/*-
 * Copyright (C) 2013-2015 Daisuke Aoyama <aoyama@peach.ne.jp>
 * 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/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/cpu.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/mutex.h>
#include <sys/sema.h>
#include <sys/sysctl.h>

#include <machine/bus.h>
#include <machine/cpu.h>
#include <machine/intr.h>

#include <dev/ofw/ofw_bus.h>
#include <dev/ofw/ofw_bus_subr.h>

#include <arm/broadcom/bcm2835/bcm2835_firmware.h>
#include <arm/broadcom/bcm2835/bcm2835_vcbus.h>

#include "cpufreq_if.h"

#ifdef DEBUG
#define DPRINTF(fmt, ...) do {                  \
        printf("%s:%u: ", __func__, __LINE__);  \
        printf(fmt, ##__VA_ARGS__);             \
} while (0)
#else
#define DPRINTF(fmt, ...)
#endif

#define HZ2MHZ(freq) ((freq) / (1000 * 1000))
#define MHZ2HZ(freq) ((freq) * (1000 * 1000))

#define OFFSET2MVOLT(val) (((val) / 1000))
#define MVOLT2OFFSET(val) (((val) * 1000))
#define DEFAULT_ARM_FREQUENCY    600
#define DEFAULT_LOWEST_FREQ      600
#define DEFAULT_CORE_FREQUENCY   250
#define DEFAULT_SDRAM_FREQUENCY  400
#define TRANSITION_LATENCY      1000
#define MIN_OVER_VOLTAGE         -16
#define MAX_OVER_VOLTAGE           6
#define MSG_ERROR         -999999999
#define MHZSTEP                  100
#define HZSTEP     (MHZ2HZ(MHZSTEP))
#define TZ_ZEROC                2731

#define VC_LOCK(sc) do {                        \
                sema_wait(&vc_sema);            \
        } while (0)
#define VC_UNLOCK(sc) do {                      \
                sema_post(&vc_sema);            \
        } while (0)

/* ARM->VC mailbox property semaphore */
static struct sema vc_sema;

static struct sysctl_ctx_list bcm2835_sysctl_ctx;

struct bcm2835_cpufreq_softc {
        device_t        dev;
        device_t        firmware;
        int             arm_max_freq;
        int             arm_min_freq;
        int             core_max_freq;
        int             core_min_freq;
        int             sdram_max_freq;
        int             sdram_min_freq;
        int             max_voltage_core;
        int             min_voltage_core;

        /* the values written in mbox */
        int             voltage_core;
        int             voltage_sdram;
        int             voltage_sdram_c;
        int             voltage_sdram_i;
        int             voltage_sdram_p;
        int             turbo_mode;

        /* initial hook for waiting mbox intr */
        struct intr_config_hook init_hook;
};

static struct ofw_compat_data compat_data[] = {
        { "broadcom,bcm2835-vc",        1 },
        { "broadcom,bcm2708-vc",        1 },
        { "brcm,bcm2709",       1 },
        { "brcm,bcm2835",       1 },
        { "brcm,bcm2836",       1 },
        { "brcm,bcm2837",       1 },
        { "brcm,bcm2711",       1 },
        { NULL, 0 }
};

static int cpufreq_verbose = 0;
TUNABLE_INT("hw.bcm2835.cpufreq.verbose", &cpufreq_verbose);
static int cpufreq_lowest_freq = DEFAULT_LOWEST_FREQ;
TUNABLE_INT("hw.bcm2835.cpufreq.lowest_freq", &cpufreq_lowest_freq);

#ifdef PROP_DEBUG
static void
bcm2835_dump(const void *data, int len)
{
        const uint8_t *p = (const uint8_t*)data;
        int i;

        printf("dump @ %p:\n", data);
        for (i = 0; i < len; i++) {
                printf("%2.2x ", p[i]);
                if ((i % 4) == 3)
                        printf(" ");
                if ((i % 16) == 15)
                        printf("\n");
        }
        printf("\n");
}
#endif

static int
bcm2835_cpufreq_get_clock_rate(struct bcm2835_cpufreq_softc *sc,
    uint32_t clock_id)
{
        union msg_get_clock_rate_body msg;
        int rate;
        int err;

        /*
         * Get clock rate
         *   Tag: 0x00030002
         *   Request:
         *     Length: 4
         *     Value:
         *       u32: clock id
         *   Response:
         *     Length: 8
         *     Value:
         *       u32: clock id
         *       u32: rate (in Hz)
         */

        /* setup single tag buffer */
        memset(&msg, 0, sizeof(msg));
        msg.req.clock_id = clock_id;

        /* call mailbox property */
        err = bcm2835_firmware_property(sc->firmware,
            BCM2835_FIRMWARE_TAG_GET_CLOCK_RATE, &msg, sizeof(msg));
        if (err) {
                device_printf(sc->dev, "can't get clock rate (id=%u)\n",
                    clock_id);
                return (MSG_ERROR);
        }

        /* result (Hz) */
        rate = (int)msg.resp.rate_hz;
        DPRINTF("clock = %d(Hz)\n", rate);
        return (rate);
}

static int
bcm2835_cpufreq_get_max_clock_rate(struct bcm2835_cpufreq_softc *sc,
    uint32_t clock_id)
{
        union msg_get_clock_rate_body msg;
        int rate;
        int err;

        /*
         * Get max clock rate
         *   Tag: 0x00030004
         *   Request:
         *     Length: 4
         *     Value:
         *       u32: clock id
         *   Response:
         *     Length: 8
         *     Value:
         *       u32: clock id
         *       u32: rate (in Hz)
         */

        /* setup single tag buffer */
        memset(&msg, 0, sizeof(msg));
        msg.req.clock_id = clock_id;

        /* call mailbox property */
        err = bcm2835_firmware_property(sc->firmware,
            BCM2835_FIRMWARE_TAG_GET_MAX_CLOCK_RATE, &msg, sizeof(msg));
        if (err) {
                device_printf(sc->dev, "can't get max clock rate (id=%u)\n",
                    clock_id);
                return (MSG_ERROR);
        }

        /* result (Hz) */
        rate = (int)msg.resp.rate_hz;
        DPRINTF("clock = %d(Hz)\n", rate);
        return (rate);
}

static int
bcm2835_cpufreq_get_min_clock_rate(struct bcm2835_cpufreq_softc *sc,
    uint32_t clock_id)
{
        union msg_get_clock_rate_body msg;
        int rate;
        int err;

        /*
         * Get min clock rate
         *   Tag: 0x00030007
         *   Request:
         *     Length: 4
         *     Value:
         *       u32: clock id
         *   Response:
         *     Length: 8
         *     Value:
         *       u32: clock id
         *       u32: rate (in Hz)
         */

        /* setup single tag buffer */
        memset(&msg, 0, sizeof(msg));
        msg.req.clock_id = clock_id;

        /* call mailbox property */
        err = bcm2835_firmware_property(sc->firmware,
            BCM2835_FIRMWARE_TAG_GET_MIN_CLOCK_RATE, &msg, sizeof(msg));
        if (err) {
                device_printf(sc->dev, "can't get min clock rate (id=%u)\n",
                    clock_id);
                return (MSG_ERROR);
        }

