// SPDX-License-Identifier: GPL-2.0+
/*
 *  Base port operations for 8250/16550-type serial ports
 *
 *  Based on drivers/char/serial.c, by Linus Torvalds, Theodore Ts'o.
 *  Split from 8250_core.c, Copyright (C) 2001 Russell King.
 *
 * 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/ratelimit.h>
#include <linux/tty_flip.h>
#include <linux/serial.h>
#include <linux/serial_8250.h>
#include <linux/nmi.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/pm_runtime.h>
#include <linux/ktime.h>

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

#include "8250.h"

/*
 * These are definitions for the Exar XR17V35X and XR17(C|D)15X
 */
#define UART_EXAR_INT0          0x80
#define UART_EXAR_SLEEP         0x8b    /* Sleep mode */
#define UART_EXAR_DVID          0x8d    /* Device identification */

/* Nuvoton NPCM timeout register */
#define UART_NPCM_TOR          7
#define UART_NPCM_TOIE         BIT(7)  /* Timeout Interrupt Enable */

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

#define BOTH_EMPTY      (UART_LSR_TEMT | UART_LSR_THRE)

/*
 * 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,
                .rxtrig_bytes   = {1, 4, 8, 14},
                .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,
                .rxtrig_bytes   = {8, 16, 24, 28},
                .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,
                .rxtrig_bytes   = {1, 16, 32, 56},
                .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,
                /* UART_CAP_EFR breaks billionon CF bluetooth card. */
                .flags          = UART_CAP_FIFO | UART_CAP_SLEEP,
        },
        [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,
                .rxtrig_bytes   = {8, 16, 56, 60},
                .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 | UART_CAP_RTOIE,
        },
        [PORT_OCTEON] = {
                .name           = "OCTEON",
                .fifo_size      = 64,
                .tx_loadsz      = 64,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
                .flags          = UART_CAP_FIFO,
        },
        [PORT_AR7] = {
                .name           = "AR7",
                .fifo_size      = 16,
                .tx_loadsz      = 16,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_00,
                .flags          = UART_CAP_FIFO /* | UART_CAP_AFE */,
        },
        [PORT_U6_16550A] = {
                .name           = "U6_16550A",
                .fifo_size      = 64,
                .tx_loadsz      = 64,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
                .flags          = UART_CAP_FIFO | UART_CAP_AFE,
        },
        [PORT_TEGRA] = {
                .name           = "Tegra",
                .fifo_size      = 32,
                .tx_loadsz      = 8,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_01 |
                                  UART_FCR_T_TRIG_01,
                .rxtrig_bytes   = {1, 4, 8, 14},
                .flags          = UART_CAP_FIFO | UART_CAP_RTOIE,
        },
        [PORT_XR17D15X] = {
                .name           = "XR17D15X",
                .fifo_size      = 64,
                .tx_loadsz      = 64,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
                .flags          = UART_CAP_FIFO | UART_CAP_AFE | UART_CAP_EFR |
                                  UART_CAP_SLEEP,
        },
        [PORT_XR17V35X] = {
                .name           = "XR17V35X",
                .fifo_size      = 256,
                .tx_loadsz      = 256,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_11 |
                                  UART_FCR_T_TRIG_11,
                .flags          = UART_CAP_FIFO | UART_CAP_AFE | UART_CAP_EFR |
                                  UART_CAP_SLEEP,
        },
        [PORT_LPC3220] = {
                .name           = "LPC3220",
                .fifo_size      = 64,
                .tx_loadsz      = 32,
                .fcr            = UART_FCR_DMA_SELECT | UART_FCR_ENABLE_FIFO |
                                  UART_FCR_R_TRIG_00 | UART_FCR_T_TRIG_00,
                .flags          = UART_CAP_FIFO,
        },
        [PORT_BRCM_TRUMANAGE] = {
                .name           = "TruManage",
                .fifo_size      = 1,
                .tx_loadsz      = 1024,
                .flags          = UART_CAP_HFIFO,
        },
        [PORT_8250_CIR] = {
                .name           = "CIR port"
        },
        [PORT_ALTR_16550_F32] = {
                .name           = "Altera 16550 FIFO32",
                .fifo_size      = 32,
                .tx_loadsz      = 32,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
                .rxtrig_bytes   = {1, 8, 16, 30},
                .flags          = UART_CAP_FIFO | UART_CAP_AFE,
        },
        [PORT_ALTR_16550_F64] = {
                .name           = "Altera 16550 FIFO64",
                .fifo_size      = 64,
                .tx_loadsz      = 64,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
                .rxtrig_bytes   = {1, 16, 32, 62},
                .flags          = UART_CAP_FIFO | UART_CAP_AFE,
        },
        [PORT_ALTR_16550_F128] = {
                .name           = "Altera 16550 FIFO128",
                .fifo_size      = 128,
                .tx_loadsz      = 128,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
                .rxtrig_bytes   = {1, 32, 64, 126},
                .flags          = UART_CAP_FIFO | UART_CAP_AFE,
        },
        /*
         * tx_loadsz is set to 63-bytes instead of 64-bytes to implement
         * workaround of errata A-008006 which states that tx_loadsz should
         * be configured less than Maximum supported fifo bytes.
         */
        [PORT_16550A_FSL64] = {
                .name           = "16550A_FSL64",
                .fifo_size      = 64,
                .tx_loadsz      = 63,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10 |
                                  UART_FCR7_64BYTE,
                .flags          = UART_CAP_FIFO,
        },
        [PORT_RT2880] = {
                .name           = "Palmchip BK-3103",
                .fifo_size      = 16,
                .tx_loadsz      = 16,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
                .rxtrig_bytes   = {1, 4, 8, 14},
                .flags          = UART_CAP_FIFO,
        },
        [PORT_DA830] = {
                .name           = "TI DA8xx/66AK2x",
                .fifo_size      = 16,
                .tx_loadsz      = 16,
                .fcr            = UART_FCR_DMA_SELECT | UART_FCR_ENABLE_FIFO |
                                  UART_FCR_R_TRIG_10,
                .rxtrig_bytes   = {1, 4, 8, 14},
                .flags          = UART_CAP_FIFO | UART_CAP_AFE,
        },
        [PORT_MTK_BTIF] = {
                .name           = "MediaTek BTIF",
                .fifo_size      = 16,
                .tx_loadsz      = 16,
                .fcr            = UART_FCR_ENABLE_FIFO |
                                  UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT,
                .flags          = UART_CAP_FIFO,
        },
        [PORT_NPCM] = {
                .name           = "Nuvoton 16550",
                .fifo_size      = 16,
                .tx_loadsz      = 16,
                .fcr            = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10 |
                                  UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT,
                .rxtrig_bytes   = {1, 4, 8, 14},
                .flags          = UART_CAP_FIFO,
        },
};

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

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

#ifdef CONFIG_SERIAL_8250_RT288X

/* Au1x00/RT288x UART hardware has a weird register layout */
static const s8 au_io_in_map[8] = {
         0,     /* UART_RX  */
         2,     /* UART_IER */
         3,     /* UART_IIR */
         5,     /* UART_LCR */
         6,     /* UART_MCR */
         7,     /* UART_LSR */
         8,     /* UART_MSR */
        -1,     /* UART_SCR (unmapped) */
};

static const s8 au_io_out_map[8] = {
         1,     /* UART_TX  */
         2,     /* UART_IER */
         4,     /* UART_FCR */
         5,     /* UART_LCR */
         6,     /* UART_MCR */
        -1,     /* UART_LSR (unmapped) */
        -1,     /* UART_MSR (unmapped) */
        -1,     /* UART_SCR (unmapped) */
};

unsigned int au_serial_in(struct uart_port *p, int offset)
{
        if (offset >= ARRAY_SIZE(au_io_in_map))
                return UINT_MAX;
        offset = au_io_in_map[offset];
        if (offset < 0)
                return UINT_MAX;
        return __raw_readl(p->membase + (offset << p->regshift));
}

void au_serial_out(struct uart_port *p, int offset, int value)
{
        if (offset >= ARRAY_SIZE(au_io_out_map))
                return;
        offset = au_io_out_map[offset];
        if (offset < 0)
                return;
        __raw_writel(value, p->membase + (offset << p->regshift));
}

/* Au1x00 haven't got a standard divisor latch */
static int au_serial_dl_read(struct uart_8250_port *up)
{
        return __raw_readl(up->port.membase + 0x28);
}

static void au_serial_dl_write(struct uart_8250_port *up, int value)
{
        __raw_writel(value, up->port.membase + 0x28);
}

