/*- * SPDX-License-Identifier: BSD-2-Clause * * Copyright (c) 1998, 2001 Nicolas Souchu * 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. */ #include /* * Generic I2C bit-banging code * * Example: * * iicbus * / \ * iicbb pcf * | \ * bti2c lpbb * * From Linux I2C generic interface * (c) 1998 Gerd Knorr * */ #include "opt_platform.h" #include #include #include #include #include #include #include #include #ifdef FDT #include #include #include #endif #include #include #include #include "iicbus_if.h" #include "iicbb_if.h" /* Based on the SMBus specification. */ #define DEFAULT_SCL_LOW_TIMEOUT (25 * 1000) struct iicbb_softc { device_t iicbus; u_int udelay; /* signal toggle delay in usec */ u_int io_latency; /* approximate pin toggling latency */ u_int scl_low_timeout; }; static int iicbb_attach(device_t); static void iicbb_child_detached(device_t, device_t); static int iicbb_detach(device_t); static int iicbb_print_child(device_t, device_t); static int iicbb_probe(device_t); static int iicbb_callback(device_t, int, caddr_t); static int iicbb_start(device_t, u_char, int); static int iicbb_repstart(device_t, u_char, int); static int iicbb_stop(device_t); static int iicbb_write(device_t, const char *, int, int *, int); static int iicbb_read(device_t, char *, int, int *, int, int); static int iicbb_reset(device_t, u_char, u_char, u_char *); static int iicbb_transfer(device_t dev, struct iic_msg *msgs, uint32_t nmsgs); static void iicbb_set_speed(struct iicbb_softc *sc, u_char); #ifdef FDT static phandle_t iicbb_get_node(device_t, device_t); #endif static device_method_t iicbb_methods[] = { /* device interface */ DEVMETHOD(device_probe, iicbb_probe), DEVMETHOD(device_attach, iicbb_attach), DEVMETHOD(device_detach, iicbb_detach), /* bus interface */ DEVMETHOD(bus_child_detached, iicbb_child_detached), DEVMETHOD(bus_print_child, iicbb_print_child), /* iicbus interface */ DEVMETHOD(iicbus_callback, iicbb_callback), DEVMETHOD(iicbus_start, iicbb_start), DEVMETHOD(iicbus_repeated_start, iicbb_repstart), DEVMETHOD(iicbus_stop, iicbb_stop), DEVMETHOD(iicbus_write, iicbb_write), DEVMETHOD(iicbus_read, iicbb_read), DEVMETHOD(iicbus_reset, iicbb_reset), DEVMETHOD(iicbus_transfer, iicbb_transfer), #ifdef FDT /* ofw_bus interface */ DEVMETHOD(ofw_bus_get_node, iicbb_get_node), #endif { 0, 0 } }; driver_t iicbb_driver = { "iicbb", iicbb_methods, sizeof(struct iicbb_softc), }; static int iicbb_probe(device_t dev) { device_set_desc(dev, "I2C bit-banging driver"); return (0); } static int iicbb_attach(device_t dev) { struct iicbb_softc *sc = (struct iicbb_softc *)device_get_softc(dev); sc->iicbus = device_add_child(dev, "iicbus", DEVICE_UNIT_ANY); if (!sc->iicbus) return (ENXIO); sc->scl_low_timeout = DEFAULT_SCL_LOW_TIMEOUT; SYSCTL_ADD_UINT(device_get_sysctl_ctx(dev), SYSCTL_CHILDREN(device_get_sysctl_tree(dev)), OID_AUTO, "delay", CTLFLAG_RD, &sc->udelay, 0, "Signal change delay controlled by bus frequency, microseconds"); SYSCTL_ADD_UINT(device_get_sysctl_ctx(dev), SYSCTL_CHILDREN(device_get_sysctl_tree(dev)), OID_AUTO, "scl_low_timeout", CTLFLAG_RWTUN, &sc->scl_low_timeout, 0, "SCL low timeout, microseconds"); SYSCTL_ADD_UINT(device_get_sysctl_ctx(dev), SYSCTL_CHILDREN(device_get_sysctl_tree(dev)), OID_AUTO, "io_latency", CTLFLAG_RWTUN, &sc->io_latency, 0, "Estimate of pin toggling latency, microseconds"); bus_generic_attach(dev); return (0); } static int iicbb_detach(device_t dev) { bus_generic_detach(dev); device_delete_children(dev); return (0); } #ifdef FDT static phandle_t iicbb_get_node(device_t bus, device_t dev) { /* We only have one child, the I2C bus, which needs our own node. */ return (ofw_bus_get_node(bus)); } #endif static void iicbb_child_detached( device_t dev, device_t child ) { struct iicbb_softc *sc = (struct iicbb_softc *)device_get_softc(dev); if (child == sc->iicbus) sc->iicbus = NULL; } static int iicbb_print_child(device_t bus, device_t dev) { int error; int retval = 0; u_char oldaddr; retval += bus_print_child_header(bus, dev); /* retrieve the interface I2C address */ error = IICBB_RESET(device_get_parent(bus), IIC_FASTEST, 0, &oldaddr); if (error == IIC_ENOADDR) { retval += printf(" on %s master-only\n", device_get_nameunit(bus)); } else { /* restore the address */ IICBB_RESET(device_get_parent(bus), IIC_FASTEST, oldaddr, NULL); retval += printf(" on %s addr 0x%x\n", device_get_nameunit(bus), oldaddr & 0xff); } return (retval); } #define IICBB_DEBUG #ifdef IICBB_DEBUG static int i2c_debug = 0; SYSCTL_DECL(_hw_i2c); SYSCTL_INT(_hw_i2c, OID_AUTO, iicbb_debug, CTLFLAG_RWTUN, &i2c_debug, 0, "Enable i2c bit-banging driver debug"); #define I2C_DEBUG(x) do { \ if (i2c_debug) (x); \ } while (0) #else #define I2C_DEBUG(x) #endif #define I2C_GETSDA(dev) (IICBB_GETSDA(device_get_parent(dev))) #define I2C_SETSDA(dev, x) (IICBB_SETSDA(device_get_parent(dev), x)) #define I2C_GETSCL(dev) (IICBB_GETSCL(device_get_parent(dev))) #define I2C_SETSCL(dev, x) (IICBB_SETSCL(device_get_parent(dev), x)) static int iicbb_waitforscl(device_t dev) { struct iicbb_softc *sc = device_get_softc(dev); sbintime_t fast_timeout; sbintime_t now, timeout; /* Spin for up to 1 ms, then switch to pause. */ now = sbinuptime(); fast_timeout = now + SBT_1MS; timeout = now + sc->scl_low_timeout * SBT_1US; do { if (I2C_GETSCL(dev)) return (0); cpu_spinwait(); now = sbinuptime(); } while (now < fast_timeout); do { I2C_DEBUG(printf(".")); pause_sbt("iicbb-scl-low", SBT_1MS, 0, C_PREL(2)); if (I2C_GETSCL(dev)) return (0); now = sbinuptime(); } while (now < timeout); I2C_DEBUG(printf("*")); return (IIC_ETIMEOUT); } /* Start the high phase of the clock. */ static int iicbb_clockin(device_t dev, int sda) { /* * Precondition: SCL is low. * Action: * - set SDA to the value; * - release SCL and wait until it's high. * The caller is responsible for keeping SCL high for udelay. * * There should be a data set-up time, 250 ns minimum, between setting * SDA and raising SCL. It's expected that the I/O access latency will * naturally provide that delay. */ I2C_SETSDA(dev, sda); I2C_SETSCL(dev, 1); return (iicbb_waitforscl(dev)); } /* * End the high phase of the clock and wait out the low phase * as nothing interesting happens during it anyway. */ static void iicbb_clockout(device_t dev) { struct iicbb_softc *sc = device_get_softc(dev); /* * Precondition: SCL is high. * Action: * - pull SCL low and hold for udelay. */ I2C_SETSCL(dev, 0); DELAY(sc->udelay); } static int iicbb_sendbit(device_t dev, int bit) { struct iicbb_softc *sc = device_get_softc(dev); int err; err = iicbb_clockin(dev, bit); if (err != 0) return (err); DELAY(sc->udelay); iicbb_clockout(dev); return (0); } /* * Waiting for ACKNOWLEDGE. * * When a chip is being addressed or has received data it will issue an * ACKNOWLEDGE pulse. Therefore the MASTER must release the DATA line * (set it to high level) and then release the CLOCK line. * Now it must wait for the SLAVE to pull the DATA line low. * Actually on the bus this looks like a START condition so nothing happens * because of the fact that the IC's that have not been addressed are doing * nothing. * * When the SLAVE has pulled this line low the MASTER will take the CLOCK * line low and then the SLAVE will release the SDA (data) line. */ static int iicbb_getack(device_t dev) { struct iicbb_softc *sc = device_get_softc(dev); int noack, err; int t; /* Release SDA so that the slave can drive it. */ err = iicbb_clockin(dev, 1); if (err != 0) { I2C_DEBUG(printf("! ")); return (err); } /* Sample SDA until ACK (low) or udelay runs out. */ for (t = 0; t < sc->udelay; t++) { noack = I2C_GETSDA(dev); if (!noack) break; DELAY(1); } DELAY(sc->udelay - t); iicbb_clockout(dev); I2C_DEBUG(printf("%c ", noack ? '-' : '+')); return (noack ? IIC_ENOACK : 0); } static int iicbb_sendbyte(device_t dev, uint8_t data) { int err, i; for (i = 7; i >= 0; i--) { err = iicbb_sendbit(dev, (data & (1 << i)) != 0); if (err != 0) { I2C_DEBUG(printf("w!")); return (err); } } I2C_DEBUG(printf("w%02x", data)); return (0); } static int iicbb_readbyte(device_t dev, bool last, uint8_t *data) { struct iicbb_softc *sc = device_get_softc(dev); int i, err; /* * Release SDA so that