// SPDX-License-Identifier: GPL-2.0+
/*
 *
 *  Copyright (C) 2008 Christian Pellegrin <chripell@evolware.org>
 *
 * Notes: the MAX3100 doesn't provide an interrupt on CTS so we have
 * to use polling for flow control. TX empty IRQ is unusable, since
 * writing conf clears FIFO buffer and we cannot have this interrupt
 * always asking us for attention.
 *
 * Example platform data:

 static struct plat_max3100 max3100_plat_data = {
 .loopback = 0,
 .crystal = 0,
 .poll_time = 100,
 };

 static struct spi_board_info spi_board_info[] = {
 {
 .modalias      = "max3100",
 .platform_data = &max3100_plat_data,
 .irq           = IRQ_EINT12,
 .max_speed_hz  = 5*1000*1000,
 .chip_select   = 0,
 },
 };

 * The initial minor number is 209 in the low-density serial port:
 * mknod /dev/ttyMAX0 c 204 209
 */

#define MAX3100_MAJOR 204
#define MAX3100_MINOR 209
/* 4 MAX3100s should be enough for everyone */
#define MAX_MAX3100 4

#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/device.h>
#include <linux/module.h>
#include <linux/serial_core.h>
#include <linux/serial.h>
#include <linux/spi/spi.h>
#include <linux/freezer.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>

#include <linux/serial_max3100.h>

#define MAX3100_C    (1<<14)
#define MAX3100_D    (0<<14)
#define MAX3100_W    (1<<15)
#define MAX3100_RX   (0<<15)

#define MAX3100_WC   (MAX3100_W  | MAX3100_C)
#define MAX3100_RC   (MAX3100_RX | MAX3100_C)
#define MAX3100_WD   (MAX3100_W  | MAX3100_D)
#define MAX3100_RD   (MAX3100_RX | MAX3100_D)
#define MAX3100_CMD  (3 << 14)

#define MAX3100_T    (1<<14)
#define MAX3100_R    (1<<15)

#define MAX3100_FEN  (1<<13)
#define MAX3100_SHDN (1<<12)
#define MAX3100_TM   (1<<11)
#define MAX3100_RM   (1<<10)
#define MAX3100_PM   (1<<9)
#define MAX3100_RAM  (1<<8)
#define MAX3100_IR   (1<<7)
#define MAX3100_ST   (1<<6)
#define MAX3100_PE   (1<<5)
#define MAX3100_L    (1<<4)
#define MAX3100_BAUD (0xf)

#define MAX3100_TE   (1<<10)
#define MAX3100_RAFE (1<<10)
#define MAX3100_RTS  (1<<9)
#define MAX3100_CTS  (1<<9)
#define MAX3100_PT   (1<<8)
#define MAX3100_DATA (0xff)

#define MAX3100_RT   (MAX3100_R | MAX3100_T)
#define MAX3100_RTC  (MAX3100_RT | MAX3100_CTS | MAX3100_RAFE)

/* the following simulate a status reg for ignore_status_mask */
#define MAX3100_STATUS_PE 1
#define MAX3100_STATUS_FE 2
#define MAX3100_STATUS_OE 4

struct max3100_port {
        struct uart_port port;
        struct spi_device *spi;

        int cts;                /* last CTS received for flow ctrl */
        int tx_empty;           /* last TX empty bit */

        spinlock_t conf_lock;   /* shared data */
        int conf_commit;        /* need to make changes */
        int conf;               /* configuration for the MAX31000
                                 * (bits 0-7, bits 8-11 are irqs) */
        int rts_commit;         /* need to change rts */
        int rts;                /* rts status */
        int baud;               /* current baud rate */

        int parity;             /* keeps track if we should send parity */
#define MAX3100_PARITY_ON 1
#define MAX3100_PARITY_ODD 2
#define MAX3100_7BIT 4
        int rx_enabled;         /* if we should rx chars */

        int irq;                /* irq assigned to the max3100 */

        int minor;              /* minor number */
        int crystal;            /* 1 if 3.6864Mhz crystal 0 for 1.8432 */
        int loopback;           /* 1 if we are in loopback mode */

