/*-
 * Copyright (c) 2015 M. Warner Losh <imp@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>
#include "opt_platform.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/gpio.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/mutex.h>

#include <dev/gpio/gpiobusvar.h>
#include <dev/ow/owll.h>

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

static struct ofw_compat_data compat_data[] = {
        {"w1-gpio",  true},
        {NULL,       false}
};
OFWBUS_PNP_INFO(compat_data);
SIMPLEBUS_PNP_INFO(compat_data);
#endif /* FDT */

#define OW_PIN          0

#define OWC_GPIOBUS_LOCK(_sc)           mtx_lock(&(_sc)->sc_mtx)
#define OWC_GPIOBUS_UNLOCK(_sc)         mtx_unlock(&(_sc)->sc_mtx)
#define OWC_GPIOBUS_LOCK_INIT(_sc) \
        mtx_init(&_sc->sc_mtx, device_get_nameunit(_sc->sc_dev), \
            "owc_gpiobus", MTX_DEF)
#define OWC_GPIOBUS_LOCK_DESTROY(_sc)   mtx_destroy(&_sc->sc_mtx);

struct owc_gpiobus_softc 
{
        device_t        sc_dev;
        gpio_pin_t      sc_pin;
        struct mtx      sc_mtx;
};

static int owc_gpiobus_probe(device_t);
static int owc_gpiobus_attach(device_t);
static int owc_gpiobus_detach(device_t);

static int
owc_gpiobus_probe(device_t dev)
{
        int rv;

        /*
         * By default we only bid to attach if specifically added by our parent
         * (usually via hint.owc_gpiobus.#.at=busname).  On FDT systems we bid
         * as the default driver based on being configured in the FDT data.
         */
        rv = BUS_PROBE_NOWILDCARD;

#ifdef FDT
        if (ofw_bus_status_okay(dev) &&
            ofw_bus_search_compatible(dev, compat_data)->ocd_data)
                rv = BUS_PROBE_DEFAULT;
#endif

        device_set_desc(dev, "GPIO one-wire bus");

        return (rv);
}

static int
owc_gpiobus_attach(device_t dev)
{
        struct owc_gpiobus_softc *sc;
        int err;

        sc = device_get_softc(dev);
        sc->sc_dev = dev;

#ifdef FDT
        /* Try to configure our pin from fdt data on fdt-based systems. */
        err = gpio_pin_get_by_ofw_idx(dev, ofw_bus_get_node(dev), OW_PIN,
            &sc->sc_pin);
#else
        err = ENOENT;
#endif
        /*
         * If we didn't get configured by fdt data and our parent is gpiobus,
         * see if we can be configured by the bus (allows hinted attachment even
         * on fdt-based systems).
         */
        if (err != 0 &&
            strcmp("gpiobus", device_get_name(device_get_parent(dev))) == 0)
                err = gpio_pin_get_by_child_index(dev, OW_PIN, &sc->sc_pin);

        /* If we didn't get configured by either method, whine and punt. */
        if (err != 0) {
                device_printf(sc->sc_dev,
                    "cannot acquire gpio pin (config error)\n");
                return (err);
        }

        OWC_GPIOBUS_LOCK_INIT(sc);

        /*
         * Add the ow bus as a child, but defer probing and attaching it until
         * interrupts work, because we can't do IO for them until we can read
         * the system timecounter (which initializes after device attachments).
         */
        device_add_child(sc->sc_dev, "ow", DEVICE_UNIT_ANY);
        bus_delayed_attach_children(dev);
        return (0);
}

static int
owc_gpiobus_detach(device_t dev)
{
        struct owc_gpiobus_softc *sc;
        int err;

        sc = device_get_softc(dev);

        if ((err = bus_generic_detach(dev)) != 0)
                return (err);

        gpio_pin_release(sc->sc_pin);
        OWC_GPIOBUS_LOCK_DESTROY(sc);

        return (0);
}

/*
 * In the diagrams below, R is driven by the resistor pullup, M is driven by the
 * master, and S is driven by the slave / target.
 */

