atmel_serial.c

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/*
 *  Driver for Atmel AT91 / AT32 Serial ports
 *  Copyright (C) 2003 Rick Bronson
 *
 *  Based on drivers/char/serial_sa1100.c, by Deep Blue Solutions Ltd.
 *  Based on drivers/char/serial.c, by Linus Torvalds, Theodore Ts'o.
 *
 *  DMA support added by Chip Coldwell.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */
#include <linux/module.h>
#include <linux/tty.h>
#include <linux/ioport.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/serial.h>
#include <linux/clk.h>
#include <linux/console.h>
#include <linux/sysrq.h>
#include <linux/tty_flip.h>
#include <linux/platform_device.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/dma-mapping.h>
#include <linux/atmel_pdc.h>
#include <linux/atmel_serial.h>
#include <linux/uaccess.h>

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

#include <asm/mach/serial_at91.h>
#include <mach/board.h>

#ifdef CONFIG_ARM
#include <mach/cpu.h>
#include <asm/gpio.h>
#endif

#define PDC_BUFFER_SIZE     512
/* Revisit: We should calculate this based on the actual port settings */
#define PDC_RX_TIMEOUT      (3 * 10)        /* 3 bytes */

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

#include <linux/serial_core.h>

static void atmel_start_rx(struct uart_port *port);
static void atmel_stop_rx(struct uart_port *port);

#ifdef CONFIG_SERIAL_ATMEL_TTYAT

/* Use device name ttyAT, major 204 and minor 154-169.  This is necessary if we
 * should coexist with the 8250 driver, such as if we have an external 16C550
 * UART. */
#define SERIAL_ATMEL_MAJOR  204
#define MINOR_START     154
#define ATMEL_DEVICENAME    "ttyAT"

#else

/* Use device name ttyS, major 4, minor 64-68.  This is the usual serial port
 * name, but it is legally reserved for the 8250 driver. */
#define SERIAL_ATMEL_MAJOR  TTY_MAJOR
#define MINOR_START     64
#define ATMEL_DEVICENAME    "ttyS"

#endif

#define ATMEL_ISR_PASS_LIMIT    256

/* UART registers. CR is write-only, hence no GET macro */
#define UART_PUT_CR(port,v) __raw_writel(v, (port)->membase + ATMEL_US_CR)
#define UART_GET_MR(port)   __raw_readl((port)->membase + ATMEL_US_MR)
#define UART_PUT_MR(port,v) __raw_writel(v, (port)->membase + ATMEL_US_MR)
#define UART_PUT_IER(port,v)    __raw_writel(v, (port)->membase + ATMEL_US_IER)
#define UART_PUT_IDR(port,v)    __raw_writel(v, (port)->membase + ATMEL_US_IDR)
#define UART_GET_IMR(port)  __raw_readl((port)->membase + ATMEL_US_IMR)
#define UART_GET_CSR(port)  __raw_readl((port)->membase + ATMEL_US_CSR)
#define UART_GET_CHAR(port) __raw_readl((port)->membase + ATMEL_US_RHR)
#define UART_PUT_CHAR(port,v)   __raw_writel(v, (port)->membase + ATMEL_US_THR)
#define UART_GET_BRGR(port) __raw_readl((port)->membase + ATMEL_US_BRGR)
#define UART_PUT_BRGR(port,v)   __raw_writel(v, (port)->membase + ATMEL_US_BRGR)
#define UART_PUT_RTOR(port,v)   __raw_writel(v, (port)->membase + ATMEL_US_RTOR)
#define UART_PUT_TTGR(port, v)  __raw_writel(v, (port)->membase + ATMEL_US_TTGR)

 /* PDC registers */
#define UART_PUT_PTCR(port,v)   __raw_writel(v, (port)->membase + ATMEL_PDC_PTCR)
#define UART_GET_PTSR(port) __raw_readl((port)->membase + ATMEL_PDC_PTSR)

#define UART_PUT_RPR(port,v)    __raw_writel(v, (port)->membase + ATMEL_PDC_RPR)
#define UART_GET_RPR(port)  __raw_readl((port)->membase + ATMEL_PDC_RPR)
#define UART_PUT_RCR(port,v)    __raw_writel(v, (port)->membase + ATMEL_PDC_RCR)
#define UART_PUT_RNPR(port,v)   __raw_writel(v, (port)->membase + ATMEL_PDC_RNPR)
#define UART_PUT_RNCR(port,v)   __raw_writel(v, (port)->membase + ATMEL_PDC_RNCR)

