i2c-eg20t: change timeout value 50msec to 1000msec

[zen-stable.git] / drivers / tty / serial / mrst_max3110.c

/*
 *  mrst_max3110.c - spi uart protocol driver for Maxim 3110
 *
 * Copyright (c) 2008-2010, Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
 */

/*
 * Note:
 * 1. From Max3110 spec, the Rx FIFO has 8 words, while the Tx FIFO only has
 *    1 word. If SPI master controller doesn't support sclk frequency change,
 *    then the char need be sent out one by one with some delay
 *
 * 2. Currently only RX available interrupt is used, no need for waiting TXE
 *    interrupt for a low speed UART device
 */

#ifdef CONFIG_MAGIC_SYSRQ
#define SUPPORT_SYSRQ
#endif

#include <linux/module.h>
#include <linux/ioport.h>
#include <linux/irq.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/serial_core.h>
#include <linux/serial_reg.h>

#include <linux/kthread.h>
#include <linux/spi/spi.h>

#include "mrst_max3110.h"

#define PR_FMT  "mrst_max3110: "

#define UART_TX_NEEDED 1
#define CON_TX_NEEDED  2
#define BIT_IRQ_PENDING    3

struct uart_max3110 {
        struct uart_port port;
        struct spi_device *spi;
        char name[SPI_NAME_SIZE];

        wait_queue_head_t wq;
        struct task_struct *main_thread;
        struct task_struct *read_thread;
        struct mutex thread_mutex;

        u32 baud;
        u16 cur_conf;
        u8 clock;
        u8 parity, word_7bits;
        u16 irq;

        unsigned long uart_flags;

        /* console related */
        struct circ_buf con_xmit;
};

/* global data structure, may need be removed */
static struct uart_max3110 *pmax;

static int receive_chars(struct uart_max3110 *max,
                                unsigned short *str, int len);
static int max3110_read_multi(struct uart_max3110 *max);
static void max3110_con_receive(struct uart_max3110 *max);

static int max3110_write_then_read(struct uart_max3110 *max,
                const void *txbuf, void *rxbuf, unsigned len, int always_fast)
{
        struct spi_device *spi = max->spi;
        struct spi_message      message;
        struct spi_transfer     x;
        int ret;

        spi_message_init(&message);
        memset(&x, 0, sizeof x);
        x.len = len;
        x.tx_buf = txbuf;
        x.rx_buf = rxbuf;
        spi_message_add_tail(&x, &message);

        if (always_fast)
                x.speed_hz = spi->max_speed_hz;
        else if (max->baud)
                x.speed_hz = max->baud;

        /* Do the i/o */
        ret = spi_sync(spi, &message);
        return ret;
}

/* Write a 16b word to the device */
static int max3110_out(struct uart_max3110 *max, const u16 out)
{
        void *buf;
        u16 *obuf, *ibuf;
        int ret;

        buf = kzalloc(8, GFP_KERNEL | GFP_DMA);
        if (!buf)
                return -ENOMEM;

        obuf = buf;
        ibuf = buf + 4;
        *obuf = out;
        ret = max3110_write_then_read(max, obuf, ibuf, 2, 1);
        if (ret) {
                pr_warning(PR_FMT "%s(): get err msg %d when sending 0x%x\n",
                                __func__, ret, out);
                goto exit;
        }

        receive_chars(max, ibuf, 1);

exit:
        kfree(buf);
        return ret;
}

/*
 * This is usually used to read data from SPIC RX FIFO, which doesn't
 * need any delay like flushing character out.
 *
 * Return how many valide bytes are read back
 */
static int max3110_read_multi(struct uart_max3110 *max)
{
        void *buf;
        u16 *obuf, *ibuf;
        int ret, blen;

        blen = M3110_RX_FIFO_DEPTH * sizeof(u16);
        buf = kzalloc(blen * 2, GFP_KERNEL | GFP_DMA);
        if (!buf) {
                pr_warning(PR_FMT "%s(): fail to alloc dma buffer\n", __func__);
                return 0;
        }

