// SPDX-License-Identifier: GPL-2.0+
/*
 * 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
 */

#include <linux/circ_buf.h>
#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/ktime.h>
#include <linux/pinctrl/consumer.h>
#include <linux/rational.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/dma-mapping.h>

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

#include "serial_mctrl_gpio.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_RXDMAEN    (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_TXDMAEN    (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 UCR3_DTRDEN     (1<<3)  /* Data Terminal Ready Delta 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_RXTL_MASK  0x3F    /* Receiver trigger 6 bits wide */
#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_AGTIM      (1<<8)   /* Ageing timer interrupt flag */
#define USR1_DTRD       (1<<7)   /* DTR Delta */
#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_RIDELT      (1<<10) /* Ring Interrupt Delta */
#define USR2_RIIN        (1<<9)  /* Ring Indicator Input */
#define USR2_IRINT       (1<<8)  /* Serial infrared interrupt flag */
#define USR2_WAKE        (1<<7)  /* Wake */
#define USR2_DCDIN       (1<<5)  /* Data Carrier Detect Input */
#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,
};

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

enum imx_tx_state {
        OFF,
        WAIT_AFTER_RTS,
        SEND,
        WAIT_AFTER_SEND,
};

struct imx_port {
        struct uart_port        port;
        struct timer_list       timer;
        unsigned int            old_status;
        unsigned int            have_rtscts:1;
        unsigned int            have_rtsgpio:1;
        unsigned int            dte_mode:1;
        unsigned int            inverted_tx:1;
        unsigned int            inverted_rx:1;
        struct clk              *clk_ipg;
        struct clk              *clk_per;
        const struct imx_uart_data *devdata;

        struct mctrl_gpios *gpios;

        /* counter to stop 0xff flood */
        int idle_counter;

        /* DMA fields */
        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;
        struct circ_buf         rx_ring;
        unsigned int            rx_buf_size;
        unsigned int            rx_period_length;
        unsigned int            rx_periods;
        dma_cookie_t            rx_cookie;
        unsigned int            tx_bytes;
        unsigned int            dma_tx_nents;
        unsigned int            saved_reg[10];
        bool                    context_saved;

        bool                    last_putchar_was_newline;

        enum imx_tx_state       tx_state;
        struct hrtimer          trigger_start_tx;
        struct hrtimer          trigger_stop_tx;
        unsigned int            rxtl;
};

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

static const struct imx_uart_data imx_uart_imx1_devdata = {
        .uts_reg = IMX1_UTS,
        .devtype = IMX1_UART,
};

static const struct imx_uart_data imx_uart_imx21_devdata = {
        .uts_reg = IMX21_UTS,
        .devtype = IMX21_UART,
};

static const struct of_device_id imx_uart_dt_ids[] = {
        /*
         * For reasons unknown to me, some UART devices (e.g. imx6ul's) are
         * compatible to fsl,imx6q-uart, but not fsl,imx21-uart, while the
         * original imx6q's UART is compatible to fsl,imx21-uart. This driver
         * doesn't make any distinction between these two variants.
         */
        { .compatible = "fsl,imx6q-uart", .data = &imx_uart_imx21_devdata, },
        { .compatible = "fsl,imx1-uart", .data = &imx_uart_imx1_devdata, },
        { .compatible = "fsl,imx21-uart", .data = &imx_uart_imx21_devdata, },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, imx_uart_dt_ids);

static inline struct imx_port *to_imx_port(struct uart_port *port)
{
        return container_of(port, struct imx_port, port);
}

static inline void imx_uart_writel(struct imx_port *sport, u32 val, u32 offset)
{
        writel(val, sport->port.membase + offset);
}

static inline u32 imx_uart_readl(struct imx_port *sport, u32 offset)
{
        return readl(sport->port.membase + offset);
}

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

static inline int imx_uart_is_imx1(struct imx_port *sport)
{
        return sport->devdata->devtype == IMX1_UART;
}

/*
 * Save and restore functions for UCR1, UCR2 and UCR3 registers
 */
#if IS_ENABLED(CONFIG_SERIAL_IMX_CONSOLE)
static void imx_uart_ucrs_save(struct imx_port *sport,
                               struct imx_port_ucrs *ucr)
{
        /* save control registers */
        ucr->ucr1 = imx_uart_readl(sport, UCR1);
        ucr->ucr2 = imx_uart_readl(sport, UCR2);
        ucr->ucr3 = imx_uart_readl(sport, UCR3);
}

static void imx_uart_ucrs_restore(struct imx_port *sport,
                                  struct imx_port_ucrs *ucr)
{
        /* restore control registers */
        imx_uart_writel(sport, ucr->ucr1, UCR1);
        imx_uart_writel(sport, ucr->ucr2, UCR2);
        imx_uart_writel(sport, ucr->ucr3, UCR3);
}
#endif

/* called with port.lock taken and irqs caller dependent */
static void imx_uart_rts_active(struct imx_port *sport, u32 *ucr2)
{
        *ucr2 &= ~(UCR2_CTSC | UCR2_CTS);

        mctrl_gpio_set(sport->gpios, sport->port.mctrl | TIOCM_RTS);
}

/* called with port.lock taken and irqs caller dependent */
static void imx_uart_rts_inactive(struct imx_port *sport, u32 *ucr2)
{
        *ucr2 &= ~UCR2_CTSC;
        *ucr2 |= UCR2_CTS;

        mctrl_gpio_set(sport->gpios, sport->port.mctrl & ~TIOCM_RTS);
}

static void start_hrtimer_ms(struct hrtimer *hrt, unsigned long msec)
{
       hrtimer_start(hrt, ms_to_ktime(msec), HRTIMER_MODE_REL);
}

/* called with port.lock taken and irqs off */
static void imx_uart_soft_reset(struct imx_port *sport)
{
        int i = 10;
        u32 ucr2, ubir, ubmr, uts;

        /*
         * 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]".
         *
         * We don't need to restore the old values from USR1, USR2, URXD and
         * UTXD. UBRC is read only, so only save/restore the other three
         * registers.
         */
        ubir = imx_uart_readl(sport, UBIR);
        ubmr = imx_uart_readl(sport, UBMR);
        uts = imx_uart_readl(sport, IMX21_UTS);

        ucr2 = imx_uart_readl(sport, UCR2);
        imx_uart_writel(sport, ucr2 & ~UCR2_SRST, UCR2);

        while (!(imx_uart_readl(sport, UCR2) & UCR2_SRST) && (--i > 0))
                udelay(1);

        /* Restore the registers */
        imx_uart_writel(sport, ubir, UBIR);
        imx_uart_writel(sport, ubmr, UBMR);
        imx_uart_writel(sport, uts, IMX21_UTS);

        sport->idle_counter = 0;
}

/* called with port.lock taken and irqs off */
static void imx_uart_disable_loopback_rs485(struct imx_port *sport)
{
        unsigned int uts;

        /* See SER_RS485_ENABLED/UTS_LOOP comment in imx_uart_probe() */
        uts = imx_uart_readl(sport, imx_uart_uts_reg(sport));
        uts &= ~UTS_LOOP;
        imx_uart_writel(sport, uts, imx_uart_uts_reg(sport));
}

/* called with port.lock taken and irqs off */
static void imx_uart_start_rx(struct uart_port *port)
{
        struct imx_port *sport = to_imx_port(port);
        unsigned int ucr1, ucr2;

        ucr1 = imx_uart_readl(sport, UCR1);
        ucr2 = imx_uart_readl(sport, UCR2);

        ucr2 |= UCR2_RXEN;

        if (sport->dma_is_enabled) {
                ucr1 |= UCR1_RXDMAEN | UCR1_ATDMAEN;
        } else {
                ucr1 |= UCR1_RRDYEN;
                ucr2 |= UCR2_ATEN;
        }

        /* Write UCR2 first as it includes RXEN */
        imx_uart_writel(sport, ucr2, UCR2);
        imx_uart_writel(sport, ucr1, UCR1);
        imx_uart_disable_loopback_rs485(sport);
}

/* called with port.lock taken and irqs off */
static void imx_uart_stop_tx(struct uart_port *port)
{
        struct imx_port *sport = to_imx_port(port);
        u32 ucr1, ucr4, usr2;

        if (sport->tx_state == OFF)
                return;

        /*
         * 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_txing)
                return;

        ucr1 = imx_uart_readl(sport, UCR1);
        imx_uart_writel(sport, ucr1 & ~UCR1_TRDYEN, UCR1);

        ucr4 = imx_uart_readl(sport, UCR4);
        usr2 = imx_uart_readl(sport, USR2);
        if ((!(usr2 & USR2_TXDC)) && (ucr4 & UCR4_TCEN)) {
                /* The shifter is still busy, so retry once TC triggers */
                return;
        }

        ucr4 &= ~UCR4_TCEN;
        imx_uart_writel(sport, ucr4, UCR4);

        /* in rs485 mode disable transmitter */
        if (port->rs485.flags & SER_RS485_ENABLED) {
                if (sport->tx_state == SEND) {
                        sport->tx_state = WAIT_AFTER_SEND;

                        if (port->rs485.delay_rts_after_send > 0) {
                                start_hrtimer_ms(&sport->trigger_stop_tx,
                                         port->rs485.delay_rts_after_send);
                                return;
                        }

                        /* continue without any delay */
                }

                if (sport->tx_state == WAIT_AFTER_RTS ||
                    sport->tx_state == WAIT_AFTER_SEND) {
                        u32 ucr2;

                        hrtimer_try_to_cancel(&sport->trigger_start_tx);

                        ucr2 = imx_uart_readl(sport, UCR2);
                        if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND)
                                imx_uart_rts_active(sport, &ucr2);
                        else
                                imx_uart_rts_inactive(sport, &ucr2);
                        imx_uart_writel(sport, ucr2, UCR2);

                        if (!port->rs485_rx_during_tx_gpio)
                                imx_uart_start_rx(port);

                        sport->tx_state = OFF;
                }
        } else {
                sport->tx_state = OFF;
        }
}

