serial: 8250: fix null-ptr-deref in serial8250_start_tx()

[linux/fpc-iii.git] / drivers / tty / serial / 8250 / 8250_core.c

// SPDX-License-Identifier: GPL-2.0+
/*
 *  Universal/legacy driver for 8250/16550-type serial ports
 *
 *  Based on drivers/char/serial.c, by Linus Torvalds, Theodore Ts'o.
 *
 *  Copyright (C) 2001 Russell King.
 *
 *  Supports: ISA-compatible 8250/16550 ports
 *            PNP 8250/16550 ports
 *            early_serial_setup() ports
 *            userspace-configurable "phantom" ports
 *            "serial8250" platform devices
 *            serial8250_register_8250_port() ports
 */

#include <linux/acpi.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/ioport.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/sysrq.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/tty.h>
#include <linux/ratelimit.h>
#include <linux/tty_flip.h>
#include <linux/serial.h>
#include <linux/serial_8250.h>
#include <linux/nmi.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/pm_runtime.h>
#include <linux/io.h>
#ifdef CONFIG_SPARC
#include <linux/sunserialcore.h>
#endif

#include <asm/irq.h>

#include "8250.h"

/*
 * Configuration:
 *   share_irqs - whether we pass IRQF_SHARED to request_irq().  This option
 *                is unsafe when used on edge-triggered interrupts.
 */
static unsigned int share_irqs = SERIAL8250_SHARE_IRQS;

static unsigned int nr_uarts = CONFIG_SERIAL_8250_RUNTIME_UARTS;

static struct uart_driver serial8250_reg;

static unsigned int skip_txen_test; /* force skip of txen test at init time */

#define PASS_LIMIT      512

#include <asm/serial.h>
/*
 * SERIAL_PORT_DFNS tells us about built-in ports that have no
 * standard enumeration mechanism.   Platforms that can find all
 * serial ports via mechanisms like ACPI or PCI need not supply it.
 */
#ifndef SERIAL_PORT_DFNS
#define SERIAL_PORT_DFNS
#endif

static const struct old_serial_port old_serial_port[] = {
        SERIAL_PORT_DFNS /* defined in asm/serial.h */
};

#define UART_NR CONFIG_SERIAL_8250_NR_UARTS

#ifdef CONFIG_SERIAL_8250_RSA

#define PORT_RSA_MAX 4
static unsigned long probe_rsa[PORT_RSA_MAX];
static unsigned int probe_rsa_count;
#endif /* CONFIG_SERIAL_8250_RSA  */

struct irq_info {
        struct                  hlist_node node;
        int                     irq;
        spinlock_t              lock;   /* Protects list not the hash */
        struct list_head        *head;
};

#define NR_IRQ_HASH             32      /* Can be adjusted later */
static struct hlist_head irq_lists[NR_IRQ_HASH];
static DEFINE_MUTEX(hash_mutex);        /* Used to walk the hash */

/*
 * This is the serial driver's interrupt routine.
 *
 * Arjan thinks the old way was overly complex, so it got simplified.
 * Alan disagrees, saying that need the complexity to handle the weird
 * nature of ISA shared interrupts.  (This is a special exception.)
 *
 * In order to handle ISA shared interrupts properly, we need to check
 * that all ports have been serviced, and therefore the ISA interrupt
 * line has been de-asserted.
 *
 * This means we need to loop through all ports. checking that they
 * don't have an interrupt pending.
 */
static irqreturn_t serial8250_interrupt(int irq, void *dev_id)
{
        struct irq_info *i = dev_id;
        struct list_head *l, *end = NULL;
        int pass_counter = 0, handled = 0;

        pr_debug("%s(%d): start\n", __func__, irq);

        spin_lock(&i->lock);

        l = i->head;
        do {
                struct uart_8250_port *up;
                struct uart_port *port;

                up = list_entry(l, struct uart_8250_port, list);
                port = &up->port;

                if (port->handle_irq(port)) {
                        handled = 1;
                        end = NULL;
                } else if (end == NULL)
                        end = l;

                l = l->next;

                if (l == i->head && pass_counter++ > PASS_LIMIT)
                        break;
        } while (l != end);

        spin_unlock(&i->lock);

        pr_debug("%s(%d): end\n", __func__, irq);

        return IRQ_RETVAL(handled);
}

/*
 * To support ISA shared interrupts, we need to have one interrupt
 * handler that ensures that the IRQ line has been deasserted
 * before returning.  Failing to do this will result in the IRQ
 * line being stuck active, and, since ISA irqs are edge triggered,
 * no more IRQs will be seen.
 */
static void serial_do_unlink(struct irq_info *i, struct uart_8250_port *up)
{
        spin_lock_irq(&i->lock);

        if (!list_empty(i->head)) {
                if (i->head == &up->list)
                        i->head = i->head->next;
                list_del(&up->list);
        } else {
                BUG_ON(i->head != &up->list);
                i->head = NULL;
        }
        spin_unlock_irq(&i->lock);
        /* List empty so throw away the hash node */
        if (i->head == NULL) {
                hlist_del(&i->node);
                kfree(i);
        }
}

