// SPDX-License-Identifier: GPL-2.0+
/*
 * Application UART driver for:
 *      Freescale STMP37XX/STMP378X
 *      Alphascale ASM9260
 *
 * Author: dmitry pervushin <dimka@embeddedalley.com>
 *
 * Copyright 2014 Oleksij Rempel <linux@rempel-privat.de>
 *      Provide Alphascale ASM9260 support.
 * Copyright 2008-2010 Freescale Semiconductor, Inc.
 * Copyright 2008 Embedded Alley Solutions, Inc All Rights Reserved.
 */

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/wait.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/tty_flip.h>
#include <linux/serial.h>
#include <linux/serial_core.h>
#include <linux/platform_device.h>
#include <linux/device.h>
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/of_device.h>
#include <linux/dma-mapping.h>
#include <linux/dmaengine.h>

#include <asm/cacheflush.h>

#include <linux/gpio/consumer.h>
#include <linux/err.h>
#include <linux/irq.h>
#include "serial_mctrl_gpio.h"

#define MXS_AUART_PORTS 5
#define MXS_AUART_FIFO_SIZE             16

#define SET_REG                         0x4
#define CLR_REG                         0x8
#define TOG_REG                         0xc

#define AUART_CTRL0                     0x00000000
#define AUART_CTRL1                     0x00000010
#define AUART_CTRL2                     0x00000020
#define AUART_LINECTRL                  0x00000030
#define AUART_LINECTRL2                 0x00000040
#define AUART_INTR                      0x00000050
#define AUART_DATA                      0x00000060
#define AUART_STAT                      0x00000070
#define AUART_DEBUG                     0x00000080
#define AUART_VERSION                   0x00000090
#define AUART_AUTOBAUD                  0x000000a0

#define AUART_CTRL0_SFTRST                      (1 << 31)
#define AUART_CTRL0_CLKGATE                     (1 << 30)
#define AUART_CTRL0_RXTO_ENABLE                 (1 << 27)
#define AUART_CTRL0_RXTIMEOUT(v)                (((v) & 0x7ff) << 16)
#define AUART_CTRL0_XFER_COUNT(v)               ((v) & 0xffff)

#define AUART_CTRL1_XFER_COUNT(v)               ((v) & 0xffff)

#define AUART_CTRL2_DMAONERR                    (1 << 26)
#define AUART_CTRL2_TXDMAE                      (1 << 25)
#define AUART_CTRL2_RXDMAE                      (1 << 24)

#define AUART_CTRL2_CTSEN                       (1 << 15)
#define AUART_CTRL2_RTSEN                       (1 << 14)
#define AUART_CTRL2_RTS                         (1 << 11)
#define AUART_CTRL2_RXE                         (1 << 9)
#define AUART_CTRL2_TXE                         (1 << 8)
#define AUART_CTRL2_UARTEN                      (1 << 0)

#define AUART_LINECTRL_BAUD_DIV_MAX             0x003fffc0
#define AUART_LINECTRL_BAUD_DIV_MIN             0x000000ec
#define AUART_LINECTRL_BAUD_DIVINT_SHIFT        16
#define AUART_LINECTRL_BAUD_DIVINT_MASK         0xffff0000
#define AUART_LINECTRL_BAUD_DIVINT(v)           (((v) & 0xffff) << 16)
#define AUART_LINECTRL_BAUD_DIVFRAC_SHIFT       8
#define AUART_LINECTRL_BAUD_DIVFRAC_MASK        0x00003f00
#define AUART_LINECTRL_BAUD_DIVFRAC(v)          (((v) & 0x3f) << 8)
#define AUART_LINECTRL_SPS                      (1 << 7)
#define AUART_LINECTRL_WLEN_MASK                0x00000060
#define AUART_LINECTRL_WLEN(v)                  (((v) & 0x3) << 5)
#define AUART_LINECTRL_FEN                      (1 << 4)
#define AUART_LINECTRL_STP2                     (1 << 3)
#define AUART_LINECTRL_EPS                      (1 << 2)
#define AUART_LINECTRL_PEN                      (1 << 1)
#define AUART_LINECTRL_BRK                      (1 << 0)

#define AUART_INTR_RTIEN                        (1 << 22)
#define AUART_INTR_TXIEN                        (1 << 21)
#define AUART_INTR_RXIEN                        (1 << 20)
#define AUART_INTR_CTSMIEN                      (1 << 17)
#define AUART_INTR_RTIS                         (1 << 6)
#define AUART_INTR_TXIS                         (1 << 5)
#define AUART_INTR_RXIS                         (1 << 4)
#define AUART_INTR_CTSMIS                       (1 << 1)

#define AUART_STAT_BUSY                         (1 << 29)
#define AUART_STAT_CTS                          (1 << 28)
#define AUART_STAT_TXFE                         (1 << 27)
#define AUART_STAT_TXFF                         (1 << 25)
#define AUART_STAT_RXFE                         (1 << 24)
#define AUART_STAT_OERR                         (1 << 19)
#define AUART_STAT_BERR                         (1 << 18)
#define AUART_STAT_PERR                         (1 << 17)
#define AUART_STAT_FERR                         (1 << 16)
#define AUART_STAT_RXCOUNT_MASK                 0xffff

/*
 * Start of Alphascale asm9260 defines
 * This list contains only differences of existing bits
 * between imx2x and asm9260
 */
#define ASM9260_HW_CTRL0                        0x0000
/*
 * RW. Tell the UART to execute the RX DMA Command. The
 * UART will clear this bit at the end of receive execution.
 */
#define ASM9260_BM_CTRL0_RXDMA_RUN              BIT(28)
/* RW. 0 use FIFO for status register; 1 use DMA */
#define ASM9260_BM_CTRL0_RXTO_SOURCE_STATUS     BIT(25)
/*
 * RW. RX TIMEOUT Enable. Valid for FIFO and DMA.
 * Warning: If this bit is set to 0, the RX timeout will not affect receive DMA
 * operation. If this bit is set to 1, a receive timeout will cause the receive
 * DMA logic to terminate by filling the remaining DMA bytes with garbage data.
 */
#define ASM9260_BM_CTRL0_RXTO_ENABLE            BIT(24)
/*
 * RW. Receive Timeout Counter Value: number of 8-bit-time to wait before
 * asserting timeout on the RX input. If the RXFIFO is not empty and the RX
 * input is idle, then the watchdog counter will decrement each bit-time. Note
 * 7-bit-time is added to the programmed value, so a value of zero will set
 * the counter to 7-bit-time, a value of 0x1 gives 15-bit-time and so on. Also
 * note that the counter is reloaded at the end of each frame, so if the frame
 * is 10 bits long and the timeout counter value is zero, then timeout will
 * occur (when FIFO is not empty) even if the RX input is not idle. The default
 * value is 0x3 (31 bit-time).
 */
#define ASM9260_BM_CTRL0_RXTO_MASK              (0xff << 16)
/* TIMEOUT = (100*7+1)*(1/BAUD) */
#define ASM9260_BM_CTRL0_DEFAULT_RXTIMEOUT      (20 << 16)

/* TX ctrl register */
#define ASM9260_HW_CTRL1                        0x0010
/*
 * RW. Tell the UART to execute the TX DMA Command. The
 * UART will clear this bit at the end of transmit execution.
 */
#define ASM9260_BM_CTRL1_TXDMA_RUN              BIT(28)

#define ASM9260_HW_CTRL2                        0x0020
/*
 * RW. Receive Interrupt FIFO Level Select.
 * The trigger points for the receive interrupt are as follows:
 * ONE_EIGHTHS = 0x0 Trigger on FIFO full to at least 2 of 16 entries.
 * ONE_QUARTER = 0x1 Trigger on FIFO full to at least 4 of 16 entries.
 * ONE_HALF = 0x2 Trigger on FIFO full to at least 8 of 16 entries.
 * THREE_QUARTERS = 0x3 Trigger on FIFO full to at least 12 of 16 entries.
 * SEVEN_EIGHTHS = 0x4 Trigger on FIFO full to at least 14 of 16 entries.
 */
#define ASM9260_BM_CTRL2_RXIFLSEL               (7 << 20)
#define ASM9260_BM_CTRL2_DEFAULT_RXIFLSEL       (3 << 20)
/* RW. Same as RXIFLSEL */
#define ASM9260_BM_CTRL2_TXIFLSEL               (7 << 16)
#define ASM9260_BM_CTRL2_DEFAULT_TXIFLSEL       (2 << 16)
/* RW. Set DTR. When this bit is 1, the output is 0. */
#define ASM9260_BM_CTRL2_DTR                    BIT(10)
/* RW. Loop Back Enable */
#define ASM9260_BM_CTRL2_LBE                    BIT(7)
#define ASM9260_BM_CTRL2_PORT_ENABLE            BIT(0)

