GNU Linux-libre 6.7.9-gnu

[releases.git] / drivers / tty / serial / serial_core.c

// SPDX-License-Identifier: GPL-2.0+
/*
 *  Driver core for serial ports
 *
 *  Based on drivers/char/serial.c, by Linus Torvalds, Theodore Ts'o.
 *
 *  Copyright 1999 ARM Limited
 *  Copyright (C) 2000-2001 Deep Blue Solutions Ltd.
 */
#include <linux/module.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/slab.h>
#include <linux/sched/signal.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/gpio/consumer.h>
#include <linux/kernel.h>
#include <linux/of.h>
#include <linux/pm_runtime.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/device.h>
#include <linux/serial.h> /* for serial_state and serial_icounter_struct */
#include <linux/serial_core.h>
#include <linux/sysrq.h>
#include <linux/delay.h>
#include <linux/mutex.h>
#include <linux/math64.h>
#include <linux/security.h>

#include <linux/irq.h>
#include <linux/uaccess.h>

#include "serial_base.h"

/*
 * This is used to lock changes in serial line configuration.
 */
static DEFINE_MUTEX(port_mutex);

/*
 * lockdep: port->lock is initialized in two places, but we
 *          want only one lock-class:
 */
static struct lock_class_key port_lock_key;

#define HIGH_BITS_OFFSET        ((sizeof(long)-sizeof(int))*8)

/*
 * Max time with active RTS before/after data is sent.
 */
#define RS485_MAX_RTS_DELAY     100 /* msecs */

static void uart_change_pm(struct uart_state *state,
                           enum uart_pm_state pm_state);

static void uart_port_shutdown(struct tty_port *port);

static int uart_dcd_enabled(struct uart_port *uport)
{
        return !!(uport->status & UPSTAT_DCD_ENABLE);
}

static inline struct uart_port *uart_port_ref(struct uart_state *state)
{
        if (atomic_add_unless(&state->refcount, 1, 0))
                return state->uart_port;
        return NULL;
}

static inline void uart_port_deref(struct uart_port *uport)
{
        if (atomic_dec_and_test(&uport->state->refcount))
                wake_up(&uport->state->remove_wait);
}

#define uart_port_lock(state, flags)                                    \
        ({                                                              \
                struct uart_port *__uport = uart_port_ref(state);       \
                if (__uport)                                            \
                        uart_port_lock_irqsave(__uport, &flags);        \
                __uport;                                                \
        })

#define uart_port_unlock(uport, flags)                                  \
        ({                                                              \
                struct uart_port *__uport = uport;                      \
                if (__uport) {                                          \
                        uart_port_unlock_irqrestore(__uport, flags);    \
                        uart_port_deref(__uport);                       \
                }                                                       \
        })

static inline struct uart_port *uart_port_check(struct uart_state *state)
{
        lockdep_assert_held(&state->port.mutex);
        return state->uart_port;
}

/**
 * uart_write_wakeup - schedule write processing
 * @port: port to be processed
 *
 * This routine is used by the interrupt handler to schedule processing in the
 * software interrupt portion of the driver. A driver is expected to call this
 * function when the number of characters in the transmit buffer have dropped
 * below a threshold.
 *
 * Locking: @port->lock should be held
 */
void uart_write_wakeup(struct uart_port *port)
{
        struct uart_state *state = port->state;
        /*
         * This means you called this function _after_ the port was
         * closed.  No cookie for you.
         */
        BUG_ON(!state);
        tty_port_tty_wakeup(&state->port);
}
EXPORT_SYMBOL(uart_write_wakeup);

static void uart_stop(struct tty_struct *tty)
{
        struct uart_state *state = tty->driver_data;
        struct uart_port *port;
        unsigned long flags;

        port = uart_port_lock(state, flags);
        if (port)
                port->ops->stop_tx(port);
        uart_port_unlock(port, flags);
}

static void __uart_start(struct uart_state *state)
{
        struct uart_port *port = state->uart_port;
        struct serial_port_device *port_dev;
        int err;

        if (!port || port->flags & UPF_DEAD || uart_tx_stopped(port))
                return;

        port_dev = port->port_dev;

        /* Increment the runtime PM usage count for the active check below */
        err = pm_runtime_get(&port_dev->dev);
        if (err < 0 && err != -EINPROGRESS) {
                pm_runtime_put_noidle(&port_dev->dev);
                return;
        }

        /*
         * Start TX if enabled, and kick runtime PM. If the device is not
         * enabled, serial_port_runtime_resume() calls start_tx() again
         * after enabling the device.
         */
        if (!pm_runtime_enabled(port->dev) || pm_runtime_active(port->dev))
                port->ops->start_tx(port);
        pm_runtime_mark_last_busy(&port_dev->dev);
        pm_runtime_put_autosuspend(&port_dev->dev);
}

static void uart_start(struct tty_struct *tty)
{
        struct uart_state *state = tty->driver_data;
        struct uart_port *port;
        unsigned long flags;

        port = uart_port_lock(state, flags);
        __uart_start(state);
        uart_port_unlock(port, flags);
}

static void
uart_update_mctrl(struct uart_port *port, unsigned int set, unsigned int clear)
{
        unsigned long flags;
        unsigned int old;

        uart_port_lock_irqsave(port, &flags);
        old = port->mctrl;
        port->mctrl = (old & ~clear) | set;
        if (old != port->mctrl && !(port->rs485.flags & SER_RS485_ENABLED))
                port->ops->set_mctrl(port, port->mctrl);
        uart_port_unlock_irqrestore(port, flags);
}

#define uart_set_mctrl(port, set)       uart_update_mctrl(port, set, 0)
#define uart_clear_mctrl(port, clear)   uart_update_mctrl(port, 0, clear)

static void uart_port_dtr_rts(struct uart_port *uport, bool active)
{
        if (active)
                uart_set_mctrl(uport, TIOCM_DTR | TIOCM_RTS);
        else
                uart_clear_mctrl(uport, TIOCM_DTR | TIOCM_RTS);
}

/* Caller holds port mutex */
static void uart_change_line_settings(struct tty_struct *tty, struct uart_state *state,
                                      const struct ktermios *old_termios)
{
        struct uart_port *uport = uart_port_check(state);
        struct ktermios *termios;
        bool old_hw_stopped;

        /*
         * If we have no tty, termios, or the port does not exist,
         * then we can't set the parameters for this port.
         */
        if (!tty || uport->type == PORT_UNKNOWN)
                return;

        termios = &tty->termios;
        uport->ops->set_termios(uport, termios, old_termios);

        /*
         * Set modem status enables based on termios cflag
         */
        uart_port_lock_irq(uport);
        if (termios->c_cflag & CRTSCTS)
                uport->status |= UPSTAT_CTS_ENABLE;
        else
                uport->status &= ~UPSTAT_CTS_ENABLE;

        if (termios->c_cflag & CLOCAL)
                uport->status &= ~UPSTAT_DCD_ENABLE;
        else
                uport->status |= UPSTAT_DCD_ENABLE;

        /* reset sw-assisted CTS flow control based on (possibly) new mode */
        old_hw_stopped = uport->hw_stopped;
        uport->hw_stopped = uart_softcts_mode(uport) &&
                            !(uport->ops->get_mctrl(uport) & TIOCM_CTS);
        if (uport->hw_stopped != old_hw_stopped) {
                if (!old_hw_stopped)
                        uport->ops->stop_tx(uport);
                else
                        __uart_start(state);
        }
        uart_port_unlock_irq(uport);
}

/*
 * Startup the port.  This will be called once per open.  All calls
 * will be serialised by the per-port mutex.
 */
static int uart_port_startup(struct tty_struct *tty, struct uart_state *state,
                             bool init_hw)
{
        struct uart_port *uport = uart_port_check(state);
        unsigned long flags;
        unsigned long page;
        int retval = 0;

        if (uport->type == PORT_UNKNOWN)
                return 1;

        /*
         * Make sure the device is in D0 state.
         */
        uart_change_pm(state, UART_PM_STATE_ON);

        /*
         * Initialise and allocate the transmit and temporary
         * buffer.
         */
        page = get_zeroed_page(GFP_KERNEL);
        if (!page)
                return -ENOMEM;

        uart_port_lock(state, flags);
        if (!state->xmit.buf) {
                state->xmit.buf = (unsigned char *) page;
                uart_circ_clear(&state->xmit);
                uart_port_unlock(uport, flags);
        } else {
                uart_port_unlock(uport, flags);
                /*
                 * Do not free() the page under the port lock, see
                 * uart_shutdown().
                 */
                free_page(page);
        }

        retval = uport->ops->startup(uport);
        if (retval == 0) {
                if (uart_console(uport) && uport->cons->cflag) {
                        tty->termios.c_cflag = uport->cons->cflag;
                        tty->termios.c_ispeed = uport->cons->ispeed;
                        tty->termios.c_ospeed = uport->cons->ospeed;
                        uport->cons->cflag = 0;
                        uport->cons->ispeed = 0;
                        uport->cons->ospeed = 0;
                }
                /*
                 * Initialise the hardware port settings.
                 */
                uart_change_line_settings(tty, state, NULL);

                /*
                 * Setup the RTS and DTR signals once the
                 * port is open and ready to respond.
                 */
                if (init_hw && C_BAUD(tty))
                        uart_port_dtr_rts(uport, true);
        }

        /*
         * This is to allow setserial on this port. People may want to set
         * port/irq/type and then reconfigure the port properly if it failed
         * now.
         */
        if (retval && capable(CAP_SYS_ADMIN))
                return 1;

        return retval;
}

static int uart_startup(struct tty_struct *tty, struct uart_state *state,
                        bool init_hw)
{
        struct tty_port *port = &state->port;
        int retval;

        if (tty_port_initialized(port))
                return 0;

        retval = uart_port_startup(tty, state, init_hw);
        if (retval)
                set_bit(TTY_IO_ERROR, &tty->flags);

        return retval;
}

/*
 * This routine will shutdown a serial port; interrupts are disabled, and
 * DTR is dropped if the hangup on close termio flag is on.  Calls to
 * uart_shutdown are serialised by the per-port semaphore.
 *
 * uport == NULL if uart_port has already been removed
 */
static void uart_shutdown(struct tty_struct *tty, struct uart_state *state)
{
        struct uart_port *uport = uart_port_check(state);
        struct tty_port *port = &state->port;
        unsigned long flags;
        char *xmit_buf = NULL;

        /*
         * Set the TTY IO error marker
         */
        if (tty)
                set_bit(TTY_IO_ERROR, &tty->flags);

        if (tty_port_initialized(port)) {
                tty_port_set_initialized(port, false);

                /*
                 * Turn off DTR and RTS early.
                 */
                if (uport && uart_console(uport) && tty) {
                        uport->cons->cflag = tty->termios.c_cflag;
                        uport->cons->ispeed = tty->termios.c_ispeed;
                        uport->cons->ospeed = tty->termios.c_ospeed;
                }

                if (!tty || C_HUPCL(tty))
                        uart_port_dtr_rts(uport, false);

                uart_port_shutdown(port);
        }

        /*
         * It's possible for shutdown to be called after suspend if we get
         * a DCD drop (hangup) at just the right time.  Clear suspended bit so
         * we don't try to resume a port that has been shutdown.
         */
        tty_port_set_suspended(port, false);

        /*
         * Do not free() the transmit buffer page under the port lock since
         * this can create various circular locking scenarios. For instance,
         * console driver may need to allocate/free a debug object, which
         * can endup in printk() recursion.
         */
        uart_port_lock(state, flags);
        xmit_buf = state->xmit.buf;
        state->xmit.buf = NULL;
        uart_port_unlock(uport, flags);

        free_page((unsigned long)xmit_buf);
}

/**
 * uart_update_timeout - update per-port frame timing information
 * @port: uart_port structure describing the port
 * @cflag: termios cflag value
 * @baud: speed of the port
 *
 * Set the @port frame timing information from which the FIFO timeout value is
 * derived. The @cflag value should reflect the actual hardware settings as
 * number of bits, parity, stop bits and baud rate is taken into account here.
 *
 * Locking: caller is expected to take @port->lock
 */
void
uart_update_timeout(struct uart_port *port, unsigned int cflag,
                    unsigned int baud)
{
        unsigned int size = tty_get_frame_size(cflag);
        u64 frame_time;

        frame_time = (u64)size * NSEC_PER_SEC;
        port->frame_time = DIV64_U64_ROUND_UP(frame_time, baud);
}
EXPORT_SYMBOL(uart_update_timeout);

/**
 * uart_get_baud_rate - return baud rate for a particular port
 * @port: uart_port structure describing the port in question.
 * @termios: desired termios settings
 * @old: old termios (or %NULL)
 * @min: minimum acceptable baud rate
 * @max: maximum acceptable baud rate
 *
 * Decode the termios structure into a numeric baud rate, taking account of the
 * magic 38400 baud rate (with spd_* flags), and mapping the %B0 rate to 9600
 * baud.
 *
 * If the new baud rate is invalid, try the @old termios setting. If it's still
 * invalid, we try 9600 baud. If that is also invalid 0 is returned.
 *
 * The @termios structure is updated to reflect the baud rate we're actually
 * going to be using. Don't do this for the case where B0 is requested ("hang
 * up").
 *
 * Locking: caller dependent
 */
unsigned int
uart_get_baud_rate(struct uart_port *port, struct ktermios *termios,
                   const struct ktermios *old, unsigned int min, unsigned int max)
{
        unsigned int try;
        unsigned int baud;
        unsigned int altbaud;
        int hung_up = 0;
        upf_t flags = port->flags & UPF_SPD_MASK;

        switch (flags) {
        case UPF_SPD_HI:
                altbaud = 57600;
                break;
        case UPF_SPD_VHI:
                altbaud = 115200;
                break;
        case UPF_SPD_SHI:
                altbaud = 230400;
                break;
        case UPF_SPD_WARP:
                altbaud = 460800;
                break;
        default:
                altbaud = 38400;
                break;
        }

        for (try = 0; try < 2; try++) {
                baud = tty_termios_baud_rate(termios);

