		    level->total_set.freq, priority);
 	}
 
 	/* Reject levels that are below our specified threshold. */
 	if (level->total_set.freq < cf_lowest_freq) {
 		CF_DEBUG("rejecting freq %d, less than %d limit\n",
 		    level->total_set.freq, cf_lowest_freq);
 		error = EINVAL;
 		goto out;
 	}
 
 	/* If already at this level, just return. */
 	if (sc->curr_level.total_set.freq == level->total_set.freq) {
 		CF_DEBUG("skipping freq %d, same as current level %d\n",
 		    level->total_set.freq, sc->curr_level.total_set.freq);
 		goto skip;
 	}
 
 	/* First, set the absolute frequency via its driver. */
 	set = &level->abs_set;
 	if (set->dev) {
 		if (!device_is_attached(set->dev)) {
 			error = ENXIO;
 			goto out;
 		}
 
 		/* Bind to the target CPU before switching. */
 		pc = cpu_get_pcpu(set->dev);
 
 		/* Skip settings if CPU is not started. */
 		if (pc == NULL) {
 			error = 0;
 			goto out;
 		}
 		thread_lock(curthread);
 		pri = curthread->td_priority;
 		sched_prio(curthread, PRI_MIN);
 		sched_bind(curthread, pc->pc_cpuid);
 		thread_unlock(curthread);
 		CF_DEBUG("setting abs freq %d on %s (cpu %d)\n", set->freq,
 		    device_get_nameunit(set->dev), PCPU_GET(cpuid));
 		error = CPUFREQ_DRV_SET(set->dev, set);
 		thread_lock(curthread);
 		sched_unbind(curthread);
 		sched_prio(curthread, pri);
 		thread_unlock(curthread);
 		if (error) {
 			goto out;
 		}
 	}
 
 	/* Next, set any/all relative frequencies via their drivers. */
 	for (i = 0; i < level->rel_count; i++) {
 		set = &level->rel_set[i];
 		if (!device_is_attached(set->dev)) {
 			error = ENXIO;
 			goto out;
 		}
 
 		/* Bind to the target CPU before switching. */
 		pc = cpu_get_pcpu(set->dev);
 		thread_lock(curthread);
 		pri = curthread->td_priority;
 		sched_prio(curthread, PRI_MIN);
 		sched_bind(curthread, pc->pc_cpuid);
 		thread_unlock(curthread);
 		CF_DEBUG("setting rel freq %d on %s (cpu %d)\n", set->freq,
 		    device_get_nameunit(set->dev), PCPU_GET(cpuid));
 		error = CPUFREQ_DRV_SET(set->dev, set);
 		thread_lock(curthread);
 		sched_unbind(curthread);
 		sched_prio(curthread, pri);
 		thread_unlock(curthread);
 		if (error) {
 			/* XXX Back out any successful setting? */
 			goto out;
 		}
 	}
 
 skip:
 	/*
 	 * Before recording the current level, check if we're going to a
 	 * higher priority.  If so, save the previous level and priority.
 	 */
 	if (sc->curr_level.total_set.freq != CPUFREQ_VAL_UNKNOWN &&
 	    priority > sc->curr_priority) {
 		CF_DEBUG("saving level, freq %d prio %d\n",
 		    sc->curr_level.total_set.freq, sc->curr_priority);
 		curr_freq = malloc(sizeof(*curr_freq), M_TEMP, M_NOWAIT);
 		if (curr_freq == NULL) {
 			error = ENOMEM;
 			goto out;
 		}
 		curr_freq->level = sc->curr_level;
 		curr_freq->priority = sc->curr_priority;
 		SLIST_INSERT_HEAD(&sc->saved_freq, curr_freq, link);
 	}
 	sc->curr_level = *level;
 	sc->curr_priority = priority;
 
 	/* If we were restoring a saved state, reset it to "unused". */
 	if (saved_freq != NULL) {
 		CF_DEBUG("resetting saved level\n");
 		sc->curr_level.total_set.freq = CPUFREQ_VAL_UNKNOWN;
 		SLIST_REMOVE_HEAD(&sc->saved_freq, link);
 		free(saved_freq, M_TEMP);
 	}
 
 out:
 	CF_MTX_UNLOCK(&sc->lock);
 
