toim3232-sir.c

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/*********************************************************************
 *
 * Filename:      toim3232-sir.c
 * Version:       1.0
 * Description:   Implementation of dongles based on the Vishay/Temic
 *        TOIM3232 SIR Endec chipset. Currently only the
 *        IRWave IR320ST-2 is tested, although it should work
 *        with any TOIM3232 or TOIM4232 chipset based RS232
 *        dongle with minimal modification.
 *        Based heavily on the Tekram driver (tekram.c),
 *        with thanks to Dag Brattli and Martin Diehl.
 * Status:        Experimental.
 * Author:        David Basden <davidb-irda@rcpt.to>
 * Created at:    Thu Feb 09 23:47:32 2006
 *
 *     Copyright (c) 2006 David Basden.
 *     Copyright (c) 1998-1999 Dag Brattli,
 *     Copyright (c) 2002 Martin Diehl,
 *     All Rights Reserved.
 *
 *     This program is free software; you can redistribute it and/or
 *     modify it under the terms of the GNU General Public License as
 *     published by the Free Software Foundation; either version 2 of
 *     the License, or (at your option) any later version.
 *
 *     Neither Dag Brattli nor University of Tromsø admit liability nor
 *     provide warranty for any of this software. This material is
 *     provided "AS-IS" and at no charge.
 *
 ********************************************************************/

/*
 * This driver has currently only been tested on the IRWave IR320ST-2
 *
 * PROTOCOL:
 *
 * The protocol for talking to the TOIM3232 is quite easy, and is
 * designed to interface with RS232 with only level convertors. The
 * BR/~D line on the chip is brought high to signal 'command mode',
 * where a command byte is sent to select the baudrate of the RS232
 * interface and the pulse length of the IRDA output. When BR/~D
 * is brought low, the dongle then changes to the selected baudrate,
 * and the RS232 interface is used for data until BR/~D is brought
 * high again. The initial speed for the TOIMx323 after RESET is
 * 9600 baud.  The baudrate for command-mode is the last selected
 * baud-rate, or 9600 after a RESET.
 *
 * The  dongle I have (below) adds some extra hardware on the front end,
 * but this is mostly directed towards pariasitic power from the RS232
 * line rather than changing very much about how to communicate with
 * the TOIM3232.
 *
 * The protocol to talk to the TOIM4232 chipset seems to be almost
 * identical to the TOIM3232 (and the 4232 datasheet is more detailed)
 * so this code will probably work on that as well, although I haven't
 * tested it on that hardware.
 *
 * Target dongle variations that might be common:
 *
 * DTR and RTS function:
 *   The data sheet for the 4232 has a sample implementation that hooks the
 *   DTR and RTS lines to the RESET and BaudRate/~Data lines of the
 *   chip (through line-converters). Given both DTR and RTS would have to
 *   be held low in normal operation, and the TOIMx232 requires +5V to
 *   signal ground, most dongle designers would almost certainly choose
 *   an implementation that kept at least one of DTR or RTS high in
 *   normal operation to provide power to the dongle, but will likely
 *   vary between designs.
 *
 * User specified command bits:
 *  There are two user-controllable output lines from the TOIMx232 that
 *  can be set low or high by setting the appropriate bits in the
 *  high-nibble of the command byte (when setting speed and pulse length).
 *  These might be used to switch on and off added hardware or extra
 *  dongle features.
 *
 *
 * Target hardware: IRWave IR320ST-2
 *
 *  The IRWave IR320ST-2 is a simple dongle based on the Vishay/Temic
 *  TOIM3232 SIR Endec and the Vishay/Temic TFDS4500 SIR IRDA transceiver.
 *  It uses a hex inverter and some discrete components to buffer and
 *  line convert the RS232 down to 5V.
 *
 *  The dongle is powered through a voltage regulator, fed by a large
 *  capacitor. To switch the dongle on, DTR is brought high to charge
 *  the capacitor and drive the voltage regulator. DTR isn't associated
 *  with any control lines on the TOIM3232. Parisitic power is also taken
 *  from the RTS, TD and RD lines when brought high, but through resistors.
 *  When DTR is low, the circuit might lose power even with RTS high.
 *
 *  RTS is inverted and attached to the BR/~D input pin. When RTS
 *  is high, BR/~D is low, and the TOIM3232 is in the normal 'data' mode.
 *  RTS is brought low, BR/~D is high, and the TOIM3232 is in 'command
 *  mode'.
 *
 *  For some unknown reason, the RESET line isn't actually connected
 *  to anything. This means to reset the dongle to get it to a known
 *  state (9600 baud) you must drop DTR and RTS low, wait for the power
 *  capacitor to discharge, and then bring DTR (and RTS for data mode)
 *  high again, and wait for the capacitor to charge, the power supply
 *  to stabilise, and the oscillator clock to stabilise.
 *
 *  Fortunately, if the current baudrate is known, the chipset can
 *  easily change speed by entering command mode without having to
 *  reset the dongle first.
 *
 *  Major Components:
 *
 *  - Vishay/Temic TOIM3232 SIR Endec to change RS232 pulse timings
 *    to IRDA pulse timings
 *  - 3.6864MHz crystal to drive TOIM3232 clock oscillator
 *  - DM74lS04M Inverting Hex line buffer for RS232 input buffering
 *    and level conversion
 *  - PJ2951AC 150mA voltage regulator
 *  - Vishay/Temic TFDS4500 SIR IRDA front-end transceiver
 *
 */