#endif

static unsigned int hub6_serial_in(struct uart_port *p, int offset)
{
        offset = offset << p->regshift;
        outb(p->hub6 - 1 + offset, p->iobase);
        return inb(p->iobase + 1);
}

static void hub6_serial_out(struct uart_port *p, int offset, int value)
{
        offset = offset << p->regshift;
        outb(p->hub6 - 1 + offset, p->iobase);
        outb(value, p->iobase + 1);
}

static unsigned int mem_serial_in(struct uart_port *p, int offset)
{
        offset = offset << p->regshift;
        return readb(p->membase + offset);
}

static void mem_serial_out(struct uart_port *p, int offset, int value)
{
        offset = offset << p->regshift;
        writeb(value, p->membase + offset);
}

static void mem16_serial_out(struct uart_port *p, int offset, int value)
{
        offset = offset << p->regshift;
        writew(value, p->membase + offset);
}

static unsigned int mem16_serial_in(struct uart_port *p, int offset)
{
        offset = offset << p->regshift;
        return readw(p->membase + offset);
}

static void mem32_serial_out(struct uart_port *p, int offset, int value)
{
        offset = offset << p->regshift;
        writel(value, p->membase + offset);
}

static unsigned int mem32_serial_in(struct uart_port *p, int offset)
{
        offset = offset << p->regshift;
        return readl(p->membase + offset);
}

static void mem32be_serial_out(struct uart_port *p, int offset, int value)
{
        offset = offset << p->regshift;
        iowrite32be(value, p->membase + offset);
}

static unsigned int mem32be_serial_in(struct uart_port *p, int offset)
{
        offset = offset << p->regshift;
        return ioread32be(p->membase + offset);
}

static unsigned int io_serial_in(struct uart_port *p, int offset)
{
        offset = offset << p->regshift;
        return inb(p->iobase + offset);
}

static void io_serial_out(struct uart_port *p, int offset, int value)
{
        offset = offset << p->regshift;
        outb(value, p->iobase + offset);
}

static int serial8250_default_handle_irq(struct uart_port *port);

static void set_io_from_upio(struct uart_port *p)
{
        struct uart_8250_port *up = up_to_u8250p(p);

        up->dl_read = default_serial_dl_read;
        up->dl_write = default_serial_dl_write;

        switch (p->iotype) {
        case UPIO_HUB6:
                p->serial_in = hub6_serial_in;
                p->serial_out = hub6_serial_out;
                break;

        case UPIO_MEM:
                p->serial_in = mem_serial_in;
                p->serial_out = mem_serial_out;
                break;

        case UPIO_MEM16:
                p->serial_in = mem16_serial_in;
                p->serial_out = mem16_serial_out;
                break;

        case UPIO_MEM32:
                p->serial_in = mem32_serial_in;
                p->serial_out = mem32_serial_out;
                break;

        case UPIO_MEM32BE:
                p->serial_in = mem32be_serial_in;
                p->serial_out = mem32be_serial_out;
                break;

#ifdef CONFIG_SERIAL_8250_RT288X
        case UPIO_AU:
                p->serial_in = au_serial_in;
                p->serial_out = au_serial_out;
                up->dl_read = au_serial_dl_read;
                up->dl_write = au_serial_dl_write;
                break;
#endif

        default:
                p->serial_in = io_serial_in;
                p->serial_out = io_serial_out;
                break;
        }
        /* Remember loaded iotype */
        up->cur_iotype = p->iotype;
        p->handle_irq = serial8250_default_handle_irq;
}

static void
serial_port_out_sync(struct uart_port *p, int offset, int value)
{
        switch (p->iotype) {
        case UPIO_MEM:
        case UPIO_MEM16:
        case UPIO_MEM32:
        case UPIO_MEM32BE:
        case UPIO_AU:
                p->serial_out(p, offset, value);
                p->serial_in(p, UART_LCR);      /* safe, no side-effects */
                break;
        default:
                p->serial_out(p, offset, value);
        }
}

/*
 * 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_out(p, UART_FCR, UART_FCR_ENABLE_FIFO);
                serial_out(p, UART_FCR, UART_FCR_ENABLE_FIFO |
                               UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT);
                serial_out(p, UART_FCR, 0);
        }
}

static inline void serial8250_em485_rts_after_send(struct uart_8250_port *p)
{
        unsigned char mcr = serial8250_in_MCR(p);

        if (p->port.rs485.flags & SER_RS485_RTS_AFTER_SEND)
                mcr |= UART_MCR_RTS;
        else
                mcr &= ~UART_MCR_RTS;
        serial8250_out_MCR(p, mcr);
}

static enum hrtimer_restart serial8250_em485_handle_start_tx(struct hrtimer *t);
static enum hrtimer_restart serial8250_em485_handle_stop_tx(struct hrtimer *t);

void serial8250_clear_and_reinit_fifos(struct uart_8250_port *p)
{
        serial8250_clear_fifos(p);
        serial_out(p, UART_FCR, p->fcr);
}
EXPORT_SYMBOL_GPL(serial8250_clear_and_reinit_fifos);

void serial8250_rpm_get(struct uart_8250_port *p)
{
        if (!(p->capabilities & UART_CAP_RPM))
                return;
        pm_runtime_get_sync(p->port.dev);
}
EXPORT_SYMBOL_GPL(serial8250_rpm_get);

void serial8250_rpm_put(struct uart_8250_port *p)
{
        if (!(p->capabilities & UART_CAP_RPM))
                return;
        pm_runtime_mark_last_busy(p->port.dev);
        pm_runtime_put_autosuspend(p->port.dev);
}
EXPORT_SYMBOL_GPL(serial8250_rpm_put);

/**
 *      serial8250_em485_init() - put uart_8250_port into rs485 emulating
 *      @p:     uart_8250_port port instance
 *
 *      The function is used to start rs485 software emulating on the
 *      &struct uart_8250_port* @p. Namely, RTS is switched before/after
 *      transmission. The function is idempotent, so it is safe to call it
 *      multiple times.
 *
 *      The caller MUST enable interrupt on empty shift register before
 *      calling serial8250_em485_init(). This interrupt is not a part of
 *      8250 standard, but implementation defined.
 *
 *      The function is supposed to be called from .rs485_config callback
 *      or from any other callback protected with p->port.lock spinlock.
 *
 *      See also serial8250_em485_destroy()
 *
 *      Return 0 - success, -errno - otherwise
 */
int serial8250_em485_init(struct uart_8250_port *p)
{
        if (p->em485)
                return 0;

        p->em485 = kmalloc(sizeof(struct uart_8250_em485), GFP_ATOMIC);
        if (!p->em485)
                return -ENOMEM;

        hrtimer_init(&p->em485->stop_tx_timer, CLOCK_MONOTONIC,
                     HRTIMER_MODE_REL);
        hrtimer_init(&p->em485->start_tx_timer, CLOCK_MONOTONIC,
                     HRTIMER_MODE_REL);
        p->em485->stop_tx_timer.function = &serial8250_em485_handle_stop_tx;
        p->em485->start_tx_timer.function = &serial8250_em485_handle_start_tx;
        p->em485->port = p;
        p->em485->active_timer = NULL;
        serial8250_em485_rts_after_send(p);

        return 0;
}
EXPORT_SYMBOL_GPL(serial8250_em485_init);

/**
 *      serial8250_em485_destroy() - put uart_8250_port into normal state
 *      @p:     uart_8250_port port instance
 *
 *      The function is used to stop rs485 software emulating on the
 *      &struct uart_8250_port* @p. The function is idempotent, so it is safe to
 *      call it multiple times.
 *
 *      The function is supposed to be called from .rs485_config callback
 *      or from any other callback protected with p->port.lock spinlock.
 *
 *      See also serial8250_em485_init()
 */
void serial8250_em485_destroy(struct uart_8250_port *p)
{
        if (!p->em485)
                return;

        hrtimer_cancel(&p->em485->start_tx_timer);
        hrtimer_cancel(&p->em485->stop_tx_timer);

        kfree(p->em485);
        p->em485 = NULL;
}
EXPORT_SYMBOL_GPL(serial8250_em485_destroy);

/*
 * These two wrappers ensure that enable_runtime_pm_tx() can be called more than
 * once and disable_runtime_pm_tx() will still disable RPM because the fifo is
 * empty and the HW can idle again.
 */
void serial8250_rpm_get_tx(struct uart_8250_port *p)
{
        unsigned char rpm_active;

        if (!(p->capabilities & UART_CAP_RPM))
                return;

        rpm_active = xchg(&p->rpm_tx_active, 1);
        if (rpm_active)
                return;
        pm_runtime_get_sync(p->port.dev);
}
EXPORT_SYMBOL_GPL(serial8250_rpm_get_tx);

void serial8250_rpm_put_tx(struct uart_8250_port *p)
{
        unsigned char rpm_active;

        if (!(p->capabilities & UART_CAP_RPM))
                return;

        rpm_active = xchg(&p->rpm_tx_active, 0);
        if (!rpm_active)
                return;
        pm_runtime_mark_last_busy(p->port.dev);
        pm_runtime_put_autosuspend(p->port.dev);
}
EXPORT_SYMBOL_GPL(serial8250_rpm_put_tx);

