/*
 *  linux/drivers/char/8250.c
 *
 *  Driver for 8250/16550-type serial ports
 *
 *  Based on drivers/char/serial.c, by Linus Torvalds, Theodore Ts'o.
 *
 *  Copyright (C) 2001 Russell King.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * A note about mapbase / membase
 *
 *  mapbase is the physical address of the IO port.
 *  membase is an 'ioremapped' cookie.
 */

#if defined(CONFIG_SERIAL_8250_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
#define SUPPORT_SYSRQ
#endif

#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/tty_flip.h>
#include <linux/serial_reg.h>
#include <linux/serial_core.h>
#include <linux/serial.h>
#include <linux/serial_8250.h>
#include <linux/nmi.h>
#include <linux/mutex.h>

#include <asm/io.h>
#include <asm/irq.h>

#include "8250.h"

#ifdef CONFIG_SPARC
#include "suncore.h"
#endif

/*
 * 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 int serial_index(struct uart_port *port)
{
        return (serial8250_reg.minor - 64) + port->line;
}

/*
 * Debugging.
 */
#if 0
#define DEBUG_AUTOCONF(fmt...)  printk(fmt)
#else
#define DEBUG_AUTOCONF(fmt...)  do { } while (0)
#endif

#if 0
#define DEBUG_INTR(fmt...)      printk(fmt)
#else
#define DEBUG_INTR(fmt...)      do { } while (0)
#endif

#define PASS_LIMIT      256

/*
 * We default to IRQ0 for the "no irq" hack.   Some
 * machine types want others as well - they're free
 * to redefine this in their header file.
 */
#define is_real_interrupt(irq)  ((irq) != 0)

#ifdef CONFIG_SERIAL_8250_DETECT_IRQ
#define CONFIG_SERIAL_DETECT_IRQ 1
#endif
#ifdef CONFIG_SERIAL_8250_MANY_PORTS
#define CONFIG_SERIAL_MANY_PORTS 1
#endif

/*
 * HUB6 is always on.  This will be removed once the header
 * files have been cleaned.
 */
#define CONFIG_HUB6 1

#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 uart_8250_port {
        struct uart_port        port;
        struct timer_list       timer;          /* "no irq" timer */
        struct list_head        list;           /* ports on this IRQ */
        unsigned short          capabilities;   /* port capabilities */
        unsigned short          bugs;           /* port bugs */
        unsigned int            tx_loadsz;      /* transmit fifo load size */
        unsigned char           acr;
        unsigned char           ier;
        unsigned char           lcr;
        unsigned char           mcr;
        unsigned char           mcr_mask;       /* mask of user bits */
        unsigned char           mcr_force;      /* mask of forced bits */

        /*
         * Some bits in registers are cleared on a read, so they must
         * be saved whenever the register is read but the bits will not
         * be immediately processed.
         */
#define LSR_SAVE_FLAGS UART_LSR_BRK_ERROR_BITS
        unsigned char           lsr_saved_flags;
#define MSR_SAVE_FLAGS UART_MSR_ANY_DELTA
        unsigned char           msr_saved_flags;

        /*
         * We provide a per-port pm hook.
         */
        void                    (*pm)(struct uart_port *port,
                                      unsigned int state, unsigned int old);
};

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 */

/*
 * Here we define the default xmit fifo size used for each type of UART.
 */
static const struct serial8250_config uart_config[] = {
        [PORT_UNKNOWN] = {
                .name           = "unknown",
                .fifo_size      = 1,
                .tx_loadsz      = 1,
        },
        [PORT_8250] = {
                .name           = "8250",
                .fifo_size      = 1,
                .tx_loadsz      = 1,
        },
        [PORT_16450] = {
                .name           = "16450",
                .fifo_size      = 1,
                .tx_loadsz      = 1,
        },
        [PORT_16550] = {
                .name           = "16550",
                .fifo_size      = 1,
                .tx_loadsz      = 1,
        },
        [PORT_16550A] = {
                .name           = "16550A",
                .fifo_size      = 16,
                .tx_loadsz      = 16,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
                .flags          = UART_CAP_FIFO,
        },
        [PORT_CIRRUS] = {
                .name           = "Cirrus",
                .fifo_size      = 1,
                .tx_loadsz      = 1,
        },
        [PORT_16650] = {
                .name           = "ST16650",
                .fifo_size      = 1,
                .tx_loadsz      = 1,
                .flags          = UART_CAP_FIFO | UART_CAP_EFR | UART_CAP_SLEEP,
        },
        [PORT_16650V2] = {
                .name           = "ST16650V2",
                .fifo_size      = 32,
                .tx_loadsz      = 16,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_01 |
                                  UART_FCR_T_TRIG_00,
                .flags          = UART_CAP_FIFO | UART_CAP_EFR | UART_CAP_SLEEP,
        },
        [PORT_16750] = {
                .name           = "TI16750",
                .fifo_size      = 64,
                .tx_loadsz      = 64,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10 |
                                  UART_FCR7_64BYTE,
                .flags          = UART_CAP_FIFO | UART_CAP_SLEEP | UART_CAP_AFE,
        },
        [PORT_STARTECH] = {
                .name           = "Startech",
                .fifo_size      = 1,
                .tx_loadsz      = 1,
        },
        [PORT_16C950] = {
                .name           = "16C950/954",
                .fifo_size      = 128,
                .tx_loadsz      = 128,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
                .flags          = UART_CAP_FIFO,
        },
        [PORT_16654] = {
                .name           = "ST16654",
                .fifo_size      = 64,
                .tx_loadsz      = 32,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_01 |
                                  UART_FCR_T_TRIG_10,
                .flags          = UART_CAP_FIFO | UART_CAP_EFR | UART_CAP_SLEEP,
        },
        [PORT_16850] = {
                .name           = "XR16850",
                .fifo_size      = 128,
                .tx_loadsz      = 128,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
                .flags          = UART_CAP_FIFO | UART_CAP_EFR | UART_CAP_SLEEP,
        },
        [PORT_RSA] = {
                .name           = "RSA",
                .fifo_size      = 2048,
                .tx_loadsz      = 2048,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_11,
                .flags          = UART_CAP_FIFO,
        },
        [PORT_NS16550A] = {
                .name           = "NS16550A",
                .fifo_size      = 16,
                .tx_loadsz      = 16,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
                .flags          = UART_CAP_FIFO | UART_NATSEMI,
        },
        [PORT_XSCALE] = {
                .name           = "XScale",
                .fifo_size      = 32,
                .tx_loadsz      = 32,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
                .flags          = UART_CAP_FIFO | UART_CAP_UUE,
        },
        [PORT_RM9000] = {
                .name           = "RM9000",
                .fifo_size      = 16,
                .tx_loadsz      = 16,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
                .flags          = UART_CAP_FIFO,
        },
};

#if defined (CONFIG_SERIAL_8250_AU1X00)

/* Au1x00 UART hardware has a weird register layout */
static const u8 au_io_in_map[] = {
        [UART_RX]  = 0,
        [UART_IER] = 2,
        [UART_IIR] = 3,
        [UART_LCR] = 5,
        [UART_MCR] = 6,
        [UART_LSR] = 7,
        [UART_MSR] = 8,
};

static const u8 au_io_out_map[] = {
        [UART_TX]  = 1,
        [UART_IER] = 2,
        [UART_FCR] = 4,
        [UART_LCR] = 5,
        [UART_MCR] = 6,
};

/* sane hardware needs no mapping */
static inline int map_8250_in_reg(struct uart_8250_port *up, int offset)
{
        if (up->port.iotype != UPIO_AU)
                return offset;
        return au_io_in_map[offset];
}

static inline int map_8250_out_reg(struct uart_8250_port *up, int offset)
{
        if (up->port.iotype != UPIO_AU)
                return offset;
        return au_io_out_map[offset];
}

#elif defined(CONFIG_SERIAL_8250_RM9K)

static const u8
        regmap_in[8] = {
                [UART_RX]       = 0x00,
                [UART_IER]      = 0x0c,
                [UART_IIR]      = 0x14,
                [UART_LCR]      = 0x1c,
                [UART_MCR]      = 0x20,
                [UART_LSR]      = 0x24,
                [UART_MSR]      = 0x28,
                [UART_SCR]      = 0x2c
        },
        regmap_out[8] = {
                [UART_TX]       = 0x04,
                [UART_IER]      = 0x0c,
                [UART_FCR]      = 0x18,
                [UART_LCR]      = 0x1c,
                [UART_MCR]      = 0x20,
                [UART_LSR]      = 0x24,
                [UART_MSR]      = 0x28,
                [UART_SCR]      = 0x2c
        };

static inline int map_8250_in_reg(struct uart_8250_port *up, int offset)
{
        if (up->port.iotype != UPIO_RM9000)
                return offset;
        return regmap_in[offset];
}

static inline int map_8250_out_reg(struct uart_8250_port *up, int offset)
{
        if (up->port.iotype != UPIO_RM9000)
                return offset;
        return regmap_out[offset];
}

#else

/* sane hardware needs no mapping */
#define map_8250_in_reg(up, offset) (offset)
#define map_8250_out_reg(up, offset) (offset)

#endif

static unsigned int serial_in(struct uart_8250_port *up, int offset)
{
        unsigned int tmp;
        offset = map_8250_in_reg(up, offset) << up->port.regshift;

        switch (up->port.iotype) {
        case UPIO_HUB6:
                outb(up->port.hub6 - 1 + offset, up->port.iobase);
                return inb(up->port.iobase + 1);

        case UPIO_MEM:
        case UPIO_DWAPB:
                return readb(up->port.membase + offset);

        case UPIO_RM9000:
        case UPIO_MEM32:
                return readl(up->port.membase + offset);

