/*
 * Driver for Motorola/Freescale IMX serial ports
 *
 * Based on drivers/char/serial.c, by Linus Torvalds, Theodore Ts'o.
 *
 * Author: Sascha Hauer <sascha@saschahauer.de>
 * Copyright (C) 2004 Pengutronix
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

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

#include <linux/module.h>
#include <linux/ioport.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/sysrq.h>
#include <linux/platform_device.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/serial_core.h>
#include <linux/serial.h>
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/rational.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/io.h>
#include <linux/dma-mapping.h>

#include <asm/irq.h>
#include <linux/platform_data/serial-imx.h>
#include <linux/platform_data/dma-imx.h>

/* Register definitions */
#define URXD0 0x0  /* Receiver Register */
#define URTX0 0x40 /* Transmitter Register */
#define UCR1  0x80 /* Control Register 1 */
#define UCR2  0x84 /* Control Register 2 */
#define UCR3  0x88 /* Control Register 3 */
#define UCR4  0x8c /* Control Register 4 */
#define UFCR  0x90 /* FIFO Control Register */
#define USR1  0x94 /* Status Register 1 */
#define USR2  0x98 /* Status Register 2 */
#define UESC  0x9c /* Escape Character Register */
#define UTIM  0xa0 /* Escape Timer Register */
#define UBIR  0xa4 /* BRM Incremental Register */
#define UBMR  0xa8 /* BRM Modulator Register */
#define UBRC  0xac /* Baud Rate Count Register */
#define IMX21_ONEMS 0xb0 /* One Millisecond register */
#define IMX1_UTS 0xd0 /* UART Test Register on i.mx1 */
#define IMX21_UTS 0xb4 /* UART Test Register on all other i.mx*/

/* UART Control Register Bit Fields.*/
#define URXD_DUMMY_READ (1<<16)
#define URXD_CHARRDY    (1<<15)
#define URXD_ERR        (1<<14)
#define URXD_OVRRUN     (1<<13)
#define URXD_FRMERR     (1<<12)
#define URXD_BRK        (1<<11)
#define URXD_PRERR      (1<<10)
#define URXD_RX_DATA    (0xFF<<0)
#define UCR1_ADEN       (1<<15) /* Auto detect interrupt */
#define UCR1_ADBR       (1<<14) /* Auto detect baud rate */
#define UCR1_TRDYEN     (1<<13) /* Transmitter ready interrupt enable */
#define UCR1_IDEN       (1<<12) /* Idle condition interrupt */
#define UCR1_ICD_REG(x) (((x) & 3) << 10) /* idle condition detect */
#define UCR1_RRDYEN     (1<<9)  /* Recv ready interrupt enable */
#define UCR1_RDMAEN     (1<<8)  /* Recv ready DMA enable */
#define UCR1_IREN       (1<<7)  /* Infrared interface enable */
#define UCR1_TXMPTYEN   (1<<6)  /* Transimitter empty interrupt enable */
#define UCR1_RTSDEN     (1<<5)  /* RTS delta interrupt enable */
#define UCR1_SNDBRK     (1<<4)  /* Send break */
#define UCR1_TDMAEN     (1<<3)  /* Transmitter ready DMA enable */
#define IMX1_UCR1_UARTCLKEN (1<<2) /* UART clock enabled, i.mx1 only */
#define UCR1_ATDMAEN    (1<<2)  /* Aging DMA Timer Enable */
#define UCR1_DOZE       (1<<1)  /* Doze */
#define UCR1_UARTEN     (1<<0)  /* UART enabled */
#define UCR2_ESCI       (1<<15) /* Escape seq interrupt enable */
#define UCR2_IRTS       (1<<14) /* Ignore RTS pin */
#define UCR2_CTSC       (1<<13) /* CTS pin control */
#define UCR2_CTS        (1<<12) /* Clear to send */
#define UCR2_ESCEN      (1<<11) /* Escape enable */
#define UCR2_PREN       (1<<8)  /* Parity enable */
#define UCR2_PROE       (1<<7)  /* Parity odd/even */
#define UCR2_STPB       (1<<6)  /* Stop */
#define UCR2_WS         (1<<5)  /* Word size */
#define UCR2_RTSEN      (1<<4)  /* Request to send interrupt enable */
#define UCR2_ATEN       (1<<3)  /* Aging Timer Enable */
#define UCR2_TXEN       (1<<2)  /* Transmitter enabled */
#define UCR2_RXEN       (1<<1)  /* Receiver enabled */
#define UCR2_SRST       (1<<0)  /* SW reset */
#define UCR3_DTREN      (1<<13) /* DTR interrupt enable */
#define UCR3_PARERREN   (1<<12) /* Parity enable */
#define UCR3_FRAERREN   (1<<11) /* Frame error interrupt enable */
#define UCR3_DSR        (1<<10) /* Data set ready */
#define UCR3_DCD        (1<<9)  /* Data carrier detect */
#define UCR3_RI         (1<<8)  /* Ring indicator */
#define UCR3_ADNIMP     (1<<7)  /* Autobaud Detection Not Improved */
#define UCR3_RXDSEN     (1<<6)  /* Receive status interrupt enable */
#define UCR3_AIRINTEN   (1<<5)  /* Async IR wake interrupt enable */
#define UCR3_AWAKEN     (1<<4)  /* Async wake interrupt enable */
#define IMX21_UCR3_RXDMUXSEL    (1<<2)  /* RXD Muxed Input Select */
#define UCR3_INVT       (1<<1)  /* Inverted Infrared transmission */
#define UCR3_BPEN       (1<<0)  /* Preset registers enable */
#define UCR4_CTSTL_SHF  10      /* CTS trigger level shift */
#define UCR4_CTSTL_MASK 0x3F    /* CTS trigger is 6 bits wide */
#define UCR4_INVR       (1<<9)  /* Inverted infrared reception */
#define UCR4_ENIRI      (1<<8)  /* Serial infrared interrupt enable */
#define UCR4_WKEN       (1<<7)  /* Wake interrupt enable */
#define UCR4_REF16      (1<<6)  /* Ref freq 16 MHz */
#define UCR4_IDDMAEN    (1<<6)  /* DMA IDLE Condition Detected */
#define UCR4_IRSC       (1<<5)  /* IR special case */
#define UCR4_TCEN       (1<<3)  /* Transmit complete interrupt enable */
#define UCR4_BKEN       (1<<2)  /* Break condition interrupt enable */
#define UCR4_OREN       (1<<1)  /* Receiver overrun interrupt enable */
#define UCR4_DREN       (1<<0)  /* Recv data ready interrupt enable */
#define UFCR_RXTL_SHF   0       /* Receiver trigger level shift */
#define UFCR_DCEDTE     (1<<6)  /* DCE/DTE mode select */
#define UFCR_RFDIV      (7<<7)  /* Reference freq divider mask */
#define UFCR_RFDIV_REG(x)       (((x) < 7 ? 6 - (x) : 6) << 7)
#define UFCR_TXTL_SHF   10      /* Transmitter trigger level shift */
#define USR1_PARITYERR  (1<<15) /* Parity error interrupt flag */
#define USR1_RTSS       (1<<14) /* RTS pin status */
#define USR1_TRDY       (1<<13) /* Transmitter ready interrupt/dma flag */
#define USR1_RTSD       (1<<12) /* RTS delta */
#define USR1_ESCF       (1<<11) /* Escape seq interrupt flag */
#define USR1_FRAMERR    (1<<10) /* Frame error interrupt flag */
#define USR1_RRDY       (1<<9)   /* Receiver ready interrupt/dma flag */
#define USR1_TIMEOUT    (1<<7)   /* Receive timeout interrupt status */
#define USR1_RXDS        (1<<6)  /* Receiver idle interrupt flag */
#define USR1_AIRINT      (1<<5)  /* Async IR wake interrupt flag */
#define USR1_AWAKE       (1<<4)  /* Aysnc wake interrupt flag */
#define USR2_ADET        (1<<15) /* Auto baud rate detect complete */
#define USR2_TXFE        (1<<14) /* Transmit buffer FIFO empty */
#define USR2_DTRF        (1<<13) /* DTR edge interrupt flag */
#define USR2_IDLE        (1<<12) /* Idle condition */
#define USR2_IRINT       (1<<8)  /* Serial infrared interrupt flag */
#define USR2_WAKE        (1<<7)  /* Wake */
#define USR2_RTSF        (1<<4)  /* RTS edge interrupt flag */
#define USR2_TXDC        (1<<3)  /* Transmitter complete */
#define USR2_BRCD        (1<<2)  /* Break condition */
#define USR2_ORE        (1<<1)   /* Overrun error */
#define USR2_RDR        (1<<0)   /* Recv data ready */
#define UTS_FRCPERR     (1<<13) /* Force parity error */
#define UTS_LOOP        (1<<12)  /* Loop tx and rx */
#define UTS_TXEMPTY      (1<<6)  /* TxFIFO empty */
#define UTS_RXEMPTY      (1<<5)  /* RxFIFO empty */
#define UTS_TXFULL       (1<<4)  /* TxFIFO full */
#define UTS_RXFULL       (1<<3)  /* RxFIFO full */
#define UTS_SOFTRST      (1<<0)  /* Software reset */

