/*-
 * Copyright (c) 2017 Kyle Evans <kevans@FreeBSD.org>
 * All rights reserved.
 *
 * 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.
 */

/*
 * This is a generic syscon driver, whose purpose is to provide access to
 * various unrelated bits packed in a single register space. It is usually used
 * as a fallback to more specific driver, but works well enough for simple
 * access.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/kernel.h>
#include <sys/module.h>
#include <sys/rman.h>

#include <machine/bus.h>

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

#include "syscon_if.h"

#define SYSCON_LOCK(_sc)		mtx_lock(&(_sc)->mtx)
#define	SYSCON_UNLOCK(_sc)		mtx_unlock(&(_sc)->mtx)
#define SYSCON_LOCK_INIT(_sc)		mtx_init(&(_sc)->mtx,		\
	    device_get_nameunit((_sc)->dev), "syscon", MTX_DEF)
#define SYSCON_LOCK_DESTROY(_sc)	mtx_destroy(&(_sc)->mtx);
#define SYSCON_ASSERT_LOCKED(_sc)	mtx_assert(&(_sc)->mtx, MA_OWNED);
#define SYSCON_ASSERT_UNLOCKED(_sc)	mtx_assert(&(_sc)->mtx, MA_NOTOWNED);

struct syscon_softc {
	device_t		dev;
	struct resource		*mem_res;
	struct mtx		mtx;
};

static struct ofw_compat_data compat_data[] = {
	{"syscon",	1},
	{NULL,		0}
};

static uint32_t
syscon_read_4(device_t dev, device_t consumer, bus_size_t offset)
{
	struct syscon_softc *sc;
	uint32_t val;

	sc = device_get_softc(dev);

	SYSCON_LOCK(sc);
	val = bus_read_4(sc->mem_res, offset);
	SYSCON_UNLOCK(sc);
	return (val);
}

static void
syscon_write_4(device_t dev, device_t consumer, bus_size_t offset, uint32_t val)
{
	struct syscon_softc *sc;

	sc = device_get_softc(dev);

	SYSCON_LOCK(sc);
	bus_write_4(sc->mem_res, offset, val);
	SYSCON_UNLOCK(sc);
}

static void
syscon_modify_4(device_t dev,  device_t consumer, bus_size_t offset,
    uint32_t clear_bits, uint32_t set_bits)
{
	struct syscon_softc *sc;
	uint32_t val;

	sc = device_get_softc(dev);

	SYSCON_LOCK(sc);
	val = bus_read_4(sc->mem_res, offset);
	val &= ~clear_bits;
	val |= set_bits;
	bus_write_4(sc->mem_res, offset, val);
	SYSCON_UNLOCK(sc);
}

static int
syscon_probe(device_t dev)
{

	if (!ofw_bus_status_okay(dev))
		return (ENXIO);
	if (ofw_bus_search_compatible(dev, compat_data)->ocd_data == 0)
		return (ENXIO);

	device_set_desc(dev, "syscon");
	return (BUS_PROBE_GENERIC);
}

static int
syscon_attach(device_t dev)
{
	struct syscon_softc *sc;
	int rid;
	phandle_t node;

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

	SYSCON_LOCK_INIT(sc);

	rid = 0;
	sc->mem_res = bus_alloc_resource_any(dev, SYS_RES_MEMORY, &rid,
	    RF_ACTIVE);
	if (sc->mem_res == NULL) {
		device_printf(dev, "Cannot allocate memory resource\n");
		return (ENXIO);
	}

	OF_device_register_xref(OF_xref_from_node(node), dev);

	return (0);
}

static int
syscon_detach(device_t dev)
{
	struct syscon_softc *sc;

	sc = device_get_softc(dev);

	OF_device_register_xref(OF_xref_from_device(dev), NULL);

	SYSCON_LOCK_DESTROY(sc);
	if (sc->mem_res != NULL)
		bus_release_resource(dev, SYS_RES_MEMORY, 0, sc->mem_res);
	return (0);
}

static device_method_t syscon_methods[] = {
	/* Device interface */
	DEVMETHOD(device_probe,		syscon_probe),
	DEVMETHOD(device_attach,	syscon_attach),
	DEVMETHOD(device_detach,	syscon_detach),

	/* Syscon interface */
	DEVMETHOD(syscon_read_4,	syscon_read_4),
	DEVMETHOD(syscon_write_4,	syscon_write_4),
	DEVMETHOD(syscon_modify_4,	syscon_modify_4),

	DEVMETHOD_END
};

DEFINE_CLASS_0(syscon, syscon_driver, syscon_methods,
    sizeof(struct syscon_softc));
static devclass_t syscon_devclass;
EARLY_DRIVER_MODULE(syscon, simplebus, syscon_driver, syscon_devclass, 0, 0,
    BUS_PASS_BUS + BUS_PASS_ORDER_LATE);
MODULE_VERSION(syscon, 1);