IMX6 RS485 驱动移植

阳光穿透心脏的1/2处 2022-01-12 18:37 636阅读 0赞

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1、修改设备树中对应串口设备节点属性，以uart4、使能引脚gpio1\_14为例：

&uart4 \{

pinctrl-names = "default";

pinctrl-0 = <&pinctrl\_uart4  &pinctrl\_uart4\_txen>;

dmas = <>;

dma-names = "";

fsl,rs485-gpio-txen = <&gpio1 14 0>;

status = "okay";

\};

2、在节点iomuxc下面增加子节点

pinctrl\_uart4\_txen: uart4\_txengpr \{

fsl,pins = <

MX6UL\_PAD\_JTAG\_TCK\_\_GPIO1\_IO14        0x17059 /\* TXEN \*/

\};

--------------------

直接更换最新官方例程即可， driver/tty/serial/imx.c 官方源码本身支持 RS485，近期提供基于 4.1.15 补丁，针对致远平台进行测试

// 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/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/pinctrl/consumer.h>
    #include <linux/rational.h>
    #include <linux/slab.h>
    #include <linux/of.h>
    #include <linux/of_device.h>
    #include <linux/io.h>
    #include <linux/dma-mapping.h>
    
    #include <asm/irq.h>
    #include <linux/platform_data/serial-imx.h>
    #include <linux/platform_data/dma-imx.h>
    
    #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_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,
    	IMX53_UART,
    	IMX6Q_UART,
    };
    
    /* device type dependent stuff */
    struct imx_uart_data {
    	unsigned uts_reg;
    	enum imx_uart_type devtype;
    };
    
    struct imx_port {
    	struct uart_port	port;
    	struct timer_list	timer;
    	unsigned int		old_status;
    	unsigned int		have_rtscts:1;
    	unsigned int		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;
    
    	/* shadow registers */
    	unsigned int ucr1;
    	unsigned int ucr2;
    	unsigned int ucr3;
    	unsigned int ucr4;
    	unsigned int ufcr;
    
    	/* 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_periods;
    	dma_cookie_t		rx_cookie;
    	unsigned int		tx_bytes;
    	unsigned int		dma_tx_nents;
    	unsigned int            saved_reg[10];
    	bool			context_saved;
    };
    
    struct imx_port_ucrs {
    	unsigned int	ucr1;
    	unsigned int	ucr2;
    	unsigned int	ucr3;
    };
    
    static struct imx_uart_data imx_uart_devdata[] = {
    	[IMX1_UART] = {
    		.uts_reg = IMX1_UTS,
    		.devtype = IMX1_UART,
    	},
    	[IMX21_UART] = {
    		.uts_reg = IMX21_UTS,
    		.devtype = IMX21_UART,
    	},
    	[IMX53_UART] = {
    		.uts_reg = IMX21_UTS,
    		.devtype = IMX53_UART,
    	},
    	[IMX6Q_UART] = {
    		.uts_reg = IMX21_UTS,
    		.devtype = IMX6Q_UART,
    	},
    };
    
    static const struct platform_device_id imx_uart_devtype[] = {
    	{
    		.name = "imx1-uart",
    		.driver_data = (kernel_ulong_t) &imx_uart_devdata[IMX1_UART],
    	}, {
    		.name = "imx21-uart",
    		.driver_data = (kernel_ulong_t) &imx_uart_devdata[IMX21_UART],
    	}, {
    		.name = "imx53-uart",
    		.driver_data = (kernel_ulong_t) &imx_uart_devdata[IMX53_UART],
    	}, {
    		.name = "imx6q-uart",
    		.driver_data = (kernel_ulong_t) &imx_uart_devdata[IMX6Q_UART],
    	}, {
    		/* sentinel */
    	}
    };
    MODULE_DEVICE_TABLE(platform, imx_uart_devtype);
    
    static const struct of_device_id imx_uart_dt_ids[] = {
    	{ .compatible = "fsl,imx6q-uart", .data = &imx_uart_devdata[IMX6Q_UART], },
    	{ .compatible = "fsl,imx53-uart", .data = &imx_uart_devdata[IMX53_UART], },
    	{ .compatible = "fsl,imx1-uart", .data = &imx_uart_devdata[IMX1_UART], },
    	{ .compatible = "fsl,imx21-uart", .data = &imx_uart_devdata[IMX21_UART], },
    	{ /* sentinel */ }
    };
    MODULE_DEVICE_TABLE(of, imx_uart_dt_ids);
    