#ifdef CONFIG_SERIAL_8250_AU1X00
        case UPIO_AU:
                return __raw_readl(up->port.membase + offset);
#endif

        case UPIO_TSI:
                if (offset == UART_IIR) {
                        tmp = readl(up->port.membase + (UART_IIR & ~3));
                        return (tmp >> 16) & 0xff; /* UART_IIR % 4 == 2 */
                } else
                        return readb(up->port.membase + offset);

        default:
                return inb(up->port.iobase + offset);
        }
}

static void
serial_out(struct uart_8250_port *up, int offset, int value)
{
        /* Save the offset before it's remapped */
        int save_offset = offset;
        offset = map_8250_out_reg(up, offset) << up->port.regshift;

        switch (up->port.iotype) {
        case UPIO_HUB6:
                outb(up->port.hub6 - 1 + offset, up->port.iobase);
                outb(value, up->port.iobase + 1);
                break;

        case UPIO_MEM:
                writeb(value, up->port.membase + offset);
                break;

        case UPIO_RM9000:
        case UPIO_MEM32:
                writel(value, up->port.membase + offset);
                break;

#ifdef CONFIG_SERIAL_8250_AU1X00
        case UPIO_AU:
                __raw_writel(value, up->port.membase + offset);
                break;
#endif
        case UPIO_TSI:
                if (!((offset == UART_IER) && (value & UART_IER_UUE)))
                        writeb(value, up->port.membase + offset);
                break;

        case UPIO_DWAPB:
                /* Save the LCR value so it can be re-written when a
                 * Busy Detect interrupt occurs. */
                if (save_offset == UART_LCR)
                        up->lcr = value;
                writeb(value, up->port.membase + offset);
                /* Read the IER to ensure any interrupt is cleared before
                 * returning from ISR. */
                if (save_offset == UART_TX || save_offset == UART_IER)
                        value = serial_in(up, UART_IER);
                break;

        default:
                outb(value, up->port.iobase + offset);
        }
}

static void
serial_out_sync(struct uart_8250_port *up, int offset, int value)
{
        switch (up->port.iotype) {
        case UPIO_MEM:
        case UPIO_MEM32:
#ifdef CONFIG_SERIAL_8250_AU1X00
        case UPIO_AU:
#endif
        case UPIO_DWAPB:
                serial_out(up, offset, value);
                serial_in(up, UART_LCR);        /* safe, no side-effects */
                break;
        default:
                serial_out(up, offset, value);
        }
}

/*
 * We used to support using pause I/O for certain machines.  We
 * haven't supported this for a while, but just in case it's badly
 * needed for certain old 386 machines, I've left these #define's
 * in....
 */
#define serial_inp(up, offset)          serial_in(up, offset)
#define serial_outp(up, offset, value)  serial_out(up, offset, value)

/* Uart divisor latch read */
static inline int _serial_dl_read(struct uart_8250_port *up)
{
        return serial_inp(up, UART_DLL) | serial_inp(up, UART_DLM) << 8;
}

/* Uart divisor latch write */
static inline void _serial_dl_write(struct uart_8250_port *up, int value)
{
        serial_outp(up, UART_DLL, value & 0xff);
        serial_outp(up, UART_DLM, value >> 8 & 0xff);
}

#if defined(CONFIG_SERIAL_8250_AU1X00)
/* Au1x00 haven't got a standard divisor latch */
static int serial_dl_read(struct uart_8250_port *up)
{
        if (up->port.iotype == UPIO_AU)
                return __raw_readl(up->port.membase + 0x28);
        else
                return _serial_dl_read(up);
}

static void serial_dl_write(struct uart_8250_port *up, int value)
{
        if (up->port.iotype == UPIO_AU)
                __raw_writel(value, up->port.membase + 0x28);
        else
                _serial_dl_write(up, value);
}
#elif defined(CONFIG_SERIAL_8250_RM9K)
static int serial_dl_read(struct uart_8250_port *up)
{
        return  (up->port.iotype == UPIO_RM9000) ?
                (((__raw_readl(up->port.membase + 0x10) << 8) |
                (__raw_readl(up->port.membase + 0x08) & 0xff)) & 0xffff) :
                _serial_dl_read(up);
}

static void serial_dl_write(struct uart_8250_port *up, int value)
{
        if (up->port.iotype == UPIO_RM9000) {
                __raw_writel(value, up->port.membase + 0x08);
                __raw_writel(value >> 8, up->port.membase + 0x10);
        } else {
                _serial_dl_write(up, value);
        }
}
#else
#define serial_dl_read(up) _serial_dl_read(up)
#define serial_dl_write(up, value) _serial_dl_write(up, value)
#endif

/*
 * For the 16C950
 */
static void serial_icr_write(struct uart_8250_port *up, int offset, int value)
{
        serial_out(up, UART_SCR, offset);
        serial_out(up, UART_ICR, value);
}

static unsigned int serial_icr_read(struct uart_8250_port *up, int offset)
{
        unsigned int value;

        serial_icr_write(up, UART_ACR, up->acr | UART_ACR_ICRRD);
        serial_out(up, UART_SCR, offset);
        value = serial_in(up, UART_ICR);
        serial_icr_write(up, UART_ACR, up->acr);

        return value;
}

/*
 * FIFO support.
 */
static void serial8250_clear_fifos(struct uart_8250_port *p)
{
        if (p->capabilities & UART_CAP_FIFO) {
                serial_outp(p, UART_FCR, UART_FCR_ENABLE_FIFO);
                serial_outp(p, UART_FCR, UART_FCR_ENABLE_FIFO |
                               UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT);
                serial_outp(p, UART_FCR, 0);
        }
}

/*
 * IER sleep support.  UARTs which have EFRs need the "extended
 * capability" bit enabled.  Note that on XR16C850s, we need to
 * reset LCR to write to IER.
 */
static void serial8250_set_sleep(struct uart_8250_port *p, int sleep)
{
        if (p->capabilities & UART_CAP_SLEEP) {
                if (p->capabilities & UART_CAP_EFR) {
                        serial_outp(p, UART_LCR, 0xBF);
                        serial_outp(p, UART_EFR, UART_EFR_ECB);
                        serial_outp(p, UART_LCR, 0);
                }
                serial_outp(p, UART_IER, sleep ? UART_IERX_SLEEP : 0);
                if (p->capabilities & UART_CAP_EFR) {
                        serial_outp(p, UART_LCR, 0xBF);
                        serial_outp(p, UART_EFR, 0);
                        serial_outp(p, UART_LCR, 0);
                }
        }
}

#ifdef CONFIG_SERIAL_8250_RSA
/*
 * Attempts to turn on the RSA FIFO.  Returns zero on failure.
 * We set the port uart clock rate if we succeed.
 */
static int __enable_rsa(struct uart_8250_port *up)
{
        unsigned char mode;
        int result;

        mode = serial_inp(up, UART_RSA_MSR);
        result = mode & UART_RSA_MSR_FIFO;

        if (!result) {
                serial_outp(up, UART_RSA_MSR, mode | UART_RSA_MSR_FIFO);
                mode = serial_inp(up, UART_RSA_MSR);
                result = mode & UART_RSA_MSR_FIFO;
        }

        if (result)
                up->port.uartclk = SERIAL_RSA_BAUD_BASE * 16;

        return result;
}

static void enable_rsa(struct uart_8250_port *up)
{
        if (up->port.type == PORT_RSA) {
                if (up->port.uartclk != SERIAL_RSA_BAUD_BASE * 16) {
                        spin_lock_irq(&up->port.lock);
                        __enable_rsa(up);
                        spin_unlock_irq(&up->port.lock);
                }
                if (up->port.uartclk == SERIAL_RSA_BAUD_BASE * 16)
                        serial_outp(up, UART_RSA_FRR, 0);
        }
}

/*
 * Attempts to turn off the RSA FIFO.  Returns zero on failure.
 * It is unknown why interrupts were disabled in here.  However,
 * the caller is expected to preserve this behaviour by grabbing
 * the spinlock before calling this function.
 */
static void disable_rsa(struct uart_8250_port *up)
{
        unsigned char mode;
        int result;

        if (up->port.type == PORT_RSA &&
            up->port.uartclk == SERIAL_RSA_BAUD_BASE * 16) {
                spin_lock_irq(&up->port.lock);

                mode = serial_inp(up, UART_RSA_MSR);
                result = !(mode & UART_RSA_MSR_FIFO);

                if (!result) {
                        serial_outp(up, UART_RSA_MSR, mode & ~UART_RSA_MSR_FIFO);
                        mode = serial_inp(up, UART_RSA_MSR);
                        result = !(mode & UART_RSA_MSR_FIFO);
                }

                if (result)
                        up->port.uartclk = SERIAL_RSA_BAUD_BASE_LO * 16;
                spin_unlock_irq(&up->port.lock);
        }
}
#endif /* CONFIG_SERIAL_8250_RSA */

/*
 * This is a quickie test to see how big the FIFO is.
 * It doesn't work at all the time, more's the pity.
 */
static int size_fifo(struct uart_8250_port *up)
{
        unsigned char old_fcr, old_mcr, old_lcr;
        unsigned short old_dl;
        int count;

        old_lcr = serial_inp(up, UART_LCR);
        serial_outp(up, UART_LCR, 0);
        old_fcr = serial_inp(up, UART_FCR);
        old_mcr = serial_inp(up, UART_MCR);
        serial_outp(up, UART_FCR, UART_FCR_ENABLE_FIFO |
                    UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT);
        serial_outp(up, UART_MCR, UART_MCR_LOOP);
        serial_outp(up, UART_LCR, UART_LCR_DLAB);
        old_dl = serial_dl_read(up);
        serial_dl_write(up, 0x0001);
        serial_outp(up, UART_LCR, 0x03);
        for (count = 0; count < 256; count++)
                serial_outp(up, UART_TX, count);
        mdelay(20);/* FIXME - schedule_timeout */
        for (count = 0; (serial_inp(up, UART_LSR) & UART_LSR_DR) &&
             (count < 256); count++)
                serial_inp(up, UART_RX);
        serial_outp(up, UART_FCR, old_fcr);
        serial_outp(up, UART_MCR, old_mcr);
        serial_outp(up, UART_LCR, UART_LCR_DLAB);
        serial_dl_write(up, old_dl);
        serial_outp(up, UART_LCR, old_lcr);

        return count;
}

/*
 * Read UART ID using the divisor method - set DLL and DLM to zero
 * and the revision will be in DLL and device type in DLM.  We
 * preserve the device state across this.
 */
static unsigned int autoconfig_read_divisor_id(struct uart_8250_port *p)
{
        unsigned char old_dll, old_dlm, old_lcr;
        unsigned int id;

        old_lcr = serial_inp(p, UART_LCR);
        serial_outp(p, UART_LCR, UART_LCR_DLAB);

        old_dll = serial_inp(p, UART_DLL);
        old_dlm = serial_inp(p, UART_DLM);

        serial_outp(p, UART_DLL, 0);
        serial_outp(p, UART_DLM, 0);

        id = serial_inp(p, UART_DLL) | serial_inp(p, UART_DLM) << 8;

        serial_outp(p, UART_DLL, old_dll);
        serial_outp(p, UART_DLM, old_dlm);
        serial_outp(p, UART_LCR, old_lcr);

        return id;
}

/*
 * This is a helper routine to autodetect StarTech/Exar/Oxsemi UART's.
 * When this function is called we know it is at least a StarTech
 * 16650 V2, but it might be one of several StarTech UARTs, or one of
 * its clones.  (We treat the broken original StarTech 16650 V1 as a
 * 16550, and why not?  Startech doesn't seem to even acknowledge its
 * existence.)
 *
 * What evil have men's minds wrought...
 */
static void autoconfig_has_efr(struct uart_8250_port *up)
{
        unsigned int id1, id2, id3, rev;