static int serial_link_irq_chain(struct uart_8250_port *up)
{
        struct hlist_head *h;
        struct hlist_node *n;
        struct irq_info *i;
        int ret;

        mutex_lock(&hash_mutex);

        h = &irq_lists[up->port.irq % NR_IRQ_HASH];

        hlist_for_each(n, h) {
                i = hlist_entry(n, struct irq_info, node);
                if (i->irq == up->port.irq)
                        break;
        }

        if (n == NULL) {
                i = kzalloc(sizeof(struct irq_info), GFP_KERNEL);
                if (i == NULL) {
                        mutex_unlock(&hash_mutex);
                        return -ENOMEM;
                }
                spin_lock_init(&i->lock);
                i->irq = up->port.irq;
                hlist_add_head(&i->node, h);
        }
        mutex_unlock(&hash_mutex);

        spin_lock_irq(&i->lock);

        if (i->head) {
                list_add(&up->list, i->head);
                spin_unlock_irq(&i->lock);

                ret = 0;
        } else {
                INIT_LIST_HEAD(&up->list);
                i->head = &up->list;
                spin_unlock_irq(&i->lock);
                ret = request_irq(up->port.irq, serial8250_interrupt,
                                  up->port.irqflags, up->port.name, i);
                if (ret < 0)
                        serial_do_unlink(i, up);
        }

        return ret;
}

static void serial_unlink_irq_chain(struct uart_8250_port *up)
{
        /*
         * yes, some broken gcc emit "warning: 'i' may be used uninitialized"
         * but no, we are not going to take a patch that assigns NULL below.
         */
        struct irq_info *i;
        struct hlist_node *n;
        struct hlist_head *h;

        mutex_lock(&hash_mutex);

        h = &irq_lists[up->port.irq % NR_IRQ_HASH];

        hlist_for_each(n, h) {
                i = hlist_entry(n, struct irq_info, node);
                if (i->irq == up->port.irq)
                        break;
        }

        BUG_ON(n == NULL);
        BUG_ON(i->head == NULL);

        if (list_empty(i->head))
                free_irq(up->port.irq, i);

        serial_do_unlink(i, up);
        mutex_unlock(&hash_mutex);
}

/*
 * This function is used to handle ports that do not have an
 * interrupt.  This doesn't work very well for 16450's, but gives
 * barely passable results for a 16550A.  (Although at the expense
 * of much CPU overhead).
 */
static void serial8250_timeout(struct timer_list *t)
{
        struct uart_8250_port *up = from_timer(up, t, timer);

        up->port.handle_irq(&up->port);
        mod_timer(&up->timer, jiffies + uart_poll_timeout(&up->port));
}

static void serial8250_backup_timeout(struct timer_list *t)
{
        struct uart_8250_port *up = from_timer(up, t, timer);
        unsigned int iir, ier = 0, lsr;
        unsigned long flags;

        spin_lock_irqsave(&up->port.lock, flags);

        /*
         * Must disable interrupts or else we risk racing with the interrupt
         * based handler.
         */
        if (up->port.irq) {
                ier = serial_in(up, UART_IER);
                serial_out(up, UART_IER, 0);
        }

        iir = serial_in(up, UART_IIR);

        /*
         * This should be a safe test for anyone who doesn't trust the
         * IIR bits on their UART, but it's specifically designed for
         * the "Diva" UART used on the management processor on many HP
         * ia64 and parisc boxes.
         */
        lsr = serial_in(up, UART_LSR);
        up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;
        if ((iir & UART_IIR_NO_INT) && (up->ier & UART_IER_THRI) &&
            (!uart_circ_empty(&up->port.state->xmit) || up->port.x_char) &&
            (lsr & UART_LSR_THRE)) {
                iir &= ~(UART_IIR_ID | UART_IIR_NO_INT);
                iir |= UART_IIR_THRI;
        }

        if (!(iir & UART_IIR_NO_INT))
                serial8250_tx_chars(up);

        if (up->port.irq)
                serial_out(up, UART_IER, ier);

        spin_unlock_irqrestore(&up->port.lock, flags);

        /* Standard timer interval plus 0.2s to keep the port running */
        mod_timer(&up->timer,
                jiffies + uart_poll_timeout(&up->port) + HZ / 5);
}

static int univ8250_setup_irq(struct uart_8250_port *up)
{
        struct uart_port *port = &up->port;
        int retval = 0;

        /*
         * The above check will only give an accurate result the first time
         * the port is opened so this value needs to be preserved.
         */
        if (up->bugs & UART_BUG_THRE) {
                pr_debug("%s - using backup timer\n", port->name);

                up->timer.function = serial8250_backup_timeout;
                mod_timer(&up->timer, jiffies +
                          uart_poll_timeout(port) + HZ / 5);
        }

        /*
         * If the "interrupt" for this port doesn't correspond with any
         * hardware interrupt, we use a timer-based system.  The original
         * driver used to do this with IRQ0.
         */
        if (!port->irq) {
                mod_timer(&up->timer, jiffies + uart_poll_timeout(port));
        } else
                retval = serial_link_irq_chain(up);

        return retval;
}

static void univ8250_release_irq(struct uart_8250_port *up)
{
        struct uart_port *port = &up->port;

        del_timer_sync(&up->timer);
        up->timer.function = serial8250_timeout;
        if (port->irq)
                serial_unlink_irq_chain(up);
}