/*
 * 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)
{
        unsigned char lcr = 0, efr = 0;
        /*
         * Exar UARTs have a SLEEP register that enables or disables
         * each UART to enter sleep mode separately.  On the XR17V35x the
         * register is accessible to each UART at the UART_EXAR_SLEEP
         * offset but the UART channel may only write to the corresponding
         * bit.
         */
        serial8250_rpm_get(p);
        if ((p->port.type == PORT_XR17V35X) ||
           (p->port.type == PORT_XR17D15X)) {
                serial_out(p, UART_EXAR_SLEEP, sleep ? 0xff : 0);
                goto out;
        }

        if (p->capabilities & UART_CAP_SLEEP) {
                if (p->capabilities & UART_CAP_EFR) {
                        lcr = serial_in(p, UART_LCR);
                        efr = serial_in(p, UART_EFR);
                        serial_out(p, UART_LCR, UART_LCR_CONF_MODE_B);
                        serial_out(p, UART_EFR, UART_EFR_ECB);
                        serial_out(p, UART_LCR, 0);
                }
                serial_out(p, UART_IER, sleep ? UART_IERX_SLEEP : 0);
                if (p->capabilities & UART_CAP_EFR) {
                        serial_out(p, UART_LCR, UART_LCR_CONF_MODE_B);
                        serial_out(p, UART_EFR, efr);
                        serial_out(p, UART_LCR, lcr);
                }
        }
out:
        serial8250_rpm_put(p);
}

#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_in(up, UART_RSA_MSR);
        result = mode & UART_RSA_MSR_FIFO;

        if (!result) {
                serial_out(up, UART_RSA_MSR, mode | UART_RSA_MSR_FIFO);
                mode = serial_in(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_out(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_in(up, UART_RSA_MSR);
                result = !(mode & UART_RSA_MSR_FIFO);

                if (!result) {
                        serial_out(up, UART_RSA_MSR, mode & ~UART_RSA_MSR_FIFO);
                        mode = serial_in(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_in(up, UART_LCR);
        serial_out(up, UART_LCR, 0);
        old_fcr = serial_in(up, UART_FCR);
        old_mcr = serial8250_in_MCR(up);
        serial_out(up, UART_FCR, UART_FCR_ENABLE_FIFO |
                    UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT);
        serial8250_out_MCR(up, UART_MCR_LOOP);
        serial_out(up, UART_LCR, UART_LCR_CONF_MODE_A);
        old_dl = serial_dl_read(up);
        serial_dl_write(up, 0x0001);
        serial_out(up, UART_LCR, 0x03);
        for (count = 0; count < 256; count++)
                serial_out(up, UART_TX, count);
        mdelay(20);/* FIXME - schedule_timeout */
        for (count = 0; (serial_in(up, UART_LSR) & UART_LSR_DR) &&
             (count < 256); count++)
                serial_in(up, UART_RX);
        serial_out(up, UART_FCR, old_fcr);
        serial8250_out_MCR(up, old_mcr);
        serial_out(up, UART_LCR, UART_LCR_CONF_MODE_A);
        serial_dl_write(up, old_dl);
        serial_out(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_lcr;
        unsigned int id, old_dl;

        old_lcr = serial_in(p, UART_LCR);
        serial_out(p, UART_LCR, UART_LCR_CONF_MODE_A);
        old_dl = serial_dl_read(p);
        serial_dl_write(p, 0);
        id = serial_dl_read(p);
        serial_dl_write(p, old_dl);

        serial_out(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, UART_LCR_CONF_MODE_B);
        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_out(up, UART_SCR, 0xa5);
        status1 = serial_in(up, UART_SCR);
        serial_out(up, UART_SCR, 0x5a);
        status2 = serial_in(up, UART_SCR);
        serial_out(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://linux.derkeiler.com/Mailing-Lists/Kernel/2004-11/4812.html
         */
        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;

        /*
         * XR17V35x UARTs have an extra divisor register, DLD
         * that gets enabled with when DLAB is set which will
         * cause the device to incorrectly match and assign
         * port type to PORT_16650.  The EFR for this UART is
         * found at offset 0x09. Instead check the Deice ID (DVID)
         * register for a 2, 4 or 8 port UART.
         */
        if (up->port.flags & UPF_EXAR_EFR) {
                status1 = serial_in(up, UART_EXAR_DVID);
                if (status1 == 0x82 || status1 == 0x84 || status1 == 0x88) {
                        DEBUG_AUTOCONF("Exar XR17V35x ");
                        up->port.type = PORT_XR17V35X;
                        up->capabilities |= UART_CAP_AFE | UART_CAP_EFR |
                                                UART_CAP_SLEEP;

                        return;
                }

        }

        /*
         * Check for presence of the EFR when DLAB is set.
         * Only ST16C650V1 UARTs pass this test.
         */
        serial_out(up, UART_LCR, UART_LCR_CONF_MODE_A);
        if (serial_in(up, UART_EFR) == 0) {
                serial_out(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 {
                        serial_out(up, UART_LCR, 0);
                        serial_out(up, UART_FCR, UART_FCR_ENABLE_FIFO |
                                   UART_FCR7_64BYTE);
                        status1 = serial_in(up, UART_IIR) >> 5;
                        serial_out(up, UART_FCR, 0);
                        serial_out(up, UART_LCR, 0);

                        if (status1 == 7)
                                up->port.type = PORT_16550A_FSL64;
                        else
                                DEBUG_AUTOCONF("Motorola 8xxx DUART ");
                }
                serial_out(up, UART_EFR, 0);
                return;
        }

        /*
         * Maybe it requires 0xbf to be written to the LCR.
         * (other ST16C650V2 UARTs, TI16C752A, etc)
         */
        serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
        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_out(up, UART_LCR, 0);
        status1 = serial8250_in_MCR(up);
        serial_out(up, UART_LCR, 0xE0);
        status2 = serial_in(up, 0x02); /* EXCR1 */

        if (!((status2 ^ status1) & UART_MCR_LOOP)) {
                serial_out(up, UART_LCR, 0);
                serial8250_out_MCR(up, status1 ^ UART_MCR_LOOP);
                serial_out(up, UART_LCR, 0xE0);
                status2 = serial_in(up, 0x02); /* EXCR1 */
                serial_out(up, UART_LCR, 0);
                serial8250_out_MCR(up, status1);

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

                        serial_out(up, UART_LCR, 0xE0);

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

                        if (ns16550a_goto_highspeed(up))
                                serial_dl_write(up, quot);

                        serial_out(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_out(up, UART_LCR, 0);
        serial_out(up, UART_FCR, UART_FCR_ENABLE_FIFO | UART_FCR7_64BYTE);
        status1 = serial_in(up, UART_IIR) >> 5;
        serial_out(up, UART_FCR, UART_FCR_ENABLE_FIFO);
        serial_out(up, UART_LCR, UART_LCR_CONF_MODE_A);
        serial_out(up, UART_FCR, UART_FCR_ENABLE_FIFO | UART_FCR7_64BYTE);
        status2 = serial_in(up, UART_IIR) >> 5;
        serial_out(up, UART_FCR, UART_FCR_ENABLE_FIFO);
        serial_out(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_out(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_out(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 | UART_CAP_RTOIE;
                        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_out(up, UART_IER, iersave);

        /*
         * Exar uarts have EFR in a weird location
         */
        if (up->port.flags & UPF_EXAR_EFR) {
                DEBUG_AUTOCONF("Exar XR17D15x ");
                up->port.type = PORT_XR17D15X;
                up->capabilities |= UART_CAP_AFE | UART_CAP_EFR |
                                    UART_CAP_SLEEP;

                return;
        }

        /*
         * We distinguish between 16550A and U6 16550A by counting
         * how many bytes are in the FIFO.
         */
        if (up->port.type == PORT_16550A && size_fifo(up) == 64) {
                up->port.type = PORT_U6_16550A;
                up->capabilities |= UART_CAP_AFE;
        }
}

/*
 * 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 char status1, scratch, scratch2, scratch3;
        unsigned char save_lcr, save_mcr;
        struct uart_port *port = &up->port;
        unsigned long flags;
        unsigned int old_capabilities;

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

        DEBUG_AUTOCONF("%s: autoconf (0x%04lx, 0x%p): ",
                       port->name, port->iobase, 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(&port->lock, flags);

