/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2017 Ian Lepore <ian@freebsd.org>
 *
 * 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>
/*
 * Driver for NXP real-time clock/calendar chips:
 *  - PCF8563 = low power, countdown timer
 *  - PCA8565 = like PCF8563, automotive temperature range
 *  - PCF8523 = low power, countdown timer, oscillator freq tuning, 2 timers
 *  - PCF2127 = like PCF8523, industrial, tcxo, tamper/ts, i2c & spi, 512B ram
 *  - PCA2129 = like PCF8523, automotive, tcxo, tamper/ts, i2c & spi, (note 1)
 *  - PCF2129 = like PCF8523, industrial, tcxo, tamper/ts, i2c & spi, (note 1)
 *
 *  Most chips have a countdown timer, ostensibly intended to generate periodic
 *  interrupt signals on an output pin.  The timer is driven from the same
 *  divider chain that clocks the time of day registers, and they start counting
 *  in sync when the STOP bit is cleared after the time and timer registers are
 *  set.  The timer register can also be read on the fly, so we use it to count
 *  fractional seconds and get a resolution of ~15ms.
 *
 *  [1] Note that the datasheets for the PCx2129 chips state that they have only
 *  a watchdog timer, not a countdown timer.  Empirical testing shows that the
 *  countdown timer is actually there and it works fine, except that it can't
 *  trigger an interrupt or toggle an output pin like it can on other chips.  We
 *  don't care about interrupts and output pins, we just read the timer register
 *  to get better resolution.
 */

#include "opt_platform.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/clock.h>
#include <sys/kernel.h>
#include <sys/libkern.h>
#include <sys/module.h>
#include <sys/sysctl.h>

#include <dev/iicbus/iicbus.h>
#include <dev/iicbus/iiconf.h>
#ifdef FDT
#include <dev/ofw/openfirm.h>
#include <dev/ofw/ofw_bus.h>
#include <dev/ofw/ofw_bus_subr.h>
#endif

#include "clock_if.h"
#include "iicbus_if.h"

/*
 * I2C address 1010 001x : PCA2129 PCF2127 PCF2129 PCF8563 PCF8565
 * I2C address 1101 000x : PCF8523
 */
#define PCF8563_ADDR            0xa2
#define PCF8523_ADDR            0xd0

/*
 * Registers, bits within them, and masks that are common to all chip types.
 */
#define PCF85xx_R_CS1           0x00    /* CS1 and CS2 control regs are in */
#define PCF85xx_R_CS2           0x01    /* the same location on all chips. */

#define PCF85xx_B_CS1_STOP      0x20    /* Stop time incrementing bit */
#define PCF85xx_B_SECOND_OS     0x80    /* Oscillator Stopped bit */

#define PCF85xx_M_SECOND        0x7f    /* Masks for all BCD time regs... */
#define PCF85xx_M_MINUTE        0x7f
#define PCF85xx_M_12HOUR        0x1f
#define PCF85xx_M_24HOUR        0x3f
#define PCF85xx_M_DAY           0x3f
#define PCF85xx_M_MONTH         0x1f
#define PCF85xx_M_YEAR          0xff

/*
 * PCF2127-specific registers, bits, and masks.
 */
#define PCF2127_R_TMR_CTL       0x10    /* Timer/watchdog control */

#define PCF2127_M_TMR_CTRL      0xe3    /* Mask off undef bits */

#define PCF2127_B_TMR_CD        0x40    /* Run in countdown mode */
#define PCF2127_B_TMR_64HZ      0x01    /* Timer frequency 64Hz */

#define PCF2127_R_TS_CTL        0x12    /* Timestamp control */
#define PCF2127_B_TSOFF         0x40    /* Turn off timestamp function */

#define PCF2127_R_AGING_OFFSET  0x19    /* Frequency aging offset in PPM */

/*
 * PCA/PCF2129-specific registers, bits, and masks.
 */
#define PCF2129_B_CS1_12HR      0x04    /* Use 12-hour (AM/PM) mode bit */
#define PCF2129_B_CLKOUT_OTPR   0x20    /* OTP refresh command */
#define PCF2129_B_CLKOUT_HIGHZ  0x07    /* Clock Out Freq = disable */

/*
 * PCF8523-specific registers, bits, and masks.
 */
#define PCF8523_R_CS3           0x02    /* Control and status reg 3 */
#define PCF8523_R_SECOND        0x03    /* Seconds */
#define PCF8523_R_TMR_CLKOUT    0x0F    /* Timer and clockout control */
#define PCF8523_R_TMR_A_FREQ    0x10    /* Timer A frequency control */
#define PCF8523_R_TMR_A_COUNT   0x11    /* Timer A count */