    static void imx_uart_writel(struct imx_port *sport, u32 val, u32 offset)
    {
    	switch (offset) {
    	case UCR1:
    		sport->ucr1 = val;
    		break;
    	case UCR2:
    		sport->ucr2 = val;
    		break;
    	case UCR3:
    		sport->ucr3 = val;
    		break;
    	case UCR4:
    		sport->ucr4 = val;
    		break;
    	case UFCR:
    		sport->ufcr = val;
    		break;
    	default:
    		break;
    	}
    	writel(val, sport->port.membase + offset);
    }
    
    static u32 imx_uart_readl(struct imx_port *sport, u32 offset)
    {
    	switch (offset) {
    	case UCR1:
    		return sport->ucr1;
    		break;
    	case UCR2:
    		/*
    		 * UCR2_SRST is the only bit in the cached registers that might
    		 * differ from the value that was last written. As it only
    		 * automatically becomes one after being cleared, reread
    		 * conditionally.
    		 */
    		if (!(sport->ucr2 & UCR2_SRST))
    			sport->ucr2 = readl(sport->port.membase + offset);
    		return sport->ucr2;
    		break;
    	case UCR3:
    		return sport->ucr3;
    		break;
    	case UCR4:
    		return sport->ucr4;
    		break;
    	case UFCR:
    		return sport->ufcr;
    		break;
    	default:
    		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;
    }
    
    static inline int imx_uart_is_imx21(struct imx_port *sport)
    {
    	return sport->devdata->devtype == IMX21_UART;
    }
    
    static inline int imx_uart_is_imx53(struct imx_port *sport)
    {
    	return sport->devdata->devtype == IMX53_UART;
    }
    
    static inline int imx_uart_is_imx6q(struct imx_port *sport)
    {
    	return sport->devdata->devtype == IMX6Q_UART;
    }
    /*
     * Save and restore functions for UCR1, UCR2 and UCR3 registers
     */
    #if defined(CONFIG_SERIAL_IMX_CONSOLE)
    static void imx_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);
    
    	sport->port.mctrl |= TIOCM_RTS;
    	mctrl_gpio_set(sport->gpios, sport->port.mctrl);
    }
    
    /* 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;
    
    	sport->port.mctrl &= ~TIOCM_RTS;
    	mctrl_gpio_set(sport->gpios, sport->port.mctrl);
    }
    
    /* called with port.lock taken and irqs off */
    static void imx_uart_start_rx(struct uart_port *port)
    {
    	struct imx_port *sport = (struct 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);
    }
    
    /* called with port.lock taken and irqs off */
    static void imx_uart_stop_tx(struct uart_port *port)
    {
    	struct imx_port *sport = (struct imx_port *)port;
    	u32 ucr1;
    
    	/*
    	 * 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);
    
    	/* in rs485 mode disable transmitter if shifter is empty */
    	if (port->rs485.flags & SER_RS485_ENABLED &&
    	    imx_uart_readl(sport, USR2) & USR2_TXDC) {
    		u32 ucr2 = imx_uart_readl(sport, UCR2), ucr4;
    		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);
    
    		imx_uart_start_rx(port);
    
    		ucr4 = imx_uart_readl(sport, UCR4);
    		ucr4 &= ~UCR4_TCEN;
    		imx_uart_writel(sport, ucr4, UCR4);
    	}
    }
    
    /* called with port.lock taken and irqs off */
    static void imx_uart_stop_rx(struct uart_port *port)
    {
    	struct imx_port *sport = (struct imx_port *)port;
    	u32 ucr1, ucr2;
    
    	ucr1 = imx_uart_readl(sport, UCR1);
    	ucr2 = imx_uart_readl(sport, UCR2);
    
    	if (sport->dma_is_enabled) {
    		ucr1 &= ~(UCR1_RXDMAEN | UCR1_ATDMAEN);
    	} else {
    		ucr1 &= ~UCR1_RRDYEN;
    		ucr2 &= ~UCR2_ATEN;
    	}
    	imx_uart_writel(sport, ucr1, UCR1);
    
    	ucr2 &= ~UCR2_RXEN;
    	imx_uart_writel(sport, ucr2, UCR2);
    }
    
    /* called with port.lock taken and irqs off */
    static void imx_uart_enable_ms(struct uart_port *port)
    {
    	struct imx_port *sport = (struct 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 circ_buf *xmit = &sport->port.state->xmit;
    
    	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 (uart_circ_empty(xmit) || 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 (!uart_circ_empty(xmit) &&
    	       !(imx_uart_readl(sport, imx_uart_uts_reg(sport)) & UTS_TXFULL)) {
    		/* send xmit->buf[xmit->tail]
    		 * out the port here */
    		imx_uart_writel(sport, xmit->buf[xmit->tail], URTX0);
    		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
    		sport->port.icount.tx++;
    	}
    
