FreeBSD/Linux Kernel Cross Reference
sys/dev/iicbus/iicbb.c

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * 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 <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    /*
     * Generic I2C bit-banging code
     *
     * Example:
     *
     *      iicbus
     *       /  \ 
     *    iicbb pcf
     *     |  \
     *   bti2c lpbb
     *
     * From Linux I2C generic interface
     * (c) 1998 Gerd Knorr <kraxel@cs.tu-berlin.de>
     *
     */
    
    #include "opt_platform.h"
    
    #include <sys/param.h>
    #include <sys/kernel.h>
    #include <sys/systm.h>
    #include <sys/module.h>
    #include <sys/bus.h>
    #include <sys/sysctl.h>
    #include <sys/uio.h>
    
    #ifdef FDT
    #include <dev/ofw/ofw_bus.h>
    #include <dev/ofw/ofw_bus_subr.h>
    #include <dev/fdt/fdt_common.h>
    #endif
    
    #include <dev/iicbus/iiconf.h>
    #include <dev/iicbus/iicbus.h>
    
    #include <dev/smbus/smbconf.h>
    
    #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", -1);
           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);
                   now = sbinuptime();
           } while (now < fast_timeout);
           do {
                   I2C_DEBUG(printf("."));
                   pause_sbt("iicbb-scl-low", SBT_1MS, C_PREL(8), 0);
                   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);

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