 	/*
 	 * We changed levels (or attempted to) so notify the post-change
 	 * handler of new frequency or error.
 	 */
 	EVENTHANDLER_INVOKE(cpufreq_post_change, level, error);
 	if (error && set)
 		device_printf(set->dev, "set freq failed, err %d\n", error);
 
 	return (error);
 }
 
 static int
 cpufreq_get_frequency(device_t dev)
 {
 	struct cf_setting set;
 
 	if (CPUFREQ_DRV_GET(dev, &set) != 0)
 		return (-1);
 
 	return (set.freq);
 }
 
 /* Returns the index into *levels with the match */
 static int
 cpufreq_get_level(device_t dev, struct cf_level *levels, int count)
 {
 	int i, freq;
 
 	if ((freq = cpufreq_get_frequency(dev)) < 0)
 		return (-1);
 	for (i = 0; i < count; i++)
 		if (freq == levels[i].total_set.freq)
 			return (i);
 
 	return (-1);
 }
 
 /*
  * Used by the cpufreq core, this function will populate *level with the current
  * frequency as either determined by a cached value sc->curr_level, or in the
  * case the lower level driver has set the CPUFREQ_FLAG_UNCACHED flag, it will
  * obtain the frequency from the driver itself.
  */
 static int
 cf_get_method(device_t dev, struct cf_level *level)
 {
 	struct cpufreq_softc *sc;
 	struct cf_level *levels;
 	struct cf_setting *curr_set;
 	struct pcpu *pc;
 	int bdiff, count, diff, error, i, type;
 	uint64_t rate;
 
 	sc = device_get_softc(dev);
 	error = 0;
 	levels = NULL;
 
 	/*
 	 * If we already know the current frequency, and the driver didn't ask
 	 * for uncached usage, we're done.
 	 */
 	CF_MTX_LOCK(&sc->lock);
 	curr_set = &sc->curr_level.total_set;
 	error = CPUFREQ_DRV_TYPE(sc->cf_drv_dev, &type);
 	if (error == 0 && (type & CPUFREQ_FLAG_UNCACHED)) {
 		struct cf_setting set;
 
 		/*
 		 * If the driver wants to always report back the real frequency,
 		 * first try the driver and if that fails, fall back to
 		 * estimating.
 		 */
 		if (CPUFREQ_DRV_GET(sc->cf_drv_dev, &set) == 0) {
 			sc->curr_level.total_set = set;
 			CF_DEBUG("get returning immediate freq %d\n",
 			    curr_set->freq);
 			goto out;
 		}
 	} else if (curr_set->freq != CPUFREQ_VAL_UNKNOWN) {
 		CF_DEBUG("get returning known freq %d\n", curr_set->freq);
 		error = 0;
 		goto out;
 	}
 	CF_MTX_UNLOCK(&sc->lock);
 
 	/*
 	 * We need to figure out the current level.  Loop through every
 	 * driver, getting the current setting.  Then, attempt to get a best
 	 * match of settings against each level.
 	 */
 	count = CF_MAX_LEVELS;
 	levels = malloc(count * sizeof(*levels), M_TEMP, M_NOWAIT);
 	if (levels == NULL)
 		return (ENOMEM);
 	error = CPUFREQ_LEVELS(sc->dev, levels, &count);
 	if (error) {
 		if (error == E2BIG)
 			printf("cpufreq: need to increase CF_MAX_LEVELS\n");
 		free(levels, M_TEMP);
 		return (error);
 	}
 
 	/*
 	 * Reacquire the lock and search for the given level.
 	 *
 	 * XXX Note: this is not quite right since we really need to go
 	 * through each level and compare both absolute and relative
 	 * settings for each driver in the system before making a match.
 	 * The estimation code below catches this case though.
 	 */
 	CF_MTX_LOCK(&sc->lock);
 	i = cpufreq_get_level(sc->cf_drv_dev, levels, count);
 	if (i >= 0)
 		sc->curr_level = levels[i];
 	else
 		CF_DEBUG("Couldn't find supported level for %s\n",
 		    device_get_nameunit(sc->cf_drv_dev));
 
 	if (curr_set->freq != CPUFREQ_VAL_UNKNOWN) {
 		CF_DEBUG("get matched freq %d from drivers\n", curr_set->freq);
 		goto out;
 	}
 
