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/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/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 irq_info *i;
	int ret;

	mutex_lock(&hash_mutex);

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

	hlist_for_each_entry(i, h, node)
		if (i->irq == up->port.irq)
			break;

	if (i == 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)
{
	struct irq_info *i;
	struct hlist_head *h;

	mutex_lock(&hash_mutex);

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

	hlist_for_each_entry(i, h, node)
		if (i->irq == up->port.irq)
			break;

	BUG_ON(i == 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_lsr_in(up);
	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 void univ8250_setup_timer(struct uart_8250_port *up)
{
	struct uart_port *port = &up->port;

	/*
	 * 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));
}

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

	if (port->irq)
		return serial_link_irq_chain(up);

	return 0;
}

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,
	.setup_timer	= univ8250_setup_timer,
};

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;

		if (IS_ENABLED(CONFIG_ALPHA_JENSEN) ||
		    (IS_ENABLED(CONFIG_ALPHA_GENERIC) && alpha_jensen()))
			port->set_mctrl = alpha_jensen_set_mctrl;

		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;

		if (uart_console_enabled(&up->port))
			pm_runtime_get_sync(up->port.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(const 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(const 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_supported = up->port.rs485_supported;
		uart->port.rs485	= up->port.rs485;
		uart->rs485_start_tx	= up->rs485_start_tx;
		uart->rs485_stop_tx	= up->rs485_stop_tx;
		uart->lsr_save_mask	= up->lsr_save_mask;
		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;
		}

		if (!uart->lsr_save_mask)
			uart->lsr_save_mask = LSR_SAVE_FLAGS;	/* Use default LSR mask */

		/* 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