    	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
    		uart_write_wakeup(&sport->port);
    
    	if (uart_circ_empty(xmit))
    		imx_uart_stop_tx(&sport->port);
    }
    
    static void imx_uart_dma_tx_callback(void *data)
    {
    	struct imx_port *sport = data;
    	struct scatterlist *sgl = &sport->tx_sgl[0];
    	struct circ_buf *xmit = &sport->port.state->xmit;
    	unsigned long flags;
    	u32 ucr1;
    
    	spin_lock_irqsave(&sport->port.lock, 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);
    
    	/* update the stat */
    	xmit->tail = (xmit->tail + sport->tx_bytes) & (UART_XMIT_SIZE - 1);
    	sport->port.icount.tx += sport->tx_bytes;
    
    	dev_dbg(sport->port.dev, "we finish the TX DMA.\n");
    
    	sport->dma_is_txing = 0;
    
    	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
    		uart_write_wakeup(&sport->port);
    
    	if (!uart_circ_empty(xmit) && !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);
    	}
    
    	spin_unlock_irqrestore(&sport->port.lock, flags);
    }
    
    /* called with port.lock taken and irqs off */
    static void imx_uart_dma_tx(struct imx_port *sport)
    {
    	struct circ_buf *xmit = &sport->port.state->xmit;
    	struct scatterlist *sgl = sport->tx_sgl;
    	struct dma_async_tx_descriptor *desc;
    	struct dma_chan	*chan = sport->dma_chan_tx;
    	struct device *dev = sport->port.dev;
    	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);
    
    	sport->tx_bytes = uart_circ_chars_pending(xmit);
    
    	if (xmit->tail < xmit->head || xmit->head == 0) {
    		sport->dma_tx_nents = 1;
    		sg_init_one(sgl, xmit->buf + xmit->tail, sport->tx_bytes);
    	} else {
    		sport->dma_tx_nents = 2;
    		sg_init_table(sgl, 2);
    		sg_set_buf(sgl, xmit->buf + xmit->tail,
    				UART_XMIT_SIZE - xmit->tail);
    		sg_set_buf(sgl + 1, xmit->buf, xmit->head);
    	}
    
    	ret = dma_map_sg(dev, sgl, sport->dma_tx_nents, DMA_TO_DEVICE);
    	if (ret == 0) {
    		dev_err(dev, "DMA mapping error for TX.\n");
    		return;
    	}
    	desc = dmaengine_prep_slave_sg(chan, sgl, 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 %lu bytes by DMA.\n",
    			uart_circ_chars_pending(xmit));
    
    	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 = (struct imx_port *)port;
    	u32 ucr1;
    
    	if (!sport->port.x_char && uart_circ_empty(&port->state->xmit))
    		return;
    
    	if (port->rs485.flags & SER_RS485_ENABLED) {
    		u32 ucr2;
    
    		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);
    
    		if (!(port->rs485.flags & SER_RS485_RX_DURING_TX))
    			imx_uart_stop_rx(port);
    
    		/*
    		 * 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);
    		}
    	}
    
    	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 (!uart_circ_empty(&port->state->xmit) &&
    		    !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;
    	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;
    
    	spin_lock(&sport->port.lock);
    
    	ret = __imx_uart_rtsint(irq, dev_id);
    
    	spin_unlock(&sport->port.lock);
    
    	return ret;
    }
    
    static irqreturn_t imx_uart_txint(int irq, void *dev_id)
    {
    	struct imx_port *sport = dev_id;
    
    	spin_lock(&sport->port.lock);
    	imx_uart_transmit_buffer(sport);
    	spin_unlock(&sport->port.lock);
    	return IRQ_HANDLED;
    }
    
    static irqreturn_t __imx_uart_rxint(int irq, void *dev_id)
    {
    	struct imx_port *sport = dev_id;
    	unsigned int rx, flg, ignored = 0;
    	struct tty_port *port = &sport->port.state->port;
    
    	while (imx_uart_readl(sport, USR2) & USR2_RDR) {
    		u32 usr2;
    
    		flg = TTY_NORMAL;
    		sport->port.icount.rx++;
    
    		rx = imx_uart_readl(sport, URXD0);
    
    		usr2 = imx_uart_readl(sport, USR2);
    		if (usr2 & USR2_BRCD) {
    			imx_uart_writel(sport, USR2_BRCD, USR2);
    			if (uart_handle_break(&sport->port))
    				continue;
    		}
    