/*
 * These macros let what why we're doing stuff shine in the code
 * below, and let the how be confined to here.
 */
#define OUTPIN(sc)      gpio_pin_setflags((sc)->sc_pin, GPIO_PIN_OUTPUT)
#define INPIN(sc)       gpio_pin_setflags((sc)->sc_pin, GPIO_PIN_INPUT)
#define GETPIN(sc, bp)  gpio_pin_is_active((sc)->sc_pin, (bp))
#define LOW(sc)         gpio_pin_set_active((sc)->sc_pin, false)

/*
 * WRITE-ONE (see owll_if.m for timings) From Figure 4-1 AN-937
 *
 *                     |<---------tSLOT---->|<-tREC->|
 *      High    RRRRM  |        RRRRRRRRRRRR|RRRRRRRRM
 *                   M |       R |     |  |           M
 *                    M|      R  |     |  |            M
 *      Low            MMMMMMM   |     |  |             MMMMMM...
 *                     |<-tLOW1->|     |  |
 *                     |<------15us--->|  |
 *                     |<--------60us---->|
 */
static int
owc_gpiobus_write_one(device_t dev, struct ow_timing *t)
{
        struct owc_gpiobus_softc *sc;

        sc = device_get_softc(dev);

        critical_enter();

        /* Force low */
        OUTPIN(sc);
        LOW(sc);
        DELAY(t->t_low1);

        /* Allow resistor to float line high */
        INPIN(sc);
        DELAY(t->t_slot - t->t_low1 + t->t_rec);

        critical_exit();

        return (0);
}

/*
 * WRITE-ZERO (see owll_if.m for timings) From Figure 4-2 AN-937
 *
 *                     |<---------tSLOT------>|<-tREC->|
 *      High    RRRRM  |                    | |RRRRRRRM
 *                   M |                    | R        M
 *                    M|         |     |    |R          M
 *      Low            MMMMMMMMMMMMMMMMMMMMMR            MMMMMM...
 *                     |<--15us->|     |    |
 *                     |<------60us--->|    |
 *                     |<-------tLOW0------>|
 */
static int
owc_gpiobus_write_zero(device_t dev, struct ow_timing *t)
{
        struct owc_gpiobus_softc *sc;

        sc = device_get_softc(dev);

        critical_enter();

        /* Force low */
        OUTPIN(sc);
        LOW(sc);
        DELAY(t->t_low0);

        /* Allow resistor to float line high */
        INPIN(sc);
        DELAY(t->t_slot - t->t_low0 + t->t_rec);

        critical_exit();

        return (0);
}

/*
 * READ-DATA (see owll_if.m for timings) From Figure 4-3 AN-937
 *
 *                     |<---------tSLOT------>|<-tREC->|
 *      High    RRRRM  |        rrrrrrrrrrrrrrrRRRRRRRM
 *                   M |       r            | R        M
 *                    M|      r         |   |R          M
 *      Low            MMMMMMMSSSSSSSSSSSSSSR            MMMMMM...
 *                     |<tLOWR>< sample >   |
 *                     |<------tRDV---->|   |
 *                                    ->|   |<-tRELEASE
 *
 * r -- allowed to pull high via the resitor when slave writes a 1-bit
 *
 */
static int
owc_gpiobus_read_data(device_t dev, struct ow_timing *t, int *bit)
{
        struct owc_gpiobus_softc *sc;
        bool sample;
        sbintime_t then, now;

        sc = device_get_softc(dev);

        critical_enter();

        /* Force low for t_lowr microseconds */
        then = sbinuptime();
        OUTPIN(sc);
        LOW(sc);
        DELAY(t->t_lowr);

        /*
         * Slave is supposed to hold the line low for t_rdv microseconds for 0
         * and immediately float it high for a 1. This is measured from the
         * master's pushing the line low.
         */
        INPIN(sc);
        do {
                now = sbinuptime();
                GETPIN(sc, &sample);
        } while (now - then < (t->t_rdv + 2) * SBT_1US && sample == false);
        critical_exit();

        if (now - then < t->t_rdv * SBT_1US)
                *bit = 1;
        else
                *bit = 0;