                /*
                 * The spd_hi, spd_vhi, spd_shi, spd_warp kludge...
                 * Die! Die! Die!
                 */
                if (try == 0 && baud == 38400)
                        baud = altbaud;

                /*
                 * Special case: B0 rate.
                 */
                if (baud == 0) {
                        hung_up = 1;
                        baud = 9600;
                }

                if (baud >= min && baud <= max)
                        return baud;

                /*
                 * Oops, the quotient was zero.  Try again with
                 * the old baud rate if possible.
                 */
                termios->c_cflag &= ~CBAUD;
                if (old) {
                        baud = tty_termios_baud_rate(old);
                        if (!hung_up)
                                tty_termios_encode_baud_rate(termios,
                                                                baud, baud);
                        old = NULL;
                        continue;
                }

                /*
                 * As a last resort, if the range cannot be met then clip to
                 * the nearest chip supported rate.
                 */
                if (!hung_up) {
                        if (baud <= min)
                                tty_termios_encode_baud_rate(termios,
                                                        min + 1, min + 1);
                        else
                                tty_termios_encode_baud_rate(termios,
                                                        max - 1, max - 1);
                }
        }
        return 0;
}
EXPORT_SYMBOL(uart_get_baud_rate);

/**
 * uart_get_divisor - return uart clock divisor
 * @port: uart_port structure describing the port
 * @baud: desired baud rate
 *
 * Calculate the divisor (baud_base / baud) for the specified @baud,
 * appropriately rounded.
 *
 * If 38400 baud and custom divisor is selected, return the custom divisor
 * instead.
 *
 * Locking: caller dependent
 */
unsigned int
uart_get_divisor(struct uart_port *port, unsigned int baud)
{
        unsigned int quot;

        /*
         * Old custom speed handling.
         */
        if (baud == 38400 && (port->flags & UPF_SPD_MASK) == UPF_SPD_CUST)
                quot = port->custom_divisor;
        else
                quot = DIV_ROUND_CLOSEST(port->uartclk, 16 * baud);

        return quot;
}
EXPORT_SYMBOL(uart_get_divisor);

static int uart_put_char(struct tty_struct *tty, u8 c)
{
        struct uart_state *state = tty->driver_data;
        struct uart_port *port;
        struct circ_buf *circ;
        unsigned long flags;
        int ret = 0;

        circ = &state->xmit;
        port = uart_port_lock(state, flags);
        if (!circ->buf) {
                uart_port_unlock(port, flags);
                return 0;
        }

        if (port && uart_circ_chars_free(circ) != 0) {
                circ->buf[circ->head] = c;
                circ->head = (circ->head + 1) & (UART_XMIT_SIZE - 1);
                ret = 1;
        }
        uart_port_unlock(port, flags);
        return ret;
}

static void uart_flush_chars(struct tty_struct *tty)
{
        uart_start(tty);
}

static ssize_t uart_write(struct tty_struct *tty, const u8 *buf, size_t count)
{
        struct uart_state *state = tty->driver_data;
        struct uart_port *port;
        struct circ_buf *circ;
        unsigned long flags;
        int c, ret = 0;

        /*
         * This means you called this function _after_ the port was
         * closed.  No cookie for you.
         */
        if (WARN_ON(!state))
                return -EL3HLT;

        port = uart_port_lock(state, flags);
        circ = &state->xmit;
        if (!circ->buf) {
                uart_port_unlock(port, flags);
                return 0;
        }

        while (port) {
                c = CIRC_SPACE_TO_END(circ->head, circ->tail, UART_XMIT_SIZE);
                if (count < c)
                        c = count;
                if (c <= 0)
                        break;
                memcpy(circ->buf + circ->head, buf, c);
                circ->head = (circ->head + c) & (UART_XMIT_SIZE - 1);
                buf += c;
                count -= c;
                ret += c;
        }

        __uart_start(state);
        uart_port_unlock(port, flags);
        return ret;
}

static unsigned int uart_write_room(struct tty_struct *tty)
{
        struct uart_state *state = tty->driver_data;
        struct uart_port *port;
        unsigned long flags;
        unsigned int ret;

        port = uart_port_lock(state, flags);
        ret = uart_circ_chars_free(&state->xmit);
        uart_port_unlock(port, flags);
        return ret;
}

static unsigned int uart_chars_in_buffer(struct tty_struct *tty)
{
        struct uart_state *state = tty->driver_data;
        struct uart_port *port;
        unsigned long flags;
        unsigned int ret;

        port = uart_port_lock(state, flags);
        ret = uart_circ_chars_pending(&state->xmit);
        uart_port_unlock(port, flags);
        return ret;
}

static void uart_flush_buffer(struct tty_struct *tty)
{
        struct uart_state *state = tty->driver_data;
        struct uart_port *port;
        unsigned long flags;

        /*
         * This means you called this function _after_ the port was
         * closed.  No cookie for you.
         */
        if (WARN_ON(!state))
                return;

        pr_debug("uart_flush_buffer(%d) called\n", tty->index);

        port = uart_port_lock(state, flags);
        if (!port)
                return;
        uart_circ_clear(&state->xmit);
        if (port->ops->flush_buffer)
                port->ops->flush_buffer(port);
        uart_port_unlock(port, flags);
        tty_port_tty_wakeup(&state->port);
}

/*
 * This function performs low-level write of high-priority XON/XOFF
 * character and accounting for it.
 *
 * Requires uart_port to implement .serial_out().
 */
void uart_xchar_out(struct uart_port *uport, int offset)
{
        serial_port_out(uport, offset, uport->x_char);
        uport->icount.tx++;
        uport->x_char = 0;
}
EXPORT_SYMBOL_GPL(uart_xchar_out);

/*
 * This function is used to send a high-priority XON/XOFF character to
 * the device
 */
static void uart_send_xchar(struct tty_struct *tty, char ch)
{
        struct uart_state *state = tty->driver_data;
        struct uart_port *port;
        unsigned long flags;

        port = uart_port_ref(state);
        if (!port)
                return;

        if (port->ops->send_xchar)
                port->ops->send_xchar(port, ch);
        else {
                uart_port_lock_irqsave(port, &flags);
                port->x_char = ch;
                if (ch)
                        port->ops->start_tx(port);
                uart_port_unlock_irqrestore(port, flags);
        }
        uart_port_deref(port);
}

static void uart_throttle(struct tty_struct *tty)
{
        struct uart_state *state = tty->driver_data;
        upstat_t mask = UPSTAT_SYNC_FIFO;
        struct uart_port *port;

        port = uart_port_ref(state);
        if (!port)
                return;

        if (I_IXOFF(tty))
                mask |= UPSTAT_AUTOXOFF;
        if (C_CRTSCTS(tty))
                mask |= UPSTAT_AUTORTS;

        if (port->status & mask) {
                port->ops->throttle(port);
                mask &= ~port->status;
        }

        if (mask & UPSTAT_AUTORTS)
                uart_clear_mctrl(port, TIOCM_RTS);

        if (mask & UPSTAT_AUTOXOFF)
                uart_send_xchar(tty, STOP_CHAR(tty));

        uart_port_deref(port);
}

static void uart_unthrottle(struct tty_struct *tty)
{
        struct uart_state *state = tty->driver_data;
        upstat_t mask = UPSTAT_SYNC_FIFO;
        struct uart_port *port;

        port = uart_port_ref(state);
        if (!port)
                return;

        if (I_IXOFF(tty))
                mask |= UPSTAT_AUTOXOFF;
        if (C_CRTSCTS(tty))
                mask |= UPSTAT_AUTORTS;

        if (port->status & mask) {
                port->ops->unthrottle(port);
                mask &= ~port->status;
        }

        if (mask & UPSTAT_AUTORTS)
                uart_set_mctrl(port, TIOCM_RTS);

        if (mask & UPSTAT_AUTOXOFF)
                uart_send_xchar(tty, START_CHAR(tty));

        uart_port_deref(port);
}

static int uart_get_info(struct tty_port *port, struct serial_struct *retinfo)
{
        struct uart_state *state = container_of(port, struct uart_state, port);
        struct uart_port *uport;
        int ret = -ENODEV;

        /* Initialize structure in case we error out later to prevent any stack info leakage. */
        *retinfo = (struct serial_struct){};

        /*
         * Ensure the state we copy is consistent and no hardware changes
         * occur as we go
         */
        mutex_lock(&port->mutex);
        uport = uart_port_check(state);
        if (!uport)
                goto out;

        retinfo->type       = uport->type;
        retinfo->line       = uport->line;
        retinfo->port       = uport->iobase;
        if (HIGH_BITS_OFFSET)
                retinfo->port_high = (long) uport->iobase >> HIGH_BITS_OFFSET;
        retinfo->irq                = uport->irq;
        retinfo->flags      = (__force int)uport->flags;
        retinfo->xmit_fifo_size  = uport->fifosize;
        retinfo->baud_base          = uport->uartclk / 16;
        retinfo->close_delay        = jiffies_to_msecs(port->close_delay) / 10;
        retinfo->closing_wait    = port->closing_wait == ASYNC_CLOSING_WAIT_NONE ?
                                ASYNC_CLOSING_WAIT_NONE :
                                jiffies_to_msecs(port->closing_wait) / 10;
        retinfo->custom_divisor  = uport->custom_divisor;
        retinfo->hub6       = uport->hub6;
        retinfo->io_type         = uport->iotype;
        retinfo->iomem_reg_shift = uport->regshift;
        retinfo->iomem_base      = (void *)(unsigned long)uport->mapbase;

        ret = 0;
out:
        mutex_unlock(&port->mutex);
        return ret;
}

static int uart_get_info_user(struct tty_struct *tty,
                         struct serial_struct *ss)
{
        struct uart_state *state = tty->driver_data;
        struct tty_port *port = &state->port;

        return uart_get_info(port, ss) < 0 ? -EIO : 0;
}

static int uart_set_info(struct tty_struct *tty, struct tty_port *port,
                         struct uart_state *state,
                         struct serial_struct *new_info)
{
        struct uart_port *uport = uart_port_check(state);
        unsigned long new_port;
        unsigned int change_irq, change_port, closing_wait;
        unsigned int old_custom_divisor, close_delay;
        upf_t old_flags, new_flags;
        int retval = 0;

        if (!uport)
                return -EIO;

        new_port = new_info->port;
        if (HIGH_BITS_OFFSET)
                new_port += (unsigned long) new_info->port_high << HIGH_BITS_OFFSET;

        new_info->irq = irq_canonicalize(new_info->irq);
        close_delay = msecs_to_jiffies(new_info->close_delay * 10);
        closing_wait = new_info->closing_wait == ASYNC_CLOSING_WAIT_NONE ?
                        ASYNC_CLOSING_WAIT_NONE :
                        msecs_to_jiffies(new_info->closing_wait * 10);


        change_irq  = !(uport->flags & UPF_FIXED_PORT)
                && new_info->irq != uport->irq;

        /*
         * Since changing the 'type' of the port changes its resource
         * allocations, we should treat type changes the same as
         * IO port changes.
         */
        change_port = !(uport->flags & UPF_FIXED_PORT)
                && (new_port != uport->iobase ||
                    (unsigned long)new_info->iomem_base != uport->mapbase ||
                    new_info->hub6 != uport->hub6 ||
                    new_info->io_type != uport->iotype ||
                    new_info->iomem_reg_shift != uport->regshift ||
                    new_info->type != uport->type);

        old_flags = uport->flags;
        new_flags = (__force upf_t)new_info->flags;
        old_custom_divisor = uport->custom_divisor;

        if (!capable(CAP_SYS_ADMIN)) {
                retval = -EPERM;
                if (change_irq || change_port ||
                    (new_info->baud_base != uport->uartclk / 16) ||
                    (close_delay != port->close_delay) ||
                    (closing_wait != port->closing_wait) ||
                    (new_info->xmit_fifo_size &&
                     new_info->xmit_fifo_size != uport->fifosize) ||
                    (((new_flags ^ old_flags) & ~UPF_USR_MASK) != 0))
                        goto exit;
                uport->flags = ((uport->flags & ~UPF_USR_MASK) |
                               (new_flags & UPF_USR_MASK));
                uport->custom_divisor = new_info->custom_divisor;
                goto check_and_exit;
        }

        if (change_irq || change_port) {
                retval = security_locked_down(LOCKDOWN_TIOCSSERIAL);
                if (retval)
                        goto exit;
        }

        /*
         * Ask the low level driver to verify the settings.
         */
        if (uport->ops->verify_port)
                retval = uport->ops->verify_port(uport, new_info);

        if ((new_info->irq >= nr_irqs) || (new_info->irq < 0) ||
            (new_info->baud_base < 9600))
                retval = -EINVAL;

        if (retval)
                goto exit;

        if (change_port || change_irq) {
                retval = -EBUSY;

                /*
                 * Make sure that we are the sole user of this port.
                 */
                if (tty_port_users(port) > 1)
                        goto exit;

                /*
                 * We need to shutdown the serial port at the old
                 * port/type/irq combination.
                 */
                uart_shutdown(tty, state);
        }

        if (change_port) {
                unsigned long old_iobase, old_mapbase;
                unsigned int old_type, old_iotype, old_hub6, old_shift;

                old_iobase = uport->iobase;
                old_mapbase = uport->mapbase;
                old_type = uport->type;
                old_hub6 = uport->hub6;
                old_iotype = uport->iotype;
                old_shift = uport->regshift;

                /*
                 * Free and release old regions
                 */
                if (old_type != PORT_UNKNOWN && uport->ops->release_port)
                        uport->ops->release_port(uport);

                uport->iobase = new_port;
                uport->type = new_info->type;
                uport->hub6 = new_info->hub6;
                uport->iotype = new_info->io_type;
                uport->regshift = new_info->iomem_reg_shift;
                uport->mapbase = (unsigned long)new_info->iomem_base;

                /*
                 * Claim and map the new regions
                 */
                if (uport->type != PORT_UNKNOWN && uport->ops->request_port) {
                        retval = uport->ops->request_port(uport);
                } else {
                        /* Always success - Jean II */
                        retval = 0;
                }