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

        if (!(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_in(up, UART_IER);
                serial_out(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_in(up, UART_IER) & 0x0f;
                serial_out(up, UART_IER, 0x0F);
#ifdef __i386__
                outb(0, 0x080);
#endif
                scratch3 = serial_in(up, UART_IER) & 0x0f;
                serial_out(up, UART_IER, scratch);
                if (scratch2 != 0 || scratch3 != 0x0F) {
                        /*
                         * We failed; there's nothing here
                         */
                        spin_unlock_irqrestore(&port->lock, flags);
                        DEBUG_AUTOCONF("IER test failed (%02x, %02x) ",
                                       scratch2, scratch3);
                        goto out;
                }
        }

        save_mcr = serial8250_in_MCR(up);
        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 (!(port->flags & UPF_SKIP_TEST)) {
                serial8250_out_MCR(up, UART_MCR_LOOP | 0x0A);
                status1 = serial_in(up, UART_MSR) & 0xF0;
                serial8250_out_MCR(up, save_mcr);
                if (status1 != 0x90) {
                        spin_unlock_irqrestore(&port->lock, flags);
                        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_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
        serial_out(up, UART_EFR, 0);
        serial_out(up, UART_LCR, 0);

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

        switch (scratch) {
        case 0:
                autoconfig_8250(up);
                break;
        case 1:
                port->type = PORT_UNKNOWN;
                break;
        case 2:
                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 (port->type == PORT_16550A && up->probe & UART_PROBE_RSA &&
            __enable_rsa(up))
                port->type = PORT_RSA;
#endif

        serial_out(up, UART_LCR, save_lcr);

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

        if (port->type == PORT_UNKNOWN)
                goto out_lock;

        /*
         * Reset the UART.
         */
#ifdef CONFIG_SERIAL_8250_RSA
        if (port->type == PORT_RSA)
                serial_out(up, UART_RSA_FRR, 0);
#endif
        serial8250_out_MCR(up, save_mcr);
        serial8250_clear_fifos(up);
        serial_in(up, UART_RX);
        if (up->capabilities & UART_CAP_UUE)
                serial_out(up, UART_IER, UART_IER_UUE);
        else
                serial_out(up, UART_IER, 0);

out_lock:
        spin_unlock_irqrestore(&port->lock, flags);

        /*
         * Check if the device is a Fintek F81216A
         */
        if (port->type == PORT_16550A && port->iotype == UPIO_PORT)
                fintek_8250_probe(up);

        if (up->capabilities != old_capabilities) {
                pr_warn("%s: detected caps %08x should be %08x\n",
                        port->name, old_capabilities, up->capabilities);
        }
out:
        DEBUG_AUTOCONF("iir=%d ", scratch);
        DEBUG_AUTOCONF("type=%s\n", uart_config[port->type].name);
}

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

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

        if (uart_console(port))
                console_lock();

        /* forget possible initially masked and pending IRQ */
        probe_irq_off(probe_irq_on());
        save_mcr = serial8250_in_MCR(up);
        save_ier = serial_in(up, UART_IER);
        serial8250_out_MCR(up, UART_MCR_OUT1 | UART_MCR_OUT2);

        irqs = probe_irq_on();
        serial8250_out_MCR(up, 0);
        udelay(10);
        if (port->flags & UPF_FOURPORT) {
                serial8250_out_MCR(up, UART_MCR_DTR | UART_MCR_RTS);
        } else {
                serial8250_out_MCR(up,
                        UART_MCR_DTR | UART_MCR_RTS | UART_MCR_OUT2);
        }
        serial_out(up, UART_IER, 0x0f); /* enable all intrs */
        serial_in(up, UART_LSR);
        serial_in(up, UART_RX);
        serial_in(up, UART_IIR);
        serial_in(up, UART_MSR);
        serial_out(up, UART_TX, 0xFF);
        udelay(20);
        irq = probe_irq_off(irqs);

        serial8250_out_MCR(up, save_mcr);
        serial_out(up, UART_IER, save_ier);

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

        if (uart_console(port))
                console_unlock();

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

static void serial8250_stop_rx(struct uart_port *port)
{
        struct uart_8250_port *up = up_to_u8250p(port);

        serial8250_rpm_get(up);

        up->ier &= ~(UART_IER_RLSI | UART_IER_RDI);
        up->port.read_status_mask &= ~UART_LSR_DR;
        serial_port_out(port, UART_IER, up->ier);

        serial8250_rpm_put(up);
}

static void __do_stop_tx_rs485(struct uart_8250_port *p)
{
        serial8250_em485_rts_after_send(p);

        /*
         * Empty the RX FIFO, we are not interested in anything
         * received during the half-duplex transmission.
         * Enable previously disabled RX interrupts.
         */
        if (!(p->port.rs485.flags & SER_RS485_RX_DURING_TX)) {
                serial8250_clear_and_reinit_fifos(p);

                p->ier |= UART_IER_RLSI | UART_IER_RDI;
                serial_port_out(&p->port, UART_IER, p->ier);
        }
}
static enum hrtimer_restart serial8250_em485_handle_stop_tx(struct hrtimer *t)
{
        struct uart_8250_em485 *em485;
        struct uart_8250_port *p;
        unsigned long flags;

        em485 = container_of(t, struct uart_8250_em485, stop_tx_timer);
        p = em485->port;

        serial8250_rpm_get(p);
        spin_lock_irqsave(&p->port.lock, flags);
        if (em485->active_timer == &em485->stop_tx_timer) {
                __do_stop_tx_rs485(p);
                em485->active_timer = NULL;
        }
        spin_unlock_irqrestore(&p->port.lock, flags);
        serial8250_rpm_put(p);
        return HRTIMER_NORESTART;
}

static void start_hrtimer_ms(struct hrtimer *hrt, unsigned long msec)
{
        long sec = msec / 1000;
        long nsec = (msec % 1000) * 1000000;
        ktime_t t = ktime_set(sec, nsec);

        hrtimer_start(hrt, t, HRTIMER_MODE_REL);
}

static void __stop_tx_rs485(struct uart_8250_port *p)
{
        struct uart_8250_em485 *em485 = p->em485;

        /*
         * __do_stop_tx_rs485 is going to set RTS according to config
         * AND flush RX FIFO if required.
         */
        if (p->port.rs485.delay_rts_after_send > 0) {
                em485->active_timer = &em485->stop_tx_timer;
                start_hrtimer_ms(&em485->stop_tx_timer,
                                   p->port.rs485.delay_rts_after_send);
        } else {
                __do_stop_tx_rs485(p);
        }
}

static inline void __do_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);
                serial8250_rpm_put_tx(p);
        }
}

static inline void __stop_tx(struct uart_8250_port *p)
{
        struct uart_8250_em485 *em485 = p->em485;

        if (em485) {
                unsigned char lsr = serial_in(p, UART_LSR);
                /*
                 * To provide required timeing and allow FIFO transfer,
                 * __stop_tx_rs485() must be called only when both FIFO and
                 * shift register are empty. It is for device driver to enable
                 * interrupt on TEMT.
                 */
                if ((lsr & BOTH_EMPTY) != BOTH_EMPTY)
                        return;

                em485->active_timer = NULL;

                __stop_tx_rs485(p);
        }
        __do_stop_tx(p);
}

static void serial8250_stop_tx(struct uart_port *port)
{
        struct uart_8250_port *up = up_to_u8250p(port);

        serial8250_rpm_get(up);
        __stop_tx(up);

        /*
         * We really want to stop the transmitter from sending.
         */
        if (port->type == PORT_16C950) {
                up->acr |= UART_ACR_TXDIS;
                serial_icr_write(up, UART_ACR, up->acr);
        }
        serial8250_rpm_put(up);
}

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

        if (up->dma && !up->dma->tx_dma(up))
                return;

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

                if (up->bugs & UART_BUG_TXEN) {
                        unsigned char lsr;

                        lsr = serial_in(up, UART_LSR);
                        up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;
                        if (lsr & UART_LSR_THRE)
                                serial8250_tx_chars(up);
                }
        }

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

static inline void start_tx_rs485(struct uart_port *port)
{
        struct uart_8250_port *up = up_to_u8250p(port);
        struct uart_8250_em485 *em485 = up->em485;
        unsigned char mcr;

        if (!(up->port.rs485.flags & SER_RS485_RX_DURING_TX))
                serial8250_stop_rx(&up->port);

        em485->active_timer = NULL;

        mcr = serial8250_in_MCR(up);
        if (!!(up->port.rs485.flags & SER_RS485_RTS_ON_SEND) !=
            !!(mcr & UART_MCR_RTS)) {
                if (up->port.rs485.flags & SER_RS485_RTS_ON_SEND)
                        mcr |= UART_MCR_RTS;
                else
                        mcr &= ~UART_MCR_RTS;
                serial8250_out_MCR(up, mcr);

                if (up->port.rs485.delay_rts_before_send > 0) {
                        em485->active_timer = &em485->start_tx_timer;
                        start_hrtimer_ms(&em485->start_tx_timer,
                                         up->port.rs485.delay_rts_before_send);
                        return;
                }
        }