#ifdef CONFIG_SERIAL_8250_RSA
static int serial8250_request_rsa_resource(struct uart_8250_port *up)
{
        unsigned long start = UART_RSA_BASE << up->port.regshift;
        unsigned int size = 8 << up->port.regshift;
        struct uart_port *port = &up->port;
        int ret = -EINVAL;

        switch (port->iotype) {
        case UPIO_HUB6:
        case UPIO_PORT:
                start += port->iobase;
                if (request_region(start, size, "serial-rsa"))
                        ret = 0;
                else
                        ret = -EBUSY;
                break;
        }

        return ret;
}

static void serial8250_release_rsa_resource(struct uart_8250_port *up)
{
        unsigned long offset = UART_RSA_BASE << up->port.regshift;
        unsigned int size = 8 << up->port.regshift;
        struct uart_port *port = &up->port;

        switch (port->iotype) {
        case UPIO_HUB6:
        case UPIO_PORT:
                release_region(port->iobase + offset, size);
                break;
        }
}
#endif

static const struct uart_ops *base_ops;
static struct uart_ops univ8250_port_ops;

static const struct uart_8250_ops univ8250_driver_ops = {
        .setup_irq      = univ8250_setup_irq,
        .release_irq    = univ8250_release_irq,
};

static struct uart_8250_port serial8250_ports[UART_NR];

/**
 * serial8250_get_port - retrieve struct uart_8250_port
 * @line: serial line number
 *
 * This function retrieves struct uart_8250_port for the specific line.
 * This struct *must* *not* be used to perform a 8250 or serial core operation
 * which is not accessible otherwise. Its only purpose is to make the struct
 * accessible to the runtime-pm callbacks for context suspend/restore.
 * The lock assumption made here is none because runtime-pm suspend/resume
 * callbacks should not be invoked if there is any operation performed on the
 * port.
 */
struct uart_8250_port *serial8250_get_port(int line)
{
        return &serial8250_ports[line];
}
EXPORT_SYMBOL_GPL(serial8250_get_port);

static void (*serial8250_isa_config)(int port, struct uart_port *up,
        u32 *capabilities);

void serial8250_set_isa_configurator(
        void (*v)(int port, struct uart_port *up, u32 *capabilities))
{
        serial8250_isa_config = v;
}
EXPORT_SYMBOL(serial8250_set_isa_configurator);

#ifdef CONFIG_SERIAL_8250_RSA

static void univ8250_config_port(struct uart_port *port, int flags)
{
        struct uart_8250_port *up = up_to_u8250p(port);

        up->probe &= ~UART_PROBE_RSA;
        if (port->type == PORT_RSA) {
                if (serial8250_request_rsa_resource(up) == 0)
                        up->probe |= UART_PROBE_RSA;
        } else if (flags & UART_CONFIG_TYPE) {
                int i;

                for (i = 0; i < probe_rsa_count; i++) {
                        if (probe_rsa[i] == up->port.iobase) {
                                if (serial8250_request_rsa_resource(up) == 0)
                                        up->probe |= UART_PROBE_RSA;
                                break;
                        }
                }
        }

        base_ops->config_port(port, flags);

        if (port->type != PORT_RSA && up->probe & UART_PROBE_RSA)
                serial8250_release_rsa_resource(up);
}

static int univ8250_request_port(struct uart_port *port)
{
        struct uart_8250_port *up = up_to_u8250p(port);
        int ret;

        ret = base_ops->request_port(port);
        if (ret == 0 && port->type == PORT_RSA) {
                ret = serial8250_request_rsa_resource(up);
                if (ret < 0)
                        base_ops->release_port(port);
        }

        return ret;
}

static void univ8250_release_port(struct uart_port *port)
{
        struct uart_8250_port *up = up_to_u8250p(port);

        if (port->type == PORT_RSA)
                serial8250_release_rsa_resource(up);
        base_ops->release_port(port);
}

static void univ8250_rsa_support(struct uart_ops *ops)
{
        ops->config_port  = univ8250_config_port;
        ops->request_port = univ8250_request_port;
        ops->release_port = univ8250_release_port;
}

#else
#define univ8250_rsa_support(x)         do { } while (0)
#endif /* CONFIG_SERIAL_8250_RSA */

static inline void serial8250_apply_quirks(struct uart_8250_port *up)
{
        up->port.quirks |= skip_txen_test ? UPQ_NO_TXEN_TEST : 0;
}

static void __init serial8250_isa_init_ports(void)
{
        struct uart_8250_port *up;
        static int first = 1;
        int i, irqflag = 0;

        if (!first)
                return;
        first = 0;

        if (nr_uarts > UART_NR)
                nr_uarts = UART_NR;

        for (i = 0; i < nr_uarts; i++) {
                struct uart_8250_port *up = &serial8250_ports[i];
                struct uart_port *port = &up->port;

                port->line = i;
                serial8250_init_port(up);
                if (!base_ops)
                        base_ops = port->ops;
                port->ops = &univ8250_port_ops;

                timer_setup(&up->timer, serial8250_timeout, 0);

                up->ops = &univ8250_driver_ops;