                /*
                 * If we fail to request resources for the
                 * new port, try to restore the old settings.
                 */
                if (retval) {
                        uport->iobase = old_iobase;
                        uport->type = old_type;
                        uport->hub6 = old_hub6;
                        uport->iotype = old_iotype;
                        uport->regshift = old_shift;
                        uport->mapbase = old_mapbase;

                        if (old_type != PORT_UNKNOWN) {
                                retval = uport->ops->request_port(uport);
                                /*
                                 * If we failed to restore the old settings,
                                 * we fail like this.
                                 */
                                if (retval)
                                        uport->type = PORT_UNKNOWN;

                                /*
                                 * We failed anyway.
                                 */
                                retval = -EBUSY;
                        }

                        /* Added to return the correct error -Ram Gupta */
                        goto exit;
                }
        }

        if (change_irq)
                uport->irq      = new_info->irq;
        if (!(uport->flags & UPF_FIXED_PORT))
                uport->uartclk  = new_info->baud_base * 16;
        uport->flags            = (uport->flags & ~UPF_CHANGE_MASK) |
                                 (new_flags & UPF_CHANGE_MASK);
        uport->custom_divisor   = new_info->custom_divisor;
        port->close_delay     = close_delay;
        port->closing_wait    = closing_wait;
        if (new_info->xmit_fifo_size)
                uport->fifosize = new_info->xmit_fifo_size;

 check_and_exit:
        retval = 0;
        if (uport->type == PORT_UNKNOWN)
                goto exit;
        if (tty_port_initialized(port)) {
                if (((old_flags ^ uport->flags) & UPF_SPD_MASK) ||
                    old_custom_divisor != uport->custom_divisor) {
                        /*
                         * If they're setting up a custom divisor or speed,
                         * instead of clearing it, then bitch about it.
                         */
                        if (uport->flags & UPF_SPD_MASK) {
                                dev_notice_ratelimited(uport->dev,
                                       "%s sets custom speed on %s. This is deprecated.\n",
                                      current->comm,
                                      tty_name(port->tty));
                        }
                        uart_change_line_settings(tty, state, NULL);
                }
        } else {
                retval = uart_startup(tty, state, true);
                if (retval == 0)
                        tty_port_set_initialized(port, true);
                if (retval > 0)
                        retval = 0;
        }
 exit:
        return retval;
}

static int uart_set_info_user(struct tty_struct *tty, struct serial_struct *ss)
{
        struct uart_state *state = tty->driver_data;
        struct tty_port *port = &state->port;
        int retval;

        down_write(&tty->termios_rwsem);
        /*
         * This semaphore protects port->count.  It is also
         * very useful to prevent opens.  Also, take the
         * port configuration semaphore to make sure that a
         * module insertion/removal doesn't change anything
         * under us.
         */
        mutex_lock(&port->mutex);
        retval = uart_set_info(tty, port, state, ss);
        mutex_unlock(&port->mutex);
        up_write(&tty->termios_rwsem);
        return retval;
}

/**
 * uart_get_lsr_info - get line status register info
 * @tty: tty associated with the UART
 * @state: UART being queried
 * @value: returned modem value
 */
static int uart_get_lsr_info(struct tty_struct *tty,
                        struct uart_state *state, unsigned int __user *value)
{
        struct uart_port *uport = uart_port_check(state);
        unsigned int result;

        result = uport->ops->tx_empty(uport);

        /*
         * If we're about to load something into the transmit
         * register, we'll pretend the transmitter isn't empty to
         * avoid a race condition (depending on when the transmit
         * interrupt happens).
         */
        if (uport->x_char ||
            ((uart_circ_chars_pending(&state->xmit) > 0) &&
             !uart_tx_stopped(uport)))
                result &= ~TIOCSER_TEMT;

        return put_user(result, value);
}

static int uart_tiocmget(struct tty_struct *tty)
{
        struct uart_state *state = tty->driver_data;
        struct tty_port *port = &state->port;
        struct uart_port *uport;
        int result = -EIO;

        mutex_lock(&port->mutex);
        uport = uart_port_check(state);
        if (!uport)
                goto out;

        if (!tty_io_error(tty)) {
                uart_port_lock_irq(uport);
                result = uport->mctrl;
                result |= uport->ops->get_mctrl(uport);
                uart_port_unlock_irq(uport);
        }
out:
        mutex_unlock(&port->mutex);
        return result;
}

static int
uart_tiocmset(struct tty_struct *tty, unsigned int set, unsigned int clear)
{
        struct uart_state *state = tty->driver_data;
        struct tty_port *port = &state->port;
        struct uart_port *uport;
        int ret = -EIO;

        mutex_lock(&port->mutex);
        uport = uart_port_check(state);
        if (!uport)
                goto out;

        if (!tty_io_error(tty)) {
                uart_update_mctrl(uport, set, clear);
                ret = 0;
        }
out:
        mutex_unlock(&port->mutex);
        return ret;
}

static int uart_break_ctl(struct tty_struct *tty, int break_state)
{
        struct uart_state *state = tty->driver_data;
        struct tty_port *port = &state->port;
        struct uart_port *uport;
        int ret = -EIO;

        mutex_lock(&port->mutex);
        uport = uart_port_check(state);
        if (!uport)
                goto out;

        if (uport->type != PORT_UNKNOWN && uport->ops->break_ctl)
                uport->ops->break_ctl(uport, break_state);
        ret = 0;
out:
        mutex_unlock(&port->mutex);
        return ret;
}

static int uart_do_autoconfig(struct tty_struct *tty, struct uart_state *state)
{
        struct tty_port *port = &state->port;
        struct uart_port *uport;
        int flags, ret;

        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;

        /*
         * Take the per-port semaphore.  This prevents count from
         * changing, and hence any extra opens of the port while
         * we're auto-configuring.
         */
        if (mutex_lock_interruptible(&port->mutex))
                return -ERESTARTSYS;

        uport = uart_port_check(state);
        if (!uport) {
                ret = -EIO;
                goto out;
        }

        ret = -EBUSY;
        if (tty_port_users(port) == 1) {
                uart_shutdown(tty, state);

                /*
                 * If we already have a port type configured,
                 * we must release its resources.
                 */
                if (uport->type != PORT_UNKNOWN && uport->ops->release_port)
                        uport->ops->release_port(uport);

                flags = UART_CONFIG_TYPE;
                if (uport->flags & UPF_AUTO_IRQ)
                        flags |= UART_CONFIG_IRQ;

                /*
                 * This will claim the ports resources if
                 * a port is found.
                 */
                uport->ops->config_port(uport, flags);

                ret = uart_startup(tty, state, true);
                if (ret == 0)
                        tty_port_set_initialized(port, true);
                if (ret > 0)
                        ret = 0;
        }
out:
        mutex_unlock(&port->mutex);
        return ret;
}

static void uart_enable_ms(struct uart_port *uport)
{
        /*
         * Force modem status interrupts on
         */
        if (uport->ops->enable_ms)
                uport->ops->enable_ms(uport);
}

/*
 * Wait for any of the 4 modem inputs (DCD,RI,DSR,CTS) to change
 * - mask passed in arg for lines of interest
 *   (use |'ed TIOCM_RNG/DSR/CD/CTS for masking)
 * Caller should use TIOCGICOUNT to see which one it was
 *
 * FIXME: This wants extracting into a common all driver implementation
 * of TIOCMWAIT using tty_port.
 */
static int uart_wait_modem_status(struct uart_state *state, unsigned long arg)
{
        struct uart_port *uport;
        struct tty_port *port = &state->port;
        DECLARE_WAITQUEUE(wait, current);
        struct uart_icount cprev, cnow;
        int ret;

        /*
         * note the counters on entry
         */
        uport = uart_port_ref(state);
        if (!uport)
                return -EIO;
        uart_port_lock_irq(uport);
        memcpy(&cprev, &uport->icount, sizeof(struct uart_icount));
        uart_enable_ms(uport);
        uart_port_unlock_irq(uport);

        add_wait_queue(&port->delta_msr_wait, &wait);
        for (;;) {
                uart_port_lock_irq(uport);
                memcpy(&cnow, &uport->icount, sizeof(struct uart_icount));
                uart_port_unlock_irq(uport);

                set_current_state(TASK_INTERRUPTIBLE);

                if (((arg & TIOCM_RNG) && (cnow.rng != cprev.rng)) ||
                    ((arg & TIOCM_DSR) && (cnow.dsr != cprev.dsr)) ||
                    ((arg & TIOCM_CD)  && (cnow.dcd != cprev.dcd)) ||
                    ((arg & TIOCM_CTS) && (cnow.cts != cprev.cts))) {
                        ret = 0;
                        break;
                }

                schedule();

                /* see if a signal did it */
                if (signal_pending(current)) {
                        ret = -ERESTARTSYS;
                        break;
                }

                cprev = cnow;
        }
        __set_current_state(TASK_RUNNING);
        remove_wait_queue(&port->delta_msr_wait, &wait);
        uart_port_deref(uport);

        return ret;
}

/*
 * Get counter of input serial line interrupts (DCD,RI,DSR,CTS)
 * Return: write counters to the user passed counter struct
 * NB: both 1->0 and 0->1 transitions are counted except for
 *     RI where only 0->1 is counted.
 */
static int uart_get_icount(struct tty_struct *tty,
                          struct serial_icounter_struct *icount)
{
        struct uart_state *state = tty->driver_data;
        struct uart_icount cnow;
        struct uart_port *uport;

        uport = uart_port_ref(state);
        if (!uport)
                return -EIO;
        uart_port_lock_irq(uport);
        memcpy(&cnow, &uport->icount, sizeof(struct uart_icount));
        uart_port_unlock_irq(uport);
        uart_port_deref(uport);

        icount->cts         = cnow.cts;
        icount->dsr         = cnow.dsr;
        icount->rng         = cnow.rng;
        icount->dcd         = cnow.dcd;
        icount->rx          = cnow.rx;
        icount->tx          = cnow.tx;
        icount->frame       = cnow.frame;
        icount->overrun     = cnow.overrun;
        icount->parity      = cnow.parity;
        icount->brk         = cnow.brk;
        icount->buf_overrun = cnow.buf_overrun;

        return 0;
}

#define SER_RS485_LEGACY_FLAGS  (SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | \
                                 SER_RS485_RTS_AFTER_SEND | SER_RS485_RX_DURING_TX | \
                                 SER_RS485_TERMINATE_BUS)

static int uart_check_rs485_flags(struct uart_port *port, struct serial_rs485 *rs485)
{
        u32 flags = rs485->flags;

        /* Don't return -EINVAL for unsupported legacy flags */
        flags &= ~SER_RS485_LEGACY_FLAGS;

        /*
         * For any bit outside of the legacy ones that is not supported by
         * the driver, return -EINVAL.
         */
        if (flags & ~port->rs485_supported.flags)
                return -EINVAL;

        /* Asking for address w/o addressing mode? */
        if (!(rs485->flags & SER_RS485_ADDRB) &&
            (rs485->flags & (SER_RS485_ADDR_RECV|SER_RS485_ADDR_DEST)))
                return -EINVAL;

        /* Address given but not enabled? */
        if (!(rs485->flags & SER_RS485_ADDR_RECV) && rs485->addr_recv)
                return -EINVAL;
        if (!(rs485->flags & SER_RS485_ADDR_DEST) && rs485->addr_dest)
                return -EINVAL;

        return 0;
}

static void uart_sanitize_serial_rs485_delays(struct uart_port *port,
                                              struct serial_rs485 *rs485)
{
        if (!port->rs485_supported.delay_rts_before_send) {
                if (rs485->delay_rts_before_send) {
                        dev_warn_ratelimited(port->dev,
                                "%s (%d): RTS delay before sending not supported\n",
                                port->name, port->line);
                }
                rs485->delay_rts_before_send = 0;
        } else if (rs485->delay_rts_before_send > RS485_MAX_RTS_DELAY) {
                rs485->delay_rts_before_send = RS485_MAX_RTS_DELAY;
                dev_warn_ratelimited(port->dev,
                        "%s (%d): RTS delay before sending clamped to %u ms\n",
                        port->name, port->line, rs485->delay_rts_before_send);
        }

        if (!port->rs485_supported.delay_rts_after_send) {
                if (rs485->delay_rts_after_send) {
                        dev_warn_ratelimited(port->dev,
                                "%s (%d): RTS delay after sending not supported\n",
                                port->name, port->line);
                }
                rs485->delay_rts_after_send = 0;
        } else if (rs485->delay_rts_after_send > RS485_MAX_RTS_DELAY) {
                rs485->delay_rts_after_send = RS485_MAX_RTS_DELAY;
                dev_warn_ratelimited(port->dev,
                        "%s (%d): RTS delay after sending clamped to %u ms\n",
                        port->name, port->line, rs485->delay_rts_after_send);
        }
}

static void uart_sanitize_serial_rs485(struct uart_port *port, struct serial_rs485 *rs485)
{
        u32 supported_flags = port->rs485_supported.flags;

        if (!(rs485->flags & SER_RS485_ENABLED)) {
                memset(rs485, 0, sizeof(*rs485));
                return;
        }

        rs485->flags &= supported_flags;

        /* Pick sane settings if the user hasn't */
        if (!(rs485->flags & SER_RS485_RTS_ON_SEND) ==
            !(rs485->flags & SER_RS485_RTS_AFTER_SEND)) {
                if (supported_flags & SER_RS485_RTS_ON_SEND) {
                        rs485->flags |= SER_RS485_RTS_ON_SEND;
                        rs485->flags &= ~SER_RS485_RTS_AFTER_SEND;

                        dev_warn_ratelimited(port->dev,
                                "%s (%d): invalid RTS setting, using RTS_ON_SEND instead\n",
                                port->name, port->line);
                } else {
                        rs485->flags |= SER_RS485_RTS_AFTER_SEND;
                        rs485->flags &= ~SER_RS485_RTS_ON_SEND;

                        dev_warn_ratelimited(port->dev,
                                "%s (%d): invalid RTS setting, using RTS_AFTER_SEND instead\n",
                                port->name, port->line);
                }
        }

        uart_sanitize_serial_rs485_delays(port, rs485);