#define ASM9260_HW_LINECTRL                     0x0030
/*
 * RW. Stick Parity Select. When bits 1, 2, and 7 of this register are set, the
 * parity bit is transmitted and checked as a 0. When bits 1 and 7 are set,
 * and bit 2 is 0, the parity bit is transmitted and checked as a 1. When this
 * bit is cleared stick parity is disabled.
 */
#define ASM9260_BM_LCTRL_SPS                    BIT(7)
/* RW. Word length */
#define ASM9260_BM_LCTRL_WLEN                   (3 << 5)
#define ASM9260_BM_LCTRL_CHRL_5                 (0 << 5)
#define ASM9260_BM_LCTRL_CHRL_6                 (1 << 5)
#define ASM9260_BM_LCTRL_CHRL_7                 (2 << 5)
#define ASM9260_BM_LCTRL_CHRL_8                 (3 << 5)

/*
 * Interrupt register.
 * contains the interrupt enables and the interrupt status bits
 */
#define ASM9260_HW_INTR                         0x0040
/* Tx FIFO EMPTY Raw Interrupt enable */
#define ASM9260_BM_INTR_TFEIEN                  BIT(27)
/* Overrun Error Interrupt Enable. */
#define ASM9260_BM_INTR_OEIEN                   BIT(26)
/* Break Error Interrupt Enable. */
#define ASM9260_BM_INTR_BEIEN                   BIT(25)
/* Parity Error Interrupt Enable. */
#define ASM9260_BM_INTR_PEIEN                   BIT(24)
/* Framing Error Interrupt Enable. */
#define ASM9260_BM_INTR_FEIEN                   BIT(23)

/* nUARTDSR Modem Interrupt Enable. */
#define ASM9260_BM_INTR_DSRMIEN                 BIT(19)
/* nUARTDCD Modem Interrupt Enable. */
#define ASM9260_BM_INTR_DCDMIEN                 BIT(18)
/* nUARTRI Modem Interrupt Enable. */
#define ASM9260_BM_INTR_RIMIEN                  BIT(16)
/* Auto-Boud Timeout */
#define ASM9260_BM_INTR_ABTO                    BIT(13)
#define ASM9260_BM_INTR_ABEO                    BIT(12)
/* Tx FIFO EMPTY Raw Interrupt state */
#define ASM9260_BM_INTR_TFEIS                   BIT(11)
/* Overrun Error */
#define ASM9260_BM_INTR_OEIS                    BIT(10)
/* Break Error */
#define ASM9260_BM_INTR_BEIS                    BIT(9)
/* Parity Error */
#define ASM9260_BM_INTR_PEIS                    BIT(8)
/* Framing Error */
#define ASM9260_BM_INTR_FEIS                    BIT(7)
#define ASM9260_BM_INTR_DSRMIS                  BIT(3)
#define ASM9260_BM_INTR_DCDMIS                  BIT(2)
#define ASM9260_BM_INTR_RIMIS                   BIT(0)

/*
 * RW. In DMA mode, up to 4 Received/Transmit characters can be accessed at a
 * time. In PIO mode, only one character can be accessed at a time. The status
 * register contains the receive data flags and valid bits.
 */
#define ASM9260_HW_DATA                         0x0050

#define ASM9260_HW_STAT                         0x0060
/* RO. If 1, UARTAPP is present in this product. */
#define ASM9260_BM_STAT_PRESENT                 BIT(31)
/* RO. If 1, HISPEED is present in this product. */
#define ASM9260_BM_STAT_HISPEED                 BIT(30)
/* RO. Receive FIFO Full. */
#define ASM9260_BM_STAT_RXFULL                  BIT(26)

/* RO. The UART Debug Register contains the state of the DMA signals. */
#define ASM9260_HW_DEBUG                        0x0070
/* DMA Command Run Status */
#define ASM9260_BM_DEBUG_TXDMARUN               BIT(5)
#define ASM9260_BM_DEBUG_RXDMARUN               BIT(4)
/* DMA Command End Status */
#define ASM9260_BM_DEBUG_TXCMDEND               BIT(3)
#define ASM9260_BM_DEBUG_RXCMDEND               BIT(2)
/* DMA Request Status */
#define ASM9260_BM_DEBUG_TXDMARQ                BIT(1)
#define ASM9260_BM_DEBUG_RXDMARQ                BIT(0)

#define ASM9260_HW_ILPR                         0x0080

#define ASM9260_HW_RS485CTRL                    0x0090
/*
 * RW. This bit reverses the polarity of the direction control signal on the RTS
 * (or DTR) pin.
 * If 0, The direction control pin will be driven to logic ‘0’ when the
 * transmitter has data to be sent. It will be driven to logic ‘1’ after the
 * last bit of data has been transmitted.
 */
#define ASM9260_BM_RS485CTRL_ONIV               BIT(5)
/* RW. Enable Auto Direction Control. */
#define ASM9260_BM_RS485CTRL_DIR_CTRL           BIT(4)
/*
 * RW. If 0 and DIR_CTRL = 1, pin RTS is used for direction control.
 * If 1 and DIR_CTRL = 1, pin DTR is used for direction control.
 */
#define ASM9260_BM_RS485CTRL_PINSEL             BIT(3)
/* RW. Enable Auto Address Detect (AAD). */
#define ASM9260_BM_RS485CTRL_AADEN              BIT(2)
/* RW. Disable receiver. */
#define ASM9260_BM_RS485CTRL_RXDIS              BIT(1)
/* RW. Enable RS-485/EIA-485 Normal Multidrop Mode (NMM) */
#define ASM9260_BM_RS485CTRL_RS485EN            BIT(0)

#define ASM9260_HW_RS485ADRMATCH                0x00a0
/* Contains the address match value. */
#define ASM9260_BM_RS485ADRMATCH_MASK           (0xff << 0)

#define ASM9260_HW_RS485DLY                     0x00b0
/*
 * RW. Contains the direction control (RTS or DTR) delay value. This delay time
 * is in periods of the baud clock.
 */
#define ASM9260_BM_RS485DLY_MASK                (0xff << 0)

#define ASM9260_HW_AUTOBAUD                     0x00c0
/* WO. Auto-baud time-out interrupt clear bit. */
#define ASM9260_BM_AUTOBAUD_TO_INT_CLR          BIT(9)
/* WO. End of auto-baud interrupt clear bit. */
#define ASM9260_BM_AUTOBAUD_EO_INT_CLR          BIT(8)
/* Restart in case of timeout (counter restarts at next UART Rx falling edge) */
#define ASM9260_BM_AUTOBAUD_AUTORESTART         BIT(2)
/* Auto-baud mode select bit. 0 - Mode 0, 1 - Mode 1. */
#define ASM9260_BM_AUTOBAUD_MODE                BIT(1)
/*
 * Auto-baud start (auto-baud is running). Auto-baud run bit. This bit is
 * automatically cleared after auto-baud completion.
 */
#define ASM9260_BM_AUTOBAUD_START               BIT(0)

#define ASM9260_HW_CTRL3                        0x00d0
#define ASM9260_BM_CTRL3_OUTCLK_DIV_MASK        (0xffff << 16)
/*
 * RW. Provide clk over OUTCLK pin. In case of asm9260 it can be configured on
 * pins 137 and 144.
 */
#define ASM9260_BM_CTRL3_MASTERMODE             BIT(6)
/* RW. Baud Rate Mode: 1 - Enable sync mode. 0 - async mode. */
#define ASM9260_BM_CTRL3_SYNCMODE               BIT(4)
/* RW. 1 - MSB bit send frist; 0 - LSB bit frist. */
#define ASM9260_BM_CTRL3_MSBF                   BIT(2)
/* RW. 1 - sample rate = 8 x Baudrate; 0 - sample rate = 16 x Baudrate. */
#define ASM9260_BM_CTRL3_BAUD8                  BIT(1)
/* RW. 1 - Set word length to 9bit. 0 - use ASM9260_BM_LCTRL_WLEN */
#define ASM9260_BM_CTRL3_9BIT                   BIT(0)