        /* Wait out the rest of t_slot */
        do {
                now = sbinuptime();
        } while (now - then < (t->t_slot + t->t_rec) * SBT_1US);

        return (0);
}

/*
 * RESET AND PRESENCE PULSE (see owll_if.m for timings) From Figure 4-4 AN-937
 *
 *                                  |<---------tRSTH------------>|
 *      High RRRM  |              | RRRRRRRS           |  RRRR RRM
 *               M |              |R|      |S          | R        M
 *                M|              R |      | S         |R          M
 *      Low        MMMMMMMM MMMMMM| |      |  SSSSSSSSSS            MMMMMM
 *                 |<----tRSTL--->| |      |<-tPDL---->|
 *                 |            ->| |<-tR  |           |
 *                                  |<tPDH>|
 *
 * Note: for Regular Speed operations, tRSTL + tR should be less than 960us to
 * avoid interfering with other devices on the bus.
 *
 * Return values in *bit:
 *  -1 = Bus wiring error (stuck low).
 *   0 = no presence pulse
 *   1 = presence pulse detected
 */
static int
owc_gpiobus_reset_and_presence(device_t dev, struct ow_timing *t, int *bit)
{
        struct owc_gpiobus_softc *sc;
        bool sample;

        sc = device_get_softc(dev);

        /*
         * Read the current state of the bus. The steady state of an idle bus is
         * high. Badly wired buses that are missing the required pull up, or
         * that have a short circuit to ground cause all kinds of mischief when
         * we try to read them later. Return EIO if the bus is currently low.
         */
        INPIN(sc);
        GETPIN(sc, &sample);
        if (sample == false) {
                *bit = -1;
                return (EIO);
        }

        critical_enter();

        /* Force low */
        OUTPIN(sc);
        LOW(sc);
        DELAY(t->t_rstl);

        /* Allow resistor to float line high and then wait for reset pulse */
        INPIN(sc);
        DELAY(t->t_pdh + t->t_pdl / 2);

        /* Read presence pulse  */
        GETPIN(sc, &sample);
        *bit = sample;

        critical_exit();

        DELAY(t->t_rsth - (t->t_pdh + t->t_pdl / 2));   /* Timing not critical for this one */

        /*
         * Read the state of the bus after we've waited past the end of the rest
         * window. It should return to high. If it is low, then we have some
         * problem and should abort the reset.
         */
        GETPIN(sc, &sample);
        if (sample == false) {
                *bit = -1;
                return (EIO);
        }

        return (0);
}

static device_method_t owc_gpiobus_methods[] = {
        /* Device interface */
        DEVMETHOD(device_probe,         owc_gpiobus_probe),
        DEVMETHOD(device_attach,        owc_gpiobus_attach),
        DEVMETHOD(device_detach,        owc_gpiobus_detach),

        DEVMETHOD(owll_write_one,       owc_gpiobus_write_one),
        DEVMETHOD(owll_write_zero,      owc_gpiobus_write_zero),
        DEVMETHOD(owll_read_data,       owc_gpiobus_read_data),
        DEVMETHOD(owll_reset_and_presence,      owc_gpiobus_reset_and_presence),
        DEVMETHOD_END
};

static driver_t owc_gpiobus_driver = {
        "owc",
        owc_gpiobus_methods,
        sizeof(struct owc_gpiobus_softc),
};

#ifdef FDT
DRIVER_MODULE(owc_gpiobus, simplebus, owc_gpiobus_driver, 0, 0);
#endif

DRIVER_MODULE(owc_gpiobus, gpiobus, owc_gpiobus_driver, 0, 0);
MODULE_DEPEND(owc_gpiobus, ow, 1, 1, 1);
MODULE_DEPEND(owc_gpiobus, gpiobus, 1, 1, 1);
MODULE_VERSION(owc_gpiobus, 1);