ch341.c

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/*
 * Copyright 2007, Frank A Kingswood <[email protected]>
 * Copyright 2007, Werner Cornelius <[email protected]>
 * Copyright 2009, Boris Hajduk <[email protected]>
 *
 * ch341.c implements a serial port driver for the Winchiphead CH341.
 *
 * The CH341 device can be used to implement an RS232 asynchronous
 * serial port, an IEEE-1284 parallel printer port or a memory-like
 * interface. In all cases the CH341 supports an I2C interface as well.
 * This driver only supports the asynchronous serial interface.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 as published by the Free Software Foundation.
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/tty.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/usb.h>
#include <linux/usb/serial.h>
#include <linux/serial.h>
#include <asm/unaligned.h>

#define DEFAULT_BAUD_RATE 9600
#define DEFAULT_TIMEOUT   1000

/* flags for IO-Bits */
#define CH341_BIT_RTS (1 << 6)
#define CH341_BIT_DTR (1 << 5)

/******************************/
/* interrupt pipe definitions */
/******************************/
/* always 4 interrupt bytes */
/* first irq byte normally 0x08 */
/* second irq byte base 0x7d + below */
/* third irq byte base 0x94 + below */
/* fourth irq byte normally 0xee */

/* second interrupt byte */
#define CH341_MULT_STAT 0x04 /* multiple status since last interrupt event */

/* status returned in third interrupt answer byte, inverted in data
   from irq */
#define CH341_BIT_CTS 0x01
#define CH341_BIT_DSR 0x02
#define CH341_BIT_RI  0x04
#define CH341_BIT_DCD 0x08
#define CH341_BITS_MODEM_STAT 0x0f /* all bits */

/*******************************/
/* baudrate calculation factor */
/*******************************/
#define CH341_BAUDBASE_FACTOR 1532620800
#define CH341_BAUDBASE_DIVMAX 3

/* Break support - the information used to implement this was gleaned from
 * the Net/FreeBSD uchcom.c driver by Takanori Watanabe.  Domo arigato.
 */

#define CH341_REQ_WRITE_REG    0x9A
#define CH341_REQ_READ_REG     0x95
#define CH341_REG_BREAK1       0x05
#define CH341_REG_BREAK2       0x18
#define CH341_NBREAK_BITS_REG1 0x01
#define CH341_NBREAK_BITS_REG2 0x40


static const struct usb_device_id id_table[] = {
    { USB_DEVICE(0x4348, 0x5523) },
    { USB_DEVICE(0x1a86, 0x7523) },
    { USB_DEVICE(0x1a86, 0x5523) },
    { },
};
MODULE_DEVICE_TABLE(usb, id_table);

struct ch341_private {
    spinlock_t lock; /* access lock */
    wait_queue_head_t delta_msr_wait; /* wait queue for modem status */
    unsigned baud_rate; /* set baud rate */
    u8 line_control; /* set line control value RTS/DTR */
    u8 line_status; /* active status of modem control inputs */
    u8 multi_status_change; /* status changed multiple since last call */
};

static int ch341_control_out(struct usb_device *dev, u8 request,
                 u16 value, u16 index)
{
    int r;

    dev_dbg(&dev->dev, "ch341_control_out(%02x,%02x,%04x,%04x)\n",
        USB_DIR_OUT|0x40, (int)request, (int)value, (int)index);

    r = usb_control_msg(dev, usb_sndctrlpipe(dev, 0), request,
                USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
                value, index, NULL, 0, DEFAULT_TIMEOUT);

    return r;
}

static int ch341_control_in(struct usb_device *dev,
                u8 request, u16 value, u16 index,
                char *buf, unsigned bufsize)
{
    int r;

    dev_dbg(&dev->dev, "ch341_control_in(%02x,%02x,%04x,%04x,%p,%u)\n",
        USB_DIR_IN|0x40, (int)request, (int)value, (int)index, buf,
        (int)bufsize);

    r = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0), request,
                USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
                value, index, buf, bufsize, DEFAULT_TIMEOUT);
    return r;
}

static int ch341_set_baudrate(struct usb_device *dev,
                  struct ch341_private *priv)
{
    short a, b;
    int r;
    unsigned long factor;
    short divisor;