/* called with port.lock taken and irqs off */
static void imx_uart_stop_rx_with_loopback_ctrl(struct uart_port *port, bool loopback)
{
        struct imx_port *sport = to_imx_port(port);
        u32 ucr1, ucr2, ucr4, uts;

        ucr1 = imx_uart_readl(sport, UCR1);
        ucr2 = imx_uart_readl(sport, UCR2);
        ucr4 = imx_uart_readl(sport, UCR4);

        if (sport->dma_is_enabled) {
                ucr1 &= ~(UCR1_RXDMAEN | UCR1_ATDMAEN);
        } else {
                ucr1 &= ~UCR1_RRDYEN;
                ucr2 &= ~UCR2_ATEN;
                ucr4 &= ~UCR4_OREN;
        }
        imx_uart_writel(sport, ucr1, UCR1);
        imx_uart_writel(sport, ucr4, UCR4);

        /* See SER_RS485_ENABLED/UTS_LOOP comment in imx_uart_probe() */
        if (port->rs485.flags & SER_RS485_ENABLED &&
            port->rs485.flags & SER_RS485_RTS_ON_SEND &&
            sport->have_rtscts && !sport->have_rtsgpio && loopback) {
                uts = imx_uart_readl(sport, imx_uart_uts_reg(sport));
                uts |= UTS_LOOP;
                imx_uart_writel(sport, uts, imx_uart_uts_reg(sport));
                ucr2 |= UCR2_RXEN;
        } else {
                ucr2 &= ~UCR2_RXEN;
        }

        imx_uart_writel(sport, ucr2, UCR2);
}

/* called with port.lock taken and irqs off */
static void imx_uart_stop_rx(struct uart_port *port)
{
        /*
         * Stop RX and enable loopback in order to make sure RS485 bus
         * is not blocked. Se comment in imx_uart_probe().
         */
        imx_uart_stop_rx_with_loopback_ctrl(port, true);
}

/* called with port.lock taken and irqs off */
static void imx_uart_enable_ms(struct uart_port *port)
{
        struct imx_port *sport = to_imx_port(port);

        mod_timer(&sport->timer, jiffies);

        mctrl_gpio_enable_ms(sport->gpios);
}

static void imx_uart_dma_tx(struct imx_port *sport);

/* called with port.lock taken and irqs off */
static inline void imx_uart_transmit_buffer(struct imx_port *sport)
{
        struct tty_port *tport = &sport->port.state->port;
        unsigned char c;

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

        if (kfifo_is_empty(&tport->xmit_fifo) ||
                        uart_tx_stopped(&sport->port)) {
                imx_uart_stop_tx(&sport->port);
                return;
        }

        if (sport->dma_is_enabled) {
                u32 ucr1;
                /*
                 * We've just sent a X-char Ensure the TX DMA is enabled
                 * and the TX IRQ is disabled.
                 **/
                ucr1 = imx_uart_readl(sport, UCR1);
                ucr1 &= ~UCR1_TRDYEN;
                if (sport->dma_is_txing) {
                        ucr1 |= UCR1_TXDMAEN;
                        imx_uart_writel(sport, ucr1, UCR1);
                } else {
                        imx_uart_writel(sport, ucr1, UCR1);
                        imx_uart_dma_tx(sport);
                }

                return;
        }

        while (!(imx_uart_readl(sport, imx_uart_uts_reg(sport)) & UTS_TXFULL) &&
                        uart_fifo_get(&sport->port, &c))
                imx_uart_writel(sport, c, URTX0);

        if (kfifo_len(&tport->xmit_fifo) < WAKEUP_CHARS)
                uart_write_wakeup(&sport->port);

        if (kfifo_is_empty(&tport->xmit_fifo))
                imx_uart_stop_tx(&sport->port);
}

static void imx_uart_dma_tx_callback(void *data)
{
        struct imx_port *sport = data;
        struct tty_port *tport = &sport->port.state->port;
        struct scatterlist *sgl = &sport->tx_sgl[0];
        unsigned long flags;
        u32 ucr1;

        uart_port_lock_irqsave(&sport->port, &flags);

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

        ucr1 = imx_uart_readl(sport, UCR1);
        ucr1 &= ~UCR1_TXDMAEN;
        imx_uart_writel(sport, ucr1, UCR1);

        uart_xmit_advance(&sport->port, sport->tx_bytes);

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

        sport->dma_is_txing = 0;

        if (kfifo_len(&tport->xmit_fifo) < WAKEUP_CHARS)
                uart_write_wakeup(&sport->port);

        if (!kfifo_is_empty(&tport->xmit_fifo) &&
                        !uart_tx_stopped(&sport->port))
                imx_uart_dma_tx(sport);
        else if (sport->port.rs485.flags & SER_RS485_ENABLED) {
                u32 ucr4 = imx_uart_readl(sport, UCR4);
                ucr4 |= UCR4_TCEN;
                imx_uart_writel(sport, ucr4, UCR4);
        }

        uart_port_unlock_irqrestore(&sport->port, flags);
}

/* called with port.lock taken and irqs off */
static void imx_uart_dma_tx(struct imx_port *sport)
{
        struct tty_port *tport = &sport->port.state->port;
        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;
        u32 ucr1, ucr4;
        int ret;

        if (sport->dma_is_txing)
                return;

        ucr4 = imx_uart_readl(sport, UCR4);
        ucr4 &= ~UCR4_TCEN;
        imx_uart_writel(sport, ucr4, UCR4);

        sg_init_table(sgl, ARRAY_SIZE(sport->tx_sgl));
        sport->tx_bytes = kfifo_len(&tport->xmit_fifo);
        sport->dma_tx_nents = kfifo_dma_out_prepare(&tport->xmit_fifo, sgl,
                        ARRAY_SIZE(sport->tx_sgl), sport->tx_bytes);

        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, ret,
                                        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 = imx_uart_dma_tx_callback;
        desc->callback_param = sport;

        dev_dbg(dev, "TX: prepare to send %u bytes by DMA.\n", sport->tx_bytes);

        ucr1 = imx_uart_readl(sport, UCR1);
        ucr1 |= UCR1_TXDMAEN;
        imx_uart_writel(sport, ucr1, UCR1);

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

/* called with port.lock taken and irqs off */
static void imx_uart_start_tx(struct uart_port *port)
{
        struct imx_port *sport = to_imx_port(port);
        struct tty_port *tport = &sport->port.state->port;
        u32 ucr1;

        if (!sport->port.x_char && kfifo_is_empty(&tport->xmit_fifo))
                return;

        /*
         * We cannot simply do nothing here if sport->tx_state == SEND already
         * because UCR1_TXMPTYEN might already have been cleared in
         * imx_uart_stop_tx(), but tx_state is still SEND.
         */

        if (port->rs485.flags & SER_RS485_ENABLED) {
                if (sport->tx_state == OFF) {
                        u32 ucr2 = imx_uart_readl(sport, UCR2);
                        if (port->rs485.flags & SER_RS485_RTS_ON_SEND)
                                imx_uart_rts_active(sport, &ucr2);
                        else
                                imx_uart_rts_inactive(sport, &ucr2);
                        imx_uart_writel(sport, ucr2, UCR2);

                        /*
                         * Since we are about to transmit we can not stop RX
                         * with loopback enabled because that will make our
                         * transmitted data being just looped to RX.
                         */
                        if (!(port->rs485.flags & SER_RS485_RX_DURING_TX) &&
                            !port->rs485_rx_during_tx_gpio)
                                imx_uart_stop_rx_with_loopback_ctrl(port, false);

                        sport->tx_state = WAIT_AFTER_RTS;

                        if (port->rs485.delay_rts_before_send > 0) {
                                start_hrtimer_ms(&sport->trigger_start_tx,
                                         port->rs485.delay_rts_before_send);
                                return;
                        }

                        /* continue without any delay */
                }

                if (sport->tx_state == WAIT_AFTER_SEND
                    || sport->tx_state == WAIT_AFTER_RTS) {

                        hrtimer_try_to_cancel(&sport->trigger_stop_tx);

                        /*
                         * Enable transmitter and shifter empty irq only if DMA
                         * is off.  In the DMA case this is done in the
                         * tx-callback.
                         */
                        if (!sport->dma_is_enabled) {
                                u32 ucr4 = imx_uart_readl(sport, UCR4);
                                ucr4 |= UCR4_TCEN;
                                imx_uart_writel(sport, ucr4, UCR4);
                        }

                        sport->tx_state = SEND;
                }
        } else {
                sport->tx_state = SEND;
        }

        if (!sport->dma_is_enabled) {
                ucr1 = imx_uart_readl(sport, UCR1);
                imx_uart_writel(sport, ucr1 | UCR1_TRDYEN, 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 */
                        ucr1 = imx_uart_readl(sport, UCR1);
                        ucr1 &= ~UCR1_TXDMAEN;
                        ucr1 |= UCR1_TRDYEN;
                        imx_uart_writel(sport, ucr1, UCR1);
                        return;
                }

                if (!kfifo_is_empty(&tport->xmit_fifo) &&
                    !uart_tx_stopped(port))
                        imx_uart_dma_tx(sport);
                return;
        }
}

static irqreturn_t __imx_uart_rtsint(int irq, void *dev_id)
{
        struct imx_port *sport = dev_id;
        u32 usr1;

        imx_uart_writel(sport, USR1_RTSD, USR1);
        usr1 = imx_uart_readl(sport, USR1) & USR1_RTSS;
        /*
         * Update sport->old_status here, so any follow-up calls to
         * imx_uart_mctrl_check() will be able to recognize that RTS
         * state changed since last imx_uart_mctrl_check() call.
         *
         * In case RTS has been detected as asserted here and later on
         * deasserted by the time imx_uart_mctrl_check() was called,
         * imx_uart_mctrl_check() can detect the RTS state change and
         * trigger uart_handle_cts_change() to unblock the port for
         * further TX transfers.
         */
        if (usr1 & USR1_RTSS)
                sport->old_status |= TIOCM_CTS;
        else
                sport->old_status &= ~TIOCM_CTS;
        uart_handle_cts_change(&sport->port, usr1);
        wake_up_interruptible(&sport->port.state->port.delta_msr_wait);

        return IRQ_HANDLED;
}

static irqreturn_t imx_uart_rtsint(int irq, void *dev_id)
{
        struct imx_port *sport = dev_id;
        irqreturn_t ret;

        uart_port_lock(&sport->port);

        ret = __imx_uart_rtsint(irq, dev_id);

        uart_port_unlock(&sport->port);

        return ret;
}

static irqreturn_t imx_uart_txint(int irq, void *dev_id)
{
        struct imx_port *sport = dev_id;

        uart_port_lock(&sport->port);
        imx_uart_transmit_buffer(sport);
        uart_port_unlock(&sport->port);
        return IRQ_HANDLED;
}