 	/*
 	 * We couldn't find an exact match, so attempt to estimate and then
 	 * match against a level.
 	 */
 	pc = cpu_get_pcpu(dev);
 	if (pc == NULL) {
 		error = ENXIO;
 		goto out;
 	}
 	cpu_est_clockrate(pc->pc_cpuid, &rate);
 	rate /= 1000000;
 	bdiff = 1 << 30;
 	for (i = 0; i < count; i++) {
 		diff = abs(levels[i].total_set.freq - rate);
 		if (diff < bdiff) {
 			bdiff = diff;
 			sc->curr_level = levels[i];
 		}
 	}
 	CF_DEBUG("get estimated freq %d\n", curr_set->freq);
 
 out:
 	if (error == 0)
 		*level = sc->curr_level;
 
 	CF_MTX_UNLOCK(&sc->lock);
 	if (levels)
 		free(levels, M_TEMP);
 	return (error);
 }
 
 /*
  * Either directly obtain settings from the cpufreq driver, or build a list of
  * relative settings to be integrated later against an absolute max.
  */
 static int
 cpufreq_add_levels(device_t cf_dev, struct cf_setting_lst *rel_sets)
 {
 	struct cf_setting_array *set_arr;
 	struct cf_setting *sets;
 	device_t dev;
 	struct cpufreq_softc *sc;
 	int type, set_count, error;
 
 	sc = device_get_softc(cf_dev);
 	dev = sc->cf_drv_dev;
 
 	/* Skip devices that aren't ready. */
 	if (!device_is_attached(cf_dev))
 		return (0);
 
 	/*
 	 * Get settings, skipping drivers that offer no settings or
 	 * provide settings for informational purposes only.
 	 */
 	error = CPUFREQ_DRV_TYPE(dev, &type);
 	if (error != 0 || (type & CPUFREQ_FLAG_INFO_ONLY)) {
 		if (error == 0) {
 			CF_DEBUG("skipping info-only driver %s\n",
 			    device_get_nameunit(cf_dev));
 		}
 		return (error);
 	}
 
 	sets = malloc(MAX_SETTINGS * sizeof(*sets), M_TEMP, M_NOWAIT);
 	if (sets == NULL)
 		return (ENOMEM);
 
 	set_count = MAX_SETTINGS;
 	error = CPUFREQ_DRV_SETTINGS(dev, sets, &set_count);
 	if (error != 0 || set_count == 0)
 		goto out;
 
 	/* Add the settings to our absolute/relative lists. */
 	switch (type & CPUFREQ_TYPE_MASK) {
 	case CPUFREQ_TYPE_ABSOLUTE:
 		error = cpufreq_insert_abs(sc, sets, set_count);
 		break;
 	case CPUFREQ_TYPE_RELATIVE:
 		CF_DEBUG("adding %d relative settings\n", set_count);
 		set_arr = malloc(sizeof(*set_arr), M_TEMP, M_NOWAIT);
 		if (set_arr == NULL) {
 			error = ENOMEM;
 			goto out;
 		}
 		bcopy(sets, set_arr->sets, set_count * sizeof(*sets));
 		set_arr->count = set_count;
 		TAILQ_INSERT_TAIL(rel_sets, set_arr, link);
 		break;
 	default:
 		error = EINVAL;
 	}
 
 out:
 	free(sets, M_TEMP);
 	return (error);
 }
 
 static int
 cf_levels_method(device_t dev, struct cf_level *levels, int *count)
 {
 	struct cf_setting_array *set_arr;
 	struct cf_setting_lst rel_sets;
 	struct cpufreq_softc *sc;
 	struct cf_level *lev;
 	struct pcpu *pc;
 	int error, i;
 	uint64_t rate;
 
 	if (levels == NULL || count == NULL)
 		return (EINVAL);
 
 	TAILQ_INIT(&rel_sets);
 	sc = device_get_softc(dev);
 
 	CF_MTX_LOCK(&sc->lock);
 	error = cpufreq_add_levels(sc->dev, &rel_sets);
 	if (error)
 		goto out;
 
 	/*
 	 * If there are no absolute levels, create a fake one at 100%.  We
 	 * then cache the clockrate for later use as our base frequency.
 	 */
 	if (TAILQ_EMPTY(&sc->all_levels)) {
 		struct cf_setting set;
 