    if (!priv->baud_rate)
        return -EINVAL;
    factor = (CH341_BAUDBASE_FACTOR / priv->baud_rate);
    divisor = CH341_BAUDBASE_DIVMAX;

    while ((factor > 0xfff0) && divisor) {
        factor >>= 3;
        divisor--;
    }

    if (factor > 0xfff0)
        return -EINVAL;

    factor = 0x10000 - factor;
    a = (factor & 0xff00) | divisor;
    b = factor & 0xff;

    r = ch341_control_out(dev, 0x9a, 0x1312, a);
    if (!r)
        r = ch341_control_out(dev, 0x9a, 0x0f2c, b);

    return r;
}

static int ch341_set_handshake(struct usb_device *dev, u8 control)
{
    return ch341_control_out(dev, 0xa4, ~control, 0);
}

static int ch341_get_status(struct usb_device *dev, struct ch341_private *priv)
{
    char *buffer;
    int r;
    const unsigned size = 8;
    unsigned long flags;

    buffer = kmalloc(size, GFP_KERNEL);
    if (!buffer)
        return -ENOMEM;

    r = ch341_control_in(dev, 0x95, 0x0706, 0, buffer, size);
    if (r < 0)
        goto out;

    /* setup the private status if available */
    if (r == 2) {
        r = 0;
        spin_lock_irqsave(&priv->lock, flags);
        priv->line_status = (~(*buffer)) & CH341_BITS_MODEM_STAT;
        priv->multi_status_change = 0;
        spin_unlock_irqrestore(&priv->lock, flags);
    } else
        r = -EPROTO;

out:    kfree(buffer);
    return r;
}

/* -------------------------------------------------------------------------- */

static int ch341_configure(struct usb_device *dev, struct ch341_private *priv)
{
    char *buffer;
    int r;
    const unsigned size = 8;

    buffer = kmalloc(size, GFP_KERNEL);
    if (!buffer)
        return -ENOMEM;

    /* expect two bytes 0x27 0x00 */
    r = ch341_control_in(dev, 0x5f, 0, 0, buffer, size);
    if (r < 0)
        goto out;

    r = ch341_control_out(dev, 0xa1, 0, 0);
    if (r < 0)
        goto out;

    r = ch341_set_baudrate(dev, priv);
    if (r < 0)
        goto out;

    /* expect two bytes 0x56 0x00 */
    r = ch341_control_in(dev, 0x95, 0x2518, 0, buffer, size);
    if (r < 0)
        goto out;

    r = ch341_control_out(dev, 0x9a, 0x2518, 0x0050);
    if (r < 0)
        goto out;

    /* expect 0xff 0xee */
    r = ch341_get_status(dev, priv);
    if (r < 0)
        goto out;

    r = ch341_control_out(dev, 0xa1, 0x501f, 0xd90a);
    if (r < 0)
        goto out;

    r = ch341_set_baudrate(dev, priv);
    if (r < 0)
        goto out;

    r = ch341_set_handshake(dev, priv->line_control);
    if (r < 0)
        goto out;

    /* expect 0x9f 0xee */
    r = ch341_get_status(dev, priv);

out:    kfree(buffer);
    return r;
}

static int ch341_port_probe(struct usb_serial_port *port)
{
    struct ch341_private *priv;
    int r;

    priv = kzalloc(sizeof(struct ch341_private), GFP_KERNEL);
    if (!priv)
        return -ENOMEM;

    spin_lock_init(&priv->lock);
    init_waitqueue_head(&priv->delta_msr_wait);
    priv->baud_rate = DEFAULT_BAUD_RATE;
    priv->line_control = CH341_BIT_RTS | CH341_BIT_DTR;

    r = ch341_configure(port->serial->dev, priv);
    if (r < 0)
        goto error;

    usb_set_serial_port_data(port, priv);
    return 0;

error:  kfree(priv);
    return r;
}

static int ch341_port_remove(struct usb_serial_port *port)
{
    struct ch341_private *priv;

    priv = usb_get_serial_port_data(port);
    kfree(priv);

    return 0;
}

static int ch341_carrier_raised(struct usb_serial_port *port)
{
    struct ch341_private *priv = usb_get_serial_port_data(port);
    if (priv->line_status & CH341_BIT_DCD)
        return 1;
    return 0;
}

static void ch341_dtr_rts(struct usb_serial_port *port, int on)
{
    struct ch341_private *priv = usb_get_serial_port_data(port);
    unsigned long flags;