/* Check if hardware Rx flood is in progress, and issue soft reset to stop it.
 * This is to be called from Rx ISRs only when some bytes were actually
 * received.
 *
 * A way to reproduce the flood (checked on iMX6SX) is: open iMX UART at 9600
 * 8N1, and from external source send 0xf0 char at 115200 8N1. In about 90% of
 * cases this starts a flood of "receiving" of 0xff characters by the iMX6 UART
 * that is terminated by any activity on RxD line, or could be stopped by
 * issuing soft reset to the UART (just stop/start of RX does not help). Note
 * that what we do here is sending isolated start bit about 2.4 times shorter
 * than it is to be on UART configured baud rate.
 *
 * Called with port.lock taken and irqs off.
 */
static void imx_uart_check_flood(struct imx_port *sport, u32 usr2)
{
        /* To detect hardware 0xff flood we monitor RxD line between RX
         * interrupts to isolate "receiving" of char(s) with no activity
         * on RxD line, that'd never happen on actual data transfers.
         *
         * We use USR2_WAKE bit to check for activity on RxD line, but we have a
         * race here if we clear USR2_WAKE when receiving of a char is in
         * progress, so we might get RX interrupt later with USR2_WAKE bit
         * cleared. Note though that as we don't try to clear USR2_WAKE when we
         * detected no activity, this race may hide actual activity only once.
         *
         * Yet another case where receive interrupt may occur without RxD
         * activity is expiration of aging timer, so we consider this as well.
         *
         * We use 'idle_counter' to ensure that we got at least so many RX
         * interrupts without any detected activity on RxD line. 2 cases
         * described plus 1 to be on the safe side gives us a margin of 3,
         * below. In practice I was not able to produce a false positive to
         * induce soft reset at regular data transfers even using 1 as the
         * margin, so 3 is actually very strong.
         *
         * We count interrupts, not chars in 'idle-counter' for simplicity.
         */

        if (usr2 & USR2_WAKE) {
                imx_uart_writel(sport, USR2_WAKE, USR2);
                sport->idle_counter = 0;
        } else if (++sport->idle_counter > 3) {
                dev_warn(sport->port.dev, "RX flood detected: soft reset.");
                imx_uart_soft_reset(sport); /* also clears 'sport->idle_counter' */
        }
}

/* called with port.lock taken and irqs off */
static irqreturn_t __imx_uart_rxint(int irq, void *dev_id)
{
        struct imx_port *sport = dev_id;
        struct tty_port *port = &sport->port.state->port;
        u32 usr2, rx;

        /* If we received something, check for 0xff flood */
        usr2 = imx_uart_readl(sport, USR2);
        if (usr2 & USR2_RDR)
                imx_uart_check_flood(sport, usr2);

        while ((rx = imx_uart_readl(sport, URXD0)) & URXD_CHARRDY) {
                unsigned int flg = TTY_NORMAL;
                sport->port.icount.rx++;

                if (unlikely(rx & URXD_ERR)) {
                        if (rx & URXD_BRK) {
                                sport->port.icount.brk++;
                                if (uart_handle_break(&sport->port))
                                        continue;
                        }
                        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)
                                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;

                        sport->port.sysrq = 0;
                } else if (uart_handle_sysrq_char(&sport->port, (unsigned char)rx)) {
                        continue;
                }

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

                if (tty_insert_flip_char(port, rx, flg) == 0)
                        sport->port.icount.buf_overrun++;
        }

        tty_flip_buffer_push(port);

        return IRQ_HANDLED;
}

static irqreturn_t imx_uart_rxint(int irq, void *dev_id)
{
        struct imx_port *sport = dev_id;
        irqreturn_t ret;

        uart_port_lock(&sport->port);

        ret = __imx_uart_rxint(irq, dev_id);

        uart_port_unlock(&sport->port);

        return ret;
}

static void imx_uart_clear_rx_errors(struct imx_port *sport);

/*
 * We have a modem side uart, so the meanings of RTS and CTS are inverted.
 */
/* called with port.lock taken and irqs off */
static unsigned int imx_uart_get_hwmctrl(struct imx_port *sport)
{
        unsigned int tmp = TIOCM_DSR;
        unsigned usr1 = imx_uart_readl(sport, USR1);
        unsigned usr2 = imx_uart_readl(sport, USR2);

        if (usr1 & USR1_RTSS)
                tmp |= TIOCM_CTS;

        /* in DCE mode DCDIN is always 0 */
        if (!(usr2 & USR2_DCDIN))
                tmp |= TIOCM_CAR;

        if (sport->dte_mode)
                if (!(imx_uart_readl(sport, USR2) & USR2_RIIN))
                        tmp |= TIOCM_RI;

        return tmp;
}

/*
 * Handle any change of modem status signal since we were last called.
 *
 * Called with port.lock taken and irqs off.
 */
static void imx_uart_mctrl_check(struct imx_port *sport)
{
        unsigned int status, changed;

        status = imx_uart_get_hwmctrl(sport);
        changed = status ^ sport->old_status;

        if (changed == 0)
                return;

        sport->old_status = status;

        if (changed & TIOCM_RI && status & 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);
}

static irqreturn_t imx_uart_int(int irq, void *dev_id)
{
        struct imx_port *sport = dev_id;
        unsigned int usr1, usr2, ucr1, ucr2, ucr3, ucr4;
        irqreturn_t ret = IRQ_NONE;

        uart_port_lock(&sport->port);

        usr1 = imx_uart_readl(sport, USR1);
        usr2 = imx_uart_readl(sport, USR2);
        ucr1 = imx_uart_readl(sport, UCR1);
        ucr2 = imx_uart_readl(sport, UCR2);
        ucr3 = imx_uart_readl(sport, UCR3);
        ucr4 = imx_uart_readl(sport, UCR4);

        /*
         * Even if a condition is true that can trigger an irq only handle it if
         * the respective irq source is enabled. This prevents some undesired
         * actions, for example if a character that sits in the RX FIFO and that
         * should be fetched via DMA is tried to be fetched using PIO. Or the
         * receiver is currently off and so reading from URXD0 results in an
         * exception. So just mask the (raw) status bits for disabled irqs.
         */
        if ((ucr1 & UCR1_RRDYEN) == 0)
                usr1 &= ~USR1_RRDY;
        if ((ucr2 & UCR2_ATEN) == 0)
                usr1 &= ~USR1_AGTIM;
        if ((ucr1 & UCR1_TRDYEN) == 0)
                usr1 &= ~USR1_TRDY;
        if ((ucr4 & UCR4_TCEN) == 0)
                usr2 &= ~USR2_TXDC;
        if ((ucr3 & UCR3_DTRDEN) == 0)
                usr1 &= ~USR1_DTRD;
        if ((ucr1 & UCR1_RTSDEN) == 0)
                usr1 &= ~USR1_RTSD;
        if ((ucr3 & UCR3_AWAKEN) == 0)
                usr1 &= ~USR1_AWAKE;
        if ((ucr4 & UCR4_OREN) == 0)
                usr2 &= ~USR2_ORE;

        if (usr1 & (USR1_RRDY | USR1_AGTIM)) {
                imx_uart_writel(sport, USR1_AGTIM, USR1);

                __imx_uart_rxint(irq, dev_id);
                ret = IRQ_HANDLED;
        }

        if ((usr1 & USR1_TRDY) || (usr2 & USR2_TXDC)) {
                imx_uart_transmit_buffer(sport);
                ret = IRQ_HANDLED;
        }

        if (usr1 & USR1_DTRD) {
                imx_uart_writel(sport, USR1_DTRD, USR1);

                imx_uart_mctrl_check(sport);

                ret = IRQ_HANDLED;
        }

        if (usr1 & USR1_RTSD) {
                __imx_uart_rtsint(irq, dev_id);
                ret = IRQ_HANDLED;
        }

        if (usr1 & USR1_AWAKE) {
                imx_uart_writel(sport, USR1_AWAKE, USR1);
                ret = IRQ_HANDLED;
        }

        if (usr2 & USR2_ORE) {
                sport->port.icount.overrun++;
                imx_uart_writel(sport, USR2_ORE, USR2);
                ret = IRQ_HANDLED;
        }

        uart_port_unlock(&sport->port);

        return ret;
}

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

        ret = (imx_uart_readl(sport, USR2) & USR2_TXDC) ?  TIOCSER_TEMT : 0;

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

        return ret;
}

/* called with port.lock taken and irqs off */
static unsigned int imx_uart_get_mctrl(struct uart_port *port)
{
        struct imx_port *sport = to_imx_port(port);
        unsigned int ret = imx_uart_get_hwmctrl(sport);

        mctrl_gpio_get(sport->gpios, &ret);

        return ret;
}

/* called with port.lock taken and irqs off */
static void imx_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
        struct imx_port *sport = to_imx_port(port);
        u32 ucr3, uts;

        if (!(port->rs485.flags & SER_RS485_ENABLED)) {
                u32 ucr2;