 		CF_DEBUG("No absolute levels returned by driver\n");
 
 		if (sc->max_mhz == CPUFREQ_VAL_UNKNOWN) {
 			sc->max_mhz = cpu_get_nominal_mhz(dev);
 			/*
 			 * If the CPU can't report a rate for 100%, hope
 			 * the CPU is running at its nominal rate right now,
 			 * and use that instead.
 			 */
 			if (sc->max_mhz <= 0) {
 				pc = cpu_get_pcpu(dev);
 				cpu_est_clockrate(pc->pc_cpuid, &rate);
 				sc->max_mhz = rate / 1000000;
 			}
 		}
 		memset(&set, CPUFREQ_VAL_UNKNOWN, sizeof(set));
 		set.freq = sc->max_mhz;
 		set.dev = NULL;
 		error = cpufreq_insert_abs(sc, &set, 1);
 		if (error)
 			goto out;
 	}
 
 	/* Create a combined list of absolute + relative levels. */
 	TAILQ_FOREACH(set_arr, &rel_sets, link)
 		cpufreq_expand_set(sc, set_arr);
 
 	/* If the caller doesn't have enough space, return the actual count. */
 	if (sc->all_count > *count) {
 		*count = sc->all_count;
 		error = E2BIG;
 		goto out;
 	}
 
 	/* Finally, output the list of levels. */
 	i = 0;
 	TAILQ_FOREACH(lev, &sc->all_levels, link) {
 		/* Skip levels that have a frequency that is too low. */
 		if (lev->total_set.freq < cf_lowest_freq) {
 			sc->all_count--;
 			continue;
 		}
 
 		levels[i] = *lev;
 		i++;
 	}
 	*count = sc->all_count;
 	error = 0;
 
 out:
 	/* Clear all levels since we regenerate them each time. */
 	while ((lev = TAILQ_FIRST(&sc->all_levels)) != NULL) {
 		TAILQ_REMOVE(&sc->all_levels, lev, link);
 		free(lev, M_TEMP);
 	}
 	sc->all_count = 0;
 
 	CF_MTX_UNLOCK(&sc->lock);
 	while ((set_arr = TAILQ_FIRST(&rel_sets)) != NULL) {
 		TAILQ_REMOVE(&rel_sets, set_arr, link);
 		free(set_arr, M_TEMP);
 	}
 	return (error);
 }
 
 /*
  * Create levels for an array of absolute settings and insert them in
  * sorted order in the specified list.
  */
 static int
 cpufreq_insert_abs(struct cpufreq_softc *sc, struct cf_setting *sets,
     int count)
 {
 	struct cf_level_lst *list;
 	struct cf_level *level, *search;
 	int i, inserted;
 
 	CF_MTX_ASSERT(&sc->lock);
 
 	list = &sc->all_levels;
 	for (i = 0; i < count; i++) {
 		level = malloc(sizeof(*level), M_TEMP, M_NOWAIT | M_ZERO);
 		if (level == NULL)
 			return (ENOMEM);
 		level->abs_set = sets[i];
 		level->total_set = sets[i];
 		level->total_set.dev = NULL;
 		sc->all_count++;
 		inserted = 0;
 
 		if (TAILQ_EMPTY(list)) {
 			CF_DEBUG("adding abs setting %d at head\n",
 			    sets[i].freq);
 			TAILQ_INSERT_HEAD(list, level, link);
 			continue;
 		}
 
 		TAILQ_FOREACH_REVERSE(search, list, cf_level_lst, link)
 			if (sets[i].freq <= search->total_set.freq) {
 				CF_DEBUG("adding abs setting %d after %d\n",
 				    sets[i].freq, search->total_set.freq);
 				TAILQ_INSERT_AFTER(list, search, level, link);
 				inserted = 1;
 				break;
 			}
 
 		if (inserted == 0) {
 			TAILQ_FOREACH(search, list, link)
 				if (sets[i].freq >= search->total_set.freq) {
 					CF_DEBUG("adding abs setting %d before %d\n",
 					    sets[i].freq, search->total_set.freq);
 					TAILQ_INSERT_BEFORE(search, level, link);
 					break;
 				}
 		}
 	}
 
 	return (0);
 }
 
 /*
  * Expand a group of relative settings, creating derived levels from them.
  */
 static int
 cpufreq_expand_set(struct cpufreq_softc *sc, struct cf_setting_array *set_arr)
 {
 	struct cf_level *fill, *search;
 	struct cf_setting *set;
 	int i;
 
 	CF_MTX_ASSERT(&sc->lock);
 
