/*      $NetBSD: i2cmux.c,v 1.13 2025/09/21 15:02:25 thorpej Exp $      */

/*-
 * Copyright (c) 2020 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Jason R. Thorpe.
 *
 * 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
 */

#if defined(__i386__) || defined(__amd64__) || defined(__aarch64__)
#include "acpica.h"
#endif

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: i2cmux.c,v 1.13 2025/09/21 15:02:25 thorpej Exp $");

#include <sys/types.h>
#include <sys/device.h>
#include <sys/kernel.h>
#include <sys/kmem.h>

#include <dev/fdt/fdtvar.h>
#include <dev/i2c/i2cvar.h>
#include <dev/i2c/i2cmuxvar.h>

#if NACPICA > 0
#include <dev/acpi/acpivar.h>
#endif

/*
 * i2c mux
 *
 * This works by interposing a set of virtual controllers behind the real
 * i2c controller.  We provide our own acquire and release functions that
 * perform the following tasks:
 *
 *      acquire -> acquire parent controller, program mux
 *
 *      release -> idle mux, release parent controller
 *
 * All of the actual I/O operations are transparently passed through.
 *
 * N.B. the locking order; the generic I2C layer has already acquired
 * our virtual controller's mutex before calling our acquire function,
 * and we will then acquire the real controller's mutex when we acquire
 * the bus, so the order is:
 *
 *      mux virtual controller -> parent controller
 *
 * These are common routines used by various i2c mux controller
 * implementations (gpio, pin mux, i2c device, etc.).
 */

/*****************************************************************************/

static int
iicmux_acquire_bus(void * const v, int const flags)
{
        struct iicmux_bus * const bus = v;
        struct iicmux_softc * const sc = bus->mux;
        int error;

        error = iic_acquire_bus(sc->sc_i2c_parent, flags);
        if (error) {
                return error;
        }

        error = sc->sc_config->acquire_bus(bus, flags);
        if (error) {
                iic_release_bus(sc->sc_i2c_parent, flags);
        }

        return error;
}

static void
iicmux_release_bus(void * const v, int const flags)
{
        struct iicmux_bus * const bus = v;
        struct iicmux_softc * const sc = bus->mux;

        sc->sc_config->release_bus(bus, flags);
        iic_release_bus(sc->sc_i2c_parent, flags);
}

static int
iicmux_exec(void * const v, i2c_op_t const op, i2c_addr_t const addr,
    const void * const cmdbuf, size_t const cmdlen, void * const databuf,
    size_t const datalen, int const flags)
{
        struct iicmux_bus * const bus = v;
        struct iicmux_softc * const sc = bus->mux;

        return iic_exec(sc->sc_i2c_parent, op, addr, cmdbuf, cmdlen,
                        databuf, datalen, flags);
}

/*****************************************************************************/

static int
iicmux_count_children(struct iicmux_softc * const sc)
{
        char name[32];
        int child, count;
        int mux_phandle = devhandle_to_of(sc->sc_i2c_mux_devhandle);

 restart:
        for (child = OF_child(mux_phandle), count = 0; child;
             child = OF_peer(child)) {
                if (OF_getprop(child, "name", name, sizeof(name)) <= 0) {
                        continue;
                }
                if (strcmp(name, "i2c-mux") == 0) {
                        /*
                         * The node we encountered is the actual parent
                         * of the i2c bus children.  Stash its phandle
                         * and restart the enumeration.
                         */
                        mux_phandle = child;
                        goto restart;
                }
                count++;
        }
        sc->sc_i2c_mux_devhandle =
            devhandle_from_of(sc->sc_i2c_mux_devhandle, mux_phandle);

        return count;
}

static void
iicmux_attach_bus(struct iicmux_softc * const sc, devhandle_t bus_devhandle,
    int const busidx)
{
        struct iicmux_bus * const bus = &sc->sc_busses[busidx];

        bus->mux = sc;
        bus->busidx = busidx;
        bus->devhandle = bus_devhandle;

        bus->bus_data = sc->sc_config->get_bus_info(bus);
        if (bus->bus_data == NULL) {
                aprint_error_dev(sc->sc_dev,
                    "unable to get info for bus %d\n", busidx);
                return;
        }

        iic_tag_init(&bus->controller);
        bus->controller.ic_cookie = bus;
        bus->controller.ic_channel = busidx;
        bus->controller.ic_acquire_bus = iicmux_acquire_bus;
        bus->controller.ic_release_bus = iicmux_release_bus;
        bus->controller.ic_exec = iicmux_exec;

        iicbus_attach_with_devhandle(sc->sc_dev, &bus->controller,
            bus->devhandle);
}

static void
iicmux_attach_fdt(struct iicmux_softc * const sc)
{

        sc->sc_nbusses = iicmux_count_children(sc);
        if (sc->sc_nbusses == 0) {
                return;
        }

        sc->sc_busses = kmem_zalloc(sizeof(*sc->sc_busses) * sc->sc_nbusses,
            KM_SLEEP);