        /* result (Hz) */
        rate = (int)msg.resp.rate_hz;
        DPRINTF("clock = %d(Hz)\n", rate);
        return (rate);
}

static int
bcm2835_cpufreq_set_clock_rate(struct bcm2835_cpufreq_softc *sc,
    uint32_t clock_id, uint32_t rate_hz)
{
        union msg_set_clock_rate_body msg;
        int rate;
        int err;

        /*
         * Set clock rate
         *   Tag: 0x00038002
         *   Request:
         *     Length: 8
         *     Value:
         *       u32: clock id
         *       u32: rate (in Hz)
         *   Response:
         *     Length: 8
         *     Value:
         *       u32: clock id
         *       u32: rate (in Hz)
         */

        /* setup single tag buffer */
        memset(&msg, 0, sizeof(msg));
        msg.req.clock_id = clock_id;
        msg.req.rate_hz = rate_hz;

        /* call mailbox property */
        err = bcm2835_firmware_property(sc->firmware,
            BCM2835_FIRMWARE_TAG_SET_CLOCK_RATE, &msg, sizeof(msg));
        if (err) {
                device_printf(sc->dev, "can't set clock rate (id=%u)\n",
                    clock_id);
                return (MSG_ERROR);
        }

        /* workaround for core clock */
        if (clock_id == BCM2835_FIRMWARE_CLOCK_ID_CORE) {
                /* for safety (may change voltage without changing clock) */
                DELAY(TRANSITION_LATENCY);

                /*
                 * XXX: the core clock is unable to change at once,
                 * to change certainly, write it twice now.
                 */

                /* setup single tag buffer */
                memset(&msg, 0, sizeof(msg));
                msg.req.clock_id = clock_id;
                msg.req.rate_hz = rate_hz;

                /* call mailbox property */
                err = bcm2835_firmware_property(sc->firmware,
                    BCM2835_FIRMWARE_TAG_SET_CLOCK_RATE, &msg, sizeof(msg));
                if (err) {
                        device_printf(sc->dev,
                            "can't set clock rate (id=%u)\n", clock_id);
                        return (MSG_ERROR);
                }
        }

        /* result (Hz) */
        rate = (int)msg.resp.rate_hz;
        DPRINTF("clock = %d(Hz)\n", rate);
        return (rate);
}

static int
bcm2835_cpufreq_get_turbo(struct bcm2835_cpufreq_softc *sc)
{
        union msg_get_turbo_body msg;
        int level;
        int err;

        /*
         * Get turbo
         *   Tag: 0x00030009
         *   Request:
         *     Length: 4
         *     Value:
         *       u32: id
         *   Response:
         *     Length: 8
         *     Value:
         *       u32: id
         *       u32: level
         */

        /* setup single tag buffer */
        memset(&msg, 0, sizeof(msg));
        msg.req.id = 0;

        /* call mailbox property */
        err = bcm2835_firmware_property(sc->firmware,
            BCM2835_FIRMWARE_TAG_GET_TURBO, &msg, sizeof(msg));
        if (err) {
                device_printf(sc->dev, "can't get turbo\n");
                return (MSG_ERROR);
        }

        /* result 0=non-turbo, 1=turbo */
        level = (int)msg.resp.level;
        DPRINTF("level = %d\n", level);
        return (level);
}

static int
bcm2835_cpufreq_set_turbo(struct bcm2835_cpufreq_softc *sc, uint32_t level)
{
        union msg_set_turbo_body msg;
        int value;
        int err;

        /*
         * Set turbo
         *   Tag: 0x00038009
         *   Request:
         *     Length: 8
         *     Value:
         *       u32: id
         *       u32: level
         *   Response:
         *     Length: 8
         *     Value:
         *       u32: id
         *       u32: level
         */

        /* replace unknown value to OFF */
        if (level != BCM2835_FIRMWARE_TURBO_ON &&
            level != BCM2835_FIRMWARE_TURBO_OFF)
                level = BCM2835_FIRMWARE_TURBO_OFF;

        /* setup single tag buffer */
        memset(&msg, 0, sizeof(msg));
        msg.req.id = 0;
        msg.req.level = level;

        /* call mailbox property */
        err = bcm2835_firmware_property(sc->firmware,
            BCM2835_FIRMWARE_TAG_SET_TURBO, &msg, sizeof(msg));
        if (err) {
                device_printf(sc->dev, "can't set turbo\n");
                return (MSG_ERROR);
        }

        /* result 0=non-turbo, 1=turbo */
        value = (int)msg.resp.level;
        DPRINTF("level = %d\n", value);
        return (value);
}

static int
bcm2835_cpufreq_get_voltage(struct bcm2835_cpufreq_softc *sc,
    uint32_t voltage_id)
{
        union msg_get_voltage_body msg;
        int value;
        int err;

        /*
         * Get voltage
         *   Tag: 0x00030003
         *   Request:
         *     Length: 4
         *     Value:
         *       u32: voltage id
         *   Response:
         *     Length: 8
         *     Value:
         *       u32: voltage id
         *       u32: value (offset from 1.2V in units of 0.025V)
         */

        /* setup single tag buffer */
        memset(&msg, 0, sizeof(msg));
        msg.req.voltage_id = voltage_id;

        /* call mailbox property */
        err = bcm2835_firmware_property(sc->firmware,
            BCM2835_FIRMWARE_TAG_GET_VOLTAGE, &msg, sizeof(msg));
        if (err) {
                device_printf(sc->dev, "can't get voltage\n");
                return (MSG_ERROR);
        }

        /* result (offset from 1.2V) */
        value = (int)msg.resp.value;
        DPRINTF("value = %d\n", value);
        return (value);
}

static int
bcm2835_cpufreq_get_max_voltage(struct bcm2835_cpufreq_softc *sc,
    uint32_t voltage_id)
{
        union msg_get_voltage_body msg;
        int value;
        int err;

        /*
         * Get voltage
         *   Tag: 0x00030005
         *   Request:
         *     Length: 4
         *     Value:
         *       u32: voltage id
         *   Response:
         *     Length: 8
         *     Value:
         *       u32: voltage id
         *       u32: value (offset from 1.2V in units of 0.025V)
         */

        /* setup single tag buffer */
        memset(&msg, 0, sizeof(msg));
        msg.req.voltage_id = voltage_id;

        /* call mailbox property */
        err = bcm2835_firmware_property(sc->firmware,
            BCM2835_FIRMWARE_TAG_GET_MAX_VOLTAGE, &msg, sizeof(msg));
        if (err) {
                device_printf(sc->dev, "can't get max voltage\n");
                return (MSG_ERROR);
        }

        /* result (offset from 1.2V) */
        value = (int)msg.resp.value;
        DPRINTF("value = %d\n", value);
        return (value);
}
static int
bcm2835_cpufreq_get_min_voltage(struct bcm2835_cpufreq_softc *sc,
    uint32_t voltage_id)
{
        union msg_get_voltage_body msg;
        int value;
        int err;