/* We've been assigned a range on the "Low-density serial ports" major */
#define SERIAL_IMX_MAJOR        207
#define MINOR_START             16
#define DEV_NAME                "ttymxc"

/*
 * This determines how often we check the modem status signals
 * for any change.  They generally aren't connected to an IRQ
 * so we have to poll them.  We also check immediately before
 * filling the TX fifo incase CTS has been dropped.
 */
#define MCTRL_TIMEOUT   (250*HZ/1000)

#define DRIVER_NAME "IMX-uart"

#define UART_NR 8

/* i.MX21 type uart runs on all i.mx except i.MX1 and i.MX6q */
enum imx_uart_type {
        IMX1_UART,
        IMX21_UART,
        IMX6Q_UART,
};

/* device type dependent stuff */
struct imx_uart_data {
        unsigned uts_reg;
        enum imx_uart_type devtype;
};

struct imx_port {
        struct uart_port        port;
        struct timer_list       timer;
        unsigned int            old_status;
        unsigned int            have_rtscts:1;
        unsigned int            dte_mode:1;
        unsigned int            irda_inv_rx:1;
        unsigned int            irda_inv_tx:1;
        unsigned short          trcv_delay; /* transceiver delay */
        struct clk              *clk_ipg;
        struct clk              *clk_per;
        const struct imx_uart_data *devdata;

        /* DMA fields */
        unsigned int            dma_is_inited:1;
        unsigned int            dma_is_enabled:1;
        unsigned int            dma_is_rxing:1;
        unsigned int            dma_is_txing:1;
        struct dma_chan         *dma_chan_rx, *dma_chan_tx;
        struct scatterlist      rx_sgl, tx_sgl[2];
        void                    *rx_buf;
        unsigned int            tx_bytes;
        unsigned int            dma_tx_nents;
        wait_queue_head_t       dma_wait;
};

struct imx_port_ucrs {
        unsigned int    ucr1;
        unsigned int    ucr2;
        unsigned int    ucr3;
};

static struct imx_uart_data imx_uart_devdata[] = {
        [IMX1_UART] = {
                .uts_reg = IMX1_UTS,
                .devtype = IMX1_UART,
        },
        [IMX21_UART] = {
                .uts_reg = IMX21_UTS,
                .devtype = IMX21_UART,
        },
        [IMX6Q_UART] = {
                .uts_reg = IMX21_UTS,
                .devtype = IMX6Q_UART,
        },
};

static struct platform_device_id imx_uart_devtype[] = {
        {
                .name = "imx1-uart",
                .driver_data = (kernel_ulong_t) &imx_uart_devdata[IMX1_UART],
        }, {
                .name = "imx21-uart",
                .driver_data = (kernel_ulong_t) &imx_uart_devdata[IMX21_UART],
        }, {
                .name = "imx6q-uart",
                .driver_data = (kernel_ulong_t) &imx_uart_devdata[IMX6Q_UART],
        }, {
                /* sentinel */
        }
};
MODULE_DEVICE_TABLE(platform, imx_uart_devtype);

static const struct of_device_id imx_uart_dt_ids[] = {
        { .compatible = "fsl,imx6q-uart", .data = &imx_uart_devdata[IMX6Q_UART], },
        { .compatible = "fsl,imx1-uart", .data = &imx_uart_devdata[IMX1_UART], },
        { .compatible = "fsl,imx21-uart", .data = &imx_uart_devdata[IMX21_UART], },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, imx_uart_dt_ids);

static inline unsigned uts_reg(struct imx_port *sport)
{
        return sport->devdata->uts_reg;
}

static inline int is_imx1_uart(struct imx_port *sport)
{
        return sport->devdata->devtype == IMX1_UART;
}

static inline int is_imx21_uart(struct imx_port *sport)
{
        return sport->devdata->devtype == IMX21_UART;
}

static inline int is_imx6q_uart(struct imx_port *sport)
{
        return sport->devdata->devtype == IMX6Q_UART;
}
/*
 * Save and restore functions for UCR1, UCR2 and UCR3 registers
 */
#if defined(CONFIG_SERIAL_IMX_CONSOLE)
static void imx_port_ucrs_save(struct uart_port *port,
                               struct imx_port_ucrs *ucr)
{
        /* save control registers */
        ucr->ucr1 = readl(port->membase + UCR1);
        ucr->ucr2 = readl(port->membase + UCR2);
        ucr->ucr3 = readl(port->membase + UCR3);
}

static void imx_port_ucrs_restore(struct uart_port *port,
                                  struct imx_port_ucrs *ucr)
{
        /* restore control registers */
        writel(ucr->ucr1, port->membase + UCR1);
        writel(ucr->ucr2, port->membase + UCR2);
        writel(ucr->ucr3, port->membase + UCR3);
}
#endif

/*
 * Handle any change of modem status signal since we were last called.
 */
static void imx_mctrl_check(struct imx_port *sport)
{
        unsigned int status, changed;

        status = sport->port.ops->get_mctrl(&sport->port);
        changed = status ^ sport->old_status;

        if (changed == 0)
                return;

        sport->old_status = status;

        if (changed & TIOCM_RI)
                sport->port.icount.rng++;
        if (changed & TIOCM_DSR)
                sport->port.icount.dsr++;
        if (changed & TIOCM_CAR)
                uart_handle_dcd_change(&sport->port, status & TIOCM_CAR);
        if (changed & TIOCM_CTS)
                uart_handle_cts_change(&sport->port, status & TIOCM_CTS);

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

/*
 * This is our per-port timeout handler, for checking the
 * modem status signals.
 */
static void imx_timeout(unsigned long data)
{
        struct imx_port *sport = (struct imx_port *)data;
        unsigned long flags;

        if (sport->port.state) {
                spin_lock_irqsave(&sport->port.lock, flags);
                imx_mctrl_check(sport);
                spin_unlock_irqrestore(&sport->port.lock, flags);

                mod_timer(&sport->timer, jiffies + MCTRL_TIMEOUT);
        }
}

/*
 * interrupts disabled on entry
 */
static void imx_stop_tx(struct uart_port *port)
{
        struct imx_port *sport = (struct imx_port *)port;
        unsigned long temp;

        /*
         * We are maybe in the SMP context, so if the DMA TX thread is running
         * on other cpu, we have to wait for it to finish.
         */
        if (sport->dma_is_enabled && sport->dma_is_txing)
                return;

        temp = readl(port->membase + UCR1);
        writel(temp & ~UCR1_TXMPTYEN, port->membase + UCR1);

        /* in rs485 mode disable transmitter if shifter is empty */
        if (port->rs485.flags & SER_RS485_ENABLED &&
            readl(port->membase + USR2) & USR2_TXDC) {
                temp = readl(port->membase + UCR2);
                if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND)
                        temp &= ~UCR2_CTS;
                else
                        temp |= UCR2_CTS;
                writel(temp, port->membase + UCR2);

                temp = readl(port->membase + UCR4);
                temp &= ~UCR4_TCEN;
                writel(temp, port->membase + UCR4);
        }
}

/*
 * interrupts disabled on entry
 */
static void imx_stop_rx(struct uart_port *port)
{
        struct imx_port *sport = (struct imx_port *)port;
        unsigned long temp;

        if (sport->dma_is_enabled && sport->dma_is_rxing) {
                if (sport->port.suspended) {
                        dmaengine_terminate_all(sport->dma_chan_rx);
                        sport->dma_is_rxing = 0;
                } else {
                        return;
                }
        }

        temp = readl(sport->port.membase + UCR2);
        writel(temp & ~UCR2_RXEN, sport->port.membase + UCR2);

        /* disable the `Receiver Ready Interrrupt` */
        temp = readl(sport->port.membase + UCR1);
        writel(temp & ~UCR1_RRDYEN, sport->port.membase + UCR1);
}