    		if (uart_handle_sysrq_char(&sport->port, (unsigned char)rx))
    			continue;
    
    		if (unlikely(rx & URXD_ERR)) {
    			if (rx & URXD_BRK)
    				sport->port.icount.brk++;
    			else if (rx & URXD_PRERR)
    				sport->port.icount.parity++;
    			else if (rx & URXD_FRMERR)
    				sport->port.icount.frame++;
    			if (rx & URXD_OVRRUN)
    				sport->port.icount.overrun++;
    
    			if (rx & sport->port.ignore_status_mask) {
    				if (++ignored > 100)
    					goto out;
    				continue;
    			}
    
    			rx &= (sport->port.read_status_mask | 0xFF);
    
    			if (rx & URXD_BRK)
    				flg = TTY_BREAK;
    			else if (rx & URXD_PRERR)
    				flg = TTY_PARITY;
    			else if (rx & URXD_FRMERR)
    				flg = TTY_FRAME;
    			if (rx & URXD_OVRRUN)
    				flg = TTY_OVERRUN;
    
    			sport->port.sysrq = 0;
    		}
    
    		if (sport->port.ignore_status_mask & URXD_DUMMY_READ)
    			goto out;
    
    		if (tty_insert_flip_char(port, rx, flg) == 0)
    			sport->port.icount.buf_overrun++;
    	}
    
    out:
    	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;
    
    	spin_lock(&sport->port.lock);
    
    	ret = __imx_uart_rxint(irq, dev_id);
    
    	spin_unlock(&sport->port.lock);
    
    	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.
     */
    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.
     */
    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;
    
    	spin_lock(&sport->port.lock);
    
    	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_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;
    	}
    
    	spin_unlock(&sport->port.lock);
    
    	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 = (struct 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 = (struct 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 = (struct 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 = (struct imx_port *)port;
    	unsigned long flags;
    	u32 ucr1;
    
    	spin_lock_irqsave(&sport->port.lock, flags);
    
    	ucr1 = imx_uart_readl(sport, UCR1) & ~UCR1_SNDBRK;
    
    	if (break_state != 0)
    		ucr1 |= UCR1_SNDBRK;
    
    	imx_uart_writel(sport, ucr1, UCR1);
    
    	spin_unlock_irqrestore(&sport->port.lock, 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 = from_timer(sport, t, timer);
    	unsigned long flags;
    
    	if (sport->port.state) {
    		spin_lock_irqsave(&sport->port.lock, flags);
    		imx_uart_mctrl_check(sport);
    		spin_unlock_irqrestore(&sport->port.lock, 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) {
    		imx_uart_clear_rx_errors(sport);
    		return;
    	}
    
    	if (!(sport->port.ignore_status_mask & URXD_DUMMY_READ)) {
    
    		/*
    		 * 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;
    
    			/* 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);
    	}
    }
    
    /* RX DMA buffer periods */
    #define RX_DMA_PERIODS	16
    #define RX_BUF_SIZE	(RX_DMA_PERIODS * PAGE_SIZE / 4)
    
    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;
    	sport->rx_periods = RX_DMA_PERIODS;
    
    	sg_init_one(sgl, sport->rx_buf, RX_BUF_SIZE);
    	ret = dma_map_sg(dev, sgl, 1, DMA_FROM_DEVICE);
    	if (ret == 0) {
    		dev_err(dev, "DMA mapping error for RX.\n");
    		return -EINVAL;
    	}
    
    	desc = dmaengine_prep_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;
    }
    
    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);
    	}
    
    }
    
    #define TXTL_DEFAULT 2 /* reset default */
    #define RXTL_DEFAULT 1 /* reset default */
    #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;
    	int ret;
    
    	/* Prepare for RX : */
    	sport->dma_chan_rx = dma_request_slave_channel(dev, "rx");
    	if (!sport->dma_chan_rx) {
    		dev_dbg(dev, "cannot get the DMA channel.\n");
    		ret = -EINVAL;
    		goto err;
    	}
    
    	slave_config.direction = DMA_DEV_TO_MEM;
    	slave_config.src_addr = sport->port.mapbase + URXD0;
    	slave_config.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
    	/* 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 = kzalloc(RX_BUF_SIZE, GFP_KERNEL);
    	if (!sport->rx_buf) {
    		ret = -ENOMEM;
    		goto err;
    	}
    	sport->rx_ring.buf = sport->rx_buf;
    