        /*
         * Get voltage
         *   Tag: 0x00030008
         *   Request:
         *     Length: 4
         *     Value:
         *       u32: voltage id
         *   Response:
         *     Length: 8
         *     Value:
         *       u32: voltage id
         *       u32: value (offset from 1.2V in units of 0.025V)
         */

        /* setup single tag buffer */
        memset(&msg, 0, sizeof(msg));
        msg.req.voltage_id = voltage_id;

        /* call mailbox property */
        err = bcm2835_firmware_property(sc->firmware,
            BCM2835_FIRMWARE_TAG_GET_MIN_VOLTAGE, &msg, sizeof(msg));
        if (err) {
                device_printf(sc->dev, "can't get min voltage\n");
                return (MSG_ERROR);
        }

        /* result (offset from 1.2V) */
        value = (int)msg.resp.value;
        DPRINTF("value = %d\n", value);
        return (value);
}

static int
bcm2835_cpufreq_set_voltage(struct bcm2835_cpufreq_softc *sc,
    uint32_t voltage_id, int32_t value)
{
        union msg_set_voltage_body msg;
        int err;

        /*
         * Set voltage
         *   Tag: 0x00038003
         *   Request:
         *     Length: 4
         *     Value:
         *       u32: voltage id
         *       u32: value (offset from 1.2V in units of 0.025V)
         *   Response:
         *     Length: 8
         *     Value:
         *       u32: voltage id
         *       u32: value (offset from 1.2V in units of 0.025V)
         */

        /*
         * over_voltage:
         * 0 (1.2 V). Values above 6 are only allowed when force_turbo or
         * current_limit_override are specified (which set the warranty bit).
         */
        if (value > MAX_OVER_VOLTAGE || value < MIN_OVER_VOLTAGE) {
                /* currently not supported */
                device_printf(sc->dev, "not supported voltage: %d\n", value);
                return (MSG_ERROR);
        }

        /* setup single tag buffer */
        memset(&msg, 0, sizeof(msg));
        msg.req.voltage_id = voltage_id;
        msg.req.value = (uint32_t)value;

        /* call mailbox property */
        err = bcm2835_firmware_property(sc->firmware,
            BCM2835_FIRMWARE_TAG_SET_VOLTAGE, &msg, sizeof(msg));
        if (err) {
                device_printf(sc->dev, "can't set voltage\n");
                return (MSG_ERROR);
        }

        /* result (offset from 1.2V) */
        value = (int)msg.resp.value;
        DPRINTF("value = %d\n", value);
        return (value);
}

static int
bcm2835_cpufreq_get_temperature(struct bcm2835_cpufreq_softc *sc)
{
        union msg_get_temperature_body msg;
        int value;
        int err;

        /*
         * Get temperature
         *   Tag: 0x00030006
         *   Request:
         *     Length: 4
         *     Value:
         *       u32: temperature id
         *   Response:
         *     Length: 8
         *     Value:
         *       u32: temperature id
         *       u32: value
         */

        /* setup single tag buffer */
        memset(&msg, 0, sizeof(msg));
        msg.req.temperature_id = 0;

        /* call mailbox property */
        err = bcm2835_firmware_property(sc->firmware,
            BCM2835_FIRMWARE_TAG_GET_TEMPERATURE, &msg, sizeof(msg));
        if (err) {
                device_printf(sc->dev, "can't get temperature\n");
                return (MSG_ERROR);
        }

        /* result (temperature of degree C) */
        value = (int)msg.resp.value;
        DPRINTF("value = %d\n", value);
        return (value);
}

static int
sysctl_bcm2835_cpufreq_arm_freq(SYSCTL_HANDLER_ARGS)
{
        struct bcm2835_cpufreq_softc *sc = arg1;
        int val;
        int err;

        /* get realtime value */
        VC_LOCK(sc);
        val = bcm2835_cpufreq_get_clock_rate(sc, BCM2835_FIRMWARE_CLOCK_ID_ARM);
        VC_UNLOCK(sc);
        if (val == MSG_ERROR)
                return (EIO);

        err = sysctl_handle_int(oidp, &val, 0, req);
        if (err || !req->newptr) /* error || read request */
                return (err);

        /* write request */
        VC_LOCK(sc);
        err = bcm2835_cpufreq_set_clock_rate(sc, BCM2835_FIRMWARE_CLOCK_ID_ARM,
            val);
        VC_UNLOCK(sc);
        if (err == MSG_ERROR) {
                device_printf(sc->dev, "set clock arm_freq error\n");
                return (EIO);
        }
        DELAY(TRANSITION_LATENCY);

        return (0);
}

static int
sysctl_bcm2835_cpufreq_core_freq(SYSCTL_HANDLER_ARGS)
{
        struct bcm2835_cpufreq_softc *sc = arg1;
        int val;
        int err;

        /* get realtime value */
        VC_LOCK(sc);
        val = bcm2835_cpufreq_get_clock_rate(sc,
            BCM2835_FIRMWARE_CLOCK_ID_CORE);
        VC_UNLOCK(sc);
        if (val == MSG_ERROR)
                return (EIO);

        err = sysctl_handle_int(oidp, &val, 0, req);
        if (err || !req->newptr) /* error || read request */
                return (err);

        /* write request */
        VC_LOCK(sc);
        err = bcm2835_cpufreq_set_clock_rate(sc, BCM2835_FIRMWARE_CLOCK_ID_CORE,
            val);
        if (err == MSG_ERROR) {
                VC_UNLOCK(sc);
                device_printf(sc->dev, "set clock core_freq error\n");
                return (EIO);
        }
        VC_UNLOCK(sc);
        DELAY(TRANSITION_LATENCY);

        return (0);
}

static int
sysctl_bcm2835_cpufreq_sdram_freq(SYSCTL_HANDLER_ARGS)
{
        struct bcm2835_cpufreq_softc *sc = arg1;
        int val;
        int err;

        /* get realtime value */
        VC_LOCK(sc);
        val = bcm2835_cpufreq_get_clock_rate(sc,
            BCM2835_FIRMWARE_CLOCK_ID_SDRAM);
        VC_UNLOCK(sc);
        if (val == MSG_ERROR)
                return (EIO);

        err = sysctl_handle_int(oidp, &val, 0, req);
        if (err || !req->newptr) /* error || read request */
                return (err);

        /* write request */
        VC_LOCK(sc);
        err = bcm2835_cpufreq_set_clock_rate(sc,
            BCM2835_FIRMWARE_CLOCK_ID_SDRAM, val);
        VC_UNLOCK(sc);
        if (err == MSG_ERROR) {
                device_printf(sc->dev, "set clock sdram_freq error\n");
                return (EIO);
        }
        DELAY(TRANSITION_LATENCY);

        return (0);
}

static int
sysctl_bcm2835_cpufreq_turbo(SYSCTL_HANDLER_ARGS)
{
        struct bcm2835_cpufreq_softc *sc = arg1;
        int val;
        int err;