        /* for handling irqs: need workqueue since we do spi_sync */
        struct workqueue_struct *workqueue;
        struct work_struct work;
        /* set to 1 to make the workhandler exit as soon as possible */
        int  force_end_work;
        /* need to know we are suspending to avoid deadlock on workqueue */
        int suspending;

        /* hook for suspending MAX3100 via dedicated pin */
        void (*max3100_hw_suspend) (int suspend);

        /* poll time (in ms) for ctrl lines */
        int poll_time;
        /* and its timer */
        struct timer_list       timer;
};

static struct max3100_port *max3100s[MAX_MAX3100]; /* the chips */
static DEFINE_MUTEX(max3100s_lock);                /* race on probe */

static int max3100_do_parity(struct max3100_port *s, u16 c)
{
        int parity;

        if (s->parity & MAX3100_PARITY_ODD)
                parity = 1;
        else
                parity = 0;

        if (s->parity & MAX3100_7BIT)
                c &= 0x7f;
        else
                c &= 0xff;

        parity = parity ^ (hweight8(c) & 1);
        return parity;
}

static int max3100_check_parity(struct max3100_port *s, u16 c)
{
        return max3100_do_parity(s, c) == ((c >> 8) & 1);
}

static void max3100_calc_parity(struct max3100_port *s, u16 *c)
{
        if (s->parity & MAX3100_7BIT)
                *c &= 0x7f;
        else
                *c &= 0xff;

        if (s->parity & MAX3100_PARITY_ON)
                *c |= max3100_do_parity(s, *c) << 8;
}

static void max3100_work(struct work_struct *w);

static void max3100_dowork(struct max3100_port *s)
{
        if (!s->force_end_work && !freezing(current) && !s->suspending)
                queue_work(s->workqueue, &s->work);
}

static void max3100_timeout(struct timer_list *t)
{
        struct max3100_port *s = from_timer(s, t, timer);

        if (s->port.state) {
                max3100_dowork(s);
                mod_timer(&s->timer, jiffies + s->poll_time);
        }
}

static int max3100_sr(struct max3100_port *s, u16 tx, u16 *rx)
{
        struct spi_message message;
        u16 etx, erx;
        int status;
        struct spi_transfer tran = {
                .tx_buf = &etx,
                .rx_buf = &erx,
                .len = 2,
        };

        etx = cpu_to_be16(tx);
        spi_message_init(&message);
        spi_message_add_tail(&tran, &message);
        status = spi_sync(s->spi, &message);
        if (status) {
                dev_warn(&s->spi->dev, "error while calling spi_sync\n");
                return -EIO;
        }
        *rx = be16_to_cpu(erx);
        s->tx_empty = (*rx & MAX3100_T) > 0;
        dev_dbg(&s->spi->dev, "%04x - %04x\n", tx, *rx);
        return 0;
}

static int max3100_handlerx(struct max3100_port *s, u16 rx)
{
        unsigned int ch, flg, status = 0;
        int ret = 0, cts;

        if (rx & MAX3100_R && s->rx_enabled) {
                dev_dbg(&s->spi->dev, "%s\n", __func__);
                ch = rx & (s->parity & MAX3100_7BIT ? 0x7f : 0xff);
                if (rx & MAX3100_RAFE) {
                        s->port.icount.frame++;
                        flg = TTY_FRAME;
                        status |= MAX3100_STATUS_FE;
                } else {
                        if (s->parity & MAX3100_PARITY_ON) {
                                if (max3100_check_parity(s, rx)) {
                                        s->port.icount.rx++;
                                        flg = TTY_NORMAL;
                                } else {
                                        s->port.icount.parity++;
                                        flg = TTY_PARITY;
                                        status |= MAX3100_STATUS_PE;
                                }
                        } else {
                                s->port.icount.rx++;
                                flg = TTY_NORMAL;
                        }
                }
                uart_insert_char(&s->port, status, MAX3100_STATUS_OE, ch, flg);
                ret = 1;
        }