    	/* Prepare for TX : */
    	sport->dma_chan_tx = dma_request_slave_channel(dev, "tx");
    	if (!sport->dma_chan_tx) {
    		dev_err(dev, "cannot get the TX DMA channel!\n");
    		ret = -EINVAL;
    		goto err;
    	}
    
    	slave_config.direction = DMA_MEM_TO_DEV;
    	slave_config.dst_addr = sport->port.mapbase + URTX0;
    	slave_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
    	slave_config.dst_maxburst = TXTL_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;
    }
    
    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, RXTL_DEFAULT);
    
    	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 = (struct imx_port *)port;
    	int retval, i;
    	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;
    	}
    
    	imx_uart_setup_ufcr(sport, TXTL_DEFAULT, RXTL_DEFAULT);
    
    	/* 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)
    		dma_is_inited = 1;
    
    	spin_lock_irqsave(&sport->port.lock, flags);
    	/* Reset fifo's and state machines */
    	i = 100;
    
    	ucr2 = imx_uart_readl(sport, UCR2);
    	ucr2 &= ~UCR2_SRST;
    	imx_uart_writel(sport, ucr2, UCR2);
    
    	while (!(imx_uart_readl(sport, UCR2) & UCR2_SRST) && (--i > 0))
    		udelay(1);
    
    	/*
    	 * 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 (!sport->dma_is_enabled)
    		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);
    	}
    
    	spin_unlock_irqrestore(&sport->port.lock, flags);
    
    	return 0;
    }
    
    static void imx_uart_shutdown(struct uart_port *port)
    {
    	struct imx_port *sport = (struct imx_port *)port;
    	unsigned long flags;
    	u32 ucr1, ucr2, ucr4;
    
    	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;
    		}
    
    		spin_lock_irqsave(&sport->port.lock, flags);
    		imx_uart_stop_tx(port);
    		imx_uart_stop_rx(port);
    		imx_uart_disable_dma(sport);
    		spin_unlock_irqrestore(&sport->port.lock, flags);
    		imx_uart_dma_exit(sport);
    	}
    
    	mctrl_gpio_disable_ms(sport->gpios);
    
    	spin_lock_irqsave(&sport->port.lock, flags);
    	ucr2 = imx_uart_readl(sport, UCR2);
    	ucr2 &= ~(UCR2_TXEN | UCR2_ATEN);
    	imx_uart_writel(sport, ucr2, UCR2);
    
    	ucr4 = imx_uart_readl(sport, UCR4);
    	ucr4 &= ~UCR4_OREN;
    	imx_uart_writel(sport, ucr4, UCR4);
    	spin_unlock_irqrestore(&sport->port.lock, flags);
    
    	/*
    	 * Stop our timer.
    	 */
    	del_timer_sync(&sport->timer);
    
    	/*
    	 * Disable all interrupts, port and break condition.
    	 */
    
    	spin_lock_irqsave(&sport->port.lock, flags);
    	ucr1 = imx_uart_readl(sport, UCR1);
    	ucr1 &= ~(UCR1_TRDYEN | UCR1_RRDYEN | UCR1_RTSDEN | UCR1_UARTEN | UCR1_RXDMAEN | UCR1_ATDMAEN);
    
    	imx_uart_writel(sport, ucr1, UCR1);
    	spin_unlock_irqrestore(&sport->port.lock, 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 = (struct imx_port *)port;
    	struct scatterlist *sgl = &sport->tx_sgl[0];
    	u32 ucr2;
    	int i = 100, ubir, ubmr, uts;
    
    	if (!sport->dma_chan_tx)
    		return;
    
    	sport->tx_bytes = 0;
    	dmaengine_terminate_all(sport->dma_chan_tx);
    	if (sport->dma_is_txing) {
    		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;
    	}
    
    	/*
    	 * 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);
    	ucr2 &= ~UCR2_SRST;
    	imx_uart_writel(sport, ucr2, 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);
    }
    
    static void
    imx_uart_set_termios(struct uart_port *port, struct ktermios *termios,
    		     struct ktermios *old)
    {
    	struct imx_port *sport = (struct 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;
    	}
    
    	del_timer_sync(&sport->timer);
    
    	/*
    	 * Ask the core to calculate the divisor for us.
    	 */
    	baud = uart_get_baud_rate(port, termios, old, 50, port->uartclk / 16);
    	quot = uart_get_divisor(port, baud);
    
    	spin_lock_irqsave(&sport->port.lock, flags);
    