                /*
                 * ALPHA_KLUDGE_MCR needs to be killed.
                 */
                up->mcr_mask = ~ALPHA_KLUDGE_MCR;
                up->mcr_force = ALPHA_KLUDGE_MCR;
                serial8250_set_defaults(up);
        }

        /* chain base port ops to support Remote Supervisor Adapter */
        univ8250_port_ops = *base_ops;
        univ8250_rsa_support(&univ8250_port_ops);

        if (share_irqs)
                irqflag = IRQF_SHARED;

        for (i = 0, up = serial8250_ports;
             i < ARRAY_SIZE(old_serial_port) && i < nr_uarts;
             i++, up++) {
                struct uart_port *port = &up->port;

                port->iobase   = old_serial_port[i].port;
                port->irq      = irq_canonicalize(old_serial_port[i].irq);
                port->irqflags = 0;
                port->uartclk  = old_serial_port[i].baud_base * 16;
                port->flags    = old_serial_port[i].flags;
                port->hub6     = 0;
                port->membase  = old_serial_port[i].iomem_base;
                port->iotype   = old_serial_port[i].io_type;
                port->regshift = old_serial_port[i].iomem_reg_shift;

                port->irqflags |= irqflag;
                if (serial8250_isa_config != NULL)
                        serial8250_isa_config(i, &up->port, &up->capabilities);
        }
}

static void __init
serial8250_register_ports(struct uart_driver *drv, struct device *dev)
{
        int i;

        for (i = 0; i < nr_uarts; i++) {
                struct uart_8250_port *up = &serial8250_ports[i];

                if (up->port.type == PORT_8250_CIR)
                        continue;

                if (up->port.dev)
                        continue;

                up->port.dev = dev;

                serial8250_apply_quirks(up);
                uart_add_one_port(drv, &up->port);
        }
}

#ifdef CONFIG_SERIAL_8250_CONSOLE

static void univ8250_console_write(struct console *co, const char *s,
                                   unsigned int count)
{
        struct uart_8250_port *up = &serial8250_ports[co->index];

        serial8250_console_write(up, s, count);
}

static int univ8250_console_setup(struct console *co, char *options)
{
        struct uart_port *port;
        int retval;

        /*
         * Check whether an invalid uart number has been specified, and
         * if so, search for the first available port that does have
         * console support.
         */
        if (co->index >= nr_uarts)
                co->index = 0;
        port = &serial8250_ports[co->index].port;
        /* link port to console */
        port->cons = co;

        retval = serial8250_console_setup(port, options, false);
        if (retval != 0)
                port->cons = NULL;
        return retval;
}

static int univ8250_console_exit(struct console *co)
{
        struct uart_port *port;

        port = &serial8250_ports[co->index].port;
        return serial8250_console_exit(port);
}

/**
 *      univ8250_console_match - non-standard console matching
 *      @co:      registering console
 *      @name:    name from console command line
 *      @idx:     index from console command line
 *      @options: ptr to option string from console command line
 *
 *      Only attempts to match console command lines of the form:
 *          console=uart[8250],io|mmio|mmio16|mmio32,<addr>[,<options>]
 *          console=uart[8250],0x<addr>[,<options>]
 *      This form is used to register an initial earlycon boot console and
 *      replace it with the serial8250_console at 8250 driver init.
 *
 *      Performs console setup for a match (as required by interface)
 *      If no <options> are specified, then assume the h/w is already setup.
 *
 *      Returns 0 if console matches; otherwise non-zero to use default matching
 */
static int univ8250_console_match(struct console *co, char *name, int idx,
                                  char *options)
{
        char match[] = "uart";  /* 8250-specific earlycon name */
        unsigned char iotype;
        resource_size_t addr;
        int i;

        if (strncmp(name, match, 4) != 0)
                return -ENODEV;

        if (uart_parse_earlycon(options, &iotype, &addr, &options))
                return -ENODEV;

        /* try to match the port specified on the command line */
        for (i = 0; i < nr_uarts; i++) {
                struct uart_port *port = &serial8250_ports[i].port;

                if (port->iotype != iotype)
                        continue;
                if ((iotype == UPIO_MEM || iotype == UPIO_MEM16 ||
                     iotype == UPIO_MEM32 || iotype == UPIO_MEM32BE)
                    && (port->mapbase != addr))
                        continue;
                if (iotype == UPIO_PORT && port->iobase != addr)
                        continue;

                co->index = i;
                port->cons = co;
                return serial8250_console_setup(port, options, true);
        }

        return -ENODEV;
}

static struct console univ8250_console = {
        .name           = "ttyS",
        .write          = univ8250_console_write,
        .device         = uart_console_device,
        .setup          = univ8250_console_setup,
        .exit           = univ8250_console_exit,
        .match          = univ8250_console_match,
        .flags          = CON_PRINTBUFFER | CON_ANYTIME,
        .index          = -1,
        .data           = &serial8250_reg,
};

static int __init univ8250_console_init(void)
{
        if (nr_uarts == 0)
                return -ENODEV;

        serial8250_isa_init_ports();
        register_console(&univ8250_console);
        return 0;
}
console_initcall(univ8250_console_init);