        __start_tx(port);
}

static enum hrtimer_restart serial8250_em485_handle_start_tx(struct hrtimer *t)
{
        struct uart_8250_em485 *em485;
        struct uart_8250_port *p;
        unsigned long flags;

        em485 = container_of(t, struct uart_8250_em485, start_tx_timer);
        p = em485->port;

        spin_lock_irqsave(&p->port.lock, flags);
        if (em485->active_timer == &em485->start_tx_timer) {
                __start_tx(&p->port);
                em485->active_timer = NULL;
        }
        spin_unlock_irqrestore(&p->port.lock, flags);
        return HRTIMER_NORESTART;
}

static void serial8250_start_tx(struct uart_port *port)
{
        struct uart_8250_port *up = up_to_u8250p(port);
        struct uart_8250_em485 *em485 = up->em485;

        serial8250_rpm_get_tx(up);

        if (em485 &&
            em485->active_timer == &em485->start_tx_timer)
                return;

        if (em485)
                start_tx_rs485(port);
        else
                __start_tx(port);
}

static void serial8250_throttle(struct uart_port *port)
{
        port->throttle(port);
}

static void serial8250_unthrottle(struct uart_port *port)
{
        port->unthrottle(port);
}

static void serial8250_disable_ms(struct uart_port *port)
{
        struct uart_8250_port *up = up_to_u8250p(port);

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

        up->ier &= ~UART_IER_MSI;
        serial_port_out(port, UART_IER, up->ier);
}

static void serial8250_enable_ms(struct uart_port *port)
{
        struct uart_8250_port *up = up_to_u8250p(port);

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

        up->ier |= UART_IER_MSI;

        serial8250_rpm_get(up);
        serial_port_out(port, UART_IER, up->ier);
        serial8250_rpm_put(up);
}

void serial8250_read_char(struct uart_8250_port *up, unsigned char lsr)
{
        struct uart_port *port = &up->port;
        unsigned char ch;
        char flag = TTY_NORMAL;

        if (likely(lsr & UART_LSR_DR))
                ch = serial_in(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;

        port->icount.rx++;

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

        if (unlikely(lsr & UART_LSR_BRK_ERROR_BITS)) {
                if (lsr & UART_LSR_BI) {
                        lsr &= ~(UART_LSR_FE | UART_LSR_PE);
                        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(port))
                                return;
                } else if (lsr & UART_LSR_PE)
                        port->icount.parity++;
                else if (lsr & UART_LSR_FE)
                        port->icount.frame++;
                if (lsr & UART_LSR_OE)
                        port->icount.overrun++;

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

                if (lsr & UART_LSR_BI) {
                        pr_debug("%s: handling break\n", __func__);
                        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(port, ch))
                return;

        uart_insert_char(port, lsr, UART_LSR_OE, ch, flag);
}
EXPORT_SYMBOL_GPL(serial8250_read_char);

/*
 * serial8250_rx_chars: processes according to the passed in LSR
 * value, and returns the remaining LSR bits not handled
 * by this Rx routine.
 */
unsigned char serial8250_rx_chars(struct uart_8250_port *up, unsigned char lsr)
{
        struct uart_port *port = &up->port;
        int max_count = 256;

        do {
                serial8250_read_char(up, lsr);
                if (--max_count == 0)
                        break;
                lsr = serial_in(up, UART_LSR);
        } while (lsr & (UART_LSR_DR | UART_LSR_BI));

        tty_flip_buffer_push(&port->state->port);
        return lsr;
}
EXPORT_SYMBOL_GPL(serial8250_rx_chars);

void serial8250_tx_chars(struct uart_8250_port *up)
{
        struct uart_port *port = &up->port;
        struct circ_buf *xmit = &port->state->xmit;
        int count;

        if (port->x_char) {
                serial_out(up, UART_TX, port->x_char);
                port->icount.tx++;
                port->x_char = 0;
                return;
        }
        if (uart_tx_stopped(port)) {
                serial8250_stop_tx(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);
                port->icount.tx++;
                if (uart_circ_empty(xmit))
                        break;
                if ((up->capabilities & UART_CAP_HFIFO) &&
                    (serial_in(up, UART_LSR) & BOTH_EMPTY) != BOTH_EMPTY)
                        break;
                /* The BCM2835 MINI UART THRE bit is really a not-full bit. */
                if ((up->capabilities & UART_CAP_MINI) &&
                    !(serial_in(up, UART_LSR) & UART_LSR_THRE))
                        break;
        } while (--count > 0);

        if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
                uart_write_wakeup(port);

        /*
         * With RPM enabled, we have to wait until the FIFO is empty before the
         * HW can go idle. So we get here once again with empty FIFO and disable
         * the interrupt and RPM in __stop_tx()
         */
        if (uart_circ_empty(xmit) && !(up->capabilities & UART_CAP_RPM))
                __stop_tx(up);
}
EXPORT_SYMBOL_GPL(serial8250_tx_chars);

/* Caller holds uart port lock */
unsigned int serial8250_modem_status(struct uart_8250_port *up)
{
        struct uart_port *port = &up->port;
        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 &&
            port->state != NULL) {
                if (status & UART_MSR_TERI)
                        port->icount.rng++;
                if (status & UART_MSR_DDSR)
                        port->icount.dsr++;
                if (status & UART_MSR_DDCD)
                        uart_handle_dcd_change(port, status & UART_MSR_DCD);
                if (status & UART_MSR_DCTS)
                        uart_handle_cts_change(port, status & UART_MSR_CTS);

                wake_up_interruptible(&port->state->port.delta_msr_wait);
        }

        return status;
}
EXPORT_SYMBOL_GPL(serial8250_modem_status);

static bool handle_rx_dma(struct uart_8250_port *up, unsigned int iir)
{
        switch (iir & 0x3f) {
        case UART_IIR_RX_TIMEOUT:
                serial8250_rx_dma_flush(up);
                /* fall-through */
        case UART_IIR_RLSI:
                return true;
        }
        return up->dma->rx_dma(up);
}

/*
 * This handles the interrupt from one port.
 */
int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
{
        unsigned char status;
        unsigned long flags;
        struct uart_8250_port *up = up_to_u8250p(port);

        if (iir & UART_IIR_NO_INT)
                return 0;

        spin_lock_irqsave(&port->lock, flags);

        status = serial_port_in(port, UART_LSR);

        if (status & (UART_LSR_DR | UART_LSR_BI) &&
            iir & UART_IIR_RDI) {
                if (!up->dma || handle_rx_dma(up, iir))
                        status = serial8250_rx_chars(up, status);
        }
        serial8250_modem_status(up);
        if ((!up->dma || up->dma->tx_err) && (status & UART_LSR_THRE))
                serial8250_tx_chars(up);

        spin_unlock_irqrestore(&port->lock, flags);
        return 1;
}
EXPORT_SYMBOL_GPL(serial8250_handle_irq);

static int serial8250_default_handle_irq(struct uart_port *port)
{
        struct uart_8250_port *up = up_to_u8250p(port);
        unsigned int iir;
        int ret;

        serial8250_rpm_get(up);

        iir = serial_port_in(port, UART_IIR);
        ret = serial8250_handle_irq(port, iir);

        serial8250_rpm_put(up);
        return ret;
}

/*
 * Newer 16550 compatible parts such as the SC16C650 & Altera 16550 Soft IP
 * have a programmable TX threshold that triggers the THRE interrupt in
 * the IIR register. In this case, the THRE interrupt indicates the FIFO
 * has space available. Load it up with tx_loadsz bytes.
 */
static int serial8250_tx_threshold_handle_irq(struct uart_port *port)
{
        unsigned long flags;
        unsigned int iir = serial_port_in(port, UART_IIR);

        /* TX Threshold IRQ triggered so load up FIFO */
        if ((iir & UART_IIR_ID) == UART_IIR_THRI) {
                struct uart_8250_port *up = up_to_u8250p(port);

                spin_lock_irqsave(&port->lock, flags);
                serial8250_tx_chars(up);
                spin_unlock_irqrestore(&port->lock, flags);
        }

        iir = serial_port_in(port, UART_IIR);
        return serial8250_handle_irq(port, iir);
}

static unsigned int serial8250_tx_empty(struct uart_port *port)
{
        struct uart_8250_port *up = up_to_u8250p(port);
        unsigned long flags;
        unsigned int lsr;

        serial8250_rpm_get(up);