#define BUS_DEVHANDLE(sc, c)            \
        devhandle_from_of((sc)->sc_i2c_mux_devhandle, (c))

        const int mux_phandle = devhandle_to_of(sc->sc_i2c_mux_devhandle);
        int child, idx;
        for (child = OF_child(mux_phandle), idx = 0; child;
             child = OF_peer(child), idx++) {
                KASSERT(idx < sc->sc_nbusses);
                iicmux_attach_bus(sc, BUS_DEVHANDLE(sc, child), idx);
        }
#undef BUS_DEVHANDLE
}

#if NACPICA > 0
static void
iicmux_attach_acpi(struct iicmux_softc * const sc)
{
        ACPI_HANDLE hdl = devhandle_to_acpi(sc->sc_i2c_mux_devhandle);
        struct acpi_devnode *devnode, *ad;
        int idx;

        devnode = acpi_match_node(hdl);
        KASSERT(devnode != NULL);

        /* Count child busses */
        sc->sc_nbusses = 0;
        SIMPLEQ_FOREACH(ad, &devnode->ad_child_head, ad_child_list) {
                if (ad->ad_devinfo->Type != ACPI_TYPE_DEVICE ||
                    !acpi_device_present(ad->ad_handle)) {
                        continue;
                }
                sc->sc_nbusses++;
        }

        sc->sc_busses = kmem_zalloc(sizeof(*sc->sc_busses) * sc->sc_nbusses,
            KM_SLEEP);

#define BUS_DEVHANDLE(sc, c)            \
        devhandle_from_acpi((sc)->sc_i2c_mux_devhandle, (c))

        /* Attach child busses */
        idx = 0;
        SIMPLEQ_FOREACH(ad, &devnode->ad_child_head, ad_child_list) {
                if (ad->ad_devinfo->Type != ACPI_TYPE_DEVICE ||
                    !acpi_device_present(ad->ad_handle)) {
                        continue;
                }
                iicmux_attach_bus(sc, BUS_DEVHANDLE(sc, ad->ad_handle), idx);
                idx++;
        }
#undef BUS_DEVHANDLE
}
#endif /* NACPICA > 0 */

void
iicmux_attach(struct iicmux_softc * const sc)
{
        /*
         * We expect sc->sc_config and sc->sc_i2c_parent to be initialized
         * by the front-end.
         */
        KASSERT(sc->sc_config != NULL);
        KASSERT(sc->sc_i2c_parent != NULL);

        /*
         * We start out assuming that the i2c bus nodes are children of
         * our own node.  We'll adjust later if we encounter an "i2c-mux"
         * node when counting our children.  If we encounter such a node,
         * then it's that node that is the parent of the i2c bus children.
         */
        sc->sc_i2c_mux_devhandle = device_handle(sc->sc_dev);

        /*
         * Gather up all of the various bits of information needed
         * for this particular type of i2c mux.
         */
        sc->sc_mux_data = sc->sc_config->get_mux_info(sc);
        if (sc->sc_mux_data == NULL) {
                aprint_error_dev(sc->sc_dev, "unable to get info for mux\n");
                return;
        }

        /*
         * Do configuration method (OF, ACPI) specific setup.
         *
         * XXX We can eliminate 99% of the platform device tree
         * XXX specific stuff here, but to do that we need a generic
         * XXX way to enumerate children of an arbitrary devhandle.
         */
        switch (devhandle_type(sc->sc_i2c_mux_devhandle)) {
        case DEVHANDLE_TYPE_OF:
                iicmux_attach_fdt(sc);
                break;
#if NACPICA > 0
        case DEVHANDLE_TYPE_ACPI:
                iicmux_attach_acpi(sc);
                break;
#endif
        default:
                aprint_error_dev(sc->sc_dev, "could not configure mux: "
                    "handle type 0x%08x not supported\n",
                    devhandle_type(sc->sc_i2c_mux_devhandle));
                break;
        }
}