#define PCF8523_M_TMR_A_FREQ    0x07    /* Mask off undef bits */

#define PCF8523_B_HOUR_PM       0x20    /* PM bit */
#define PCF8523_B_CS1_SOFTRESET 0x58    /* Initiate Soft Reset bits */
#define PCF8523_B_CS1_12HR      0x08    /* Use 12-hour (AM/PM) mode bit */
#define PCF8523_B_CLKOUT_TACD   0x02    /* TimerA runs in CountDown mode */
#define PCF8523_B_CLKOUT_HIGHZ  0x38    /* Clock Out Freq = disable */
#define PCF8523_B_TMR_A_64HZ    0x01    /* Timer A freq 64Hz */

#define PCF8523_M_CS3_PM        0xE0    /* Power mode mask */
#define PCF8523_B_CS3_PM_NOBAT  0xE0    /* PM bits: no battery usage */
#define PCF8523_B_CS3_PM_STD    0x00    /* PM bits: standard */
#define PCF8523_B_CS3_PM_DSNBM  0xa0    /* PM bits: direct switch, no bat mon */
#define PCF8523_B_CS3_BLF       0x04    /* Battery Low Flag bit */

/*
 * PCF8563-specific registers, bits, and masks.
 */
#define PCF8563_R_SECOND        0x02    /* Seconds */

#define PCF8563_R_CLKOUT        0x0d    /* Clock output control */

#define PCF8563_R_TMR_CTRL      0x0e    /* Timer control */
#define PCF8563_R_TMR_COUNT     0x0f    /* Timer count */

#define PCF8563_M_TMR_CTRL      0x93    /* Mask off undef bits */

#define PCF8563_B_TMR_ENABLE    0x80    /* Enable countdown timer */
#define PCF8563_B_TMR_64HZ      0x01    /* Timer frequency 64Hz */

#define PCF8563_B_MONTH_C       0x80    /* Century bit */

/*
 * We use the countdown timer for fractional seconds.  We program it for 64 Hz,
 * the fastest available rate that doesn't roll over in less than a second.
 */
#define TMR_TICKS_SEC           64
#define TMR_TICKS_HALFSEC       32

/*
 * The chip types we support.
 */
enum {
        TYPE_NONE,
        TYPE_PCA2129,
        TYPE_PCA8565,
        TYPE_PCF2127,
        TYPE_PCF2129,
        TYPE_PCF8523,
        TYPE_PCF8563,

        TYPE_COUNT
};
static const char *desc_strings[] = {
        "",
        "NXP PCA2129 RTC",
        "NXP PCA8565 RTC",
        "NXP PCF2127 RTC",
        "NXP PCF2129 RTC",
        "NXP PCF8523 RTC",
        "NXP PCF8563 RTC",
};
CTASSERT(nitems(desc_strings) == TYPE_COUNT);

/*
 * The time registers in the order they are laid out in hardware.
 */
struct time_regs {
        uint8_t sec, min, hour, day, wday, month, year;
};

struct nxprtc_softc {
        device_t        dev;
        device_t        busdev;
        struct intr_config_hook
                        config_hook;
        u_int           flags;          /* SC_F_* flags */
        u_int           chiptype;       /* Type of PCF85xx chip */
        time_t          bat_time;       /* Next time to check battery */
        int             freqadj;        /* Current freq adj in PPM */
        uint8_t         secaddr;        /* Address of seconds register */
        uint8_t         tmcaddr;        /* Address of timer count register */
        bool            use_timer;      /* Use timer for fractional sec */
        bool            use_ampm;       /* Chip is set to use am/pm mode */
        bool            is212x;         /* Chip type is 2127 or 2129 */
};

#define SC_F_CPOL       (1 << 0)        /* Century bit means 19xx */

/*
 * When doing i2c IO, indicate that we need to wait for exclusive bus ownership,
 * but that we should not wait if we already own the bus.  This lets us put
 * iicbus_acquire_bus() calls with a non-recursive wait at the entry of our API
 * functions to ensure that only one client at a time accesses the hardware for
 * the entire series of operations it takes to read or write the clock.
 */
#define WAITFLAGS       (IIC_WAIT | IIC_RECURSIVE)

/*
 * We use the compat_data table to look up hint strings in the non-FDT case, so
 * define the struct locally when we don't get it from ofw_bus_subr.h.
 */
#ifdef FDT
typedef struct ofw_compat_data nxprtc_compat_data;
#else
typedef struct {
        const char *ocd_str;
        uintptr_t  ocd_data;
} nxprtc_compat_data;
#endif

static nxprtc_compat_data compat_data[] = {
        {"nxp,pca2129",     TYPE_PCA2129},
        {"nxp,pca8565",     TYPE_PCA8565},
        {"nxp,pcf2127",     TYPE_PCF2127},
        {"nxp,pcf2129",     TYPE_PCF2129},
        {"nxp,pcf8523",     TYPE_PCF8523},
        {"nxp,pcf8563",     TYPE_PCF8563},

