iic_gpiomux.c

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/*-
 * 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.
 */
 
/*
 * Driver for i2c bus muxes controlled by one or more gpio pins.
 *
 * This driver has #ifdef FDT sections in it, as if it supports both fdt and
 * hinted attachment, but there is currently no support for hinted attachment.
 */
 
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
 
#include "opt_platform.h"
 
#include <sys/param.h>
#include <sys/bus.h>
#include <sys/gpio.h>
#include <sys/kernel.h>
#include <sys/module.h>
#include <sys/systm.h>
 
#include <dev/gpio/gpiobusvar.h>
 
#include <dev/iicbus/iicbus.h>
#include <dev/iicbus/mux/iicmux.h>
 
#ifdef FDT
#include <dev/ofw/ofw_bus.h>
#include <dev/ofw/ofw_bus_subr.h>
#include <dev/ofw/openfirm.h>
 
static struct ofw_compat_data compat_data[] = {
        {"i2c-mux-gpio",  true},
        {NULL,            false}
};
OFWBUS_PNP_INFO(compat_data);
SIMPLEBUS_PNP_INFO(compat_data);
#endif /* FDT */
 
#include <dev/iicbus/iiconf.h>
#include "iicmux.h"
#include "iicmux_if.h"
 
struct gpiomux_softc {
        struct iicmux_softc mux;
        int     idleidx;
        int     numpins;
        gpio_pin_t pins[IICMUX_MAX_BUSES];
};
 
#define IDLE_NOOP       (-1) /* When asked to idle the bus, do nothing. */
 
static int
gpiomux_bus_select(device_t dev, int busidx, struct iic_reqbus_data *rd)
{
        struct gpiomux_softc *sc = device_get_softc(dev);
        int i;
 
        /*
         * The iicmux caller ensures busidx is between 0 and the number of buses
         * we passed to iicmux_init_softc(), no need for validation here.  The
         * bits in the index number are transcribed to the state of the pins,
         * except when we're asked to idle the bus.  In that case, we transcribe
         * sc->idleidx to the pins, unless that is IDLE_NOOP (leave the current
         * bus selected), in which case we just bail.
         */
        if (busidx == IICMUX_SELECT_IDLE) {
                if (sc->idleidx == IDLE_NOOP)
                        return (0);
                busidx = sc->idleidx;
        }
 
        for (i = 0; i < sc->numpins; ++i)
                gpio_pin_set_active(sc->pins[i], busidx & (1u << i));
 
        return (0);
}
 
static int
gpiomux_probe(device_t dev)
{
        int rv;
 
        rv = ENXIO;
 
#ifdef FDT
        if (ofw_bus_status_okay(dev) &&
            ofw_bus_search_compatible(dev, compat_data)->ocd_data)
                rv = BUS_PROBE_DEFAULT;
#endif
 
        device_set_desc(dev, "I2C GPIO Mux");
 
        return (rv);
}
 
static void
gpiomux_release_pins(struct gpiomux_softc *sc)
{
        int i;
 
        for (i = 0; i < sc->numpins; ++i)
                gpio_pin_release(sc->pins[i]);
}
 
static int
gpiomux_attach(device_t dev)
{
        struct gpiomux_softc *sc = device_get_softc(dev);
        ssize_t len;
        device_t busdev;
        int err, i, idlebits, numchannels;
        pcell_t propval;
        phandle_t node;
 
        node = ofw_bus_get_node(dev);
 
        /*
         * Locate the gpio pin(s) that control the mux hardware.  There can be
         * multiple pins, but there must be at least one.
         */
        for (i = 0; ; ++i) {
                err = gpio_pin_get_by_ofw_propidx(dev, node, "mux-gpios", i,
                    &sc->pins[i]);
                if (err != 0) {
                        break;
                }
        }
        sc->numpins = i;
        if (sc->numpins == 0) {
                device_printf(dev, "cannot acquire pins listed in mux-gpios\n");
                if (err == 0)
                        err = ENXIO;
                goto errexit;
        }
        numchannels = 1u << sc->numpins;
        if (numchannels > IICMUX_MAX_BUSES) {
                device_printf(dev, "too many mux-gpios pins for max %d buses\n",
                    IICMUX_MAX_BUSES);
                err = EINVAL;
                goto errexit;
        }
 