#define SERIAL8250_CONSOLE      (&univ8250_console)
#else
#define SERIAL8250_CONSOLE      NULL
#endif

static struct uart_driver serial8250_reg = {
        .owner                  = THIS_MODULE,
        .driver_name            = "serial",
        .dev_name               = "ttyS",
        .major                  = TTY_MAJOR,
        .minor                  = 64,
        .cons                   = SERIAL8250_CONSOLE,
};

/*
 * early_serial_setup - early registration for 8250 ports
 *
 * Setup an 8250 port structure prior to console initialisation.  Use
 * after console initialisation will cause undefined behaviour.
 */
int __init early_serial_setup(struct uart_port *port)
{
        struct uart_port *p;

        if (port->line >= ARRAY_SIZE(serial8250_ports) || nr_uarts == 0)
                return -ENODEV;

        serial8250_isa_init_ports();
        p = &serial8250_ports[port->line].port;
        p->iobase       = port->iobase;
        p->membase      = port->membase;
        p->irq          = port->irq;
        p->irqflags     = port->irqflags;
        p->uartclk      = port->uartclk;
        p->fifosize     = port->fifosize;
        p->regshift     = port->regshift;
        p->iotype       = port->iotype;
        p->flags        = port->flags;
        p->mapbase      = port->mapbase;
        p->mapsize      = port->mapsize;
        p->private_data = port->private_data;
        p->type         = port->type;
        p->line         = port->line;

        serial8250_set_defaults(up_to_u8250p(p));

        if (port->serial_in)
                p->serial_in = port->serial_in;
        if (port->serial_out)
                p->serial_out = port->serial_out;
        if (port->handle_irq)
                p->handle_irq = port->handle_irq;

        return 0;
}

/**
 *      serial8250_suspend_port - suspend one serial port
 *      @line:  serial line number
 *
 *      Suspend one serial port.
 */
void serial8250_suspend_port(int line)
{
        struct uart_8250_port *up = &serial8250_ports[line];
        struct uart_port *port = &up->port;

        if (!console_suspend_enabled && uart_console(port) &&
            port->type != PORT_8250) {
                unsigned char canary = 0xa5;
                serial_out(up, UART_SCR, canary);
                if (serial_in(up, UART_SCR) == canary)
                        up->canary = canary;
        }

        uart_suspend_port(&serial8250_reg, port);
}
EXPORT_SYMBOL(serial8250_suspend_port);

/**
 *      serial8250_resume_port - resume one serial port
 *      @line:  serial line number
 *
 *      Resume one serial port.
 */
void serial8250_resume_port(int line)
{
        struct uart_8250_port *up = &serial8250_ports[line];
        struct uart_port *port = &up->port;

        up->canary = 0;

        if (up->capabilities & UART_NATSEMI) {
                /* Ensure it's still in high speed mode */
                serial_port_out(port, UART_LCR, 0xE0);

                ns16550a_goto_highspeed(up);

                serial_port_out(port, UART_LCR, 0);
                port->uartclk = 921600*16;
        }
        uart_resume_port(&serial8250_reg, port);
}
EXPORT_SYMBOL(serial8250_resume_port);

/*
 * Register a set of serial devices attached to a platform device.  The
 * list is terminated with a zero flags entry, which means we expect
 * all entries to have at least UPF_BOOT_AUTOCONF set.
 */
static int serial8250_probe(struct platform_device *dev)
{
        struct plat_serial8250_port *p = dev_get_platdata(&dev->dev);
        struct uart_8250_port uart;
        int ret, i, irqflag = 0;

        memset(&uart, 0, sizeof(uart));

        if (share_irqs)
                irqflag = IRQF_SHARED;

        for (i = 0; p && p->flags != 0; p++, i++) {
                uart.port.iobase        = p->iobase;
                uart.port.membase       = p->membase;
                uart.port.irq           = p->irq;
                uart.port.irqflags      = p->irqflags;
                uart.port.uartclk       = p->uartclk;
                uart.port.regshift      = p->regshift;
                uart.port.iotype        = p->iotype;
                uart.port.flags         = p->flags;
                uart.port.mapbase       = p->mapbase;
                uart.port.hub6          = p->hub6;
                uart.port.has_sysrq     = p->has_sysrq;
                uart.port.private_data  = p->private_data;
                uart.port.type          = p->type;
                uart.port.serial_in     = p->serial_in;
                uart.port.serial_out    = p->serial_out;
                uart.port.handle_irq    = p->handle_irq;
                uart.port.handle_break  = p->handle_break;
                uart.port.set_termios   = p->set_termios;
                uart.port.set_ldisc     = p->set_ldisc;
                uart.port.get_mctrl     = p->get_mctrl;
                uart.port.pm            = p->pm;
                uart.port.dev           = &dev->dev;
                uart.port.irqflags      |= irqflag;
                ret = serial8250_register_8250_port(&uart);
                if (ret < 0) {
                        dev_err(&dev->dev, "unable to register port at index %d "
                                "(IO%lx MEM%llx IRQ%d): %d\n", i,
                                p->iobase, (unsigned long long)p->mapbase,
                                p->irq, ret);
                }
        }
        return 0;
}

