// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * SDIO UART/GPS driver
 *
 * Based on drivers/serial/8250.c and drivers/serial/serial_core.c
 * by Russell King.
 *
 * Author:      Nicolas Pitre
 * Created:     June 15, 2007
 * Copyright:   MontaVista Software, Inc.
 */

/*
 * Note: Although this driver assumes a 16550A-like UART implementation,
 * it is not possible to leverage the common 8250/16550 driver, nor the
 * core UART infrastructure, as they assumes direct access to the hardware
 * registers, often under a spinlock.  This is not possible in the SDIO
 * context as SDIO access functions must be able to sleep.
 *
 * Because we need to lock the SDIO host to ensure an exclusive access to
 * the card, we simply rely on that lock to also prevent and serialize
 * concurrent access to the same port.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mutex.h>
#include <linux/seq_file.h>
#include <linux/serial_reg.h>
#include <linux/circ_buf.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/kfifo.h>
#include <linux/slab.h>

#include <linux/mmc/core.h>
#include <linux/mmc/card.h>
#include <linux/mmc/sdio_func.h>
#include <linux/mmc/sdio_ids.h>


#define UART_NR         8       /* Number of UARTs this driver can handle */


#define FIFO_SIZE       PAGE_SIZE
#define WAKEUP_CHARS    256

struct uart_icount {
        __u32   cts;
        __u32   dsr;
        __u32   rng;
        __u32   dcd;
        __u32   rx;
        __u32   tx;
        __u32   frame;
        __u32   overrun;
        __u32   parity;
        __u32   brk;
};

struct sdio_uart_port {
        struct tty_port         port;
        unsigned int            index;
        struct sdio_func        *func;
        struct mutex            func_lock;
        struct task_struct      *in_sdio_uart_irq;
        unsigned int            regs_offset;
        struct kfifo            xmit_fifo;
        spinlock_t              write_lock;
        struct uart_icount      icount;
        unsigned int            uartclk;
        unsigned int            mctrl;
        unsigned int            rx_mctrl;
        unsigned int            read_status_mask;
        unsigned int            ignore_status_mask;
        unsigned char           x_char;
        unsigned char           ier;
        unsigned char           lcr;
};

static struct sdio_uart_port *sdio_uart_table[UART_NR];
static DEFINE_SPINLOCK(sdio_uart_table_lock);

static int sdio_uart_add_port(struct sdio_uart_port *port)
{
        int index, ret = -EBUSY;

        mutex_init(&port->func_lock);
        spin_lock_init(&port->write_lock);
        if (kfifo_alloc(&port->xmit_fifo, FIFO_SIZE, GFP_KERNEL))
                return -ENOMEM;

        spin_lock(&sdio_uart_table_lock);
        for (index = 0; index < UART_NR; index++) {
                if (!sdio_uart_table[index]) {
                        port->index = index;
                        sdio_uart_table[index] = port;
                        ret = 0;
                        break;
                }
        }
        spin_unlock(&sdio_uart_table_lock);

        return ret;
}

static struct sdio_uart_port *sdio_uart_port_get(unsigned index)
{
        struct sdio_uart_port *port;

        if (index >= UART_NR)
                return NULL;

        spin_lock(&sdio_uart_table_lock);
        port = sdio_uart_table[index];
        if (port)
                tty_port_get(&port->port);
        spin_unlock(&sdio_uart_table_lock);

        return port;
}

static void sdio_uart_port_put(struct sdio_uart_port *port)
{
        tty_port_put(&port->port);
}

static void sdio_uart_port_remove(struct sdio_uart_port *port)
{
        struct sdio_func *func;

        spin_lock(&sdio_uart_table_lock);
        sdio_uart_table[port->index] = NULL;
        spin_unlock(&sdio_uart_table_lock);

        /*
         * We're killing a port that potentially still is in use by
         * the tty layer. Be careful to prevent any further access
         * to the SDIO function and arrange for the tty layer to
         * give up on that port ASAP.
         * Beware: the lock ordering is critical.
         */
        mutex_lock(&port->port.mutex);
        mutex_lock(&port->func_lock);
        func = port->func;
        sdio_claim_host(func);
        port->func = NULL;
        mutex_unlock(&port->func_lock);
        /* tty_hangup is async so is this safe as is ?? */
        tty_port_tty_hangup(&port->port, false);
        mutex_unlock(&port->port.mutex);
        sdio_release_irq(func);
        sdio_disable_func(func);
        sdio_release_host(func);

        sdio_uart_port_put(port);
}

static int sdio_uart_claim_func(struct sdio_uart_port *port)
{
        mutex_lock(&port->func_lock);
        if (unlikely(!port->func)) {
                mutex_unlock(&port->func_lock);
                return -ENODEV;
        }
        if (likely(port->in_sdio_uart_irq != current))
                sdio_claim_host(port->func);
        mutex_unlock(&port->func_lock);
        return 0;
}