#define ASM9260_HW_ISO7816_CTRL                 0x00e0
/* RW. Enable High Speed mode. */
#define ASM9260_BM_ISO7816CTRL_HS               BIT(12)
/* Disable Successive Receive NACK */
#define ASM9260_BM_ISO7816CTRL_DS_NACK          BIT(8)
#define ASM9260_BM_ISO7816CTRL_MAX_ITER_MASK    (0xff << 4)
/* Receive NACK Inhibit */
#define ASM9260_BM_ISO7816CTRL_INACK            BIT(3)
#define ASM9260_BM_ISO7816CTRL_NEG_DATA         BIT(2)
/* RW. 1 - ISO7816 mode; 0 - USART mode */
#define ASM9260_BM_ISO7816CTRL_ENABLE           BIT(0)

#define ASM9260_HW_ISO7816_ERRCNT               0x00f0
/* Parity error counter. Will be cleared after reading */
#define ASM9260_BM_ISO7816_NB_ERRORS_MASK       (0xff << 0)

#define ASM9260_HW_ISO7816_STATUS               0x0100
/* Max number of Repetitions Reached */
#define ASM9260_BM_ISO7816_STAT_ITERATION       BIT(0)

/* End of Alphascale asm9260 defines */

static struct uart_driver auart_driver;

enum mxs_auart_type {
        IMX23_AUART,
        IMX28_AUART,
        ASM9260_AUART,
};

struct vendor_data {
        const u16       *reg_offset;
};

enum {
        REG_CTRL0,
        REG_CTRL1,
        REG_CTRL2,
        REG_LINECTRL,
        REG_LINECTRL2,
        REG_INTR,
        REG_DATA,
        REG_STAT,
        REG_DEBUG,
        REG_VERSION,
        REG_AUTOBAUD,

        /* The size of the array - must be last */
        REG_ARRAY_SIZE,
};

static const u16 mxs_asm9260_offsets[REG_ARRAY_SIZE] = {
        [REG_CTRL0] = ASM9260_HW_CTRL0,
        [REG_CTRL1] = ASM9260_HW_CTRL1,
        [REG_CTRL2] = ASM9260_HW_CTRL2,
        [REG_LINECTRL] = ASM9260_HW_LINECTRL,
        [REG_INTR] = ASM9260_HW_INTR,
        [REG_DATA] = ASM9260_HW_DATA,
        [REG_STAT] = ASM9260_HW_STAT,
        [REG_DEBUG] = ASM9260_HW_DEBUG,
        [REG_AUTOBAUD] = ASM9260_HW_AUTOBAUD,
};

static const u16 mxs_stmp37xx_offsets[REG_ARRAY_SIZE] = {
        [REG_CTRL0] = AUART_CTRL0,
        [REG_CTRL1] = AUART_CTRL1,
        [REG_CTRL2] = AUART_CTRL2,
        [REG_LINECTRL] = AUART_LINECTRL,
        [REG_LINECTRL2] = AUART_LINECTRL2,
        [REG_INTR] = AUART_INTR,
        [REG_DATA] = AUART_DATA,
        [REG_STAT] = AUART_STAT,
        [REG_DEBUG] = AUART_DEBUG,
        [REG_VERSION] = AUART_VERSION,
        [REG_AUTOBAUD] = AUART_AUTOBAUD,
};

static const struct vendor_data vendor_alphascale_asm9260 = {
        .reg_offset = mxs_asm9260_offsets,
};

static const struct vendor_data vendor_freescale_stmp37xx = {
        .reg_offset = mxs_stmp37xx_offsets,
};

struct mxs_auart_port {
        struct uart_port port;

#define MXS_AUART_DMA_ENABLED   0x2
#define MXS_AUART_DMA_TX_SYNC   2  /* bit 2 */
#define MXS_AUART_DMA_RX_READY  3  /* bit 3 */
#define MXS_AUART_RTSCTS        4  /* bit 4 */
        unsigned long flags;
        unsigned int mctrl_prev;
        enum mxs_auart_type devtype;
        const struct vendor_data *vendor;

        struct clk *clk;
        struct clk *clk_ahb;
        struct device *dev;

        /* for DMA */
        struct scatterlist tx_sgl;
        struct dma_chan *tx_dma_chan;
        void *tx_dma_buf;

        struct scatterlist rx_sgl;
        struct dma_chan *rx_dma_chan;
        void *rx_dma_buf;

        struct mctrl_gpios      *gpios;
        int                     gpio_irq[UART_GPIO_MAX];
        bool                    ms_irq_enabled;
};

static const struct platform_device_id mxs_auart_devtype[] = {
        { .name = "mxs-auart-imx23", .driver_data = IMX23_AUART },
        { .name = "mxs-auart-imx28", .driver_data = IMX28_AUART },
        { .name = "as-auart-asm9260", .driver_data = ASM9260_AUART },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(platform, mxs_auart_devtype);

static const struct of_device_id mxs_auart_dt_ids[] = {
        {
                .compatible = "fsl,imx28-auart",
                .data = &mxs_auart_devtype[IMX28_AUART]
        }, {
                .compatible = "fsl,imx23-auart",
                .data = &mxs_auart_devtype[IMX23_AUART]
        }, {
                .compatible = "alphascale,asm9260-auart",
                .data = &mxs_auart_devtype[ASM9260_AUART]
        }, { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, mxs_auart_dt_ids);

static inline int is_imx28_auart(struct mxs_auart_port *s)
{
        return s->devtype == IMX28_AUART;
}

static inline int is_asm9260_auart(struct mxs_auart_port *s)
{
        return s->devtype == ASM9260_AUART;
}

static inline bool auart_dma_enabled(struct mxs_auart_port *s)
{
        return s->flags & MXS_AUART_DMA_ENABLED;
}

static unsigned int mxs_reg_to_offset(const struct mxs_auart_port *uap,
                                      unsigned int reg)
{
        return uap->vendor->reg_offset[reg];
}

static unsigned int mxs_read(const struct mxs_auart_port *uap,
                             unsigned int reg)
{
        void __iomem *addr = uap->port.membase + mxs_reg_to_offset(uap, reg);

        return readl_relaxed(addr);
}

static void mxs_write(unsigned int val, struct mxs_auart_port *uap,
                      unsigned int reg)
{
        void __iomem *addr = uap->port.membase + mxs_reg_to_offset(uap, reg);

        writel_relaxed(val, addr);
}

static void mxs_set(unsigned int val, struct mxs_auart_port *uap,
                    unsigned int reg)
{
        void __iomem *addr = uap->port.membase + mxs_reg_to_offset(uap, reg);

        writel_relaxed(val, addr + SET_REG);
}

static void mxs_clr(unsigned int val, struct mxs_auart_port *uap,
                    unsigned int reg)
{
        void __iomem *addr = uap->port.membase + mxs_reg_to_offset(uap, reg);

        writel_relaxed(val, addr + CLR_REG);
}

static void mxs_auart_stop_tx(struct uart_port *u);

#define to_auart_port(u) container_of(u, struct mxs_auart_port, port)

static void mxs_auart_tx_chars(struct mxs_auart_port *s);

static void dma_tx_callback(void *param)
{
        struct mxs_auart_port *s = param;
        struct circ_buf *xmit = &s->port.state->xmit;

        dma_unmap_sg(s->dev, &s->tx_sgl, 1, DMA_TO_DEVICE);

        /* clear the bit used to serialize the DMA tx. */
        clear_bit(MXS_AUART_DMA_TX_SYNC, &s->flags);
        smp_mb__after_atomic();

        /* wake up the possible processes. */
        if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
                uart_write_wakeup(&s->port);

        mxs_auart_tx_chars(s);
}

static int mxs_auart_dma_tx(struct mxs_auart_port *s, int size)
{
        struct dma_async_tx_descriptor *desc;
        struct scatterlist *sgl = &s->tx_sgl;
        struct dma_chan *channel = s->tx_dma_chan;
        u32 pio;