#include <linux/module.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/sched.h>

#include <net/irda/irda.h>

#include "sir-dev.h"

static int toim3232delay = 150; /* default is 150 ms */
module_param(toim3232delay, int, 0);
MODULE_PARM_DESC(toim3232delay, "toim3232 dongle write complete delay");

#if 0
static int toim3232flipdtr = 0; /* default is DTR high to reset */
module_param(toim3232flipdtr, int, 0);
MODULE_PARM_DESC(toim3232flipdtr, "toim3232 dongle invert DTR (Reset)");

static int toim3232fliprts = 0; /* default is RTS high for baud change */
module_param(toim3232fliptrs, int, 0);
MODULE_PARM_DESC(toim3232fliprts, "toim3232 dongle invert RTS (BR/D)");
#endif

static int toim3232_open(struct sir_dev *);
static int toim3232_close(struct sir_dev *);
static int toim3232_change_speed(struct sir_dev *, unsigned);
static int toim3232_reset(struct sir_dev *);

#define TOIM3232_115200 0x00
#define TOIM3232_57600  0x01
#define TOIM3232_38400  0x02
#define TOIM3232_19200  0x03
#define TOIM3232_9600   0x06
#define TOIM3232_2400   0x0A

#define TOIM3232_PW     0x10 /* Pulse select bit */

static struct dongle_driver toim3232 = {
    .owner      = THIS_MODULE,
    .driver_name    = "Vishay TOIM3232",
    .type       = IRDA_TOIM3232_DONGLE,
    .open       = toim3232_open,
    .close      = toim3232_close,
    .reset      = toim3232_reset,
    .set_speed  = toim3232_change_speed,
};

static int __init toim3232_sir_init(void)
{
    if (toim3232delay < 1  ||  toim3232delay > 500)
        toim3232delay = 200;
    IRDA_DEBUG(1, "%s - using %d ms delay\n",
        toim3232.driver_name, toim3232delay);
    return irda_register_dongle(&toim3232);
}

static void __exit toim3232_sir_cleanup(void)
{
    irda_unregister_dongle(&toim3232);
}

static int toim3232_open(struct sir_dev *dev)
{
    struct qos_info *qos = &dev->qos;

    IRDA_DEBUG(2, "%s()\n", __func__);

    /* Pull the lines high to start with.
     *
     * For the IR320ST-2, we need to charge the main supply capacitor to
     * switch the device on. We keep DTR high throughout to do this.
     * When RTS, TD and RD are high, they will also trickle-charge the
     * cap. RTS is high for data transmission, and low for baud rate select.
     *  -- DGB
     */
    sirdev_set_dtr_rts(dev, TRUE, TRUE);

    /* The TOI3232 supports many speeds between 1200bps and 115000bps.
     * We really only care about those supported by the IRDA spec, but
     * 38400 seems to be implemented in many places */
    qos->baud_rate.bits &= IR_2400|IR_9600|IR_19200|IR_38400|IR_57600|IR_115200;

    /* From the tekram driver. Not sure what a reasonable value is -- DGB */
    qos->min_turn_time.bits = 0x01; /* Needs at least 10 ms */
    irda_qos_bits_to_value(qos);

    /* irda thread waits 50 msec for power settling */

    return 0;
}

static int toim3232_close(struct sir_dev *dev)
{
    IRDA_DEBUG(2, "%s()\n", __func__);

    /* Power off dongle */
    sirdev_set_dtr_rts(dev, FALSE, FALSE);

    return 0;
}

/*
 * Function toim3232change_speed (dev, state, speed)
 *
 *    Set the speed for the TOIM3232 based dongle. Warning, this
 *    function must be called with a process context!
 *
 *    Algorithm
 *    1. keep DTR high but clear RTS to bring into baud programming mode
 *    2. wait at least 7us to enter programming mode
 *    3. send control word to set baud rate and timing
 *    4. wait at least 1us
 *    5. bring RTS high to enter DATA mode (RS232 is passed through to transceiver)
 *    6. should take effect immediately (although probably worth waiting)
 */