        cts = (rx & MAX3100_CTS) > 0;
        if (s->cts != cts) {
                s->cts = cts;
                uart_handle_cts_change(&s->port, cts ? TIOCM_CTS : 0);
        }

        return ret;
}

static void max3100_work(struct work_struct *w)
{
        struct max3100_port *s = container_of(w, struct max3100_port, work);
        int rxchars;
        u16 tx, rx;
        int conf, cconf, crts;
        struct circ_buf *xmit = &s->port.state->xmit;

        dev_dbg(&s->spi->dev, "%s\n", __func__);

        rxchars = 0;
        do {
                spin_lock(&s->conf_lock);
                conf = s->conf;
                cconf = s->conf_commit;
                s->conf_commit = 0;
                crts = s->rts_commit;
                s->rts_commit = 0;
                spin_unlock(&s->conf_lock);
                if (cconf)
                        max3100_sr(s, MAX3100_WC | conf, &rx);
                if (crts) {
                        max3100_sr(s, MAX3100_WD | MAX3100_TE |
                                   (s->rts ? MAX3100_RTS : 0), &rx);
                        rxchars += max3100_handlerx(s, rx);
                }

                max3100_sr(s, MAX3100_RD, &rx);
                rxchars += max3100_handlerx(s, rx);

                if (rx & MAX3100_T) {
                        tx = 0xffff;
                        if (s->port.x_char) {
                                tx = s->port.x_char;
                                s->port.icount.tx++;
                                s->port.x_char = 0;
                        } else if (!uart_circ_empty(xmit) &&
                                   !uart_tx_stopped(&s->port)) {
                                tx = xmit->buf[xmit->tail];
                                xmit->tail = (xmit->tail + 1) &
                                        (UART_XMIT_SIZE - 1);
                                s->port.icount.tx++;
                        }
                        if (tx != 0xffff) {
                                max3100_calc_parity(s, &tx);
                                tx |= MAX3100_WD | (s->rts ? MAX3100_RTS : 0);
                                max3100_sr(s, tx, &rx);
                                rxchars += max3100_handlerx(s, rx);
                        }
                }

                if (rxchars > 16) {
                        tty_flip_buffer_push(&s->port.state->port);
                        rxchars = 0;
                }
                if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
                        uart_write_wakeup(&s->port);

        } while (!s->force_end_work &&
                 !freezing(current) &&
                 ((rx & MAX3100_R) ||
                  (!uart_circ_empty(xmit) &&
                   !uart_tx_stopped(&s->port))));

        if (rxchars > 0)
                tty_flip_buffer_push(&s->port.state->port);
}

static irqreturn_t max3100_irq(int irqno, void *dev_id)
{
        struct max3100_port *s = dev_id;

        dev_dbg(&s->spi->dev, "%s\n", __func__);

        max3100_dowork(s);
        return IRQ_HANDLED;
}

static void max3100_enable_ms(struct uart_port *port)
{
        struct max3100_port *s = container_of(port,
                                              struct max3100_port,
                                              port);

        if (s->poll_time > 0)
                mod_timer(&s->timer, jiffies);
        dev_dbg(&s->spi->dev, "%s\n", __func__);
}

static void max3100_start_tx(struct uart_port *port)
{
        struct max3100_port *s = container_of(port,
                                              struct max3100_port,
                                              port);

        dev_dbg(&s->spi->dev, "%s\n", __func__);

        max3100_dowork(s);
}

static void max3100_stop_rx(struct uart_port *port)
{
        struct max3100_port *s = container_of(port,
                                              struct max3100_port,
                                              port);

        dev_dbg(&s->spi->dev, "%s\n", __func__);

        s->rx_enabled = 0;
        spin_lock(&s->conf_lock);
        s->conf &= ~MAX3100_RM;
        s->conf_commit = 1;
        spin_unlock(&s->conf_lock);
        max3100_dowork(s);
}

static unsigned int max3100_tx_empty(struct uart_port *port)
{
        struct max3100_port *s = container_of(port,
                                              struct max3100_port,
                                              port);

        dev_dbg(&s->spi->dev, "%s\n", __func__);