        /* [1] : send PIO. Note, the first pio word is CTRL1. */
        pio = AUART_CTRL1_XFER_COUNT(size);
        desc = dmaengine_prep_slave_sg(channel, (struct scatterlist *)&pio,
                                        1, DMA_TRANS_NONE, 0);
        if (!desc) {
                dev_err(s->dev, "step 1 error\n");
                return -EINVAL;
        }

        /* [2] : set DMA buffer. */
        sg_init_one(sgl, s->tx_dma_buf, size);
        dma_map_sg(s->dev, sgl, 1, DMA_TO_DEVICE);
        desc = dmaengine_prep_slave_sg(channel, sgl,
                        1, DMA_MEM_TO_DEV, DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
        if (!desc) {
                dev_err(s->dev, "step 2 error\n");
                return -EINVAL;
        }

        /* [3] : submit the DMA */
        desc->callback = dma_tx_callback;
        desc->callback_param = s;
        dmaengine_submit(desc);
        dma_async_issue_pending(channel);
        return 0;
}

static void mxs_auart_tx_chars(struct mxs_auart_port *s)
{
        struct circ_buf *xmit = &s->port.state->xmit;

        if (auart_dma_enabled(s)) {
                u32 i = 0;
                int size;
                void *buffer = s->tx_dma_buf;

                if (test_and_set_bit(MXS_AUART_DMA_TX_SYNC, &s->flags))
                        return;

                while (!uart_circ_empty(xmit) && !uart_tx_stopped(&s->port)) {
                        size = min_t(u32, UART_XMIT_SIZE - i,
                                     CIRC_CNT_TO_END(xmit->head,
                                                     xmit->tail,
                                                     UART_XMIT_SIZE));
                        memcpy(buffer + i, xmit->buf + xmit->tail, size);
                        xmit->tail = (xmit->tail + size) & (UART_XMIT_SIZE - 1);

                        i += size;
                        if (i >= UART_XMIT_SIZE)
                                break;
                }

                if (uart_tx_stopped(&s->port))
                        mxs_auart_stop_tx(&s->port);

                if (i) {
                        mxs_auart_dma_tx(s, i);
                } else {
                        clear_bit(MXS_AUART_DMA_TX_SYNC, &s->flags);
                        smp_mb__after_atomic();
                }
                return;
        }


        while (!(mxs_read(s, REG_STAT) & AUART_STAT_TXFF)) {
                if (s->port.x_char) {
                        s->port.icount.tx++;
                        mxs_write(s->port.x_char, s, REG_DATA);
                        s->port.x_char = 0;
                        continue;
                }
                if (!uart_circ_empty(xmit) && !uart_tx_stopped(&s->port)) {
                        s->port.icount.tx++;
                        mxs_write(xmit->buf[xmit->tail], s, REG_DATA);
                        xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
                } else
                        break;
        }
        if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
                uart_write_wakeup(&s->port);

        if (uart_circ_empty(&(s->port.state->xmit)))
                mxs_clr(AUART_INTR_TXIEN, s, REG_INTR);
        else
                mxs_set(AUART_INTR_TXIEN, s, REG_INTR);

        if (uart_tx_stopped(&s->port))
                mxs_auart_stop_tx(&s->port);
}

static void mxs_auart_rx_char(struct mxs_auart_port *s)
{
        int flag;
        u32 stat;
        u8 c;

        c = mxs_read(s, REG_DATA);
        stat = mxs_read(s, REG_STAT);

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

        if (stat & AUART_STAT_BERR) {
                s->port.icount.brk++;
                if (uart_handle_break(&s->port))
                        goto out;
        } else if (stat & AUART_STAT_PERR) {
                s->port.icount.parity++;
        } else if (stat & AUART_STAT_FERR) {
                s->port.icount.frame++;
        }

        /*
         * Mask off conditions which should be ingored.
         */
        stat &= s->port.read_status_mask;

        if (stat & AUART_STAT_BERR) {
                flag = TTY_BREAK;
        } else if (stat & AUART_STAT_PERR)
                flag = TTY_PARITY;
        else if (stat & AUART_STAT_FERR)
                flag = TTY_FRAME;

        if (stat & AUART_STAT_OERR)
                s->port.icount.overrun++;

        if (uart_handle_sysrq_char(&s->port, c))
                goto out;

        uart_insert_char(&s->port, stat, AUART_STAT_OERR, c, flag);
out:
        mxs_write(stat, s, REG_STAT);
}

static void mxs_auart_rx_chars(struct mxs_auart_port *s)
{
        u32 stat = 0;

        for (;;) {
                stat = mxs_read(s, REG_STAT);
                if (stat & AUART_STAT_RXFE)
                        break;
                mxs_auart_rx_char(s);
        }

        mxs_write(stat, s, REG_STAT);
        tty_flip_buffer_push(&s->port.state->port);
}

static int mxs_auart_request_port(struct uart_port *u)
{
        return 0;
}

static int mxs_auart_verify_port(struct uart_port *u,
                                    struct serial_struct *ser)
{
        if (u->type != PORT_UNKNOWN && u->type != PORT_IMX)
                return -EINVAL;
        return 0;
}

static void mxs_auart_config_port(struct uart_port *u, int flags)
{
}

static const char *mxs_auart_type(struct uart_port *u)
{
        struct mxs_auart_port *s = to_auart_port(u);

        return dev_name(s->dev);
}

static void mxs_auart_release_port(struct uart_port *u)
{
}

static void mxs_auart_set_mctrl(struct uart_port *u, unsigned mctrl)
{
        struct mxs_auart_port *s = to_auart_port(u);

        u32 ctrl = mxs_read(s, REG_CTRL2);

        ctrl &= ~(AUART_CTRL2_RTSEN | AUART_CTRL2_RTS);
        if (mctrl & TIOCM_RTS) {
                if (uart_cts_enabled(u))
                        ctrl |= AUART_CTRL2_RTSEN;
                else
                        ctrl |= AUART_CTRL2_RTS;
        }

        mxs_write(ctrl, s, REG_CTRL2);

        mctrl_gpio_set(s->gpios, mctrl);
}

#define MCTRL_ANY_DELTA        (TIOCM_RI | TIOCM_DSR | TIOCM_CD | TIOCM_CTS)
static u32 mxs_auart_modem_status(struct mxs_auart_port *s, u32 mctrl)
{
        u32 mctrl_diff;

        mctrl_diff = mctrl ^ s->mctrl_prev;
        s->mctrl_prev = mctrl;
        if (mctrl_diff & MCTRL_ANY_DELTA && s->ms_irq_enabled &&
                                                s->port.state != NULL) {
                if (mctrl_diff & TIOCM_RI)
                        s->port.icount.rng++;
                if (mctrl_diff & TIOCM_DSR)
                        s->port.icount.dsr++;
                if (mctrl_diff & TIOCM_CD)
                        uart_handle_dcd_change(&s->port, mctrl & TIOCM_CD);
                if (mctrl_diff & TIOCM_CTS)
                        uart_handle_cts_change(&s->port, mctrl & TIOCM_CTS);

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

static u32 mxs_auart_get_mctrl(struct uart_port *u)
{
        struct mxs_auart_port *s = to_auart_port(u);
        u32 stat = mxs_read(s, REG_STAT);
        u32 mctrl = 0;

        if (stat & AUART_STAT_CTS)
                mctrl |= TIOCM_CTS;

        return mctrl_gpio_get(s->gpios, &mctrl);
}

/*
 * Enable modem status interrupts
 */
static void mxs_auart_enable_ms(struct uart_port *port)
{
        struct mxs_auart_port *s = to_auart_port(port);

        /*
         * Interrupt should not be enabled twice
         */
        if (s->ms_irq_enabled)
                return;

        s->ms_irq_enabled = true;

        if (s->gpio_irq[UART_GPIO_CTS] >= 0)
                enable_irq(s->gpio_irq[UART_GPIO_CTS]);
        /* TODO: enable AUART_INTR_CTSMIEN otherwise */

        if (s->gpio_irq[UART_GPIO_DSR] >= 0)
                enable_irq(s->gpio_irq[UART_GPIO_DSR]);

        if (s->gpio_irq[UART_GPIO_RI] >= 0)
                enable_irq(s->gpio_irq[UART_GPIO_RI]);

        if (s->gpio_irq[UART_GPIO_DCD] >= 0)
                enable_irq(s->gpio_irq[UART_GPIO_DCD]);
}