                /*
                 * Turn off autoRTS if RTS is lowered and restore autoRTS
                 * setting if RTS is raised.
                 */
                ucr2 = imx_uart_readl(sport, UCR2);
                ucr2 &= ~(UCR2_CTS | UCR2_CTSC);
                if (mctrl & TIOCM_RTS) {
                        ucr2 |= UCR2_CTS;
                        /*
                         * UCR2_IRTS is unset if and only if the port is
                         * configured for CRTSCTS, so we use inverted UCR2_IRTS
                         * to get the state to restore to.
                         */
                        if (!(ucr2 & UCR2_IRTS))
                                ucr2 |= UCR2_CTSC;
                }
                imx_uart_writel(sport, ucr2, UCR2);
        }

        ucr3 = imx_uart_readl(sport, UCR3) & ~UCR3_DSR;
        if (!(mctrl & TIOCM_DTR))
                ucr3 |= UCR3_DSR;
        imx_uart_writel(sport, ucr3, UCR3);

        uts = imx_uart_readl(sport, imx_uart_uts_reg(sport)) & ~UTS_LOOP;
        if (mctrl & TIOCM_LOOP)
                uts |= UTS_LOOP;
        imx_uart_writel(sport, uts, imx_uart_uts_reg(sport));

        mctrl_gpio_set(sport->gpios, mctrl);
}

/*
 * Interrupts always disabled.
 */
static void imx_uart_break_ctl(struct uart_port *port, int break_state)
{
        struct imx_port *sport = to_imx_port(port);
        unsigned long flags;
        u32 ucr1;

        uart_port_lock_irqsave(&sport->port, &flags);

        ucr1 = imx_uart_readl(sport, UCR1) & ~UCR1_SNDBRK;

        if (break_state != 0)
                ucr1 |= UCR1_SNDBRK;

        imx_uart_writel(sport, ucr1, UCR1);

        uart_port_unlock_irqrestore(&sport->port, flags);
}

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

        if (sport->port.state) {
                uart_port_lock_irqsave(&sport->port, &flags);
                imx_uart_mctrl_check(sport);
                uart_port_unlock_irqrestore(&sport->port, flags);

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

/*
 * There are two kinds of RX DMA interrupts(such as in the MX6Q):
 *   [1] the RX DMA buffer is full.
 *   [2] the aging timer expires
 *
 * Condition [2] is triggered when a character has been sitting in the FIFO
 * for at least 8 byte durations.
 */
static void imx_uart_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;
        struct circ_buf *rx_ring = &sport->rx_ring;
        enum dma_status status;
        unsigned int w_bytes = 0;
        unsigned int r_bytes;
        unsigned int bd_size;

        status = dmaengine_tx_status(chan, sport->rx_cookie, &state);

        if (status == DMA_ERROR) {
                uart_port_lock(&sport->port);
                imx_uart_clear_rx_errors(sport);
                uart_port_unlock(&sport->port);
                return;
        }

        /*
         * The state-residue variable represents the empty space
         * relative to the entire buffer. Taking this in consideration
         * the head is always calculated base on the buffer total
         * length - DMA transaction residue. The UART script from the
         * SDMA firmware will jump to the next buffer descriptor,
         * once a DMA transaction if finalized (IMX53 RM - A.4.1.2.4).
         * Taking this in consideration the tail is always at the
         * beginning of the buffer descriptor that contains the head.
         */

        /* Calculate the head */
        rx_ring->head = sg_dma_len(sgl) - state.residue;

        /* Calculate the tail. */
        bd_size = sg_dma_len(sgl) / sport->rx_periods;
        rx_ring->tail = ((rx_ring->head-1) / bd_size) * bd_size;

        if (rx_ring->head <= sg_dma_len(sgl) &&
            rx_ring->head > rx_ring->tail) {

                /* Move data from tail to head */
                r_bytes = rx_ring->head - rx_ring->tail;

                /* If we received something, check for 0xff flood */
                uart_port_lock(&sport->port);
                imx_uart_check_flood(sport, imx_uart_readl(sport, USR2));
                uart_port_unlock(&sport->port);

                if (!(sport->port.ignore_status_mask & URXD_DUMMY_READ)) {

                        /* CPU claims ownership of RX DMA buffer */
                        dma_sync_sg_for_cpu(sport->port.dev, sgl, 1,
                                            DMA_FROM_DEVICE);

                        w_bytes = tty_insert_flip_string(port,
                                                         sport->rx_buf + rx_ring->tail, r_bytes);

                        /* UART retrieves ownership of RX DMA buffer */
                        dma_sync_sg_for_device(sport->port.dev, sgl, 1,
                                               DMA_FROM_DEVICE);

                        if (w_bytes != r_bytes)
                                sport->port.icount.buf_overrun++;

                        sport->port.icount.rx += w_bytes;
                }
        } else  {
                WARN_ON(rx_ring->head > sg_dma_len(sgl));
                WARN_ON(rx_ring->head <= rx_ring->tail);
        }

        if (w_bytes) {
                tty_flip_buffer_push(port);
                dev_dbg(sport->port.dev, "We get %d bytes.\n", w_bytes);
        }
}

static int imx_uart_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;

        sport->rx_ring.head = 0;
        sport->rx_ring.tail = 0;

        sg_init_one(sgl, sport->rx_buf, sport->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_dma_cyclic(chan, sg_dma_address(sgl),
                sg_dma_len(sgl), sg_dma_len(sgl) / sport->rx_periods,
                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 = imx_uart_dma_rx_callback;
        desc->callback_param = sport;

        dev_dbg(dev, "RX: prepare for the DMA.\n");
        sport->dma_is_rxing = 1;
        sport->rx_cookie = dmaengine_submit(desc);
        dma_async_issue_pending(chan);
        return 0;
}

/* called with port.lock taken and irqs off */
static void imx_uart_clear_rx_errors(struct imx_port *sport)
{
        struct tty_port *port = &sport->port.state->port;
        u32 usr1, usr2;

        usr1 = imx_uart_readl(sport, USR1);
        usr2 = imx_uart_readl(sport, USR2);

        if (usr2 & USR2_BRCD) {
                sport->port.icount.brk++;
                imx_uart_writel(sport, USR2_BRCD, USR2);
                uart_handle_break(&sport->port);
                if (tty_insert_flip_char(port, 0, TTY_BREAK) == 0)
                        sport->port.icount.buf_overrun++;
                tty_flip_buffer_push(port);
        } else {
                if (usr1 & USR1_FRAMERR) {
                        sport->port.icount.frame++;
                        imx_uart_writel(sport, USR1_FRAMERR, USR1);
                } else if (usr1 & USR1_PARITYERR) {
                        sport->port.icount.parity++;
                        imx_uart_writel(sport, USR1_PARITYERR, USR1);
                }
        }

        if (usr2 & USR2_ORE) {
                sport->port.icount.overrun++;
                imx_uart_writel(sport, USR2_ORE, USR2);
        }

        sport->idle_counter = 0;

}

#define TXTL_DEFAULT 8
#define RXTL_DEFAULT 8 /* 8 characters or aging timer */
#define RXTL_CONSOLE_DEFAULT 1
#define TXTL_DMA 8 /* DMA burst setting */
#define RXTL_DMA 9 /* DMA burst setting */

static void imx_uart_setup_ufcr(struct imx_port *sport,
                                unsigned char txwl, unsigned char rxwl)
{
        unsigned int val;

        /* set receiver / transmitter trigger level */
        val = imx_uart_readl(sport, UFCR) & (UFCR_RFDIV | UFCR_DCEDTE);
        val |= txwl << UFCR_TXTL_SHF | rxwl;
        imx_uart_writel(sport, val, UFCR);
}

static void imx_uart_dma_exit(struct imx_port *sport)
{
        if (sport->dma_chan_rx) {
                dmaengine_terminate_sync(sport->dma_chan_rx);
                dma_release_channel(sport->dma_chan_rx);
                sport->dma_chan_rx = NULL;
                sport->rx_cookie = -EINVAL;
                kfree(sport->rx_buf);
                sport->rx_buf = NULL;
        }

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

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

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

        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;
        /* one byte less than the watermark level to enable the aging timer */
        slave_config.src_maxburst = RXTL_DMA - 1;
        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_size = sport->rx_period_length * sport->rx_periods;
        sport->rx_buf = kzalloc(sport->rx_buf_size, GFP_KERNEL);
        if (!sport->rx_buf) {
                ret = -ENOMEM;
                goto err;
        }
        sport->rx_ring.buf = sport->rx_buf;

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

        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_DMA;
        ret = dmaengine_slave_config(sport->dma_chan_tx, &slave_config);
        if (ret) {
                dev_err(dev, "error in TX dma configuration.");
                goto err;
        }

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

/* called with port.lock taken and irqs off */
static void imx_uart_enable_dma(struct imx_port *sport)
{
        u32 ucr1;

        imx_uart_setup_ufcr(sport, TXTL_DMA, RXTL_DMA);

        /* set UCR1 */
        ucr1 = imx_uart_readl(sport, UCR1);
        ucr1 |= UCR1_RXDMAEN | UCR1_TXDMAEN | UCR1_ATDMAEN;
        imx_uart_writel(sport, ucr1, UCR1);

        sport->dma_is_enabled = 1;
}

static void imx_uart_disable_dma(struct imx_port *sport)
{
        u32 ucr1;

        /* clear UCR1 */
        ucr1 = imx_uart_readl(sport, UCR1);
        ucr1 &= ~(UCR1_RXDMAEN | UCR1_TXDMAEN | UCR1_ATDMAEN);
        imx_uart_writel(sport, ucr1, UCR1);

        imx_uart_setup_ufcr(sport, TXTL_DEFAULT, sport->rxtl);

        sport->dma_is_enabled = 0;
}

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

static int imx_uart_startup(struct uart_port *port)
{
        struct imx_port *sport = to_imx_port(port);
        int retval;
        unsigned long flags;
        int dma_is_inited = 0;
        u32 ucr1, ucr2, ucr3, ucr4;

        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;
        }

        if (uart_console(&sport->port))
                sport->rxtl = RXTL_CONSOLE_DEFAULT;
        else
                sport->rxtl = RXTL_DEFAULT;

        imx_uart_setup_ufcr(sport, TXTL_DEFAULT, sport->rxtl);

        /* disable the DREN bit (Data Ready interrupt enable) before
         * requesting IRQs
         */
        ucr4 = imx_uart_readl(sport, UCR4);

        /* set the trigger level for CTS */
        ucr4 &= ~(UCR4_CTSTL_MASK << UCR4_CTSTL_SHF);
        ucr4 |= CTSTL << UCR4_CTSTL_SHF;

        imx_uart_writel(sport, ucr4 & ~UCR4_DREN, UCR4);