        /*
         * Everything with an EFR has SLEEP
         */
        up->capabilities |= UART_CAP_EFR | UART_CAP_SLEEP;

        /*
         * First we check to see if it's an Oxford Semiconductor UART.
         *
         * If we have to do this here because some non-National
         * Semiconductor clone chips lock up if you try writing to the
         * LSR register (which serial_icr_read does)
         */

        /*
         * Check for Oxford Semiconductor 16C950.
         *
         * EFR [4] must be set else this test fails.
         *
         * This shouldn't be necessary, but Mike Hudson (Exoray@isys.ca)
         * claims that it's needed for 952 dual UART's (which are not
         * recommended for new designs).
         */
        up->acr = 0;
        serial_out(up, UART_LCR, 0xBF);
        serial_out(up, UART_EFR, UART_EFR_ECB);
        serial_out(up, UART_LCR, 0x00);
        id1 = serial_icr_read(up, UART_ID1);
        id2 = serial_icr_read(up, UART_ID2);
        id3 = serial_icr_read(up, UART_ID3);
        rev = serial_icr_read(up, UART_REV);

        DEBUG_AUTOCONF("950id=%02x:%02x:%02x:%02x ", id1, id2, id3, rev);

        if (id1 == 0x16 && id2 == 0xC9 &&
            (id3 == 0x50 || id3 == 0x52 || id3 == 0x54)) {
                up->port.type = PORT_16C950;

                /*
                 * Enable work around for the Oxford Semiconductor 952 rev B
                 * chip which causes it to seriously miscalculate baud rates
                 * when DLL is 0.
                 */
                if (id3 == 0x52 && rev == 0x01)
                        up->bugs |= UART_BUG_QUOT;
                return;
        }

        /*
         * We check for a XR16C850 by setting DLL and DLM to 0, and then
         * reading back DLL and DLM.  The chip type depends on the DLM
         * value read back:
         *  0x10 - XR16C850 and the DLL contains the chip revision.
         *  0x12 - XR16C2850.
         *  0x14 - XR16C854.
         */
        id1 = autoconfig_read_divisor_id(up);
        DEBUG_AUTOCONF("850id=%04x ", id1);

        id2 = id1 >> 8;
        if (id2 == 0x10 || id2 == 0x12 || id2 == 0x14) {
                up->port.type = PORT_16850;
                return;
        }

        /*
         * It wasn't an XR16C850.
         *
         * We distinguish between the '654 and the '650 by counting
         * how many bytes are in the FIFO.  I'm using this for now,
         * since that's the technique that was sent to me in the
         * serial driver update, but I'm not convinced this works.
         * I've had problems doing this in the past.  -TYT
         */
        if (size_fifo(up) == 64)
                up->port.type = PORT_16654;
        else
                up->port.type = PORT_16650V2;
}

/*
 * We detected a chip without a FIFO.  Only two fall into
 * this category - the original 8250 and the 16450.  The
 * 16450 has a scratch register (accessible with LCR=0)
 */
static void autoconfig_8250(struct uart_8250_port *up)
{
        unsigned char scratch, status1, status2;

        up->port.type = PORT_8250;

        scratch = serial_in(up, UART_SCR);
        serial_outp(up, UART_SCR, 0xa5);
        status1 = serial_in(up, UART_SCR);
        serial_outp(up, UART_SCR, 0x5a);
        status2 = serial_in(up, UART_SCR);
        serial_outp(up, UART_SCR, scratch);

        if (status1 == 0xa5 && status2 == 0x5a)
                up->port.type = PORT_16450;
}

static int broken_efr(struct uart_8250_port *up)
{
        /*
         * Exar ST16C2550 "A2" devices incorrectly detect as
         * having an EFR, and report an ID of 0x0201.  See
         * http://www.exar.com/info.php?pdf=dan180_oct2004.pdf
         */
        if (autoconfig_read_divisor_id(up) == 0x0201 && size_fifo(up) == 16)
                return 1;

        return 0;
}

/*
 * We know that the chip has FIFOs.  Does it have an EFR?  The
 * EFR is located in the same register position as the IIR and
 * we know the top two bits of the IIR are currently set.  The
 * EFR should contain zero.  Try to read the EFR.
 */
static void autoconfig_16550a(struct uart_8250_port *up)
{
        unsigned char status1, status2;
        unsigned int iersave;

        up->port.type = PORT_16550A;
        up->capabilities |= UART_CAP_FIFO;

        /*
         * Check for presence of the EFR when DLAB is set.
         * Only ST16C650V1 UARTs pass this test.
         */
        serial_outp(up, UART_LCR, UART_LCR_DLAB);
        if (serial_in(up, UART_EFR) == 0) {
                serial_outp(up, UART_EFR, 0xA8);
                if (serial_in(up, UART_EFR) != 0) {
                        DEBUG_AUTOCONF("EFRv1 ");
                        up->port.type = PORT_16650;
                        up->capabilities |= UART_CAP_EFR | UART_CAP_SLEEP;
                } else {
                        DEBUG_AUTOCONF("Motorola 8xxx DUART ");
                }
                serial_outp(up, UART_EFR, 0);
                return;
        }

        /*
         * Maybe it requires 0xbf to be written to the LCR.
         * (other ST16C650V2 UARTs, TI16C752A, etc)
         */
        serial_outp(up, UART_LCR, 0xBF);
        if (serial_in(up, UART_EFR) == 0 && !broken_efr(up)) {
                DEBUG_AUTOCONF("EFRv2 ");
                autoconfig_has_efr(up);
                return;
        }

        /*
         * Check for a National Semiconductor SuperIO chip.
         * Attempt to switch to bank 2, read the value of the LOOP bit
         * from EXCR1. Switch back to bank 0, change it in MCR. Then
         * switch back to bank 2, read it from EXCR1 again and check
         * it's changed. If so, set baud_base in EXCR2 to 921600. -- dwmw2
         */
        serial_outp(up, UART_LCR, 0);
        status1 = serial_in(up, UART_MCR);
        serial_outp(up, UART_LCR, 0xE0);
        status2 = serial_in(up, 0x02); /* EXCR1 */

        if (!((status2 ^ status1) & UART_MCR_LOOP)) {
                serial_outp(up, UART_LCR, 0);
                serial_outp(up, UART_MCR, status1 ^ UART_MCR_LOOP);
                serial_outp(up, UART_LCR, 0xE0);
                status2 = serial_in(up, 0x02); /* EXCR1 */
                serial_outp(up, UART_LCR, 0);
                serial_outp(up, UART_MCR, status1);

                if ((status2 ^ status1) & UART_MCR_LOOP) {
                        unsigned short quot;

                        serial_outp(up, UART_LCR, 0xE0);

                        quot = serial_dl_read(up);
                        quot <<= 3;

                        status1 = serial_in(up, 0x04); /* EXCR2 */
                        status1 &= ~0xB0; /* Disable LOCK, mask out PRESL[01] */
                        status1 |= 0x10;  /* 1.625 divisor for baud_base --> 921600 */
                        serial_outp(up, 0x04, status1);

                        serial_dl_write(up, quot);

                        serial_outp(up, UART_LCR, 0);

                        up->port.uartclk = 921600*16;
                        up->port.type = PORT_NS16550A;
                        up->capabilities |= UART_NATSEMI;
                        return;
                }
        }

        /*
         * No EFR.  Try to detect a TI16750, which only sets bit 5 of
         * the IIR when 64 byte FIFO mode is enabled when DLAB is set.
         * Try setting it with and without DLAB set.  Cheap clones
         * set bit 5 without DLAB set.
         */
        serial_outp(up, UART_LCR, 0);
        serial_outp(up, UART_FCR, UART_FCR_ENABLE_FIFO | UART_FCR7_64BYTE);
        status1 = serial_in(up, UART_IIR) >> 5;
        serial_outp(up, UART_FCR, UART_FCR_ENABLE_FIFO);
        serial_outp(up, UART_LCR, UART_LCR_DLAB);
        serial_outp(up, UART_FCR, UART_FCR_ENABLE_FIFO | UART_FCR7_64BYTE);
        status2 = serial_in(up, UART_IIR) >> 5;
        serial_outp(up, UART_FCR, UART_FCR_ENABLE_FIFO);
        serial_outp(up, UART_LCR, 0);

        DEBUG_AUTOCONF("iir1=%d iir2=%d ", status1, status2);

        if (status1 == 6 && status2 == 7) {
                up->port.type = PORT_16750;
                up->capabilities |= UART_CAP_AFE | UART_CAP_SLEEP;
                return;
        }