 	/*
 	 * Walk the set of all existing levels in reverse.  This is so we
 	 * create derived states from the lowest absolute settings first
 	 * and discard duplicates created from higher absolute settings.
 	 * For instance, a level of 50 Mhz derived from 100 Mhz + 50% is
 	 * preferable to 200 Mhz + 25% because absolute settings are more
 	 * efficient since they often change the voltage as well.
 	 */
 	TAILQ_FOREACH_REVERSE(search, &sc->all_levels, cf_level_lst, link) {
 		/* Add each setting to the level, duplicating if necessary. */
 		for (i = 0; i < set_arr->count; i++) {
 			set = &set_arr->sets[i];
 
 			/*
 			 * If this setting is less than 100%, split the level
 			 * into two and add this setting to the new level.
 			 */
 			fill = search;
 			if (set->freq < 10000) {
 				fill = cpufreq_dup_set(sc, search, set);
 
 				/*
 				 * The new level was a duplicate of an existing
 				 * level or its absolute setting is too high
 				 * so we freed it.  For example, we discard a
 				 * derived level of 1000 MHz/25% if a level
 				 * of 500 MHz/100% already exists.
 				 */
 				if (fill == NULL)
 					break;
 			}
 
 			/* Add this setting to the existing or new level. */
 			KASSERT(fill->rel_count < MAX_SETTINGS,
 			    ("cpufreq: too many relative drivers (%d)",
 			    MAX_SETTINGS));
 			fill->rel_set[fill->rel_count] = *set;
 			fill->rel_count++;
 			CF_DEBUG(
 			"expand set added rel setting %d%% to %d level\n",
 			    set->freq / 100, fill->total_set.freq);
 		}
 	}
 
 	return (0);
 }
 
 static struct cf_level *
 cpufreq_dup_set(struct cpufreq_softc *sc, struct cf_level *dup,
     struct cf_setting *set)
 {
 	struct cf_level_lst *list;
 	struct cf_level *fill, *itr;
 	struct cf_setting *fill_set, *itr_set;
 	int i;
 
 	CF_MTX_ASSERT(&sc->lock);
 
 	/*
 	 * Create a new level, copy it from the old one, and update the
 	 * total frequency and power by the percentage specified in the
 	 * relative setting.
 	 */
 	fill = malloc(sizeof(*fill), M_TEMP, M_NOWAIT);
 	if (fill == NULL)
 		return (NULL);
 	*fill = *dup;
 	fill_set = &fill->total_set;
 	fill_set->freq =
 	    ((uint64_t)fill_set->freq * set->freq) / 10000;
 	if (fill_set->power != CPUFREQ_VAL_UNKNOWN) {
 		fill_set->power = ((uint64_t)fill_set->power * set->freq)
 		    / 10000;
 	}
 	if (set->lat != CPUFREQ_VAL_UNKNOWN) {
 		if (fill_set->lat != CPUFREQ_VAL_UNKNOWN)
 			fill_set->lat += set->lat;
 		else
 			fill_set->lat = set->lat;
 	}
 	CF_DEBUG("dup set considering derived setting %d\n", fill_set->freq);
 
 	/*
 	 * If we copied an old level that we already modified (say, at 100%),
 	 * we need to remove that setting before adding this one.  Since we
 	 * process each setting array in order, we know any settings for this
 	 * driver will be found at the end.
 	 */
 	for (i = fill->rel_count; i != 0; i--) {
 		if (fill->rel_set[i - 1].dev != set->dev)
 			break;
 		CF_DEBUG("removed last relative driver: %s\n",
 		    device_get_nameunit(set->dev));
 		fill->rel_count--;
 	}
 
 	/*
 	 * Insert the new level in sorted order.  If it is a duplicate of an
 	 * existing level (1) or has an absolute setting higher than the
 	 * existing level (2), do not add it.  We can do this since any such
 	 * level is guaranteed use less power.  For example (1), a level with
 	 * one absolute setting of 800 Mhz uses less power than one composed
 	 * of an absolute setting of 1600 Mhz and a relative setting at 50%.
 	 * Also for example (2), a level of 800 Mhz/75% is preferable to
 	 * 1600 Mhz/25% even though the latter has a lower total frequency.
 	 */
 	list = &sc->all_levels;
 	KASSERT(!TAILQ_EMPTY(list), ("all levels list empty in dup set"));
 	TAILQ_FOREACH_REVERSE(itr, list, cf_level_lst, link) {
 		itr_set = &itr->total_set;
 		if (CPUFREQ_CMP(fill_set->freq, itr_set->freq)) {
 			CF_DEBUG("dup set rejecting %d (dupe)\n",
 			    fill_set->freq);
 			itr = NULL;
 			break;
 		} else if (fill_set->freq < itr_set->freq) {
 			if (fill->abs_set.freq <= itr->abs_set.freq) {
 				CF_DEBUG(
 			"dup done, inserting new level %d after %d\n",
 				    fill_set->freq, itr_set->freq);
 				TAILQ_INSERT_AFTER(list, itr, fill, link);
 				sc->all_count++;
 			} else {
 				CF_DEBUG("dup set rejecting %d (abs too big)\n",
 				    fill_set->freq);
 				itr = NULL;
 			}
 			break;
 		}
 	}
 