static inline void sdio_uart_release_func(struct sdio_uart_port *port)
{
        if (likely(port->in_sdio_uart_irq != current))
                sdio_release_host(port->func);
}

static inline unsigned int sdio_in(struct sdio_uart_port *port, int offset)
{
        unsigned char c;
        c = sdio_readb(port->func, port->regs_offset + offset, NULL);
        return c;
}

static inline void sdio_out(struct sdio_uart_port *port, int offset, int value)
{
        sdio_writeb(port->func, value, port->regs_offset + offset, NULL);
}

static unsigned int sdio_uart_get_mctrl(struct sdio_uart_port *port)
{
        unsigned char status;
        unsigned int ret;

        /* FIXME: What stops this losing the delta bits and breaking
           sdio_uart_check_modem_status ? */
        status = sdio_in(port, UART_MSR);

        ret = 0;
        if (status & UART_MSR_DCD)
                ret |= TIOCM_CAR;
        if (status & UART_MSR_RI)
                ret |= TIOCM_RNG;
        if (status & UART_MSR_DSR)
                ret |= TIOCM_DSR;
        if (status & UART_MSR_CTS)
                ret |= TIOCM_CTS;
        return ret;
}

static void sdio_uart_write_mctrl(struct sdio_uart_port *port,
                                  unsigned int mctrl)
{
        unsigned char mcr = 0;

        if (mctrl & TIOCM_RTS)
                mcr |= UART_MCR_RTS;
        if (mctrl & TIOCM_DTR)
                mcr |= UART_MCR_DTR;
        if (mctrl & TIOCM_OUT1)
                mcr |= UART_MCR_OUT1;
        if (mctrl & TIOCM_OUT2)
                mcr |= UART_MCR_OUT2;
        if (mctrl & TIOCM_LOOP)
                mcr |= UART_MCR_LOOP;

        sdio_out(port, UART_MCR, mcr);
}

static inline void sdio_uart_update_mctrl(struct sdio_uart_port *port,
                                          unsigned int set, unsigned int clear)
{
        unsigned int old;

        old = port->mctrl;
        port->mctrl = (old & ~clear) | set;
        if (old != port->mctrl)
                sdio_uart_write_mctrl(port, port->mctrl);
}

#define sdio_uart_set_mctrl(port, x)    sdio_uart_update_mctrl(port, x, 0)
#define sdio_uart_clear_mctrl(port, x)  sdio_uart_update_mctrl(port, 0, x)

static void sdio_uart_change_speed(struct sdio_uart_port *port,
                                   struct ktermios *termios,
                                   struct ktermios *old)
{
        unsigned char cval, fcr = 0;
        unsigned int baud, quot;

        switch (termios->c_cflag & CSIZE) {
        case CS5:
                cval = UART_LCR_WLEN5;
                break;
        case CS6:
                cval = UART_LCR_WLEN6;
                break;
        case CS7:
                cval = UART_LCR_WLEN7;
                break;
        default:
        case CS8:
                cval = UART_LCR_WLEN8;
                break;
        }

        if (termios->c_cflag & CSTOPB)
                cval |= UART_LCR_STOP;
        if (termios->c_cflag & PARENB)
                cval |= UART_LCR_PARITY;
        if (!(termios->c_cflag & PARODD))
                cval |= UART_LCR_EPAR;

        for (;;) {
                baud = tty_termios_baud_rate(termios);
                if (baud == 0)
                        baud = 9600;  /* Special case: B0 rate. */
                if (baud <= port->uartclk)
                        break;
                /*
                 * Oops, the quotient was zero.  Try again with the old
                 * baud rate if possible, otherwise default to 9600.
                 */
                termios->c_cflag &= ~CBAUD;
                if (old) {
                        termios->c_cflag |= old->c_cflag & CBAUD;
                        old = NULL;
                } else
                        termios->c_cflag |= B9600;
        }
        quot = (2 * port->uartclk + baud) / (2 * baud);

        if (baud < 2400)
                fcr = UART_FCR_ENABLE_FIFO | UART_FCR_TRIGGER_1;
        else
                fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10;

        port->read_status_mask = UART_LSR_OE | UART_LSR_THRE | UART_LSR_DR;
        if (termios->c_iflag & INPCK)
                port->read_status_mask |= UART_LSR_FE | UART_LSR_PE;
        if (termios->c_iflag & (BRKINT | PARMRK))
                port->read_status_mask |= UART_LSR_BI;