/*
 * Disable modem status interrupts
 */
static void mxs_auart_disable_ms(struct uart_port *port)
{
        struct mxs_auart_port *s = to_auart_port(port);

        /*
         * Interrupt should not be disabled twice
         */
        if (!s->ms_irq_enabled)
                return;

        s->ms_irq_enabled = false;

        if (s->gpio_irq[UART_GPIO_CTS] >= 0)
                disable_irq(s->gpio_irq[UART_GPIO_CTS]);
        /* TODO: disable AUART_INTR_CTSMIEN otherwise */

        if (s->gpio_irq[UART_GPIO_DSR] >= 0)
                disable_irq(s->gpio_irq[UART_GPIO_DSR]);

        if (s->gpio_irq[UART_GPIO_RI] >= 0)
                disable_irq(s->gpio_irq[UART_GPIO_RI]);

        if (s->gpio_irq[UART_GPIO_DCD] >= 0)
                disable_irq(s->gpio_irq[UART_GPIO_DCD]);
}

static int mxs_auart_dma_prep_rx(struct mxs_auart_port *s);
static void dma_rx_callback(void *arg)
{
        struct mxs_auart_port *s = (struct mxs_auart_port *) arg;
        struct tty_port *port = &s->port.state->port;
        int count;
        u32 stat;

        dma_unmap_sg(s->dev, &s->rx_sgl, 1, DMA_FROM_DEVICE);

        stat = mxs_read(s, REG_STAT);
        stat &= ~(AUART_STAT_OERR | AUART_STAT_BERR |
                        AUART_STAT_PERR | AUART_STAT_FERR);

        count = stat & AUART_STAT_RXCOUNT_MASK;
        tty_insert_flip_string(port, s->rx_dma_buf, count);

        mxs_write(stat, s, REG_STAT);
        tty_flip_buffer_push(port);

        /* start the next DMA for RX. */
        mxs_auart_dma_prep_rx(s);
}

static int mxs_auart_dma_prep_rx(struct mxs_auart_port *s)
{
        struct dma_async_tx_descriptor *desc;
        struct scatterlist *sgl = &s->rx_sgl;
        struct dma_chan *channel = s->rx_dma_chan;
        u32 pio[1];

        /* [1] : send PIO */
        pio[0] = AUART_CTRL0_RXTO_ENABLE
                | AUART_CTRL0_RXTIMEOUT(0x80)
                | AUART_CTRL0_XFER_COUNT(UART_XMIT_SIZE);
        desc = dmaengine_prep_slave_sg(channel, (struct scatterlist *)pio,
                                        1, DMA_TRANS_NONE, 0);
        if (!desc) {
                dev_err(s->dev, "step 1 error\n");
                return -EINVAL;
        }

        /* [2] : send DMA request */
        sg_init_one(sgl, s->rx_dma_buf, UART_XMIT_SIZE);
        dma_map_sg(s->dev, sgl, 1, DMA_FROM_DEVICE);
        desc = dmaengine_prep_slave_sg(channel, sgl, 1, DMA_DEV_TO_MEM,
                                        DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
        if (!desc) {
                dev_err(s->dev, "step 2 error\n");
                return -1;
        }

        /* [3] : submit the DMA, but do not issue it. */
        desc->callback = dma_rx_callback;
        desc->callback_param = s;
        dmaengine_submit(desc);
        dma_async_issue_pending(channel);
        return 0;
}

static void mxs_auart_dma_exit_channel(struct mxs_auart_port *s)
{
        if (s->tx_dma_chan) {
                dma_release_channel(s->tx_dma_chan);
                s->tx_dma_chan = NULL;
        }
        if (s->rx_dma_chan) {
                dma_release_channel(s->rx_dma_chan);
                s->rx_dma_chan = NULL;
        }

        kfree(s->tx_dma_buf);
        kfree(s->rx_dma_buf);
        s->tx_dma_buf = NULL;
        s->rx_dma_buf = NULL;
}

static void mxs_auart_dma_exit(struct mxs_auart_port *s)
{

        mxs_clr(AUART_CTRL2_TXDMAE | AUART_CTRL2_RXDMAE | AUART_CTRL2_DMAONERR,
                s, REG_CTRL2);

        mxs_auart_dma_exit_channel(s);
        s->flags &= ~MXS_AUART_DMA_ENABLED;
        clear_bit(MXS_AUART_DMA_TX_SYNC, &s->flags);
        clear_bit(MXS_AUART_DMA_RX_READY, &s->flags);
}

static int mxs_auart_dma_init(struct mxs_auart_port *s)
{
        if (auart_dma_enabled(s))
                return 0;

        /* init for RX */
        s->rx_dma_chan = dma_request_slave_channel(s->dev, "rx");
        if (!s->rx_dma_chan)
                goto err_out;
        s->rx_dma_buf = kzalloc(UART_XMIT_SIZE, GFP_KERNEL | GFP_DMA);
        if (!s->rx_dma_buf)
                goto err_out;

        /* init for TX */
        s->tx_dma_chan = dma_request_slave_channel(s->dev, "tx");
        if (!s->tx_dma_chan)
                goto err_out;
        s->tx_dma_buf = kzalloc(UART_XMIT_SIZE, GFP_KERNEL | GFP_DMA);
        if (!s->tx_dma_buf)
                goto err_out;

        /* set the flags */
        s->flags |= MXS_AUART_DMA_ENABLED;
        dev_dbg(s->dev, "enabled the DMA support.");

        /* The DMA buffer is now the FIFO the TTY subsystem can use */
        s->port.fifosize = UART_XMIT_SIZE;

        return 0;

err_out:
        mxs_auart_dma_exit_channel(s);
        return -EINVAL;

}

#define RTS_AT_AUART()  !mctrl_gpio_to_gpiod(s->gpios, UART_GPIO_RTS)
#define CTS_AT_AUART()  !mctrl_gpio_to_gpiod(s->gpios, UART_GPIO_CTS)
static void mxs_auart_settermios(struct uart_port *u,
                                 struct ktermios *termios,
                                 struct ktermios *old)
{
        struct mxs_auart_port *s = to_auart_port(u);
        u32 bm, ctrl, ctrl2, div;
        unsigned int cflag, baud, baud_min, baud_max;

        cflag = termios->c_cflag;

        ctrl = AUART_LINECTRL_FEN;
        ctrl2 = mxs_read(s, REG_CTRL2);

        /* byte size */
        switch (cflag & CSIZE) {
        case CS5:
                bm = 0;
                break;
        case CS6:
                bm = 1;
                break;
        case CS7:
                bm = 2;
                break;
        case CS8:
                bm = 3;
                break;
        default:
                return;
        }

        ctrl |= AUART_LINECTRL_WLEN(bm);

        /* parity */
        if (cflag & PARENB) {
                ctrl |= AUART_LINECTRL_PEN;
                if ((cflag & PARODD) == 0)
                        ctrl |= AUART_LINECTRL_EPS;
                if (cflag & CMSPAR)
                        ctrl |= AUART_LINECTRL_SPS;
        }

        u->read_status_mask = AUART_STAT_OERR;

        if (termios->c_iflag & INPCK)
                u->read_status_mask |= AUART_STAT_PERR;
        if (termios->c_iflag & (IGNBRK | BRKINT | PARMRK))
                u->read_status_mask |= AUART_STAT_BERR;

        /*
         * Characters to ignore
         */
        u->ignore_status_mask = 0;
        if (termios->c_iflag & IGNPAR)
                u->ignore_status_mask |= AUART_STAT_PERR;
        if (termios->c_iflag & IGNBRK) {
                u->ignore_status_mask |= AUART_STAT_BERR;
                /*
                 * If we're ignoring parity and break indicators,
                 * ignore overruns too (for real raw support).
                 */
                if (termios->c_iflag & IGNPAR)
                        u->ignore_status_mask |= AUART_STAT_OERR;
        }

        /*
         * ignore all characters if CREAD is not set
         */
        if (cflag & CREAD)
                ctrl2 |= AUART_CTRL2_RXE;
        else
                ctrl2 &= ~AUART_CTRL2_RXE;