        /* get realtime value */
        VC_LOCK(sc);
        val = bcm2835_cpufreq_get_turbo(sc);
        VC_UNLOCK(sc);
        if (val == MSG_ERROR)
                return (EIO);

        err = sysctl_handle_int(oidp, &val, 0, req);
        if (err || !req->newptr) /* error || read request */
                return (err);

        /* write request */
        if (val > 0)
                sc->turbo_mode = BCM2835_FIRMWARE_TURBO_ON;
        else
                sc->turbo_mode = BCM2835_FIRMWARE_TURBO_OFF;

        VC_LOCK(sc);
        err = bcm2835_cpufreq_set_turbo(sc, sc->turbo_mode);
        VC_UNLOCK(sc);
        if (err == MSG_ERROR) {
                device_printf(sc->dev, "set turbo error\n");
                return (EIO);
        }
        DELAY(TRANSITION_LATENCY);

        return (0);
}

static int
sysctl_bcm2835_cpufreq_voltage_core(SYSCTL_HANDLER_ARGS)
{
        struct bcm2835_cpufreq_softc *sc = arg1;
        int val;
        int err;

        /* get realtime value */
        VC_LOCK(sc);
        val = bcm2835_cpufreq_get_voltage(sc, BCM2835_FIRMWARE_VOLTAGE_ID_CORE);
        VC_UNLOCK(sc);
        if (val == MSG_ERROR)
                return (EIO);

        err = sysctl_handle_int(oidp, &val, 0, req);
        if (err || !req->newptr) /* error || read request */
                return (err);

        /* write request */
        if (val > MAX_OVER_VOLTAGE || val < MIN_OVER_VOLTAGE)
                return (EINVAL);
        sc->voltage_core = val;

        VC_LOCK(sc);
        err = bcm2835_cpufreq_set_voltage(sc, BCM2835_FIRMWARE_VOLTAGE_ID_CORE,
            sc->voltage_core);
        VC_UNLOCK(sc);
        if (err == MSG_ERROR) {
                device_printf(sc->dev, "set voltage core error\n");
                return (EIO);
        }
        DELAY(TRANSITION_LATENCY);

        return (0);
}

static int
sysctl_bcm2835_cpufreq_voltage_sdram_c(SYSCTL_HANDLER_ARGS)
{
        struct bcm2835_cpufreq_softc *sc = arg1;
        int val;
        int err;

        /* get realtime value */
        VC_LOCK(sc);
        val = bcm2835_cpufreq_get_voltage(sc,
            BCM2835_FIRMWARE_VOLTAGE_ID_SDRAM_C);
        VC_UNLOCK(sc);
        if (val == MSG_ERROR)
                return (EIO);

        err = sysctl_handle_int(oidp, &val, 0, req);
        if (err || !req->newptr) /* error || read request */
                return (err);

        /* write request */
        if (val > MAX_OVER_VOLTAGE || val < MIN_OVER_VOLTAGE)
                return (EINVAL);
        sc->voltage_sdram_c = val;

        VC_LOCK(sc);
        err = bcm2835_cpufreq_set_voltage(sc,
            BCM2835_FIRMWARE_VOLTAGE_ID_SDRAM_C,
           sc->voltage_sdram_c);
        VC_UNLOCK(sc);
        if (err == MSG_ERROR) {
                device_printf(sc->dev, "set voltage sdram_c error\n");
                return (EIO);
        }
        DELAY(TRANSITION_LATENCY);

        return (0);
}

static int
sysctl_bcm2835_cpufreq_voltage_sdram_i(SYSCTL_HANDLER_ARGS)
{
        struct bcm2835_cpufreq_softc *sc = arg1;
        int val;
        int err;

        /* get realtime value */
        VC_LOCK(sc);
        val = bcm2835_cpufreq_get_voltage(sc,
            BCM2835_FIRMWARE_VOLTAGE_ID_SDRAM_I);
        VC_UNLOCK(sc);
        if (val == MSG_ERROR)
                return (EIO);

        err = sysctl_handle_int(oidp, &val, 0, req);
        if (err || !req->newptr) /* error || read request */
                return (err);

        /* write request */
        if (val > MAX_OVER_VOLTAGE || val < MIN_OVER_VOLTAGE)
                return (EINVAL);
        sc->voltage_sdram_i = val;

        VC_LOCK(sc);
        err = bcm2835_cpufreq_set_voltage(sc,
            BCM2835_FIRMWARE_VOLTAGE_ID_SDRAM_I, sc->voltage_sdram_i);
        VC_UNLOCK(sc);
        if (err == MSG_ERROR) {
                device_printf(sc->dev, "set voltage sdram_i error\n");
                return (EIO);
        }
        DELAY(TRANSITION_LATENCY);

        return (0);
}

static int
sysctl_bcm2835_cpufreq_voltage_sdram_p(SYSCTL_HANDLER_ARGS)
{
        struct bcm2835_cpufreq_softc *sc = arg1;
        int val;
        int err;

        /* get realtime value */
        VC_LOCK(sc);
        val = bcm2835_cpufreq_get_voltage(sc,
            BCM2835_FIRMWARE_VOLTAGE_ID_SDRAM_P);
        VC_UNLOCK(sc);
        if (val == MSG_ERROR)
                return (EIO);

        err = sysctl_handle_int(oidp, &val, 0, req);
        if (err || !req->newptr) /* error || read request */
                return (err);

        /* write request */
        if (val > MAX_OVER_VOLTAGE || val < MIN_OVER_VOLTAGE)
                return (EINVAL);
        sc->voltage_sdram_p = val;

        VC_LOCK(sc);
        err = bcm2835_cpufreq_set_voltage(sc,
            BCM2835_FIRMWARE_VOLTAGE_ID_SDRAM_P, sc->voltage_sdram_p);
        VC_UNLOCK(sc);
        if (err == MSG_ERROR) {
                device_printf(sc->dev, "set voltage sdram_p error\n");
                return (EIO);
        }
        DELAY(TRANSITION_LATENCY);

        return (0);
}

static int
sysctl_bcm2835_cpufreq_voltage_sdram(SYSCTL_HANDLER_ARGS)
{
        struct bcm2835_cpufreq_softc *sc = arg1;
        int val;
        int err;

        /* multiple write only */
        if (!req->newptr)
                return (EINVAL);
        val = 0;
        err = sysctl_handle_int(oidp, &val, 0, req);
        if (err)
                return (err);

        /* write request */
        if (val > MAX_OVER_VOLTAGE || val < MIN_OVER_VOLTAGE)
                return (EINVAL);
        sc->voltage_sdram = val;