        /*
         * Characters to ignore
         */
        port->ignore_status_mask = 0;
        if (termios->c_iflag & IGNPAR)
                port->ignore_status_mask |= UART_LSR_PE | UART_LSR_FE;
        if (termios->c_iflag & IGNBRK) {
                port->ignore_status_mask |= UART_LSR_BI;
                /*
                 * If we're ignoring parity and break indicators,
                 * ignore overruns too (for real raw support).
                 */
                if (termios->c_iflag & IGNPAR)
                        port->ignore_status_mask |= UART_LSR_OE;
        }

        /*
         * ignore all characters if CREAD is not set
         */
        if ((termios->c_cflag & CREAD) == 0)
                port->ignore_status_mask |= UART_LSR_DR;

        /*
         * CTS flow control flag and modem status interrupts
         */
        port->ier &= ~UART_IER_MSI;
        if ((termios->c_cflag & CRTSCTS) || !(termios->c_cflag & CLOCAL))
                port->ier |= UART_IER_MSI;

        port->lcr = cval;

        sdio_out(port, UART_IER, port->ier);
        sdio_out(port, UART_LCR, cval | UART_LCR_DLAB);
        sdio_out(port, UART_DLL, quot & 0xff);
        sdio_out(port, UART_DLM, quot >> 8);
        sdio_out(port, UART_LCR, cval);
        sdio_out(port, UART_FCR, fcr);

        sdio_uart_write_mctrl(port, port->mctrl);
}

static void sdio_uart_start_tx(struct sdio_uart_port *port)
{
        if (!(port->ier & UART_IER_THRI)) {
                port->ier |= UART_IER_THRI;
                sdio_out(port, UART_IER, port->ier);
        }
}

static void sdio_uart_stop_tx(struct sdio_uart_port *port)
{
        if (port->ier & UART_IER_THRI) {
                port->ier &= ~UART_IER_THRI;
                sdio_out(port, UART_IER, port->ier);
        }
}

static void sdio_uart_stop_rx(struct sdio_uart_port *port)
{
        port->ier &= ~UART_IER_RLSI;
        port->read_status_mask &= ~UART_LSR_DR;
        sdio_out(port, UART_IER, port->ier);
}

static void sdio_uart_receive_chars(struct sdio_uart_port *port,
                                    unsigned int *status)
{
        unsigned int ch, flag;
        int max_count = 256;

        do {
                ch = sdio_in(port, UART_RX);
                flag = TTY_NORMAL;
                port->icount.rx++;

                if (unlikely(*status & (UART_LSR_BI | UART_LSR_PE |
                                        UART_LSR_FE | UART_LSR_OE))) {
                        /*
                         * For statistics only
                         */
                        if (*status & UART_LSR_BI) {
                                *status &= ~(UART_LSR_FE | UART_LSR_PE);
                                port->icount.brk++;
                        } else if (*status & UART_LSR_PE)
                                port->icount.parity++;
                        else if (*status & UART_LSR_FE)
                                port->icount.frame++;
                        if (*status & UART_LSR_OE)
                                port->icount.overrun++;

                        /*
                         * Mask off conditions which should be ignored.
                         */
                        *status &= port->read_status_mask;
                        if (*status & UART_LSR_BI)
                                flag = TTY_BREAK;
                        else if (*status & UART_LSR_PE)
                                flag = TTY_PARITY;
                        else if (*status & UART_LSR_FE)
                                flag = TTY_FRAME;
                }

                if ((*status & port->ignore_status_mask & ~UART_LSR_OE) == 0)
                        tty_insert_flip_char(&port->port, ch, flag);

                /*
                 * Overrun is special.  Since it's reported immediately,
                 * it doesn't affect the current character.
                 */
                if (*status & ~port->ignore_status_mask & UART_LSR_OE)
                        tty_insert_flip_char(&port->port, 0, TTY_OVERRUN);

                *status = sdio_in(port, UART_LSR);
        } while ((*status & UART_LSR_DR) && (max_count-- > 0));

        tty_flip_buffer_push(&port->port);
}

static void sdio_uart_transmit_chars(struct sdio_uart_port *port)
{
        struct kfifo *xmit = &port->xmit_fifo;
        int count;
        struct tty_struct *tty;
        u8 iobuf[16];
        int len;

        if (port->x_char) {
                sdio_out(port, UART_TX, port->x_char);
                port->icount.tx++;
                port->x_char = 0;
                return;
        }

        tty = tty_port_tty_get(&port->port);

        if (tty == NULL || !kfifo_len(xmit) ||
                                tty->flow.stopped || tty->hw_stopped) {
                sdio_uart_stop_tx(port);
                tty_kref_put(tty);
                return;
        }

        len = kfifo_out_locked(xmit, iobuf, 16, &port->write_lock);
        for (count = 0; count < len; count++) {
                sdio_out(port, UART_TX, iobuf[count]);
                port->icount.tx++;
        }