#define UART_PUT_TPR(port,v)    __raw_writel(v, (port)->membase + ATMEL_PDC_TPR)
#define UART_PUT_TCR(port,v)    __raw_writel(v, (port)->membase + ATMEL_PDC_TCR)
#define UART_GET_TCR(port)  __raw_readl((port)->membase + ATMEL_PDC_TCR)

static int (*atmel_open_hook)(struct uart_port *);
static void (*atmel_close_hook)(struct uart_port *);

struct atmel_dma_buffer {
    unsigned char   *buf;
    dma_addr_t  dma_addr;
    unsigned int    dma_size;
    unsigned int    ofs;
};

struct atmel_uart_char {
    u16     status;
    u16     ch;
};

#define ATMEL_SERIAL_RINGSIZE 1024

/*
 * We wrap our port structure around the generic uart_port.
 */
struct atmel_uart_port {
    struct uart_port    uart;       /* uart */
    struct clk      *clk;       /* uart clock */
    int         may_wakeup; /* cached value of device_may_wakeup for times we need to disable it */
    u32         backup_imr; /* IMR saved during suspend */
    int         break_active;   /* break being received */

    short           use_dma_rx; /* enable PDC receiver */
    short           pdc_rx_idx; /* current PDC RX buffer */
    struct atmel_dma_buffer pdc_rx[2];  /* PDC receier */

    short           use_dma_tx; /* enable PDC transmitter */
    struct atmel_dma_buffer pdc_tx;     /* PDC transmitter */

    struct tasklet_struct   tasklet;
    unsigned int        irq_status;
    unsigned int        irq_status_prev;

    struct circ_buf     rx_ring;

    struct serial_rs485 rs485;      /* rs485 settings */
    unsigned int        tx_done_mask;
};

static struct atmel_uart_port atmel_ports[ATMEL_MAX_UART];
static unsigned long atmel_ports_in_use;

#ifdef SUPPORT_SYSRQ
static struct console atmel_console;
#endif

#if defined(CONFIG_OF)
static const struct of_device_id atmel_serial_dt_ids[] = {
    { .compatible = "atmel,at91rm9200-usart" },
    { .compatible = "atmel,at91sam9260-usart" },
    { /* sentinel */ }
};

MODULE_DEVICE_TABLE(of, atmel_serial_dt_ids);
#endif

static inline struct atmel_uart_port *
to_atmel_uart_port(struct uart_port *uart)
{
    return container_of(uart, struct atmel_uart_port, uart);
}

#ifdef CONFIG_SERIAL_ATMEL_PDC
static bool atmel_use_dma_rx(struct uart_port *port)
{
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

    return atmel_port->use_dma_rx;
}

static bool atmel_use_dma_tx(struct uart_port *port)
{
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

    return atmel_port->use_dma_tx;
}
#else
static bool atmel_use_dma_rx(struct uart_port *port)
{
    return false;
}

static bool atmel_use_dma_tx(struct uart_port *port)
{
    return false;
}
#endif

/* Enable or disable the rs485 support */
void atmel_config_rs485(struct uart_port *port, struct serial_rs485 *rs485conf)
{
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
    unsigned int mode;
    unsigned long flags;

    spin_lock_irqsave(&port->lock, flags);

    /* Disable interrupts */
    UART_PUT_IDR(port, atmel_port->tx_done_mask);

    mode = UART_GET_MR(port);

    /* Resetting serial mode to RS232 (0x0) */
    mode &= ~ATMEL_US_USMODE;

    atmel_port->rs485 = *rs485conf;

    if (rs485conf->flags & SER_RS485_ENABLED) {
        dev_dbg(port->dev, "Setting UART to RS485\n");
        atmel_port->tx_done_mask = ATMEL_US_TXEMPTY;
        if ((rs485conf->delay_rts_after_send) > 0)
            UART_PUT_TTGR(port, rs485conf->delay_rts_after_send);
        mode |= ATMEL_US_USMODE_RS485;
    } else {
        dev_dbg(port->dev, "Setting UART to RS232\n");
        if (atmel_use_dma_tx(port))
            atmel_port->tx_done_mask = ATMEL_US_ENDTX |
                ATMEL_US_TXBUFE;
        else
            atmel_port->tx_done_mask = ATMEL_US_TXRDY;
    }
    UART_PUT_MR(port, mode);

    /* Enable interrupts */
    UART_PUT_IER(port, atmel_port->tx_done_mask);

    spin_unlock_irqrestore(&port->lock, flags);

}

/*
 * Return TIOCSER_TEMT when transmitter FIFO and Shift register is empty.
 */
static u_int atmel_tx_empty(struct uart_port *port)
{
    return (UART_GET_CSR(port) & ATMEL_US_TXEMPTY) ? TIOCSER_TEMT : 0;
}

/*
 * Set state of the modem control output lines
 */
static void atmel_set_mctrl(struct uart_port *port, u_int mctrl)
{
    unsigned int control = 0;
    unsigned int mode;
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

