OpenHarmony-v5.1.0-Release/s

// 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/pm_runtime.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 */
#define CORE_FIVE 5
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 / CORE_FIVE);
}

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 / CORE_FIVE);
    }

    /*
     * 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;
        default:
            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;
        default:
            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)
{
#ifndef CONFIG_ARCH_ROCKCHIP
    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;
        if (uart_console_enabled(&up->port))
            pm_runtime_get_sync(up->port.dev);

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

#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, 0x4) != 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 = 0xe10000;
    }
    uart_resume_port(&serial8250_reg, port);
}
EXPORT_SYMBOL(serial8250_resume_port);

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 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);

/**
 *    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;
#ifdef CONFIG_ARCH_ROCKCHIP
        uart->port.line = up->port.line;
#endif
        /* 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);

/*
 * 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_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
}

#ifdef CONFIG_ROCKCHIP_THUNDER_BOOT
rootfs_initcall(serial8250_init);
#else
module_init(serial8250_init);
#endif
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