    /* drop DTR and RTS */
    spin_lock_irqsave(&priv->lock, flags);
    if (on)
        priv->line_control |= CH341_BIT_RTS | CH341_BIT_DTR;
    else
        priv->line_control &= ~(CH341_BIT_RTS | CH341_BIT_DTR);
    spin_unlock_irqrestore(&priv->lock, flags);
    ch341_set_handshake(port->serial->dev, priv->line_control);
    wake_up_interruptible(&priv->delta_msr_wait);
}

static void ch341_close(struct usb_serial_port *port)
{
    usb_serial_generic_close(port);
    usb_kill_urb(port->interrupt_in_urb);
}


/* open this device, set default parameters */
static int ch341_open(struct tty_struct *tty, struct usb_serial_port *port)
{
    struct usb_serial *serial = port->serial;
    struct ch341_private *priv = usb_get_serial_port_data(port);
    int r;

    priv->baud_rate = DEFAULT_BAUD_RATE;

    r = ch341_configure(serial->dev, priv);
    if (r)
        goto out;

    r = ch341_set_handshake(serial->dev, priv->line_control);
    if (r)
        goto out;

    r = ch341_set_baudrate(serial->dev, priv);
    if (r)
        goto out;

    dev_dbg(&port->dev, "%s - submitting interrupt urb", __func__);
    r = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
    if (r) {
        dev_err(&port->dev, "%s - failed submitting interrupt urb,"
            " error %d\n", __func__, r);
        ch341_close(port);
        goto out;
    }

    r = usb_serial_generic_open(tty, port);

out:    return r;
}

/* Old_termios contains the original termios settings and
 * tty->termios contains the new setting to be used.
 */
static void ch341_set_termios(struct tty_struct *tty,
        struct usb_serial_port *port, struct ktermios *old_termios)
{
    struct ch341_private *priv = usb_get_serial_port_data(port);
    unsigned baud_rate;
    unsigned long flags;

    baud_rate = tty_get_baud_rate(tty);

    priv->baud_rate = baud_rate;

    if (baud_rate) {
        spin_lock_irqsave(&priv->lock, flags);
        priv->line_control |= (CH341_BIT_DTR | CH341_BIT_RTS);
        spin_unlock_irqrestore(&priv->lock, flags);
        ch341_set_baudrate(port->serial->dev, priv);
    } else {
        spin_lock_irqsave(&priv->lock, flags);
        priv->line_control &= ~(CH341_BIT_DTR | CH341_BIT_RTS);
        spin_unlock_irqrestore(&priv->lock, flags);
    }

    ch341_set_handshake(port->serial->dev, priv->line_control);

    /* Unimplemented:
     * (cflag & CSIZE) : data bits [5, 8]
     * (cflag & PARENB) : parity {NONE, EVEN, ODD}
     * (cflag & CSTOPB) : stop bits [1, 2]
     */
}

static void ch341_break_ctl(struct tty_struct *tty, int break_state)
{
    const uint16_t ch341_break_reg =
        CH341_REG_BREAK1 | ((uint16_t) CH341_REG_BREAK2 << 8);
    struct usb_serial_port *port = tty->driver_data;
    int r;
    uint16_t reg_contents;
    uint8_t *break_reg;

    break_reg = kmalloc(2, GFP_KERNEL);
    if (!break_reg) {
        dev_err(&port->dev, "%s - kmalloc failed\n", __func__);
        return;
    }