        /* Undocumented compat strings known to exist in the wild... */
        {"pcf8563",         TYPE_PCF8563},
        {"phg,pcf8563",     TYPE_PCF8563},
        {"philips,pcf8563", TYPE_PCF8563},

        {NULL,              TYPE_NONE},
};

static int
nxprtc_readfrom(device_t slavedev, uint8_t regaddr, void *buffer,
    uint16_t buflen, int waithow)
{
        struct iic_msg msg;
        int err;
        uint8_t slaveaddr;

        /*
         * Two transfers back to back with a stop and start between them; first we
         * write the address-within-device, then we read from the device.  This
         * is used instead of the standard iicdev_readfrom() because some of the
         * chips we service don't support i2c repeat-start operations (grrrrr)
         * so we do two completely separate transfers with a full stop between.
         */
        slaveaddr = iicbus_get_addr(slavedev);

        msg.slave = slaveaddr;
        msg.flags = IIC_M_WR;
        msg.len   = 1;
        msg.buf   = &regaddr;

        if ((err = iicbus_transfer_excl(slavedev, &msg, 1, waithow)) != 0)
                return (err);

        msg.slave = slaveaddr;
        msg.flags = IIC_M_RD;
        msg.len   = buflen;
        msg.buf   = buffer;

        return (iicbus_transfer_excl(slavedev, &msg, 1, waithow));
}

static int
read_reg(struct nxprtc_softc *sc, uint8_t reg, uint8_t *val)
{

        return (nxprtc_readfrom(sc->dev, reg, val, sizeof(*val), WAITFLAGS));
}

static int
write_reg(struct nxprtc_softc *sc, uint8_t reg, uint8_t val)
{

        return (iicdev_writeto(sc->dev, reg, &val, sizeof(val), WAITFLAGS));
}

static int
read_timeregs(struct nxprtc_softc *sc, struct time_regs *tregs, uint8_t *tmr)
{
        int err;
        uint8_t sec, tmr1, tmr2;

        /*
         * The datasheet says loop to read the same timer value twice because it
         * does not freeze while reading.  To that we add our own logic that
         * the seconds register must be the same before and after reading the
         * timer, ensuring the fractional part is from the same second as tregs.
         */
        do {
                if (sc->use_timer) {
                        if ((err = read_reg(sc, sc->secaddr, &sec)) != 0)
                                break;
                        if ((err = read_reg(sc, sc->tmcaddr, &tmr1)) != 0)
                                break;
                        if ((err = read_reg(sc, sc->tmcaddr, &tmr2)) != 0)
                                break;
                        if (tmr1 != tmr2)
                                continue;
                }
                if ((err = nxprtc_readfrom(sc->dev, sc->secaddr, tregs,
                    sizeof(*tregs), WAITFLAGS)) != 0)
                        break;
        } while (sc->use_timer && tregs->sec != sec);

        /*
         * If the timer value is greater than our hz rate (or is zero),
         * something is wrong.  Maybe some other OS used the timer differently?
         * Just set it to zero.  Likewise if we're not using the timer.  After
         * the offset calc below, the zero turns into 32, the mid-second point,
         * which in effect performs 4/5 rounding, which is just the right thing
         * to do if we don't have fine-grained time.
         */
        if (!sc->use_timer || tmr1 > TMR_TICKS_SEC)
                tmr1 = 0;

        /*
         * Turn the downcounter into an upcounter.  The timer starts counting at
         * and rolls over at mid-second, so add half a second worth of ticks to
         * get its zero point back in sync with the tregs.sec rollover.
         */
        *tmr = (TMR_TICKS_SEC - tmr1 + TMR_TICKS_HALFSEC) % TMR_TICKS_SEC;

        return (err);
}

static int
write_timeregs(struct nxprtc_softc *sc, struct time_regs *tregs)
{

        return (iicdev_writeto(sc->dev, sc->secaddr, tregs,
            sizeof(*tregs), WAITFLAGS));
}

static int
freqadj_sysctl(SYSCTL_HANDLER_ARGS)
{
        struct nxprtc_softc *sc;
        int err, freqppm, newppm;

        sc = arg1;