        /* Return clean padding area to userspace */
        memset(rs485->padding0, 0, sizeof(rs485->padding0));
        memset(rs485->padding1, 0, sizeof(rs485->padding1));
}

static void uart_set_rs485_termination(struct uart_port *port,
                                       const struct serial_rs485 *rs485)
{
        if (!(rs485->flags & SER_RS485_ENABLED))
                return;

        gpiod_set_value_cansleep(port->rs485_term_gpio,
                                 !!(rs485->flags & SER_RS485_TERMINATE_BUS));
}

static void uart_set_rs485_rx_during_tx(struct uart_port *port,
                                        const struct serial_rs485 *rs485)
{
        if (!(rs485->flags & SER_RS485_ENABLED))
                return;

        gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio,
                                 !!(rs485->flags & SER_RS485_RX_DURING_TX));
}

static int uart_rs485_config(struct uart_port *port)
{
        struct serial_rs485 *rs485 = &port->rs485;
        unsigned long flags;
        int ret;

        if (!(rs485->flags & SER_RS485_ENABLED))
                return 0;

        uart_sanitize_serial_rs485(port, rs485);
        uart_set_rs485_termination(port, rs485);
        uart_set_rs485_rx_during_tx(port, rs485);

        uart_port_lock_irqsave(port, &flags);
        ret = port->rs485_config(port, NULL, rs485);
        uart_port_unlock_irqrestore(port, flags);
        if (ret) {
                memset(rs485, 0, sizeof(*rs485));
                /* unset GPIOs */
                gpiod_set_value_cansleep(port->rs485_term_gpio, 0);
                gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio, 0);
        }

        return ret;
}

static int uart_get_rs485_config(struct uart_port *port,
                         struct serial_rs485 __user *rs485)
{
        unsigned long flags;
        struct serial_rs485 aux;

        uart_port_lock_irqsave(port, &flags);
        aux = port->rs485;
        uart_port_unlock_irqrestore(port, flags);

        if (copy_to_user(rs485, &aux, sizeof(aux)))
                return -EFAULT;

        return 0;
}

static int uart_set_rs485_config(struct tty_struct *tty, struct uart_port *port,
                         struct serial_rs485 __user *rs485_user)
{
        struct serial_rs485 rs485;
        int ret;
        unsigned long flags;

        if (!(port->rs485_supported.flags & SER_RS485_ENABLED))
                return -ENOTTY;

        if (copy_from_user(&rs485, rs485_user, sizeof(*rs485_user)))
                return -EFAULT;

        ret = uart_check_rs485_flags(port, &rs485);
        if (ret)
                return ret;
        uart_sanitize_serial_rs485(port, &rs485);
        uart_set_rs485_termination(port, &rs485);
        uart_set_rs485_rx_during_tx(port, &rs485);

        uart_port_lock_irqsave(port, &flags);
        ret = port->rs485_config(port, &tty->termios, &rs485);
        if (!ret) {
                port->rs485 = rs485;

                /* Reset RTS and other mctrl lines when disabling RS485 */
                if (!(rs485.flags & SER_RS485_ENABLED))
                        port->ops->set_mctrl(port, port->mctrl);
        }
        uart_port_unlock_irqrestore(port, flags);
        if (ret) {
                /* restore old GPIO settings */
                gpiod_set_value_cansleep(port->rs485_term_gpio,
                        !!(port->rs485.flags & SER_RS485_TERMINATE_BUS));
                gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio,
                        !!(port->rs485.flags & SER_RS485_RX_DURING_TX));
                return ret;
        }

        if (copy_to_user(rs485_user, &port->rs485, sizeof(port->rs485)))
                return -EFAULT;

        return 0;
}

static int uart_get_iso7816_config(struct uart_port *port,
                                   struct serial_iso7816 __user *iso7816)
{
        unsigned long flags;
        struct serial_iso7816 aux;

        if (!port->iso7816_config)
                return -ENOTTY;

        uart_port_lock_irqsave(port, &flags);
        aux = port->iso7816;
        uart_port_unlock_irqrestore(port, flags);

        if (copy_to_user(iso7816, &aux, sizeof(aux)))
                return -EFAULT;

        return 0;
}

static int uart_set_iso7816_config(struct uart_port *port,
                                   struct serial_iso7816 __user *iso7816_user)
{
        struct serial_iso7816 iso7816;
        int i, ret;
        unsigned long flags;

        if (!port->iso7816_config)
                return -ENOTTY;

        if (copy_from_user(&iso7816, iso7816_user, sizeof(*iso7816_user)))
                return -EFAULT;

        /*
         * There are 5 words reserved for future use. Check that userspace
         * doesn't put stuff in there to prevent breakages in the future.
         */
        for (i = 0; i < ARRAY_SIZE(iso7816.reserved); i++)
                if (iso7816.reserved[i])
                        return -EINVAL;

        uart_port_lock_irqsave(port, &flags);
        ret = port->iso7816_config(port, &iso7816);
        uart_port_unlock_irqrestore(port, flags);
        if (ret)
                return ret;

        if (copy_to_user(iso7816_user, &port->iso7816, sizeof(port->iso7816)))
                return -EFAULT;

        return 0;
}

/*
 * Called via sys_ioctl.  We can use spin_lock_irq() here.
 */
static int
uart_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)
{
        struct uart_state *state = tty->driver_data;
        struct tty_port *port = &state->port;
        struct uart_port *uport;
        void __user *uarg = (void __user *)arg;
        int ret = -ENOIOCTLCMD;


        /*
         * These ioctls don't rely on the hardware to be present.
         */
        switch (cmd) {
        case TIOCSERCONFIG:
                down_write(&tty->termios_rwsem);
                ret = uart_do_autoconfig(tty, state);
                up_write(&tty->termios_rwsem);
                break;
        }

        if (ret != -ENOIOCTLCMD)
                goto out;

        if (tty_io_error(tty)) {
                ret = -EIO;
                goto out;
        }

        /*
         * The following should only be used when hardware is present.
         */
        switch (cmd) {
        case TIOCMIWAIT:
                ret = uart_wait_modem_status(state, arg);
                break;
        }

        if (ret != -ENOIOCTLCMD)
                goto out;

        /* rs485_config requires more locking than others */
        if (cmd == TIOCSRS485)
                down_write(&tty->termios_rwsem);

        mutex_lock(&port->mutex);
        uport = uart_port_check(state);

        if (!uport || tty_io_error(tty)) {
                ret = -EIO;
                goto out_up;
        }

        /*
         * All these rely on hardware being present and need to be
         * protected against the tty being hung up.
         */

        switch (cmd) {
        case TIOCSERGETLSR: /* Get line status register */
                ret = uart_get_lsr_info(tty, state, uarg);
                break;

        case TIOCGRS485:
                ret = uart_get_rs485_config(uport, uarg);
                break;

        case TIOCSRS485:
                ret = uart_set_rs485_config(tty, uport, uarg);
                break;

        case TIOCSISO7816:
                ret = uart_set_iso7816_config(state->uart_port, uarg);
                break;

        case TIOCGISO7816:
                ret = uart_get_iso7816_config(state->uart_port, uarg);
                break;
        default:
                if (uport->ops->ioctl)
                        ret = uport->ops->ioctl(uport, cmd, arg);
                break;
        }
out_up:
        mutex_unlock(&port->mutex);
        if (cmd == TIOCSRS485)
                up_write(&tty->termios_rwsem);
out:
        return ret;
}

static void uart_set_ldisc(struct tty_struct *tty)
{
        struct uart_state *state = tty->driver_data;
        struct uart_port *uport;
        struct tty_port *port = &state->port;

        if (!tty_port_initialized(port))
                return;

        mutex_lock(&state->port.mutex);
        uport = uart_port_check(state);
        if (uport && uport->ops->set_ldisc)
                uport->ops->set_ldisc(uport, &tty->termios);
        mutex_unlock(&state->port.mutex);
}

static void uart_set_termios(struct tty_struct *tty,
                             const struct ktermios *old_termios)
{
        struct uart_state *state = tty->driver_data;
        struct uart_port *uport;
        unsigned int cflag = tty->termios.c_cflag;
        unsigned int iflag_mask = IGNBRK|BRKINT|IGNPAR|PARMRK|INPCK;
        bool sw_changed = false;

        mutex_lock(&state->port.mutex);
        uport = uart_port_check(state);
        if (!uport)
                goto out;

        /*
         * Drivers doing software flow control also need to know
         * about changes to these input settings.
         */
        if (uport->flags & UPF_SOFT_FLOW) {
                iflag_mask |= IXANY|IXON|IXOFF;
                sw_changed =
                   tty->termios.c_cc[VSTART] != old_termios->c_cc[VSTART] ||
                   tty->termios.c_cc[VSTOP] != old_termios->c_cc[VSTOP];
        }

        /*
         * These are the bits that are used to setup various
         * flags in the low level driver. We can ignore the Bfoo
         * bits in c_cflag; c_[io]speed will always be set
         * appropriately by set_termios() in tty_ioctl.c
         */
        if ((cflag ^ old_termios->c_cflag) == 0 &&
            tty->termios.c_ospeed == old_termios->c_ospeed &&
            tty->termios.c_ispeed == old_termios->c_ispeed &&
            ((tty->termios.c_iflag ^ old_termios->c_iflag) & iflag_mask) == 0 &&
            !sw_changed) {
                goto out;
        }

        uart_change_line_settings(tty, state, old_termios);
        /* reload cflag from termios; port driver may have overridden flags */
        cflag = tty->termios.c_cflag;

        /* Handle transition to B0 status */
        if (((old_termios->c_cflag & CBAUD) != B0) && ((cflag & CBAUD) == B0))
                uart_clear_mctrl(uport, TIOCM_RTS | TIOCM_DTR);
        /* Handle transition away from B0 status */
        else if (((old_termios->c_cflag & CBAUD) == B0) && ((cflag & CBAUD) != B0)) {
                unsigned int mask = TIOCM_DTR;

                if (!(cflag & CRTSCTS) || !tty_throttled(tty))
                        mask |= TIOCM_RTS;
                uart_set_mctrl(uport, mask);
        }
out:
        mutex_unlock(&state->port.mutex);
}

/*
 * Calls to uart_close() are serialised via the tty_lock in
 *   drivers/tty/tty_io.c:tty_release()
 *   drivers/tty/tty_io.c:do_tty_hangup()
 */
static void uart_close(struct tty_struct *tty, struct file *filp)
{
        struct uart_state *state = tty->driver_data;

        if (!state) {
                struct uart_driver *drv = tty->driver->driver_state;
                struct tty_port *port;

                state = drv->state + tty->index;
                port = &state->port;
                spin_lock_irq(&port->lock);
                --port->count;
                spin_unlock_irq(&port->lock);
                return;
        }

        pr_debug("uart_close(%d) called\n", tty->index);

        tty_port_close(tty->port, tty, filp);
}

static void uart_tty_port_shutdown(struct tty_port *port)
{
        struct uart_state *state = container_of(port, struct uart_state, port);
        struct uart_port *uport = uart_port_check(state);
        char *buf;

        /*
         * At this point, we stop accepting input.  To do this, we
         * disable the receive line status interrupts.
         */
        if (WARN(!uport, "detached port still initialized!\n"))
                return;

        uart_port_lock_irq(uport);
        uport->ops->stop_rx(uport);
        uart_port_unlock_irq(uport);

        uart_port_shutdown(port);

        /*
         * It's possible for shutdown to be called after suspend if we get
         * a DCD drop (hangup) at just the right time.  Clear suspended bit so
         * we don't try to resume a port that has been shutdown.
         */
        tty_port_set_suspended(port, false);

        /*
         * Free the transmit buffer.
         */
        uart_port_lock_irq(uport);
        buf = state->xmit.buf;
        state->xmit.buf = NULL;
        uart_port_unlock_irq(uport);

        free_page((unsigned long)buf);

        uart_change_pm(state, UART_PM_STATE_OFF);
}

static void uart_wait_until_sent(struct tty_struct *tty, int timeout)
{
        struct uart_state *state = tty->driver_data;
        struct uart_port *port;
        unsigned long char_time, expire, fifo_timeout;

        port = uart_port_ref(state);
        if (!port)
                return;

        if (port->type == PORT_UNKNOWN || port->fifosize == 0) {
                uart_port_deref(port);
                return;
        }

        /*
         * Set the check interval to be 1/5 of the estimated time to
         * send a single character, and make it at least 1.  The check
         * interval should also be less than the timeout.
         *
         * Note: we have to use pretty tight timings here to satisfy
         * the NIST-PCTS.
         */
        char_time = max(nsecs_to_jiffies(port->frame_time / 5), 1UL);

        if (timeout && timeout < char_time)
                char_time = timeout;

        if (!uart_cts_enabled(port)) {
                /*
                 * If the transmitter hasn't cleared in twice the approximate
                 * amount of time to send the entire FIFO, it probably won't
                 * ever clear.  This assumes the UART isn't doing flow
                 * control, which is currently the case.  Hence, if it ever
                 * takes longer than FIFO timeout, this is probably due to a
                 * UART bug of some kind.  So, we clamp the timeout parameter at
                 * 2 * FIFO timeout.
                 */
                fifo_timeout = uart_fifo_timeout(port);
                if (timeout == 0 || timeout > 2 * fifo_timeout)
                        timeout = 2 * fifo_timeout;
        }

        expire = jiffies + timeout;

        pr_debug("uart_wait_until_sent(%d), jiffies=%lu, expire=%lu...\n",
                port->line, jiffies, expire);

        /*
         * Check whether the transmitter is empty every 'char_time'.
         * 'timeout' / 'expire' give us the maximum amount of time
         * we wait.
         */
        while (!port->ops->tx_empty(port)) {
                msleep_interruptible(jiffies_to_msecs(char_time));
                if (signal_pending(current))
                        break;
                if (timeout && time_after(jiffies, expire))
                        break;
        }
        uart_port_deref(port);
}