        /*
         * Try writing and reading the UART_IER_UUE bit (b6).
         * If it works, this is probably one of the Xscale platform's
         * internal UARTs.
         * We're going to explicitly set the UUE bit to 0 before
         * trying to write and read a 1 just to make sure it's not
         * already a 1 and maybe locked there before we even start start.
         */
        iersave = serial_in(up, UART_IER);
        serial_outp(up, UART_IER, iersave & ~UART_IER_UUE);
        if (!(serial_in(up, UART_IER) & UART_IER_UUE)) {
                /*
                 * OK it's in a known zero state, try writing and reading
                 * without disturbing the current state of the other bits.
                 */
                serial_outp(up, UART_IER, iersave | UART_IER_UUE);
                if (serial_in(up, UART_IER) & UART_IER_UUE) {
                        /*
                         * It's an Xscale.
                         * We'll leave the UART_IER_UUE bit set to 1 (enabled).
                         */
                        DEBUG_AUTOCONF("Xscale ");
                        up->port.type = PORT_XSCALE;
                        up->capabilities |= UART_CAP_UUE;
                        return;
                }
        } else {
                /*
                 * If we got here we couldn't force the IER_UUE bit to 0.
                 * Log it and continue.
                 */
                DEBUG_AUTOCONF("Couldn't force IER_UUE to 0 ");
        }
        serial_outp(up, UART_IER, iersave);
}

/*
 * This routine is called by rs_init() to initialize a specific serial
 * port.  It determines what type of UART chip this serial port is
 * using: 8250, 16450, 16550, 16550A.  The important question is
 * whether or not this UART is a 16550A or not, since this will
 * determine whether or not we can use its FIFO features or not.
 */

static void autoconfig(struct uart_8250_port *up, unsigned int probeflags)
{
        unsigned char status1, scratch, scratch2, scratch3;
        unsigned char save_lcr, save_mcr;
        unsigned long flags;

        if (!up->port.iobase && !up->port.mapbase && !up->port.membase)
                return;

        DEBUG_AUTOCONF("ttyS%d: autoconf (0x%04x, 0x%p): ",
                       serial_index(&up->port), up->port.iobase, up->port.membase);

        /*
         * We really do need global IRQs disabled here - we're going to
         * be frobbing the chips IRQ enable register to see if it exists.
         */
        spin_lock_irqsave(&up->port.lock, flags);

        up->capabilities = 0;
        up->bugs = 0;

        if (!(up->port.flags & UPF_BUGGY_UART)) {
                /*
                 * Do a simple existence test first; if we fail this,
                 * there's no point trying anything else.
                 *
                 * 0x80 is used as a nonsense port to prevent against
                 * false positives due to ISA bus float.  The
                 * assumption is that 0x80 is a non-existent port;
                 * which should be safe since include/asm/io.h also
                 * makes this assumption.
                 *
                 * Note: this is safe as long as MCR bit 4 is clear
                 * and the device is in "PC" mode.
                 */
                scratch = serial_inp(up, UART_IER);
                serial_outp(up, UART_IER, 0);
#ifdef __i386__
                outb(0xff, 0x080);
#endif
                /*
                 * Mask out IER[7:4] bits for test as some UARTs (e.g. TL
                 * 16C754B) allow only to modify them if an EFR bit is set.
                 */
                scratch2 = serial_inp(up, UART_IER) & 0x0f;
                serial_outp(up, UART_IER, 0x0F);
#ifdef __i386__
                outb(0, 0x080);
#endif
                scratch3 = serial_inp(up, UART_IER) & 0x0f;
                serial_outp(up, UART_IER, scratch);
                if (scratch2 != 0 || scratch3 != 0x0F) {
                        /*
                         * We failed; there's nothing here
                         */
                        DEBUG_AUTOCONF("IER test failed (%02x, %02x) ",
                                       scratch2, scratch3);
                        goto out;
                }
        }

        save_mcr = serial_in(up, UART_MCR);
        save_lcr = serial_in(up, UART_LCR);

        /*
         * Check to see if a UART is really there.  Certain broken
         * internal modems based on the Rockwell chipset fail this
         * test, because they apparently don't implement the loopback
         * test mode.  So this test is skipped on the COM 1 through
         * COM 4 ports.  This *should* be safe, since no board
         * manufacturer would be stupid enough to design a board
         * that conflicts with COM 1-4 --- we hope!
         */
        if (!(up->port.flags & UPF_SKIP_TEST)) {
                serial_outp(up, UART_MCR, UART_MCR_LOOP | 0x0A);
                status1 = serial_inp(up, UART_MSR) & 0xF0;
                serial_outp(up, UART_MCR, save_mcr);
                if (status1 != 0x90) {
                        DEBUG_AUTOCONF("LOOP test failed (%02x) ",
                                       status1);
                        goto out;
                }
        }

        /*
         * We're pretty sure there's a port here.  Lets find out what
         * type of port it is.  The IIR top two bits allows us to find
         * out if it's 8250 or 16450, 16550, 16550A or later.  This
         * determines what we test for next.
         *
         * We also initialise the EFR (if any) to zero for later.  The
         * EFR occupies the same register location as the FCR and IIR.
         */
        serial_outp(up, UART_LCR, 0xBF);
        serial_outp(up, UART_EFR, 0);
        serial_outp(up, UART_LCR, 0);

        serial_outp(up, UART_FCR, UART_FCR_ENABLE_FIFO);
        scratch = serial_in(up, UART_IIR) >> 6;

        DEBUG_AUTOCONF("iir=%d ", scratch);

        switch (scratch) {
        case 0:
                autoconfig_8250(up);
                break;
        case 1:
                up->port.type = PORT_UNKNOWN;
                break;
        case 2:
                up->port.type = PORT_16550;
                break;
        case 3:
                autoconfig_16550a(up);
                break;
        }

#ifdef CONFIG_SERIAL_8250_RSA
        /*
         * Only probe for RSA ports if we got the region.
         */
        if (up->port.type == PORT_16550A && probeflags & PROBE_RSA) {
                int i;

                for (i = 0 ; i < probe_rsa_count; ++i) {
                        if (probe_rsa[i] == up->port.iobase &&
                            __enable_rsa(up)) {
                                up->port.type = PORT_RSA;
                                break;
                        }
                }
        }
#endif

#ifdef CONFIG_SERIAL_8250_AU1X00
        /* if access method is AU, it is a 16550 with a quirk */
        if (up->port.type == PORT_16550A && up->port.iotype == UPIO_AU)
                up->bugs |= UART_BUG_NOMSR;
#endif

        serial_outp(up, UART_LCR, save_lcr);

        if (up->capabilities != uart_config[up->port.type].flags) {
                printk(KERN_WARNING
                       "ttyS%d: detected caps %08x should be %08x\n",
                       serial_index(&up->port), up->capabilities,
                       uart_config[up->port.type].flags);
        }

        up->port.fifosize = uart_config[up->port.type].fifo_size;
        up->capabilities = uart_config[up->port.type].flags;
        up->tx_loadsz = uart_config[up->port.type].tx_loadsz;

        if (up->port.type == PORT_UNKNOWN)
                goto out;

        /*
         * Reset the UART.
         */
#ifdef CONFIG_SERIAL_8250_RSA
        if (up->port.type == PORT_RSA)
                serial_outp(up, UART_RSA_FRR, 0);
#endif
        serial_outp(up, UART_MCR, save_mcr);
        serial8250_clear_fifos(up);
        serial_in(up, UART_RX);
        if (up->capabilities & UART_CAP_UUE)
                serial_outp(up, UART_IER, UART_IER_UUE);
        else
                serial_outp(up, UART_IER, 0);

 out:
        spin_unlock_irqrestore(&up->port.lock, flags);
        DEBUG_AUTOCONF("type=%s\n", uart_config[up->port.type].name);
}

static void autoconfig_irq(struct uart_8250_port *up)
{
        unsigned char save_mcr, save_ier;
        unsigned char save_ICP = 0;
        unsigned int ICP = 0;
        unsigned long irqs;
        int irq;

        if (up->port.flags & UPF_FOURPORT) {
                ICP = (up->port.iobase & 0xfe0) | 0x1f;
                save_ICP = inb_p(ICP);
                outb_p(0x80, ICP);
                (void) inb_p(ICP);
        }

        /* forget possible initially masked and pending IRQ */
        probe_irq_off(probe_irq_on());
        save_mcr = serial_inp(up, UART_MCR);
        save_ier = serial_inp(up, UART_IER);
        serial_outp(up, UART_MCR, UART_MCR_OUT1 | UART_MCR_OUT2);

        irqs = probe_irq_on();
        serial_outp(up, UART_MCR, 0);
        udelay(10);
        if (up->port.flags & UPF_FOURPORT) {
                serial_outp(up, UART_MCR,
                            UART_MCR_DTR | UART_MCR_RTS);
        } else {
                serial_outp(up, UART_MCR,
                            UART_MCR_DTR | UART_MCR_RTS | UART_MCR_OUT2);
        }
        serial_outp(up, UART_IER, 0x0f);        /* enable all intrs */
        (void)serial_inp(up, UART_LSR);
        (void)serial_inp(up, UART_RX);
        (void)serial_inp(up, UART_IIR);
        (void)serial_inp(up, UART_MSR);
        serial_outp(up, UART_TX, 0xFF);
        udelay(20);
        irq = probe_irq_off(irqs);

        serial_outp(up, UART_MCR, save_mcr);
        serial_outp(up, UART_IER, save_ier);

        if (up->port.flags & UPF_FOURPORT)
                outb_p(save_ICP, ICP);

        up->port.irq = (irq > 0) ? irq : 0;
}

static inline void __stop_tx(struct uart_8250_port *p)
{
        if (p->ier & UART_IER_THRI) {
                p->ier &= ~UART_IER_THRI;
                serial_out(p, UART_IER, p->ier);
        }
}

static void serial8250_stop_tx(struct uart_port *port)
{
        struct uart_8250_port *up = (struct uart_8250_port *)port;