        /* PPM range [-7,8] maps to reg value range [0,15] */
        freqppm = newppm = 8 - sc->freqadj;

        err = sysctl_handle_int(oidp, &newppm, 0, req);
        if (err != 0 || req->newptr == NULL)
                return (err);
        if (freqppm != newppm) {
                if (newppm < -7 || newppm > 8)
                        return (EINVAL);
                sc->freqadj = 8 - newppm;
                err = write_reg(sc, PCF2127_R_AGING_OFFSET, sc->freqadj);
        }

        return (err);
}

static int
pcf8523_battery_check(struct nxprtc_softc *sc)
{
        struct timespec ts;
        int err;
        uint8_t cs3;

        /* We check the battery when starting up, and then only once a day. */
        getnanouptime(&ts);
        if (ts.tv_sec < sc->bat_time)
                return (0);
        sc->bat_time = ts.tv_sec + (60 * 60 * 24);

        /*
         * The 8523, 2127, and 2129 chips have a "power manager" which includes
         * an optional battery voltage monitor and several choices for power
         * switching modes.  The battery monitor uses a lot of current and it
         * remains active when running from battery, making it the "drain my
         * battery twice as fast" mode.  So, we run the chip in direct-switching
         * mode with the battery monitor disabled, reducing the current draw
         * when running on battery from 1930nA to 880nA.  While it's not clear
         * from the datasheets, empirical testing shows that both disabling the
         * battery monitor and using direct-switch mode are required to get the
         * full power savings.
         *
         * There isn't any need to continuously monitor the battery voltage, so
         * this function is used to periodically enable the monitor, check the
         * voltage, then return to the low-power monitor-disabled mode.
         */
        err = write_reg(sc, PCF8523_R_CS3, PCF8523_B_CS3_PM_STD);
        if (err != 0) {
                device_printf(sc->dev, "cannot write CS3 reg\n");
                return (err);
        }
        pause_sbt("nxpbat", mstosbt(100), 0, 0);
        if ((err = read_reg(sc, PCF8523_R_CS3, &cs3)) != 0) {
                device_printf(sc->dev, "cannot read CS3 reg\n");
                return (err);
        }
        err = write_reg(sc, PCF8523_R_CS3, PCF8523_B_CS3_PM_DSNBM);
        if (err != 0) {
                device_printf(sc->dev, "cannot write CS3 reg\n");
                return (err);
        }

        if (cs3 & PCF8523_B_CS3_BLF)
                device_printf(sc->dev, "WARNING: RTC battery is low\n");

        return (0);
}

static int
pcf8523_start(struct nxprtc_softc *sc)
{
        struct sysctl_ctx_list *ctx;
        struct sysctl_oid_list *tree;
        struct csr {
                uint8_t cs1;
                uint8_t cs2;
                uint8_t cs3;
                uint8_t sec;
        } csr;
        int err;
        uint8_t clkout, freqadj;

        /* Read the control and status registers. */
        if ((err = nxprtc_readfrom(sc->dev, PCF85xx_R_CS1, &csr,
            sizeof(csr), WAITFLAGS)) != 0){
                device_printf(sc->dev, "cannot read RTC control regs\n");
                return (err);
        }

        /*
         * Do a full init if...
         *  - The chip power manager is in battery-disable mode.
         *  - The OS (oscillator stopped) bit is set (all power was lost).
         *  - The clock-increment STOP flag is set (this is just insane).
         */
        if ((csr.cs3 & PCF8523_M_CS3_PM) == PCF8523_B_CS3_PM_NOBAT ||
            (csr.cs1 & PCF85xx_B_CS1_STOP) || (csr.sec & PCF85xx_B_SECOND_OS)) {
                device_printf(sc->dev, 
                    "WARNING: RTC battery failed; time is invalid\n");

                /*
                 * For 212x series...
                 * - Turn off the POR-Override bit (used for mfg test only), 
                 *   by writing zero to cs 1 (all other bits power on as zero). 
                 * - Turn off the timestamp option to save the power used to
                 *   monitor that input pin.
                 * - Trigger OTP refresh by forcing the OTPR bit to zero then
                 *   back to 1, then wait 100ms for the refresh.
                 */
                if (sc->is212x) {
                        err = write_reg(sc, PCF85xx_R_CS1, 0);
                        if (err != 0) {
                                device_printf(sc->dev,
                                    "cannot write CS1 reg\n");
                                return (err);
                        }

                        err = write_reg(sc, PCF2127_R_TS_CTL, PCF2127_B_TSOFF);
                        if (err != 0) {
                                device_printf(sc->dev,
                                    "cannot write timestamp control\n");
                                return (err);
                        }

                        clkout = PCF2129_B_CLKOUT_HIGHZ;
                        err = write_reg(sc, PCF8523_R_TMR_CLKOUT, clkout);
                        if (err == 0)
                                err = write_reg(sc, PCF8523_R_TMR_CLKOUT,
                                    clkout | PCF2129_B_CLKOUT_OTPR);
                        if (err != 0) {
                                device_printf(sc->dev,
                                    "cannot write CLKOUT control\n");
                                return (err);
                        }
                        pause_sbt("nxpotp", mstosbt(100), mstosbt(10), 0);
                } else
                        clkout = PCF8523_B_CLKOUT_HIGHZ;