        /* may not be truly up-to-date */
        max3100_dowork(s);
        return s->tx_empty;
}

static unsigned int max3100_get_mctrl(struct uart_port *port)
{
        struct max3100_port *s = container_of(port,
                                              struct max3100_port,
                                              port);

        dev_dbg(&s->spi->dev, "%s\n", __func__);

        /* may not be truly up-to-date */
        max3100_dowork(s);
        /* always assert DCD and DSR since these lines are not wired */
        return (s->cts ? TIOCM_CTS : 0) | TIOCM_DSR | TIOCM_CAR;
}

static void max3100_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
        struct max3100_port *s = container_of(port,
                                              struct max3100_port,
                                              port);
        int rts;

        dev_dbg(&s->spi->dev, "%s\n", __func__);

        rts = (mctrl & TIOCM_RTS) > 0;

        spin_lock(&s->conf_lock);
        if (s->rts != rts) {
                s->rts = rts;
                s->rts_commit = 1;
                max3100_dowork(s);
        }
        spin_unlock(&s->conf_lock);
}

static void
max3100_set_termios(struct uart_port *port, struct ktermios *termios,
                    struct ktermios *old)
{
        struct max3100_port *s = container_of(port,
                                              struct max3100_port,
                                              port);
        int baud = 0;
        unsigned cflag;
        u32 param_new, param_mask, parity = 0;

        dev_dbg(&s->spi->dev, "%s\n", __func__);

        cflag = termios->c_cflag;
        param_mask = 0;

        baud = tty_termios_baud_rate(termios);
        param_new = s->conf & MAX3100_BAUD;
        switch (baud) {
        case 300:
                if (s->crystal)
                        baud = s->baud;
                else
                        param_new = 15;
                break;
        case 600:
                param_new = 14 + s->crystal;
                break;
        case 1200:
                param_new = 13 + s->crystal;
                break;
        case 2400:
                param_new = 12 + s->crystal;
                break;
        case 4800:
                param_new = 11 + s->crystal;
                break;
        case 9600:
                param_new = 10 + s->crystal;
                break;
        case 19200:
                param_new = 9 + s->crystal;
                break;
        case 38400:
                param_new = 8 + s->crystal;
                break;
        case 57600:
                param_new = 1 + s->crystal;
                break;
        case 115200:
                param_new = 0 + s->crystal;
                break;
        case 230400:
                if (s->crystal)
                        param_new = 0;
                else
                        baud = s->baud;
                break;
        default:
                baud = s->baud;
        }
        tty_termios_encode_baud_rate(termios, baud, baud);
        s->baud = baud;
        param_mask |= MAX3100_BAUD;

        if ((cflag & CSIZE) == CS8) {
                param_new &= ~MAX3100_L;
                parity &= ~MAX3100_7BIT;
        } else {
                param_new |= MAX3100_L;
                parity |= MAX3100_7BIT;
                cflag = (cflag & ~CSIZE) | CS7;
        }
        param_mask |= MAX3100_L;

        if (cflag & CSTOPB)
                param_new |= MAX3100_ST;
        else
                param_new &= ~MAX3100_ST;
        param_mask |= MAX3100_ST;

        if (cflag & PARENB) {
                param_new |= MAX3100_PE;
                parity |= MAX3100_PARITY_ON;
        } else {
                param_new &= ~MAX3100_PE;
                parity &= ~MAX3100_PARITY_ON;
        }
        param_mask |= MAX3100_PE;

        if (cflag & PARODD)
                parity |= MAX3100_PARITY_ODD;
        else
                parity &= ~MAX3100_PARITY_ODD;

        /* mask termios capabilities we don't support */
        cflag &= ~CMSPAR;
        termios->c_cflag = cflag;

        s->port.ignore_status_mask = 0;
        if (termios->c_iflag & IGNPAR)
                s->port.ignore_status_mask |=
                        MAX3100_STATUS_PE | MAX3100_STATUS_FE |
                        MAX3100_STATUS_OE;

        if (s->poll_time > 0)
                del_timer_sync(&s->timer);

