xref: /src/sys/dev/i2c/i2cmux.c

/*	$NetBSD: i2cmux.c,v 1.1.2.2 2021/01/03 16:34:58 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.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: i2cmux.c,v 1.1.2.2 2021/01/03 16:34:58 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>

/*
 * 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;

 restart:
	for (child = OF_child(sc->sc_i2c_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 acutal parent
			 * of the i2c bus children.  Stash its phandle
			 * and restart the enumeration.
			 */
			sc->sc_i2c_mux_phandle = child;
			goto restart;
		}
		count++;
	}

	return count;
}

/* XXX iicbus_print() should be able to do this. */
static int
iicmux_print(void * const aux, const char * const pnp)
{
	i2c_tag_t const tag = aux;
	struct iicmux_bus * const bus = tag->ic_cookie;
	int rv;

	rv = iicbus_print(aux, pnp);
	aprint_normal(" bus %d", bus->busidx);

	return rv;
}

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

	bus->mux = sc;
	bus->busidx = busidx;
	bus->phandle = phandle;

	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_acquire_bus = iicmux_acquire_bus;
	bus->controller.ic_release_bus = iicmux_release_bus;
	bus->controller.ic_exec = iicmux_exec;

	fdtbus_register_i2c_controller(&bus->controller, bus->phandle);

	fdtbus_attach_i2cbus(sc->sc_dev, bus->phandle, &bus->controller,
	    iicmux_print);
}

void
iicmux_attach(struct iicmux_softc * const sc)
{

	/*
	 * We expect sc->sc_phandle, sc->sc_config, and sc->sc_i2c_parent
	 * to be initialized by the front-end.
	 */
	KASSERT(sc->sc_phandle > 0);
	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_phandle = sc->sc_phandle;

	/*
	 * 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;
	}

	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);

	int child, idx;
	for (child = OF_child(sc->sc_i2c_mux_phandle), idx = 0; child;
	     child = OF_peer(child), idx++) {
		KASSERT(idx < sc->sc_nbusses);
		iicmux_attach_bus(sc, child, idx);
	}
}