        len = kfifo_len(xmit);
        if (len < WAKEUP_CHARS) {
                tty_wakeup(tty);
                if (len == 0)
                        sdio_uart_stop_tx(port);
        }
        tty_kref_put(tty);
}

static void sdio_uart_check_modem_status(struct sdio_uart_port *port)
{
        int status;
        struct tty_struct *tty;

        status = sdio_in(port, UART_MSR);

        if ((status & UART_MSR_ANY_DELTA) == 0)
                return;

        if (status & UART_MSR_TERI)
                port->icount.rng++;
        if (status & UART_MSR_DDSR)
                port->icount.dsr++;
        if (status & UART_MSR_DDCD) {
                port->icount.dcd++;
                /* DCD raise - wake for open */
                if (status & UART_MSR_DCD)
                        wake_up_interruptible(&port->port.open_wait);
                else {
                        /* DCD drop - hang up if tty attached */
                        tty_port_tty_hangup(&port->port, false);
                }
        }
        if (status & UART_MSR_DCTS) {
                port->icount.cts++;
                tty = tty_port_tty_get(&port->port);
                if (tty && C_CRTSCTS(tty)) {
                        int cts = (status & UART_MSR_CTS);
                        if (tty->hw_stopped) {
                                if (cts) {
                                        tty->hw_stopped = 0;
                                        sdio_uart_start_tx(port);
                                        tty_wakeup(tty);
                                }
                        } else {
                                if (!cts) {
                                        tty->hw_stopped = 1;
                                        sdio_uart_stop_tx(port);
                                }
                        }
                }
                tty_kref_put(tty);
        }
}

/*
 * This handles the interrupt from one port.
 */
static void sdio_uart_irq(struct sdio_func *func)
{
        struct sdio_uart_port *port = sdio_get_drvdata(func);
        unsigned int iir, lsr;

        /*
         * In a few places sdio_uart_irq() is called directly instead of
         * waiting for the actual interrupt to be raised and the SDIO IRQ
         * thread scheduled in order to reduce latency.  However, some
         * interaction with the tty core may end up calling us back
         * (serial echo, flow control, etc.) through those same places
         * causing undesirable effects.  Let's stop the recursion here.
         */
        if (unlikely(port->in_sdio_uart_irq == current))
                return;

        iir = sdio_in(port, UART_IIR);
        if (iir & UART_IIR_NO_INT)
                return;

        port->in_sdio_uart_irq = current;
        lsr = sdio_in(port, UART_LSR);
        if (lsr & UART_LSR_DR)
                sdio_uart_receive_chars(port, &lsr);
        sdio_uart_check_modem_status(port);
        if (lsr & UART_LSR_THRE)
                sdio_uart_transmit_chars(port);
        port->in_sdio_uart_irq = NULL;
}

static int uart_carrier_raised(struct tty_port *tport)
{
        struct sdio_uart_port *port =
                        container_of(tport, struct sdio_uart_port, port);
        unsigned int ret = sdio_uart_claim_func(port);
        if (ret)        /* Missing hardware shouldn't block for carrier */
                return 1;
        ret = sdio_uart_get_mctrl(port);
        sdio_uart_release_func(port);
        if (ret & TIOCM_CAR)
                return 1;
        return 0;
}

/**
 *      uart_dtr_rts            -        port helper to set uart signals
 *      @tport: tty port to be updated
 *      @onoff: set to turn on DTR/RTS
 *
 *      Called by the tty port helpers when the modem signals need to be
 *      adjusted during an open, close and hangup.
 */

static void uart_dtr_rts(struct tty_port *tport, int onoff)
{
        struct sdio_uart_port *port =
                        container_of(tport, struct sdio_uart_port, port);
        int ret = sdio_uart_claim_func(port);
        if (ret)
                return;
        if (onoff == 0)
                sdio_uart_clear_mctrl(port, TIOCM_DTR | TIOCM_RTS);
        else
                sdio_uart_set_mctrl(port, TIOCM_DTR | TIOCM_RTS);
        sdio_uart_release_func(port);
}

/**
 *      sdio_uart_activate      -       start up hardware
 *      @tport: tty port to activate
 *      @tty: tty bound to this port
 *
 *      Activate a tty port. The port locking guarantees us this will be
 *      run exactly once per set of opens, and if successful will see the
 *      shutdown method run exactly once to match. Start up and shutdown are
 *      protected from each other by the internal locking and will not run
 *      at the same time even during a hangup event.
 *
 *      If we successfully start up the port we take an extra kref as we
 *      will keep it around until shutdown when the kref is dropped.
 */

static int sdio_uart_activate(struct tty_port *tport, struct tty_struct *tty)
{
        struct sdio_uart_port *port =
                        container_of(tport, struct sdio_uart_port, port);
        int ret;