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

        spin_lock(&s->conf_lock);
        s->conf = (s->conf & ~param_mask) | (param_new & param_mask);
        s->conf_commit = 1;
        s->parity = parity;
        spin_unlock(&s->conf_lock);
        max3100_dowork(s);

        if (UART_ENABLE_MS(&s->port, termios->c_cflag))
                max3100_enable_ms(&s->port);
}

static void max3100_shutdown(struct uart_port *port)
{
        struct max3100_port *s = container_of(port,
                                              struct max3100_port,
                                              port);

        dev_dbg(&s->spi->dev, "%s\n", __func__);

        if (s->suspending)
                return;

        s->force_end_work = 1;

        if (s->poll_time > 0)
                del_timer_sync(&s->timer);

        if (s->workqueue) {
                flush_workqueue(s->workqueue);
                destroy_workqueue(s->workqueue);
                s->workqueue = NULL;
        }
        if (s->irq)
                free_irq(s->irq, s);

        /* set shutdown mode to save power */
        if (s->max3100_hw_suspend)
                s->max3100_hw_suspend(1);
        else  {
                u16 tx, rx;

                tx = MAX3100_WC | MAX3100_SHDN;
                max3100_sr(s, tx, &rx);
        }
}

static int max3100_startup(struct uart_port *port)
{
        struct max3100_port *s = container_of(port,
                                              struct max3100_port,
                                              port);
        char b[12];

        dev_dbg(&s->spi->dev, "%s\n", __func__);

        s->conf = MAX3100_RM;
        s->baud = s->crystal ? 230400 : 115200;
        s->rx_enabled = 1;

        if (s->suspending)
                return 0;

        s->force_end_work = 0;
        s->parity = 0;
        s->rts = 0;

        sprintf(b, "max3100-%d", s->minor);
        s->workqueue = create_freezable_workqueue(b);
        if (!s->workqueue) {
                dev_warn(&s->spi->dev, "cannot create workqueue\n");
                return -EBUSY;
        }
        INIT_WORK(&s->work, max3100_work);

        if (request_irq(s->irq, max3100_irq,
                        IRQF_TRIGGER_FALLING, "max3100", s) < 0) {
                dev_warn(&s->spi->dev, "cannot allocate irq %d\n", s->irq);
                s->irq = 0;
                destroy_workqueue(s->workqueue);
                s->workqueue = NULL;
                return -EBUSY;
        }

        if (s->loopback) {
                u16 tx, rx;
                tx = 0x4001;
                max3100_sr(s, tx, &rx);
        }

        if (s->max3100_hw_suspend)
                s->max3100_hw_suspend(0);
        s->conf_commit = 1;
        max3100_dowork(s);
        /* wait for clock to settle */
        msleep(50);

        max3100_enable_ms(&s->port);

        return 0;
}

static const char *max3100_type(struct uart_port *port)
{
        struct max3100_port *s = container_of(port,
                                              struct max3100_port,
                                              port);

        dev_dbg(&s->spi->dev, "%s\n", __func__);

        return s->port.type == PORT_MAX3100 ? "MAX3100" : NULL;
}

static void max3100_release_port(struct uart_port *port)
{
        struct max3100_port *s = container_of(port,
                                              struct max3100_port,
                                              port);

        dev_dbg(&s->spi->dev, "%s\n", __func__);
}

static void max3100_config_port(struct uart_port *port, int flags)
{
        struct max3100_port *s = container_of(port,
                                              struct max3100_port,
                                              port);

        dev_dbg(&s->spi->dev, "%s\n", __func__);

        if (flags & UART_CONFIG_TYPE)
                s->port.type = PORT_MAX3100;
}

static int max3100_verify_port(struct uart_port *port,
                               struct serial_struct *ser)
{
        struct max3100_port *s = container_of(port,
                                              struct max3100_port,
                                              port);
        int ret = -EINVAL;