        __stop_tx(up);

        /*
         * We really want to stop the transmitter from sending.
         */
        if (up->port.type == PORT_16C950) {
                up->acr |= UART_ACR_TXDIS;
                serial_icr_write(up, UART_ACR, up->acr);
        }
}

static void transmit_chars(struct uart_8250_port *up);

static void serial8250_start_tx(struct uart_port *port)
{
        struct uart_8250_port *up = (struct uart_8250_port *)port;

        if (!(up->ier & UART_IER_THRI)) {
                up->ier |= UART_IER_THRI;
                serial_out(up, UART_IER, up->ier);

                if (up->bugs & UART_BUG_TXEN) {
                        unsigned char lsr, iir;
                        lsr = serial_in(up, UART_LSR);
                        up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;
                        iir = serial_in(up, UART_IIR) & 0x0f;
                        if ((up->port.type == PORT_RM9000) ?
                                (lsr & UART_LSR_THRE &&
                                (iir == UART_IIR_NO_INT || iir == UART_IIR_THRI)) :
                                (lsr & UART_LSR_TEMT && iir & UART_IIR_NO_INT))
                                transmit_chars(up);
                }
        }

        /*
         * Re-enable the transmitter if we disabled it.
         */
        if (up->port.type == PORT_16C950 && up->acr & UART_ACR_TXDIS) {
                up->acr &= ~UART_ACR_TXDIS;
                serial_icr_write(up, UART_ACR, up->acr);
        }
}

static void serial8250_stop_rx(struct uart_port *port)
{
        struct uart_8250_port *up = (struct uart_8250_port *)port;

        up->ier &= ~UART_IER_RLSI;
        up->port.read_status_mask &= ~UART_LSR_DR;
        serial_out(up, UART_IER, up->ier);
}

static void serial8250_enable_ms(struct uart_port *port)
{
        struct uart_8250_port *up = (struct uart_8250_port *)port;

        /* no MSR capabilities */
        if (up->bugs & UART_BUG_NOMSR)
                return;

        up->ier |= UART_IER_MSI;
        serial_out(up, UART_IER, up->ier);
}

static void
receive_chars(struct uart_8250_port *up, unsigned int *status)
{
        struct tty_struct *tty = up->port.info->port.tty;
        unsigned char ch, lsr = *status;
        int max_count = 256;
        char flag;

        do {
                if (likely(lsr & UART_LSR_DR))
                        ch = serial_inp(up, UART_RX);
                else
                        /*
                         * Intel 82571 has a Serial Over Lan device that will
                         * set UART_LSR_BI without setting UART_LSR_DR when
                         * it receives a break. To avoid reading from the
                         * receive buffer without UART_LSR_DR bit set, we
                         * just force the read character to be 0
                         */
                        ch = 0;

                flag = TTY_NORMAL;
                up->port.icount.rx++;

                lsr |= up->lsr_saved_flags;
                up->lsr_saved_flags = 0;

                if (unlikely(lsr & UART_LSR_BRK_ERROR_BITS)) {
                        /*
                         * For statistics only
                         */
                        if (lsr & UART_LSR_BI) {
                                lsr &= ~(UART_LSR_FE | UART_LSR_PE);
                                up->port.icount.brk++;
                                /*
                                 * We do the SysRQ and SAK checking
                                 * here because otherwise the break
                                 * may get masked by ignore_status_mask
                                 * or read_status_mask.
                                 */
                                if (uart_handle_break(&up->port))
                                        goto ignore_char;
                        } else if (lsr & UART_LSR_PE)
                                up->port.icount.parity++;
                        else if (lsr & UART_LSR_FE)
                                up->port.icount.frame++;
                        if (lsr & UART_LSR_OE)
                                up->port.icount.overrun++;

                        /*
                         * Mask off conditions which should be ignored.
                         */
                        lsr &= up->port.read_status_mask;

                        if (lsr & UART_LSR_BI) {
                                DEBUG_INTR("handling break....");
                                flag = TTY_BREAK;
                        } else if (lsr & UART_LSR_PE)
                                flag = TTY_PARITY;
                        else if (lsr & UART_LSR_FE)
                                flag = TTY_FRAME;
                }
                if (uart_handle_sysrq_char(&up->port, ch))
                        goto ignore_char;

                uart_insert_char(&up->port, lsr, UART_LSR_OE, ch, flag);

ignore_char:
                lsr = serial_inp(up, UART_LSR);
        } while ((lsr & (UART_LSR_DR | UART_LSR_BI)) && (max_count-- > 0));
        spin_unlock(&up->port.lock);
        tty_flip_buffer_push(tty);
        spin_lock(&up->port.lock);
        *status = lsr;
}

static void transmit_chars(struct uart_8250_port *up)
{
        struct circ_buf *xmit = &up->port.info->xmit;
        int count;

        if (up->port.x_char) {
                serial_outp(up, UART_TX, up->port.x_char);
                up->port.icount.tx++;
                up->port.x_char = 0;
                return;
        }
        if (uart_tx_stopped(&up->port)) {
                serial8250_stop_tx(&up->port);
                return;
        }
        if (uart_circ_empty(xmit)) {
                __stop_tx(up);
                return;
        }

        count = up->tx_loadsz;
        do {
                serial_out(up, UART_TX, xmit->buf[xmit->tail]);
                xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
                up->port.icount.tx++;
                if (uart_circ_empty(xmit))
                        break;
        } while (--count > 0);

        if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
                uart_write_wakeup(&up->port);

        DEBUG_INTR("THRE...");

        if (uart_circ_empty(xmit))
                __stop_tx(up);
}

static unsigned int check_modem_status(struct uart_8250_port *up)
{
        unsigned int status = serial_in(up, UART_MSR);

        status |= up->msr_saved_flags;
        up->msr_saved_flags = 0;
        if (status & UART_MSR_ANY_DELTA && up->ier & UART_IER_MSI &&
            up->port.info != NULL) {
                if (status & UART_MSR_TERI)
                        up->port.icount.rng++;
                if (status & UART_MSR_DDSR)
                        up->port.icount.dsr++;
                if (status & UART_MSR_DDCD)
                        uart_handle_dcd_change(&up->port, status & UART_MSR_DCD);
                if (status & UART_MSR_DCTS)
                        uart_handle_cts_change(&up->port, status & UART_MSR_CTS);

                wake_up_interruptible(&up->port.info->delta_msr_wait);
        }

        return status;
}

/*
 * This handles the interrupt from one port.
 */
static void serial8250_handle_port(struct uart_8250_port *up)
{
        unsigned int status;
        unsigned long flags;

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

        status = serial_inp(up, UART_LSR);

        DEBUG_INTR("status = %x...", status);

        if (status & (UART_LSR_DR | UART_LSR_BI))
                receive_chars(up, &status);
        check_modem_status(up);
        if (status & UART_LSR_THRE)
                transmit_chars(up);

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

/*
 * 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;

        DEBUG_INTR("serial8250_interrupt(%d)...", irq);

        spin_lock(&i->lock);

        l = i->head;
        do {
                struct uart_8250_port *up;
                unsigned int iir;

                up = list_entry(l, struct uart_8250_port, list);

                iir = serial_in(up, UART_IIR);
                if (!(iir & UART_IIR_NO_INT)) {
                        serial8250_handle_port(up);

                        handled = 1;

                        end = NULL;
                } else if (up->port.iotype == UPIO_DWAPB &&
                          (iir & UART_IIR_BUSY) == UART_IIR_BUSY) {
                        /* The DesignWare APB UART has an Busy Detect (0x07)
                         * interrupt meaning an LCR write attempt occured while the
                         * UART was busy. The interrupt must be cleared by reading
                         * the UART status register (USR) and the LCR re-written. */
                        unsigned int status;
                        status = *(volatile u32 *)up->port.private_data;
                        serial_out(up, UART_LCR, up->lcr);

                        handled = 1;

                        end = NULL;
                } else if (end == NULL)
                        end = l;

                l = l->next;

                if (l == i->head && pass_counter++ > PASS_LIMIT) {
                        /* If we hit this, we're dead. */
                        printk(KERN_ERR "serial8250: too much work for "
                                "irq%d\n", irq);
                        break;
                }
        } while (l != end);

        spin_unlock(&i->lock);

        DEBUG_INTR("end.\n");

        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, irq_flags = up->port.flags & UPF_SHARE_IRQ ? IRQF_SHARED : 0;

        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,
                                  irq_flags, "serial", 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_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);
}

/* Base timer interval for polling */
static inline int poll_timeout(int timeout)
{
        return timeout > 6 ? (timeout / 2 - 2) : 1;
}

/*
 * 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(unsigned long data)
{
        struct uart_8250_port *up = (struct uart_8250_port *)data;
        unsigned int iir;

        iir = serial_in(up, UART_IIR);
        if (!(iir & UART_IIR_NO_INT))
                serial8250_handle_port(up);
        mod_timer(&up->timer, jiffies + poll_timeout(up->port.timeout));
}

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

        /*
         * Must disable interrupts or else we risk racing with the interrupt
         * based handler.
         */
        if (is_real_interrupt(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.
         */
        spin_lock_irqsave(&up->port.lock, flags);
        lsr = serial_in(up, UART_LSR);
        up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;
        spin_unlock_irqrestore(&up->port.lock, flags);
        if ((iir & UART_IIR_NO_INT) && (up->ier & UART_IER_THRI) &&
            (!uart_circ_empty(&up->port.info->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_handle_port(up);

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

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

static unsigned int serial8250_tx_empty(struct uart_port *port)
{
        struct uart_8250_port *up = (struct uart_8250_port *)port;
        unsigned long flags;
        unsigned int lsr;

        spin_lock_irqsave(&up->port.lock, flags);
        lsr = serial_in(up, UART_LSR);
        up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;
        spin_unlock_irqrestore(&up->port.lock, flags);

        return lsr & UART_LSR_TEMT ? TIOCSER_TEMT : 0;
}

static unsigned int serial8250_get_mctrl(struct uart_port *port)
{
        struct uart_8250_port *up = (struct uart_8250_port *)port;
        unsigned int status;
        unsigned int ret;

        status = check_modem_status(up);

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

static void serial8250_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
        struct uart_8250_port *up = (struct uart_8250_port *)port;
        unsigned char mcr = 0;