                /* All chips: set clock output pin to high-z to save power */
                if ((err = write_reg(sc, PCF8523_R_TMR_CLKOUT, clkout)) != 0) {
                        device_printf(sc->dev, "cannot write CLKOUT control\n");
                        return (err);
                }
        }

        /*
         * Check the battery voltage and report if it's low.  This also has the
         * side effect of (re-)initializing the power manager to low-power mode
         * when we come up after a power fail.
         */
        pcf8523_battery_check(sc);

        /*
         * Remember whether we're running in AM/PM mode.  The chip default is
         * 24-hour mode, but if we're co-existing with some other OS that
         * prefers AM/PM we can run that way too.
         *
         * Also, for 212x chips, retrieve the current frequency aging offset,
         * and set up the sysctl handler for reading/setting it.
         */
        if (sc->is212x) {
                if (csr.cs1 & PCF2129_B_CS1_12HR)
                        sc->use_ampm = true;

                err = read_reg(sc, PCF2127_R_AGING_OFFSET, &freqadj);
                if (err != 0) {
                        device_printf(sc->dev,
                            "cannot read AGINGOFFSET register\n");
                        return (err);
                }
                sc->freqadj = (int8_t)freqadj;

                ctx = device_get_sysctl_ctx(sc->dev);
                tree = SYSCTL_CHILDREN(device_get_sysctl_tree(sc->dev));

                SYSCTL_ADD_PROC(ctx, tree, OID_AUTO, "freqadj",
                    CTLFLAG_RWTUN | CTLTYPE_INT | CTLFLAG_MPSAFE, sc, 0,
                    freqadj_sysctl, "I", "Frequency adjust in PPM, range [-7,+8]");
        } else {
                if (csr.cs1 & PCF8523_B_CS1_12HR)
                        sc->use_ampm = true;
        }

        return (0);
}
static int
pcf8523_start_timer(struct nxprtc_softc *sc)
{
        int err;
        uint8_t clkout, stdclk, stdfreq, tmrfreq;

        /*
         * Read the timer control and frequency regs.  If they don't have the
         * values we normally program into them then the timer count doesn't
         * contain a valid fractional second, so zero it to prevent using a bad
         * value.  Then program the normal timer values so that on the first
         * settime call we'll begin to use fractional time.
         */
        if ((err = read_reg(sc, PCF8523_R_TMR_A_FREQ, &tmrfreq)) != 0)
                return (err);
        if ((err = read_reg(sc, PCF8523_R_TMR_CLKOUT, &clkout)) != 0)
                return (err);

        stdfreq = PCF8523_B_TMR_A_64HZ;
        stdclk = PCF8523_B_CLKOUT_TACD | PCF8523_B_CLKOUT_HIGHZ;

        if (clkout != stdclk || (tmrfreq & PCF8523_M_TMR_A_FREQ) != stdfreq) {
                if ((err = write_reg(sc, sc->tmcaddr, 0)) != 0)
                        return (err);
                if ((err = write_reg(sc, PCF8523_R_TMR_A_FREQ, stdfreq)) != 0)
                        return (err);
                if ((err = write_reg(sc, PCF8523_R_TMR_CLKOUT, stdclk)) != 0)
                        return (err);
        }
        return (0);
}

static int
pcf2127_start_timer(struct nxprtc_softc *sc)
{
        int err;
        uint8_t stdctl, tmrctl;

        /*
         * Set up timer if it's not already in the mode we normally run it.  See
         * the comment in pcf8523_start_timer() for more details.
         *
         * Note that the PCF2129 datasheet says it has no countdown timer, but
         * empirical testing shows that it works just fine for our purposes.
         */
        if ((err = read_reg(sc, PCF2127_R_TMR_CTL, &tmrctl)) != 0)
                return (err);

        stdctl = PCF2127_B_TMR_CD | PCF8523_B_TMR_A_64HZ;

        if ((tmrctl & PCF2127_M_TMR_CTRL) != stdctl) {
                if ((err = write_reg(sc, sc->tmcaddr, 0)) != 0)
                        return (err);
                if ((err = write_reg(sc, PCF2127_R_TMR_CTL, stdctl)) != 0)
                        return (err);
        }
        return (0);
}

static int
pcf8563_start(struct nxprtc_softc *sc)
{
        struct csr {
                uint8_t cs1;
                uint8_t cs2;
                uint8_t sec;
        } csr;
        int err;