/*
 * Set the modem control timer to fire immediately.
 */
static void imx_enable_ms(struct uart_port *port)
{
        struct imx_port *sport = (struct imx_port *)port;

        mod_timer(&sport->timer, jiffies);
}

static void imx_dma_tx(struct imx_port *sport);
static inline void imx_transmit_buffer(struct imx_port *sport)
{
        struct circ_buf *xmit = &sport->port.state->xmit;
        unsigned long temp;

        if (sport->port.x_char) {
                /* Send next char */
                writel(sport->port.x_char, sport->port.membase + URTX0);
                sport->port.icount.tx++;
                sport->port.x_char = 0;
                return;
        }

        if (uart_circ_empty(xmit) || uart_tx_stopped(&sport->port)) {
                imx_stop_tx(&sport->port);
                return;
        }

        if (sport->dma_is_enabled) {
                /*
                 * We've just sent a X-char Ensure the TX DMA is enabled
                 * and the TX IRQ is disabled.
                 **/
                temp = readl(sport->port.membase + UCR1);
                temp &= ~UCR1_TXMPTYEN;
                if (sport->dma_is_txing) {
                        temp |= UCR1_TDMAEN;
                        writel(temp, sport->port.membase + UCR1);
                } else {
                        writel(temp, sport->port.membase + UCR1);
                        imx_dma_tx(sport);
                }
        }

        while (!uart_circ_empty(xmit) &&
               !(readl(sport->port.membase + uts_reg(sport)) & UTS_TXFULL)) {
                /* send xmit->buf[xmit->tail]
                 * out the port here */
                writel(xmit->buf[xmit->tail], sport->port.membase + URTX0);
                xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
                sport->port.icount.tx++;
        }

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

        if (uart_circ_empty(xmit))
                imx_stop_tx(&sport->port);
}

static void dma_tx_callback(void *data)
{
        struct imx_port *sport = data;
        struct scatterlist *sgl = &sport->tx_sgl[0];
        struct circ_buf *xmit = &sport->port.state->xmit;
        unsigned long flags;
        unsigned long temp;

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

        dma_unmap_sg(sport->port.dev, sgl, sport->dma_tx_nents, DMA_TO_DEVICE);

        temp = readl(sport->port.membase + UCR1);
        temp &= ~UCR1_TDMAEN;
        writel(temp, sport->port.membase + UCR1);

        /* update the stat */
        xmit->tail = (xmit->tail + sport->tx_bytes) & (UART_XMIT_SIZE - 1);
        sport->port.icount.tx += sport->tx_bytes;

        dev_dbg(sport->port.dev, "we finish the TX DMA.\n");

        sport->dma_is_txing = 0;

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

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

        if (waitqueue_active(&sport->dma_wait)) {
                wake_up(&sport->dma_wait);
                dev_dbg(sport->port.dev, "exit in %s.\n", __func__);
                return;
        }

        spin_lock_irqsave(&sport->port.lock, flags);
        if (!uart_circ_empty(xmit) && !uart_tx_stopped(&sport->port))
                imx_dma_tx(sport);
        spin_unlock_irqrestore(&sport->port.lock, flags);
}

static void imx_dma_tx(struct imx_port *sport)
{
        struct circ_buf *xmit = &sport->port.state->xmit;
        struct scatterlist *sgl = sport->tx_sgl;
        struct dma_async_tx_descriptor *desc;
        struct dma_chan *chan = sport->dma_chan_tx;
        struct device *dev = sport->port.dev;
        unsigned long temp;
        int ret;

        if (sport->dma_is_txing)
                return;

        sport->tx_bytes = uart_circ_chars_pending(xmit);

        if (xmit->tail < xmit->head) {
                sport->dma_tx_nents = 1;
                sg_init_one(sgl, xmit->buf + xmit->tail, sport->tx_bytes);
        } else {
                sport->dma_tx_nents = 2;
                sg_init_table(sgl, 2);
                sg_set_buf(sgl, xmit->buf + xmit->tail,
                                UART_XMIT_SIZE - xmit->tail);
                sg_set_buf(sgl + 1, xmit->buf, xmit->head);
        }

        ret = dma_map_sg(dev, sgl, sport->dma_tx_nents, DMA_TO_DEVICE);
        if (ret == 0) {
                dev_err(dev, "DMA mapping error for TX.\n");
                return;
        }
        desc = dmaengine_prep_slave_sg(chan, sgl, sport->dma_tx_nents,
                                        DMA_MEM_TO_DEV, DMA_PREP_INTERRUPT);
        if (!desc) {
                dma_unmap_sg(dev, sgl, sport->dma_tx_nents,
                             DMA_TO_DEVICE);
                dev_err(dev, "We cannot prepare for the TX slave dma!\n");
                return;
        }
        desc->callback = dma_tx_callback;
        desc->callback_param = sport;

        dev_dbg(dev, "TX: prepare to send %lu bytes by DMA.\n",
                        uart_circ_chars_pending(xmit));

        temp = readl(sport->port.membase + UCR1);
        temp |= UCR1_TDMAEN;
        writel(temp, sport->port.membase + UCR1);

        /* fire it */
        sport->dma_is_txing = 1;
        dmaengine_submit(desc);
        dma_async_issue_pending(chan);
        return;
}

/*
 * interrupts disabled on entry
 */
static void imx_start_tx(struct uart_port *port)
{
        struct imx_port *sport = (struct imx_port *)port;
        unsigned long temp;

        if (port->rs485.flags & SER_RS485_ENABLED) {
                /* enable transmitter and shifter empty irq */
                temp = readl(port->membase + UCR2);
                if (port->rs485.flags & SER_RS485_RTS_ON_SEND)
                        temp &= ~UCR2_CTS;
                else
                        temp |= UCR2_CTS;
                writel(temp, port->membase + UCR2);

                temp = readl(port->membase + UCR4);
                temp |= UCR4_TCEN;
                writel(temp, port->membase + UCR4);
        }

        if (!sport->dma_is_enabled) {
                temp = readl(sport->port.membase + UCR1);
                writel(temp | UCR1_TXMPTYEN, sport->port.membase + UCR1);
        }

        if (sport->dma_is_enabled) {
                if (sport->port.x_char) {
                        /* We have X-char to send, so enable TX IRQ and
                         * disable TX DMA to let TX interrupt to send X-char */
                        temp = readl(sport->port.membase + UCR1);
                        temp &= ~UCR1_TDMAEN;
                        temp |= UCR1_TXMPTYEN;
                        writel(temp, sport->port.membase + UCR1);
                        return;
                }

                if (!uart_circ_empty(&port->state->xmit) &&
                    !uart_tx_stopped(port))
                        imx_dma_tx(sport);
                return;
        }
}

static irqreturn_t imx_rtsint(int irq, void *dev_id)
{
        struct imx_port *sport = dev_id;
        unsigned int val;
        unsigned long flags;

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

        writel(USR1_RTSD, sport->port.membase + USR1);
        val = readl(sport->port.membase + USR1) & USR1_RTSS;
        uart_handle_cts_change(&sport->port, !!val);
        wake_up_interruptible(&sport->port.state->port.delta_msr_wait);

        spin_unlock_irqrestore(&sport->port.lock, flags);
        return IRQ_HANDLED;
}

static irqreturn_t imx_txint(int irq, void *dev_id)
{
        struct imx_port *sport = dev_id;
        unsigned long flags;

        spin_lock_irqsave(&sport->port.lock, flags);
        imx_transmit_buffer(sport);
        spin_unlock_irqrestore(&sport->port.lock, flags);
        return IRQ_HANDLED;
}

static irqreturn_t imx_rxint(int irq, void *dev_id)
{
        struct imx_port *sport = dev_id;
        unsigned int rx, flg, ignored = 0;
        struct tty_port *port = &sport->port.state->port;
        unsigned long flags, temp;

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

        while (readl(sport->port.membase + USR2) & USR2_RDR) {
                flg = TTY_NORMAL;
                sport->port.icount.rx++;

                rx = readl(sport->port.membase + URXD0);

                temp = readl(sport->port.membase + USR2);
                if (temp & USR2_BRCD) {
                        writel(USR2_BRCD, sport->port.membase + USR2);
                        if (uart_handle_break(&sport->port))
                                continue;
                }

                if (uart_handle_sysrq_char(&sport->port, (unsigned char)rx))
                        continue;

                if (unlikely(rx & URXD_ERR)) {
                        if (rx & URXD_BRK)
                                sport->port.icount.brk++;
                        else if (rx & URXD_PRERR)
                                sport->port.icount.parity++;
                        else if (rx & URXD_FRMERR)
                                sport->port.icount.frame++;
                        if (rx & URXD_OVRRUN)
                                sport->port.icount.overrun++;

                        if (rx & sport->port.ignore_status_mask) {
                                if (++ignored > 100)
                                        goto out;
                                continue;
                        }