        /* Can we enable the DMA support? */
        if (!uart_console(port) && imx_uart_dma_init(sport) == 0) {
                lockdep_set_subclass(&port->lock, 1);
                dma_is_inited = 1;
        }

        uart_port_lock_irqsave(&sport->port, &flags);

        /* Reset fifo's and state machines */
        imx_uart_soft_reset(sport);

        /*
         * Finally, clear and enable interrupts
         */
        imx_uart_writel(sport, USR1_RTSD | USR1_DTRD, USR1);
        imx_uart_writel(sport, USR2_ORE, USR2);

        ucr1 = imx_uart_readl(sport, UCR1) & ~UCR1_RRDYEN;
        ucr1 |= UCR1_UARTEN;
        if (sport->have_rtscts)
                ucr1 |= UCR1_RTSDEN;

        imx_uart_writel(sport, ucr1, UCR1);

        ucr4 = imx_uart_readl(sport, UCR4) & ~(UCR4_OREN | UCR4_INVR);
        if (!dma_is_inited)
                ucr4 |= UCR4_OREN;
        if (sport->inverted_rx)
                ucr4 |= UCR4_INVR;
        imx_uart_writel(sport, ucr4, UCR4);

        ucr3 = imx_uart_readl(sport, UCR3) & ~UCR3_INVT;
        /*
         * configure tx polarity before enabling tx
         */
        if (sport->inverted_tx)
                ucr3 |= UCR3_INVT;

        if (!imx_uart_is_imx1(sport)) {
                ucr3 |= UCR3_DTRDEN | UCR3_RI | UCR3_DCD;

                if (sport->dte_mode)
                        /* disable broken interrupts */
                        ucr3 &= ~(UCR3_RI | UCR3_DCD);
        }
        imx_uart_writel(sport, ucr3, UCR3);

        ucr2 = imx_uart_readl(sport, UCR2) & ~UCR2_ATEN;
        ucr2 |= (UCR2_RXEN | UCR2_TXEN);
        if (!sport->have_rtscts)
                ucr2 |= UCR2_IRTS;
        /*
         * make sure the edge sensitive RTS-irq is disabled,
         * we're using RTSD instead.
         */
        if (!imx_uart_is_imx1(sport))
                ucr2 &= ~UCR2_RTSEN;
        imx_uart_writel(sport, ucr2, UCR2);

        /*
         * Enable modem status interrupts
         */
        imx_uart_enable_ms(&sport->port);

        if (dma_is_inited) {
                imx_uart_enable_dma(sport);
                imx_uart_start_rx_dma(sport);
        } else {
                ucr1 = imx_uart_readl(sport, UCR1);
                ucr1 |= UCR1_RRDYEN;
                imx_uart_writel(sport, ucr1, UCR1);

                ucr2 = imx_uart_readl(sport, UCR2);
                ucr2 |= UCR2_ATEN;
                imx_uart_writel(sport, ucr2, UCR2);
        }

        imx_uart_disable_loopback_rs485(sport);

        uart_port_unlock_irqrestore(&sport->port, flags);

        return 0;
}

static void imx_uart_shutdown(struct uart_port *port)
{
        struct imx_port *sport = to_imx_port(port);
        unsigned long flags;
        u32 ucr1, ucr2, ucr4, uts;
        int loops;

        if (sport->dma_is_enabled) {
                dmaengine_terminate_sync(sport->dma_chan_tx);
                if (sport->dma_is_txing) {
                        dma_unmap_sg(sport->port.dev, &sport->tx_sgl[0],
                                     sport->dma_tx_nents, DMA_TO_DEVICE);
                        sport->dma_is_txing = 0;
                }
                dmaengine_terminate_sync(sport->dma_chan_rx);
                if (sport->dma_is_rxing) {
                        dma_unmap_sg(sport->port.dev, &sport->rx_sgl,
                                     1, DMA_FROM_DEVICE);
                        sport->dma_is_rxing = 0;
                }

                uart_port_lock_irqsave(&sport->port, &flags);
                imx_uart_stop_tx(port);
                imx_uart_stop_rx(port);
                imx_uart_disable_dma(sport);
                uart_port_unlock_irqrestore(&sport->port, flags);
                imx_uart_dma_exit(sport);
        }

        mctrl_gpio_disable_ms_sync(sport->gpios);

        uart_port_lock_irqsave(&sport->port, &flags);
        ucr2 = imx_uart_readl(sport, UCR2);
        ucr2 &= ~(UCR2_TXEN | UCR2_ATEN);
        imx_uart_writel(sport, ucr2, UCR2);
        uart_port_unlock_irqrestore(&sport->port, flags);

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

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

        uart_port_lock_irqsave(&sport->port, &flags);

        ucr1 = imx_uart_readl(sport, UCR1);
        ucr1 &= ~(UCR1_TRDYEN | UCR1_RRDYEN | UCR1_RTSDEN | UCR1_RXDMAEN |
                  UCR1_ATDMAEN | UCR1_SNDBRK);
        /* See SER_RS485_ENABLED/UTS_LOOP comment in imx_uart_probe() */
        if (port->rs485.flags & SER_RS485_ENABLED &&
            port->rs485.flags & SER_RS485_RTS_ON_SEND &&
            sport->have_rtscts && !sport->have_rtsgpio) {
                uts = imx_uart_readl(sport, imx_uart_uts_reg(sport));
                uts |= UTS_LOOP;
                imx_uart_writel(sport, uts, imx_uart_uts_reg(sport));
                ucr1 |= UCR1_UARTEN;
        } else {
                ucr1 &= ~UCR1_UARTEN;
        }
        imx_uart_writel(sport, ucr1, UCR1);

        ucr4 = imx_uart_readl(sport, UCR4);
        ucr4 &= ~UCR4_TCEN;
        imx_uart_writel(sport, ucr4, UCR4);

        /*
         * We have to ensure the tx state machine ends up in OFF. This
         * is especially important for rs485 where we must not leave
         * the RTS signal high, blocking the bus indefinitely.
         *
         * All interrupts are now disabled, so imx_uart_stop_tx() will
         * no longer be called from imx_uart_transmit_buffer(). It may
         * still be called via the hrtimers, and if those are in play,
         * we have to honour the delays.
         */
        if (sport->tx_state == WAIT_AFTER_RTS || sport->tx_state == SEND)
                imx_uart_stop_tx(port);

        /*
         * In many cases (rs232 mode, or if tx_state was
         * WAIT_AFTER_RTS, or if tx_state was SEND and there is no
         * delay_rts_after_send), this will have moved directly to
         * OFF. In rs485 mode, tx_state might already have been
         * WAIT_AFTER_SEND and the hrtimer thus already started, or
         * the above imx_uart_stop_tx() call could have started it. In
         * those cases, we have to wait for the hrtimer to fire and
         * complete the transition to OFF.
         */
        loops = port->rs485.flags & SER_RS485_ENABLED ?
                port->rs485.delay_rts_after_send : 0;
        while (sport->tx_state != OFF && loops--) {
                uart_port_unlock_irqrestore(&sport->port, flags);
                msleep(1);
                uart_port_lock_irqsave(&sport->port, &flags);
        }

        if (sport->tx_state != OFF) {
                dev_warn(sport->port.dev, "unexpected tx_state %d\n",
                         sport->tx_state);
                /*
                 * This machine may be busted, but ensure the RTS
                 * signal is inactive in order not to block other
                 * devices.
                 */
                if (port->rs485.flags & SER_RS485_ENABLED) {
                        ucr2 = imx_uart_readl(sport, UCR2);
                        if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND)
                                imx_uart_rts_active(sport, &ucr2);
                        else
                                imx_uart_rts_inactive(sport, &ucr2);
                        imx_uart_writel(sport, ucr2, UCR2);
                }
                sport->tx_state = OFF;
        }

        uart_port_unlock_irqrestore(&sport->port, flags);

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

/* called with port.lock taken and irqs off */
static void imx_uart_flush_buffer(struct uart_port *port)
{
        struct imx_port *sport = to_imx_port(port);
        struct scatterlist *sgl = &sport->tx_sgl[0];

        if (!sport->dma_chan_tx)
                return;

        sport->tx_bytes = 0;
        dmaengine_terminate_all(sport->dma_chan_tx);
        if (sport->dma_is_txing) {
                u32 ucr1;

                dma_unmap_sg(sport->port.dev, sgl, sport->dma_tx_nents,
                             DMA_TO_DEVICE);
                ucr1 = imx_uart_readl(sport, UCR1);
                ucr1 &= ~UCR1_TXDMAEN;
                imx_uart_writel(sport, ucr1, UCR1);
                sport->dma_is_txing = 0;
        }

        imx_uart_soft_reset(sport);

}

static void
imx_uart_set_termios(struct uart_port *port, struct ktermios *termios,
                     const struct ktermios *old)
{
        struct imx_port *sport = to_imx_port(port);
        unsigned long flags;
        u32 ucr2, old_ucr2, ufcr;
        unsigned int baud, quot;
        unsigned int old_csize = old ? old->c_cflag & CSIZE : CS8;
        unsigned long div;
        unsigned long num, denom, old_ubir, old_ubmr;
        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;
        }

        timer_delete_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);

        uart_port_lock_irqsave(&sport->port, &flags);

        /*
         * Read current UCR2 and save it for future use, then clear all the bits
         * except those we will or may need to preserve.
         */
        old_ucr2 = imx_uart_readl(sport, UCR2);
        ucr2 = old_ucr2 & (UCR2_TXEN | UCR2_RXEN | UCR2_ATEN | UCR2_CTS);

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

        if (!sport->have_rtscts)
                termios->c_cflag &= ~CRTSCTS;

        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)
                        imx_uart_rts_active(sport, &ucr2);
                else
                        imx_uart_rts_inactive(sport, &ucr2);

        } else if (termios->c_cflag & CRTSCTS) {
                /*
                 * Only let receiver control RTS output if we were not requested
                 * to have RTS inactive (which then should take precedence).
                 */
                if (ucr2 & UCR2_CTS)
                        ucr2 |= UCR2_CTSC;
        }

        if (termios->c_cflag & CRTSCTS)
                ucr2 &= ~UCR2_IRTS;
        if (termios->c_cflag & CSTOPB)
                ucr2 |= UCR2_STPB;
        if (termios->c_cflag & PARENB) {
                ucr2 |= UCR2_PREN;
                if (termios->c_cflag & PARODD)
                        ucr2 |= UCR2_PROE;
        }