        /* Read the control and status registers. */
        if ((err = nxprtc_readfrom(sc->dev, PCF85xx_R_CS1, &csr,
            sizeof(csr), WAITFLAGS)) != 0){
                device_printf(sc->dev, "cannot read RTC control regs\n");
                return (err);
        }

        /*
         * Do a full init if...
         *  - The OS (oscillator stopped) bit is set (all power was lost).  This
         *    bit is called VL (Voltage Low) in the 8563 datasheet.
         *  - The clock-increment STOP flag is set (this is just insane).
         */
        if ((csr.cs1 & PCF85xx_B_CS1_STOP) || (csr.sec & PCF85xx_B_SECOND_OS)) {
                device_printf(sc->dev, 
                    "WARNING: RTC battery failed; time is invalid\n");
                /*
                 * - Turn off the POR-Override bit (used for mfg test only), by
                 *   writing zero to cs 1 (all other bits power on as zero).
                 * - Turn off the clock output pin (to save battery power), by
                 *   writing zero to the clkout control reg.
                 */
                if ((err = write_reg(sc, PCF85xx_R_CS1, 0)) != 0) {
                        device_printf(sc->dev, "cannot write CS1 reg\n");
                        return (err);
                }

                if ((err = write_reg(sc, PCF8563_R_CLKOUT, 0)) != 0) {
                        device_printf(sc->dev, "cannot write CS1 reg\n");
                        return (err);
                }
        }

        return (0);
}

static int
pcf8563_start_timer(struct nxprtc_softc *sc)
{
        int err;
        uint8_t stdctl, tmrctl;

        /* See comment in pcf8523_start_timer().  */
        if ((err = read_reg(sc, PCF8563_R_TMR_CTRL, &tmrctl)) != 0)
                return (err);

        stdctl = PCF8563_B_TMR_ENABLE | PCF8563_B_TMR_64HZ;

        if ((tmrctl & PCF8563_M_TMR_CTRL) != stdctl) {
                if ((err = write_reg(sc, sc->tmcaddr, 0)) != 0)
                        return (err);
                if ((err = write_reg(sc, PCF8563_R_TMR_CTRL, stdctl)) != 0)
                        return (err);
        }
        return (0);
}

static void
nxprtc_start(void *dev)
{
        struct nxprtc_softc *sc;
        int clockflags, resolution;

        sc = device_get_softc((device_t)dev);
        config_intrhook_disestablish(&sc->config_hook);

        /* First do chip-specific inits. */
        switch (sc->chiptype) {
        case TYPE_PCA2129:
        case TYPE_PCF2129:
        case TYPE_PCF2127:
                sc->is212x = true;
                if (pcf8523_start(sc) != 0)
                        return;
                if (pcf2127_start_timer(sc) != 0) {
                        device_printf(sc->dev, "cannot set up timer\n");
                        return;
                }
                break;
        case TYPE_PCF8523:
                if (pcf8523_start(sc) != 0)
                        return;
                if (pcf8523_start_timer(sc) != 0) {
                        device_printf(sc->dev, "cannot set up timer\n");
                        return;
                }
                break;
        case TYPE_PCA8565:
        case TYPE_PCF8563:
                if (pcf8563_start(sc) != 0)
                        return;
                if (pcf8563_start_timer(sc) != 0) {
                        device_printf(sc->dev, "cannot set up timer\n");
                        return;
                }
                break;
        default:
                device_printf(sc->dev, "missing init code for this chiptype\n");
                return;
        }

        /*
         * Everything looks good if we make it to here; register as an RTC.  If
         * we're using the timer to count fractional seconds, our resolution is
         * 1e6/64, about 15.6ms.  Without the timer we still align the RTC clock
         * when setting it so our error is an average .5s when reading it.
         * Schedule our clock_settime() method to be called at a .495ms offset
         * into the second, because the clock hardware resets the divider chain
         * to the mid-second point when you set the time and it takes about 5ms
         * of i2c bus activity to set the clock.
         */
        resolution = sc->use_timer ? 1000000 / TMR_TICKS_SEC : 1000000 / 2;
        clockflags = CLOCKF_GETTIME_NO_ADJ | CLOCKF_SETTIME_NO_TS;
        clock_register_flags(sc->dev, resolution, clockflags);
        clock_schedule(sc->dev, 495000000);
}

static int
nxprtc_gettime(device_t dev, struct timespec *ts)
{
        struct bcd_clocktime bct;
        struct time_regs tregs;
        struct nxprtc_softc *sc;
        int err;
        uint8_t cs1, hourmask, tmrcount;

        sc = device_get_softc(dev);