#ifdef CONFIG_ARCH_AT91RM9200
    if (cpu_is_at91rm9200()) {
        /*
         * AT91RM9200 Errata #39: RTS0 is not internally connected
         * to PA21. We need to drive the pin manually.
         */
        if (port->mapbase == AT91RM9200_BASE_US0) {
            if (mctrl & TIOCM_RTS)
                at91_set_gpio_value(AT91_PIN_PA21, 0);
            else
                at91_set_gpio_value(AT91_PIN_PA21, 1);
        }
    }
#endif

    if (mctrl & TIOCM_RTS)
        control |= ATMEL_US_RTSEN;
    else
        control |= ATMEL_US_RTSDIS;

    if (mctrl & TIOCM_DTR)
        control |= ATMEL_US_DTREN;
    else
        control |= ATMEL_US_DTRDIS;

    UART_PUT_CR(port, control);

    /* Local loopback mode? */
    mode = UART_GET_MR(port) & ~ATMEL_US_CHMODE;
    if (mctrl & TIOCM_LOOP)
        mode |= ATMEL_US_CHMODE_LOC_LOOP;
    else
        mode |= ATMEL_US_CHMODE_NORMAL;

    /* Resetting serial mode to RS232 (0x0) */
    mode &= ~ATMEL_US_USMODE;

    if (atmel_port->rs485.flags & SER_RS485_ENABLED) {
        dev_dbg(port->dev, "Setting UART to RS485\n");
        if ((atmel_port->rs485.delay_rts_after_send) > 0)
            UART_PUT_TTGR(port,
                    atmel_port->rs485.delay_rts_after_send);
        mode |= ATMEL_US_USMODE_RS485;
    } else {
        dev_dbg(port->dev, "Setting UART to RS232\n");
    }
    UART_PUT_MR(port, mode);
}

/*
 * Get state of the modem control input lines
 */
static u_int atmel_get_mctrl(struct uart_port *port)
{
    unsigned int status, ret = 0;

    status = UART_GET_CSR(port);

    /*
     * The control signals are active low.
     */
    if (!(status & ATMEL_US_DCD))
        ret |= TIOCM_CD;
    if (!(status & ATMEL_US_CTS))
        ret |= TIOCM_CTS;
    if (!(status & ATMEL_US_DSR))
        ret |= TIOCM_DSR;
    if (!(status & ATMEL_US_RI))
        ret |= TIOCM_RI;

    return ret;
}

/*
 * Stop transmitting.
 */
static void atmel_stop_tx(struct uart_port *port)
{
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

    if (atmel_use_dma_tx(port)) {
        /* disable PDC transmit */
        UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS);
    }
    /* Disable interrupts */
    UART_PUT_IDR(port, atmel_port->tx_done_mask);

    if ((atmel_port->rs485.flags & SER_RS485_ENABLED) &&
        !(atmel_port->rs485.flags & SER_RS485_RX_DURING_TX))
        atmel_start_rx(port);
}

/*
 * Start transmitting.
 */
static void atmel_start_tx(struct uart_port *port)
{
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

    if (atmel_use_dma_tx(port)) {
        if (UART_GET_PTSR(port) & ATMEL_PDC_TXTEN)
            /* The transmitter is already running.  Yes, we
               really need this.*/
            return;

        if ((atmel_port->rs485.flags & SER_RS485_ENABLED) &&
            !(atmel_port->rs485.flags & SER_RS485_RX_DURING_TX))
            atmel_stop_rx(port);

        /* re-enable PDC transmit */
        UART_PUT_PTCR(port, ATMEL_PDC_TXTEN);
    }
    /* Enable interrupts */
    UART_PUT_IER(port, atmel_port->tx_done_mask);
}

/*
 * start receiving - port is in process of being opened.
 */
static void atmel_start_rx(struct uart_port *port)
{
    UART_PUT_CR(port, ATMEL_US_RSTSTA);  /* reset status and receiver */

    UART_PUT_CR(port, ATMEL_US_RXEN);

    if (atmel_use_dma_rx(port)) {
        /* enable PDC controller */
        UART_PUT_IER(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT |
            port->read_status_mask);
        UART_PUT_PTCR(port, ATMEL_PDC_RXTEN);
    } else {
        UART_PUT_IER(port, ATMEL_US_RXRDY);
    }
}

/*
 * Stop receiving - port is in process of being closed.
 */
static void atmel_stop_rx(struct uart_port *port)
{
    UART_PUT_CR(port, ATMEL_US_RXDIS);

    if (atmel_use_dma_rx(port)) {
        /* disable PDC receive */
        UART_PUT_PTCR(port, ATMEL_PDC_RXTDIS);
        UART_PUT_IDR(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT |
            port->read_status_mask);
    } else {
        UART_PUT_IDR(port, ATMEL_US_RXRDY);
    }
}