        VC_LOCK(sc);
        err = bcm2835_cpufreq_set_voltage(sc,
            BCM2835_FIRMWARE_VOLTAGE_ID_SDRAM_C, val);
        if (err == MSG_ERROR) {
                VC_UNLOCK(sc);
                device_printf(sc->dev, "set voltage sdram_c error\n");
                return (EIO);
        }
        err = bcm2835_cpufreq_set_voltage(sc,
            BCM2835_FIRMWARE_VOLTAGE_ID_SDRAM_I, val);
        if (err == MSG_ERROR) {
                VC_UNLOCK(sc);
                device_printf(sc->dev, "set voltage sdram_i error\n");
                return (EIO);
        }
        err = bcm2835_cpufreq_set_voltage(sc,
            BCM2835_FIRMWARE_VOLTAGE_ID_SDRAM_P, val);
        if (err == MSG_ERROR) {
                VC_UNLOCK(sc);
                device_printf(sc->dev, "set voltage sdram_p error\n");
                return (EIO);
        }
        VC_UNLOCK(sc);
        DELAY(TRANSITION_LATENCY);

        return (0);
}

static int
sysctl_bcm2835_cpufreq_temperature(SYSCTL_HANDLER_ARGS)
{
        struct bcm2835_cpufreq_softc *sc = arg1;
        int val;
        int err;

        /* get realtime value */
        VC_LOCK(sc);
        val = bcm2835_cpufreq_get_temperature(sc);
        VC_UNLOCK(sc);
        if (val == MSG_ERROR)
                return (EIO);

        err = sysctl_handle_int(oidp, &val, 0, req);
        if (err || !req->newptr) /* error || read request */
                return (err);

        /* write request */
        return (EINVAL);
}

static int
sysctl_bcm2835_devcpu_temperature(SYSCTL_HANDLER_ARGS)
{
        struct bcm2835_cpufreq_softc *sc = arg1;
        int val;
        int err;

        /* get realtime value */
        VC_LOCK(sc);
        val = bcm2835_cpufreq_get_temperature(sc);
        VC_UNLOCK(sc);
        if (val == MSG_ERROR)
                return (EIO);

        /* 1/1000 celsius (raw) to 1/10 kelvin */
        val = val / 100 + TZ_ZEROC;

        err = sysctl_handle_int(oidp, &val, 0, req);
        if (err || !req->newptr) /* error || read request */
                return (err);

        /* write request */
        return (EINVAL);
}

static void
bcm2835_cpufreq_init(void *arg)
{
        struct bcm2835_cpufreq_softc *sc = arg;
        struct sysctl_ctx_list *ctx;
        device_t cpu;
        int arm_freq, core_freq, sdram_freq;
        int arm_max_freq, arm_min_freq, core_max_freq, core_min_freq;
        int sdram_max_freq, sdram_min_freq;
        int voltage_core, voltage_sdram_c, voltage_sdram_i, voltage_sdram_p;
        int max_voltage_core, min_voltage_core;
        int max_voltage_sdram_c, min_voltage_sdram_c;
        int max_voltage_sdram_i, min_voltage_sdram_i;
        int max_voltage_sdram_p, min_voltage_sdram_p;
        int turbo, temperature;

        VC_LOCK(sc);

        /* current clock */
        arm_freq = bcm2835_cpufreq_get_clock_rate(sc,
            BCM2835_FIRMWARE_CLOCK_ID_ARM);
        core_freq = bcm2835_cpufreq_get_clock_rate(sc,
            BCM2835_FIRMWARE_CLOCK_ID_CORE);
        sdram_freq = bcm2835_cpufreq_get_clock_rate(sc,
            BCM2835_FIRMWARE_CLOCK_ID_SDRAM);

        /* max/min clock */
        arm_max_freq = bcm2835_cpufreq_get_max_clock_rate(sc,
            BCM2835_FIRMWARE_CLOCK_ID_ARM);
        arm_min_freq = bcm2835_cpufreq_get_min_clock_rate(sc,
            BCM2835_FIRMWARE_CLOCK_ID_ARM);
        core_max_freq = bcm2835_cpufreq_get_max_clock_rate(sc,
            BCM2835_FIRMWARE_CLOCK_ID_CORE);
        core_min_freq = bcm2835_cpufreq_get_min_clock_rate(sc,
            BCM2835_FIRMWARE_CLOCK_ID_CORE);
        sdram_max_freq = bcm2835_cpufreq_get_max_clock_rate(sc,
            BCM2835_FIRMWARE_CLOCK_ID_SDRAM);
        sdram_min_freq = bcm2835_cpufreq_get_min_clock_rate(sc,
            BCM2835_FIRMWARE_CLOCK_ID_SDRAM);

        /* turbo mode */
        turbo = bcm2835_cpufreq_get_turbo(sc);
        if (turbo > 0)
                sc->turbo_mode = BCM2835_FIRMWARE_TURBO_ON;
        else
                sc->turbo_mode = BCM2835_FIRMWARE_TURBO_OFF;

        /* voltage */
        voltage_core = bcm2835_cpufreq_get_voltage(sc,
            BCM2835_FIRMWARE_VOLTAGE_ID_CORE);
        voltage_sdram_c = bcm2835_cpufreq_get_voltage(sc,
            BCM2835_FIRMWARE_VOLTAGE_ID_SDRAM_C);
        voltage_sdram_i = bcm2835_cpufreq_get_voltage(sc,
            BCM2835_FIRMWARE_VOLTAGE_ID_SDRAM_I);
        voltage_sdram_p = bcm2835_cpufreq_get_voltage(sc,
            BCM2835_FIRMWARE_VOLTAGE_ID_SDRAM_P);

        /* current values (offset from 1.2V) */
        sc->voltage_core = voltage_core;
        sc->voltage_sdram = voltage_sdram_c;
        sc->voltage_sdram_c = voltage_sdram_c;
        sc->voltage_sdram_i = voltage_sdram_i;
        sc->voltage_sdram_p = voltage_sdram_p;

        /* max/min voltage */
        max_voltage_core = bcm2835_cpufreq_get_max_voltage(sc,
            BCM2835_FIRMWARE_VOLTAGE_ID_CORE);
        min_voltage_core = bcm2835_cpufreq_get_min_voltage(sc,
            BCM2835_FIRMWARE_VOLTAGE_ID_CORE);
        max_voltage_sdram_c = bcm2835_cpufreq_get_max_voltage(sc,
            BCM2835_FIRMWARE_VOLTAGE_ID_SDRAM_C);
        max_voltage_sdram_i = bcm2835_cpufreq_get_max_voltage(sc,
            BCM2835_FIRMWARE_VOLTAGE_ID_SDRAM_I);
        max_voltage_sdram_p = bcm2835_cpufreq_get_max_voltage(sc,
            BCM2835_FIRMWARE_VOLTAGE_ID_SDRAM_P);
        min_voltage_sdram_c = bcm2835_cpufreq_get_min_voltage(sc,
            BCM2835_FIRMWARE_VOLTAGE_ID_SDRAM_C);
        min_voltage_sdram_i = bcm2835_cpufreq_get_min_voltage(sc,
            BCM2835_FIRMWARE_VOLTAGE_ID_SDRAM_I);
        min_voltage_sdram_p = bcm2835_cpufreq_get_min_voltage(sc,
            BCM2835_FIRMWARE_VOLTAGE_ID_SDRAM_P);