        /* figure out the stop bits requested */
        if (cflag & CSTOPB)
                ctrl |= AUART_LINECTRL_STP2;

        /* figure out the hardware flow control settings */
        ctrl2 &= ~(AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN);
        if (cflag & CRTSCTS) {
                /*
                 * The DMA has a bug(see errata:2836) in mx23.
                 * So we can not implement the DMA for auart in mx23,
                 * we can only implement the DMA support for auart
                 * in mx28.
                 */
                if (is_imx28_auart(s)
                                && test_bit(MXS_AUART_RTSCTS, &s->flags)) {
                        if (!mxs_auart_dma_init(s))
                                /* enable DMA tranfer */
                                ctrl2 |= AUART_CTRL2_TXDMAE | AUART_CTRL2_RXDMAE
                                       | AUART_CTRL2_DMAONERR;
                }
                /* Even if RTS is GPIO line RTSEN can be enabled because
                 * the pinctrl configuration decides about RTS pin function */
                ctrl2 |= AUART_CTRL2_RTSEN;
                if (CTS_AT_AUART())
                        ctrl2 |= AUART_CTRL2_CTSEN;
        }

        /* set baud rate */
        if (is_asm9260_auart(s)) {
                baud = uart_get_baud_rate(u, termios, old,
                                          u->uartclk * 4 / 0x3FFFFF,
                                          u->uartclk / 16);
                div = u->uartclk * 4 / baud;
        } else {
                baud_min = DIV_ROUND_UP(u->uartclk * 32,
                                        AUART_LINECTRL_BAUD_DIV_MAX);
                baud_max = u->uartclk * 32 / AUART_LINECTRL_BAUD_DIV_MIN;
                baud = uart_get_baud_rate(u, termios, old, baud_min, baud_max);
                div = DIV_ROUND_CLOSEST(u->uartclk * 32, baud);
        }

        ctrl |= AUART_LINECTRL_BAUD_DIVFRAC(div & 0x3F);
        ctrl |= AUART_LINECTRL_BAUD_DIVINT(div >> 6);
        mxs_write(ctrl, s, REG_LINECTRL);

        mxs_write(ctrl2, s, REG_CTRL2);

        uart_update_timeout(u, termios->c_cflag, baud);

        /* prepare for the DMA RX. */
        if (auart_dma_enabled(s) &&
                !test_and_set_bit(MXS_AUART_DMA_RX_READY, &s->flags)) {
                if (!mxs_auart_dma_prep_rx(s)) {
                        /* Disable the normal RX interrupt. */
                        mxs_clr(AUART_INTR_RXIEN | AUART_INTR_RTIEN,
                                s, REG_INTR);
                } else {
                        mxs_auart_dma_exit(s);
                        dev_err(s->dev, "We can not start up the DMA.\n");
                }
        }

        /* CTS flow-control and modem-status interrupts */
        if (UART_ENABLE_MS(u, termios->c_cflag))
                mxs_auart_enable_ms(u);
        else
                mxs_auart_disable_ms(u);
}

static void mxs_auart_set_ldisc(struct uart_port *port,
                                struct ktermios *termios)
{
        if (termios->c_line == N_PPS) {
                port->flags |= UPF_HARDPPS_CD;
                mxs_auart_enable_ms(port);
        } else {
                port->flags &= ~UPF_HARDPPS_CD;
        }
}

static irqreturn_t mxs_auart_irq_handle(int irq, void *context)
{
        u32 istat;
        struct mxs_auart_port *s = context;
        u32 mctrl_temp = s->mctrl_prev;
        u32 stat = mxs_read(s, REG_STAT);

        istat = mxs_read(s, REG_INTR);

        /* ack irq */
        mxs_clr(istat & (AUART_INTR_RTIS | AUART_INTR_TXIS | AUART_INTR_RXIS
                | AUART_INTR_CTSMIS), s, REG_INTR);

        /*
         * Dealing with GPIO interrupt
         */
        if (irq == s->gpio_irq[UART_GPIO_CTS] ||
            irq == s->gpio_irq[UART_GPIO_DCD] ||
            irq == s->gpio_irq[UART_GPIO_DSR] ||
            irq == s->gpio_irq[UART_GPIO_RI])
                mxs_auart_modem_status(s,
                                mctrl_gpio_get(s->gpios, &mctrl_temp));

        if (istat & AUART_INTR_CTSMIS) {
                if (CTS_AT_AUART() && s->ms_irq_enabled)
                        uart_handle_cts_change(&s->port,
                                        stat & AUART_STAT_CTS);
                mxs_clr(AUART_INTR_CTSMIS, s, REG_INTR);
                istat &= ~AUART_INTR_CTSMIS;
        }

        if (istat & (AUART_INTR_RTIS | AUART_INTR_RXIS)) {
                if (!auart_dma_enabled(s))
                        mxs_auart_rx_chars(s);
                istat &= ~(AUART_INTR_RTIS | AUART_INTR_RXIS);
        }

        if (istat & AUART_INTR_TXIS) {
                mxs_auart_tx_chars(s);
                istat &= ~AUART_INTR_TXIS;
        }

        return IRQ_HANDLED;
}

static void mxs_auart_reset_deassert(struct mxs_auart_port *s)
{
        int i;
        unsigned int reg;

        mxs_clr(AUART_CTRL0_SFTRST, s, REG_CTRL0);

        for (i = 0; i < 10000; i++) {
                reg = mxs_read(s, REG_CTRL0);
                if (!(reg & AUART_CTRL0_SFTRST))
                        break;
                udelay(3);
        }
        mxs_clr(AUART_CTRL0_CLKGATE, s, REG_CTRL0);
}

static void mxs_auart_reset_assert(struct mxs_auart_port *s)
{
        int i;
        u32 reg;

        reg = mxs_read(s, REG_CTRL0);
        /* if already in reset state, keep it untouched */
        if (reg & AUART_CTRL0_SFTRST)
                return;

        mxs_clr(AUART_CTRL0_CLKGATE, s, REG_CTRL0);
        mxs_set(AUART_CTRL0_SFTRST, s, REG_CTRL0);

        for (i = 0; i < 1000; i++) {
                reg = mxs_read(s, REG_CTRL0);
                /* reset is finished when the clock is gated */
                if (reg & AUART_CTRL0_CLKGATE)
                        return;
                udelay(10);
        }

        dev_err(s->dev, "Failed to reset the unit.");
}

static int mxs_auart_startup(struct uart_port *u)
{
        int ret;
        struct mxs_auart_port *s = to_auart_port(u);

        ret = clk_prepare_enable(s->clk);
        if (ret)
                return ret;

        if (uart_console(u)) {
                mxs_clr(AUART_CTRL0_CLKGATE, s, REG_CTRL0);
        } else {
                /* reset the unit to a well known state */
                mxs_auart_reset_assert(s);
                mxs_auart_reset_deassert(s);
        }

        mxs_set(AUART_CTRL2_UARTEN, s, REG_CTRL2);

        mxs_write(AUART_INTR_RXIEN | AUART_INTR_RTIEN | AUART_INTR_CTSMIEN,
                  s, REG_INTR);

        /* Reset FIFO size (it could have changed if DMA was enabled) */
        u->fifosize = MXS_AUART_FIFO_SIZE;

        /*
         * Enable fifo so all four bytes of a DMA word are written to
         * output (otherwise, only the LSB is written, ie. 1 in 4 bytes)
         */
        mxs_set(AUART_LINECTRL_FEN, s, REG_LINECTRL);

        /* get initial status of modem lines */
        mctrl_gpio_get(s->gpios, &s->mctrl_prev);

        s->ms_irq_enabled = false;
        return 0;
}

static void mxs_auart_shutdown(struct uart_port *u)
{
        struct mxs_auart_port *s = to_auart_port(u);

        mxs_auart_disable_ms(u);

        if (auart_dma_enabled(s))
                mxs_auart_dma_exit(s);

        if (uart_console(u)) {
                mxs_clr(AUART_CTRL2_UARTEN, s, REG_CTRL2);

                mxs_clr(AUART_INTR_RXIEN | AUART_INTR_RTIEN |
                        AUART_INTR_CTSMIEN, s, REG_INTR);
                mxs_set(AUART_CTRL0_CLKGATE, s, REG_CTRL0);
        } else {
                mxs_auart_reset_assert(s);
        }

        clk_disable_unprepare(s->clk);
}

static unsigned int mxs_auart_tx_empty(struct uart_port *u)
{
        struct mxs_auart_port *s = to_auart_port(u);

        if ((mxs_read(s, REG_STAT) &
                 (AUART_STAT_TXFE | AUART_STAT_BUSY)) == AUART_STAT_TXFE)
                return TIOCSER_TEMT;

        return 0;
}

static void mxs_auart_start_tx(struct uart_port *u)
{
        struct mxs_auart_port *s = to_auart_port(u);