/*
 * Calls to uart_hangup() are serialised by the tty_lock in
 *   drivers/tty/tty_io.c:do_tty_hangup()
 * This runs from a workqueue and can sleep for a _short_ time only.
 */
static void uart_hangup(struct tty_struct *tty)
{
        struct uart_state *state = tty->driver_data;
        struct tty_port *port = &state->port;
        struct uart_port *uport;
        unsigned long flags;

        pr_debug("uart_hangup(%d)\n", tty->index);

        mutex_lock(&port->mutex);
        uport = uart_port_check(state);
        WARN(!uport, "hangup of detached port!\n");

        if (tty_port_active(port)) {
                uart_flush_buffer(tty);
                uart_shutdown(tty, state);
                spin_lock_irqsave(&port->lock, flags);
                port->count = 0;
                spin_unlock_irqrestore(&port->lock, flags);
                tty_port_set_active(port, false);
                tty_port_tty_set(port, NULL);
                if (uport && !uart_console(uport))
                        uart_change_pm(state, UART_PM_STATE_OFF);
                wake_up_interruptible(&port->open_wait);
                wake_up_interruptible(&port->delta_msr_wait);
        }
        mutex_unlock(&port->mutex);
}

/* uport == NULL if uart_port has already been removed */
static void uart_port_shutdown(struct tty_port *port)
{
        struct uart_state *state = container_of(port, struct uart_state, port);
        struct uart_port *uport = uart_port_check(state);

        /*
         * clear delta_msr_wait queue to avoid mem leaks: we may free
         * the irq here so the queue might never be woken up.  Note
         * that we won't end up waiting on delta_msr_wait again since
         * any outstanding file descriptors should be pointing at
         * hung_up_tty_fops now.
         */
        wake_up_interruptible(&port->delta_msr_wait);

        if (uport) {
                /* Free the IRQ and disable the port. */
                uport->ops->shutdown(uport);

                /* Ensure that the IRQ handler isn't running on another CPU. */
                synchronize_irq(uport->irq);
        }
}

static bool uart_carrier_raised(struct tty_port *port)
{
        struct uart_state *state = container_of(port, struct uart_state, port);
        struct uart_port *uport;
        int mctrl;

        uport = uart_port_ref(state);
        /*
         * Should never observe uport == NULL since checks for hangup should
         * abort the tty_port_block_til_ready() loop before checking for carrier
         * raised -- but report carrier raised if it does anyway so open will
         * continue and not sleep
         */
        if (WARN_ON(!uport))
                return true;
        uart_port_lock_irq(uport);
        uart_enable_ms(uport);
        mctrl = uport->ops->get_mctrl(uport);
        uart_port_unlock_irq(uport);
        uart_port_deref(uport);

        return mctrl & TIOCM_CAR;
}

static void uart_dtr_rts(struct tty_port *port, bool active)
{
        struct uart_state *state = container_of(port, struct uart_state, port);
        struct uart_port *uport;

        uport = uart_port_ref(state);
        if (!uport)
                return;
        uart_port_dtr_rts(uport, active);
        uart_port_deref(uport);
}

static int uart_install(struct tty_driver *driver, struct tty_struct *tty)
{
        struct uart_driver *drv = driver->driver_state;
        struct uart_state *state = drv->state + tty->index;

        tty->driver_data = state;

        return tty_standard_install(driver, tty);
}

/*
 * Calls to uart_open are serialised by the tty_lock in
 *   drivers/tty/tty_io.c:tty_open()
 * Note that if this fails, then uart_close() _will_ be called.
 *
 * In time, we want to scrap the "opening nonpresent ports"
 * behaviour and implement an alternative way for setserial
 * to set base addresses/ports/types.  This will allow us to
 * get rid of a certain amount of extra tests.
 */
static int uart_open(struct tty_struct *tty, struct file *filp)
{
        struct uart_state *state = tty->driver_data;
        int retval;

        retval = tty_port_open(&state->port, tty, filp);
        if (retval > 0)
                retval = 0;

        return retval;
}

static int uart_port_activate(struct tty_port *port, struct tty_struct *tty)
{
        struct uart_state *state = container_of(port, struct uart_state, port);
        struct uart_port *uport;
        int ret;

        uport = uart_port_check(state);
        if (!uport || uport->flags & UPF_DEAD)
                return -ENXIO;

        /*
         * Start up the serial port.
         */
        ret = uart_startup(tty, state, false);
        if (ret > 0)
                tty_port_set_active(port, true);

        return ret;
}

static const char *uart_type(struct uart_port *port)
{
        const char *str = NULL;

        if (port->ops->type)
                str = port->ops->type(port);

        if (!str)
                str = "unknown";

        return str;
}

#ifdef CONFIG_PROC_FS

static void uart_line_info(struct seq_file *m, struct uart_driver *drv, int i)
{
        struct uart_state *state = drv->state + i;
        struct tty_port *port = &state->port;
        enum uart_pm_state pm_state;
        struct uart_port *uport;
        char stat_buf[32];
        unsigned int status;
        int mmio;

        mutex_lock(&port->mutex);
        uport = uart_port_check(state);
        if (!uport)
                goto out;

        mmio = uport->iotype >= UPIO_MEM;
        seq_printf(m, "%d: uart:%s %s%08llX irq:%d",
                        uport->line, uart_type(uport),
                        mmio ? "mmio:0x" : "port:",
                        mmio ? (unsigned long long)uport->mapbase
                             : (unsigned long long)uport->iobase,
                        uport->irq);

        if (uport->type == PORT_UNKNOWN) {
                seq_putc(m, '\n');
                goto out;
        }

        if (capable(CAP_SYS_ADMIN)) {
                pm_state = state->pm_state;
                if (pm_state != UART_PM_STATE_ON)
                        uart_change_pm(state, UART_PM_STATE_ON);
                uart_port_lock_irq(uport);
                status = uport->ops->get_mctrl(uport);
                uart_port_unlock_irq(uport);
                if (pm_state != UART_PM_STATE_ON)
                        uart_change_pm(state, pm_state);

                seq_printf(m, " tx:%d rx:%d",
                                uport->icount.tx, uport->icount.rx);
                if (uport->icount.frame)
                        seq_printf(m, " fe:%d", uport->icount.frame);
                if (uport->icount.parity)
                        seq_printf(m, " pe:%d", uport->icount.parity);
                if (uport->icount.brk)
                        seq_printf(m, " brk:%d", uport->icount.brk);
                if (uport->icount.overrun)
                        seq_printf(m, " oe:%d", uport->icount.overrun);
                if (uport->icount.buf_overrun)
                        seq_printf(m, " bo:%d", uport->icount.buf_overrun);

#define INFOBIT(bit, str) \
        if (uport->mctrl & (bit)) \
                strncat(stat_buf, (str), sizeof(stat_buf) - \
                        strlen(stat_buf) - 2)
#define STATBIT(bit, str) \
        if (status & (bit)) \
                strncat(stat_buf, (str), sizeof(stat_buf) - \
                       strlen(stat_buf) - 2)

                stat_buf[0] = '\0';
                stat_buf[1] = '\0';
                INFOBIT(TIOCM_RTS, "|RTS");
                STATBIT(TIOCM_CTS, "|CTS");
                INFOBIT(TIOCM_DTR, "|DTR");
                STATBIT(TIOCM_DSR, "|DSR");
                STATBIT(TIOCM_CAR, "|CD");
                STATBIT(TIOCM_RNG, "|RI");
                if (stat_buf[0])
                        stat_buf[0] = ' ';

                seq_puts(m, stat_buf);
        }
        seq_putc(m, '\n');
#undef STATBIT
#undef INFOBIT
out:
        mutex_unlock(&port->mutex);
}

static int uart_proc_show(struct seq_file *m, void *v)
{
        struct tty_driver *ttydrv = m->private;
        struct uart_driver *drv = ttydrv->driver_state;
        int i;

        seq_printf(m, "serinfo:1.0 driver%s%s revision:%s\n", "", "", "");
        for (i = 0; i < drv->nr; i++)
                uart_line_info(m, drv, i);
        return 0;
}
#endif

static void uart_port_spin_lock_init(struct uart_port *port)
{
        spin_lock_init(&port->lock);
        lockdep_set_class(&port->lock, &port_lock_key);
}

#if defined(CONFIG_SERIAL_CORE_CONSOLE) || defined(CONFIG_CONSOLE_POLL)
/**
 * uart_console_write - write a console message to a serial port
 * @port: the port to write the message
 * @s: array of characters
 * @count: number of characters in string to write
 * @putchar: function to write character to port
 */
void uart_console_write(struct uart_port *port, const char *s,
                        unsigned int count,
                        void (*putchar)(struct uart_port *, unsigned char))
{
        unsigned int i;

        for (i = 0; i < count; i++, s++) {
                if (*s == '\n')
                        putchar(port, '\r');
                putchar(port, *s);
        }
}
EXPORT_SYMBOL_GPL(uart_console_write);

/**
 * uart_get_console - get uart port for console
 * @ports: ports to search in
 * @nr: number of @ports
 * @co: console to search for
 * Returns: uart_port for the console @co
 *
 * Check whether an invalid uart number has been specified (as @co->index), and
 * if so, search for the first available port that does have console support.
 */
struct uart_port * __init
uart_get_console(struct uart_port *ports, int nr, struct console *co)
{
        int idx = co->index;

        if (idx < 0 || idx >= nr || (ports[idx].iobase == 0 &&
                                     ports[idx].membase == NULL))
                for (idx = 0; idx < nr; idx++)
                        if (ports[idx].iobase != 0 ||
                            ports[idx].membase != NULL)
                                break;

        co->index = idx;

        return ports + idx;
}

/**
 * uart_parse_earlycon - Parse earlycon options
 * @p:       ptr to 2nd field (ie., just beyond '<name>,')
 * @iotype:  ptr for decoded iotype (out)
 * @addr:    ptr for decoded mapbase/iobase (out)
 * @options: ptr for <options> field; %NULL if not present (out)
 *
 * Decodes earlycon kernel command line parameters of the form:
 *  * earlycon=<name>,io|mmio|mmio16|mmio32|mmio32be|mmio32native,<addr>,<options>
 *  * console=<name>,io|mmio|mmio16|mmio32|mmio32be|mmio32native,<addr>,<options>
 *
 * The optional form:
 *  * earlycon=<name>,0x<addr>,<options>
 *  * console=<name>,0x<addr>,<options>
 *
 * is also accepted; the returned @iotype will be %UPIO_MEM.
 *
 * Returns: 0 on success or -%EINVAL on failure
 */
int uart_parse_earlycon(char *p, unsigned char *iotype, resource_size_t *addr,
                        char **options)
{
        if (strncmp(p, "mmio,", 5) == 0) {
                *iotype = UPIO_MEM;
                p += 5;
        } else if (strncmp(p, "mmio16,", 7) == 0) {
                *iotype = UPIO_MEM16;
                p += 7;
        } else if (strncmp(p, "mmio32,", 7) == 0) {
                *iotype = UPIO_MEM32;
                p += 7;
        } else if (strncmp(p, "mmio32be,", 9) == 0) {
                *iotype = UPIO_MEM32BE;
                p += 9;
        } else if (strncmp(p, "mmio32native,", 13) == 0) {
                *iotype = IS_ENABLED(CONFIG_CPU_BIG_ENDIAN) ?
                        UPIO_MEM32BE : UPIO_MEM32;
                p += 13;
        } else if (strncmp(p, "io,", 3) == 0) {
                *iotype = UPIO_PORT;
                p += 3;
        } else if (strncmp(p, "0x", 2) == 0) {
                *iotype = UPIO_MEM;
        } else {
                return -EINVAL;
        }

        /*
         * Before you replace it with kstrtoull(), think about options separator
         * (',') it will not tolerate
         */
        *addr = simple_strtoull(p, NULL, 0);
        p = strchr(p, ',');
        if (p)
                p++;

        *options = p;
        return 0;
}
EXPORT_SYMBOL_GPL(uart_parse_earlycon);

/**
 * uart_parse_options - Parse serial port baud/parity/bits/flow control.
 * @options: pointer to option string
 * @baud: pointer to an 'int' variable for the baud rate.
 * @parity: pointer to an 'int' variable for the parity.
 * @bits: pointer to an 'int' variable for the number of data bits.
 * @flow: pointer to an 'int' variable for the flow control character.
 *
 * uart_parse_options() decodes a string containing the serial console
 * options. The format of the string is <baud><parity><bits><flow>,
 * eg: 115200n8r
 */
void
uart_parse_options(const char *options, int *baud, int *parity,
                   int *bits, int *flow)
{
        const char *s = options;

        *baud = simple_strtoul(s, NULL, 10);
        while (*s >= '0' && *s <= '9')
                s++;
        if (*s)
                *parity = *s++;
        if (*s)
                *bits = *s++ - '0';
        if (*s)
                *flow = *s;
}
EXPORT_SYMBOL_GPL(uart_parse_options);

/**
 * uart_set_options - setup the serial console parameters
 * @port: pointer to the serial ports uart_port structure
 * @co: console pointer
 * @baud: baud rate
 * @parity: parity character - 'n' (none), 'o' (odd), 'e' (even)
 * @bits: number of data bits
 * @flow: flow control character - 'r' (rts)
 *
 * Locking: Caller must hold console_list_lock in order to serialize
 * early initialization of the serial-console lock.
 */
int
uart_set_options(struct uart_port *port, struct console *co,
                 int baud, int parity, int bits, int flow)
{
        struct ktermios termios;
        static struct ktermios dummy;

        /*
         * Ensure that the serial-console lock is initialised early.
         *
         * Note that the console-registered check is needed because
         * kgdboc can call uart_set_options() for an already registered
         * console via tty_find_polling_driver() and uart_poll_init().
         */
        if (!uart_console_registered_locked(port) && !port->console_reinit)
                uart_port_spin_lock_init(port);

        memset(&termios, 0, sizeof(struct ktermios));

        termios.c_cflag |= CREAD | HUPCL | CLOCAL;
        tty_termios_encode_baud_rate(&termios, baud, baud);

        if (bits == 7)
                termios.c_cflag |= CS7;
        else
                termios.c_cflag |= CS8;

        switch (parity) {
        case 'o': case 'O':
                termios.c_cflag |= PARODD;
                fallthrough;
        case 'e': case 'E':
                termios.c_cflag |= PARENB;
                break;
        }

        if (flow == 'r')
                termios.c_cflag |= CRTSCTS;