/*
 * Remove serial ports registered against a platform device.
 */
static int serial8250_remove(struct platform_device *dev)
{
        int i;

        for (i = 0; i < nr_uarts; i++) {
                struct uart_8250_port *up = &serial8250_ports[i];

                if (up->port.dev == &dev->dev)
                        serial8250_unregister_port(i);
        }
        return 0;
}

static int serial8250_suspend(struct platform_device *dev, pm_message_t state)
{
        int i;

        for (i = 0; i < UART_NR; i++) {
                struct uart_8250_port *up = &serial8250_ports[i];

                if (up->port.type != PORT_UNKNOWN && up->port.dev == &dev->dev)
                        uart_suspend_port(&serial8250_reg, &up->port);
        }

        return 0;
}

static int serial8250_resume(struct platform_device *dev)
{
        int i;

        for (i = 0; i < UART_NR; i++) {
                struct uart_8250_port *up = &serial8250_ports[i];

                if (up->port.type != PORT_UNKNOWN && up->port.dev == &dev->dev)
                        serial8250_resume_port(i);
        }

        return 0;
}

static struct platform_driver serial8250_isa_driver = {
        .probe          = serial8250_probe,
        .remove         = serial8250_remove,
        .suspend        = serial8250_suspend,
        .resume         = serial8250_resume,
        .driver         = {
                .name   = "serial8250",
        },
};

/*
 * This "device" covers _all_ ISA 8250-compatible serial devices listed
 * in the table in include/asm/serial.h
 */
static struct platform_device *serial8250_isa_devs;

/*
 * serial8250_register_8250_port and serial8250_unregister_port allows for
 * 16x50 serial ports to be configured at run-time, to support PCMCIA
 * modems and PCI multiport cards.
 */
static DEFINE_MUTEX(serial_mutex);

static struct uart_8250_port *serial8250_find_match_or_unused(struct uart_port *port)
{
        int i;

        /*
         * First, find a port entry which matches.
         */
        for (i = 0; i < nr_uarts; i++)
                if (uart_match_port(&serial8250_ports[i].port, port))
                        return &serial8250_ports[i];

        /* try line number first if still available */
        i = port->line;
        if (i < nr_uarts && serial8250_ports[i].port.type == PORT_UNKNOWN &&
                        serial8250_ports[i].port.iobase == 0)
                return &serial8250_ports[i];
        /*
         * We didn't find a matching entry, so look for the first
         * free entry.  We look for one which hasn't been previously
         * used (indicated by zero iobase).
         */
        for (i = 0; i < nr_uarts; i++)
                if (serial8250_ports[i].port.type == PORT_UNKNOWN &&
                    serial8250_ports[i].port.iobase == 0)
                        return &serial8250_ports[i];

        /*
         * That also failed.  Last resort is to find any entry which
         * doesn't have a real port associated with it.
         */
        for (i = 0; i < nr_uarts; i++)
                if (serial8250_ports[i].port.type == PORT_UNKNOWN)
                        return &serial8250_ports[i];

        return NULL;
}

static void serial_8250_overrun_backoff_work(struct work_struct *work)
{
        struct uart_8250_port *up =
            container_of(to_delayed_work(work), struct uart_8250_port,
                         overrun_backoff);
        struct uart_port *port = &up->port;
        unsigned long flags;

        spin_lock_irqsave(&port->lock, flags);
        up->ier |= UART_IER_RLSI | UART_IER_RDI;
        up->port.read_status_mask |= UART_LSR_DR;
        serial_out(up, UART_IER, up->ier);
        spin_unlock_irqrestore(&port->lock, flags);
}

/**
 *      serial8250_register_8250_port - register a serial port
 *      @up: serial port template
 *
 *      Configure the serial port specified by the request. If the
 *      port exists and is in use, it is hung up and unregistered
 *      first.
 *
 *      The port is then probed and if necessary the IRQ is autodetected
 *      If this fails an error is returned.
 *
 *      On success the port is ready to use and the line number is returned.
 */
int serial8250_register_8250_port(struct uart_8250_port *up)
{
        struct uart_8250_port *uart;
        int ret = -ENOSPC;

        if (up->port.uartclk == 0)
                return -EINVAL;

        mutex_lock(&serial_mutex);

        uart = serial8250_find_match_or_unused(&up->port);
        if (uart && uart->port.type != PORT_8250_CIR) {
                struct mctrl_gpios *gpios;

                if (uart->port.dev)
                        uart_remove_one_port(&serial8250_reg, &uart->port);