                        rx &= (sport->port.read_status_mask | 0xFF);

                        if (rx & URXD_BRK)
                                flg = TTY_BREAK;
                        else if (rx & URXD_PRERR)
                                flg = TTY_PARITY;
                        else if (rx & URXD_FRMERR)
                                flg = TTY_FRAME;
                        if (rx & URXD_OVRRUN)
                                flg = TTY_OVERRUN;

#ifdef SUPPORT_SYSRQ
                        sport->port.sysrq = 0;
#endif
                }

                if (sport->port.ignore_status_mask & URXD_DUMMY_READ)
                        goto out;

                tty_insert_flip_char(port, rx, flg);
        }

out:
        spin_unlock_irqrestore(&sport->port.lock, flags);
        tty_flip_buffer_push(port);
        return IRQ_HANDLED;
}

static int start_rx_dma(struct imx_port *sport);
/*
 * If the RXFIFO is filled with some data, and then we
 * arise a DMA operation to receive them.
 */
static void imx_dma_rxint(struct imx_port *sport)
{
        unsigned long temp;
        unsigned long flags;

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

        temp = readl(sport->port.membase + USR2);
        if ((temp & USR2_RDR) && !sport->dma_is_rxing) {
                sport->dma_is_rxing = 1;

                /* disable the `Recerver Ready Interrrupt` */
                temp = readl(sport->port.membase + UCR1);
                temp &= ~(UCR1_RRDYEN);
                writel(temp, sport->port.membase + UCR1);

                /* tell the DMA to receive the data. */
                start_rx_dma(sport);
        }

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

static irqreturn_t imx_int(int irq, void *dev_id)
{
        struct imx_port *sport = dev_id;
        unsigned int sts;
        unsigned int sts2;

        sts = readl(sport->port.membase + USR1);
        sts2 = readl(sport->port.membase + USR2);

        if (sts & USR1_RRDY) {
                if (sport->dma_is_enabled)
                        imx_dma_rxint(sport);
                else
                        imx_rxint(irq, dev_id);
        }

        if ((sts & USR1_TRDY &&
             readl(sport->port.membase + UCR1) & UCR1_TXMPTYEN) ||
            (sts2 & USR2_TXDC &&
             readl(sport->port.membase + UCR4) & UCR4_TCEN))
                imx_txint(irq, dev_id);

        if (sts & USR1_RTSD)
                imx_rtsint(irq, dev_id);

        if (sts & USR1_AWAKE)
                writel(USR1_AWAKE, sport->port.membase + USR1);

        if (sts2 & USR2_ORE) {
                dev_err(sport->port.dev, "Rx FIFO overrun\n");
                sport->port.icount.overrun++;
                writel(USR2_ORE, sport->port.membase + USR2);
        }

        return IRQ_HANDLED;
}

/*
 * Return TIOCSER_TEMT when transmitter is not busy.
 */
static unsigned int imx_tx_empty(struct uart_port *port)
{
        struct imx_port *sport = (struct imx_port *)port;
        unsigned int ret;

        ret = (readl(sport->port.membase + USR2) & USR2_TXDC) ?  TIOCSER_TEMT : 0;

        /* If the TX DMA is working, return 0. */
        if (sport->dma_is_enabled && sport->dma_is_txing)
                ret = 0;

        return ret;
}

/*
 * We have a modem side uart, so the meanings of RTS and CTS are inverted.
 */
static unsigned int imx_get_mctrl(struct uart_port *port)
{
        struct imx_port *sport = (struct imx_port *)port;
        unsigned int tmp = TIOCM_DSR | TIOCM_CAR;

        if (readl(sport->port.membase + USR1) & USR1_RTSS)
                tmp |= TIOCM_CTS;

        if (readl(sport->port.membase + UCR2) & UCR2_CTS)
                tmp |= TIOCM_RTS;

        if (readl(sport->port.membase + uts_reg(sport)) & UTS_LOOP)
                tmp |= TIOCM_LOOP;

        return tmp;
}

static void imx_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
        struct imx_port *sport = (struct imx_port *)port;
        unsigned long temp;

        if (!(port->rs485.flags & SER_RS485_ENABLED)) {
                temp = readl(sport->port.membase + UCR2);
                temp &= ~(UCR2_CTS | UCR2_CTSC);
                if (mctrl & TIOCM_RTS)
                        temp |= UCR2_CTS | UCR2_CTSC;
                writel(temp, sport->port.membase + UCR2);
        }

        temp = readl(sport->port.membase + uts_reg(sport)) & ~UTS_LOOP;
        if (mctrl & TIOCM_LOOP)
                temp |= UTS_LOOP;
        writel(temp, sport->port.membase + uts_reg(sport));
}

/*
 * Interrupts always disabled.
 */
static void imx_break_ctl(struct uart_port *port, int break_state)
{
        struct imx_port *sport = (struct imx_port *)port;
        unsigned long flags, temp;

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

        temp = readl(sport->port.membase + UCR1) & ~UCR1_SNDBRK;

        if (break_state != 0)
                temp |= UCR1_SNDBRK;

        writel(temp, sport->port.membase + UCR1);

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

#define TXTL 2 /* reset default */
#define RXTL 1 /* reset default */

static int imx_setup_ufcr(struct imx_port *sport, unsigned int mode)
{
        unsigned int val;

        /* set receiver / transmitter trigger level */
        val = readl(sport->port.membase + UFCR) & (UFCR_RFDIV | UFCR_DCEDTE);
        val |= TXTL << UFCR_TXTL_SHF | RXTL;
        writel(val, sport->port.membase + UFCR);
        return 0;
}

#define RX_BUF_SIZE     (PAGE_SIZE)
static void imx_rx_dma_done(struct imx_port *sport)
{
        unsigned long temp;
        unsigned long flags;

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

        /* Enable this interrupt when the RXFIFO is empty. */
        temp = readl(sport->port.membase + UCR1);
        temp |= UCR1_RRDYEN;
        writel(temp, sport->port.membase + UCR1);

        sport->dma_is_rxing = 0;

        /* Is the shutdown waiting for us? */
        if (waitqueue_active(&sport->dma_wait))
                wake_up(&sport->dma_wait);

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

/*
 * There are three kinds of RX DMA interrupts(such as in the MX6Q):
 *   [1] the RX DMA buffer is full.
 *   [2] the Aging timer expires(wait for 8 bytes long)
 *   [3] the Idle Condition Detect(enabled the UCR4_IDDMAEN).
 *
 * The [2] is trigger when a character was been sitting in the FIFO
 * meanwhile [3] can wait for 32 bytes long when the RX line is
 * on IDLE state and RxFIFO is empty.
 */
static void dma_rx_callback(void *data)
{
        struct imx_port *sport = data;
        struct dma_chan *chan = sport->dma_chan_rx;
        struct scatterlist *sgl = &sport->rx_sgl;
        struct tty_port *port = &sport->port.state->port;
        struct dma_tx_state state;
        enum dma_status status;
        unsigned int count;

        /* unmap it first */
        dma_unmap_sg(sport->port.dev, sgl, 1, DMA_FROM_DEVICE);

        status = dmaengine_tx_status(chan, (dma_cookie_t)0, &state);
        count = RX_BUF_SIZE - state.residue;

        if (readl(sport->port.membase + USR2) & USR2_IDLE) {
                /* In condition [3] the SDMA counted up too early */
                count--;

                writel(USR2_IDLE, sport->port.membase + USR2);
        }

        dev_dbg(sport->port.dev, "We get %d bytes.\n", count);

        if (count) {
                if (!(sport->port.ignore_status_mask & URXD_DUMMY_READ))
                        tty_insert_flip_string(port, sport->rx_buf, count);
                tty_flip_buffer_push(port);

                start_rx_dma(sport);
        } else if (readl(sport->port.membase + USR2) & USR2_RDR) {
                /*
                 * start rx_dma directly once data in RXFIFO, more efficient
                 * than before:
                 *      1. call imx_rx_dma_done to stop dma if no data received
                 *      2. wait next  RDR interrupt to start dma transfer.
                 */
                start_rx_dma(sport);
        } else {
                /*
                 * stop dma to prevent too many IDLE event trigged if no data
                 * in RXFIFO
                 */
                imx_rx_dma_done(sport);
        }
}

static int start_rx_dma(struct imx_port *sport)
{
        struct scatterlist *sgl = &sport->rx_sgl;
        struct dma_chan *chan = sport->dma_chan_rx;
        struct device *dev = sport->port.dev;
        struct dma_async_tx_descriptor *desc;
        int ret;