        /*
         * Set the TTY IO error marker - we will only clear this
         * once we have successfully opened the port.
         */
        set_bit(TTY_IO_ERROR, &tty->flags);

        kfifo_reset(&port->xmit_fifo);

        ret = sdio_uart_claim_func(port);
        if (ret)
                return ret;
        ret = sdio_enable_func(port->func);
        if (ret)
                goto err1;
        ret = sdio_claim_irq(port->func, sdio_uart_irq);
        if (ret)
                goto err2;

        /*
         * Clear the FIFO buffers and disable them.
         * (they will be reenabled in sdio_change_speed())
         */
        sdio_out(port, UART_FCR, UART_FCR_ENABLE_FIFO);
        sdio_out(port, UART_FCR, UART_FCR_ENABLE_FIFO |
                       UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT);
        sdio_out(port, UART_FCR, 0);

        /*
         * Clear the interrupt registers.
         */
        (void) sdio_in(port, UART_LSR);
        (void) sdio_in(port, UART_RX);
        (void) sdio_in(port, UART_IIR);
        (void) sdio_in(port, UART_MSR);

        /*
         * Now, initialize the UART
         */
        sdio_out(port, UART_LCR, UART_LCR_WLEN8);

        port->ier = UART_IER_RLSI|UART_IER_RDI|UART_IER_RTOIE|UART_IER_UUE;
        port->mctrl = TIOCM_OUT2;

        sdio_uart_change_speed(port, &tty->termios, NULL);

        if (C_BAUD(tty))
                sdio_uart_set_mctrl(port, TIOCM_RTS | TIOCM_DTR);

        if (C_CRTSCTS(tty))
                if (!(sdio_uart_get_mctrl(port) & TIOCM_CTS))
                        tty->hw_stopped = 1;

        clear_bit(TTY_IO_ERROR, &tty->flags);

        /* Kick the IRQ handler once while we're still holding the host lock */
        sdio_uart_irq(port->func);

        sdio_uart_release_func(port);
        return 0;

err2:
        sdio_disable_func(port->func);
err1:
        sdio_uart_release_func(port);
        return ret;
}

/**
 *      sdio_uart_shutdown      -       stop hardware
 *      @tport: tty port to shut down
 *
 *      Deactivate a tty port. The port locking guarantees us this will be
 *      run only if a successful matching activate already ran. The two are
 *      protected from each other by the internal locking and will not run
 *      at the same time even during a hangup event.
 */

static void sdio_uart_shutdown(struct tty_port *tport)
{
        struct sdio_uart_port *port =
                        container_of(tport, struct sdio_uart_port, port);
        int ret;

        ret = sdio_uart_claim_func(port);
        if (ret)
                return;

        sdio_uart_stop_rx(port);

        /* Disable interrupts from this port */
        sdio_release_irq(port->func);
        port->ier = 0;
        sdio_out(port, UART_IER, 0);

        sdio_uart_clear_mctrl(port, TIOCM_OUT2);

        /* Disable break condition and FIFOs. */
        port->lcr &= ~UART_LCR_SBC;
        sdio_out(port, UART_LCR, port->lcr);
        sdio_out(port, UART_FCR, UART_FCR_ENABLE_FIFO |
                                 UART_FCR_CLEAR_RCVR |
                                 UART_FCR_CLEAR_XMIT);
        sdio_out(port, UART_FCR, 0);

        sdio_disable_func(port->func);

        sdio_uart_release_func(port);
}

static void sdio_uart_port_destroy(struct tty_port *tport)
{
        struct sdio_uart_port *port =
                container_of(tport, struct sdio_uart_port, port);
        kfifo_free(&port->xmit_fifo);
        kfree(port);
}

/**
 *      sdio_uart_install       -       install method
 *      @driver: the driver in use (sdio_uart in our case)
 *      @tty: the tty being bound
 *
 *      Look up and bind the tty and the driver together. Initialize
 *      any needed private data (in our case the termios)
 */

static int sdio_uart_install(struct tty_driver *driver, struct tty_struct *tty)
{
        int idx = tty->index;
        struct sdio_uart_port *port = sdio_uart_port_get(idx);
        int ret = tty_standard_install(driver, tty);

        if (ret == 0)
                /* This is the ref sdio_uart_port get provided */
                tty->driver_data = port;
        else
                sdio_uart_port_put(port);
        return ret;
}

/**
 *      sdio_uart_cleanup       -       called on the last tty kref drop
 *      @tty: the tty being destroyed
 *
 *      Called asynchronously when the last reference to the tty is dropped.
 *      We cannot destroy the tty->driver_data port kref until this point
 */

static void sdio_uart_cleanup(struct tty_struct *tty)
{
        struct sdio_uart_port *port = tty->driver_data;
        tty->driver_data = NULL;        /* Bug trap */
        sdio_uart_port_put(port);
}

