/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2019 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>
#include "opt_platform.h"

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

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

#include <dev/iicbus/iiconf.h>
#include "iicbus_if.h"
#include "iicmux_if.h"
#include "iicmux.h"

/*------------------------------------------------------------------------------
 * iicbus methods, called by the iicbus functions in iiconf.c.
 *
 * All these functions return an IIC adapter-layer error code (because we are
 * pretending to be a host bridge/i2c controller).  Standard errno values
 * returned from these must be encoded using iic2errno().
 *----------------------------------------------------------------------------*/

static int
iicmux_callback(device_t dev, int index, caddr_t data)
{
        struct iicmux_softc *sc = device_get_softc(dev);
        struct iic_reqbus_data *rd;
        int err, i;

        /* If it's not one of the operations we know about, bail early. */
        if (index != IIC_REQUEST_BUS && index != IIC_RELEASE_BUS)
                return (iic2errno(EOPNOTSUPP));

        /*
         * Ensure that the data passed to us includes the device_t of the child
         * bus and device.  If missing, someone bypassed iicbus_request_bus()
         * and called this method directly using the old calling standard.  If
         * present, find the index of the child bus that called us.
         */
        rd = (struct iic_reqbus_data *)data;
        if (!(rd->flags & IIC_REQBUS_DEV))
                return (iic2errno(EINVAL));

        for (i = 0; i <= sc->maxbus && sc->childdevs[i] != rd->bus; ++i)
                continue;
        if (i > sc->maxbus)
                return (iic2errno(ENOENT));

        /*
         * If the operation is a release it "cannot fail".  Idle the downstream
         * bus, then release exclusive use of the upstream bus, and we're done.
         */
        if (index == IIC_RELEASE_BUS) {
                if (sc->debugmux > 0) {
                        device_printf(dev, "idle the bus for %s on bus %s\n",
                            device_get_nameunit(rd->dev),
                            device_get_nameunit(rd->bus));
                }
                IICMUX_BUS_SELECT(dev, IICMUX_SELECT_IDLE, rd);
                iicbus_release_bus(sc->busdev, dev);
                return (IIC_NOERR);
        }

        if (sc->debugmux > 0) {
                device_printf(dev, "select bus idx %d for %s on bus %s\n", i,
                    device_get_nameunit(rd->dev), device_get_nameunit(rd->bus));
        }

        /*
         * The operation is a request for exclusive use.  First we have to
         * request exclusive use of our upstream bus.  If multiple slave devices
         * from our different child buses attempt to do IO at the same time,
         * this is what ensures that they don't switch the bus out from under
         * each other. The first one in proceeds and others wait here (or get an
         * EWOULDBLOCK return if they're using IIC_DONTWAIT).
         */
        if ((err = iicbus_request_bus(sc->busdev, dev, rd->flags)) != 0)
                return (err); /* Already an IIC error code. */

        /*
         * Now that we own exclusive use of the upstream bus, connect it to the
         * downstream bus where the request came from.
         */
        if ((err = IICMUX_BUS_SELECT(dev, i, rd)) != 0)
                iicbus_release_bus(sc->busdev, dev);

        return (err);
}

static u_int
iicmux_get_frequency(device_t dev, u_char speed)
{
        struct iicmux_softc *sc = device_get_softc(dev);

        return (IICBUS_GET_FREQUENCY(sc->busdev, speed));
}

#ifdef FDT
static phandle_t
iicmux_get_node(device_t dev, device_t child)
{
        struct iicmux_softc *sc = device_get_softc(dev);
        int i;

        for (i = 0; i <= sc->maxbus; ++i) {
                if (sc->childdevs[i] == child)
                        return (sc->childnodes[i]);
        }
        return (0); /* null handle */
}
#endif

static int
iicmux_intr(device_t dev, int event, char *buf)
{
        struct iicmux_softc *sc = device_get_softc(dev);

        /* XXX iicbus_intr() in iiconf.c should return status. */

        iicbus_intr(sc->busdev, event, buf);
        return (0);
}

static int
iicmux_read(device_t dev, char *buf, int len, int *bytes, int last, int delay)
{
        struct iicmux_softc *sc = device_get_softc(dev);

        return (iicbus_read(sc->busdev, buf, len, bytes, last, delay));
}

static int
iicmux_repeated_start(device_t dev, u_char slave, int timeout)
{
        struct iicmux_softc *sc = device_get_softc(dev);

        return (iicbus_repeated_start(sc->busdev, slave, timeout));
}

static int
iicmux_reset(device_t dev, u_char speed, u_char addr, u_char *oldaddr)
{
        struct iicmux_softc *sc = device_get_softc(dev);

        return (iicbus_reset(sc->busdev, speed, addr, oldaddr));
}

static int
iicmux_start(device_t dev, u_char slave, int timeout)
{
        struct iicmux_softc *sc = device_get_softc(dev);

        return (iicbus_start(sc->busdev, slave, timeout));
}

static int
iicmux_stop(device_t dev)
{
        struct iicmux_softc *sc = device_get_softc(dev);

        return (iicbus_stop(sc->busdev));
}

static int
iicmux_transfer( device_t dev, struct iic_msg *msgs, uint32_t nmsgs)
{
        struct iicmux_softc *sc = device_get_softc(dev);

        return (iicbus_transfer(sc->busdev, msgs, nmsgs));
}

static int
iicmux_write(device_t dev, const char *buf, int len, int *bytes, int timeout)
{
        struct iicmux_softc *sc = device_get_softc(dev);

        return (iicbus_write(sc->busdev, buf, len, bytes, timeout));
}

/*------------------------------------------------------------------------------
 * iicmux helper functions, called by hardware-specific drivers.
 * All these functions return a standard errno value.
 *----------------------------------------------------------------------------*/

int
iicmux_add_child(device_t dev, device_t child, int busidx)
{
        struct iicmux_softc *sc = device_get_softc(dev);

        if (busidx >= sc->numbuses) {
                device_printf(dev,
                    "iicmux_add_child: bus idx %d too big", busidx);
                return (EINVAL);
        }
        if (sc->childdevs[busidx] != NULL) {
                device_printf(dev, "iicmux_add_child: bus idx %d already added",
                    busidx);
                return (EINVAL);
        }

        sc->childdevs[busidx] = child;
        if (sc->maxbus < busidx)
                sc->maxbus = busidx;

        return (0);
}

static int
iicmux_attach_children(struct iicmux_softc *sc)
{
        int i;
#ifdef FDT
        phandle_t child, node, parent;
        pcell_t idx;