                uart->port.iobase       = up->port.iobase;
                uart->port.membase      = up->port.membase;
                uart->port.irq          = up->port.irq;
                uart->port.irqflags     = up->port.irqflags;
                uart->port.uartclk      = up->port.uartclk;
                uart->port.fifosize     = up->port.fifosize;
                uart->port.regshift     = up->port.regshift;
                uart->port.iotype       = up->port.iotype;
                uart->port.flags        = up->port.flags | UPF_BOOT_AUTOCONF;
                uart->bugs              = up->bugs;
                uart->port.mapbase      = up->port.mapbase;
                uart->port.mapsize      = up->port.mapsize;
                uart->port.private_data = up->port.private_data;
                uart->tx_loadsz         = up->tx_loadsz;
                uart->capabilities      = up->capabilities;
                uart->port.throttle     = up->port.throttle;
                uart->port.unthrottle   = up->port.unthrottle;
                uart->port.rs485_config = up->port.rs485_config;
                uart->port.rs485        = up->port.rs485;
                uart->rs485_start_tx    = up->rs485_start_tx;
                uart->rs485_stop_tx     = up->rs485_stop_tx;
                uart->dma               = up->dma;

                /* Take tx_loadsz from fifosize if it wasn't set separately */
                if (uart->port.fifosize && !uart->tx_loadsz)
                        uart->tx_loadsz = uart->port.fifosize;

                if (up->port.dev) {
                        uart->port.dev = up->port.dev;
                        ret = uart_get_rs485_mode(&uart->port);
                        if (ret)
                                goto err;
                }

                if (up->port.flags & UPF_FIXED_TYPE)
                        uart->port.type = up->port.type;

                /*
                 * Only call mctrl_gpio_init(), if the device has no ACPI
                 * companion device
                 */
                if (!has_acpi_companion(uart->port.dev)) {
                        gpios = mctrl_gpio_init(&uart->port, 0);
                        if (IS_ERR(gpios)) {
                                ret = PTR_ERR(gpios);
                                goto err;
                        } else {
                                uart->gpios = gpios;
                        }
                }

                serial8250_set_defaults(uart);

                /* Possibly override default I/O functions.  */
                if (up->port.serial_in)
                        uart->port.serial_in = up->port.serial_in;
                if (up->port.serial_out)
                        uart->port.serial_out = up->port.serial_out;
                if (up->port.handle_irq)
                        uart->port.handle_irq = up->port.handle_irq;
                /*  Possibly override set_termios call */
                if (up->port.set_termios)
                        uart->port.set_termios = up->port.set_termios;
                if (up->port.set_ldisc)
                        uart->port.set_ldisc = up->port.set_ldisc;
                if (up->port.get_mctrl)
                        uart->port.get_mctrl = up->port.get_mctrl;
                if (up->port.set_mctrl)
                        uart->port.set_mctrl = up->port.set_mctrl;
                if (up->port.get_divisor)
                        uart->port.get_divisor = up->port.get_divisor;
                if (up->port.set_divisor)
                        uart->port.set_divisor = up->port.set_divisor;
                if (up->port.startup)
                        uart->port.startup = up->port.startup;
                if (up->port.shutdown)
                        uart->port.shutdown = up->port.shutdown;
                if (up->port.pm)
                        uart->port.pm = up->port.pm;
                if (up->port.handle_break)
                        uart->port.handle_break = up->port.handle_break;
                if (up->dl_read)
                        uart->dl_read = up->dl_read;
                if (up->dl_write)
                        uart->dl_write = up->dl_write;

                if (uart->port.type != PORT_8250_CIR) {
                        if (serial8250_isa_config != NULL)
                                serial8250_isa_config(0, &uart->port,
                                                &uart->capabilities);

                        serial8250_apply_quirks(uart);
                        ret = uart_add_one_port(&serial8250_reg,
                                                &uart->port);
                        if (ret)
                                goto err;

                        ret = uart->port.line;
                } else {
                        dev_info(uart->port.dev,
                                "skipping CIR port at 0x%lx / 0x%llx, IRQ %d\n",
                                uart->port.iobase,
                                (unsigned long long)uart->port.mapbase,
                                uart->port.irq);

                        ret = 0;
                }

                /* Initialise interrupt backoff work if required */
                if (up->overrun_backoff_time_ms > 0) {
                        uart->overrun_backoff_time_ms =
                                up->overrun_backoff_time_ms;
                        INIT_DELAYED_WORK(&uart->overrun_backoff,
                                        serial_8250_overrun_backoff_work);
                } else {
                        uart->overrun_backoff_time_ms = 0;
                }
        }

        mutex_unlock(&serial_mutex);

        return ret;

err:
        uart->port.dev = NULL;
        mutex_unlock(&serial_mutex);
        return ret;
}
EXPORT_SYMBOL(serial8250_register_8250_port);