    	/*
    	 * 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);
    
    	spin_unlock_irqrestore(&sport->port.lock, flags);
    }
    
    static const char *imx_uart_type(struct uart_port *port)
    {
    	struct imx_port *sport = (struct imx_port *)port;
    
    	return sport->port.type == PORT_IMX ? "IMX" : NULL;
    }
    
    /*
     * Configure/autoconfigure the port.
     */
    static void imx_uart_config_port(struct uart_port *port, int flags)
    {
    	struct imx_port *sport = (struct imx_port *)port;
    
    	if (flags & UART_CONFIG_TYPE)
    		sport->port.type = PORT_IMX;
    }
    
    /*
     * Verify the new serial_struct (for TIOCSSERIAL).
     * The only change we allow are to the flags and type, and
     * even then only between PORT_IMX and PORT_UNKNOWN
     */
    static int
    imx_uart_verify_port(struct uart_port *port, struct serial_struct *ser)
    {
    	struct imx_port *sport = (struct imx_port *)port;
    	int ret = 0;
    
    	if (ser->type != PORT_UNKNOWN && ser->type != PORT_IMX)
    		ret = -EINVAL;
    	if (sport->port.irq != ser->irq)
    		ret = -EINVAL;
    	if (ser->io_type != UPIO_MEM)
    		ret = -EINVAL;
    	if (sport->port.uartclk / 16 != ser->baud_base)
    		ret = -EINVAL;
    	if (sport->port.mapbase != (unsigned long)ser->iomem_base)
    		ret = -EINVAL;
    	if (sport->port.iobase != ser->port)
    		ret = -EINVAL;
    	if (ser->hub6 != 0)
    		ret = -EINVAL;
    	return ret;
    }
    
    #if defined(CONFIG_CONSOLE_POLL)
    
    static int imx_uart_poll_init(struct uart_port *port)
    {
    	struct imx_port *sport = (struct 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, RXTL_DEFAULT);
    
    	spin_lock_irqsave(&sport->port.lock, 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 &= ~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);
    
    	spin_unlock_irqrestore(&sport->port.lock, flags);
    
    	return 0;
    }
    
    static int imx_uart_poll_get_char(struct uart_port *port)
    {
    	struct imx_port *sport = (struct 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 = (struct 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 serial_rs485 *rs485conf)
    {
    	struct imx_port *sport = (struct imx_port *)port;
    	u32 ucr2;
    
    	/* unimplemented */
    	rs485conf->delay_rts_before_send = 0;
    	rs485conf->delay_rts_after_send = 0;
    
    	/* RTS is required to control the transmitter */
    	if (!sport->have_rtscts && !sport->have_rtsgpio)
    		rs485conf->flags &= ~SER_RS485_ENABLED;
    
    	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)
    		imx_uart_start_rx(port);
    
    	port->rs485 = *rs485conf;
    
    	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];
    
    #ifdef CONFIG_SERIAL_IMX_CONSOLE
    static void imx_uart_console_putchar(struct uart_port *port, int ch)
    {
    	struct imx_port *sport = (struct imx_port *)port;
    
    	while (imx_uart_readl(sport, imx_uart_uts_reg(sport)) & UTS_TXFULL)
    		barrier();
    
    	imx_uart_writel(sport, ch, URTX0);
    }
    
    /*
     * Interrupts are disabled on entering
     */
    static void
    imx_uart_console_write(struct console *co, const char *s, unsigned int count)
    {
    	struct imx_port *sport = imx_uart_ports[co->index];
    	struct imx_port_ucrs old_ucr;
    	unsigned int ucr1;
    	unsigned long flags = 0;
    	int locked = 1;
    	int retval;
    
    	retval = clk_enable(sport->clk_per);
    	if (retval)
    		return;
    	retval = clk_enable(sport->clk_ipg);
    	if (retval) {
    		clk_disable(sport->clk_per);
    		return;
    	}
    
    	if (sport->port.sysrq)
    		locked = 0;
    	else if (oops_in_progress)
    		locked = spin_trylock_irqsave(&sport->port.lock, flags);
    	else
    		spin_lock_irqsave(&sport->port.lock, flags);
    
    	/*
    	 *	First, save UCR1/2/3 and then disable interrupts
    	 */
    	imx_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);
    
    	uart_console_write(&sport->port, s, count, imx_uart_console_putchar);
    
    	/*
    	 *	Finally, wait for transmitter to become empty
    	 *	and restore UCR1/2/3
    	 */
    	while (!(imx_uart_readl(sport, USR2) & USR2_TXDC));
    
    	imx_uart_ucrs_restore(sport, &old_ucr);
    
    	if (locked)
    		spin_unlock_irqrestore(&sport->port.lock, flags);
    
    	clk_disable(sport->clk_ipg);
    	clk_disable(sport->clk_per);
    }
    
    /*
     * If the port was already initialised (eg, by a boot loader),
     * try to determine the current setup.
     */
    static void __init
    imx_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 __init
    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;
    