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

        serial8250_rpm_put(up);

        return (lsr & BOTH_EMPTY) == BOTH_EMPTY ? TIOCSER_TEMT : 0;
}

unsigned int serial8250_do_get_mctrl(struct uart_port *port)
{
        struct uart_8250_port *up = up_to_u8250p(port);
        unsigned int status;
        unsigned int ret;

        serial8250_rpm_get(up);
        status = serial8250_modem_status(up);
        serial8250_rpm_put(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;
}
EXPORT_SYMBOL_GPL(serial8250_do_get_mctrl);

static unsigned int serial8250_get_mctrl(struct uart_port *port)
{
        if (port->get_mctrl)
                return port->get_mctrl(port);
        return serial8250_do_get_mctrl(port);
}

void serial8250_do_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
        struct uart_8250_port *up = up_to_u8250p(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;

        serial8250_out_MCR(up, mcr);
}
EXPORT_SYMBOL_GPL(serial8250_do_set_mctrl);

static void serial8250_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
        if (port->set_mctrl)
                port->set_mctrl(port, mctrl);
        else
                serial8250_do_set_mctrl(port, mctrl);

}

static void serial8250_break_ctl(struct uart_port *port, int break_state)
{
        struct uart_8250_port *up = up_to_u8250p(port);
        unsigned long flags;

        serial8250_rpm_get(up);
        spin_lock_irqsave(&port->lock, flags);
        if (break_state == -1)
                up->lcr |= UART_LCR_SBC;
        else
                up->lcr &= ~UART_LCR_SBC;
        serial_port_out(port, UART_LCR, up->lcr);
        spin_unlock_irqrestore(&port->lock, flags);
        serial8250_rpm_put(up);
}

/*
 *      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. */
        for (;;) {
                status = serial_in(up, UART_LSR);

                up->lsr_saved_flags |= status & LSR_SAVE_FLAGS;

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

        /* Wait up to 1s for flow control if necessary */
        if (up->port.flags & UPF_CONS_FLOW) {
                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 = up_to_u8250p(port);
        unsigned char lsr;
        int status;

        serial8250_rpm_get(up);

        lsr = serial_port_in(port, UART_LSR);

        if (!(lsr & UART_LSR_DR)) {
                status = NO_POLL_CHAR;
                goto out;
        }

        status = serial_port_in(port, UART_RX);
out:
        serial8250_rpm_put(up);
        return status;
}


static void serial8250_put_poll_char(struct uart_port *port,
                         unsigned char c)
{
        unsigned int ier;
        struct uart_8250_port *up = up_to_u8250p(port);

        serial8250_rpm_get(up);
        /*
         *      First save the IER then disable the interrupts
         */
        ier = serial_port_in(port, UART_IER);
        if (up->capabilities & UART_CAP_UUE)
                serial_port_out(port, UART_IER, UART_IER_UUE);
        else
                serial_port_out(port, UART_IER, 0);

        wait_for_xmitr(up, BOTH_EMPTY);
        /*
         *      Send the character out.
         */
        serial_port_out(port, UART_TX, c);

        /*
         *      Finally, wait for transmitter to become empty
         *      and restore the IER
         */
        wait_for_xmitr(up, BOTH_EMPTY);
        serial_port_out(port, UART_IER, ier);
        serial8250_rpm_put(up);
}

#endif /* CONFIG_CONSOLE_POLL */

int serial8250_do_startup(struct uart_port *port)
{
        struct uart_8250_port *up = up_to_u8250p(port);
        unsigned long flags;
        unsigned char lsr, iir;
        int retval;

        if (!port->fifosize)
                port->fifosize = uart_config[port->type].fifo_size;
        if (!up->tx_loadsz)
                up->tx_loadsz = uart_config[port->type].tx_loadsz;
        if (!up->capabilities)
                up->capabilities = uart_config[port->type].flags;
        up->mcr = 0;

        if (port->iotype != up->cur_iotype)
                set_io_from_upio(port);

        serial8250_rpm_get(up);
        if (port->type == PORT_16C950) {
                /* Wake up and initialize UART */
                up->acr = 0;
                serial_port_out(port, UART_LCR, UART_LCR_CONF_MODE_B);
                serial_port_out(port, UART_EFR, UART_EFR_ECB);
                serial_port_out(port, UART_IER, 0);
                serial_port_out(port, UART_LCR, 0);
                serial_icr_write(up, UART_CSR, 0); /* Reset the UART */
                serial_port_out(port, UART_LCR, UART_LCR_CONF_MODE_B);
                serial_port_out(port, UART_EFR, UART_EFR_ECB);
                serial_port_out(port, UART_LCR, 0);
        }

        if (port->type == PORT_DA830) {
                /* Reset the port */
                serial_port_out(port, UART_IER, 0);
                serial_port_out(port, UART_DA830_PWREMU_MGMT, 0);
                mdelay(10);

                /* Enable Tx, Rx and free run mode */
                serial_port_out(port, UART_DA830_PWREMU_MGMT,
                                UART_DA830_PWREMU_MGMT_UTRST |
                                UART_DA830_PWREMU_MGMT_URRST |
                                UART_DA830_PWREMU_MGMT_FREE);
        }

        if (port->type == PORT_NPCM) {
                /*
                 * Nuvoton calls the scratch register 'UART_TOR' (timeout
                 * register). Enable it, and set TIOC (timeout interrupt
                 * comparator) to be 0x20 for correct operation.
                 */
                serial_port_out(port, UART_NPCM_TOR, UART_NPCM_TOIE | 0x20);
        }

#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

        if (port->type == PORT_XR17V35X) {
                /*
                 * First enable access to IER [7:5], ISR [5:4], FCR [5:4],
                 * MCR [7:5] and MSR [7:0]
                 */
                serial_port_out(port, UART_XR_EFR, UART_EFR_ECB);

                /*
                 * Make sure all interrups are masked until initialization is
                 * complete and the FIFOs are cleared
                 */
                serial_port_out(port, UART_IER, 0);
        }

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

        /*
         * Clear the interrupt registers.
         */
        serial_port_in(port, UART_LSR);
        serial_port_in(port, UART_RX);
        serial_port_in(port, UART_IIR);
        serial_port_in(port, UART_MSR);
        if ((port->type == PORT_XR17V35X) || (port->type == PORT_XR17D15X))
                serial_port_in(port, UART_EXAR_INT0);

        /*
         * 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 (!(port->flags & UPF_BUGGY_UART) &&
            (serial_port_in(port, UART_LSR) == 0xff)) {
                pr_info_ratelimited("%s: LSR safety check engaged!\n", port->name);
                retval = -ENODEV;
                goto out;
        }

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

                serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);

                fctr = serial_in(up, UART_FCTR) & ~(UART_FCTR_RX|UART_FCTR_TX);
                serial_port_out(port, UART_FCTR,
                                fctr | UART_FCTR_TRGD | UART_FCTR_RX);
                serial_port_out(port, UART_TRG, UART_TRG_96);
                serial_port_out(port, UART_FCTR,
                                fctr | UART_FCTR_TRGD | UART_FCTR_TX);
                serial_port_out(port, UART_TRG, UART_TRG_96);

                serial_port_out(port, UART_LCR, 0);
        }

        /*
         * For the Altera 16550 variants, set TX threshold trigger level.
         */
        if (((port->type == PORT_ALTR_16550_F32) ||
             (port->type == PORT_ALTR_16550_F64) ||
             (port->type == PORT_ALTR_16550_F128)) && (port->fifosize > 1)) {
                /* Bounds checking of TX threshold (valid 0 to fifosize-2) */
                if ((up->tx_loadsz < 2) || (up->tx_loadsz > port->fifosize)) {
                        pr_err("%s TX FIFO Threshold errors, skipping\n",
                               port->name);
                } else {
                        serial_port_out(port, UART_ALTR_AFR,
                                        UART_ALTR_EN_TXFIFO_LW);
                        serial_port_out(port, UART_ALTR_TX_LOW,
                                        port->fifosize - up->tx_loadsz);
                        port->handle_irq = serial8250_tx_threshold_handle_irq;
                }
        }

        if (port->irq && !(up->port.flags & UPF_NO_THRE_TEST)) {
                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(&port->lock, flags);
                if (up->port.irqflags & IRQF_SHARED)
                        disable_irq_nosync(port->irq);

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

                if (port->irqflags & IRQF_SHARED)
                        enable_irq(port->irq);
                spin_unlock_irqrestore(&port->lock, flags);

                /*
                 * If the interrupt is not reasserted, or we otherwise
                 * don't trust the iir, setup a timer to kick the UART
                 * on a regular basis.
                 */
                if ((!(iir1 & UART_IIR_NO_INT) && (iir & UART_IIR_NO_INT)) ||
                    up->port.flags & UPF_BUG_THRE) {
                        up->bugs |= UART_BUG_THRE;
                }
        }

        retval = up->ops->setup_irq(up);
        if (retval)
                goto out;