        /*
         * some uarts on other side don't support no flow control.
         * So we set * DTR in host uart to make them happy
         */
        port->mctrl |= TIOCM_DTR;

        port->ops->set_termios(port, &termios, &dummy);
        /*
         * Allow the setting of the UART parameters with a NULL console
         * too:
         */
        if (co) {
                co->cflag = termios.c_cflag;
                co->ispeed = termios.c_ispeed;
                co->ospeed = termios.c_ospeed;
        }

        return 0;
}
EXPORT_SYMBOL_GPL(uart_set_options);
#endif /* CONFIG_SERIAL_CORE_CONSOLE */

/**
 * uart_change_pm - set power state of the port
 *
 * @state: port descriptor
 * @pm_state: new state
 *
 * Locking: port->mutex has to be held
 */
static void uart_change_pm(struct uart_state *state,
                           enum uart_pm_state pm_state)
{
        struct uart_port *port = uart_port_check(state);

        if (state->pm_state != pm_state) {
                if (port && port->ops->pm)
                        port->ops->pm(port, pm_state, state->pm_state);
                state->pm_state = pm_state;
        }
}

struct uart_match {
        struct uart_port *port;
        struct uart_driver *driver;
};

static int serial_match_port(struct device *dev, void *data)
{
        struct uart_match *match = data;
        struct tty_driver *tty_drv = match->driver->tty_driver;
        dev_t devt = MKDEV(tty_drv->major, tty_drv->minor_start) +
                match->port->line;

        return dev->devt == devt; /* Actually, only one tty per port */
}

int uart_suspend_port(struct uart_driver *drv, struct uart_port *uport)
{
        struct uart_state *state = drv->state + uport->line;
        struct tty_port *port = &state->port;
        struct device *tty_dev;
        struct uart_match match = {uport, drv};

        mutex_lock(&port->mutex);

        tty_dev = device_find_child(uport->dev, &match, serial_match_port);
        if (tty_dev && device_may_wakeup(tty_dev)) {
                enable_irq_wake(uport->irq);
                put_device(tty_dev);
                mutex_unlock(&port->mutex);
                return 0;
        }
        put_device(tty_dev);

        /*
         * Nothing to do if the console is not suspending
         * except stop_rx to prevent any asynchronous data
         * over RX line. However ensure that we will be
         * able to Re-start_rx later.
         */
        if (!console_suspend_enabled && uart_console(uport)) {
                if (uport->ops->start_rx) {
                        uart_port_lock_irq(uport);
                        uport->ops->stop_rx(uport);
                        uart_port_unlock_irq(uport);
                }
                goto unlock;
        }

        uport->suspended = 1;

        if (tty_port_initialized(port)) {
                const struct uart_ops *ops = uport->ops;
                int tries;
                unsigned int mctrl;

                tty_port_set_suspended(port, true);
                tty_port_set_initialized(port, false);

                uart_port_lock_irq(uport);
                ops->stop_tx(uport);
                if (!(uport->rs485.flags & SER_RS485_ENABLED))
                        ops->set_mctrl(uport, 0);
                /* save mctrl so it can be restored on resume */
                mctrl = uport->mctrl;
                uport->mctrl = 0;
                ops->stop_rx(uport);
                uart_port_unlock_irq(uport);

                /*
                 * Wait for the transmitter to empty.
                 */
                for (tries = 3; !ops->tx_empty(uport) && tries; tries--)
                        msleep(10);
                if (!tries)
                        dev_err(uport->dev, "%s: Unable to drain transmitter\n",
                                uport->name);

                ops->shutdown(uport);
                uport->mctrl = mctrl;
        }

        /*
         * Disable the console device before suspending.
         */
        if (uart_console(uport))
                console_stop(uport->cons);

        uart_change_pm(state, UART_PM_STATE_OFF);
unlock:
        mutex_unlock(&port->mutex);

        return 0;
}
EXPORT_SYMBOL(uart_suspend_port);

int uart_resume_port(struct uart_driver *drv, struct uart_port *uport)
{
        struct uart_state *state = drv->state + uport->line;
        struct tty_port *port = &state->port;
        struct device *tty_dev;
        struct uart_match match = {uport, drv};
        struct ktermios termios;

        mutex_lock(&port->mutex);

        tty_dev = device_find_child(uport->dev, &match, serial_match_port);
        if (!uport->suspended && device_may_wakeup(tty_dev)) {
                if (irqd_is_wakeup_set(irq_get_irq_data((uport->irq))))
                        disable_irq_wake(uport->irq);
                put_device(tty_dev);
                mutex_unlock(&port->mutex);
                return 0;
        }
        put_device(tty_dev);
        uport->suspended = 0;

        /*
         * Re-enable the console device after suspending.
         */
        if (uart_console(uport)) {
                /*
                 * First try to use the console cflag setting.
                 */
                memset(&termios, 0, sizeof(struct ktermios));
                termios.c_cflag = uport->cons->cflag;
                termios.c_ispeed = uport->cons->ispeed;
                termios.c_ospeed = uport->cons->ospeed;

                /*
                 * If that's unset, use the tty termios setting.
                 */
                if (port->tty && termios.c_cflag == 0)
                        termios = port->tty->termios;

                if (console_suspend_enabled)
                        uart_change_pm(state, UART_PM_STATE_ON);
                uport->ops->set_termios(uport, &termios, NULL);
                if (!console_suspend_enabled && uport->ops->start_rx) {
                        uart_port_lock_irq(uport);
                        uport->ops->start_rx(uport);
                        uart_port_unlock_irq(uport);
                }
                if (console_suspend_enabled)
                        console_start(uport->cons);
        }

        if (tty_port_suspended(port)) {
                const struct uart_ops *ops = uport->ops;
                int ret;

                uart_change_pm(state, UART_PM_STATE_ON);
                uart_port_lock_irq(uport);
                if (!(uport->rs485.flags & SER_RS485_ENABLED))
                        ops->set_mctrl(uport, 0);
                uart_port_unlock_irq(uport);
                if (console_suspend_enabled || !uart_console(uport)) {
                        /* Protected by port mutex for now */
                        struct tty_struct *tty = port->tty;

                        ret = ops->startup(uport);
                        if (ret == 0) {
                                if (tty)
                                        uart_change_line_settings(tty, state, NULL);
                                uart_rs485_config(uport);
                                uart_port_lock_irq(uport);
                                if (!(uport->rs485.flags & SER_RS485_ENABLED))
                                        ops->set_mctrl(uport, uport->mctrl);
                                ops->start_tx(uport);
                                uart_port_unlock_irq(uport);
                                tty_port_set_initialized(port, true);
                        } else {
                                /*
                                 * Failed to resume - maybe hardware went away?
                                 * Clear the "initialized" flag so we won't try
                                 * to call the low level drivers shutdown method.
                                 */
                                uart_shutdown(tty, state);
                        }
                }

                tty_port_set_suspended(port, false);
        }

        mutex_unlock(&port->mutex);

        return 0;
}
EXPORT_SYMBOL(uart_resume_port);

static inline void
uart_report_port(struct uart_driver *drv, struct uart_port *port)
{
        char address[64];

        switch (port->iotype) {
        case UPIO_PORT:
                snprintf(address, sizeof(address), "I/O 0x%lx", port->iobase);
                break;
        case UPIO_HUB6:
                snprintf(address, sizeof(address),
                         "I/O 0x%lx offset 0x%x", port->iobase, port->hub6);
                break;
        case UPIO_MEM:
        case UPIO_MEM16:
        case UPIO_MEM32:
        case UPIO_MEM32BE:
        case UPIO_AU:
        case UPIO_TSI:
                snprintf(address, sizeof(address),
                         "MMIO 0x%llx", (unsigned long long)port->mapbase);
                break;
        default:
                strscpy(address, "*unknown*", sizeof(address));
                break;
        }

        pr_info("%s%s%s at %s (irq = %d, base_baud = %d) is a %s\n",
               port->dev ? dev_name(port->dev) : "",
               port->dev ? ": " : "",
               port->name,
               address, port->irq, port->uartclk / 16, uart_type(port));

        /* The magic multiplier feature is a bit obscure, so report it too.  */
        if (port->flags & UPF_MAGIC_MULTIPLIER)
                pr_info("%s%s%s extra baud rates supported: %d, %d",
                        port->dev ? dev_name(port->dev) : "",
                        port->dev ? ": " : "",
                        port->name,
                        port->uartclk / 8, port->uartclk / 4);
}

static void
uart_configure_port(struct uart_driver *drv, struct uart_state *state,
                    struct uart_port *port)
{
        unsigned int flags;

        /*
         * If there isn't a port here, don't do anything further.
         */
        if (!port->iobase && !port->mapbase && !port->membase)
                return;

        /*
         * Now do the auto configuration stuff.  Note that config_port
         * is expected to claim the resources and map the port for us.
         */
        flags = 0;
        if (port->flags & UPF_AUTO_IRQ)
                flags |= UART_CONFIG_IRQ;
        if (port->flags & UPF_BOOT_AUTOCONF) {
                if (!(port->flags & UPF_FIXED_TYPE)) {
                        port->type = PORT_UNKNOWN;
                        flags |= UART_CONFIG_TYPE;
                }
                port->ops->config_port(port, flags);
        }

        if (port->type != PORT_UNKNOWN) {
                unsigned long flags;

                uart_report_port(drv, port);

                /* Power up port for set_mctrl() */
                uart_change_pm(state, UART_PM_STATE_ON);

                /*
                 * Ensure that the modem control lines are de-activated.
                 * keep the DTR setting that is set in uart_set_options()
                 * We probably don't need a spinlock around this, but
                 */
                uart_port_lock_irqsave(port, &flags);
                port->mctrl &= TIOCM_DTR;
                if (!(port->rs485.flags & SER_RS485_ENABLED))
                        port->ops->set_mctrl(port, port->mctrl);
                uart_port_unlock_irqrestore(port, flags);

                uart_rs485_config(port);

                /*
                 * If this driver supports console, and it hasn't been
                 * successfully registered yet, try to re-register it.
                 * It may be that the port was not available.
                 */
                if (port->cons && !console_is_registered(port->cons))
                        register_console(port->cons);

                /*
                 * Power down all ports by default, except the
                 * console if we have one.
                 */
                if (!uart_console(port))
                        uart_change_pm(state, UART_PM_STATE_OFF);
        }
}

#ifdef CONFIG_CONSOLE_POLL

static int uart_poll_init(struct tty_driver *driver, int line, char *options)
{
        struct uart_driver *drv = driver->driver_state;
        struct uart_state *state = drv->state + line;
        enum uart_pm_state pm_state;
        struct tty_port *tport;
        struct uart_port *port;
        int baud = 9600;
        int bits = 8;
        int parity = 'n';
        int flow = 'n';
        int ret = 0;

        tport = &state->port;
        mutex_lock(&tport->mutex);

        port = uart_port_check(state);
        if (!port || !(port->ops->poll_get_char && port->ops->poll_put_char)) {
                ret = -1;
                goto out;
        }

        pm_state = state->pm_state;
        uart_change_pm(state, UART_PM_STATE_ON);

        if (port->ops->poll_init) {
                /*
                 * We don't set initialized as we only initialized the hw,
                 * e.g. state->xmit is still uninitialized.
                 */
                if (!tty_port_initialized(tport))
                        ret = port->ops->poll_init(port);
        }

        if (!ret && options) {
                uart_parse_options(options, &baud, &parity, &bits, &flow);
                console_list_lock();
                ret = uart_set_options(port, NULL, baud, parity, bits, flow);
                console_list_unlock();
        }
out:
        if (ret)
                uart_change_pm(state, pm_state);
        mutex_unlock(&tport->mutex);
        return ret;
}

static int uart_poll_get_char(struct tty_driver *driver, int line)
{
        struct uart_driver *drv = driver->driver_state;
        struct uart_state *state = drv->state + line;
        struct uart_port *port;
        int ret = -1;

        port = uart_port_ref(state);
        if (port) {
                ret = port->ops->poll_get_char(port);
                uart_port_deref(port);
        }

        return ret;
}

static void uart_poll_put_char(struct tty_driver *driver, int line, char ch)
{
        struct uart_driver *drv = driver->driver_state;
        struct uart_state *state = drv->state + line;
        struct uart_port *port;

        port = uart_port_ref(state);
        if (!port)
                return;

        if (ch == '\n')
                port->ops->poll_put_char(port, '\r');
        port->ops->poll_put_char(port, ch);
        uart_port_deref(port);
}
#endif

static const struct tty_operations uart_ops = {
        .install        = uart_install,
        .open           = uart_open,
        .close          = uart_close,
        .write          = uart_write,
        .put_char       = uart_put_char,
        .flush_chars    = uart_flush_chars,
        .write_room     = uart_write_room,
        .chars_in_buffer= uart_chars_in_buffer,
        .flush_buffer   = uart_flush_buffer,
        .ioctl          = uart_ioctl,
        .throttle       = uart_throttle,
        .unthrottle     = uart_unthrottle,
        .send_xchar     = uart_send_xchar,
        .set_termios    = uart_set_termios,
        .set_ldisc      = uart_set_ldisc,
        .stop           = uart_stop,
        .start          = uart_start,
        .hangup         = uart_hangup,
        .break_ctl      = uart_break_ctl,
        .wait_until_sent= uart_wait_until_sent,
#ifdef CONFIG_PROC_FS
        .proc_show      = uart_proc_show,
#endif
        .tiocmget       = uart_tiocmget,
        .tiocmset       = uart_tiocmset,
        .set_serial     = uart_set_info_user,
        .get_serial     = uart_get_info_user,
        .get_icount     = uart_get_icount,
#ifdef CONFIG_CONSOLE_POLL
        .poll_init      = uart_poll_init,
        .poll_get_char  = uart_poll_get_char,
        .poll_put_char  = uart_poll_put_char,
#endif
};

static const struct tty_port_operations uart_port_ops = {
        .carrier_raised = uart_carrier_raised,
        .dtr_rts        = uart_dtr_rts,
        .activate       = uart_port_activate,
        .shutdown       = uart_tty_port_shutdown,
};