    	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, RXTL_DEFAULT);
    
    	retval = uart_set_options(&sport->port, co, baud, parity, bits, flow);
    
    	clk_disable(sport->clk_ipg);
    	if (retval) {
    		clk_unprepare(sport->clk_ipg);
    		goto error_console;
    	}
    
    	retval = clk_prepare(sport->clk_per);
    	if (retval)
    		clk_unprepare(sport->clk_ipg);
    
    error_console:
    	return retval;
    }
    
    static struct uart_driver imx_uart_uart_driver;
    static struct console imx_uart_console = {
    	.name		= DEV_NAME,
    	.write		= imx_uart_console_write,
    	.device		= uart_console_device,
    	.setup		= imx_uart_console_setup,
    	.flags		= CON_PRINTBUFFER,
    	.index		= -1,
    	.data		= &imx_uart_uart_driver,
    };
    
    #define IMX_CONSOLE	&imx_uart_console
    
    #ifdef CONFIG_OF
    static void imx_uart_console_early_putchar(struct uart_port *port, int ch)
    {
    	struct imx_port *sport = (struct imx_port *)port;
    
    	while (imx_uart_readl(sport, IMX21_UTS) & UTS_TXFULL)
    		cpu_relax();
    
    	imx_uart_writel(sport, ch, URTX0);
    }
    
    static void imx_uart_console_early_write(struct console *con, const char *s,
    					 unsigned count)
    {
    	struct earlycon_device *dev = con->data;
    
    	uart_console_write(&dev->port, s, count, imx_uart_console_early_putchar);
    }
    
    static int __init
    imx_console_early_setup(struct earlycon_device *dev, const char *opt)
    {
    	if (!dev->port.membase)
    		return -ENODEV;
    
    	dev->con->write = imx_uart_console_early_write;
    
    	return 0;
    }
    OF_EARLYCON_DECLARE(ec_imx6q, "fsl,imx6q-uart", imx_console_early_setup);
    OF_EARLYCON_DECLARE(ec_imx21, "fsl,imx21-uart", imx_console_early_setup);
    #endif
    
    #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,
    };
    
    #ifdef CONFIG_OF
    /*
     * This function returns 1 iff pdev isn't a device instatiated by dt, 0 iff it
     * could successfully get all information from dt or a negative errno.
     */
    static int imx_uart_probe_dt(struct imx_port *sport,
    			     struct platform_device *pdev)
    {
    	struct device_node *np = pdev->dev.of_node;
    	int ret;
    
    	sport->devdata = of_device_get_match_data(&pdev->dev);
    	if (!sport->devdata)
    		/* no device tree device */
    		return 1;
    
    	ret = of_alias_get_id(np, "serial");
    	if (ret < 0) {
    		dev_err(&pdev->dev, "failed to get alias id, errno %d\n", ret);
    		return ret;
    	}
    	sport->port.line = ret;
    
    	if (of_get_property(np, "uart-has-rtscts", NULL) ||
    	    of_get_property(np, "fsl,uart-has-rtscts", NULL) /* deprecated */)
    		sport->have_rtscts = 1;
    
    	if (of_get_property(np, "fsl,dte-mode", NULL))
    		sport->dte_mode = 1;
    
    	if (of_get_property(np, "rts-gpios", NULL))
    		sport->have_rtsgpio = 1;
    
    	if (of_get_property(np, "fsl,inverted-tx", NULL))
    		sport->inverted_tx = 1;
    
    	if (of_get_property(np, "fsl,inverted-rx", NULL))
    		sport->inverted_rx = 1;
    
    	return 0;
    }
    #else
    static inline int imx_uart_probe_dt(struct imx_port *sport,
    				    struct platform_device *pdev)
    {
    	return 1;
    }
    #endif
    
    static void imx_uart_probe_pdata(struct imx_port *sport,
    				 struct platform_device *pdev)
    {
    	struct imxuart_platform_data *pdata = dev_get_platdata(&pdev->dev);
    
    	sport->port.line = pdev->id;
    	sport->devdata = (struct imx_uart_data	*) pdev->id_entry->driver_data;
    
    	if (!pdata)
    		return;
    
    	if (pdata->flags & IMXUART_HAVE_RTSCTS)
    		sport->have_rtscts = 1;
    }
    
    static int imx_uart_probe(struct platform_device *pdev)
    {
    	struct imx_port *sport;
    	void __iomem *base;
    	int ret = 0;
    	u32 ucr1;
    	struct resource *res;
    	int txirq, rxirq, rtsirq;
    
    	sport = devm_kzalloc(&pdev->dev, sizeof(*sport), GFP_KERNEL);
    	if (!sport)
    		return -ENOMEM;
    
    	ret = imx_uart_probe_dt(sport, pdev);
    	if (ret > 0)
    		imx_uart_probe_pdata(sport, pdev);
    	else if (ret < 0)
    		return ret;
    
    	if (sport->port.line >= ARRAY_SIZE(imx_uart_ports)) {
    		dev_err(&pdev->dev, "serial%d out of range\n",
    			sport->port.line);
    		return -EINVAL;
    	}
    