        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);

        /* 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 = imx_uart_readl(sport, UFCR);
        ufcr = (ufcr & (~UFCR_RFDIV)) | UFCR_RFDIV_REG(div);
        imx_uart_writel(sport, ufcr, UFCR);

        /*
         *  Two registers below should always be written both and in this
         *  particular order. One consequence is that we need to check if any of
         *  them changes and then update both. We do need the check for change
         *  as even writing the same values seem to "restart"
         *  transmission/receiving logic in the hardware, that leads to data
         *  breakage even when rate doesn't in fact change. E.g., user switches
         *  RTS/CTS handshake and suddenly gets broken bytes.
         */
        old_ubir = imx_uart_readl(sport, UBIR);
        old_ubmr = imx_uart_readl(sport, UBMR);
        if (old_ubir != num || old_ubmr != denom) {
                imx_uart_writel(sport, num, UBIR);
                imx_uart_writel(sport, denom, UBMR);
        }

        if (!imx_uart_is_imx1(sport))
                imx_uart_writel(sport, sport->port.uartclk / div / 1000,
                                IMX21_ONEMS);

        imx_uart_writel(sport, ucr2, UCR2);

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

        uart_port_unlock_irqrestore(&sport->port, flags);
}

static const char *imx_uart_type(struct uart_port *port)
{
        return port->type == PORT_IMX ? "IMX" : NULL;
}

/*
 * Configure/autoconfigure the port.
 */
static void imx_uart_config_port(struct uart_port *port, int flags)
{
        if (flags & UART_CONFIG_TYPE)
                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_uart_verify_port(struct uart_port *port, struct serial_struct *ser)
{
        int ret = 0;

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

#if defined(CONFIG_CONSOLE_POLL)

static int imx_uart_poll_init(struct uart_port *port)
{
        struct imx_port *sport = to_imx_port(port);
        unsigned long flags;
        u32 ucr1, ucr2;
        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_uart_setup_ufcr(sport, TXTL_DEFAULT, sport->rxtl);

        uart_port_lock_irqsave(&sport->port, &flags);

        /*
         * Be careful about the order of enabling bits here. First enable the
         * receiver (UARTEN + RXEN) and only then the corresponding irqs.
         * This prevents that a character that already sits in the RX fifo is
         * triggering an irq but the try to fetch it from there results in an
         * exception because UARTEN or RXEN is still off.
         */
        ucr1 = imx_uart_readl(sport, UCR1);
        ucr2 = imx_uart_readl(sport, UCR2);

        if (imx_uart_is_imx1(sport))
                ucr1 |= IMX1_UCR1_UARTCLKEN;

        ucr1 |= UCR1_UARTEN;
        ucr1 &= ~(UCR1_TRDYEN | UCR1_RTSDEN | UCR1_RRDYEN);

        ucr2 |= UCR2_RXEN | UCR2_TXEN;
        ucr2 &= ~UCR2_ATEN;

        imx_uart_writel(sport, ucr1, UCR1);
        imx_uart_writel(sport, ucr2, UCR2);

        /* now enable irqs */
        imx_uart_writel(sport, ucr1 | UCR1_RRDYEN, UCR1);
        imx_uart_writel(sport, ucr2 | UCR2_ATEN, UCR2);

        uart_port_unlock_irqrestore(&sport->port, flags);

        return 0;
}

static int imx_uart_poll_get_char(struct uart_port *port)
{
        struct imx_port *sport = to_imx_port(port);
        if (!(imx_uart_readl(sport, USR2) & USR2_RDR))
                return NO_POLL_CHAR;

        return imx_uart_readl(sport, URXD0) & URXD_RX_DATA;
}

static void imx_uart_poll_put_char(struct uart_port *port, unsigned char c)
{
        struct imx_port *sport = to_imx_port(port);
        unsigned int status;

        /* drain */
        do {
                status = imx_uart_readl(sport, USR1);
        } while (~status & USR1_TRDY);

        /* write */
        imx_uart_writel(sport, c, URTX0);

        /* flush */
        do {
                status = imx_uart_readl(sport, USR2);
        } while (~status & USR2_TXDC);
}
#endif

/* called with port.lock taken and irqs off or from .probe without locking */
static int imx_uart_rs485_config(struct uart_port *port, struct ktermios *termios,
                                 struct serial_rs485 *rs485conf)
{
        struct imx_port *sport = to_imx_port(port);
        u32 ucr2, ufcr;

        if (rs485conf->flags & SER_RS485_ENABLED) {
                /* Enable receiver if low-active RTS signal is requested */
                if (sport->have_rtscts &&  !sport->have_rtsgpio &&
                    !(rs485conf->flags & SER_RS485_RTS_ON_SEND))
                        rs485conf->flags |= SER_RS485_RX_DURING_TX;

                /* disable transmitter */
                ucr2 = imx_uart_readl(sport, UCR2);
                if (rs485conf->flags & SER_RS485_RTS_AFTER_SEND)
                        imx_uart_rts_active(sport, &ucr2);
                else
                        imx_uart_rts_inactive(sport, &ucr2);
                imx_uart_writel(sport, ucr2, UCR2);
        }

        /* Make sure Rx is enabled in case Tx is active with Rx disabled */
        if (!(rs485conf->flags & SER_RS485_ENABLED) ||
            rs485conf->flags & SER_RS485_RX_DURING_TX) {
                /* If the receiver trigger is 0, set it to a default value */
                ufcr = imx_uart_readl(sport, UFCR);
                if ((ufcr & UFCR_RXTL_MASK) == 0)
                        imx_uart_setup_ufcr(sport, TXTL_DEFAULT, sport->rxtl);
                imx_uart_start_rx(port);
        }

        return 0;
}

static const struct uart_ops imx_uart_pops = {
        .tx_empty       = imx_uart_tx_empty,
        .set_mctrl      = imx_uart_set_mctrl,
        .get_mctrl      = imx_uart_get_mctrl,
        .stop_tx        = imx_uart_stop_tx,
        .start_tx       = imx_uart_start_tx,
        .stop_rx        = imx_uart_stop_rx,
        .enable_ms      = imx_uart_enable_ms,
        .break_ctl      = imx_uart_break_ctl,
        .startup        = imx_uart_startup,
        .shutdown       = imx_uart_shutdown,
        .flush_buffer   = imx_uart_flush_buffer,
        .set_termios    = imx_uart_set_termios,
        .type           = imx_uart_type,
        .config_port    = imx_uart_config_port,
        .verify_port    = imx_uart_verify_port,
#if defined(CONFIG_CONSOLE_POLL)
        .poll_init      = imx_uart_poll_init,
        .poll_get_char  = imx_uart_poll_get_char,
        .poll_put_char  = imx_uart_poll_put_char,
#endif
};

static struct imx_port *imx_uart_ports[UART_NR];

#if IS_ENABLED(CONFIG_SERIAL_IMX_CONSOLE)
static void imx_uart_console_putchar(struct uart_port *port, unsigned char ch)
{
        struct imx_port *sport = to_imx_port(port);

        while (imx_uart_readl(sport, imx_uart_uts_reg(sport)) & UTS_TXFULL)
                barrier();

        imx_uart_writel(sport, ch, URTX0);

        sport->last_putchar_was_newline = (ch == '\n');
}

static void imx_uart_console_device_lock(struct console *co, unsigned long *flags)
{
        struct uart_port *up = &imx_uart_ports[co->index]->port;

        return __uart_port_lock_irqsave(up, flags);
}

static void imx_uart_console_device_unlock(struct console *co, unsigned long flags)
{
        struct uart_port *up = &imx_uart_ports[co->index]->port;

        return __uart_port_unlock_irqrestore(up, flags);
}

static void imx_uart_console_write_atomic(struct console *co,
                                          struct nbcon_write_context *wctxt)
{
        struct imx_port *sport = imx_uart_ports[co->index];
        struct uart_port *port = &sport->port;
        struct imx_port_ucrs old_ucr;
        unsigned int ucr1, usr2;

        if (!nbcon_enter_unsafe(wctxt))
                return;

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

        if (imx_uart_is_imx1(sport))
                ucr1 |= IMX1_UCR1_UARTCLKEN;
        ucr1 |= UCR1_UARTEN;
        ucr1 &= ~(UCR1_TRDYEN | UCR1_RRDYEN | UCR1_RTSDEN);

        imx_uart_writel(sport, ucr1, UCR1);
        imx_uart_writel(sport, old_ucr.ucr2 | UCR2_TXEN, UCR2);

        if (!sport->last_putchar_was_newline)
                uart_console_write(port, "\n", 1, imx_uart_console_putchar);
        uart_console_write(port, wctxt->outbuf, wctxt->len,
                           imx_uart_console_putchar);

        /*
         *      Finally, wait for transmitter to become empty
         *      and restore UCR1/2/3
         */
        read_poll_timeout_atomic(imx_uart_readl, usr2, usr2 & USR2_TXDC,
                                 0, USEC_PER_SEC, false, sport, USR2);
        imx_uart_ucrs_restore(sport, &old_ucr);

        nbcon_exit_unsafe(wctxt);
}

static void imx_uart_console_write_thread(struct console *co,
                                          struct nbcon_write_context *wctxt)
{
        struct imx_port *sport = imx_uart_ports[co->index];
        struct uart_port *port = &sport->port;
        struct imx_port_ucrs old_ucr;
        unsigned int ucr1, usr2;

        if (!nbcon_enter_unsafe(wctxt))
                return;

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

        if (imx_uart_is_imx1(sport))
                ucr1 |= IMX1_UCR1_UARTCLKEN;
        ucr1 |= UCR1_UARTEN;
        ucr1 &= ~(UCR1_TRDYEN | UCR1_RRDYEN | UCR1_RTSDEN);

        imx_uart_writel(sport, ucr1, UCR1);
        imx_uart_writel(sport, old_ucr.ucr2 | UCR2_TXEN, UCR2);

        if (nbcon_exit_unsafe(wctxt)) {
                int len = READ_ONCE(wctxt->len);
                int i;