        /*
         * Now, initialize the UART
         */
        serial_port_out(port, UART_LCR, UART_LCR_WLEN8);

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

        serial8250_set_mctrl(port, port->mctrl);

        /*
         * Serial over Lan (SoL) hack:
         * Intel 8257x Gigabit ethernet chips have a 16550 emulation, to be
         * used for Serial Over Lan.  Those chips take a longer time than a
         * normal serial device to signalize that a transmission data was
         * queued. Due to that, the above test generally fails. One solution
         * would be to delay the reading of iir. However, this is not
         * reliable, since the timeout is variable. So, let's just don't
         * test if we receive TX irq.  This way, we'll never enable
         * UART_BUG_TXEN.
         */
        if (up->port.quirks & UPQ_NO_TXEN_TEST)
                goto dont_test_tx_en;

        /*
         * Do a quick test to see if we receive an interrupt when we enable
         * the TX irq.
         */
        serial_port_out(port, UART_IER, UART_IER_THRI);
        lsr = serial_port_in(port, UART_LSR);
        iir = serial_port_in(port, UART_IIR);
        serial_port_out(port, 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("%s - enabling bad tx status workarounds\n",
                                 port->name);
                }
        } else {
                up->bugs &= ~UART_BUG_TXEN;
        }

dont_test_tx_en:
        spin_unlock_irqrestore(&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_port_in(port, UART_LSR);
        serial_port_in(port, UART_RX);
        serial_port_in(port, UART_IIR);
        serial_port_in(port, UART_MSR);
        if ((port->type == PORT_XR17V35X) || (port->type == PORT_XR17D15X))
                serial_port_in(port, UART_EXAR_INT0);
        up->lsr_saved_flags = 0;
        up->msr_saved_flags = 0;

        /*
         * Request DMA channels for both RX and TX.
         */
        if (up->dma) {
                retval = serial8250_request_dma(up);
                if (retval) {
                        pr_warn_ratelimited("%s - failed to request DMA\n",
                                            port->name);
                        up->dma = NULL;
                }
        }

        /*
         * Set the IER shadow for rx interrupts but defer actual interrupt
         * enable until after the FIFOs are enabled; otherwise, an already-
         * active sender can swamp the interrupt handler with "too much work".
         */
        up->ier = UART_IER_RLSI | UART_IER_RDI;

        if (port->flags & UPF_FOURPORT) {
                unsigned int icp;
                /*
                 * Enable interrupts on the AST Fourport board
                 */
                icp = (port->iobase & 0xfe0) | 0x01f;
                outb_p(0x80, icp);
                inb_p(icp);
        }
        retval = 0;
out:
        serial8250_rpm_put(up);
        return retval;
}
EXPORT_SYMBOL_GPL(serial8250_do_startup);

static int serial8250_startup(struct uart_port *port)
{
        if (port->startup)
                return port->startup(port);
        return serial8250_do_startup(port);
}

void serial8250_do_shutdown(struct uart_port *port)
{
        struct uart_8250_port *up = up_to_u8250p(port);
        unsigned long flags;

        serial8250_rpm_get(up);
        /*
         * Disable interrupts from this port
         */
        spin_lock_irqsave(&port->lock, flags);
        up->ier = 0;
        serial_port_out(port, UART_IER, 0);
        spin_unlock_irqrestore(&port->lock, flags);

        synchronize_irq(port->irq);

        if (up->dma)
                serial8250_release_dma(up);

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

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

        /*
         * Disable break condition and FIFOs
         */
        serial_port_out(port, UART_LCR,
                        serial_port_in(port, 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.
         */
        serial_port_in(port, UART_RX);
        serial8250_rpm_put(up);

        up->ops->release_irq(up);
}
EXPORT_SYMBOL_GPL(serial8250_do_shutdown);

static void serial8250_shutdown(struct uart_port *port)
{
        if (port->shutdown)
                port->shutdown(port);
        else
                serial8250_do_shutdown(port);
}

/*
 * XR17V35x UARTs have an extra fractional divisor register (DLD)
 * Calculate divisor with extra 4-bit fractional portion
 */
static unsigned int xr17v35x_get_divisor(struct uart_8250_port *up,
                                         unsigned int baud,
                                         unsigned int *frac)
{
        struct uart_port *port = &up->port;
        unsigned int quot_16;

        quot_16 = DIV_ROUND_CLOSEST(port->uartclk, baud);
        *frac = quot_16 & 0x0f;

        return quot_16 >> 4;
}

/* Nuvoton NPCM UARTs have a custom divisor calculation */
static unsigned int npcm_get_divisor(struct uart_8250_port *up,
                unsigned int baud)
{
        struct uart_port *port = &up->port;

        return DIV_ROUND_CLOSEST(port->uartclk, 16 * baud + 2) - 2;
}

static unsigned int serial8250_do_get_divisor(struct uart_port *port,
                                              unsigned int baud,
                                              unsigned int *frac)
{
        struct uart_8250_port *up = up_to_u8250p(port);
        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 if (up->port.type == PORT_XR17V35X)
                quot = xr17v35x_get_divisor(up, baud, frac);
        else if (up->port.type == PORT_NPCM)
                quot = npcm_get_divisor(up, baud);
        else
                quot = uart_get_divisor(port, baud);

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

        return quot;
}

static unsigned int serial8250_get_divisor(struct uart_port *port,
                                           unsigned int baud,
                                           unsigned int *frac)
{
        if (port->get_divisor)
                return port->get_divisor(port, baud, frac);

        return serial8250_do_get_divisor(port, baud, frac);
}

static unsigned char serial8250_compute_lcr(struct uart_8250_port *up,
                                            tcflag_t c_cflag)
{
        unsigned char cval;

        switch (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 (c_cflag & CSTOPB)
                cval |= UART_LCR_STOP;
        if (c_cflag & PARENB) {
                cval |= UART_LCR_PARITY;
                if (up->bugs & UART_BUG_PARITY)
                        up->fifo_bug = true;
        }
        if (!(c_cflag & PARODD))
                cval |= UART_LCR_EPAR;
#ifdef CMSPAR
        if (c_cflag & CMSPAR)
                cval |= UART_LCR_SPAR;
#endif

        return cval;
}

void serial8250_do_set_divisor(struct uart_port *port, unsigned int baud,
                               unsigned int quot, unsigned int quot_frac)
{
        struct uart_8250_port *up = up_to_u8250p(port);

        /* Workaround to enable 115200 baud on OMAP1510 internal ports */
        if (is_omap1510_8250(up)) {
                if (baud == 115200) {
                        quot = 1;
                        serial_port_out(port, UART_OMAP_OSC_12M_SEL, 1);
                } else
                        serial_port_out(port, UART_OMAP_OSC_12M_SEL, 0);
        }

        /*
         * For NatSemi, switch to bank 2 not bank 1, to avoid resetting EXCR2,
         * otherwise just set DLAB
         */
        if (up->capabilities & UART_NATSEMI)
                serial_port_out(port, UART_LCR, 0xe0);
        else
                serial_port_out(port, UART_LCR, up->lcr | UART_LCR_DLAB);

        serial_dl_write(up, quot);

        /* XR17V35x UARTs have an extra fractional divisor register (DLD) */
        if (up->port.type == PORT_XR17V35X) {
                /* Preserve bits not related to baudrate; DLD[7:4]. */
                quot_frac |= serial_port_in(port, 0x2) & 0xf0;
                serial_port_out(port, 0x2, quot_frac);
        }
}
EXPORT_SYMBOL_GPL(serial8250_do_set_divisor);

static void serial8250_set_divisor(struct uart_port *port, unsigned int baud,
                                   unsigned int quot, unsigned int quot_frac)
{
        if (port->set_divisor)
                port->set_divisor(port, baud, quot, quot_frac);
        else
                serial8250_do_set_divisor(port, baud, quot, quot_frac);
}

static unsigned int serial8250_get_baud_rate(struct uart_port *port,
                                             struct ktermios *termios,
                                             struct ktermios *old)
{
        /*
         * Ask the core to calculate the divisor for us.
         * Allow 1% tolerance at the upper limit so uart clks marginally
         * slower than nominal still match standard baud rates without
         * causing transmission errors.
         */
        return uart_get_baud_rate(port, termios, old,
                                  port->uartclk / 16 / UART_DIV_MAX,
                                  port->uartclk);
}

void
serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
                          struct ktermios *old)
{
        struct uart_8250_port *up = up_to_u8250p(port);
        unsigned char cval;
        unsigned long flags;
        unsigned int baud, quot, frac = 0;

        if (up->capabilities & UART_CAP_MINI) {
                termios->c_cflag &= ~(CSTOPB | PARENB | PARODD | CMSPAR);
                if ((termios->c_cflag & CSIZE) == CS5 ||
                    (termios->c_cflag & CSIZE) == CS6)
                        termios->c_cflag = (termios->c_cflag & ~CSIZE) | CS7;
        }
        cval = serial8250_compute_lcr(up, termios->c_cflag);

        baud = serial8250_get_baud_rate(port, termios, old);
        quot = serial8250_get_divisor(port, baud, &frac);