        /*
         * Read the time, but before using it, validate that the oscillator-
         * stopped/power-fail bit is not set, and that the time-increment STOP
         * bit is not set in the control reg.  The latter can happen if there
         * was an error when setting the time.
         */
        if ((err = iicbus_request_bus(sc->busdev, sc->dev, IIC_WAIT)) == 0) {
                if ((err = read_timeregs(sc, &tregs, &tmrcount)) == 0) {
                        err = read_reg(sc, PCF85xx_R_CS1, &cs1);
                }
                iicbus_release_bus(sc->busdev, sc->dev);
        }
        if (err != 0)
                return (err);

        if ((tregs.sec & PCF85xx_B_SECOND_OS) || (cs1 & PCF85xx_B_CS1_STOP)) {
                device_printf(dev, "RTC clock not running\n");
                return (EINVAL); /* hardware is good, time is not. */
        }

        if (sc->use_ampm)
                hourmask = PCF85xx_M_12HOUR;
        else
                hourmask = PCF85xx_M_24HOUR;

        bct.nsec = ((uint64_t)tmrcount * 1000000000) / TMR_TICKS_SEC;
        bct.ispm = (tregs.hour & PCF8523_B_HOUR_PM) != 0;
        bct.sec  = tregs.sec   & PCF85xx_M_SECOND;
        bct.min  = tregs.min   & PCF85xx_M_MINUTE;
        bct.hour = tregs.hour  & hourmask;
        bct.day  = tregs.day   & PCF85xx_M_DAY;
        bct.mon  = tregs.month & PCF85xx_M_MONTH;
        bct.year = tregs.year  & PCF85xx_M_YEAR;

        /*
         * Old PCF8563 datasheets recommended that the C bit be 1 for 19xx and 0
         * for 20xx; newer datasheets don't recommend that.  We don't care,
         * but we may co-exist with other OSes sharing the hardware. Determine
         * existing polarity on a read so that we can preserve it on a write.
         */
        if (sc->chiptype == TYPE_PCF8563) {
                if (tregs.month & PCF8563_B_MONTH_C) {
                        if (bct.year < 0x70)
                                sc->flags |= SC_F_CPOL;
                } else if (bct.year >= 0x70)
                                sc->flags |= SC_F_CPOL;
        }

        clock_dbgprint_bcd(sc->dev, CLOCK_DBG_READ, &bct); 
        err = clock_bcd_to_ts(&bct, ts, sc->use_ampm);
        ts->tv_sec += utc_offset();

        return (err);
}

static int
nxprtc_settime(device_t dev, struct timespec *ts)
{
        struct bcd_clocktime bct;
        struct time_regs tregs;
        struct nxprtc_softc *sc;
        int err;
        uint8_t cflag, cs1;

        sc = device_get_softc(dev);

        /*
         * We stop the clock, set the time, then restart the clock.  Half a
         * second after restarting the clock it ticks over to the next second.
         * So to align the RTC, we schedule this function to be called when
         * system time is roughly halfway (.495) through the current second.
         *
         * Reserve use of the i2c bus and stop the RTC clock.  Note that if
         * anything goes wrong from this point on, we leave the clock stopped,
         * because we don't really know what state it's in.
         */
        if ((err = iicbus_request_bus(sc->busdev, sc->dev, IIC_WAIT)) != 0)
                return (err);
        if ((err = read_reg(sc, PCF85xx_R_CS1, &cs1)) != 0)
                goto errout;
        cs1 |= PCF85xx_B_CS1_STOP;
        if ((err = write_reg(sc, PCF85xx_R_CS1, cs1)) != 0)
                goto errout;

        /* Grab a fresh post-sleep idea of what time it is. */
        getnanotime(ts);
        ts->tv_sec -= utc_offset();
        ts->tv_nsec = 0;
        clock_ts_to_bcd(ts, &bct, sc->use_ampm);
        clock_dbgprint_bcd(sc->dev, CLOCK_DBG_WRITE, &bct);

        /* On 8563 set the century based on the polarity seen when reading. */
        cflag = 0;
        if (sc->chiptype == TYPE_PCF8563) {
                if ((sc->flags & SC_F_CPOL) != 0) {
                        if (bct.year >= 0x2000)
                                cflag = PCF8563_B_MONTH_C;
                } else if (bct.year < 0x2000)
                                cflag = PCF8563_B_MONTH_C;
        }

        tregs.sec   = bct.sec;
        tregs.min   = bct.min;
        tregs.hour  = bct.hour | (bct.ispm ? PCF8523_B_HOUR_PM : 0);
        tregs.day   = bct.day;
        tregs.month = bct.mon;
        tregs.year  = (bct.year & 0xff) | cflag;
        tregs.wday  = bct.dow;