/*
 *      Open/close/hangup is now entirely boilerplate
 */

static int sdio_uart_open(struct tty_struct *tty, struct file *filp)
{
        struct sdio_uart_port *port = tty->driver_data;
        return tty_port_open(&port->port, tty, filp);
}

static void sdio_uart_close(struct tty_struct *tty, struct file * filp)
{
        struct sdio_uart_port *port = tty->driver_data;
        tty_port_close(&port->port, tty, filp);
}

static void sdio_uart_hangup(struct tty_struct *tty)
{
        struct sdio_uart_port *port = tty->driver_data;
        tty_port_hangup(&port->port);
}

static int sdio_uart_write(struct tty_struct *tty, const unsigned char *buf,
                           int count)
{
        struct sdio_uart_port *port = tty->driver_data;
        int ret;

        if (!port->func)
                return -ENODEV;

        ret = kfifo_in_locked(&port->xmit_fifo, buf, count, &port->write_lock);
        if (!(port->ier & UART_IER_THRI)) {
                int err = sdio_uart_claim_func(port);
                if (!err) {
                        sdio_uart_start_tx(port);
                        sdio_uart_irq(port->func);
                        sdio_uart_release_func(port);
                } else
                        ret = err;
        }

        return ret;
}

static unsigned int sdio_uart_write_room(struct tty_struct *tty)
{
        struct sdio_uart_port *port = tty->driver_data;
        return FIFO_SIZE - kfifo_len(&port->xmit_fifo);
}

static unsigned int sdio_uart_chars_in_buffer(struct tty_struct *tty)
{
        struct sdio_uart_port *port = tty->driver_data;
        return kfifo_len(&port->xmit_fifo);
}

static void sdio_uart_send_xchar(struct tty_struct *tty, char ch)
{
        struct sdio_uart_port *port = tty->driver_data;

        port->x_char = ch;
        if (ch && !(port->ier & UART_IER_THRI)) {
                if (sdio_uart_claim_func(port) != 0)
                        return;
                sdio_uart_start_tx(port);
                sdio_uart_irq(port->func);
                sdio_uart_release_func(port);
        }
}

static void sdio_uart_throttle(struct tty_struct *tty)
{
        struct sdio_uart_port *port = tty->driver_data;

        if (!I_IXOFF(tty) && !C_CRTSCTS(tty))
                return;

        if (sdio_uart_claim_func(port) != 0)
                return;

        if (I_IXOFF(tty)) {
                port->x_char = STOP_CHAR(tty);
                sdio_uart_start_tx(port);
        }

        if (C_CRTSCTS(tty))
                sdio_uart_clear_mctrl(port, TIOCM_RTS);

        sdio_uart_irq(port->func);
        sdio_uart_release_func(port);
}

static void sdio_uart_unthrottle(struct tty_struct *tty)
{
        struct sdio_uart_port *port = tty->driver_data;

        if (!I_IXOFF(tty) && !C_CRTSCTS(tty))
                return;

        if (sdio_uart_claim_func(port) != 0)
                return;

        if (I_IXOFF(tty)) {
                if (port->x_char) {
                        port->x_char = 0;
                } else {
                        port->x_char = START_CHAR(tty);
                        sdio_uart_start_tx(port);
                }
        }

        if (C_CRTSCTS(tty))
                sdio_uart_set_mctrl(port, TIOCM_RTS);

        sdio_uart_irq(port->func);
        sdio_uart_release_func(port);
}

static void sdio_uart_set_termios(struct tty_struct *tty,
                                                struct ktermios *old_termios)
{
        struct sdio_uart_port *port = tty->driver_data;
        unsigned int cflag = tty->termios.c_cflag;

        if (sdio_uart_claim_func(port) != 0)
                return;

        sdio_uart_change_speed(port, &tty->termios, old_termios);

        /* Handle transition to B0 status */
        if ((old_termios->c_cflag & CBAUD) && !(cflag & CBAUD))
                sdio_uart_clear_mctrl(port, TIOCM_RTS | TIOCM_DTR);

        /* Handle transition away from B0 status */
        if (!(old_termios->c_cflag & CBAUD) && (cflag & CBAUD)) {
                unsigned int mask = TIOCM_DTR;
                if (!(cflag & CRTSCTS) || !tty_throttled(tty))
                        mask |= TIOCM_RTS;
                sdio_uart_set_mctrl(port, mask);
        }

        /* Handle turning off CRTSCTS */
        if ((old_termios->c_cflag & CRTSCTS) && !(cflag & CRTSCTS)) {
                tty->hw_stopped = 0;
                sdio_uart_start_tx(port);
        }