#define TOIM3232_STATE_WAIT_SPEED   (SIRDEV_STATE_DONGLE_SPEED + 1)

static int toim3232_change_speed(struct sir_dev *dev, unsigned speed)
{
    unsigned state = dev->fsm.substate;
    unsigned delay = 0;
    u8 byte;
    static int ret = 0;

    IRDA_DEBUG(2, "%s()\n", __func__);

    switch(state) {
    case SIRDEV_STATE_DONGLE_SPEED:

        /* Figure out what we are going to send as a control byte */
        switch (speed) {
        case 2400:
            byte = TOIM3232_PW|TOIM3232_2400;
            break;
        default:
            speed = 9600;
            ret = -EINVAL;
            /* fall thru */
        case 9600:
            byte = TOIM3232_PW|TOIM3232_9600;
            break;
        case 19200:
            byte = TOIM3232_PW|TOIM3232_19200;
            break;
        case 38400:
            byte = TOIM3232_PW|TOIM3232_38400;
            break;
        case 57600:
            byte = TOIM3232_PW|TOIM3232_57600;
            break;
        case 115200:
            byte = TOIM3232_115200;
            break;
        }

        /* Set DTR, Clear RTS: Go into baud programming mode */
        sirdev_set_dtr_rts(dev, TRUE, FALSE);

        /* Wait at least 7us */
        udelay(14);

        /* Write control byte */
        sirdev_raw_write(dev, &byte, 1);

        dev->speed = speed;

        state = TOIM3232_STATE_WAIT_SPEED;
        delay = toim3232delay;
        break;

    case TOIM3232_STATE_WAIT_SPEED:
        /* Have transmitted control byte * Wait for 'at least 1us' */
        udelay(14);

        /* Set DTR, Set RTS: Go into normal data mode */
        sirdev_set_dtr_rts(dev, TRUE, TRUE);

        /* Wait (TODO: check this is needed) */
        udelay(50);
        break;

    default:
        printk(KERN_ERR "%s - undefined state %d\n", __func__, state);
        ret = -EINVAL;
        break;
    }

    dev->fsm.substate = state;
    return (delay > 0) ? delay : ret;
}

/*
 * Function toim3232reset (driver)
 *
 *      This function resets the toim3232 dongle. Warning, this function
 *      must be called with a process context!!
 *
 * What we should do is:
 *  0. Pull RESET high
 *  1. Wait for at least 7us
 *  2. Pull RESET low
 *  3. Wait for at least 7us
 *  4. Pull BR/~D high
 *  5. Wait for at least 7us
 *  6. Send control byte to set baud rate
 *  7. Wait at least 1us after stop bit
 *  8. Pull BR/~D low
 *  9. Should then be in data mode
 *
 * Because the IR320ST-2 doesn't have the RESET line connected for some reason,
 * we'll have to do something else.
 *
 * The default speed after a RESET is 9600, so lets try just bringing it up in
 * data mode after switching it off, waiting for the supply capacitor to
 * discharge, and then switch it back on. This isn't actually pulling RESET
 * high, but it seems to have the same effect.
 *
 * This behaviour will probably work on dongles that have the RESET line connected,
 * but if not, add a flag for the IR320ST-2, and implment the above-listed proper
 * behaviour.
 *
 * RTS is inverted and then fed to BR/~D, so to put it in programming mode, we
 * need to have pull RTS low
 */

static int toim3232_reset(struct sir_dev *dev)
{
    IRDA_DEBUG(2, "%s()\n", __func__);

    /* Switch off both DTR and RTS to switch off dongle */
    sirdev_set_dtr_rts(dev, FALSE, FALSE);

    /* Should sleep a while. This might be evil doing it this way.*/
    set_current_state(TASK_UNINTERRUPTIBLE);
    schedule_timeout(msecs_to_jiffies(50));

    /* Set DTR, Set RTS (data mode) */
    sirdev_set_dtr_rts(dev, TRUE, TRUE);

    /* Wait at least 10 ms for power to stabilize again */
    set_current_state(TASK_UNINTERRUPTIBLE);
    schedule_timeout(msecs_to_jiffies(10));

    /* Speed should now be 9600 */
    dev->speed = 9600;

    return 0;
}

MODULE_AUTHOR("David Basden <davidb-linux@rcpt.to>");
MODULE_DESCRIPTION("Vishay/Temic TOIM3232 based dongle driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("irda-dongle-12"); /* IRDA_TOIM3232_DONGLE */

module_init(toim3232_sir_init);
module_exit(toim3232_sir_cleanup);