        /*
         * Set the time, reset the timer count register, then start the clocks.
         */
        if ((err = write_timeregs(sc, &tregs)) != 0)
                goto errout;

        if ((err = write_reg(sc, sc->tmcaddr, TMR_TICKS_SEC)) != 0)
                return (err);

        cs1 &= ~PCF85xx_B_CS1_STOP;
        err = write_reg(sc, PCF85xx_R_CS1, cs1);

        /*
         * Check for battery-low.  The actual check is throttled to only occur
         * once a day, mostly to avoid spamming the user with frequent warnings.
         */
        pcf8523_battery_check(sc);

errout:

        iicbus_release_bus(sc->busdev, sc->dev);

        if (err != 0)
                device_printf(dev, "cannot write RTC time\n");

        return (err);
}

static int
nxprtc_get_chiptype(device_t dev)
{
#ifdef FDT

        return (ofw_bus_search_compatible(dev, compat_data)->ocd_data);
#else
        nxprtc_compat_data *cdata;
        const char *htype;
        int chiptype;

        /*
         * If given a chiptype hint string, loop through the ofw compat data
         * comparing the hinted chip type to the compat strings.  The table end
         * marker ocd_data is TYPE_NONE.
         */
        if (resource_string_value(device_get_name(dev), 
            device_get_unit(dev), "compatible", &htype) == 0) {
                for (cdata = compat_data; cdata->ocd_str != NULL; ++cdata) {
                        if (strcmp(htype, cdata->ocd_str) == 0)
                                break;
                }
                chiptype = cdata->ocd_data;
        } else
                chiptype = TYPE_NONE;

        /*
         * On non-FDT systems the historical behavior of this driver was to
         * assume a PCF8563; keep doing that for compatibility.
         */
        if (chiptype == TYPE_NONE)
                return (TYPE_PCF8563);
        else
                return (chiptype);
#endif
}

static int
nxprtc_probe(device_t dev)
{
        int chiptype, rv;

#ifdef FDT
        if (!ofw_bus_status_okay(dev))
                return (ENXIO);
        rv = BUS_PROBE_GENERIC;
#else
        rv = BUS_PROBE_NOWILDCARD;
#endif
        if ((chiptype = nxprtc_get_chiptype(dev)) == TYPE_NONE)
                return (ENXIO);

        device_set_desc(dev, desc_strings[chiptype]);
        return (rv);
}

static int
nxprtc_attach(device_t dev)
{
        struct nxprtc_softc *sc;

        sc = device_get_softc(dev);
        sc->dev = dev;
        sc->busdev = device_get_parent(dev);

        /* We need to know what kind of chip we're driving. */
        sc->chiptype = nxprtc_get_chiptype(dev);

        /* The features and some register addresses vary by chip type. */
        switch (sc->chiptype) {
        case TYPE_PCA2129:
        case TYPE_PCF2129:
        case TYPE_PCF2127:
        case TYPE_PCF8523:
                sc->secaddr = PCF8523_R_SECOND;
                sc->tmcaddr = PCF8523_R_TMR_A_COUNT;
                sc->use_timer = true;
                break;
        case TYPE_PCA8565:
        case TYPE_PCF8563:
                sc->secaddr = PCF8563_R_SECOND;
                sc->tmcaddr = PCF8563_R_TMR_COUNT;
                sc->use_timer = true;
                break;
        default:
                device_printf(dev, "impossible: cannot determine chip type\n");
                return (ENXIO);
        }

        /*
         * We have to wait until interrupts are enabled.  Sometimes I2C read
         * and write only works when the interrupts are available.
         */
        sc->config_hook.ich_func = nxprtc_start;
        sc->config_hook.ich_arg = dev;
        if (config_intrhook_establish(&sc->config_hook) != 0)
                return (ENOMEM);

        return (0);
}

static int
nxprtc_detach(device_t dev)
{

        clock_unregister(dev);
        return (0);
}

static device_method_t nxprtc_methods[] = {
        DEVMETHOD(device_probe,         nxprtc_probe),
        DEVMETHOD(device_attach,        nxprtc_attach),
        DEVMETHOD(device_detach,        nxprtc_detach),

        DEVMETHOD(clock_gettime,        nxprtc_gettime),
        DEVMETHOD(clock_settime,        nxprtc_settime),

        DEVMETHOD_END
};

static driver_t nxprtc_driver = {
        "nxprtc",
        nxprtc_methods,
        sizeof(struct nxprtc_softc),
};

DRIVER_MODULE(nxprtc, iicbus, nxprtc_driver, NULL, NULL);
MODULE_VERSION(nxprtc, 1);
MODULE_DEPEND(nxprtc, iicbus, IICBUS_MINVER, IICBUS_PREFVER, IICBUS_MAXVER);
IICBUS_FDT_PNP_INFO(compat_data);