        /* tx/rx always have the same length */
        obuf = buf;
        ibuf = buf + blen;

        if (max3110_write_then_read(max, obuf, ibuf, blen, 1)) {
                kfree(buf);
                return 0;
        }

        ret = receive_chars(max, ibuf, M3110_RX_FIFO_DEPTH);

        kfree(buf);
        return ret;
}

static void serial_m3110_con_putchar(struct uart_port *port, int ch)
{
        struct uart_max3110 *max =
                container_of(port, struct uart_max3110, port);
        struct circ_buf *xmit = &max->con_xmit;

        if (uart_circ_chars_free(xmit)) {
                xmit->buf[xmit->head] = (char)ch;
                xmit->head = (xmit->head + 1) & (PAGE_SIZE - 1);
        }
}

/*
 * Print a string to the serial port trying not to disturb
 * any possible real use of the port...
 *
 *      The console_lock must be held when we get here.
 */
static void serial_m3110_con_write(struct console *co,
                                const char *s, unsigned int count)
{
        if (!pmax)
                return;

        uart_console_write(&pmax->port, s, count, serial_m3110_con_putchar);

        if (!test_and_set_bit(CON_TX_NEEDED, &pmax->uart_flags))
                wake_up(&pmax->wq);
}

static int __init
serial_m3110_con_setup(struct console *co, char *options)
{
        struct uart_max3110 *max = pmax;
        int baud = 115200;
        int bits = 8;
        int parity = 'n';
        int flow = 'n';

        pr_info(PR_FMT "setting up console\n");

        if (co->index == -1)
                co->index = 0;

        if (!max) {
                pr_err(PR_FMT "pmax is NULL, return");
                return -ENODEV;
        }

        if (options)
                uart_parse_options(options, &baud, &parity, &bits, &flow);

        return uart_set_options(&max->port, co, baud, parity, bits, flow);
}

static struct tty_driver *serial_m3110_con_device(struct console *co,
                                                        int *index)
{
        struct uart_driver *p = co->data;
        *index = co->index;
        return p->tty_driver;
}

static struct uart_driver serial_m3110_reg;
static struct console serial_m3110_console = {
        .name           = "ttyS",
        .write          = serial_m3110_con_write,
        .device         = serial_m3110_con_device,
        .setup          = serial_m3110_con_setup,
        .flags          = CON_PRINTBUFFER,
        .index          = -1,
        .data           = &serial_m3110_reg,
};

static unsigned int serial_m3110_tx_empty(struct uart_port *port)
{
        return 1;
}

static void serial_m3110_stop_tx(struct uart_port *port)
{
        return;
}

/* stop_rx will be called in spin_lock env */
static void serial_m3110_stop_rx(struct uart_port *port)
{
        return;
}

#define WORDS_PER_XFER  128
static void send_circ_buf(struct uart_max3110 *max,
                                struct circ_buf *xmit)
{
        void *buf;
        u16 *obuf, *ibuf;
        int i, len, blen, dma_size, left, ret = 0;


        dma_size = WORDS_PER_XFER * sizeof(u16) * 2;
        buf = kzalloc(dma_size, GFP_KERNEL | GFP_DMA);
        if (!buf)
                return;
        obuf = buf;
        ibuf = buf + dma_size/2;

        while (!uart_circ_empty(xmit)) {
                left = uart_circ_chars_pending(xmit);
                while (left) {
                        len = min(left, WORDS_PER_XFER);
                        blen = len * sizeof(u16);
                        memset(ibuf, 0, blen);

                        for (i = 0; i < len; i++) {
                                obuf[i] = (u8)xmit->buf[xmit->tail] | WD_TAG;
                                xmit->tail = (xmit->tail + 1) &
                                                (UART_XMIT_SIZE - 1);
                        }

                        /* Fail to send msg to console is not very critical */

                        ret = max3110_write_then_read(max, obuf, ibuf, blen, 0);
                        if (ret)
                                pr_warning(PR_FMT "%s(): get err msg %d\n",
                                                __func__, ret);

                        receive_chars(max, ibuf, len);