        /* temperature */
        temperature = bcm2835_cpufreq_get_temperature(sc);

        /* show result */
        if (cpufreq_verbose || bootverbose) {
                device_printf(sc->dev, "Boot settings:\n");
                device_printf(sc->dev,
                    "current ARM %dMHz, Core %dMHz, SDRAM %dMHz, Turbo %s\n",
                    HZ2MHZ(arm_freq), HZ2MHZ(core_freq), HZ2MHZ(sdram_freq),
                    (sc->turbo_mode == BCM2835_FIRMWARE_TURBO_ON) ? "ON":"OFF");

                device_printf(sc->dev,
                    "max/min ARM %d/%dMHz, Core %d/%dMHz, SDRAM %d/%dMHz\n",
                    HZ2MHZ(arm_max_freq), HZ2MHZ(arm_min_freq),
                    HZ2MHZ(core_max_freq), HZ2MHZ(core_min_freq),
                    HZ2MHZ(sdram_max_freq), HZ2MHZ(sdram_min_freq));

                device_printf(sc->dev,
                    "current Core %dmV, SDRAM_C %dmV, SDRAM_I %dmV, "
                    "SDRAM_P %dmV\n",
                    OFFSET2MVOLT(voltage_core), OFFSET2MVOLT(voltage_sdram_c),
                    OFFSET2MVOLT(voltage_sdram_i), 
                    OFFSET2MVOLT(voltage_sdram_p));

                device_printf(sc->dev,
                    "max/min Core %d/%dmV, SDRAM_C %d/%dmV, SDRAM_I %d/%dmV, "
                    "SDRAM_P %d/%dmV\n",
                    OFFSET2MVOLT(max_voltage_core),
                    OFFSET2MVOLT(min_voltage_core),
                    OFFSET2MVOLT(max_voltage_sdram_c),
                    OFFSET2MVOLT(min_voltage_sdram_c),
                    OFFSET2MVOLT(max_voltage_sdram_i),
                    OFFSET2MVOLT(min_voltage_sdram_i),
                    OFFSET2MVOLT(max_voltage_sdram_p),
                    OFFSET2MVOLT(min_voltage_sdram_p));

                device_printf(sc->dev,
                    "Temperature %d.%dC\n", (temperature / 1000),
                    (temperature % 1000) / 100);
        } else { /* !cpufreq_verbose && !bootverbose */
                device_printf(sc->dev,
                    "ARM %dMHz, Core %dMHz, SDRAM %dMHz, Turbo %s\n",
                    HZ2MHZ(arm_freq), HZ2MHZ(core_freq), HZ2MHZ(sdram_freq),
                    (sc->turbo_mode == BCM2835_FIRMWARE_TURBO_ON) ? "ON":"OFF");
        }

        /* keep in softc (MHz/mV) */
        sc->arm_max_freq = HZ2MHZ(arm_max_freq);
        sc->arm_min_freq = HZ2MHZ(arm_min_freq);
        sc->core_max_freq = HZ2MHZ(core_max_freq);
        sc->core_min_freq = HZ2MHZ(core_min_freq);
        sc->sdram_max_freq = HZ2MHZ(sdram_max_freq);
        sc->sdram_min_freq = HZ2MHZ(sdram_min_freq);
        sc->max_voltage_core = OFFSET2MVOLT(max_voltage_core);
        sc->min_voltage_core = OFFSET2MVOLT(min_voltage_core);

        /* if turbo is on, set to max values */
        if (sc->turbo_mode == BCM2835_FIRMWARE_TURBO_ON) {
                bcm2835_cpufreq_set_clock_rate(sc,
                    BCM2835_FIRMWARE_CLOCK_ID_ARM, arm_max_freq);
                DELAY(TRANSITION_LATENCY);
                bcm2835_cpufreq_set_clock_rate(sc,
                    BCM2835_FIRMWARE_CLOCK_ID_CORE, core_max_freq);
                DELAY(TRANSITION_LATENCY);
                bcm2835_cpufreq_set_clock_rate(sc,
                    BCM2835_FIRMWARE_CLOCK_ID_SDRAM, sdram_max_freq);
                DELAY(TRANSITION_LATENCY);
        } else {
                bcm2835_cpufreq_set_clock_rate(sc,
                    BCM2835_FIRMWARE_CLOCK_ID_ARM, arm_min_freq);
                DELAY(TRANSITION_LATENCY);
                bcm2835_cpufreq_set_clock_rate(sc,
                    BCM2835_FIRMWARE_CLOCK_ID_CORE, core_min_freq);
                DELAY(TRANSITION_LATENCY);
                bcm2835_cpufreq_set_clock_rate(sc,
                    BCM2835_FIRMWARE_CLOCK_ID_SDRAM, sdram_min_freq);
                DELAY(TRANSITION_LATENCY);
        }

        VC_UNLOCK(sc);

        /* add human readable temperature to dev.cpu node */
        cpu = device_get_parent(sc->dev);
        if (cpu != NULL) {
                ctx = device_get_sysctl_ctx(cpu);
                SYSCTL_ADD_PROC(ctx,
                    SYSCTL_CHILDREN(device_get_sysctl_tree(cpu)), OID_AUTO,
                    "temperature",
                    CTLTYPE_INT | CTLFLAG_RD | CTLFLAG_NEEDGIANT, sc, 0,
                    sysctl_bcm2835_devcpu_temperature, "IK",
                    "Current SoC temperature");
        }

        /* release this hook (continue boot) */
        config_intrhook_disestablish(&sc->init_hook);
}

static void
bcm2835_cpufreq_identify(driver_t *driver, device_t parent)
{
        const struct ofw_compat_data *compat;
        phandle_t root;

        root = OF_finddevice("/");
        for (compat = compat_data; compat->ocd_str != NULL; compat++)
                if (ofw_bus_node_is_compatible(root, compat->ocd_str))
                        break;

        if (compat->ocd_data == 0)
                return;

        DPRINTF("driver=%p, parent=%p\n", driver, parent);
        if (device_find_child(parent, "bcm2835_cpufreq", DEVICE_UNIT_ANY) != NULL)
                return;
        if (BUS_ADD_CHILD(parent, 0, "bcm2835_cpufreq", DEVICE_UNIT_ANY) == NULL)
                device_printf(parent, "add child failed\n");
}

static int
bcm2835_cpufreq_probe(device_t dev)
{

        if (device_get_unit(dev) != 0)
                return (ENXIO);
        device_set_desc(dev, "CPU Frequency Control");

        return (0);
}

static int
bcm2835_cpufreq_attach(device_t dev)
{
        struct bcm2835_cpufreq_softc *sc;
        struct sysctl_oid *oid;

        /* set self dev */
        sc = device_get_softc(dev);
        sc->dev = dev;
        sc->firmware = devclass_get_device(
            devclass_find("bcm2835_firmware"), 0);
        if (sc->firmware == NULL) {
                device_printf(dev, "Unable to find firmware device\n");
                return (ENXIO);
        }