        /*
         * Find our FDT node.  Child nodes within our node will become our
         * iicbus children.
         */
        if((node = ofw_bus_get_node(sc->dev)) == 0) {
                device_printf(sc->dev, "cannot find FDT node\n");
                return (ENOENT);
        }

        /*
         * First we have to see if there is a child node named "i2c-mux".  If it
         * exists, all children of that node are buses, else all children of the
         * device node are buses.
         */
        if ((parent = ofw_bus_find_child(node, "i2c-mux")) == 0)
                parent = node;

        /*
         * Attach the children represented in the device tree.
         */
        for (child = OF_child(parent); child != 0; child = OF_peer(child)) {
                if (OF_getencprop(child, "reg", &idx, sizeof(idx)) == -1) {
                        device_printf(sc->dev,
                            "child bus missing required 'reg' property\n");
                        continue;
                }
                if (idx >= sc->numbuses) {
                        device_printf(sc->dev,
                            "child bus 'reg' property %d exceeds the number "
                            "of buses supported by the device (%d)\n",
                            idx, sc->numbuses);
                        continue;
                }
                sc->childdevs[idx] = device_add_child(sc->dev, "iicbus", DEVICE_UNIT_ANY);
                sc->childnodes[idx] = child;
                if (sc->maxbus < (int)idx)
                        sc->maxbus = idx;
        }

        /* If we configured anything using FDT data, we're done. */
        if (sc->maxbus >= 0)
                return (0);
#endif /* FDT */

        /*
         * If we make it to here, we didn't add any children based on FDT data.
         * Add an iicbus child for every downstream bus supported by the mux.
         */
        for (i = 0; i < sc->numbuses; ++i) {
                sc->childdevs[i] = device_add_child(sc->dev, "iicbus", DEVICE_UNIT_ANY);
                sc->maxbus = i;
        }

        return (0);
}

int
iicmux_attach(device_t dev, device_t busdev, int numbuses)
{
        struct iicmux_softc *sc = device_get_softc(dev);
        int err;

        if (numbuses >= IICMUX_MAX_BUSES) {
                device_printf(dev, "iicmux_attach: numbuses %d > max %d\n",
                    numbuses, IICMUX_MAX_BUSES);
                return (EINVAL);
        }

        sc->dev = dev;
        sc->busdev = busdev;
        sc->maxbus = -1;
        sc->numbuses = numbuses;

        if ((err = iicmux_attach_children(sc)) != 0)
                return (err);

        SYSCTL_ADD_UINT(device_get_sysctl_ctx(sc->dev),
            SYSCTL_CHILDREN(device_get_sysctl_tree(sc->dev)), OID_AUTO,
            "debugmux", CTLFLAG_RWTUN, &sc->debugmux, 0, "debug mux operations");

        return (0);
}

int
iicmux_detach(device_t dev)
{
        struct iicmux_softc *sc = device_get_softc(dev);
        int err, i;

        /* Delete only the children we added in iicmux_add* functions. */
        for (i = 0; i <= sc->maxbus; ++i) {
                if (sc->childdevs[i] == NULL)
                        continue;
                if ((err = device_delete_child(dev, sc->childdevs[i])) != 0)
                        return (err);
                sc->childdevs[i] = NULL;
        }

        return (0);
}

static device_method_t iicmux_methods [] = {
        /* iicbus_if methods */
        DEVMETHOD(iicbus_intr,                  iicmux_intr),
        DEVMETHOD(iicbus_callback,              iicmux_callback),
        DEVMETHOD(iicbus_repeated_start,        iicmux_repeated_start),
        DEVMETHOD(iicbus_start,                 iicmux_start),
        DEVMETHOD(iicbus_stop,                  iicmux_stop),
        DEVMETHOD(iicbus_read,                  iicmux_read),
        DEVMETHOD(iicbus_write,                 iicmux_write),
        DEVMETHOD(iicbus_reset,                 iicmux_reset),
        DEVMETHOD(iicbus_transfer,              iicmux_transfer),
        DEVMETHOD(iicbus_get_frequency,         iicmux_get_frequency),

#ifdef FDT
        /* ofwbus_if methods */
        DEVMETHOD(ofw_bus_get_node,             iicmux_get_node),
#endif

        DEVMETHOD_END
};

static int
iicmux_modevent(module_t mod, int type, void *unused)
{
        switch (type) {
        case MOD_LOAD:
                return 0;
        case MOD_UNLOAD:
                return 0;
        }
        return EINVAL;
}

static moduledata_t iicmux_mod = {
        "iicmux",
        iicmux_modevent,
        0
};

DEFINE_CLASS_0(iicmux, iicmux_driver, iicmux_methods,
    sizeof(struct iicmux_softc));

DECLARE_MODULE(iicmux, iicmux_mod, SI_SUB_DRIVERS, SI_ORDER_ANY);
MODULE_VERSION(iicmux, 1);

MODULE_DEPEND(iicmux, iicbus, 1, 1, 1);