                        max->port.icount.tx += len;
                        left -= len;
                }
        }

        kfree(buf);
}

static void transmit_char(struct uart_max3110 *max)
{
        struct uart_port *port = &max->port;
        struct circ_buf *xmit = &port->state->xmit;

        if (uart_circ_empty(xmit) || uart_tx_stopped(port))
                return;

        send_circ_buf(max, xmit);

        if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
                uart_write_wakeup(port);

        if (uart_circ_empty(xmit))
                serial_m3110_stop_tx(port);
}

/*
 * This will be called by uart_write() and tty_write, can't
 * go to sleep
 */
static void serial_m3110_start_tx(struct uart_port *port)
{
        struct uart_max3110 *max =
                container_of(port, struct uart_max3110, port);

        if (!test_and_set_bit(UART_TX_NEEDED, &max->uart_flags))
                wake_up(&max->wq);
}

static int
receive_chars(struct uart_max3110 *max, unsigned short *str, int len)
{
        struct uart_port *port = &max->port;
        struct tty_struct *tty;
        char buf[M3110_RX_FIFO_DEPTH];
        int r, w, usable;

        /* If uart is not opened, just return */
        if (!port->state)
                return 0;

        tty = tty_port_tty_get(&port->state->port);
        if (!tty)
                return 0;

        for (r = 0, w = 0; r < len; r++) {
                if (str[r] & MAX3110_BREAK &&
                    uart_handle_break(port))
                        continue;

                if (str[r] & MAX3110_READ_DATA_AVAILABLE) {
                        if (uart_handle_sysrq_char(port, str[r] & 0xff))
                                continue;

                        buf[w++] = str[r] & 0xff;
                }
        }

        if (!w) {
                tty_kref_put(tty);
                return 0;
        }

        for (r = 0; w; r += usable, w -= usable) {
                usable = tty_buffer_request_room(tty, w);
                if (usable) {
                        tty_insert_flip_string(tty, buf + r, usable);
                        port->icount.rx += usable;
                }
        }
        tty_flip_buffer_push(tty);
        tty_kref_put(tty);

        return r;
}

/*
 * This routine will be used in read_thread or RX IRQ handling,
 * it will first do one round buffer read(8 words), if there is some
 * valid RX data, will try to read 5 more rounds till all data
 * is read out.
 *
 * Use stack space as data buffer to save some system load, and chose
 * 504 Btyes as a threadhold to do a bulk push to upper tty layer when
 * receiving bulk data, a much bigger buffer may cause stack overflow
 */
static void max3110_con_receive(struct uart_max3110 *max)
{
        int loop = 1, num;

        do {
                num = max3110_read_multi(max);

                if (num) {
                        loop = 5;
                }
        } while (--loop);
}

static int max3110_main_thread(void *_max)
{
        struct uart_max3110 *max = _max;
        wait_queue_head_t *wq = &max->wq;
        int ret = 0;
        struct circ_buf *xmit = &max->con_xmit;

        pr_info(PR_FMT "start main thread\n");

        do {
                wait_event_interruptible(*wq,
                                max->uart_flags || kthread_should_stop());

                mutex_lock(&max->thread_mutex);

                if (test_and_clear_bit(BIT_IRQ_PENDING, &max->uart_flags))
                        max3110_con_receive(max);

                /* first handle console output */
                if (test_and_clear_bit(CON_TX_NEEDED, &max->uart_flags))
                        send_circ_buf(max, xmit);

                /* handle uart output */
                if (test_and_clear_bit(UART_TX_NEEDED, &max->uart_flags))
                        transmit_char(max);

                mutex_unlock(&max->thread_mutex);

        } while (!kthread_should_stop());

        return ret;
}

static irqreturn_t serial_m3110_irq(int irq, void *dev_id)
{
        struct uart_max3110 *max = dev_id;

        /* max3110's irq is a falling edge, not level triggered,
         * so no need to disable the irq */

        if (!test_and_set_bit(BIT_IRQ_PENDING, &max->uart_flags))
                wake_up(&max->wq);

        return IRQ_HANDLED;
}

/* if don't use RX IRQ, then need a thread to polling read */
static int max3110_read_thread(void *_max)
{
        struct uart_max3110 *max = _max;

        pr_info(PR_FMT "start read thread\n");
        do {
                /*
                 * If can't acquire the mutex, it means the main thread
                 * is running which will also perform the rx job
                 */
                if (mutex_trylock(&max->thread_mutex)) {
                        max3110_con_receive(max);
                        mutex_unlock(&max->thread_mutex);
                }

                set_current_state(TASK_INTERRUPTIBLE);
                schedule_timeout(HZ / 20);
        } while (!kthread_should_stop());

        return 0;
}

static int serial_m3110_startup(struct uart_port *port)
{
        struct uart_max3110 *max =
                container_of(port, struct uart_max3110, port);
        u16 config = 0;
        int ret = 0;

        if (port->line != 0) {
                pr_err(PR_FMT "uart port startup failed\n");
                return -1;
        }