 	/* We didn't find a good place for this new level so free it. */
 	if (itr == NULL) {
 		CF_DEBUG("dup set freeing new level %d (not optimal)\n",
 		    fill_set->freq);
 		free(fill, M_TEMP);
 		fill = NULL;
 	}
 
 	return (fill);
 }
 
 static int
 cpufreq_curr_sysctl(SYSCTL_HANDLER_ARGS)
 {
 	struct cpufreq_softc *sc;
 	struct cf_level *levels;
 	int best, count, diff, bdiff, devcount, error, freq, i, n;
 	device_t *devs;
 
 	devs = NULL;
 	sc = oidp->oid_arg1;
 	levels = sc->levels_buf;
 
 	error = CPUFREQ_GET(sc->dev, &levels[0]);
 	if (error)
 		goto out;
 	freq = levels[0].total_set.freq;
 	error = sysctl_handle_int(oidp, &freq, 0, req);
 	if (error != 0 || req->newptr == NULL)
 		goto out;
 
 	/*
 	 * While we only call cpufreq_get() on one device (assuming all
 	 * CPUs have equal levels), we call cpufreq_set() on all CPUs.
 	 * This is needed for some MP systems.
 	 */
 	error = devclass_get_devices(devclass_find("cpufreq"), &devs, &devcount);
 	if (error)
 		goto out;
 	for (n = 0; n < devcount; n++) {
 		count = CF_MAX_LEVELS;
 		error = CPUFREQ_LEVELS(devs[n], levels, &count);
 		if (error) {
 			if (error == E2BIG)
 				printf(
 			"cpufreq: need to increase CF_MAX_LEVELS\n");
 			break;
 		}
 		best = 0;
 		bdiff = 1 << 30;
 		for (i = 0; i < count; i++) {
 			diff = abs(levels[i].total_set.freq - freq);
 			if (diff < bdiff) {
 				bdiff = diff;
 				best = i;
 			}
 		}
 		error = CPUFREQ_SET(devs[n], &levels[best], CPUFREQ_PRIO_USER);
 	}
 
 out:
 	if (devs)
 		free(devs, M_TEMP);
 	return (error);
 }
 
 static int
 cpufreq_levels_sysctl(SYSCTL_HANDLER_ARGS)
 {
 	struct cpufreq_softc *sc;
 	struct cf_level *levels;
 	struct cf_setting *set;
 	struct sbuf sb;
 	int count, error, i;
 
 	sc = oidp->oid_arg1;
 	sbuf_new(&sb, NULL, 128, SBUF_AUTOEXTEND);
 
 	/* Get settings from the device and generate the output string. */
 	count = CF_MAX_LEVELS;
 	levels = sc->levels_buf;
 	if (levels == NULL) {
 		sbuf_delete(&sb);
 		return (ENOMEM);
 	}
 	error = CPUFREQ_LEVELS(sc->dev, levels, &count);
 	if (error) {
 		if (error == E2BIG)
 			printf("cpufreq: need to increase CF_MAX_LEVELS\n");
 		goto out;
 	}
 	if (count) {
 		for (i = 0; i < count; i++) {
 			set = &levels[i].total_set;
 			sbuf_printf(&sb, "%d/%d ", set->freq, set->power);
 		}
 	} else
 		sbuf_cpy(&sb, "0");
 	sbuf_trim(&sb);
 	sbuf_finish(&sb);
 	error = sysctl_handle_string(oidp, sbuf_data(&sb), sbuf_len(&sb), req);
 
 out:
 	sbuf_delete(&sb);
 	return (error);
 }
 
 static int
 cpufreq_settings_sysctl(SYSCTL_HANDLER_ARGS)
 {
 	device_t dev;
 	struct cf_setting *sets;
 	struct sbuf sb;
 	int error, i, set_count;
 
 	dev = oidp->oid_arg1;
 	sbuf_new(&sb, NULL, 128, SBUF_AUTOEXTEND);
 