                /*
                 * Write out the message. Toggle unsafe for each byte in order
                 * to give another (higher priority) context the opportunity
                 * for a friendly takeover. If such a takeover occurs, this
                 * context must reacquire ownership in order to perform final
                 * actions (such as re-enabling the interrupts).
                 *
                 * IMPORTANT: wctxt->outbuf and wctxt->len are no longer valid
                 *            after a reacquire so writing the message must be
                 *            aborted.
                 */
                for (i = 0; i < len; i++) {
                        if (!nbcon_enter_unsafe(wctxt))
                                break;

                        uart_console_write(port, wctxt->outbuf + i, 1,
                                           imx_uart_console_putchar);

                        if (!nbcon_exit_unsafe(wctxt))
                                break;
                }
        }

        while (!nbcon_enter_unsafe(wctxt))
                nbcon_reacquire_nobuf(wctxt);

        /*
         *      Finally, wait for transmitter to become empty
         *      and restore UCR1/2/3
         */
        read_poll_timeout(imx_uart_readl, usr2, usr2 & USR2_TXDC,
                          0, USEC_PER_SEC, false, sport, USR2);
        imx_uart_ucrs_restore(sport, &old_ucr);

        nbcon_exit_unsafe(wctxt);
}

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

        if (imx_uart_readl(sport, UCR1) & UCR1_UARTEN) {
                /* ok, the port was enabled */
                unsigned int ucr2, ubir, ubmr, uartclk;
                unsigned int baud_raw;
                unsigned int ucfr_rfdiv;

                ucr2 = imx_uart_readl(sport, 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 = imx_uart_readl(sport, UBIR) & 0xffff;
                ubmr = imx_uart_readl(sport, UBMR) & 0xffff;

                ucfr_rfdiv = (imx_uart_readl(sport, 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)
                        dev_info(sport->port.dev, "Console IMX rounded baud rate from %d to %d\n",
                                baud_raw, *baud);
        }
}

static int
imx_uart_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_uart_ports))
                co->index = 0;
        sport = imx_uart_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;

        sport->last_putchar_was_newline = true;

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

        imx_uart_setup_ufcr(sport, TXTL_DEFAULT, sport->rxtl);

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

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

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

error_console:
        return retval;
}

static int
imx_uart_console_exit(struct console *co)
{
        struct imx_port *sport = imx_uart_ports[co->index];

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

        return 0;
}

static struct uart_driver imx_uart_uart_driver;
static struct console imx_uart_console = {
        .name           = DEV_NAME,
        .write_atomic   = imx_uart_console_write_atomic,
        .write_thread   = imx_uart_console_write_thread,
        .device_lock    = imx_uart_console_device_lock,
        .device_unlock  = imx_uart_console_device_unlock,
        .flags          = CON_PRINTBUFFER | CON_NBCON,
        .device         = uart_console_device,
        .setup          = imx_uart_console_setup,
        .exit           = imx_uart_console_exit,
        .index          = -1,
        .data           = &imx_uart_uart_driver,
};

#define IMX_CONSOLE     &imx_uart_console

#else
#define IMX_CONSOLE     NULL
#endif

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

static enum hrtimer_restart imx_trigger_start_tx(struct hrtimer *t)
{
        struct imx_port *sport = container_of(t, struct imx_port, trigger_start_tx);
        unsigned long flags;

        uart_port_lock_irqsave(&sport->port, &flags);
        if (sport->tx_state == WAIT_AFTER_RTS)
                imx_uart_start_tx(&sport->port);
        uart_port_unlock_irqrestore(&sport->port, flags);

        return HRTIMER_NORESTART;
}

static enum hrtimer_restart imx_trigger_stop_tx(struct hrtimer *t)
{
        struct imx_port *sport = container_of(t, struct imx_port, trigger_stop_tx);
        unsigned long flags;

        uart_port_lock_irqsave(&sport->port, &flags);
        if (sport->tx_state == WAIT_AFTER_SEND)
                imx_uart_stop_tx(&sport->port);
        uart_port_unlock_irqrestore(&sport->port, flags);

        return HRTIMER_NORESTART;
}

static const struct serial_rs485 imx_rs485_supported = {
        .flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTER_SEND |
                 SER_RS485_RX_DURING_TX,
        .delay_rts_before_send = 1,
        .delay_rts_after_send = 1,
};

/* Default RX DMA buffer configuration */
#define RX_DMA_PERIODS          16
#define RX_DMA_PERIOD_LEN       (PAGE_SIZE / 4)

static int imx_uart_probe(struct platform_device *pdev)
{
        struct device_node *np = pdev->dev.of_node;
        struct imx_port *sport;
        void __iomem *base;
        u32 dma_buf_conf[2];
        int ret = 0;
        u32 ucr1, ucr2, uts;
        struct resource *res;
        int txirq, rxirq, rtsirq;

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

        sport->devdata = of_device_get_match_data(&pdev->dev);

        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;

        sport->have_rtscts = of_property_read_bool(np, "uart-has-rtscts") ||
                of_property_read_bool(np, "fsl,uart-has-rtscts"); /* deprecated */

        sport->dte_mode = of_property_read_bool(np, "fsl,dte-mode");

        sport->have_rtsgpio = of_property_present(np, "rts-gpios");

        sport->inverted_tx = of_property_read_bool(np, "fsl,inverted-tx");

        sport->inverted_rx = of_property_read_bool(np, "fsl,inverted-rx");

        if (!of_property_read_u32_array(np, "fsl,dma-info", dma_buf_conf, 2)) {
                sport->rx_period_length = dma_buf_conf[0];
                sport->rx_periods = dma_buf_conf[1];
        } else {
                sport->rx_period_length = RX_DMA_PERIOD_LEN;
                sport->rx_periods = RX_DMA_PERIODS;
        }

        if (sport->port.line >= ARRAY_SIZE(imx_uart_ports)) {
                dev_err(&pdev->dev, "serial%d out of range\n",
                        sport->port.line);
                return -EINVAL;
        }

        base = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
        if (IS_ERR(base))
                return PTR_ERR(base);

        rxirq = platform_get_irq(pdev, 0);
        if (rxirq < 0)
                return rxirq;
        txirq = platform_get_irq_optional(pdev, 1);
        rtsirq = platform_get_irq_optional(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.has_sysrq = IS_ENABLED(CONFIG_SERIAL_IMX_CONSOLE);
        sport->port.ops = &imx_uart_pops;
        sport->port.rs485_config = imx_uart_rs485_config;
        /* RTS is required to control the RS485 transmitter */
        if (sport->have_rtscts || sport->have_rtsgpio)
                sport->port.rs485_supported = imx_rs485_supported;
        sport->port.flags = UPF_BOOT_AUTOCONF;
        timer_setup(&sport->timer, imx_uart_timeout, 0);

        sport->gpios = mctrl_gpio_init(&sport->port, 0);
        if (IS_ERR(sport->gpios))
                return PTR_ERR(sport->gpios);

        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);

        /* For register access, we only need to enable the ipg clock. */
        ret = clk_prepare_enable(sport->clk_ipg);
        if (ret) {
                dev_err(&pdev->dev, "failed to enable ipg clk: %d\n", ret);
                return ret;
        }

        ret = uart_get_rs485_mode(&sport->port);
        if (ret)
                goto err_clk;

        /*
         * If using the i.MX UART RTS/CTS control then the RTS (CTS_B)
         * signal cannot be set low during transmission in case the
         * receiver is off (limitation of the i.MX UART IP).
         */
        if (sport->port.rs485.flags & SER_RS485_ENABLED &&
            sport->have_rtscts && !sport->have_rtsgpio &&
            (!(sport->port.rs485.flags & SER_RS485_RTS_ON_SEND) &&
             !(sport->port.rs485.flags & SER_RS485_RX_DURING_TX)))
                dev_err(&pdev->dev,
                        "low-active RTS not possible when receiver is off, enabling receiver\n");

        /* Disable interrupts before requesting them */
        ucr1 = imx_uart_readl(sport, UCR1);
        ucr1 &= ~(UCR1_ADEN | UCR1_TRDYEN | UCR1_IDEN | UCR1_RRDYEN | UCR1_RTSDEN);
        imx_uart_writel(sport, ucr1, UCR1);

        /* Disable Ageing Timer interrupt */
        ucr2 = imx_uart_readl(sport, UCR2);
        ucr2 &= ~UCR2_ATEN;
        imx_uart_writel(sport, ucr2, UCR2);

        /*
         * In case RS485 is enabled without GPIO RTS control, the UART IP
         * is used to control CTS signal. Keep both the UART and Receiver
         * enabled, otherwise the UART IP pulls CTS signal always HIGH no
         * matter how the UCR2 CTSC and CTS bits are set. To prevent any
         * data from being fed into the RX FIFO, enable loopback mode in
         * UTS register, which disconnects the RX path from external RXD
         * pin and connects it to the Transceiver, which is disabled, so
         * no data can be fed to the RX FIFO that way.
         */
        if (sport->port.rs485.flags & SER_RS485_ENABLED &&
            sport->have_rtscts && !sport->have_rtsgpio) {
                uts = imx_uart_readl(sport, imx_uart_uts_reg(sport));
                uts |= UTS_LOOP;
                imx_uart_writel(sport, uts, imx_uart_uts_reg(sport));

                ucr1 = imx_uart_readl(sport, UCR1);
                ucr1 |= UCR1_UARTEN;
                imx_uart_writel(sport, ucr1, UCR1);

                ucr2 = imx_uart_readl(sport, UCR2);
                ucr2 |= UCR2_RXEN;
                imx_uart_writel(sport, ucr2, UCR2);
        }

        if (!imx_uart_is_imx1(sport) && sport->dte_mode) {
                /*
                 * The DCEDTE bit changes the direction of DSR, DCD, DTR and RI
                 * and influences if UCR3_RI and UCR3_DCD changes the level of RI
                 * and DCD (when they are outputs) or enables the respective
                 * irqs. So set this bit early, i.e. before requesting irqs.
                 */
                u32 ufcr = imx_uart_readl(sport, UFCR);
                if (!(ufcr & UFCR_DCEDTE))
                        imx_uart_writel(sport, ufcr | UFCR_DCEDTE, UFCR);