/**
 * uart_register_driver - register a driver with the uart core layer
 * @drv: low level driver structure
 *
 * Register a uart driver with the core driver. We in turn register with the
 * tty layer, and initialise the core driver per-port state.
 *
 * We have a proc file in /proc/tty/driver which is named after the normal
 * driver.
 *
 * @drv->port should be %NULL, and the per-port structures should be registered
 * using uart_add_one_port() after this call has succeeded.
 *
 * Locking: none, Interrupts: enabled
 */
int uart_register_driver(struct uart_driver *drv)
{
        struct tty_driver *normal;
        int i, retval = -ENOMEM;

        BUG_ON(drv->state);

        /*
         * Maybe we should be using a slab cache for this, especially if
         * we have a large number of ports to handle.
         */
        drv->state = kcalloc(drv->nr, sizeof(struct uart_state), GFP_KERNEL);
        if (!drv->state)
                goto out;

        normal = tty_alloc_driver(drv->nr, TTY_DRIVER_REAL_RAW |
                        TTY_DRIVER_DYNAMIC_DEV);
        if (IS_ERR(normal)) {
                retval = PTR_ERR(normal);
                goto out_kfree;
        }

        drv->tty_driver = normal;

        normal->driver_name     = drv->driver_name;
        normal->name            = drv->dev_name;
        normal->major           = drv->major;
        normal->minor_start     = drv->minor;
        normal->type            = TTY_DRIVER_TYPE_SERIAL;
        normal->subtype         = SERIAL_TYPE_NORMAL;
        normal->init_termios    = tty_std_termios;
        normal->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL | CLOCAL;
        normal->init_termios.c_ispeed = normal->init_termios.c_ospeed = 9600;
        normal->driver_state    = drv;
        tty_set_operations(normal, &uart_ops);

        /*
         * Initialise the UART state(s).
         */
        for (i = 0; i < drv->nr; i++) {
                struct uart_state *state = drv->state + i;
                struct tty_port *port = &state->port;

                tty_port_init(port);
                port->ops = &uart_port_ops;
        }

        retval = tty_register_driver(normal);
        if (retval >= 0)
                return retval;

        for (i = 0; i < drv->nr; i++)
                tty_port_destroy(&drv->state[i].port);
        tty_driver_kref_put(normal);
out_kfree:
        kfree(drv->state);
out:
        return retval;
}
EXPORT_SYMBOL(uart_register_driver);

/**
 * uart_unregister_driver - remove a driver from the uart core layer
 * @drv: low level driver structure
 *
 * Remove all references to a driver from the core driver. The low level
 * driver must have removed all its ports via the uart_remove_one_port() if it
 * registered them with uart_add_one_port(). (I.e. @drv->port is %NULL.)
 *
 * Locking: none, Interrupts: enabled
 */
void uart_unregister_driver(struct uart_driver *drv)
{
        struct tty_driver *p = drv->tty_driver;
        unsigned int i;

        tty_unregister_driver(p);
        tty_driver_kref_put(p);
        for (i = 0; i < drv->nr; i++)
                tty_port_destroy(&drv->state[i].port);
        kfree(drv->state);
        drv->state = NULL;
        drv->tty_driver = NULL;
}
EXPORT_SYMBOL(uart_unregister_driver);

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

static ssize_t uartclk_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
        struct serial_struct tmp;
        struct tty_port *port = dev_get_drvdata(dev);

        uart_get_info(port, &tmp);
        return sprintf(buf, "%d\n", tmp.baud_base * 16);
}

static ssize_t type_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
        struct serial_struct tmp;
        struct tty_port *port = dev_get_drvdata(dev);

        uart_get_info(port, &tmp);
        return sprintf(buf, "%d\n", tmp.type);
}

static ssize_t line_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
        struct serial_struct tmp;
        struct tty_port *port = dev_get_drvdata(dev);

        uart_get_info(port, &tmp);
        return sprintf(buf, "%d\n", tmp.line);
}

static ssize_t port_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
        struct serial_struct tmp;
        struct tty_port *port = dev_get_drvdata(dev);
        unsigned long ioaddr;

        uart_get_info(port, &tmp);
        ioaddr = tmp.port;
        if (HIGH_BITS_OFFSET)
                ioaddr |= (unsigned long)tmp.port_high << HIGH_BITS_OFFSET;
        return sprintf(buf, "0x%lX\n", ioaddr);
}

static ssize_t irq_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
        struct serial_struct tmp;
        struct tty_port *port = dev_get_drvdata(dev);

        uart_get_info(port, &tmp);
        return sprintf(buf, "%d\n", tmp.irq);
}

static ssize_t flags_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
        struct serial_struct tmp;
        struct tty_port *port = dev_get_drvdata(dev);

        uart_get_info(port, &tmp);
        return sprintf(buf, "0x%X\n", tmp.flags);
}

static ssize_t xmit_fifo_size_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
        struct serial_struct tmp;
        struct tty_port *port = dev_get_drvdata(dev);

        uart_get_info(port, &tmp);
        return sprintf(buf, "%d\n", tmp.xmit_fifo_size);
}

static ssize_t close_delay_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
        struct serial_struct tmp;
        struct tty_port *port = dev_get_drvdata(dev);

        uart_get_info(port, &tmp);
        return sprintf(buf, "%d\n", tmp.close_delay);
}

static ssize_t closing_wait_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
        struct serial_struct tmp;
        struct tty_port *port = dev_get_drvdata(dev);

        uart_get_info(port, &tmp);
        return sprintf(buf, "%d\n", tmp.closing_wait);
}

static ssize_t custom_divisor_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
        struct serial_struct tmp;
        struct tty_port *port = dev_get_drvdata(dev);

        uart_get_info(port, &tmp);
        return sprintf(buf, "%d\n", tmp.custom_divisor);
}

static ssize_t io_type_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
        struct serial_struct tmp;
        struct tty_port *port = dev_get_drvdata(dev);

        uart_get_info(port, &tmp);
        return sprintf(buf, "%d\n", tmp.io_type);
}

static ssize_t iomem_base_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
        struct serial_struct tmp;
        struct tty_port *port = dev_get_drvdata(dev);

        uart_get_info(port, &tmp);
        return sprintf(buf, "0x%lX\n", (unsigned long)tmp.iomem_base);
}

static ssize_t iomem_reg_shift_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
        struct serial_struct tmp;
        struct tty_port *port = dev_get_drvdata(dev);

        uart_get_info(port, &tmp);
        return sprintf(buf, "%d\n", tmp.iomem_reg_shift);
}

static ssize_t console_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
        struct tty_port *port = dev_get_drvdata(dev);
        struct uart_state *state = container_of(port, struct uart_state, port);
        struct uart_port *uport;
        bool console = false;

        mutex_lock(&port->mutex);
        uport = uart_port_check(state);
        if (uport)
                console = uart_console_registered(uport);
        mutex_unlock(&port->mutex);

        return sprintf(buf, "%c\n", console ? 'Y' : 'N');
}

static ssize_t console_store(struct device *dev,
        struct device_attribute *attr, const char *buf, size_t count)
{
        struct tty_port *port = dev_get_drvdata(dev);
        struct uart_state *state = container_of(port, struct uart_state, port);
        struct uart_port *uport;
        bool oldconsole, newconsole;
        int ret;

        ret = kstrtobool(buf, &newconsole);
        if (ret)
                return ret;

        mutex_lock(&port->mutex);
        uport = uart_port_check(state);
        if (uport) {
                oldconsole = uart_console_registered(uport);
                if (oldconsole && !newconsole) {
                        ret = unregister_console(uport->cons);
                } else if (!oldconsole && newconsole) {
                        if (uart_console(uport)) {
                                uport->console_reinit = 1;
                                register_console(uport->cons);
                        } else {
                                ret = -ENOENT;
                        }
                }
        } else {
                ret = -ENXIO;
        }
        mutex_unlock(&port->mutex);

        return ret < 0 ? ret : count;
}

static DEVICE_ATTR_RO(uartclk);
static DEVICE_ATTR_RO(type);
static DEVICE_ATTR_RO(line);
static DEVICE_ATTR_RO(port);
static DEVICE_ATTR_RO(irq);
static DEVICE_ATTR_RO(flags);
static DEVICE_ATTR_RO(xmit_fifo_size);
static DEVICE_ATTR_RO(close_delay);
static DEVICE_ATTR_RO(closing_wait);
static DEVICE_ATTR_RO(custom_divisor);
static DEVICE_ATTR_RO(io_type);
static DEVICE_ATTR_RO(iomem_base);
static DEVICE_ATTR_RO(iomem_reg_shift);
static DEVICE_ATTR_RW(console);

static struct attribute *tty_dev_attrs[] = {
        &dev_attr_uartclk.attr,
        &dev_attr_type.attr,
        &dev_attr_line.attr,
        &dev_attr_port.attr,
        &dev_attr_irq.attr,
        &dev_attr_flags.attr,
        &dev_attr_xmit_fifo_size.attr,
        &dev_attr_close_delay.attr,
        &dev_attr_closing_wait.attr,
        &dev_attr_custom_divisor.attr,
        &dev_attr_io_type.attr,
        &dev_attr_iomem_base.attr,
        &dev_attr_iomem_reg_shift.attr,
        &dev_attr_console.attr,
        NULL
};

static const struct attribute_group tty_dev_attr_group = {
        .attrs = tty_dev_attrs,
};

/**
 * serial_core_add_one_port - attach a driver-defined port structure
 * @drv: pointer to the uart low level driver structure for this port
 * @uport: uart port structure to use for this port.
 *
 * Context: task context, might sleep
 *
 * This allows the driver @drv to register its own uart_port structure with the
 * core driver. The main purpose is to allow the low level uart drivers to
 * expand uart_port, rather than having yet more levels of structures.
 * Caller must hold port_mutex.
 */
static int serial_core_add_one_port(struct uart_driver *drv, struct uart_port *uport)
{
        struct uart_state *state;
        struct tty_port *port;
        int ret = 0;
        struct device *tty_dev;
        int num_groups;

        if (uport->line >= drv->nr)
                return -EINVAL;

        state = drv->state + uport->line;
        port = &state->port;

        mutex_lock(&port->mutex);
        if (state->uart_port) {
                ret = -EINVAL;
                goto out;
        }

        /* Link the port to the driver state table and vice versa */
        atomic_set(&state->refcount, 1);
        init_waitqueue_head(&state->remove_wait);
        state->uart_port = uport;
        uport->state = state;

        state->pm_state = UART_PM_STATE_UNDEFINED;
        uport->cons = drv->cons;
        uport->minor = drv->tty_driver->minor_start + uport->line;
        uport->name = kasprintf(GFP_KERNEL, "%s%d", drv->dev_name,
                                drv->tty_driver->name_base + uport->line);
        if (!uport->name) {
                ret = -ENOMEM;
                goto out;
        }

        /*
         * If this port is in use as a console then the spinlock is already
         * initialised.
         */
        if (!uart_console_registered(uport))
                uart_port_spin_lock_init(uport);

        if (uport->cons && uport->dev)
                of_console_check(uport->dev->of_node, uport->cons->name, uport->line);

        tty_port_link_device(port, drv->tty_driver, uport->line);
        uart_configure_port(drv, state, uport);

        port->console = uart_console(uport);

        num_groups = 2;
        if (uport->attr_group)
                num_groups++;

        uport->tty_groups = kcalloc(num_groups, sizeof(*uport->tty_groups),
                                    GFP_KERNEL);
        if (!uport->tty_groups) {
                ret = -ENOMEM;
                goto out;
        }
        uport->tty_groups[0] = &tty_dev_attr_group;
        if (uport->attr_group)
                uport->tty_groups[1] = uport->attr_group;

        /*
         * Register the port whether it's detected or not.  This allows
         * setserial to be used to alter this port's parameters.
         */
        tty_dev = tty_port_register_device_attr_serdev(port, drv->tty_driver,
                        uport->line, uport->dev, port, uport->tty_groups);
        if (!IS_ERR(tty_dev)) {
                device_set_wakeup_capable(tty_dev, 1);
        } else {
                dev_err(uport->dev, "Cannot register tty device on line %d\n",
                       uport->line);
        }

 out:
        mutex_unlock(&port->mutex);

        return ret;
}

/**
 * serial_core_remove_one_port - detach a driver defined port structure
 * @drv: pointer to the uart low level driver structure for this port
 * @uport: uart port structure for this port
 *
 * Context: task context, might sleep
 *
 * This unhooks (and hangs up) the specified port structure from the core
 * driver. No further calls will be made to the low-level code for this port.
 * Caller must hold port_mutex.
 */
static void serial_core_remove_one_port(struct uart_driver *drv,
                                        struct uart_port *uport)
{
        struct uart_state *state = drv->state + uport->line;
        struct tty_port *port = &state->port;
        struct uart_port *uart_port;
        struct tty_struct *tty;

        mutex_lock(&port->mutex);
        uart_port = uart_port_check(state);
        if (uart_port != uport)
                dev_alert(uport->dev, "Removing wrong port: %p != %p\n",
                          uart_port, uport);

        if (!uart_port) {
                mutex_unlock(&port->mutex);
                return;
        }
        mutex_unlock(&port->mutex);

        /*
         * Remove the devices from the tty layer
         */
        tty_port_unregister_device(port, drv->tty_driver, uport->line);

        tty = tty_port_tty_get(port);
        if (tty) {
                tty_vhangup(port->tty);
                tty_kref_put(tty);
        }

        /*
         * If the port is used as a console, unregister it
         */
        if (uart_console(uport))
                unregister_console(uport->cons);

        /*
         * Free the port IO and memory resources, if any.
         */
        if (uport->type != PORT_UNKNOWN && uport->ops->release_port)
                uport->ops->release_port(uport);
        kfree(uport->tty_groups);
        kfree(uport->name);