 	/* Get settings from the device and generate the output string. */
 	set_count = MAX_SETTINGS;
 	sets = malloc(set_count * sizeof(*sets), M_TEMP, M_NOWAIT);
 	if (sets == NULL) {
 		sbuf_delete(&sb);
 		return (ENOMEM);
 	}
 	error = CPUFREQ_DRV_SETTINGS(dev, sets, &set_count);
 	if (error)
 		goto out;
 	if (set_count) {
 		for (i = 0; i < set_count; i++)
 			sbuf_printf(&sb, "%d/%d ", sets[i].freq, sets[i].power);
 	} else
 		sbuf_cpy(&sb, "0");
 	sbuf_trim(&sb);
 	sbuf_finish(&sb);
 	error = sysctl_handle_string(oidp, sbuf_data(&sb), sbuf_len(&sb), req);
 
 out:
 	free(sets, M_TEMP);
 	sbuf_delete(&sb);
 	return (error);
 }
 
 static void
 cpufreq_add_freq_driver_sysctl(device_t cf_dev)
 {
 	struct cpufreq_softc *sc;
 
 	sc = device_get_softc(cf_dev);
 	SYSCTL_ADD_CONST_STRING(&sc->sysctl_ctx,
 	    SYSCTL_CHILDREN(device_get_sysctl_tree(cf_dev)), OID_AUTO,
 	    "freq_driver", CTLFLAG_RD, device_get_nameunit(sc->cf_drv_dev),
 	    "cpufreq driver used by this cpu");
 }
 
 int
 cpufreq_register(device_t dev)
 {
 	struct cpufreq_softc *sc;
 	device_t cf_dev, cpu_dev;
 	int error;
 
 	/* Add a sysctl to get each driver's settings separately. */
 	SYSCTL_ADD_PROC(device_get_sysctl_ctx(dev),
 	    SYSCTL_CHILDREN(device_get_sysctl_tree(dev)),
 	    OID_AUTO, "freq_settings",
 	    CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_NEEDGIANT, dev, 0,
 	    cpufreq_settings_sysctl, "A", "CPU frequency driver settings");
 
 	/*
 	 * Add only one cpufreq device to each CPU.  Currently, all CPUs
 	 * must offer the same levels and be switched at the same time.
 	 */
 	cpu_dev = device_get_parent(dev);
 	if ((cf_dev = device_find_child(cpu_dev, "cpufreq", -1))) {
 		sc = device_get_softc(cf_dev);
 		sc->max_mhz = CPUFREQ_VAL_UNKNOWN;
 		MPASS(sc->cf_drv_dev != NULL);
 		return (0);
 	}
 
 	/* Add the child device and possibly sysctls. */
 	cf_dev = BUS_ADD_CHILD(cpu_dev, 0, "cpufreq", device_get_unit(cpu_dev));
 	if (cf_dev == NULL)
 		return (ENOMEM);
 	device_quiet(cf_dev);
 
 	error = device_probe_and_attach(cf_dev);
 	if (error)
 		return (error);
 
 	sc = device_get_softc(cf_dev);
 	sc->cf_drv_dev = dev;
 	cpufreq_add_freq_driver_sysctl(cf_dev);
 	return (error);
 }
 
 int
 cpufreq_unregister(device_t dev)
 {
 	device_t cf_dev;
 	struct cpufreq_softc *sc __diagused;
 
 	/*
 	 * If this is the last cpufreq child device, remove the control
 	 * device as well.  We identify cpufreq children by calling a method
 	 * they support.
 	 */
 	cf_dev = device_find_child(device_get_parent(dev), "cpufreq", -1);
 	if (cf_dev == NULL) {
 		device_printf(dev,
 	"warning: cpufreq_unregister called with no cpufreq device active\n");
 		return (0);
 	}
 	sc = device_get_softc(cf_dev);
 	MPASS(sc->cf_drv_dev == dev);
 	device_delete_child(device_get_parent(cf_dev), cf_dev);
 
 	return (0);
 }
 
 int
 cpufreq_settings_changed(device_t dev)
 {
 
 	EVENTHANDLER_INVOKE(cpufreq_levels_changed,
 	    device_get_unit(device_get_parent(dev)));
 	return (0);
 }