/**
 *      serial8250_unregister_port - remove a 16x50 serial port at runtime
 *      @line: serial line number
 *
 *      Remove one serial port.  This may not be called from interrupt
 *      context.  We hand the port back to the our control.
 */
void serial8250_unregister_port(int line)
{
        struct uart_8250_port *uart = &serial8250_ports[line];

        mutex_lock(&serial_mutex);

        if (uart->em485) {
                unsigned long flags;

                spin_lock_irqsave(&uart->port.lock, flags);
                serial8250_em485_destroy(uart);
                spin_unlock_irqrestore(&uart->port.lock, flags);
        }

        uart_remove_one_port(&serial8250_reg, &uart->port);
        if (serial8250_isa_devs) {
                uart->port.flags &= ~UPF_BOOT_AUTOCONF;
                uart->port.type = PORT_UNKNOWN;
                uart->port.dev = &serial8250_isa_devs->dev;
                uart->capabilities = 0;
                serial8250_apply_quirks(uart);
                uart_add_one_port(&serial8250_reg, &uart->port);
        } else {
                uart->port.dev = NULL;
        }
        mutex_unlock(&serial_mutex);
}
EXPORT_SYMBOL(serial8250_unregister_port);

static int __init serial8250_init(void)
{
        int ret;

        if (nr_uarts == 0)
                return -ENODEV;

        serial8250_isa_init_ports();

        pr_info("Serial: 8250/16550 driver, %d ports, IRQ sharing %sabled\n",
                nr_uarts, share_irqs ? "en" : "dis");

#ifdef CONFIG_SPARC
        ret = sunserial_register_minors(&serial8250_reg, UART_NR);
#else
        serial8250_reg.nr = UART_NR;
        ret = uart_register_driver(&serial8250_reg);
#endif
        if (ret)
                goto out;

        ret = serial8250_pnp_init();
        if (ret)
                goto unreg_uart_drv;

        serial8250_isa_devs = platform_device_alloc("serial8250",
                                                    PLAT8250_DEV_LEGACY);
        if (!serial8250_isa_devs) {
                ret = -ENOMEM;
                goto unreg_pnp;
        }

        ret = platform_device_add(serial8250_isa_devs);
        if (ret)
                goto put_dev;

        serial8250_register_ports(&serial8250_reg, &serial8250_isa_devs->dev);

        ret = platform_driver_register(&serial8250_isa_driver);
        if (ret == 0)
                goto out;

        platform_device_del(serial8250_isa_devs);
put_dev:
        platform_device_put(serial8250_isa_devs);
unreg_pnp:
        serial8250_pnp_exit();
unreg_uart_drv:
#ifdef CONFIG_SPARC
        sunserial_unregister_minors(&serial8250_reg, UART_NR);
#else
        uart_unregister_driver(&serial8250_reg);
#endif
out:
        return ret;
}

static void __exit serial8250_exit(void)
{
        struct platform_device *isa_dev = serial8250_isa_devs;

        /*
         * This tells serial8250_unregister_port() not to re-register
         * the ports (thereby making serial8250_isa_driver permanently
         * in use.)
         */
        serial8250_isa_devs = NULL;

        platform_driver_unregister(&serial8250_isa_driver);
        platform_device_unregister(isa_dev);

        serial8250_pnp_exit();

#ifdef CONFIG_SPARC
        sunserial_unregister_minors(&serial8250_reg, UART_NR);
#else
        uart_unregister_driver(&serial8250_reg);
#endif
}

module_init(serial8250_init);
module_exit(serial8250_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Generic 8250/16x50 serial driver");

module_param_hw(share_irqs, uint, other, 0644);
MODULE_PARM_DESC(share_irqs, "Share IRQs with other non-8250/16x50 devices (unsafe)");

module_param(nr_uarts, uint, 0644);
MODULE_PARM_DESC(nr_uarts, "Maximum number of UARTs supported. (1-" __MODULE_STRING(CONFIG_SERIAL_8250_NR_UARTS) ")");

module_param(skip_txen_test, uint, 0644);
MODULE_PARM_DESC(skip_txen_test, "Skip checking for the TXEN bug at init time");

#ifdef CONFIG_SERIAL_8250_RSA
module_param_hw_array(probe_rsa, ulong, ioport, &probe_rsa_count, 0444);
MODULE_PARM_DESC(probe_rsa, "Probe I/O ports for RSA");
#endif
MODULE_ALIAS_CHARDEV_MAJOR(TTY_MAJOR);

#ifdef CONFIG_SERIAL_8250_DEPRECATED_OPTIONS
#ifndef MODULE
/* This module was renamed to 8250_core in 3.7.  Keep the old "8250" name
 * working as well for the module options so we don't break people.  We
 * need to keep the names identical and the convenient macros will happily
 * refuse to let us do that by failing the build with redefinition errors
 * of global variables.  So we stick them inside a dummy function to avoid
 * those conflicts.  The options still get parsed, and the redefined
 * MODULE_PARAM_PREFIX lets us keep the "8250." syntax alive.
 *
 * This is hacky.  I'm sorry.
 */
static void __used s8250_options(void)
{
#undef MODULE_PARAM_PREFIX
#define MODULE_PARAM_PREFIX "8250_core."

        module_param_cb(share_irqs, &param_ops_uint, &share_irqs, 0644);
        module_param_cb(nr_uarts, &param_ops_uint, &nr_uarts, 0644);
        module_param_cb(skip_txen_test, &param_ops_uint, &skip_txen_test, 0644);
#ifdef CONFIG_SERIAL_8250_RSA
        __module_param_call(MODULE_PARAM_PREFIX, probe_rsa,
                &param_array_ops, .arr = &__param_arr_probe_rsa,
                0444, -1, 0);
#endif
}
#else
MODULE_ALIAS("8250_core");
#endif
#endif