                /*
                 * Disable UCR3_RI and UCR3_DCD irqs. They are also not
                 * enabled later because they cannot be cleared
                 * (confirmed on i.MX25) which makes them unusable.
                 */
                imx_uart_writel(sport,
                                IMX21_UCR3_RXDMUXSEL | UCR3_ADNIMP | UCR3_DSR,
                                UCR3);

        } else {
                u32 ucr3 = UCR3_DSR;
                u32 ufcr = imx_uart_readl(sport, UFCR);
                if (ufcr & UFCR_DCEDTE)
                        imx_uart_writel(sport, ufcr & ~UFCR_DCEDTE, UFCR);

                if (!imx_uart_is_imx1(sport))
                        ucr3 |= IMX21_UCR3_RXDMUXSEL | UCR3_ADNIMP;
                imx_uart_writel(sport, ucr3, UCR3);
        }

        hrtimer_setup(&sport->trigger_start_tx, imx_trigger_start_tx, CLOCK_MONOTONIC,
                      HRTIMER_MODE_REL);
        hrtimer_setup(&sport->trigger_stop_tx, imx_trigger_stop_tx, CLOCK_MONOTONIC,
                      HRTIMER_MODE_REL);

        /*
         * 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_uart_rxint, 0,
                                       dev_name(&pdev->dev), sport);
                if (ret) {
                        dev_err(&pdev->dev, "failed to request rx irq: %d\n",
                                ret);
                        goto err_clk;
                }

                ret = devm_request_irq(&pdev->dev, txirq, imx_uart_txint, 0,
                                       dev_name(&pdev->dev), sport);
                if (ret) {
                        dev_err(&pdev->dev, "failed to request tx irq: %d\n",
                                ret);
                        goto err_clk;
                }

                ret = devm_request_irq(&pdev->dev, rtsirq, imx_uart_rtsint, 0,
                                       dev_name(&pdev->dev), sport);
                if (ret) {
                        dev_err(&pdev->dev, "failed to request rts irq: %d\n",
                                ret);
                        goto err_clk;
                }
        } else {
                ret = devm_request_irq(&pdev->dev, rxirq, imx_uart_int, 0,
                                       dev_name(&pdev->dev), sport);
                if (ret) {
                        dev_err(&pdev->dev, "failed to request irq: %d\n", ret);
                        goto err_clk;
                }
        }

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

        platform_set_drvdata(pdev, sport);

        ret = uart_add_one_port(&imx_uart_uart_driver, &sport->port);

err_clk:
        clk_disable_unprepare(sport->clk_ipg);

        return ret;
}

static void imx_uart_remove(struct platform_device *pdev)
{
        struct imx_port *sport = platform_get_drvdata(pdev);

        uart_remove_one_port(&imx_uart_uart_driver, &sport->port);
}

static void imx_uart_restore_context(struct imx_port *sport)
{
        unsigned long flags;

        uart_port_lock_irqsave(&sport->port, &flags);
        if (!sport->context_saved) {
                uart_port_unlock_irqrestore(&sport->port, flags);
                return;
        }

        imx_uart_writel(sport, sport->saved_reg[4], UFCR);
        imx_uart_writel(sport, sport->saved_reg[5], UESC);
        imx_uart_writel(sport, sport->saved_reg[6], UTIM);
        imx_uart_writel(sport, sport->saved_reg[7], UBIR);
        imx_uart_writel(sport, sport->saved_reg[8], UBMR);
        imx_uart_writel(sport, sport->saved_reg[9], IMX21_UTS);
        imx_uart_writel(sport, sport->saved_reg[0], UCR1);
        imx_uart_writel(sport, sport->saved_reg[1] | UCR2_SRST, UCR2);
        imx_uart_writel(sport, sport->saved_reg[2], UCR3);
        imx_uart_writel(sport, sport->saved_reg[3], UCR4);
        sport->context_saved = false;
        uart_port_unlock_irqrestore(&sport->port, flags);
}

static void imx_uart_save_context(struct imx_port *sport)
{
        unsigned long flags;

        /* Save necessary regs */
        uart_port_lock_irqsave(&sport->port, &flags);
        sport->saved_reg[0] = imx_uart_readl(sport, UCR1);
        sport->saved_reg[1] = imx_uart_readl(sport, UCR2);
        sport->saved_reg[2] = imx_uart_readl(sport, UCR3);
        sport->saved_reg[3] = imx_uart_readl(sport, UCR4);
        sport->saved_reg[4] = imx_uart_readl(sport, UFCR);
        sport->saved_reg[5] = imx_uart_readl(sport, UESC);
        sport->saved_reg[6] = imx_uart_readl(sport, UTIM);
        sport->saved_reg[7] = imx_uart_readl(sport, UBIR);
        sport->saved_reg[8] = imx_uart_readl(sport, UBMR);
        sport->saved_reg[9] = imx_uart_readl(sport, IMX21_UTS);
        sport->context_saved = true;
        uart_port_unlock_irqrestore(&sport->port, flags);
}

/* called with irq off */
static void imx_uart_enable_wakeup(struct imx_port *sport, bool on)
{
        struct tty_port *port = &sport->port.state->port;
        struct device *tty_dev;
        bool may_wake = false, wake_active = false;
        u32 ucr3, usr1;

        scoped_guard(tty_port_tty, port) {
                struct tty_struct *tty = scoped_tty();

                tty_dev = tty->dev;
                may_wake = tty_dev && device_may_wakeup(tty_dev);
        }

        /* only configure the wake register when device set as wakeup source */
        if (!may_wake)
                return;

        uart_port_lock_irq(&sport->port);

        usr1 = imx_uart_readl(sport, USR1);
        ucr3 = imx_uart_readl(sport, UCR3);
        if (on) {
                imx_uart_writel(sport, USR1_AWAKE, USR1);
                ucr3 |= UCR3_AWAKEN;
        } else {
                ucr3 &= ~UCR3_AWAKEN;
                wake_active = usr1 & USR1_AWAKE;
        }
        imx_uart_writel(sport, ucr3, UCR3);

        if (sport->have_rtscts) {
                u32 ucr1 = imx_uart_readl(sport, UCR1);
                if (on) {
                        imx_uart_writel(sport, USR1_RTSD, USR1);
                        ucr1 |= UCR1_RTSDEN;
                } else {
                        ucr1 &= ~UCR1_RTSDEN;
                        wake_active = wake_active || (usr1 & USR1_RTSD);
                }
                imx_uart_writel(sport, ucr1, UCR1);
        }

        if (wake_active && irqd_is_wakeup_set(irq_get_irq_data(sport->port.irq)))
                pm_wakeup_event(tty_port_tty_get(port)->dev, 0);

        uart_port_unlock_irq(&sport->port);
}

static int imx_uart_suspend_noirq(struct device *dev)
{
        struct imx_port *sport = dev_get_drvdata(dev);

        imx_uart_save_context(sport);

        clk_disable(sport->clk_ipg);

        pinctrl_pm_select_sleep_state(dev);

        return 0;
}

static int imx_uart_resume_noirq(struct device *dev)
{
        struct imx_port *sport = dev_get_drvdata(dev);
        int ret;

        pinctrl_pm_select_default_state(dev);

        ret = clk_enable(sport->clk_ipg);
        if (ret)
                return ret;

        imx_uart_restore_context(sport);

        return 0;
}

static int imx_uart_suspend(struct device *dev)
{
        struct imx_port *sport = dev_get_drvdata(dev);
        int ret;

        uart_suspend_port(&imx_uart_uart_driver, &sport->port);
        disable_irq(sport->port.irq);

        ret = clk_prepare_enable(sport->clk_ipg);
        if (ret)
                return ret;

        /* enable wakeup from i.MX UART */
        imx_uart_enable_wakeup(sport, true);

        return 0;
}

static int imx_uart_resume(struct device *dev)
{
        struct imx_port *sport = dev_get_drvdata(dev);

        /* disable wakeup from i.MX UART */
        imx_uart_enable_wakeup(sport, false);

        uart_resume_port(&imx_uart_uart_driver, &sport->port);
        enable_irq(sport->port.irq);

        clk_disable_unprepare(sport->clk_ipg);

        return 0;
}

static int imx_uart_freeze(struct device *dev)
{
        struct imx_port *sport = dev_get_drvdata(dev);

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

        return clk_prepare_enable(sport->clk_ipg);
}

static int imx_uart_thaw(struct device *dev)
{
        struct imx_port *sport = dev_get_drvdata(dev);

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

        clk_disable_unprepare(sport->clk_ipg);

        return 0;
}

static const struct dev_pm_ops imx_uart_pm_ops = {
        .suspend_noirq = imx_uart_suspend_noirq,
        .resume_noirq = imx_uart_resume_noirq,
        .freeze_noirq = imx_uart_suspend_noirq,
        .thaw_noirq = imx_uart_resume_noirq,
        .restore_noirq = imx_uart_resume_noirq,
        .suspend = imx_uart_suspend,
        .resume = imx_uart_resume,
        .freeze = imx_uart_freeze,
        .thaw = imx_uart_thaw,
        .restore = imx_uart_thaw,
};

static struct platform_driver imx_uart_platform_driver = {
        .probe = imx_uart_probe,
        .remove = imx_uart_remove,

        .driver = {
                .name = "imx-uart",
                .of_match_table = imx_uart_dt_ids,
                .pm = &imx_uart_pm_ops,
        },
};

static int __init imx_uart_init(void)
{
        int ret = uart_register_driver(&imx_uart_uart_driver);

        if (ret)
                return ret;

        ret = platform_driver_register(&imx_uart_platform_driver);
        if (ret != 0)
                uart_unregister_driver(&imx_uart_uart_driver);

        return ret;
}

static void __exit imx_uart_exit(void)
{
        platform_driver_unregister(&imx_uart_platform_driver);
        uart_unregister_driver(&imx_uart_uart_driver);
}

module_init(imx_uart_init);
module_exit(imx_uart_exit);

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