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

        mcr = (mcr & up->mcr_mask) | up->mcr_force | up->mcr;

        serial_out(up, UART_MCR, mcr);
}

static void serial8250_break_ctl(struct uart_port *port, int break_state)
{
        struct uart_8250_port *up = (struct uart_8250_port *)port;
        unsigned long flags;

        spin_lock_irqsave(&up->port.lock, flags);
        if (break_state == -1)
                up->lcr |= UART_LCR_SBC;
        else
                up->lcr &= ~UART_LCR_SBC;
        serial_out(up, UART_LCR, up->lcr);
        spin_unlock_irqrestore(&up->port.lock, flags);
}

#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)

/*
 *      Wait for transmitter & holding register to empty
 */
static void wait_for_xmitr(struct uart_8250_port *up, int bits)
{
        unsigned int status, tmout = 10000;

        /* Wait up to 10ms for the character(s) to be sent. */
        do {
                status = serial_in(up, UART_LSR);

                up->lsr_saved_flags |= status & LSR_SAVE_FLAGS;

                if (--tmout == 0)
                        break;
                udelay(1);
        } while ((status & bits) != bits);

        /* Wait up to 1s for flow control if necessary */
        if (up->port.flags & UPF_CONS_FLOW) {
                unsigned int tmout;
                for (tmout = 1000000; tmout; tmout--) {
                        unsigned int msr = serial_in(up, UART_MSR);
                        up->msr_saved_flags |= msr & MSR_SAVE_FLAGS;
                        if (msr & UART_MSR_CTS)
                                break;
                        udelay(1);
                        touch_nmi_watchdog();
                }
        }
}

#ifdef CONFIG_CONSOLE_POLL
/*
 * Console polling routines for writing and reading from the uart while
 * in an interrupt or debug context.
 */

static int serial8250_get_poll_char(struct uart_port *port)
{
        struct uart_8250_port *up = (struct uart_8250_port *)port;
        unsigned char lsr = serial_inp(up, UART_LSR);

        while (!(lsr & UART_LSR_DR))
                lsr = serial_inp(up, UART_LSR);

        return serial_inp(up, UART_RX);
}


static void serial8250_put_poll_char(struct uart_port *port,
                         unsigned char c)
{
        unsigned int ier;
        struct uart_8250_port *up = (struct uart_8250_port *)port;

        /*
         *      First save the IER then disable the interrupts
         */
        ier = serial_in(up, UART_IER);
        if (up->capabilities & UART_CAP_UUE)
                serial_out(up, UART_IER, UART_IER_UUE);
        else
                serial_out(up, UART_IER, 0);

        wait_for_xmitr(up, BOTH_EMPTY);
        /*
         *      Send the character out.
         *      If a LF, also do CR...
         */
        serial_out(up, UART_TX, c);
        if (c == 10) {
                wait_for_xmitr(up, BOTH_EMPTY);
                serial_out(up, UART_TX, 13);
        }

        /*
         *      Finally, wait for transmitter to become empty
         *      and restore the IER
         */
        wait_for_xmitr(up, BOTH_EMPTY);
        serial_out(up, UART_IER, ier);
}

#endif /* CONFIG_CONSOLE_POLL */

static int serial8250_startup(struct uart_port *port)
{
        struct uart_8250_port *up = (struct uart_8250_port *)port;
        unsigned long flags;
        unsigned char lsr, iir;
        int retval;

        up->capabilities = uart_config[up->port.type].flags;
        up->mcr = 0;

        if (up->port.type == PORT_16C950) {
                /* Wake up and initialize UART */
                up->acr = 0;
                serial_outp(up, UART_LCR, 0xBF);
                serial_outp(up, UART_EFR, UART_EFR_ECB);
                serial_outp(up, UART_IER, 0);
                serial_outp(up, UART_LCR, 0);
                serial_icr_write(up, UART_CSR, 0); /* Reset the UART */
                serial_outp(up, UART_LCR, 0xBF);
                serial_outp(up, UART_EFR, UART_EFR_ECB);
                serial_outp(up, UART_LCR, 0);
        }

#ifdef CONFIG_SERIAL_8250_RSA
        /*
         * If this is an RSA port, see if we can kick it up to the
         * higher speed clock.
         */
        enable_rsa(up);
#endif

        /*
         * Clear the FIFO buffers and disable them.
         * (they will be reenabled in set_termios())
         */
        serial8250_clear_fifos(up);

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

        /*
         * At this point, there's no way the LSR could still be 0xff;
         * if it is, then bail out, because there's likely no UART
         * here.
         */
        if (!(up->port.flags & UPF_BUGGY_UART) &&
            (serial_inp(up, UART_LSR) == 0xff)) {
                printk(KERN_INFO "ttyS%d: LSR safety check engaged!\n",
                       serial_index(&up->port));
                return -ENODEV;
        }

        /*
         * For a XR16C850, we need to set the trigger levels
         */
        if (up->port.type == PORT_16850) {
                unsigned char fctr;

                serial_outp(up, UART_LCR, 0xbf);

                fctr = serial_inp(up, UART_FCTR) & ~(UART_FCTR_RX|UART_FCTR_TX);
                serial_outp(up, UART_FCTR, fctr | UART_FCTR_TRGD | UART_FCTR_RX);
                serial_outp(up, UART_TRG, UART_TRG_96);
                serial_outp(up, UART_FCTR, fctr | UART_FCTR_TRGD | UART_FCTR_TX);
                serial_outp(up, UART_TRG, UART_TRG_96);

                serial_outp(up, UART_LCR, 0);
        }

        if (is_real_interrupt(up->port.irq)) {
                unsigned char iir1;
                /*
                 * Test for UARTs that do not reassert THRE when the
                 * transmitter is idle and the interrupt has already
                 * been cleared.  Real 16550s should always reassert
                 * this interrupt whenever the transmitter is idle and
                 * the interrupt is enabled.  Delays are necessary to
                 * allow register changes to become visible.
                 */
                spin_lock_irqsave(&up->port.lock, flags);
                if (up->port.flags & UPF_SHARE_IRQ)
                        disable_irq_nosync(up->port.irq);

                wait_for_xmitr(up, UART_LSR_THRE);
                serial_out_sync(up, UART_IER, UART_IER_THRI);
                udelay(1); /* allow THRE to set */
                iir1 = serial_in(up, UART_IIR);
                serial_out(up, UART_IER, 0);
                serial_out_sync(up, UART_IER, UART_IER_THRI);
                udelay(1); /* allow a working UART time to re-assert THRE */
                iir = serial_in(up, UART_IIR);
                serial_out(up, UART_IER, 0);

                if (up->port.flags & UPF_SHARE_IRQ)
                        enable_irq(up->port.irq);
                spin_unlock_irqrestore(&up->port.lock, flags);

                /*
                 * If the interrupt is not reasserted, setup a timer to
                 * kick the UART on a regular basis.
                 */
                if (!(iir1 & UART_IIR_NO_INT) && (iir & UART_IIR_NO_INT)) {
                        up->bugs |= UART_BUG_THRE;
                        pr_debug("ttyS%d - using backup timer\n",
                                 serial_index(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) {
                up->timer.function = serial8250_backup_timeout;
                up->timer.data = (unsigned long)up;
                mod_timer(&up->timer, jiffies +
                          poll_timeout(up->port.timeout) + 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 (!is_real_interrupt(up->port.irq)) {
                up->timer.data = (unsigned long)up;
                mod_timer(&up->timer, jiffies + poll_timeout(up->port.timeout));
        } else {
                retval = serial_link_irq_chain(up);
                if (retval)
                        return retval;
        }

        /*
         * Now, initialize the UART

         */
        serial_outp(up, UART_LCR, UART_LCR_WLEN8);

        spin_lock_irqsave(&up->port.lock, flags);
        if (up->port.flags & UPF_FOURPORT) {
                if (!is_real_interrupt(up->port.irq))
                        up->port.mctrl |= TIOCM_OUT1;
        } else
                /*
                 * Most PC uarts need OUT2 raised to enable interrupts.
                 */
                if (is_real_interrupt(up->port.irq))
                        up->port.mctrl |= TIOCM_OUT2;

        serial8250_set_mctrl(&up->port, up->port.mctrl);

        /*
         * Do a quick test to see if we receive an
         * interrupt when we enable the TX irq.
         */
        serial_outp(up, UART_IER, UART_IER_THRI);
        lsr = serial_in(up, UART_LSR);
        iir = serial_in(up, UART_IIR);
        serial_outp(up, UART_IER, 0);

        if (lsr & UART_LSR_TEMT && iir & UART_IIR_NO_INT) {
                if (!(up->bugs & UART_BUG_TXEN)) {
                        up->bugs |= UART_BUG_TXEN;
                        pr_debug("ttyS%d - enabling bad tx status workarounds\n",
                                 serial_index(port));
                }
        } else {
                up->bugs &= ~UART_BUG_TXEN;
        }

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

        /*
         * Clear the interrupt registers again for luck, and clear the
         * saved flags to avoid getting false values from polling
         * routines or the previous session.
         */
        serial_inp(up, UART_LSR);
        serial_inp(up, UART_RX);
        serial_inp(up, UART_IIR);
        serial_inp(up, UART_MSR);
        up->lsr_saved_flags = 0;
        up->msr_saved_flags = 0;

        /*
         * Finally, enable interrupts.  Note: Modem status interrupts
         * are set via set_termios(), which will be occurring imminently
         * anyway, so we don't enable them here.
         */
        up->ier = UART_IER_RLSI | UART_IER_RDI;
        serial_outp(up, UART_IER, up->ier);

        if (up->port.flags & UPF_FOURPORT) {
                unsigned int icp;
                /*
                 * Enable interrupts on the AST Fourport board
                 */
                icp = (up->port.iobase & 0xfe0) | 0x01f;
                outb_p(0x80, icp);
                (void) inb_p(icp);
        }

        return 0;
}

static void serial8250_shutdown(struct uart_port *port)
{
        struct uart_8250_port *up = (struct uart_8250_port *)port;
        unsigned long flags;

