/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2022 Ruslan Bukin <br@bsdpad.com>
 *
 * This work was supported by Innovate UK project 105694, "Digital Security
 * by Design (DSbD) Technology Platform Prototype".
 *
 * 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/rman.h>
#include <sys/kernel.h>
#include <sys/module.h>

#include <machine/bus.h>

#include <dev/fdt/simplebus.h>
#include <dev/fdt/fdt_common.h>
#include <dev/ofw/ofw_bus_subr.h>

#include "mmio_sram_if.h"

#define dprintf(fmt, ...)

static struct resource_spec mmio_sram_spec[] = {
        { SYS_RES_MEMORY,       0,      RF_ACTIVE },
        { -1, 0 }
};

struct mmio_sram_softc {
        struct simplebus_softc  simplebus_sc;
        struct resource         *res[1];
        device_t                dev;
};

static int
mmio_sram_probe(device_t dev)
{

        if (!ofw_bus_is_compatible(dev, "mmio-sram"))
                return (ENXIO);

        if (!ofw_bus_status_okay(dev))
                return (ENXIO);

        device_set_desc(dev, "MMIO SRAM");

        return (BUS_PROBE_DEFAULT);
}

static int
mmio_sram_attach(device_t dev)
{
        struct mmio_sram_softc *sc;
        phandle_t node;

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

        if (bus_alloc_resources(dev, mmio_sram_spec, sc->res) != 0) {
                device_printf(dev, "Can't allocate resources for device.\n");
                return (ENXIO);
        }

        node = ofw_bus_get_node(dev);
        if (node == -1)
                return (ENXIO);

        simplebus_init(dev, node);

        /*
         * Allow devices to identify.
         */
        bus_identify_children(dev);

        /*
         * Now walk the OFW tree and attach top-level devices.
         */
        for (node = OF_child(node); node > 0; node = OF_peer(node))
                simplebus_add_device(dev, node, 0, NULL, -1, NULL);

        bus_attach_children(dev);
        return (0);
}

static int
mmio_sram_detach(device_t dev)
{
        struct mmio_sram_softc *sc;

        sc = device_get_softc(dev);

        bus_release_resources(dev, mmio_sram_spec, sc->res);

        return (0);
}

static uint8_t
mmio_sram_read_1(device_t dev, bus_size_t offset)
{
        struct mmio_sram_softc *sc;

        sc = device_get_softc(dev);

        dprintf("%s: reading from %lx\n", __func__, offset);

        return (bus_read_1(sc->res[0], offset));
}

static void
mmio_sram_write_1(device_t dev, bus_size_t offset, uint8_t val)
{
        struct mmio_sram_softc *sc;

        sc = device_get_softc(dev);

        dprintf("%s: writing to %lx val %x\n", __func__, offset, val);

        bus_write_1(sc->res[0], offset, val);
}

static device_method_t mmio_sram_methods[] = {
        /* Device Interface */
        DEVMETHOD(device_probe,         mmio_sram_probe),
        DEVMETHOD(device_attach,        mmio_sram_attach),
        DEVMETHOD(device_detach,        mmio_sram_detach),

        /* MMIO interface */
        DEVMETHOD(mmio_sram_read_1,     mmio_sram_read_1),
        DEVMETHOD(mmio_sram_write_1,    mmio_sram_write_1),
        DEVMETHOD_END
};

DEFINE_CLASS_1(mmio_sram, mmio_sram_driver, mmio_sram_methods,
    sizeof(struct mmio_sram_softc), simplebus_driver);

EARLY_DRIVER_MODULE(mmio_sram, simplebus, mmio_sram_driver, 0, 0,
    BUS_PASS_SUPPORTDEV + BUS_PASS_ORDER_MIDDLE);
MODULE_VERSION(mmio_sram, 1);