        /* Disable all IRQ and config it to 115200, 8n1 */
        config = WC_TAG | WC_FIFO_ENABLE
                        | WC_1_STOPBITS
                        | WC_8BIT_WORD
                        | WC_BAUD_DR2;

        /* as we use thread to handle tx/rx, need set low latency */
        port->state->port.tty->low_latency = 1;

        if (max->irq) {
                max->read_thread = NULL;
                ret = request_irq(max->irq, serial_m3110_irq,
                                IRQ_TYPE_EDGE_FALLING, "max3110", max);
                if (ret) {
                        max->irq = 0;
                        pr_err(PR_FMT "unable to allocate IRQ, polling\n");
                }  else {
                        /* Enable RX IRQ only */
                        config |= WC_RXA_IRQ_ENABLE;
                }
        }

        if (max->irq == 0) {
                /* If IRQ is disabled, start a read thread for input data */
                max->read_thread =
                        kthread_run(max3110_read_thread, max, "max3110_read");
                if (IS_ERR(max->read_thread)) {
                        ret = PTR_ERR(max->read_thread);
                        max->read_thread = NULL;
                        pr_err(PR_FMT "Can't create read thread!\n");
                        return ret;
                }
        }

        ret = max3110_out(max, config);
        if (ret) {
                if (max->irq)
                        free_irq(max->irq, max);
                if (max->read_thread)
                        kthread_stop(max->read_thread);
                max->read_thread = NULL;
                return ret;
        }

        max->cur_conf = config;
        return 0;
}

static void serial_m3110_shutdown(struct uart_port *port)
{
        struct uart_max3110 *max =
                container_of(port, struct uart_max3110, port);
        u16 config;

        if (max->read_thread) {
                kthread_stop(max->read_thread);
                max->read_thread = NULL;
        }

        if (max->irq)
                free_irq(max->irq, max);

        /* Disable interrupts from this port */
        config = WC_TAG | WC_SW_SHDI;
        max3110_out(max, config);
}

static void serial_m3110_release_port(struct uart_port *port)
{
}

static int serial_m3110_request_port(struct uart_port *port)
{
        return 0;
}

static void serial_m3110_config_port(struct uart_port *port, int flags)
{
        port->type = PORT_MAX3100;
}

static int
serial_m3110_verify_port(struct uart_port *port, struct serial_struct *ser)
{
        /* we don't want the core code to modify any port params */
        return -EINVAL;
}


static const char *serial_m3110_type(struct uart_port *port)
{
        struct uart_max3110 *max =
                container_of(port, struct uart_max3110, port);
        return max->name;
}

static void
serial_m3110_set_termios(struct uart_port *port, struct ktermios *termios,
                       struct ktermios *old)
{
        struct uart_max3110 *max =
                container_of(port, struct uart_max3110, port);
        unsigned char cval;
        unsigned int baud, parity = 0;
        int clk_div = -1;
        u16 new_conf = max->cur_conf;

        switch (termios->c_cflag & CSIZE) {
        case CS7:
                cval = UART_LCR_WLEN7;
                new_conf |= WC_7BIT_WORD;
                break;
        default:
                /* We only support CS7 & CS8 */
                termios->c_cflag &= ~CSIZE;
                termios->c_cflag |= CS8;
        case CS8:
                cval = UART_LCR_WLEN8;
                new_conf |= WC_8BIT_WORD;
                break;
        }

        baud = uart_get_baud_rate(port, termios, old, 0, 230400);