        /*
         * Disable interrupts from this port
         */
        up->ier = 0;
        serial_outp(up, UART_IER, 0);

        spin_lock_irqsave(&up->port.lock, flags);
        if (up->port.flags & UPF_FOURPORT) {
                /* reset interrupts on the AST Fourport board */
                inb((up->port.iobase & 0xfe0) | 0x1f);
                up->port.mctrl |= TIOCM_OUT1;
        } else
                up->port.mctrl &= ~TIOCM_OUT2;

        serial8250_set_mctrl(&up->port, up->port.mctrl);
        spin_unlock_irqrestore(&up->port.lock, flags);

        /*
         * Disable break condition and FIFOs
         */
        serial_out(up, UART_LCR, serial_inp(up, UART_LCR) & ~UART_LCR_SBC);
        serial8250_clear_fifos(up);

#ifdef CONFIG_SERIAL_8250_RSA
        /*
         * Reset the RSA board back to 115kbps compat mode.
         */
        disable_rsa(up);
#endif

        /*
         * Read data port to reset things, and then unlink from
         * the IRQ chain.
         */
        (void) serial_in(up, UART_RX);

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

static unsigned int serial8250_get_divisor(struct uart_port *port, unsigned int baud)
{
        unsigned int quot;

        /*
         * Handle magic divisors for baud rates above baud_base on
         * SMSC SuperIO chips.
         */
        if ((port->flags & UPF_MAGIC_MULTIPLIER) &&
            baud == (port->uartclk/4))
                quot = 0x8001;
        else if ((port->flags & UPF_MAGIC_MULTIPLIER) &&
                 baud == (port->uartclk/8))
                quot = 0x8002;
        else
                quot = uart_get_divisor(port, baud);

        return quot;
}

static void
serial8250_set_termios(struct uart_port *port, struct ktermios *termios,
                       struct ktermios *old)
{
        struct uart_8250_port *up = (struct uart_8250_port *)port;
        unsigned char cval, fcr = 0;
        unsigned long flags;
        unsigned int baud, quot;

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

        if (termios->c_cflag & CSTOPB)
                cval |= UART_LCR_STOP;
        if (termios->c_cflag & PARENB)
                cval |= UART_LCR_PARITY;
        if (!(termios->c_cflag & PARODD))
                cval |= UART_LCR_EPAR;
#ifdef CMSPAR
        if (termios->c_cflag & CMSPAR)
                cval |= UART_LCR_SPAR;
#endif

        /*
         * Ask the core to calculate the divisor for us.
         */
        baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk/16);
        quot = serial8250_get_divisor(port, baud);

        /*
         * Oxford Semi 952 rev B workaround
         */
        if (up->bugs & UART_BUG_QUOT && (quot & 0xff) == 0)
                quot++;

        if (up->capabilities & UART_CAP_FIFO && up->port.fifosize > 1) {
                if (baud < 2400)
                        fcr = UART_FCR_ENABLE_FIFO | UART_FCR_TRIGGER_1;
                else
                        fcr = uart_config[up->port.type].fcr;
        }

        /*
         * MCR-based auto flow control.  When AFE is enabled, RTS will be
         * deasserted when the receive FIFO contains more characters than
         * the trigger, or the MCR RTS bit is cleared.  In the case where
         * the remote UART is not using CTS auto flow control, we must
         * have sufficient FIFO entries for the latency of the remote
         * UART to respond.  IOW, at least 32 bytes of FIFO.
         */
        if (up->capabilities & UART_CAP_AFE && up->port.fifosize >= 32) {
                up->mcr &= ~UART_MCR_AFE;
                if (termios->c_cflag & CRTSCTS)
                        up->mcr |= UART_MCR_AFE;
        }

        /*
         * Ok, we're now changing the port state.  Do it with
         * interrupts disabled.
         */
        spin_lock_irqsave(&up->port.lock, flags);

        /*
         * Update the per-port timeout.
         */
        uart_update_timeout(port, termios->c_cflag, baud);

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

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

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

        /*
         * CTS flow control flag and modem status interrupts
         */
        up->ier &= ~UART_IER_MSI;
        if (!(up->bugs & UART_BUG_NOMSR) &&
                        UART_ENABLE_MS(&up->port, termios->c_cflag))
                up->ier |= UART_IER_MSI;
        if (up->capabilities & UART_CAP_UUE)
                up->ier |= UART_IER_UUE | UART_IER_RTOIE;

        serial_out(up, UART_IER, up->ier);

        if (up->capabilities & UART_CAP_EFR) {
                unsigned char efr = 0;
                /*
                 * TI16C752/Startech hardware flow control.  FIXME:
                 * - TI16C752 requires control thresholds to be set.
                 * - UART_MCR_RTS is ineffective if auto-RTS mode is enabled.
                 */
                if (termios->c_cflag & CRTSCTS)
                        efr |= UART_EFR_CTS;

                serial_outp(up, UART_LCR, 0xBF);
                serial_outp(up, UART_EFR, efr);
        }

#ifdef CONFIG_ARCH_OMAP
        /* Workaround to enable 115200 baud on OMAP1510 internal ports */
        if (cpu_is_omap1510() && is_omap_port(up)) {
                if (baud == 115200) {
                        quot = 1;
                        serial_out(up, UART_OMAP_OSC_12M_SEL, 1);
                } else
                        serial_out(up, UART_OMAP_OSC_12M_SEL, 0);
        }
#endif

        if (up->capabilities & UART_NATSEMI) {
                /* Switch to bank 2 not bank 1, to avoid resetting EXCR2 */
                serial_outp(up, UART_LCR, 0xe0);
        } else {
                serial_outp(up, UART_LCR, cval | UART_LCR_DLAB);/* set DLAB */
        }

        serial_dl_write(up, quot);

        /*
         * LCR DLAB must be set to enable 64-byte FIFO mode. If the FCR
         * is written without DLAB set, this mode will be disabled.
         */
        if (up->port.type == PORT_16750)
                serial_outp(up, UART_FCR, fcr);

        serial_outp(up, UART_LCR, cval);                /* reset DLAB */
        up->lcr = cval;                                 /* Save LCR */
        if (up->port.type != PORT_16750) {
                if (fcr & UART_FCR_ENABLE_FIFO) {
                        /* emulated UARTs (Lucent Venus 167x) need two steps */
                        serial_outp(up, UART_FCR, UART_FCR_ENABLE_FIFO);
                }
                serial_outp(up, UART_FCR, fcr);         /* set fcr */
        }
        serial8250_set_mctrl(&up->port, up->port.mctrl);
        spin_unlock_irqrestore(&up->port.lock, flags);
        /* Don't rewrite B0 */
        if (tty_termios_baud_rate(termios))
                tty_termios_encode_baud_rate(termios, baud, baud);
}

static void
serial8250_pm(struct uart_port *port, unsigned int state,
              unsigned int oldstate)
{
        struct uart_8250_port *p = (struct uart_8250_port *)port;

        serial8250_set_sleep(p, state != 0);

        if (p->pm)
                p->pm(port, state, oldstate);
}

static unsigned int serial8250_port_size(struct uart_8250_port *pt)
{
        if (pt->port.iotype == UPIO_AU)
                return 0x100000;
#ifdef CONFIG_ARCH_OMAP
        if (is_omap_port(pt))
                return 0x16 << pt->port.regshift;
#endif
        return 8 << pt->port.regshift;
}

/*
 * Resource handling.
 */
static int serial8250_request_std_resource(struct uart_8250_port *up)
{
        unsigned int size = serial8250_port_size(up);
        int ret = 0;

        switch (up->port.iotype) {
        case UPIO_AU:
        case UPIO_TSI:
        case UPIO_MEM32:
        case UPIO_MEM:
        case UPIO_DWAPB:
                if (!up->port.mapbase)
                        break;

                if (!request_mem_region(up->port.mapbase, size, "serial")) {
                        ret = -EBUSY;
                        break;
                }

                if (up->port.flags & UPF_IOREMAP) {
                        up->port.membase = ioremap_nocache(up->port.mapbase,
                                                                        size);
                        if (!up->port.membase) {
                                release_mem_region(up->port.mapbase, size);
                                ret = -ENOMEM;
                        }
                }
                break;

        case UPIO_HUB6:
        case UPIO_PORT:
                if (!request_region(up->port.iobase, size, "serial"))
                        ret = -EBUSY;
                break;
        }
        return ret;
}

static void serial8250_release_std_resource(struct uart_8250_port *up)
{
        unsigned int size = serial8250_port_size(up);

        switch (up->port.iotype) {
        case UPIO_AU:
        case UPIO_TSI:
        case UPIO_MEM32:
        case UPIO_MEM:
        case UPIO_DWAPB:
                if (!up->port.mapbase)
                        break;

                if (up->port.flags & UPF_IOREMAP) {
                        iounmap(up->port.membase);
                        up->port.membase = NULL;
                }

                release_mem_region(up->port.mapbase, size);
                break;

        case UPIO_HUB6:
        case UPIO_PORT:
                release_region(up->port.iobase, size);
                break;
        }
}

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;
        int ret = -EINVAL;

        switch (up->port.iotype) {
        case UPIO_HUB6:
        case UPIO_PORT:
                start += up->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;

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

static void serial8250_release_port(struct uart_port *port)
{
        struct uart_8250_port *up = (struct uart_8250_port *)port;

        serial8250_release_std_resource(up);
        if (up->port.type == PORT_RSA)
                serial8250_release_rsa_resource(up);
}

static int serial8250_request_port(struct uart_port *port)
{
        struct uart_8250_port *up = (struct uart_8250_port *)port;
        int ret = 0;

        ret = serial8250_request_std_resource(up);
        if (ret == 0 && up->port.type == PORT_RSA) {
                ret = serial8250_request_rsa_resource(up);
                if (ret < 0)
                        serial8250_release_std_resource(up);
        }

        return ret;
}

static void serial8250_config_port(struct uart_port *port, int flags)
{
        struct uart_8250_port *up = (struct uart_8250_port *)port;
        int probeflags = PROBE_ANY;
        int ret;