        /* Handle turning on CRTSCTS */
        if (!(old_termios->c_cflag & CRTSCTS) && (cflag & CRTSCTS)) {
                if (!(sdio_uart_get_mctrl(port) & TIOCM_CTS)) {
                        tty->hw_stopped = 1;
                        sdio_uart_stop_tx(port);
                }
        }

        sdio_uart_release_func(port);
}

static int sdio_uart_break_ctl(struct tty_struct *tty, int break_state)
{
        struct sdio_uart_port *port = tty->driver_data;
        int result;

        result = sdio_uart_claim_func(port);
        if (result != 0)
                return result;

        if (break_state == -1)
                port->lcr |= UART_LCR_SBC;
        else
                port->lcr &= ~UART_LCR_SBC;
        sdio_out(port, UART_LCR, port->lcr);

        sdio_uart_release_func(port);
        return 0;
}

static int sdio_uart_tiocmget(struct tty_struct *tty)
{
        struct sdio_uart_port *port = tty->driver_data;
        int result;

        result = sdio_uart_claim_func(port);
        if (!result) {
                result = port->mctrl | sdio_uart_get_mctrl(port);
                sdio_uart_release_func(port);
        }

        return result;
}

static int sdio_uart_tiocmset(struct tty_struct *tty,
                              unsigned int set, unsigned int clear)
{
        struct sdio_uart_port *port = tty->driver_data;
        int result;

        result = sdio_uart_claim_func(port);
        if (!result) {
                sdio_uart_update_mctrl(port, set, clear);
                sdio_uart_release_func(port);
        }

        return result;
}

static int sdio_uart_proc_show(struct seq_file *m, void *v)
{
        int i;

        seq_printf(m, "serinfo:1.0 driver%s%s revision:%s\n",
                       "", "", "");
        for (i = 0; i < UART_NR; i++) {
                struct sdio_uart_port *port = sdio_uart_port_get(i);
                if (port) {
                        seq_printf(m, "%d: uart:SDIO", i);
                        if (capable(CAP_SYS_ADMIN)) {
                                seq_printf(m, " tx:%d rx:%d",
                                              port->icount.tx, port->icount.rx);
                                if (port->icount.frame)
                                        seq_printf(m, " fe:%d",
                                                      port->icount.frame);
                                if (port->icount.parity)
                                        seq_printf(m, " pe:%d",
                                                      port->icount.parity);
                                if (port->icount.brk)
                                        seq_printf(m, " brk:%d",
                                                      port->icount.brk);
                                if (port->icount.overrun)
                                        seq_printf(m, " oe:%d",
                                                      port->icount.overrun);
                                if (port->icount.cts)
                                        seq_printf(m, " cts:%d",
                                                      port->icount.cts);
                                if (port->icount.dsr)
                                        seq_printf(m, " dsr:%d",
                                                      port->icount.dsr);
                                if (port->icount.rng)
                                        seq_printf(m, " rng:%d",
                                                      port->icount.rng);
                                if (port->icount.dcd)
                                        seq_printf(m, " dcd:%d",
                                                      port->icount.dcd);
                        }
                        sdio_uart_port_put(port);

                        seq_putc(m, '\n');
                }
        }
        return 0;
}

static const struct tty_port_operations sdio_uart_port_ops = {
        .dtr_rts = uart_dtr_rts,
        .carrier_raised = uart_carrier_raised,
        .shutdown = sdio_uart_shutdown,
        .activate = sdio_uart_activate,
        .destruct = sdio_uart_port_destroy,
};

static const struct tty_operations sdio_uart_ops = {
        .open                   = sdio_uart_open,
        .close                  = sdio_uart_close,
        .write                  = sdio_uart_write,
        .write_room             = sdio_uart_write_room,
        .chars_in_buffer        = sdio_uart_chars_in_buffer,
        .send_xchar             = sdio_uart_send_xchar,
        .throttle               = sdio_uart_throttle,
        .unthrottle             = sdio_uart_unthrottle,
        .set_termios            = sdio_uart_set_termios,
        .hangup                 = sdio_uart_hangup,
        .break_ctl              = sdio_uart_break_ctl,
        .tiocmget               = sdio_uart_tiocmget,
        .tiocmset               = sdio_uart_tiocmset,
        .install                = sdio_uart_install,
        .cleanup                = sdio_uart_cleanup,
        .proc_show              = sdio_uart_proc_show,
};

static struct tty_driver *sdio_uart_tty_driver;

static int sdio_uart_probe(struct sdio_func *func,
                           const struct sdio_device_id *id)
{
        struct sdio_uart_port *port;
        int ret;

        port = kzalloc(sizeof(struct sdio_uart_port), GFP_KERNEL);
        if (!port)
                return -ENOMEM;