        sg_init_one(sgl, sport->rx_buf, RX_BUF_SIZE);
        ret = dma_map_sg(dev, sgl, 1, DMA_FROM_DEVICE);
        if (ret == 0) {
                dev_err(dev, "DMA mapping error for RX.\n");
                return -EINVAL;
        }
        desc = dmaengine_prep_slave_sg(chan, sgl, 1, DMA_DEV_TO_MEM,
                                        DMA_PREP_INTERRUPT);
        if (!desc) {
                dma_unmap_sg(dev, sgl, 1, DMA_FROM_DEVICE);
                dev_err(dev, "We cannot prepare for the RX slave dma!\n");
                return -EINVAL;
        }
        desc->callback = dma_rx_callback;
        desc->callback_param = sport;

        dev_dbg(dev, "RX: prepare for the DMA.\n");
        dmaengine_submit(desc);
        dma_async_issue_pending(chan);
        return 0;
}

static void imx_uart_dma_exit(struct imx_port *sport)
{
        if (sport->dma_chan_rx) {
                dma_release_channel(sport->dma_chan_rx);
                sport->dma_chan_rx = NULL;

                kfree(sport->rx_buf);
                sport->rx_buf = NULL;
        }

        if (sport->dma_chan_tx) {
                dma_release_channel(sport->dma_chan_tx);
                sport->dma_chan_tx = NULL;
        }

        sport->dma_is_inited = 0;
}

static int imx_uart_dma_init(struct imx_port *sport)
{
        struct dma_slave_config slave_config = {};
        struct device *dev = sport->port.dev;
        int ret;

        /* Prepare for RX : */
        sport->dma_chan_rx = dma_request_slave_channel(dev, "rx");
        if (!sport->dma_chan_rx) {
                dev_dbg(dev, "cannot get the DMA channel.\n");
                ret = -EINVAL;
                goto err;
        }

        slave_config.direction = DMA_DEV_TO_MEM;
        slave_config.src_addr = sport->port.mapbase + URXD0;
        slave_config.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
        slave_config.src_maxburst = RXTL;
        ret = dmaengine_slave_config(sport->dma_chan_rx, &slave_config);
        if (ret) {
                dev_err(dev, "error in RX dma configuration.\n");
                goto err;
        }

        sport->rx_buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
        if (!sport->rx_buf) {
                ret = -ENOMEM;
                goto err;
        }

        /* Prepare for TX : */
        sport->dma_chan_tx = dma_request_slave_channel(dev, "tx");
        if (!sport->dma_chan_tx) {
                dev_err(dev, "cannot get the TX DMA channel!\n");
                ret = -EINVAL;
                goto err;
        }

        slave_config.direction = DMA_MEM_TO_DEV;
        slave_config.dst_addr = sport->port.mapbase + URTX0;
        slave_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
        slave_config.dst_maxburst = TXTL;
        ret = dmaengine_slave_config(sport->dma_chan_tx, &slave_config);
        if (ret) {
                dev_err(dev, "error in TX dma configuration.");
                goto err;
        }

        sport->dma_is_inited = 1;

        return 0;
err:
        imx_uart_dma_exit(sport);
        return ret;
}

static void imx_enable_dma(struct imx_port *sport)
{
        unsigned long temp;

        init_waitqueue_head(&sport->dma_wait);

        /* set UCR1 */
        temp = readl(sport->port.membase + UCR1);
        temp |= UCR1_RDMAEN | UCR1_TDMAEN | UCR1_ATDMAEN |
                /* wait for 32 idle frames for IDDMA interrupt */
                UCR1_ICD_REG(3);
        writel(temp, sport->port.membase + UCR1);

        /* set UCR4 */
        temp = readl(sport->port.membase + UCR4);
        temp |= UCR4_IDDMAEN;
        writel(temp, sport->port.membase + UCR4);

        sport->dma_is_enabled = 1;
}

static void imx_disable_dma(struct imx_port *sport)
{
        unsigned long temp;

        /* clear UCR1 */
        temp = readl(sport->port.membase + UCR1);
        temp &= ~(UCR1_RDMAEN | UCR1_TDMAEN | UCR1_ATDMAEN);
        writel(temp, sport->port.membase + UCR1);

        /* clear UCR2 */
        temp = readl(sport->port.membase + UCR2);
        temp &= ~(UCR2_CTSC | UCR2_CTS);
        writel(temp, sport->port.membase + UCR2);

        /* clear UCR4 */
        temp = readl(sport->port.membase + UCR4);
        temp &= ~UCR4_IDDMAEN;
        writel(temp, sport->port.membase + UCR4);

        sport->dma_is_enabled = 0;
}

/* half the RX buffer size */
#define CTSTL 16

static int imx_startup(struct uart_port *port)
{
        struct imx_port *sport = (struct imx_port *)port;
        int retval, i;
        unsigned long flags, temp;

        retval = clk_prepare_enable(sport->clk_per);
        if (retval)
                return retval;
        retval = clk_prepare_enable(sport->clk_ipg);
        if (retval) {
                clk_disable_unprepare(sport->clk_per);
                return retval;
        }

        imx_setup_ufcr(sport, 0);

        /* disable the DREN bit (Data Ready interrupt enable) before
         * requesting IRQs
         */
        temp = readl(sport->port.membase + UCR4);

        /* set the trigger level for CTS */
        temp &= ~(UCR4_CTSTL_MASK << UCR4_CTSTL_SHF);
        temp |= CTSTL << UCR4_CTSTL_SHF;

        writel(temp & ~UCR4_DREN, sport->port.membase + UCR4);

        /* Reset fifo's and state machines */
        i = 100;

        temp = readl(sport->port.membase + UCR2);
        temp &= ~UCR2_SRST;
        writel(temp, sport->port.membase + UCR2);

        while (!(readl(sport->port.membase + UCR2) & UCR2_SRST) && (--i > 0))
                udelay(1);

        /* Can we enable the DMA support? */
        if (is_imx6q_uart(sport) && !uart_console(port) &&
            !sport->dma_is_inited)
                imx_uart_dma_init(sport);

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

        /*
         * Finally, clear and enable interrupts
         */
        writel(USR1_RTSD, sport->port.membase + USR1);
        writel(USR2_ORE, sport->port.membase + USR2);

        if (sport->dma_is_inited && !sport->dma_is_enabled)
                imx_enable_dma(sport);

        temp = readl(sport->port.membase + UCR1);
        temp |= UCR1_RRDYEN | UCR1_RTSDEN | UCR1_UARTEN;

        writel(temp, sport->port.membase + UCR1);

        temp = readl(sport->port.membase + UCR4);
        temp |= UCR4_OREN;
        writel(temp, sport->port.membase + UCR4);

        temp = readl(sport->port.membase + UCR2);
        temp |= (UCR2_RXEN | UCR2_TXEN);
        if (!sport->have_rtscts)
                temp |= UCR2_IRTS;
        writel(temp, sport->port.membase + UCR2);

        if (!is_imx1_uart(sport)) {
                temp = readl(sport->port.membase + UCR3);
                temp |= IMX21_UCR3_RXDMUXSEL | UCR3_ADNIMP;
                writel(temp, sport->port.membase + UCR3);
        }

        /*
         * Enable modem status interrupts
         */
        imx_enable_ms(&sport->port);
        spin_unlock_irqrestore(&sport->port.lock, flags);

        return 0;
}

static void imx_shutdown(struct uart_port *port)
{
        struct imx_port *sport = (struct imx_port *)port;
        unsigned long temp;
        unsigned long flags;

        if (sport->dma_is_enabled) {
                int ret;

                /* We have to wait for the DMA to finish. */
                ret = wait_event_interruptible(sport->dma_wait,
                        !sport->dma_is_rxing && !sport->dma_is_txing);
                if (ret != 0) {
                        sport->dma_is_rxing = 0;
                        sport->dma_is_txing = 0;
                        dmaengine_terminate_all(sport->dma_chan_tx);
                        dmaengine_terminate_all(sport->dma_chan_rx);
                }
                spin_lock_irqsave(&sport->port.lock, flags);
                imx_stop_tx(port);
                imx_stop_rx(port);
                imx_disable_dma(sport);
                spin_unlock_irqrestore(&sport->port.lock, flags);
                imx_uart_dma_exit(sport);
        }

        spin_lock_irqsave(&sport->port.lock, flags);
        temp = readl(sport->port.membase + UCR2);
        temp &= ~(UCR2_TXEN);
        writel(temp, sport->port.membase + UCR2);
        spin_unlock_irqrestore(&sport->port.lock, flags);

        /*
         * Stop our timer.
         */
        del_timer_sync(&sport->timer);