        /* enable transmitter */
        mxs_set(AUART_CTRL2_TXE, s, REG_CTRL2);

        mxs_auart_tx_chars(s);
}

static void mxs_auart_stop_tx(struct uart_port *u)
{
        struct mxs_auart_port *s = to_auart_port(u);

        mxs_clr(AUART_CTRL2_TXE, s, REG_CTRL2);
}

static void mxs_auart_stop_rx(struct uart_port *u)
{
        struct mxs_auart_port *s = to_auart_port(u);

        mxs_clr(AUART_CTRL2_RXE, s, REG_CTRL2);
}

static void mxs_auart_break_ctl(struct uart_port *u, int ctl)
{
        struct mxs_auart_port *s = to_auart_port(u);

        if (ctl)
                mxs_set(AUART_LINECTRL_BRK, s, REG_LINECTRL);
        else
                mxs_clr(AUART_LINECTRL_BRK, s, REG_LINECTRL);
}

static const struct uart_ops mxs_auart_ops = {
        .tx_empty       = mxs_auart_tx_empty,
        .start_tx       = mxs_auart_start_tx,
        .stop_tx        = mxs_auart_stop_tx,
        .stop_rx        = mxs_auart_stop_rx,
        .enable_ms      = mxs_auart_enable_ms,
        .break_ctl      = mxs_auart_break_ctl,
        .set_mctrl      = mxs_auart_set_mctrl,
        .get_mctrl      = mxs_auart_get_mctrl,
        .startup        = mxs_auart_startup,
        .shutdown       = mxs_auart_shutdown,
        .set_termios    = mxs_auart_settermios,
        .set_ldisc      = mxs_auart_set_ldisc,
        .type           = mxs_auart_type,
        .release_port   = mxs_auart_release_port,
        .request_port   = mxs_auart_request_port,
        .config_port    = mxs_auart_config_port,
        .verify_port    = mxs_auart_verify_port,
};

static struct mxs_auart_port *auart_port[MXS_AUART_PORTS];

#ifdef CONFIG_SERIAL_MXS_AUART_CONSOLE
static void mxs_auart_console_putchar(struct uart_port *port, int ch)
{
        struct mxs_auart_port *s = to_auart_port(port);
        unsigned int to = 1000;

        while (mxs_read(s, REG_STAT) & AUART_STAT_TXFF) {
                if (!to--)
                        break;
                udelay(1);
        }

        mxs_write(ch, s, REG_DATA);
}

static void
auart_console_write(struct console *co, const char *str, unsigned int count)
{
        struct mxs_auart_port *s;
        struct uart_port *port;
        unsigned int old_ctrl0, old_ctrl2;
        unsigned int to = 20000;

        if (co->index >= MXS_AUART_PORTS || co->index < 0)
                return;

        s = auart_port[co->index];
        port = &s->port;

        clk_enable(s->clk);

        /* First save the CR then disable the interrupts */
        old_ctrl2 = mxs_read(s, REG_CTRL2);
        old_ctrl0 = mxs_read(s, REG_CTRL0);

        mxs_clr(AUART_CTRL0_CLKGATE, s, REG_CTRL0);
        mxs_set(AUART_CTRL2_UARTEN | AUART_CTRL2_TXE, s, REG_CTRL2);

        uart_console_write(port, str, count, mxs_auart_console_putchar);

        /* Finally, wait for transmitter to become empty ... */
        while (mxs_read(s, REG_STAT) & AUART_STAT_BUSY) {
                udelay(1);
                if (!to--)
                        break;
        }

        /*
         * ... and restore the TCR if we waited long enough for the transmitter
         * to be idle. This might keep the transmitter enabled although it is
         * unused, but that is better than to disable it while it is still
         * transmitting.
         */
        if (!(mxs_read(s, REG_STAT) & AUART_STAT_BUSY)) {
                mxs_write(old_ctrl0, s, REG_CTRL0);
                mxs_write(old_ctrl2, s, REG_CTRL2);
        }

        clk_disable(s->clk);
}

static void __init
auart_console_get_options(struct mxs_auart_port *s, int *baud,
                          int *parity, int *bits)
{
        struct uart_port *port = &s->port;
        unsigned int lcr_h, quot;

        if (!(mxs_read(s, REG_CTRL2) & AUART_CTRL2_UARTEN))
                return;

        lcr_h = mxs_read(s, REG_LINECTRL);

        *parity = 'n';
        if (lcr_h & AUART_LINECTRL_PEN) {
                if (lcr_h & AUART_LINECTRL_EPS)
                        *parity = 'e';
                else
                        *parity = 'o';
        }

        if ((lcr_h & AUART_LINECTRL_WLEN_MASK) == AUART_LINECTRL_WLEN(2))
                *bits = 7;
        else
                *bits = 8;

        quot = ((mxs_read(s, REG_LINECTRL) & AUART_LINECTRL_BAUD_DIVINT_MASK))
                >> (AUART_LINECTRL_BAUD_DIVINT_SHIFT - 6);
        quot |= ((mxs_read(s, REG_LINECTRL) & AUART_LINECTRL_BAUD_DIVFRAC_MASK))
                >> AUART_LINECTRL_BAUD_DIVFRAC_SHIFT;
        if (quot == 0)
                quot = 1;

        *baud = (port->uartclk << 2) / quot;
}

static int __init
auart_console_setup(struct console *co, char *options)
{
        struct mxs_auart_port *s;
        int baud = 9600;
        int bits = 8;
        int parity = 'n';
        int flow = 'n';
        int ret;

        /*
         * 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(auart_port))
                co->index = 0;
        s = auart_port[co->index];
        if (!s)
                return -ENODEV;

        ret = clk_prepare_enable(s->clk);
        if (ret)
                return ret;

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

        ret = uart_set_options(&s->port, co, baud, parity, bits, flow);

        clk_disable_unprepare(s->clk);

        return ret;
}

static struct console auart_console = {
        .name           = "ttyAPP",
        .write          = auart_console_write,
        .device         = uart_console_device,
        .setup          = auart_console_setup,
        .flags          = CON_PRINTBUFFER,
        .index          = -1,
        .data           = &auart_driver,
};
#endif

static struct uart_driver auart_driver = {
        .owner          = THIS_MODULE,
        .driver_name    = "ttyAPP",
        .dev_name       = "ttyAPP",
        .major          = 0,
        .minor          = 0,
        .nr             = MXS_AUART_PORTS,
#ifdef CONFIG_SERIAL_MXS_AUART_CONSOLE
        .cons =         &auart_console,
#endif
};

static void mxs_init_regs(struct mxs_auart_port *s)
{
        if (is_asm9260_auart(s))
                s->vendor = &vendor_alphascale_asm9260;
        else
                s->vendor = &vendor_freescale_stmp37xx;
}

static int mxs_get_clks(struct mxs_auart_port *s,
                        struct platform_device *pdev)
{
        int err;

        if (!is_asm9260_auart(s)) {
                s->clk = devm_clk_get(&pdev->dev, NULL);
                return PTR_ERR_OR_ZERO(s->clk);
        }

        s->clk = devm_clk_get(s->dev, "mod");
        if (IS_ERR(s->clk)) {
                dev_err(s->dev, "Failed to get \"mod\" clk\n");
                return PTR_ERR(s->clk);
        }

        s->clk_ahb = devm_clk_get(s->dev, "ahb");
        if (IS_ERR(s->clk_ahb)) {
                dev_err(s->dev, "Failed to get \"ahb\" clk\n");
                return PTR_ERR(s->clk_ahb);
        }

        err = clk_prepare_enable(s->clk_ahb);
        if (err) {
                dev_err(s->dev, "Failed to enable ahb_clk!\n");
                return err;
        }

        err = clk_set_rate(s->clk, clk_get_rate(s->clk_ahb));
        if (err) {
                dev_err(s->dev, "Failed to set rate!\n");
                goto disable_clk_ahb;
        }

        err = clk_prepare_enable(s->clk);
        if (err) {
                dev_err(s->dev, "Failed to enable clk!\n");
                goto disable_clk_ahb;
        }

        return 0;

disable_clk_ahb:
        clk_disable_unprepare(s->clk_ahb);
        return err;
}