    	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    	base = devm_ioremap_resource(&pdev->dev, res);
    	if (IS_ERR(base))
    		return PTR_ERR(base);
    
    	rxirq = platform_get_irq(pdev, 0);
    	txirq = platform_get_irq_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;
    	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 per clk: %d\n", ret);
    		return ret;
    	}
    
    	/* initialize shadow register values */
    	sport->ucr1 = readl(sport->port.membase + UCR1);
    	sport->ucr2 = readl(sport->port.membase + UCR2);
    	sport->ucr3 = readl(sport->port.membase + UCR3);
    	sport->ucr4 = readl(sport->port.membase + UCR4);
    	sport->ufcr = readl(sport->port.membase + UFCR);
    
    	uart_get_rs485_mode(&pdev->dev, &sport->port.rs485);
    
    	if (sport->port.rs485.flags & SER_RS485_ENABLED &&
    	    (!sport->have_rtscts && !sport->have_rtsgpio))
    		dev_err(&pdev->dev, "no RTS control, disabling rs485\n");
    
    	/*
    	 * 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");
    
    	imx_uart_rs485_config(&sport->port, &sport->port.rs485);
    
    	/* Disable interrupts before requesting them */
    	ucr1 = imx_uart_readl(sport, UCR1);
    	ucr1 &= ~(UCR1_ADEN | UCR1_TRDYEN | UCR1_IDEN | UCR1_RRDYEN |
    		 UCR1_TRDYEN | UCR1_RTSDEN);
    	imx_uart_writel(sport, ucr1, UCR1);
    
    	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);
    	}
    
    	clk_disable_unprepare(sport->clk_ipg);
    
    	/*
    	 * 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);
    			return ret;
    		}
    
    		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);
    			return ret;
    		}
    
    		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);
    			return ret;
    		}
    	} 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);
    			return ret;
    		}
    	}
    
    	imx_uart_ports[sport->port.line] = sport;
    
    	platform_set_drvdata(pdev, sport);
    
    	return uart_add_one_port(&imx_uart_uart_driver, &sport->port);
    }
    
    static int imx_uart_remove(struct platform_device *pdev)
    {
    	struct imx_port *sport = platform_get_drvdata(pdev);
    
    	return uart_remove_one_port(&imx_uart_uart_driver, &sport->port);
    }
    
    static void imx_uart_restore_context(struct imx_port *sport)
    {
    	unsigned long flags;
    
    	spin_lock_irqsave(&sport->port.lock, flags);
    	if (!sport->context_saved) {
    		spin_unlock_irqrestore(&sport->port.lock, 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;
    	spin_unlock_irqrestore(&sport->port.lock, flags);
    }
    
    static void imx_uart_save_context(struct imx_port *sport)
    {
    	unsigned long flags;
    
    	/* Save necessary regs */
    	spin_lock_irqsave(&sport->port.lock, 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;
    	spin_unlock_irqrestore(&sport->port.lock, flags);
    }
    
    static void imx_uart_enable_wakeup(struct imx_port *sport, bool on)
    {
    	u32 ucr3;
    
    	ucr3 = imx_uart_readl(sport, UCR3);
    	if (on) {
    		imx_uart_writel(sport, USR1_AWAKE, USR1);
    		ucr3 |= UCR3_AWAKEN;
    	} else {
    		ucr3 &= ~UCR3_AWAKEN;
    	}
    	imx_uart_writel(sport, ucr3, UCR3);
    
    	if (sport->have_rtscts) {
    		u32 ucr1 = imx_uart_readl(sport, UCR1);
    		if (on)
    			ucr1 |= UCR1_RTSDEN;
    		else
    			ucr1 &= ~UCR1_RTSDEN;
    		imx_uart_writel(sport, ucr1, UCR1);
    	}
    }
    
    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,
    	.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,
    
    	.id_table = imx_uart_devtype,
    	.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");

[Link 1]: http://www.openedv.com/thread-13912-1-1.html