        /*
         * Disable all interrupts, port and break condition.
         */

        spin_lock_irqsave(&sport->port.lock, flags);
        temp = readl(sport->port.membase + UCR1);
        temp &= ~(UCR1_TXMPTYEN | UCR1_RRDYEN | UCR1_RTSDEN | UCR1_UARTEN);

        writel(temp, sport->port.membase + UCR1);
        spin_unlock_irqrestore(&sport->port.lock, flags);

        clk_disable_unprepare(sport->clk_per);
        clk_disable_unprepare(sport->clk_ipg);
}

static void imx_flush_buffer(struct uart_port *port)
{
        struct imx_port *sport = (struct imx_port *)port;
        struct scatterlist *sgl = &sport->tx_sgl[0];
        unsigned long temp;
        int i = 100, ubir, ubmr, uts;

        if (!sport->dma_chan_tx)
                return;

        sport->tx_bytes = 0;
        dmaengine_terminate_all(sport->dma_chan_tx);
        if (sport->dma_is_txing) {
                dma_unmap_sg(sport->port.dev, sgl, sport->dma_tx_nents,
                             DMA_TO_DEVICE);
                temp = readl(sport->port.membase + UCR1);
                temp &= ~UCR1_TDMAEN;
                writel(temp, sport->port.membase + UCR1);
                sport->dma_is_txing = false;
        }

        /*
         * According to the Reference Manual description of the UART SRST bit:
         * "Reset the transmit and receive state machines,
         * all FIFOs and register USR1, USR2, UBIR, UBMR, UBRC, URXD, UTXD
         * and UTS[6-3]". As we don't need to restore the old values from
         * USR1, USR2, URXD, UTXD, only save/restore the other four registers
         */
        ubir = readl(sport->port.membase + UBIR);
        ubmr = readl(sport->port.membase + UBMR);
        uts = readl(sport->port.membase + IMX21_UTS);

        temp = readl(sport->port.membase + UCR2);
        temp &= ~UCR2_SRST;
        writel(temp, sport->port.membase + UCR2);

        while (!(readl(sport->port.membase + UCR2) & UCR2_SRST) && (--i > 0))
                udelay(1);

        /* Restore the registers */
        writel(ubir, sport->port.membase + UBIR);
        writel(ubmr, sport->port.membase + UBMR);
        writel(uts, sport->port.membase + IMX21_UTS);
}

static void
imx_set_termios(struct uart_port *port, struct ktermios *termios,
                   struct ktermios *old)
{
        struct imx_port *sport = (struct imx_port *)port;
        unsigned long flags;
        unsigned int ucr2, old_ucr1, old_txrxen, baud, quot;
        unsigned int old_csize = old ? old->c_cflag & CSIZE : CS8;
        unsigned int div, ufcr;
        unsigned long num, denom;
        uint64_t tdiv64;

        /*
         * We only support CS7 and CS8.
         */
        while ((termios->c_cflag & CSIZE) != CS7 &&
               (termios->c_cflag & CSIZE) != CS8) {
                termios->c_cflag &= ~CSIZE;
                termios->c_cflag |= old_csize;
                old_csize = CS8;
        }

        if ((termios->c_cflag & CSIZE) == CS8)
                ucr2 = UCR2_WS | UCR2_SRST | UCR2_IRTS;
        else
                ucr2 = UCR2_SRST | UCR2_IRTS;

        if (termios->c_cflag & CRTSCTS) {
                if (sport->have_rtscts) {
                        ucr2 &= ~UCR2_IRTS;

                        if (port->rs485.flags & SER_RS485_ENABLED) {
                                /*
                                 * RTS is mandatory for rs485 operation, so keep
                                 * it under manual control and keep transmitter
                                 * disabled.
                                 */
                                if (!(port->rs485.flags &
                                      SER_RS485_RTS_AFTER_SEND))
                                        ucr2 |= UCR2_CTS;
                        } else {
                                ucr2 |= UCR2_CTSC;
                        }
                } else {
                        termios->c_cflag &= ~CRTSCTS;
                }
        } else if (port->rs485.flags & SER_RS485_ENABLED)
                /* disable transmitter */
                if (!(port->rs485.flags & SER_RS485_RTS_AFTER_SEND))
                        ucr2 |= UCR2_CTS;

        if (termios->c_cflag & CSTOPB)
                ucr2 |= UCR2_STPB;
        if (termios->c_cflag & PARENB) {
                ucr2 |= UCR2_PREN;
                if (termios->c_cflag & PARODD)
                        ucr2 |= UCR2_PROE;
        }

        del_timer_sync(&sport->timer);

        /*
         * Ask the core to calculate the divisor for us.
         */
        baud = uart_get_baud_rate(port, termios, old, 50, port->uartclk / 16);
        quot = uart_get_divisor(port, baud);

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

        sport->port.read_status_mask = 0;
        if (termios->c_iflag & INPCK)
                sport->port.read_status_mask |= (URXD_FRMERR | URXD_PRERR);
        if (termios->c_iflag & (BRKINT | PARMRK))
                sport->port.read_status_mask |= URXD_BRK;

        /*
         * Characters to ignore
         */
        sport->port.ignore_status_mask = 0;
        if (termios->c_iflag & IGNPAR)
                sport->port.ignore_status_mask |= URXD_PRERR | URXD_FRMERR;
        if (termios->c_iflag & IGNBRK) {
                sport->port.ignore_status_mask |= URXD_BRK;
                /*
                 * If we're ignoring parity and break indicators,
                 * ignore overruns too (for real raw support).
                 */
                if (termios->c_iflag & IGNPAR)
                        sport->port.ignore_status_mask |= URXD_OVRRUN;
        }

        if ((termios->c_cflag & CREAD) == 0)
                sport->port.ignore_status_mask |= URXD_DUMMY_READ;

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

        /*
         * disable interrupts and drain transmitter
         */
        old_ucr1 = readl(sport->port.membase + UCR1);
        writel(old_ucr1 & ~(UCR1_TXMPTYEN | UCR1_RRDYEN | UCR1_RTSDEN),
                        sport->port.membase + UCR1);

        while (!(readl(sport->port.membase + USR2) & USR2_TXDC))
                barrier();

        /* then, disable everything */
        old_txrxen = readl(sport->port.membase + UCR2);
        writel(old_txrxen & ~(UCR2_TXEN | UCR2_RXEN),
                        sport->port.membase + UCR2);
        old_txrxen &= (UCR2_TXEN | UCR2_RXEN);

        /* custom-baudrate handling */
        div = sport->port.uartclk / (baud * 16);
        if (baud == 38400 && quot != div)
                baud = sport->port.uartclk / (quot * 16);

        div = sport->port.uartclk / (baud * 16);
        if (div > 7)
                div = 7;
        if (!div)
                div = 1;

        rational_best_approximation(16 * div * baud, sport->port.uartclk,
                1 << 16, 1 << 16, &num, &denom);

        tdiv64 = sport->port.uartclk;
        tdiv64 *= num;
        do_div(tdiv64, denom * 16 * div);
        tty_termios_encode_baud_rate(termios,
                                (speed_t)tdiv64, (speed_t)tdiv64);

        num -= 1;
        denom -= 1;

        ufcr = readl(sport->port.membase + UFCR);
        ufcr = (ufcr & (~UFCR_RFDIV)) | UFCR_RFDIV_REG(div);
        if (sport->dte_mode)
                ufcr |= UFCR_DCEDTE;
        writel(ufcr, sport->port.membase + UFCR);

        writel(num, sport->port.membase + UBIR);
        writel(denom, sport->port.membase + UBMR);

        if (!is_imx1_uart(sport))
                writel(sport->port.uartclk / div / 1000,
                                sport->port.membase + IMX21_ONEMS);

        writel(old_ucr1, sport->port.membase + UCR1);

        /* set the parity, stop bits and data size */
        writel(ucr2 | old_txrxen, sport->port.membase + UCR2);

        if (UART_ENABLE_MS(&sport->port, termios->c_cflag))
                imx_enable_ms(&sport->port);