        /*
         * Indicate that there isn't a port here anymore.
         */
        uport->type = PORT_UNKNOWN;
        uport->port_dev = NULL;

        mutex_lock(&port->mutex);
        WARN_ON(atomic_dec_return(&state->refcount) < 0);
        wait_event(state->remove_wait, !atomic_read(&state->refcount));
        state->uart_port = NULL;
        mutex_unlock(&port->mutex);
}

/**
 * uart_match_port - are the two ports equivalent?
 * @port1: first port
 * @port2: second port
 *
 * This utility function can be used to determine whether two uart_port
 * structures describe the same port.
 */
bool uart_match_port(const struct uart_port *port1,
                const struct uart_port *port2)
{
        if (port1->iotype != port2->iotype)
                return false;

        switch (port1->iotype) {
        case UPIO_PORT:
                return port1->iobase == port2->iobase;
        case UPIO_HUB6:
                return port1->iobase == port2->iobase &&
                       port1->hub6   == port2->hub6;
        case UPIO_MEM:
        case UPIO_MEM16:
        case UPIO_MEM32:
        case UPIO_MEM32BE:
        case UPIO_AU:
        case UPIO_TSI:
                return port1->mapbase == port2->mapbase;
        }

        return false;
}
EXPORT_SYMBOL(uart_match_port);

static struct serial_ctrl_device *
serial_core_get_ctrl_dev(struct serial_port_device *port_dev)
{
        struct device *dev = &port_dev->dev;

        return to_serial_base_ctrl_device(dev->parent);
}

/*
 * Find a registered serial core controller device if one exists. Returns
 * the first device matching the ctrl_id. Caller must hold port_mutex.
 */
static struct serial_ctrl_device *serial_core_ctrl_find(struct uart_driver *drv,
                                                        struct device *phys_dev,
                                                        int ctrl_id)
{
        struct uart_state *state;
        int i;

        lockdep_assert_held(&port_mutex);

        for (i = 0; i < drv->nr; i++) {
                state = drv->state + i;
                if (!state->uart_port || !state->uart_port->port_dev)
                        continue;

                if (state->uart_port->dev == phys_dev &&
                    state->uart_port->ctrl_id == ctrl_id)
                        return serial_core_get_ctrl_dev(state->uart_port->port_dev);
        }

        return NULL;
}

static struct serial_ctrl_device *serial_core_ctrl_device_add(struct uart_port *port)
{
        return serial_base_ctrl_add(port, port->dev);
}

static int serial_core_port_device_add(struct serial_ctrl_device *ctrl_dev,
                                       struct uart_port *port)
{
        struct serial_port_device *port_dev;

        port_dev = serial_base_port_add(port, ctrl_dev);
        if (IS_ERR(port_dev))
                return PTR_ERR(port_dev);

        port->port_dev = port_dev;

        return 0;
}

/*
 * Initialize a serial core port device, and a controller device if needed.
 */
int serial_core_register_port(struct uart_driver *drv, struct uart_port *port)
{
        struct serial_ctrl_device *ctrl_dev, *new_ctrl_dev = NULL;
        int ret;

        mutex_lock(&port_mutex);

        /*
         * Prevent serial_port_runtime_resume() from trying to use the port
         * until serial_core_add_one_port() has completed
         */
        port->flags |= UPF_DEAD;

        /* Inititalize a serial core controller device if needed */
        ctrl_dev = serial_core_ctrl_find(drv, port->dev, port->ctrl_id);
        if (!ctrl_dev) {
                new_ctrl_dev = serial_core_ctrl_device_add(port);
                if (IS_ERR(new_ctrl_dev)) {
                        ret = PTR_ERR(new_ctrl_dev);
                        goto err_unlock;
                }
                ctrl_dev = new_ctrl_dev;
        }

        /*
         * Initialize a serial core port device. Tag the port dead to prevent
         * serial_port_runtime_resume() trying to do anything until port has
         * been registered. It gets cleared by serial_core_add_one_port().
         */
        ret = serial_core_port_device_add(ctrl_dev, port);
        if (ret)
                goto err_unregister_ctrl_dev;

        ret = serial_core_add_one_port(drv, port);
        if (ret)
                goto err_unregister_port_dev;

        port->flags &= ~UPF_DEAD;

        mutex_unlock(&port_mutex);

        return 0;

err_unregister_port_dev:
        serial_base_port_device_remove(port->port_dev);

err_unregister_ctrl_dev:
        serial_base_ctrl_device_remove(new_ctrl_dev);

err_unlock:
        mutex_unlock(&port_mutex);

        return ret;
}

/*
 * Removes a serial core port device, and the related serial core controller
 * device if the last instance.
 */
void serial_core_unregister_port(struct uart_driver *drv, struct uart_port *port)
{
        struct device *phys_dev = port->dev;
        struct serial_port_device *port_dev = port->port_dev;
        struct serial_ctrl_device *ctrl_dev = serial_core_get_ctrl_dev(port_dev);
        int ctrl_id = port->ctrl_id;

        mutex_lock(&port_mutex);

        port->flags |= UPF_DEAD;

        serial_core_remove_one_port(drv, port);

        /* Note that struct uart_port *port is no longer valid at this point */
        serial_base_port_device_remove(port_dev);

        /* Drop the serial core controller device if no ports are using it */
        if (!serial_core_ctrl_find(drv, phys_dev, ctrl_id))
                serial_base_ctrl_device_remove(ctrl_dev);

        mutex_unlock(&port_mutex);
}

/**
 * uart_handle_dcd_change - handle a change of carrier detect state
 * @uport: uart_port structure for the open port
 * @active: new carrier detect status
 *
 * Caller must hold uport->lock.
 */
void uart_handle_dcd_change(struct uart_port *uport, bool active)
{
        struct tty_port *port = &uport->state->port;
        struct tty_struct *tty = port->tty;
        struct tty_ldisc *ld;

        lockdep_assert_held_once(&uport->lock);

        if (tty) {
                ld = tty_ldisc_ref(tty);
                if (ld) {
                        if (ld->ops->dcd_change)
                                ld->ops->dcd_change(tty, active);
                        tty_ldisc_deref(ld);
                }
        }

        uport->icount.dcd++;

        if (uart_dcd_enabled(uport)) {
                if (active)
                        wake_up_interruptible(&port->open_wait);
                else if (tty)
                        tty_hangup(tty);
        }
}
EXPORT_SYMBOL_GPL(uart_handle_dcd_change);

/**
 * uart_handle_cts_change - handle a change of clear-to-send state
 * @uport: uart_port structure for the open port
 * @active: new clear-to-send status
 *
 * Caller must hold uport->lock.
 */
void uart_handle_cts_change(struct uart_port *uport, bool active)
{
        lockdep_assert_held_once(&uport->lock);

        uport->icount.cts++;

        if (uart_softcts_mode(uport)) {
                if (uport->hw_stopped) {
                        if (active) {
                                uport->hw_stopped = false;
                                uport->ops->start_tx(uport);
                                uart_write_wakeup(uport);
                        }
                } else {
                        if (!active) {
                                uport->hw_stopped = true;
                                uport->ops->stop_tx(uport);
                        }
                }

        }
}
EXPORT_SYMBOL_GPL(uart_handle_cts_change);

/**
 * uart_insert_char - push a char to the uart layer
 *
 * User is responsible to call tty_flip_buffer_push when they are done with
 * insertion.
 *
 * @port: corresponding port
 * @status: state of the serial port RX buffer (LSR for 8250)
 * @overrun: mask of overrun bits in @status
 * @ch: character to push
 * @flag: flag for the character (see TTY_NORMAL and friends)
 */
void uart_insert_char(struct uart_port *port, unsigned int status,
                      unsigned int overrun, u8 ch, u8 flag)
{
        struct tty_port *tport = &port->state->port;

        if ((status & port->ignore_status_mask & ~overrun) == 0)
                if (tty_insert_flip_char(tport, ch, flag) == 0)
                        ++port->icount.buf_overrun;

        /*
         * Overrun is special.  Since it's reported immediately,
         * it doesn't affect the current character.
         */
        if (status & ~port->ignore_status_mask & overrun)
                if (tty_insert_flip_char(tport, 0, TTY_OVERRUN) == 0)
                        ++port->icount.buf_overrun;
}
EXPORT_SYMBOL_GPL(uart_insert_char);

#ifdef CONFIG_MAGIC_SYSRQ_SERIAL
static const u8 sysrq_toggle_seq[] = CONFIG_MAGIC_SYSRQ_SERIAL_SEQUENCE;

static void uart_sysrq_on(struct work_struct *w)
{
        int sysrq_toggle_seq_len = strlen(sysrq_toggle_seq);

        sysrq_toggle_support(1);
        pr_info("SysRq is enabled by magic sequence '%*pE' on serial\n",
                sysrq_toggle_seq_len, sysrq_toggle_seq);
}
static DECLARE_WORK(sysrq_enable_work, uart_sysrq_on);

/**
 * uart_try_toggle_sysrq - Enables SysRq from serial line
 * @port: uart_port structure where char(s) after BREAK met
 * @ch: new character in the sequence after received BREAK
 *
 * Enables magic SysRq when the required sequence is met on port
 * (see CONFIG_MAGIC_SYSRQ_SERIAL_SEQUENCE).
 *
 * Returns: %false if @ch is out of enabling sequence and should be
 * handled some other way, %true if @ch was consumed.
 */
bool uart_try_toggle_sysrq(struct uart_port *port, u8 ch)
{
        int sysrq_toggle_seq_len = strlen(sysrq_toggle_seq);

        if (!sysrq_toggle_seq_len)
                return false;

        BUILD_BUG_ON(ARRAY_SIZE(sysrq_toggle_seq) >= U8_MAX);
        if (sysrq_toggle_seq[port->sysrq_seq] != ch) {
                port->sysrq_seq = 0;
                return false;
        }

        if (++port->sysrq_seq < sysrq_toggle_seq_len) {
                port->sysrq = jiffies + SYSRQ_TIMEOUT;
                return true;
        }

        schedule_work(&sysrq_enable_work);

        port->sysrq = 0;
        return true;
}
EXPORT_SYMBOL_GPL(uart_try_toggle_sysrq);
#endif

/**
 * uart_get_rs485_mode() - retrieve rs485 properties for given uart
 * @port: uart device's target port
 *
 * This function implements the device tree binding described in
 * Documentation/devicetree/bindings/serial/rs485.txt.
 */
int uart_get_rs485_mode(struct uart_port *port)
{
        struct serial_rs485 *rs485conf = &port->rs485;
        struct device *dev = port->dev;
        enum gpiod_flags dflags;
        struct gpio_desc *desc;
        u32 rs485_delay[2];
        int ret;

        if (!(port->rs485_supported.flags & SER_RS485_ENABLED))
                return 0;

        ret = device_property_read_u32_array(dev, "rs485-rts-delay",
                                             rs485_delay, 2);
        if (!ret) {
                rs485conf->delay_rts_before_send = rs485_delay[0];
                rs485conf->delay_rts_after_send = rs485_delay[1];
        } else {
                rs485conf->delay_rts_before_send = 0;
                rs485conf->delay_rts_after_send = 0;
        }

        uart_sanitize_serial_rs485_delays(port, rs485conf);

        /*
         * Clear full-duplex and enabled flags, set RTS polarity to active high
         * to get to a defined state with the following properties:
         */
        rs485conf->flags &= ~(SER_RS485_RX_DURING_TX | SER_RS485_ENABLED |
                              SER_RS485_TERMINATE_BUS |
                              SER_RS485_RTS_AFTER_SEND);
        rs485conf->flags |= SER_RS485_RTS_ON_SEND;

        if (device_property_read_bool(dev, "rs485-rx-during-tx"))
                rs485conf->flags |= SER_RS485_RX_DURING_TX;

        if (device_property_read_bool(dev, "linux,rs485-enabled-at-boot-time"))
                rs485conf->flags |= SER_RS485_ENABLED;

        if (device_property_read_bool(dev, "rs485-rts-active-low")) {
                rs485conf->flags &= ~SER_RS485_RTS_ON_SEND;
                rs485conf->flags |= SER_RS485_RTS_AFTER_SEND;
        }

        /*
         * Disabling termination by default is the safe choice:  Else if many
         * bus participants enable it, no communication is possible at all.
         * Works fine for short cables and users may enable for longer cables.
         */
        desc = devm_gpiod_get_optional(dev, "rs485-term", GPIOD_OUT_LOW);
        if (IS_ERR(desc))
                return dev_err_probe(dev, PTR_ERR(desc), "Cannot get rs485-term-gpios\n");
        port->rs485_term_gpio = desc;
        if (port->rs485_term_gpio)
                port->rs485_supported.flags |= SER_RS485_TERMINATE_BUS;

        dflags = (rs485conf->flags & SER_RS485_RX_DURING_TX) ?
                 GPIOD_OUT_HIGH : GPIOD_OUT_LOW;
        desc = devm_gpiod_get_optional(dev, "rs485-rx-during-tx", dflags);
        if (IS_ERR(desc))
                return dev_err_probe(dev, PTR_ERR(desc), "Cannot get rs485-rx-during-tx-gpios\n");
        port->rs485_rx_during_tx_gpio = desc;
        if (port->rs485_rx_during_tx_gpio)
                port->rs485_supported.flags |= SER_RS485_RX_DURING_TX;

        return 0;
}
EXPORT_SYMBOL_GPL(uart_get_rs485_mode);

/* Compile-time assertions for serial_rs485 layout */
static_assert(offsetof(struct serial_rs485, padding) ==
              (offsetof(struct serial_rs485, delay_rts_after_send) + sizeof(__u32)));
static_assert(offsetof(struct serial_rs485, padding1) ==
              offsetof(struct serial_rs485, padding[1]));
static_assert((offsetof(struct serial_rs485, padding[4]) + sizeof(__u32)) ==
              sizeof(struct serial_rs485));

MODULE_DESCRIPTION("Serial driver core");
MODULE_LICENSE("GPL");