/*
 * This function returns 1 if pdev isn't a device instatiated by dt, 0 if it
 * could successfully get all information from dt or a negative errno.
 */
static int serial_mxs_probe_dt(struct mxs_auart_port *s,
                struct platform_device *pdev)
{
        struct device_node *np = pdev->dev.of_node;
        int ret;

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

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

        if (of_get_property(np, "uart-has-rtscts", NULL) ||
            of_get_property(np, "fsl,uart-has-rtscts", NULL) /* deprecated */)
                set_bit(MXS_AUART_RTSCTS, &s->flags);

        return 0;
}

static int mxs_auart_init_gpios(struct mxs_auart_port *s, struct device *dev)
{
        enum mctrl_gpio_idx i;
        struct gpio_desc *gpiod;

        s->gpios = mctrl_gpio_init_noauto(dev, 0);
        if (IS_ERR(s->gpios))
                return PTR_ERR(s->gpios);

        /* Block (enabled before) DMA option if RTS or CTS is GPIO line */
        if (!RTS_AT_AUART() || !CTS_AT_AUART()) {
                if (test_bit(MXS_AUART_RTSCTS, &s->flags))
                        dev_warn(dev,
                                 "DMA and flow control via gpio may cause some problems. DMA disabled!\n");
                clear_bit(MXS_AUART_RTSCTS, &s->flags);
        }

        for (i = 0; i < UART_GPIO_MAX; i++) {
                gpiod = mctrl_gpio_to_gpiod(s->gpios, i);
                if (gpiod && (gpiod_get_direction(gpiod) == 1))
                        s->gpio_irq[i] = gpiod_to_irq(gpiod);
                else
                        s->gpio_irq[i] = -EINVAL;
        }

        return 0;
}

static void mxs_auart_free_gpio_irq(struct mxs_auart_port *s)
{
        enum mctrl_gpio_idx i;

        for (i = 0; i < UART_GPIO_MAX; i++)
                if (s->gpio_irq[i] >= 0)
                        free_irq(s->gpio_irq[i], s);
}

static int mxs_auart_request_gpio_irq(struct mxs_auart_port *s)
{
        int *irq = s->gpio_irq;
        enum mctrl_gpio_idx i;
        int err = 0;

        for (i = 0; (i < UART_GPIO_MAX) && !err; i++) {
                if (irq[i] < 0)
                        continue;

                irq_set_status_flags(irq[i], IRQ_NOAUTOEN);
                err = request_irq(irq[i], mxs_auart_irq_handle,
                                IRQ_TYPE_EDGE_BOTH, dev_name(s->dev), s);
                if (err)
                        dev_err(s->dev, "%s - Can't get %d irq\n",
                                __func__, irq[i]);
        }

        /*
         * If something went wrong, rollback.
         * Be careful: i may be unsigned.
         */
        while (err && (i-- > 0))
                if (irq[i] >= 0)
                        free_irq(irq[i], s);

        return err;
}

static int mxs_auart_probe(struct platform_device *pdev)
{
        const struct of_device_id *of_id =
                        of_match_device(mxs_auart_dt_ids, &pdev->dev);
        struct mxs_auart_port *s;
        u32 version;
        int ret, irq;
        struct resource *r;

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

        s->port.dev = &pdev->dev;
        s->dev = &pdev->dev;

        ret = serial_mxs_probe_dt(s, pdev);
        if (ret > 0)
                s->port.line = pdev->id < 0 ? 0 : pdev->id;
        else if (ret < 0)
                return ret;
        if (s->port.line >= ARRAY_SIZE(auart_port)) {
                dev_err(&pdev->dev, "serial%d out of range\n", s->port.line);
                return -EINVAL;
        }

        if (of_id) {
                pdev->id_entry = of_id->data;
                s->devtype = pdev->id_entry->driver_data;
        }

        ret = mxs_get_clks(s, pdev);
        if (ret)
                return ret;

        r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!r) {
                ret = -ENXIO;
                goto out_disable_clks;
        }

        s->port.mapbase = r->start;
        s->port.membase = ioremap(r->start, resource_size(r));
        if (!s->port.membase) {
                ret = -ENOMEM;
                goto out_disable_clks;
        }
        s->port.ops = &mxs_auart_ops;
        s->port.iotype = UPIO_MEM;
        s->port.fifosize = MXS_AUART_FIFO_SIZE;
        s->port.uartclk = clk_get_rate(s->clk);
        s->port.type = PORT_IMX;
        s->port.has_sysrq = IS_ENABLED(CONFIG_SERIAL_MXS_AUART_CONSOLE);

        mxs_init_regs(s);

        s->mctrl_prev = 0;

        irq = platform_get_irq(pdev, 0);
        if (irq < 0) {
                ret = irq;
                goto out_iounmap;
        }

        s->port.irq = irq;
        ret = devm_request_irq(&pdev->dev, irq, mxs_auart_irq_handle, 0,
                               dev_name(&pdev->dev), s);
        if (ret)
                goto out_iounmap;

        platform_set_drvdata(pdev, s);

        ret = mxs_auart_init_gpios(s, &pdev->dev);
        if (ret) {
                dev_err(&pdev->dev, "Failed to initialize GPIOs.\n");
                goto out_iounmap;
        }

        /*
         * Get the GPIO lines IRQ
         */
        ret = mxs_auart_request_gpio_irq(s);
        if (ret)
                goto out_iounmap;

        auart_port[s->port.line] = s;

        mxs_auart_reset_deassert(s);

        ret = uart_add_one_port(&auart_driver, &s->port);
        if (ret)
                goto out_free_qpio_irq;

        /* ASM9260 don't have version reg */
        if (is_asm9260_auart(s)) {
                dev_info(&pdev->dev, "Found APPUART ASM9260\n");
        } else {
                version = mxs_read(s, REG_VERSION);
                dev_info(&pdev->dev, "Found APPUART %d.%d.%d\n",
                         (version >> 24) & 0xff,
                         (version >> 16) & 0xff, version & 0xffff);
        }

        return 0;

out_free_qpio_irq:
        mxs_auart_free_gpio_irq(s);
        auart_port[pdev->id] = NULL;

out_iounmap:
        iounmap(s->port.membase);

out_disable_clks:
        if (is_asm9260_auart(s)) {
                clk_disable_unprepare(s->clk);
                clk_disable_unprepare(s->clk_ahb);
        }
        return ret;
}

static int mxs_auart_remove(struct platform_device *pdev)
{
        struct mxs_auart_port *s = platform_get_drvdata(pdev);

        uart_remove_one_port(&auart_driver, &s->port);
        auart_port[pdev->id] = NULL;
        mxs_auart_free_gpio_irq(s);
        iounmap(s->port.membase);
        if (is_asm9260_auart(s)) {
                clk_disable_unprepare(s->clk);
                clk_disable_unprepare(s->clk_ahb);
        }

        return 0;
}

static struct platform_driver mxs_auart_driver = {
        .probe = mxs_auart_probe,
        .remove = mxs_auart_remove,
        .driver = {
                .name = "mxs-auart",
                .of_match_table = mxs_auart_dt_ids,
        },
};

static int __init mxs_auart_init(void)
{
        int r;

        r = uart_register_driver(&auart_driver);
        if (r)
                goto out;

        r = platform_driver_register(&mxs_auart_driver);
        if (r)
                goto out_err;

        return 0;
out_err:
        uart_unregister_driver(&auart_driver);
out:
        return r;
}

static void __exit mxs_auart_exit(void)
{
        platform_driver_unregister(&mxs_auart_driver);
        uart_unregister_driver(&auart_driver);
}

module_init(mxs_auart_init);
module_exit(mxs_auart_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Freescale MXS application uart driver");
MODULE_ALIAS("platform:mxs-auart");