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

static const char *imx_type(struct uart_port *port)
{
        struct imx_port *sport = (struct imx_port *)port;

        return sport->port.type == PORT_IMX ? "IMX" : NULL;
}

/*
 * Configure/autoconfigure the port.
 */
static void imx_config_port(struct uart_port *port, int flags)
{
        struct imx_port *sport = (struct imx_port *)port;

        if (flags & UART_CONFIG_TYPE)
                sport->port.type = PORT_IMX;
}

/*
 * Verify the new serial_struct (for TIOCSSERIAL).
 * The only change we allow are to the flags and type, and
 * even then only between PORT_IMX and PORT_UNKNOWN
 */
static int
imx_verify_port(struct uart_port *port, struct serial_struct *ser)
{
        struct imx_port *sport = (struct imx_port *)port;
        int ret = 0;

        if (ser->type != PORT_UNKNOWN && ser->type != PORT_IMX)
                ret = -EINVAL;
        if (sport->port.irq != ser->irq)
                ret = -EINVAL;
        if (ser->io_type != UPIO_MEM)
                ret = -EINVAL;
        if (sport->port.uartclk / 16 != ser->baud_base)
                ret = -EINVAL;
        if (sport->port.mapbase != (unsigned long)ser->iomem_base)
                ret = -EINVAL;
        if (sport->port.iobase != ser->port)
                ret = -EINVAL;
        if (ser->hub6 != 0)
                ret = -EINVAL;
        return ret;
}

#if defined(CONFIG_CONSOLE_POLL)

static int imx_poll_init(struct uart_port *port)
{
        struct imx_port *sport = (struct imx_port *)port;
        unsigned long flags;
        unsigned long temp;
        int retval;

        retval = clk_prepare_enable(sport->clk_ipg);
        if (retval)
                return retval;
        retval = clk_prepare_enable(sport->clk_per);
        if (retval)
                clk_disable_unprepare(sport->clk_ipg);

        imx_setup_ufcr(sport, 0);

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

        temp = readl(sport->port.membase + UCR1);
        if (is_imx1_uart(sport))
                temp |= IMX1_UCR1_UARTCLKEN;
        temp |= UCR1_UARTEN | UCR1_RRDYEN;
        temp &= ~(UCR1_TXMPTYEN | UCR1_RTSDEN);
        writel(temp, sport->port.membase + UCR1);

        temp = readl(sport->port.membase + UCR2);
        temp |= UCR2_RXEN;
        writel(temp, sport->port.membase + UCR2);

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

        return 0;
}

static int imx_poll_get_char(struct uart_port *port)
{
        if (!(readl_relaxed(port->membase + USR2) & USR2_RDR))
                return NO_POLL_CHAR;

        return readl_relaxed(port->membase + URXD0) & URXD_RX_DATA;
}

static void imx_poll_put_char(struct uart_port *port, unsigned char c)
{
        unsigned int status;

        /* drain */
        do {
                status = readl_relaxed(port->membase + USR1);
        } while (~status & USR1_TRDY);

        /* write */
        writel_relaxed(c, port->membase + URTX0);

        /* flush */
        do {
                status = readl_relaxed(port->membase + USR2);
        } while (~status & USR2_TXDC);
}
#endif

static int imx_rs485_config(struct uart_port *port,
                            struct serial_rs485 *rs485conf)
{
        struct imx_port *sport = (struct imx_port *)port;

        /* unimplemented */
        rs485conf->delay_rts_before_send = 0;
        rs485conf->delay_rts_after_send = 0;
        rs485conf->flags |= SER_RS485_RX_DURING_TX;

        /* RTS is required to control the transmitter */
        if (!sport->have_rtscts)
                rs485conf->flags &= ~SER_RS485_ENABLED;

        if (rs485conf->flags & SER_RS485_ENABLED) {
                unsigned long temp;

                /* disable transmitter */
                temp = readl(sport->port.membase + UCR2);
                temp &= ~UCR2_CTSC;
                if (rs485conf->flags & SER_RS485_RTS_AFTER_SEND)
                        temp &= ~UCR2_CTS;
                else
                        temp |= UCR2_CTS;
                writel(temp, sport->port.membase + UCR2);
        }

        port->rs485 = *rs485conf;

        return 0;
}

static struct uart_ops imx_pops = {
        .tx_empty       = imx_tx_empty,
        .set_mctrl      = imx_set_mctrl,
        .get_mctrl      = imx_get_mctrl,
        .stop_tx        = imx_stop_tx,
        .start_tx       = imx_start_tx,
        .stop_rx        = imx_stop_rx,
        .enable_ms      = imx_enable_ms,
        .break_ctl      = imx_break_ctl,
        .startup        = imx_startup,
        .shutdown       = imx_shutdown,
        .flush_buffer   = imx_flush_buffer,
        .set_termios    = imx_set_termios,
        .type           = imx_type,
        .config_port    = imx_config_port,
        .verify_port    = imx_verify_port,
#if defined(CONFIG_CONSOLE_POLL)
        .poll_init      = imx_poll_init,
        .poll_get_char  = imx_poll_get_char,
        .poll_put_char  = imx_poll_put_char,
#endif
};

static struct imx_port *imx_ports[UART_NR];

#ifdef CONFIG_SERIAL_IMX_CONSOLE
static void imx_console_putchar(struct uart_port *port, int ch)
{
        struct imx_port *sport = (struct imx_port *)port;

        while (readl(sport->port.membase + uts_reg(sport)) & UTS_TXFULL)
                barrier();

        writel(ch, sport->port.membase + URTX0);
}

/*
 * Interrupts are disabled on entering
 */
static void
imx_console_write(struct console *co, const char *s, unsigned int count)
{
        struct imx_port *sport = imx_ports[co->index];
        struct imx_port_ucrs old_ucr;
        unsigned int ucr1;
        unsigned long flags = 0;
        int locked = 1;
        int retval;

        retval = clk_enable(sport->clk_per);
        if (retval)
                return;
        retval = clk_enable(sport->clk_ipg);
        if (retval) {
                clk_disable(sport->clk_per);
                return;
        }

        if (sport->port.sysrq)
                locked = 0;
        else if (oops_in_progress)
                locked = spin_trylock_irqsave(&sport->port.lock, flags);
        else
                spin_lock_irqsave(&sport->port.lock, flags);

        /*
         *      First, save UCR1/2/3 and then disable interrupts
         */
        imx_port_ucrs_save(&sport->port, &old_ucr);
        ucr1 = old_ucr.ucr1;

        if (is_imx1_uart(sport))
                ucr1 |= IMX1_UCR1_UARTCLKEN;
        ucr1 |= UCR1_UARTEN;
        ucr1 &= ~(UCR1_TXMPTYEN | UCR1_RRDYEN | UCR1_RTSDEN);

        writel(ucr1, sport->port.membase + UCR1);

        writel(old_ucr.ucr2 | UCR2_TXEN, sport->port.membase + UCR2);

        uart_console_write(&sport->port, s, count, imx_console_putchar);

        /*
         *      Finally, wait for transmitter to become empty
         *      and restore UCR1/2/3
         */
        while (!(readl(sport->port.membase + USR2) & USR2_TXDC));

        imx_port_ucrs_restore(&sport->port, &old_ucr);

        if (locked)
                spin_unlock_irqrestore(&sport->port.lock, flags);

        clk_disable(sport->clk_ipg);
        clk_disable(sport->clk_per);
}

/*
 * If the port was already initialised (eg, by a boot loader),
 * try to determine the current setup.
 */
static void __init
imx_console_get_options(struct imx_port *sport, int *baud,
                           int *parity, int *bits)
{

        if (readl(sport->port.membase + UCR1) & UCR1_UARTEN) {
                /* ok, the port was enabled */
                unsigned int ucr2, ubir, ubmr, uartclk;
                unsigned int baud_raw;
                unsigned int ucfr_rfdiv;

                ucr2 = readl(sport->port.membase + UCR2);

                *parity = 'n';
                if (ucr2 & UCR2_PREN) {
                        if (ucr2 & UCR2_PROE)
                                *parity = 'o';
                        else
                                *parity = 'e';
                }

                if (ucr2 & UCR2_WS)
                        *bits = 8;
                else
                        *bits = 7;

                ubir = readl(sport->port.membase + UBIR) & 0xffff;
                ubmr = readl(sport->port.membase + UBMR) & 0xffff;

                ucfr_rfdiv = (readl(sport->port.membase + UFCR) & UFCR_RFDIV) >> 7;
                if (ucfr_rfdiv == 6)
                        ucfr_rfdiv = 7;
                else
                        ucfr_rfdiv = 6 - ucfr_rfdiv;

                uartclk = clk_get_rate(sport->clk_per);
                uartclk /= ucfr_rfdiv;

                {       /*
                         * The next code provides exact computation of
                         *   baud_raw = round(((uartclk/16) * (ubir + 1)) / (ubmr + 1))
                         * without need of float support or long long division,
                         * which would be required to prevent 32bit arithmetic overflow
                         */
                        unsigned int mul = ubir + 1;
                        unsigned int div = 16 * (ubmr + 1);
                        unsigned int rem = uartclk % div;