the slave can drive it. * We do not use iicbb_clockin() here because we need to release SDA * only once and then we just pulse the SCL. */ *data = 0; I2C_SETSDA(dev, 1); for (i = 7; i >= 0; i--) { I2C_SETSCL(dev, 1); err = iicbb_waitforscl(dev); if (err != 0) { I2C_DEBUG(printf("r! ")); return (err); } DELAY((sc->udelay + 1) / 2); if (I2C_GETSDA(dev)) *data |= 1 << i; DELAY((sc->udelay + 1) / 2); iicbb_clockout(dev); } /* * Send master->slave ACK (low) for more data, * NoACK (high) otherwise. */ iicbb_sendbit(dev, last); I2C_DEBUG(printf("r%02x%c ", *data, last ? '-' : '+')); return (0); } static int iicbb_callback(device_t dev, int index, caddr_t data) { return (IICBB_CALLBACK(device_get_parent(dev), index, data)); } static int iicbb_reset(device_t dev, u_char speed, u_char addr, u_char *oldaddr) { iicbb_set_speed(device_get_softc(dev), speed); return (IICBB_RESET(device_get_parent(dev), speed, addr, oldaddr)); } static int iicbb_start_impl(device_t dev, u_char slave, bool repstart) { struct iicbb_softc *sc = device_get_softc(dev); int error; if (!repstart) { I2C_DEBUG(printf("<<")); /* SCL must be high on the idle bus. */ if (iicbb_waitforscl(dev) != 0) { I2C_DEBUG(printf("C!\n")); return (IIC_EBUSERR); } } else { I2C_DEBUG(printf("<")); error = iicbb_clockin(dev, 1); if (error != 0) return (error); /* SDA will go low in the middle of the SCL high phase. */ DELAY((sc->udelay + 1) / 2); } /* * SDA must be high after the earlier stop condition or the end * of Ack/NoAck pulse. */ if (!I2C_GETSDA(dev)) { I2C_DEBUG(printf("D!\n")); return (IIC_EBUSERR); } /* Start: SDA high->low. */ I2C_SETSDA(dev, 0); /* Wait the second half of the SCL high phase. */ DELAY((sc->udelay + 1) / 2); /* Pull SCL low to keep the bus reserved. */ iicbb_clockout(dev); /* send address */ error = iicbb_sendbyte(dev, slave); /* check for ack */ if (error == 0) error = iicbb_getack(dev); if (error != 0) (void)iicbb_stop(dev); return (error); } /* NB: the timeout is ignored. */ static int iicbb_start(device_t dev, u_char slave, int timeout) { return (iicbb_start_impl(dev, slave, false)); } /* NB: the timeout is ignored. */ static int iicbb_repstart(device_t dev, u_char slave, int timeout) { return (iicbb_start_impl(dev, slave, true)); } static int iicbb_stop(device_t dev) { struct iicbb_softc *sc = device_get_softc(dev); int err = 0; /* * Stop: SDA goes from low to high in the middle of the SCL high phase. */ err = iicbb_clockin(dev, 0); if (err != 0) return (err); DELAY((sc->udelay + 1) / 2); I2C_SETSDA(dev, 1); DELAY((sc->udelay + 1) / 2); I2C_DEBUG(printf("%s>>", err != 0 ? "!" : "")); I2C_DEBUG(printf("\n")); return (err); } /* NB: the timeout is ignored. */ static int iicbb_write(device_t dev, const char *buf, int len, int *sent, int timeout) { int bytes, error = 0; bytes = 0; while (len > 0) { /* send byte */ iicbb_sendbyte(dev, (uint8_t)*buf++); /* check for ack */ error = iicbb_getack(dev); if (error != 0) break; bytes++; len--; } *sent = bytes; return (error); } /* NB: whatever delay is, it's ignored. */ static int iicbb_read(device_t dev, char *buf, int len, int *read, int last, int delay) { int bytes = 0; int err = 0; while (len > 0) { err = iicbb_readbyte(dev, (len == 1) ? last : 0, (uint8_t *)buf); if (err != 0) break; buf++; bytes++; len--; } *read = bytes; return (err); } static int iicbb_transfer(device_t dev, struct iic_msg *msgs, uint32_t nmsgs) { int error; error = IICBB_PRE_XFER(device_get_parent(dev)); if (error) return (error); error = iicbus_transfer_gen(dev, msgs, nmsgs); IICBB_POST_XFER(device_get_parent(dev)); return (error); } static void iicbb_set_speed(struct iicbb_softc *sc, u_char speed) { u_int busfreq; int period; /* * udelay is half a period, the clock is held high or low for this long. */ busfreq = IICBUS_GET_FREQUENCY(sc->iicbus, speed); period = 1000000 / 2 / busfreq; /* Hz -> uS */ period -= sc->io_latency; sc->udelay = MAX(period, 1); } DRIVER_MODULE(iicbus, iicbb, iicbus_driver, 0, 0); MODULE_DEPEND(iicbb, iicbus, IICBUS_MINVER, IICBUS_PREFVER, IICBUS_MAXVER); MODULE_VERSION(iicbb, IICBB_MODVER);