        /* initial values */
        sc->arm_max_freq = -1;
        sc->arm_min_freq = -1;
        sc->core_max_freq = -1;
        sc->core_min_freq = -1;
        sc->sdram_max_freq = -1;
        sc->sdram_min_freq = -1;
        sc->max_voltage_core = 0;
        sc->min_voltage_core = 0;

        /* setup sysctl at first device */
        if (device_get_unit(dev) == 0) {
                sysctl_ctx_init(&bcm2835_sysctl_ctx);
                /* create node for hw.cpufreq */
                oid = SYSCTL_ADD_NODE(&bcm2835_sysctl_ctx,
                    SYSCTL_STATIC_CHILDREN(_hw), OID_AUTO, "cpufreq",
                    CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, "");

                /* Frequency (Hz) */
                SYSCTL_ADD_PROC(&bcm2835_sysctl_ctx, SYSCTL_CHILDREN(oid),
                    OID_AUTO, "arm_freq",
                    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, sc, 0,
                    sysctl_bcm2835_cpufreq_arm_freq, "IU",
                    "ARM frequency (Hz)");
                SYSCTL_ADD_PROC(&bcm2835_sysctl_ctx, SYSCTL_CHILDREN(oid),
                    OID_AUTO, "core_freq",
                    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, sc, 0,
                    sysctl_bcm2835_cpufreq_core_freq, "IU",
                    "Core frequency (Hz)");
                SYSCTL_ADD_PROC(&bcm2835_sysctl_ctx, SYSCTL_CHILDREN(oid),
                    OID_AUTO, "sdram_freq",
                    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, sc, 0,
                    sysctl_bcm2835_cpufreq_sdram_freq, "IU",
                    "SDRAM frequency (Hz)");

                /* Turbo state */
                SYSCTL_ADD_PROC(&bcm2835_sysctl_ctx, SYSCTL_CHILDREN(oid),
                    OID_AUTO, "turbo",
                    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, sc, 0,
                    sysctl_bcm2835_cpufreq_turbo, "IU",
                    "Disables dynamic clocking");

                /* Voltage (offset from 1.2V in units of 0.025V) */
                SYSCTL_ADD_PROC(&bcm2835_sysctl_ctx, SYSCTL_CHILDREN(oid),
                    OID_AUTO, "voltage_core",
                    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, sc, 0,
                    sysctl_bcm2835_cpufreq_voltage_core, "I",
                    "ARM/GPU core voltage"
                    "(offset from 1.2V in units of 0.025V)");
                SYSCTL_ADD_PROC(&bcm2835_sysctl_ctx, SYSCTL_CHILDREN(oid),
                    OID_AUTO, "voltage_sdram",
                    CTLTYPE_INT | CTLFLAG_WR | CTLFLAG_NEEDGIANT, sc,
                    0, sysctl_bcm2835_cpufreq_voltage_sdram, "I",
                    "SDRAM voltage (offset from 1.2V in units of 0.025V)");

                /* Voltage individual SDRAM */
                SYSCTL_ADD_PROC(&bcm2835_sysctl_ctx, SYSCTL_CHILDREN(oid),
                    OID_AUTO, "voltage_sdram_c",
                    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, sc,
                    0, sysctl_bcm2835_cpufreq_voltage_sdram_c, "I",
                    "SDRAM controller voltage"
                    "(offset from 1.2V in units of 0.025V)");
                SYSCTL_ADD_PROC(&bcm2835_sysctl_ctx, SYSCTL_CHILDREN(oid),
                    OID_AUTO, "voltage_sdram_i",
                    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, sc,
                    0, sysctl_bcm2835_cpufreq_voltage_sdram_i, "I",
                    "SDRAM I/O voltage (offset from 1.2V in units of 0.025V)");
                SYSCTL_ADD_PROC(&bcm2835_sysctl_ctx, SYSCTL_CHILDREN(oid),
                    OID_AUTO, "voltage_sdram_p",
                    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, sc,
                    0, sysctl_bcm2835_cpufreq_voltage_sdram_p, "I",
                    "SDRAM phy voltage (offset from 1.2V in units of 0.025V)");

                /* Temperature */
                SYSCTL_ADD_PROC(&bcm2835_sysctl_ctx, SYSCTL_CHILDREN(oid),
                    OID_AUTO, "temperature",
                    CTLTYPE_INT | CTLFLAG_RD | CTLFLAG_NEEDGIANT, sc, 0,
                    sysctl_bcm2835_cpufreq_temperature, "I",
                    "SoC temperature (thousandths of a degree C)");
        }

        /* ARM->VC lock */
        sema_init(&vc_sema, 1, "vcsema");

        /* register callback for using mbox when interrupts are enabled */
        sc->init_hook.ich_func = bcm2835_cpufreq_init;
        sc->init_hook.ich_arg = sc;

        if (config_intrhook_establish(&sc->init_hook) != 0) {
                device_printf(dev, "config_intrhook_establish failed\n");
                return (ENOMEM);
        }

        /* this device is controlled by cpufreq(4) */
        cpufreq_register(dev);

        return (0);
}

static int
bcm2835_cpufreq_detach(device_t dev)
{

        sema_destroy(&vc_sema);

        return (cpufreq_unregister(dev));
}

static int
bcm2835_cpufreq_set(device_t dev, const struct cf_setting *cf)
{
        struct bcm2835_cpufreq_softc *sc;
        uint32_t rate_hz, rem;
        int resp_freq, arm_freq, min_freq, core_freq;
#ifdef DEBUG
        int cur_freq;
#endif

        if (cf == NULL || cf->freq < 0)
                return (EINVAL);

        sc = device_get_softc(dev);

        /* setting clock (Hz) */
        rate_hz = (uint32_t)MHZ2HZ(cf->freq);
        rem = rate_hz % HZSTEP;
        rate_hz -= rem;
        if (rate_hz == 0)
                return (EINVAL);

        /* adjust min freq */
        min_freq = sc->arm_min_freq;
        if (sc->turbo_mode != BCM2835_FIRMWARE_TURBO_ON)
                if (min_freq > cpufreq_lowest_freq)
                        min_freq = cpufreq_lowest_freq;

        if (rate_hz < MHZ2HZ(min_freq) || rate_hz > MHZ2HZ(sc->arm_max_freq))
                return (EINVAL);

        /* set new value and verify it */
        VC_LOCK(sc);
#ifdef DEBUG
        cur_freq = bcm2835_cpufreq_get_clock_rate(sc,
            BCM2835_FIRMWARE_CLOCK_ID_ARM);
#endif
        resp_freq = bcm2835_cpufreq_set_clock_rate(sc,
            BCM2835_FIRMWARE_CLOCK_ID_ARM, rate_hz);
        DELAY(TRANSITION_LATENCY);
        arm_freq = bcm2835_cpufreq_get_clock_rate(sc,
            BCM2835_FIRMWARE_CLOCK_ID_ARM);