                        baud_raw = (uartclk / div) * mul;
                        baud_raw += (rem * mul + div / 2) / div;
                        *baud = (baud_raw + 50) / 100 * 100;
                }

                if (*baud != baud_raw)
                        pr_info("Console IMX rounded baud rate from %d to %d\n",
                                baud_raw, *baud);
        }
}

static int __init
imx_console_setup(struct console *co, char *options)
{
        struct imx_port *sport;
        int baud = 9600;
        int bits = 8;
        int parity = 'n';
        int flow = 'n';
        int retval;

        /*
         * Check whether an invalid uart number has been specified, and
         * if so, search for the first available port that does have
         * console support.
         */
        if (co->index == -1 || co->index >= ARRAY_SIZE(imx_ports))
                co->index = 0;
        sport = imx_ports[co->index];
        if (sport == NULL)
                return -ENODEV;

        /* For setting the registers, we only need to enable the ipg clock. */
        retval = clk_prepare_enable(sport->clk_ipg);
        if (retval)
                goto error_console;

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

        imx_setup_ufcr(sport, 0);

        retval = uart_set_options(&sport->port, co, baud, parity, bits, flow);

        clk_disable(sport->clk_ipg);
        if (retval) {
                clk_unprepare(sport->clk_ipg);
                goto error_console;
        }

        retval = clk_prepare(sport->clk_per);
        if (retval)
                clk_disable_unprepare(sport->clk_ipg);

error_console:
        return retval;
}

static struct uart_driver imx_reg;
static struct console imx_console = {
        .name           = DEV_NAME,
        .write          = imx_console_write,
        .device         = uart_console_device,
        .setup          = imx_console_setup,
        .flags          = CON_PRINTBUFFER,
        .index          = -1,
        .data           = &imx_reg,
};

#define IMX_CONSOLE     &imx_console
#else
#define IMX_CONSOLE     NULL
#endif

static struct uart_driver imx_reg = {
        .owner          = THIS_MODULE,
        .driver_name    = DRIVER_NAME,
        .dev_name       = DEV_NAME,
        .major          = SERIAL_IMX_MAJOR,
        .minor          = MINOR_START,
        .nr             = ARRAY_SIZE(imx_ports),
        .cons           = IMX_CONSOLE,
};

static int serial_imx_suspend(struct platform_device *dev, pm_message_t state)
{
        struct imx_port *sport = platform_get_drvdata(dev);
        unsigned int val;

        /* enable wakeup from i.MX UART */
        val = readl(sport->port.membase + UCR3);
        val |= UCR3_AWAKEN;
        writel(val, sport->port.membase + UCR3);

        uart_suspend_port(&imx_reg, &sport->port);

        return 0;
}

static int serial_imx_resume(struct platform_device *dev)
{
        struct imx_port *sport = platform_get_drvdata(dev);
        unsigned int val;

        /* disable wakeup from i.MX UART */
        val = readl(sport->port.membase + UCR3);
        val &= ~UCR3_AWAKEN;
        writel(val, sport->port.membase + UCR3);

        uart_resume_port(&imx_reg, &sport->port);

        return 0;
}

#ifdef CONFIG_OF
/*
 * This function returns 1 iff pdev isn't a device instatiated by dt, 0 iff it
 * could successfully get all information from dt or a negative errno.
 */
static int serial_imx_probe_dt(struct imx_port *sport,
                struct platform_device *pdev)
{
        struct device_node *np = pdev->dev.of_node;
        const struct of_device_id *of_id =
                        of_match_device(imx_uart_dt_ids, &pdev->dev);
        int ret;

        if (!np)
                /* no device tree device */
                return 1;

        ret = of_alias_get_id(np, "serial");
        if (ret < 0) {
                dev_err(&pdev->dev, "failed to get alias id, errno %d\n", ret);
                return ret;
        }
        sport->port.line = ret;

        if (of_get_property(np, "fsl,uart-has-rtscts", NULL))
                sport->have_rtscts = 1;

        if (of_get_property(np, "fsl,dte-mode", NULL))
                sport->dte_mode = 1;

        sport->devdata = of_id->data;

        return 0;
}
#else
static inline int serial_imx_probe_dt(struct imx_port *sport,
                struct platform_device *pdev)
{
        return 1;
}
#endif

static void serial_imx_probe_pdata(struct imx_port *sport,
                struct platform_device *pdev)
{
        struct imxuart_platform_data *pdata = dev_get_platdata(&pdev->dev);

        sport->port.line = pdev->id;
        sport->devdata = (struct imx_uart_data  *) pdev->id_entry->driver_data;

        if (!pdata)
                return;

        if (pdata->flags & IMXUART_HAVE_RTSCTS)
                sport->have_rtscts = 1;
}

static int serial_imx_probe(struct platform_device *pdev)
{
        struct imx_port *sport;
        void __iomem *base;
        int ret = 0;
        struct resource *res;
        int txirq, rxirq, rtsirq;

        sport = devm_kzalloc(&pdev->dev, sizeof(*sport), GFP_KERNEL);
        if (!sport)
                return -ENOMEM;

        ret = serial_imx_probe_dt(sport, pdev);
        if (ret > 0)
                serial_imx_probe_pdata(sport, pdev);
        else if (ret < 0)
                return ret;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        base = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(base))
                return PTR_ERR(base);

        rxirq = platform_get_irq(pdev, 0);
        txirq = platform_get_irq(pdev, 1);
        rtsirq = platform_get_irq(pdev, 2);

        sport->port.dev = &pdev->dev;
        sport->port.mapbase = res->start;
        sport->port.membase = base;
        sport->port.type = PORT_IMX,
        sport->port.iotype = UPIO_MEM;
        sport->port.irq = rxirq;
        sport->port.fifosize = 32;
        sport->port.ops = &imx_pops;
        sport->port.rs485_config = imx_rs485_config;
        sport->port.rs485.flags =
                SER_RS485_RTS_ON_SEND | SER_RS485_RX_DURING_TX;
        sport->port.flags = UPF_BOOT_AUTOCONF;
        init_timer(&sport->timer);
        sport->timer.function = imx_timeout;
        sport->timer.data     = (unsigned long)sport;

        sport->clk_ipg = devm_clk_get(&pdev->dev, "ipg");
        if (IS_ERR(sport->clk_ipg)) {
                ret = PTR_ERR(sport->clk_ipg);
                dev_err(&pdev->dev, "failed to get ipg clk: %d\n", ret);
                return ret;
        }

        sport->clk_per = devm_clk_get(&pdev->dev, "per");
        if (IS_ERR(sport->clk_per)) {
                ret = PTR_ERR(sport->clk_per);
                dev_err(&pdev->dev, "failed to get per clk: %d\n", ret);
                return ret;
        }

        sport->port.uartclk = clk_get_rate(sport->clk_per);

        /*
         * Allocate the IRQ(s) i.MX1 has three interrupts whereas later
         * chips only have one interrupt.
         */
        if (txirq > 0) {
                ret = devm_request_irq(&pdev->dev, rxirq, imx_rxint, 0,
                                       dev_name(&pdev->dev), sport);
                if (ret)
                        return ret;

                ret = devm_request_irq(&pdev->dev, txirq, imx_txint, 0,
                                       dev_name(&pdev->dev), sport);
                if (ret)
                        return ret;
        } else {
                ret = devm_request_irq(&pdev->dev, rxirq, imx_int, 0,
                                       dev_name(&pdev->dev), sport);
                if (ret)
                        return ret;
        }

        imx_ports[sport->port.line] = sport;

        platform_set_drvdata(pdev, sport);

        return uart_add_one_port(&imx_reg, &sport->port);
}

static int serial_imx_remove(struct platform_device *pdev)
{
        struct imx_port *sport = platform_get_drvdata(pdev);

        return uart_remove_one_port(&imx_reg, &sport->port);
}

static struct platform_driver serial_imx_driver = {
        .probe          = serial_imx_probe,
        .remove         = serial_imx_remove,

        .suspend        = serial_imx_suspend,
        .resume         = serial_imx_resume,
        .id_table       = imx_uart_devtype,
        .driver         = {
                .name   = "imx-uart",
                .of_match_table = imx_uart_dt_ids,
        },
};

static int __init imx_serial_init(void)
{
        int ret = uart_register_driver(&imx_reg);

        if (ret)
                return ret;

        ret = platform_driver_register(&serial_imx_driver);
        if (ret != 0)
                uart_unregister_driver(&imx_reg);

        return ret;
}

static void __exit imx_serial_exit(void)
{
        platform_driver_unregister(&serial_imx_driver);
        uart_unregister_driver(&imx_reg);
}

module_init(imx_serial_init);
module_exit(imx_serial_exit);

MODULE_AUTHOR("Sascha Hauer");
MODULE_DESCRIPTION("IMX generic serial port driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:imx-uart");