        /* First calc the div for 1.8MHZ clock case */
        switch (baud) {
        case 300:
                clk_div = WC_BAUD_DR384;
                break;
        case 600:
                clk_div = WC_BAUD_DR192;
                break;
        case 1200:
                clk_div = WC_BAUD_DR96;
                break;
        case 2400:
                clk_div = WC_BAUD_DR48;
                break;
        case 4800:
                clk_div = WC_BAUD_DR24;
                break;
        case 9600:
                clk_div = WC_BAUD_DR12;
                break;
        case 19200:
                clk_div = WC_BAUD_DR6;
                break;
        case 38400:
                clk_div = WC_BAUD_DR3;
                break;
        case 57600:
                clk_div = WC_BAUD_DR2;
                break;
        case 115200:
                clk_div = WC_BAUD_DR1;
                break;
        case 230400:
                if (max->clock & MAX3110_HIGH_CLK)
                        break;
        default:
                /* Pick the previous baud rate */
                baud = max->baud;
                clk_div = max->cur_conf & WC_BAUD_DIV_MASK;
                tty_termios_encode_baud_rate(termios, baud, baud);
        }

        if (max->clock & MAX3110_HIGH_CLK) {
                clk_div += 1;
                /* High clk version max3110 doesn't support B300 */
                if (baud == 300) {
                        baud = 600;
                        clk_div = WC_BAUD_DR384;
                }
                if (baud == 230400)
                        clk_div = WC_BAUD_DR1;
                tty_termios_encode_baud_rate(termios, baud, baud);
        }

        new_conf = (new_conf & ~WC_BAUD_DIV_MASK) | clk_div;

        if (unlikely(termios->c_cflag & CMSPAR))
                termios->c_cflag &= ~CMSPAR;

        if (termios->c_cflag & CSTOPB)
                new_conf |= WC_2_STOPBITS;
        else
                new_conf &= ~WC_2_STOPBITS;

        if (termios->c_cflag & PARENB) {
                new_conf |= WC_PARITY_ENABLE;
                parity |= UART_LCR_PARITY;
        } else
                new_conf &= ~WC_PARITY_ENABLE;

        if (!(termios->c_cflag & PARODD))
                parity |= UART_LCR_EPAR;
        max->parity = parity;

        uart_update_timeout(port, termios->c_cflag, baud);

        new_conf |= WC_TAG;
        if (new_conf != max->cur_conf) {
                if (!max3110_out(max, new_conf)) {
                        max->cur_conf = new_conf;
                        max->baud = baud;
                }
        }
}

/* Don't handle hw handshaking */
static unsigned int serial_m3110_get_mctrl(struct uart_port *port)
{
        return TIOCM_DSR | TIOCM_CAR | TIOCM_DSR;
}

static void serial_m3110_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
}

static void serial_m3110_break_ctl(struct uart_port *port, int break_state)
{
}

static void serial_m3110_pm(struct uart_port *port, unsigned int state,
                        unsigned int oldstate)
{
}

static void serial_m3110_enable_ms(struct uart_port *port)
{
}

struct uart_ops serial_m3110_ops = {
        .tx_empty       = serial_m3110_tx_empty,
        .set_mctrl      = serial_m3110_set_mctrl,
        .get_mctrl      = serial_m3110_get_mctrl,
        .stop_tx        = serial_m3110_stop_tx,
        .start_tx       = serial_m3110_start_tx,
        .stop_rx        = serial_m3110_stop_rx,
        .enable_ms      = serial_m3110_enable_ms,
        .break_ctl      = serial_m3110_break_ctl,
        .startup        = serial_m3110_startup,
        .shutdown       = serial_m3110_shutdown,
        .set_termios    = serial_m3110_set_termios,
        .pm             = serial_m3110_pm,
        .type           = serial_m3110_type,
        .release_port   = serial_m3110_release_port,
        .request_port   = serial_m3110_request_port,
        .config_port    = serial_m3110_config_port,
        .verify_port    = serial_m3110_verify_port,
};

static struct uart_driver serial_m3110_reg = {
        .owner          = THIS_MODULE,
        .driver_name    = "MRST serial",
        .dev_name       = "ttyS",
        .major          = TTY_MAJOR,
        .minor          = 64,
        .nr             = 1,
        .cons           = &serial_m3110_console,
};