        /*
         * if non-turbo and lower than or equal min_freq,
         * clock down core and sdram to default first.
         */
        if (sc->turbo_mode != BCM2835_FIRMWARE_TURBO_ON) {
                core_freq = bcm2835_cpufreq_get_clock_rate(sc,
                    BCM2835_FIRMWARE_CLOCK_ID_CORE);
                if (rate_hz > MHZ2HZ(sc->arm_min_freq)) {
                        bcm2835_cpufreq_set_clock_rate(sc,
                            BCM2835_FIRMWARE_CLOCK_ID_CORE,
                            MHZ2HZ(sc->core_max_freq));
                        DELAY(TRANSITION_LATENCY);
                        bcm2835_cpufreq_set_clock_rate(sc,
                            BCM2835_FIRMWARE_CLOCK_ID_SDRAM,
                            MHZ2HZ(sc->sdram_max_freq));
                        DELAY(TRANSITION_LATENCY);
                } else {
                        if (sc->core_min_freq < DEFAULT_CORE_FREQUENCY &&
                            core_freq > DEFAULT_CORE_FREQUENCY) {
                                /* first, down to 250, then down to min */
                                DELAY(TRANSITION_LATENCY);
                                bcm2835_cpufreq_set_clock_rate(sc,
                                    BCM2835_FIRMWARE_CLOCK_ID_CORE,
                                    MHZ2HZ(DEFAULT_CORE_FREQUENCY));
                                DELAY(TRANSITION_LATENCY);
                                /* reset core voltage */
                                bcm2835_cpufreq_set_voltage(sc,
                                    BCM2835_FIRMWARE_VOLTAGE_ID_CORE, 0);
                                DELAY(TRANSITION_LATENCY);
                        }
                        bcm2835_cpufreq_set_clock_rate(sc,
                            BCM2835_FIRMWARE_CLOCK_ID_CORE,
                            MHZ2HZ(sc->core_min_freq));
                        DELAY(TRANSITION_LATENCY);
                        bcm2835_cpufreq_set_clock_rate(sc,
                            BCM2835_FIRMWARE_CLOCK_ID_SDRAM,
                            MHZ2HZ(sc->sdram_min_freq));
                        DELAY(TRANSITION_LATENCY);
                }
        }

        VC_UNLOCK(sc);

        if (resp_freq < 0 || arm_freq < 0 || resp_freq != arm_freq) {
                device_printf(dev, "wrong freq\n");
                return (EIO);
        }
        DPRINTF("cpufreq: %d -> %d\n", cur_freq, arm_freq);

        return (0);
}

static int
bcm2835_cpufreq_get(device_t dev, struct cf_setting *cf)
{
        struct bcm2835_cpufreq_softc *sc;
        int arm_freq;

        if (cf == NULL)
                return (EINVAL);

        sc = device_get_softc(dev);
        memset(cf, CPUFREQ_VAL_UNKNOWN, sizeof(*cf));
        cf->dev = NULL;

        /* get cuurent value */
        VC_LOCK(sc);
        arm_freq = bcm2835_cpufreq_get_clock_rate(sc,
            BCM2835_FIRMWARE_CLOCK_ID_ARM);
        VC_UNLOCK(sc);
        if (arm_freq < 0) {
                device_printf(dev, "can't get clock\n");
                return (EINVAL);
        }

        /* CPU clock in MHz or 100ths of a percent. */
        cf->freq = HZ2MHZ(arm_freq);
        /* Voltage in mV. */
        cf->volts = CPUFREQ_VAL_UNKNOWN;
        /* Power consumed in mW. */
        cf->power = CPUFREQ_VAL_UNKNOWN;
        /* Transition latency in us. */
        cf->lat = TRANSITION_LATENCY;
        /* Driver providing this setting. */
        cf->dev = dev;

        return (0);
}

static int
bcm2835_cpufreq_make_freq_list(device_t dev, struct cf_setting *sets,
    int *count)
{
        struct bcm2835_cpufreq_softc *sc;
        int freq, min_freq, volts, rem;
        int idx;

        sc = device_get_softc(dev);
        freq = sc->arm_max_freq;
        min_freq = sc->arm_min_freq;

        /* adjust head freq to STEP */
        rem = freq % MHZSTEP;
        freq -= rem;
        if (freq < min_freq)
                freq = min_freq;

        /* if non-turbo, add extra low freq */
        if (sc->turbo_mode != BCM2835_FIRMWARE_TURBO_ON)
                if (min_freq > cpufreq_lowest_freq)
                        min_freq = cpufreq_lowest_freq;

        /* XXX RPi2 have only 900/600MHz */
        idx = 0;
        volts = sc->min_voltage_core;
        sets[idx].freq = freq;
        sets[idx].volts = volts;
        sets[idx].lat = TRANSITION_LATENCY;
        sets[idx].dev = dev;
        idx++;
        if (freq != min_freq) {
                sets[idx].freq = min_freq;
                sets[idx].volts = volts;
                sets[idx].lat = TRANSITION_LATENCY;
                sets[idx].dev = dev;
                idx++;
        }
        *count = idx;

        return (0);
}

static int
bcm2835_cpufreq_settings(device_t dev, struct cf_setting *sets, int *count)
{
        struct bcm2835_cpufreq_softc *sc;

        if (sets == NULL || count == NULL)
                return (EINVAL);

        sc = device_get_softc(dev);
        if (sc->arm_min_freq < 0 || sc->arm_max_freq < 0) {
                printf("device is not configured\n");
                return (EINVAL);
        }

        /* fill data with unknown value */
        memset(sets, CPUFREQ_VAL_UNKNOWN, sizeof(*sets) * (*count));
        /* create new array up to count */
        bcm2835_cpufreq_make_freq_list(dev, sets, count);

        return (0);
}

static int
bcm2835_cpufreq_type(device_t dev, int *type)
{

        if (type == NULL)
                return (EINVAL);
        *type = CPUFREQ_TYPE_ABSOLUTE;

        return (0);
}

static device_method_t bcm2835_cpufreq_methods[] = {
        /* Device interface */
        DEVMETHOD(device_identify,      bcm2835_cpufreq_identify),
        DEVMETHOD(device_probe,         bcm2835_cpufreq_probe),
        DEVMETHOD(device_attach,        bcm2835_cpufreq_attach),
        DEVMETHOD(device_detach,        bcm2835_cpufreq_detach),

        /* cpufreq interface */
        DEVMETHOD(cpufreq_drv_set,      bcm2835_cpufreq_set),
        DEVMETHOD(cpufreq_drv_get,      bcm2835_cpufreq_get),
        DEVMETHOD(cpufreq_drv_settings, bcm2835_cpufreq_settings),
        DEVMETHOD(cpufreq_drv_type,     bcm2835_cpufreq_type),

        DEVMETHOD_END
};

static driver_t bcm2835_cpufreq_driver = {
        "bcm2835_cpufreq",
        bcm2835_cpufreq_methods,
        sizeof(struct bcm2835_cpufreq_softc),
};

DRIVER_MODULE(bcm2835_cpufreq, cpu, bcm2835_cpufreq_driver, 0, 0);
MODULE_DEPEND(bcm2835_cpufreq, bcm2835_firmware, 1, 1, 1);