        /*
         * We don't have a parent/child relationship to the upstream bus, we
         * have to locate it via the i2c-parent property.  Explicitly tell the
         * user which upstream we're associated with, since the normal attach
         * message is going to mention only our actual parent.
         */
        len = OF_getencprop(node, "i2c-parent", &propval, sizeof(propval));
        if (len != sizeof(propval)) {
                device_printf(dev, "cannot obtain i2c-parent property\n");
                err = ENXIO;
                goto errexit;
        }
        busdev = OF_device_from_xref((phandle_t)propval);
        if (busdev == NULL) {
                device_printf(dev,
                    "cannot find device referenced by i2c-parent property\n");
                err = ENXIO;
                goto errexit;
        }
        device_printf(dev, "upstream bus is %s\n", device_get_nameunit(busdev));
 
        /*
         * If there is an idle-state property, that is the value we set the pins
         * to when the bus is idle, otherwise idling the bus is a no-op
         * (whichever bus was last accessed remains active).
         */
        len = OF_getencprop(node, "idle-state", &propval, sizeof(propval));
        if (len == sizeof(propval)) {
                if ((int)propval >= numchannels) {
                        device_printf(dev,
                            "idle-state property %d exceeds channel count\n",
                            propval);
                }
                sc->idleidx = (int)propval;
                idlebits = sc->idleidx;
        } else {
                sc->idleidx = IDLE_NOOP;
                idlebits = 0;
        }
 
        /* Preset the mux to the idle state to get things started. */
        for (i = 0; i < sc->numpins; ++i) {
                gpio_pin_setflags(sc->pins[i], GPIO_PIN_OUTPUT);
                gpio_pin_set_active(sc->pins[i], idlebits & (1u << i));
        }
 
        /* Init the core driver, have it add our child downstream buses. */
        if ((err = iicmux_attach(dev, busdev, numchannels)) == 0)
                bus_generic_attach(dev);
 
errexit:
 
        if (err != 0)
                gpiomux_release_pins(sc);
 
        return (err);
}
 
static int
gpiomux_detach(device_t dev)
{
        struct gpiomux_softc *sc = device_get_softc(dev);
        int err;
 
        if ((err = iicmux_detach(dev)) != 0)
                return (err);
 
        gpiomux_release_pins(sc);
 
        return (0);
}
 
static device_method_t gpiomux_methods[] = {
        /* device methods */
        DEVMETHOD(device_probe,                 gpiomux_probe),
        DEVMETHOD(device_attach,                gpiomux_attach),
        DEVMETHOD(device_detach,                gpiomux_detach),
 
        /* iicmux methods */
        DEVMETHOD(iicmux_bus_select,            gpiomux_bus_select),
 
        DEVMETHOD_END
};
 
static devclass_t gpiomux_devclass;
 
DEFINE_CLASS_1(iic_gpiomux, iic_gpiomux_driver, gpiomux_methods,
    sizeof(struct gpiomux_softc), iicmux_driver);
DRIVER_MODULE(iic_gpiomux, simplebus, iic_gpiomux_driver, gpiomux_devclass, 0, 0);
DRIVER_MODULE(iic_gpiomux, ofw_simplebus, iic_gpiomux_driver, gpiomux_devclass, 0, 0);
 
#ifdef FDT
DRIVER_MODULE(ofw_iicbus, iic_gpiomux, ofw_iicbus_driver, ofw_iicbus_devclass, 0, 0);
#else
DRIVER_MODULE(iicbus, iic_gpiomux, iicbus_driver, iicbus_devclass, 0, 0);
#endif
 
MODULE_DEPEND(iic_gpiomux, iicmux, 1, 1, 1);
MODULE_DEPEND(iic_gpiomux, iicbus, 1, 1, 1);