    r = ch341_control_in(port->serial->dev, CH341_REQ_READ_REG,
            ch341_break_reg, 0, break_reg, 2);
    if (r < 0) {
        dev_err(&port->dev, "%s - USB control read error (%d)\n",
                __func__, r);
        goto out;
    }
    dev_dbg(&port->dev, "%s - initial ch341 break register contents - reg1: %x, reg2: %x\n",
        __func__, break_reg[0], break_reg[1]);
    if (break_state != 0) {
        dev_dbg(&port->dev, "%s - Enter break state requested\n", __func__);
        break_reg[0] &= ~CH341_NBREAK_BITS_REG1;
        break_reg[1] &= ~CH341_NBREAK_BITS_REG2;
    } else {
        dev_dbg(&port->dev, "%s - Leave break state requested\n", __func__);
        break_reg[0] |= CH341_NBREAK_BITS_REG1;
        break_reg[1] |= CH341_NBREAK_BITS_REG2;
    }
    dev_dbg(&port->dev, "%s - New ch341 break register contents - reg1: %x, reg2: %x\n",
        __func__, break_reg[0], break_reg[1]);
    reg_contents = get_unaligned_le16(break_reg);
    r = ch341_control_out(port->serial->dev, CH341_REQ_WRITE_REG,
            ch341_break_reg, reg_contents);
    if (r < 0)
        dev_err(&port->dev, "%s - USB control write error (%d)\n",
                __func__, r);
out:
    kfree(break_reg);
}

static int ch341_tiocmset(struct tty_struct *tty,
              unsigned int set, unsigned int clear)
{
    struct usb_serial_port *port = tty->driver_data;
    struct ch341_private *priv = usb_get_serial_port_data(port);
    unsigned long flags;
    u8 control;

    spin_lock_irqsave(&priv->lock, flags);
    if (set & TIOCM_RTS)
        priv->line_control |= CH341_BIT_RTS;
    if (set & TIOCM_DTR)
        priv->line_control |= CH341_BIT_DTR;
    if (clear & TIOCM_RTS)
        priv->line_control &= ~CH341_BIT_RTS;
    if (clear & TIOCM_DTR)
        priv->line_control &= ~CH341_BIT_DTR;
    control = priv->line_control;
    spin_unlock_irqrestore(&priv->lock, flags);

    return ch341_set_handshake(port->serial->dev, control);
}

static void ch341_read_int_callback(struct urb *urb)
{
    struct usb_serial_port *port = (struct usb_serial_port *) urb->context;
    unsigned char *data = urb->transfer_buffer;
    unsigned int actual_length = urb->actual_length;
    int status;

    switch (urb->status) {
    case 0:
        /* success */
        break;
    case -ECONNRESET:
    case -ENOENT:
    case -ESHUTDOWN:
        /* this urb is terminated, clean up */
        dev_dbg(&urb->dev->dev, "%s - urb shutting down with status: %d\n",
            __func__, urb->status);
        return;
    default:
        dev_dbg(&urb->dev->dev, "%s - nonzero urb status received: %d\n",
            __func__, urb->status);
        goto exit;
    }

    usb_serial_debug_data(&port->dev, __func__,
                  urb->actual_length, urb->transfer_buffer);

    if (actual_length >= 4) {
        struct ch341_private *priv = usb_get_serial_port_data(port);
        unsigned long flags;
        u8 prev_line_status = priv->line_status;

        spin_lock_irqsave(&priv->lock, flags);
        priv->line_status = (~(data[2])) & CH341_BITS_MODEM_STAT;
        if ((data[1] & CH341_MULT_STAT))
            priv->multi_status_change = 1;
        spin_unlock_irqrestore(&priv->lock, flags);

        if ((priv->line_status ^ prev_line_status) & CH341_BIT_DCD) {
            struct tty_struct *tty = tty_port_tty_get(&port->port);
            if (tty)
                usb_serial_handle_dcd_change(port, tty,
                        priv->line_status & CH341_BIT_DCD);
            tty_kref_put(tty);
        }

        wake_up_interruptible(&priv->delta_msr_wait);
    }

exit:
    status = usb_submit_urb(urb, GFP_ATOMIC);
    if (status)
        dev_err(&urb->dev->dev,
            "%s - usb_submit_urb failed with result %d\n",
            __func__, status);
}

static int wait_modem_info(struct usb_serial_port *port, unsigned int arg)
{
    struct ch341_private *priv = usb_get_serial_port_data(port);
    unsigned long flags;
    u8 prevstatus;
    u8 status;
    u8 changed;
    u8 multi_change = 0;