#ifdef CONFIG_PM
static int serial_m3110_suspend(struct spi_device *spi, pm_message_t state)
{
        struct uart_max3110 *max = spi_get_drvdata(spi);

        disable_irq(max->irq);
        uart_suspend_port(&serial_m3110_reg, &max->port);
        max3110_out(max, max->cur_conf | WC_SW_SHDI);
        return 0;
}

static int serial_m3110_resume(struct spi_device *spi)
{
        struct uart_max3110 *max = spi_get_drvdata(spi);

        max3110_out(max, max->cur_conf);
        uart_resume_port(&serial_m3110_reg, &max->port);
        enable_irq(max->irq);
        return 0;
}
#else
#define serial_m3110_suspend    NULL
#define serial_m3110_resume     NULL
#endif

static int __devinit serial_m3110_probe(struct spi_device *spi)
{
        struct uart_max3110 *max;
        void *buffer;
        u16 res;
        int ret = 0;

        max = kzalloc(sizeof(*max), GFP_KERNEL);
        if (!max)
                return -ENOMEM;

        /* Set spi info */
        spi->bits_per_word = 16;
        max->clock = MAX3110_HIGH_CLK;

        spi_setup(spi);

        max->port.type = PORT_MAX3100;
        max->port.fifosize = 2;         /* Only have 16b buffer */
        max->port.ops = &serial_m3110_ops;
        max->port.line = 0;
        max->port.dev = &spi->dev;
        max->port.uartclk = 115200;

        max->spi = spi;
        strcpy(max->name, spi->modalias);
        max->irq = (u16)spi->irq;

        mutex_init(&max->thread_mutex);

        max->word_7bits = 0;
        max->parity = 0;
        max->baud = 0;

        max->cur_conf = 0;
        max->uart_flags = 0;

        /* Check if reading configuration register returns something sane */

        res = RC_TAG;
        ret = max3110_write_then_read(max, (u8 *)&res, (u8 *)&res, 2, 0);
        if (ret < 0 || res == 0 || res == 0xffff) {
                dev_dbg(&spi->dev, "MAX3111 deemed not present (conf reg %04x)",
                                                                        res);
                ret = -ENODEV;
                goto err_get_page;
        }

        buffer = (void *)__get_free_page(GFP_KERNEL);
        if (!buffer) {
                ret = -ENOMEM;
                goto err_get_page;
        }
        max->con_xmit.buf = buffer;
        max->con_xmit.head = 0;
        max->con_xmit.tail = 0;

        init_waitqueue_head(&max->wq);

        max->main_thread = kthread_run(max3110_main_thread,
                                        max, "max3110_main");
        if (IS_ERR(max->main_thread)) {
                ret = PTR_ERR(max->main_thread);
                goto err_kthread;
        }

        spi_set_drvdata(spi, max);
        pmax = max;

        /* Give membase a psudo value to pass serial_core's check */
        max->port.membase = (void *)0xff110000;
        uart_add_one_port(&serial_m3110_reg, &max->port);

        return 0;

err_kthread:
        free_page((unsigned long)buffer);
err_get_page:
        kfree(max);
        return ret;
}

static int __devexit serial_m3110_remove(struct spi_device *dev)
{
        struct uart_max3110 *max = spi_get_drvdata(dev);

        if (!max)
                return 0;

        uart_remove_one_port(&serial_m3110_reg, &max->port);

        free_page((unsigned long)max->con_xmit.buf);

        if (max->main_thread)
                kthread_stop(max->main_thread);

        kfree(max);
        return 0;
}

static struct spi_driver uart_max3110_driver = {
        .driver = {
                        .name   = "spi_max3111",
                        .owner  = THIS_MODULE,
        },
        .probe          = serial_m3110_probe,
        .remove         = __devexit_p(serial_m3110_remove),
        .suspend        = serial_m3110_suspend,
        .resume         = serial_m3110_resume,
};

static int __init serial_m3110_init(void)
{
        int ret = 0;

        ret = uart_register_driver(&serial_m3110_reg);
        if (ret)
                return ret;

        ret = spi_register_driver(&uart_max3110_driver);
        if (ret)
                uart_unregister_driver(&serial_m3110_reg);

        return ret;
}

static void __exit serial_m3110_exit(void)
{
        spi_unregister_driver(&uart_max3110_driver);
        uart_unregister_driver(&serial_m3110_reg);
}

module_init(serial_m3110_init);
module_exit(serial_m3110_exit);

MODULE_LICENSE("GPL v2");
MODULE_ALIAS("spi:max3110-uart");