        /*
         * Ok, we're now changing the port state.  Do it with
         * interrupts disabled.
         */
        serial8250_rpm_get(up);
        spin_lock_irqsave(&port->lock, flags);

        up->lcr = cval;                                 /* Save computed LCR */

        if (up->capabilities & UART_CAP_FIFO && port->fifosize > 1) {
                /* NOTE: If fifo_bug is not set, a user can set RX_trigger. */
                if ((baud < 2400 && !up->dma) || up->fifo_bug) {
                        up->fcr &= ~UART_FCR_TRIGGER_MASK;
                        up->fcr |= UART_FCR_TRIGGER_1;
                }
        }

        /*
         * 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.
         */
        if (up->capabilities & UART_CAP_AFE) {
                up->mcr &= ~UART_MCR_AFE;
                if (termios->c_cflag & CRTSCTS)
                        up->mcr |= UART_MCR_AFE;
        }

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

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

        /*
         * Characteres to ignore
         */
        port->ignore_status_mask = 0;
        if (termios->c_iflag & IGNPAR)
                port->ignore_status_mask |= UART_LSR_PE | UART_LSR_FE;
        if (termios->c_iflag & IGNBRK) {
                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)
                        port->ignore_status_mask |= UART_LSR_OE;
        }

        /*
         * ignore all characters if CREAD is not set
         */
        if ((termios->c_cflag & CREAD) == 0)
                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;
        if (up->capabilities & UART_CAP_RTOIE)
                up->ier |= UART_IER_RTOIE;

        serial_port_out(port, 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_port_out(port, UART_LCR, UART_LCR_CONF_MODE_B);
                if (port->flags & UPF_EXAR_EFR)
                        serial_port_out(port, UART_XR_EFR, efr);
                else
                        serial_port_out(port, UART_EFR, efr);
        }

        serial8250_set_divisor(port, baud, quot, frac);

        /*
         * 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 (port->type == PORT_16750)
                serial_port_out(port, UART_FCR, up->fcr);

        serial_port_out(port, UART_LCR, up->lcr);       /* reset DLAB */
        if (port->type != PORT_16750) {
                /* emulated UARTs (Lucent Venus 167x) need two steps */
                if (up->fcr & UART_FCR_ENABLE_FIFO)
                        serial_port_out(port, UART_FCR, UART_FCR_ENABLE_FIFO);
                serial_port_out(port, UART_FCR, up->fcr);       /* set fcr */
        }
        serial8250_set_mctrl(port, port->mctrl);
        spin_unlock_irqrestore(&port->lock, flags);
        serial8250_rpm_put(up);

        /* Don't rewrite B0 */
        if (tty_termios_baud_rate(termios))
                tty_termios_encode_baud_rate(termios, baud, baud);
}
EXPORT_SYMBOL(serial8250_do_set_termios);

static void
serial8250_set_termios(struct uart_port *port, struct ktermios *termios,
                       struct ktermios *old)
{
        if (port->set_termios)
                port->set_termios(port, termios, old);
        else
                serial8250_do_set_termios(port, termios, old);
}

void serial8250_do_set_ldisc(struct uart_port *port, struct ktermios *termios)
{
        if (termios->c_line == N_PPS) {
                port->flags |= UPF_HARDPPS_CD;
                spin_lock_irq(&port->lock);
                serial8250_enable_ms(port);
                spin_unlock_irq(&port->lock);
        } else {
                port->flags &= ~UPF_HARDPPS_CD;
                if (!UART_ENABLE_MS(port, termios->c_cflag)) {
                        spin_lock_irq(&port->lock);
                        serial8250_disable_ms(port);
                        spin_unlock_irq(&port->lock);
                }
        }
}
EXPORT_SYMBOL_GPL(serial8250_do_set_ldisc);

static void
serial8250_set_ldisc(struct uart_port *port, struct ktermios *termios)
{
        if (port->set_ldisc)
                port->set_ldisc(port, termios);
        else
                serial8250_do_set_ldisc(port, termios);
}

void serial8250_do_pm(struct uart_port *port, unsigned int state,
                      unsigned int oldstate)
{
        struct uart_8250_port *p = up_to_u8250p(port);

        serial8250_set_sleep(p, state != 0);
}
EXPORT_SYMBOL(serial8250_do_pm);

static void
serial8250_pm(struct uart_port *port, unsigned int state,
              unsigned int oldstate)
{
        if (port->pm)
                port->pm(port, state, oldstate);
        else
                serial8250_do_pm(port, state, oldstate);
}

static unsigned int serial8250_port_size(struct uart_8250_port *pt)
{
        if (pt->port.mapsize)
                return pt->port.mapsize;
        if (pt->port.iotype == UPIO_AU) {
                if (pt->port.type == PORT_RT2880)
                        return 0x100;
                return 0x1000;
        }
        if (is_omap1_8250(pt))
                return 0x16 << pt->port.regshift;

        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);
        struct uart_port *port = &up->port;
        int ret = 0;

        switch (port->iotype) {
        case UPIO_AU:
        case UPIO_TSI:
        case UPIO_MEM32:
        case UPIO_MEM32BE:
        case UPIO_MEM16:
        case UPIO_MEM:
                if (!port->mapbase)
                        break;

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

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

        case UPIO_HUB6:
        case UPIO_PORT:
                if (!request_region(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);
        struct uart_port *port = &up->port;

        switch (port->iotype) {
        case UPIO_AU:
        case UPIO_TSI:
        case UPIO_MEM32:
        case UPIO_MEM32BE:
        case UPIO_MEM16:
        case UPIO_MEM:
                if (!port->mapbase)
                        break;

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

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

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

static void serial8250_release_port(struct uart_port *port)
{
        struct uart_8250_port *up = up_to_u8250p(port);

        serial8250_release_std_resource(up);
}

static int serial8250_request_port(struct uart_port *port)
{
        struct uart_8250_port *up = up_to_u8250p(port);

        return serial8250_request_std_resource(up);
}

static int fcr_get_rxtrig_bytes(struct uart_8250_port *up)
{
        const struct serial8250_config *conf_type = &uart_config[up->port.type];
        unsigned char bytes;

        bytes = conf_type->rxtrig_bytes[UART_FCR_R_TRIG_BITS(up->fcr)];

        return bytes ? bytes : -EOPNOTSUPP;
}

static int bytes_to_fcr_rxtrig(struct uart_8250_port *up, unsigned char bytes)
{
        const struct serial8250_config *conf_type = &uart_config[up->port.type];
        int i;

        if (!conf_type->rxtrig_bytes[UART_FCR_R_TRIG_BITS(UART_FCR_R_TRIG_00)])
                return -EOPNOTSUPP;

        for (i = 1; i < UART_FCR_R_TRIG_MAX_STATE; i++) {
                if (bytes < conf_type->rxtrig_bytes[i])
                        /* Use the nearest lower value */
                        return (--i) << UART_FCR_R_TRIG_SHIFT;
        }

        return UART_FCR_R_TRIG_11;
}

static int do_get_rxtrig(struct tty_port *port)
{
        struct uart_state *state = container_of(port, struct uart_state, port);
        struct uart_port *uport = state->uart_port;
        struct uart_8250_port *up = up_to_u8250p(uport);

        if (!(up->capabilities & UART_CAP_FIFO) || uport->fifosize <= 1)
                return -EINVAL;

        return fcr_get_rxtrig_bytes(up);
}

static int do_serial8250_get_rxtrig(struct tty_port *port)
{
        int rxtrig_bytes;

        mutex_lock(&port->mutex);
        rxtrig_bytes = do_get_rxtrig(port);
        mutex_unlock(&port->mutex);

        return rxtrig_bytes;
}

static ssize_t serial8250_get_attr_rx_trig_bytes(struct device *dev,
        struct device_attribute *attr, char *buf)
{
        struct tty_port *port = dev_get_drvdata(dev);
        int rxtrig_bytes;

        rxtrig_bytes = do_serial8250_get_rxtrig(port);
        if (rxtrig_bytes < 0)
                return rxtrig_bytes;

        return snprintf(buf, PAGE_SIZE, "%d\n", rxtrig_bytes);
}

static int do_set_rxtrig(struct tty_port *port, unsigned char bytes)
{
        struct uart_state *state = container_of(port, struct uart_state, port);
        struct uart_port *uport = state->uart_port;
        struct uart_8250_port *up = up_to_u8250p(uport);