    spin_lock_irqsave(&priv->lock, flags);
    prevstatus = priv->line_status;
    priv->multi_status_change = 0;
    spin_unlock_irqrestore(&priv->lock, flags);

    while (!multi_change) {
        interruptible_sleep_on(&priv->delta_msr_wait);
        /* see if a signal did it */
        if (signal_pending(current))
            return -ERESTARTSYS;

        spin_lock_irqsave(&priv->lock, flags);
        status = priv->line_status;
        multi_change = priv->multi_status_change;
        spin_unlock_irqrestore(&priv->lock, flags);

        changed = prevstatus ^ status;

        if (((arg & TIOCM_RNG) && (changed & CH341_BIT_RI)) ||
            ((arg & TIOCM_DSR) && (changed & CH341_BIT_DSR)) ||
            ((arg & TIOCM_CD)  && (changed & CH341_BIT_DCD)) ||
            ((arg & TIOCM_CTS) && (changed & CH341_BIT_CTS))) {
            return 0;
        }
        prevstatus = status;
    }

    return 0;
}

static int ch341_ioctl(struct tty_struct *tty,
            unsigned int cmd, unsigned long arg)
{
    struct usb_serial_port *port = tty->driver_data;

    dev_dbg(&port->dev, "%s (%d) cmd = 0x%04x\n", __func__, port->number, cmd);

    switch (cmd) {
    case TIOCMIWAIT:
        dev_dbg(&port->dev, "%s (%d) TIOCMIWAIT\n", __func__,  port->number);
        return wait_modem_info(port, arg);

    default:
        dev_dbg(&port->dev, "%s not supported = 0x%04x\n", __func__, cmd);
        break;
    }

    return -ENOIOCTLCMD;
}

static int ch341_tiocmget(struct tty_struct *tty)
{
    struct usb_serial_port *port = tty->driver_data;
    struct ch341_private *priv = usb_get_serial_port_data(port);
    unsigned long flags;
    u8 mcr;
    u8 status;
    unsigned int result;

    spin_lock_irqsave(&priv->lock, flags);
    mcr = priv->line_control;
    status = priv->line_status;
    spin_unlock_irqrestore(&priv->lock, flags);

    result = ((mcr & CH341_BIT_DTR)     ? TIOCM_DTR : 0)
          | ((mcr & CH341_BIT_RTS)  ? TIOCM_RTS : 0)
          | ((status & CH341_BIT_CTS)   ? TIOCM_CTS : 0)
          | ((status & CH341_BIT_DSR)   ? TIOCM_DSR : 0)
          | ((status & CH341_BIT_RI)    ? TIOCM_RI  : 0)
          | ((status & CH341_BIT_DCD)   ? TIOCM_CD  : 0);

    dev_dbg(&port->dev, "%s - result = %x\n", __func__, result);

    return result;
}

static int ch341_reset_resume(struct usb_serial *serial)
{
    struct ch341_private *priv;

    priv = usb_get_serial_port_data(serial->port[0]);

    /* reconfigure ch341 serial port after bus-reset */
    ch341_configure(serial->dev, priv);

    return 0;
}

static struct usb_serial_driver ch341_device = {
    .driver = {
        .owner  = THIS_MODULE,
        .name   = "ch341-uart",
    },
    .id_table          = id_table,
    .num_ports         = 1,
    .open              = ch341_open,
    .dtr_rts       = ch341_dtr_rts,
    .carrier_raised    = ch341_carrier_raised,
    .close             = ch341_close,
    .ioctl             = ch341_ioctl,
    .set_termios       = ch341_set_termios,
    .break_ctl         = ch341_break_ctl,
    .tiocmget          = ch341_tiocmget,
    .tiocmset          = ch341_tiocmset,
    .read_int_callback = ch341_read_int_callback,
    .port_probe        = ch341_port_probe,
    .port_remove       = ch341_port_remove,
    .reset_resume      = ch341_reset_resume,
};

static struct usb_serial_driver * const serial_drivers[] = {
    &ch341_device, NULL
};

module_usb_serial_driver(serial_drivers, id_table);

MODULE_LICENSE("GPL");