        /*
         * Find the region that we can probe for.  This in turn
         * tells us whether we can probe for the type of port.
         */
        ret = serial8250_request_std_resource(up);
        if (ret < 0)
                return;

        ret = serial8250_request_rsa_resource(up);
        if (ret < 0)
                probeflags &= ~PROBE_RSA;

        if (flags & UART_CONFIG_TYPE)
                autoconfig(up, probeflags);
        if (up->port.type != PORT_UNKNOWN && flags & UART_CONFIG_IRQ)
                autoconfig_irq(up);

        if (up->port.type != PORT_RSA && probeflags & PROBE_RSA)
                serial8250_release_rsa_resource(up);
        if (up->port.type == PORT_UNKNOWN)
                serial8250_release_std_resource(up);
}

static int
serial8250_verify_port(struct uart_port *port, struct serial_struct *ser)
{
        if (ser->irq >= nr_irqs || ser->irq < 0 ||
            ser->baud_base < 9600 || ser->type < PORT_UNKNOWN ||
            ser->type >= ARRAY_SIZE(uart_config) || ser->type == PORT_CIRRUS ||
            ser->type == PORT_STARTECH)
                return -EINVAL;
        return 0;
}

static const char *
serial8250_type(struct uart_port *port)
{
        int type = port->type;

        if (type >= ARRAY_SIZE(uart_config))
                type = 0;
        return uart_config[type].name;
}

static struct uart_ops serial8250_pops = {
        .tx_empty       = serial8250_tx_empty,
        .set_mctrl      = serial8250_set_mctrl,
        .get_mctrl      = serial8250_get_mctrl,
        .stop_tx        = serial8250_stop_tx,
        .start_tx       = serial8250_start_tx,
        .stop_rx        = serial8250_stop_rx,
        .enable_ms      = serial8250_enable_ms,
        .break_ctl      = serial8250_break_ctl,
        .startup        = serial8250_startup,
        .shutdown       = serial8250_shutdown,
        .set_termios    = serial8250_set_termios,
        .pm             = serial8250_pm,
        .type           = serial8250_type,
        .release_port   = serial8250_release_port,
        .request_port   = serial8250_request_port,
        .config_port    = serial8250_config_port,
        .verify_port    = serial8250_verify_port,
#ifdef CONFIG_CONSOLE_POLL
        .poll_get_char = serial8250_get_poll_char,
        .poll_put_char = serial8250_put_poll_char,
#endif
};

static struct uart_8250_port serial8250_ports[UART_NR];

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

        if (!first)
                return;
        first = 0;

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

                up->port.line = i;
                spin_lock_init(&up->port.lock);

                init_timer(&up->timer);
                up->timer.function = serial8250_timeout;

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

                up->port.ops = &serial8250_pops;
        }

        for (i = 0, up = serial8250_ports;
             i < ARRAY_SIZE(old_serial_port) && i < nr_uarts;
             i++, up++) {
                up->port.iobase   = old_serial_port[i].port;
                up->port.irq      = irq_canonicalize(old_serial_port[i].irq);
                up->port.uartclk  = old_serial_port[i].baud_base * 16;
                up->port.flags    = old_serial_port[i].flags;
                up->port.hub6     = old_serial_port[i].hub6;
                up->port.membase  = old_serial_port[i].iomem_base;
                up->port.iotype   = old_serial_port[i].io_type;
                up->port.regshift = old_serial_port[i].iomem_reg_shift;
                if (share_irqs)
                        up->port.flags |= UPF_SHARE_IRQ;
        }
}

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

        serial8250_isa_init_ports();

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

                up->port.dev = dev;
                uart_add_one_port(drv, &up->port);
        }
}

#ifdef CONFIG_SERIAL_8250_CONSOLE

static void serial8250_console_putchar(struct uart_port *port, int ch)
{
        struct uart_8250_port *up = (struct uart_8250_port *)port;

        wait_for_xmitr(up, UART_LSR_THRE);
        serial_out(up, UART_TX, ch);
}

/*
 *      Print a string to the serial port trying not to disturb
 *      any possible real use of the port...
 *
 *      The console_lock must be held when we get here.
 */
static void
serial8250_console_write(struct console *co, const char *s, unsigned int count)
{
        struct uart_8250_port *up = &serial8250_ports[co->index];
        unsigned long flags;
        unsigned int ier;
        int locked = 1;

        touch_nmi_watchdog();

        local_irq_save(flags);
        if (up->port.sysrq) {
                /* serial8250_handle_port() already took the lock */
                locked = 0;
        } else if (oops_in_progress) {
                locked = spin_trylock(&up->port.lock);
        } else
                spin_lock(&up->port.lock);

        /*
         *      First save the IER then disable the interrupts
         */
        ier = serial_in(up, UART_IER);

        if (up->capabilities & UART_CAP_UUE)
                serial_out(up, UART_IER, UART_IER_UUE);
        else
                serial_out(up, UART_IER, 0);

        uart_console_write(&up->port, s, count, serial8250_console_putchar);

        /*
         *      Finally, wait for transmitter to become empty
         *      and restore the IER
         */
        wait_for_xmitr(up, BOTH_EMPTY);
        serial_out(up, UART_IER, ier);

        /*
         *      The receive handling will happen properly because the
         *      receive ready bit will still be set; it is not cleared
         *      on read.  However, modem control will not, we must
         *      call it if we have saved something in the saved flags
         *      while processing with interrupts off.
         */
        if (up->msr_saved_flags)
                check_modem_status(up);

        if (locked)
                spin_unlock(&up->port.lock);
        local_irq_restore(flags);
}

static int __init serial8250_console_setup(struct console *co, char *options)
{
        struct uart_port *port;
        int baud = 9600;
        int bits = 8;
        int parity = 'n';
        int flow = 'n';

        /*
         * 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;
        if (!port->iobase && !port->membase)
                return -ENODEV;

        if (options)
                uart_parse_options(options, &baud, &parity, &bits, &flow);

        return uart_set_options(port, co, baud, parity, bits, flow);
}

static int serial8250_console_early_setup(void)
{
        return serial8250_find_port_for_earlycon();
}

static struct console serial8250_console = {
        .name           = "ttyS",
        .write          = serial8250_console_write,
        .device         = uart_console_device,
        .setup          = serial8250_console_setup,
        .early_setup    = serial8250_console_early_setup,
        .flags          = CON_PRINTBUFFER,
        .index          = -1,
        .data           = &serial8250_reg,
};

static int __init serial8250_console_init(void)
{
        if (nr_uarts > UART_NR)
                nr_uarts = UART_NR;

        serial8250_isa_init_ports();
        register_console(&serial8250_console);
        return 0;
}
console_initcall(serial8250_console_init);

int serial8250_find_port(struct uart_port *p)
{
        int line;
        struct uart_port *port;

        for (line = 0; line < nr_uarts; line++) {
                port = &serial8250_ports[line].port;
                if (uart_match_port(p, port))
                        return line;
        }
        return -ENODEV;
}

#define SERIAL8250_CONSOLE      &serial8250_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)
{
        if (port->line >= ARRAY_SIZE(serial8250_ports))
                return -ENODEV;

        serial8250_isa_init_ports();
        serial8250_ports[port->line].port       = *port;
        serial8250_ports[port->line].port.ops   = &serial8250_pops;
        return 0;
}

/**
 *      serial8250_suspend_port - suspend one serial port
 *      @line:  serial line number
 *
 *      Suspend one serial port.
 */
void serial8250_suspend_port(int line)
{
        uart_suspend_port(&serial8250_reg, &serial8250_ports[line].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];

        if (up->capabilities & UART_NATSEMI) {
                unsigned char tmp;

                /* Ensure it's still in high speed mode */
                serial_outp(up, UART_LCR, 0xE0);

                tmp = serial_in(up, 0x04); /* EXCR2 */
                tmp &= ~0xB0; /* Disable LOCK, mask out PRESL[01] */
                tmp |= 0x10;  /* 1.625 divisor for baud_base --> 921600 */
                serial_outp(up, 0x04, tmp);

                serial_outp(up, UART_LCR, 0);
        }
        uart_resume_port(&serial8250_reg, &up->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 __devinit serial8250_probe(struct platform_device *dev)
{
        struct plat_serial8250_port *p = dev->dev.platform_data;
        struct uart_port port;
        int ret, i;

        memset(&port, 0, sizeof(struct uart_port));

        for (i = 0; p && p->flags != 0; p++, i++) {
                port.iobase             = p->iobase;
                port.membase            = p->membase;
                port.irq                = p->irq;
                port.uartclk            = p->uartclk;
                port.regshift           = p->regshift;
                port.iotype             = p->iotype;
                port.flags              = p->flags;
                port.mapbase            = p->mapbase;
                port.hub6               = p->hub6;
                port.private_data       = p->private_data;
                port.dev                = &dev->dev;
                if (share_irqs)
                        port.flags |= UPF_SHARE_IRQ;
                ret = serial8250_register_port(&port);
                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 __devexit 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         = __devexit_p(serial8250_remove),
        .suspend        = serial8250_suspend,
        .resume         = serial8250_resume,
        .driver         = {
                .name   = "serial8250",
                .owner  = THIS_MODULE,
        },
};

/*
 * 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_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];

        /*
         * 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;
}

/**
 *      serial8250_register_port - register a serial port
 *      @port: 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_port(struct uart_port *port)
{
        struct uart_8250_port *uart;
        int ret = -ENOSPC;

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

        mutex_lock(&serial_mutex);

        uart = serial8250_find_match_or_unused(port);
        if (uart) {
                uart_remove_one_port(&serial8250_reg, &uart->port);

                uart->port.iobase       = port->iobase;
                uart->port.membase      = port->membase;
                uart->port.irq          = port->irq;
                uart->port.uartclk      = port->uartclk;
                uart->port.fifosize     = port->fifosize;
                uart->port.regshift     = port->regshift;
                uart->port.iotype       = port->iotype;
                uart->port.flags        = port->flags | UPF_BOOT_AUTOCONF;
                uart->port.mapbase      = port->mapbase;
                uart->port.private_data = port->private_data;
                if (port->dev)
                        uart->port.dev = port->dev;

                ret = uart_add_one_port(&serial8250_reg, &uart->port);
                if (ret == 0)
                        ret = uart->port.line;
        }
        mutex_unlock(&serial_mutex);

        return ret;
}
EXPORT_SYMBOL(serial8250_register_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);