        dev_dbg(&s->spi->dev, "%s\n", __func__);

        if (ser->type == PORT_UNKNOWN || ser->type == PORT_MAX3100)
                ret = 0;
        return ret;
}

static void max3100_stop_tx(struct uart_port *port)
{
        struct max3100_port *s = container_of(port,
                                              struct max3100_port,
                                              port);

        dev_dbg(&s->spi->dev, "%s\n", __func__);
}

static int max3100_request_port(struct uart_port *port)
{
        struct max3100_port *s = container_of(port,
                                              struct max3100_port,
                                              port);

        dev_dbg(&s->spi->dev, "%s\n", __func__);
        return 0;
}

static void max3100_break_ctl(struct uart_port *port, int break_state)
{
        struct max3100_port *s = container_of(port,
                                              struct max3100_port,
                                              port);

        dev_dbg(&s->spi->dev, "%s\n", __func__);
}

static const struct uart_ops max3100_ops = {
        .tx_empty       = max3100_tx_empty,
        .set_mctrl      = max3100_set_mctrl,
        .get_mctrl      = max3100_get_mctrl,
        .stop_tx        = max3100_stop_tx,
        .start_tx       = max3100_start_tx,
        .stop_rx        = max3100_stop_rx,
        .enable_ms      = max3100_enable_ms,
        .break_ctl      = max3100_break_ctl,
        .startup        = max3100_startup,
        .shutdown       = max3100_shutdown,
        .set_termios    = max3100_set_termios,
        .type           = max3100_type,
        .release_port   = max3100_release_port,
        .request_port   = max3100_request_port,
        .config_port    = max3100_config_port,
        .verify_port    = max3100_verify_port,
};

static struct uart_driver max3100_uart_driver = {
        .owner          = THIS_MODULE,
        .driver_name    = "ttyMAX",
        .dev_name       = "ttyMAX",
        .major          = MAX3100_MAJOR,
        .minor          = MAX3100_MINOR,
        .nr             = MAX_MAX3100,
};
static int uart_driver_registered;

static int max3100_probe(struct spi_device *spi)
{
        int i, retval;
        struct plat_max3100 *pdata;
        u16 tx, rx;

        mutex_lock(&max3100s_lock);

        if (!uart_driver_registered) {
                uart_driver_registered = 1;
                retval = uart_register_driver(&max3100_uart_driver);
                if (retval) {
                        printk(KERN_ERR "Couldn't register max3100 uart driver\n");
                        mutex_unlock(&max3100s_lock);
                        return retval;
                }
        }

        for (i = 0; i < MAX_MAX3100; i++)
                if (!max3100s[i])
                        break;
        if (i == MAX_MAX3100) {
                dev_warn(&spi->dev, "too many MAX3100 chips\n");
                mutex_unlock(&max3100s_lock);
                return -ENOMEM;
        }

        max3100s[i] = kzalloc(sizeof(struct max3100_port), GFP_KERNEL);
        if (!max3100s[i]) {
                dev_warn(&spi->dev,
                         "kmalloc for max3100 structure %d failed!\n", i);
                mutex_unlock(&max3100s_lock);
                return -ENOMEM;
        }
        max3100s[i]->spi = spi;
        max3100s[i]->irq = spi->irq;
        spin_lock_init(&max3100s[i]->conf_lock);
        spi_set_drvdata(spi, max3100s[i]);
        pdata = dev_get_platdata(&spi->dev);
        max3100s[i]->crystal = pdata->crystal;
        max3100s[i]->loopback = pdata->loopback;
        max3100s[i]->poll_time = msecs_to_jiffies(pdata->poll_time);
        if (pdata->poll_time > 0 && max3100s[i]->poll_time == 0)
                max3100s[i]->poll_time = 1;
        max3100s[i]->max3100_hw_suspend = pdata->max3100_hw_suspend;
        max3100s[i]->minor = i;
        timer_setup(&max3100s[i]->timer, max3100_timeout, 0);