        if (func->class == SDIO_CLASS_UART) {
                pr_warn("%s: need info on UART class basic setup\n",
                        sdio_func_id(func));
                kfree(port);
                return -ENOSYS;
        } else if (func->class == SDIO_CLASS_GPS) {
                /*
                 * We need tuple 0x91.  It contains SUBTPL_SIOREG
                 * and SUBTPL_RCVCAPS.
                 */
                struct sdio_func_tuple *tpl;
                for (tpl = func->tuples; tpl; tpl = tpl->next) {
                        if (tpl->code != 0x91)
                                continue;
                        if (tpl->size < 10)
                                continue;
                        if (tpl->data[1] == 0)  /* SUBTPL_SIOREG */
                                break;
                }
                if (!tpl) {
                        pr_warn("%s: can't find tuple 0x91 subtuple 0 (SUBTPL_SIOREG) for GPS class\n",
                                sdio_func_id(func));
                        kfree(port);
                        return -EINVAL;
                }
                pr_debug("%s: Register ID = 0x%02x, Exp ID = 0x%02x\n",
                       sdio_func_id(func), tpl->data[2], tpl->data[3]);
                port->regs_offset = (tpl->data[4] << 0) |
                                    (tpl->data[5] << 8) |
                                    (tpl->data[6] << 16);
                pr_debug("%s: regs offset = 0x%x\n",
                       sdio_func_id(func), port->regs_offset);
                port->uartclk = tpl->data[7] * 115200;
                if (port->uartclk == 0)
                        port->uartclk = 115200;
                pr_debug("%s: clk %d baudcode %u 4800-div %u\n",
                       sdio_func_id(func), port->uartclk,
                       tpl->data[7], tpl->data[8] | (tpl->data[9] << 8));
        } else {
                kfree(port);
                return -EINVAL;
        }

        port->func = func;
        sdio_set_drvdata(func, port);
        tty_port_init(&port->port);
        port->port.ops = &sdio_uart_port_ops;

        ret = sdio_uart_add_port(port);
        if (ret) {
                kfree(port);
        } else {
                struct device *dev;
                dev = tty_port_register_device(&port->port,
                                sdio_uart_tty_driver, port->index, &func->dev);
                if (IS_ERR(dev)) {
                        sdio_uart_port_remove(port);
                        ret = PTR_ERR(dev);
                }
        }

        return ret;
}

static void sdio_uart_remove(struct sdio_func *func)
{
        struct sdio_uart_port *port = sdio_get_drvdata(func);

        tty_unregister_device(sdio_uart_tty_driver, port->index);
        sdio_uart_port_remove(port);
}

static const struct sdio_device_id sdio_uart_ids[] = {
        { SDIO_DEVICE_CLASS(SDIO_CLASS_UART)            },
        { SDIO_DEVICE_CLASS(SDIO_CLASS_GPS)             },
        { /* end: all zeroes */                         },
};

MODULE_DEVICE_TABLE(sdio, sdio_uart_ids);

static struct sdio_driver sdio_uart_driver = {
        .probe          = sdio_uart_probe,
        .remove         = sdio_uart_remove,
        .name           = "sdio_uart",
        .id_table       = sdio_uart_ids,
};

static int __init sdio_uart_init(void)
{
        int ret;
        struct tty_driver *tty_drv;

        sdio_uart_tty_driver = tty_drv = tty_alloc_driver(UART_NR,
                        TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV);
        if (IS_ERR(tty_drv))
                return PTR_ERR(tty_drv);

        tty_drv->driver_name = "sdio_uart";
        tty_drv->name =   "ttySDIO";
        tty_drv->major = 0;  /* dynamically allocated */
        tty_drv->minor_start = 0;
        tty_drv->type = TTY_DRIVER_TYPE_SERIAL;
        tty_drv->subtype = SERIAL_TYPE_NORMAL;
        tty_drv->init_termios = tty_std_termios;
        tty_drv->init_termios.c_cflag = B4800 | CS8 | CREAD | HUPCL | CLOCAL;
        tty_drv->init_termios.c_ispeed = 4800;
        tty_drv->init_termios.c_ospeed = 4800;
        tty_set_operations(tty_drv, &sdio_uart_ops);

        ret = tty_register_driver(tty_drv);
        if (ret)
                goto err1;

        ret = sdio_register_driver(&sdio_uart_driver);
        if (ret)
                goto err2;

        return 0;

err2:
        tty_unregister_driver(tty_drv);
err1:
        tty_driver_kref_put(tty_drv);
        return ret;
}

static void __exit sdio_uart_exit(void)
{
        sdio_unregister_driver(&sdio_uart_driver);
        tty_unregister_driver(sdio_uart_tty_driver);
        tty_driver_kref_put(sdio_uart_tty_driver);
}

module_init(sdio_uart_init);
module_exit(sdio_uart_exit);

MODULE_AUTHOR("Nicolas Pitre");
MODULE_LICENSE("GPL");