        dev_dbg(&spi->dev, "%s: adding port %d\n", __func__, i);
        max3100s[i]->port.irq = max3100s[i]->irq;
        max3100s[i]->port.uartclk = max3100s[i]->crystal ? 3686400 : 1843200;
        max3100s[i]->port.fifosize = 16;
        max3100s[i]->port.ops = &max3100_ops;
        max3100s[i]->port.flags = UPF_SKIP_TEST | UPF_BOOT_AUTOCONF;
        max3100s[i]->port.line = i;
        max3100s[i]->port.type = PORT_MAX3100;
        max3100s[i]->port.dev = &spi->dev;
        retval = uart_add_one_port(&max3100_uart_driver, &max3100s[i]->port);
        if (retval < 0)
                dev_warn(&spi->dev,
                         "uart_add_one_port failed for line %d with error %d\n",
                         i, retval);

        /* set shutdown mode to save power. Will be woken-up on open */
        if (max3100s[i]->max3100_hw_suspend)
                max3100s[i]->max3100_hw_suspend(1);
        else {
                tx = MAX3100_WC | MAX3100_SHDN;
                max3100_sr(max3100s[i], tx, &rx);
        }
        mutex_unlock(&max3100s_lock);
        return 0;
}

static int max3100_remove(struct spi_device *spi)
{
        struct max3100_port *s = spi_get_drvdata(spi);
        int i;

        mutex_lock(&max3100s_lock);

        /* find out the index for the chip we are removing */
        for (i = 0; i < MAX_MAX3100; i++)
                if (max3100s[i] == s) {
                        dev_dbg(&spi->dev, "%s: removing port %d\n", __func__, i);
                        uart_remove_one_port(&max3100_uart_driver, &max3100s[i]->port);
                        kfree(max3100s[i]);
                        max3100s[i] = NULL;
                        break;
                }

        WARN_ON(i == MAX_MAX3100);
        
        /* check if this is the last chip we have */
        for (i = 0; i < MAX_MAX3100; i++)
                if (max3100s[i]) {
                        mutex_unlock(&max3100s_lock);
                        return 0;
                }
        pr_debug("removing max3100 driver\n");
        uart_unregister_driver(&max3100_uart_driver);

        mutex_unlock(&max3100s_lock);
        return 0;
}

#ifdef CONFIG_PM_SLEEP

static int max3100_suspend(struct device *dev)
{
        struct max3100_port *s = dev_get_drvdata(dev);

        dev_dbg(&s->spi->dev, "%s\n", __func__);

        disable_irq(s->irq);

        s->suspending = 1;
        uart_suspend_port(&max3100_uart_driver, &s->port);

        if (s->max3100_hw_suspend)
                s->max3100_hw_suspend(1);
        else {
                /* no HW suspend, so do SW one */
                u16 tx, rx;

                tx = MAX3100_WC | MAX3100_SHDN;
                max3100_sr(s, tx, &rx);
        }
        return 0;
}

static int max3100_resume(struct device *dev)
{
        struct max3100_port *s = dev_get_drvdata(dev);

        dev_dbg(&s->spi->dev, "%s\n", __func__);

        if (s->max3100_hw_suspend)
                s->max3100_hw_suspend(0);
        uart_resume_port(&max3100_uart_driver, &s->port);
        s->suspending = 0;

        enable_irq(s->irq);

        s->conf_commit = 1;
        if (s->workqueue)
                max3100_dowork(s);

        return 0;
}

static SIMPLE_DEV_PM_OPS(max3100_pm_ops, max3100_suspend, max3100_resume);
#define MAX3100_PM_OPS (&max3100_pm_ops)

#else
#define MAX3100_PM_OPS NULL
#endif

static struct spi_driver max3100_driver = {
        .driver = {
                .name           = "max3100",
                .pm             = MAX3100_PM_OPS,
        },
        .probe          = max3100_probe,
        .remove         = max3100_remove,
};

module_spi_driver(max3100_driver);

MODULE_DESCRIPTION("MAX3100 driver");
MODULE_AUTHOR("Christian Pellegrin <chripell@evolware.org>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("spi:max3100");