/*
 * Enable modem status interrupts
 */
static void atmel_enable_ms(struct uart_port *port)
{
    UART_PUT_IER(port, ATMEL_US_RIIC | ATMEL_US_DSRIC
            | ATMEL_US_DCDIC | ATMEL_US_CTSIC);
}

/*
 * Control the transmission of a break signal
 */
static void atmel_break_ctl(struct uart_port *port, int break_state)
{
    if (break_state != 0)
        UART_PUT_CR(port, ATMEL_US_STTBRK); /* start break */
    else
        UART_PUT_CR(port, ATMEL_US_STPBRK); /* stop break */
}

/*
 * Stores the incoming character in the ring buffer
 */
static void
atmel_buffer_rx_char(struct uart_port *port, unsigned int status,
             unsigned int ch)
{
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
    struct circ_buf *ring = &atmel_port->rx_ring;
    struct atmel_uart_char *c;

    if (!CIRC_SPACE(ring->head, ring->tail, ATMEL_SERIAL_RINGSIZE))
        /* Buffer overflow, ignore char */
        return;

    c = &((struct atmel_uart_char *)ring->buf)[ring->head];
    c->status   = status;
    c->ch       = ch;

    /* Make sure the character is stored before we update head. */
    smp_wmb();

    ring->head = (ring->head + 1) & (ATMEL_SERIAL_RINGSIZE - 1);
}

/*
 * Deal with parity, framing and overrun errors.
 */
static void atmel_pdc_rxerr(struct uart_port *port, unsigned int status)
{
    /* clear error */
    UART_PUT_CR(port, ATMEL_US_RSTSTA);

    if (status & ATMEL_US_RXBRK) {
        /* ignore side-effect */
        status &= ~(ATMEL_US_PARE | ATMEL_US_FRAME);
        port->icount.brk++;
    }
    if (status & ATMEL_US_PARE)
        port->icount.parity++;
    if (status & ATMEL_US_FRAME)
        port->icount.frame++;
    if (status & ATMEL_US_OVRE)
        port->icount.overrun++;
}

/*
 * Characters received (called from interrupt handler)
 */
static void atmel_rx_chars(struct uart_port *port)
{
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
    unsigned int status, ch;

    status = UART_GET_CSR(port);
    while (status & ATMEL_US_RXRDY) {
        ch = UART_GET_CHAR(port);

        /*
         * note that the error handling code is
         * out of the main execution path
         */
        if (unlikely(status & (ATMEL_US_PARE | ATMEL_US_FRAME
                       | ATMEL_US_OVRE | ATMEL_US_RXBRK)
                 || atmel_port->break_active)) {

            /* clear error */
            UART_PUT_CR(port, ATMEL_US_RSTSTA);

            if (status & ATMEL_US_RXBRK
                && !atmel_port->break_active) {
                atmel_port->break_active = 1;
                UART_PUT_IER(port, ATMEL_US_RXBRK);
            } else {
                /*
                 * This is either the end-of-break
                 * condition or we've received at
                 * least one character without RXBRK
                 * being set. In both cases, the next
                 * RXBRK will indicate start-of-break.
                 */
                UART_PUT_IDR(port, ATMEL_US_RXBRK);
                status &= ~ATMEL_US_RXBRK;
                atmel_port->break_active = 0;
            }
        }

        atmel_buffer_rx_char(port, status, ch);
        status = UART_GET_CSR(port);
    }

    tasklet_schedule(&atmel_port->tasklet);
}

/*
 * Transmit characters (called from tasklet with TXRDY interrupt
 * disabled)
 */
static void atmel_tx_chars(struct uart_port *port)
{
    struct circ_buf *xmit = &port->state->xmit;
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

    if (port->x_char && UART_GET_CSR(port) & atmel_port->tx_done_mask) {
        UART_PUT_CHAR(port, port->x_char);
        port->icount.tx++;
        port->x_char = 0;
    }
    if (uart_circ_empty(xmit) || uart_tx_stopped(port))
        return;

    while (UART_GET_CSR(port) & atmel_port->tx_done_mask) {
        UART_PUT_CHAR(port, xmit->buf[xmit->tail]);
        xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
        port->icount.tx++;
        if (uart_circ_empty(xmit))
            break;
    }

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

    if (!uart_circ_empty(xmit))
        /* Enable interrupts */
        UART_PUT_IER(port, atmel_port->tx_done_mask);
}

/*
 * receive interrupt handler.
 */
static void
atmel_handle_receive(struct uart_port *port, unsigned int pending)
{
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

    if (atmel_use_dma_rx(port)) {
        /*
         * PDC receive. Just schedule the tasklet and let it
         * figure out the details.
         *
         * TODO: We're not handling error flags correctly at
         * the moment.
         */
        if (pending & (ATMEL_US_ENDRX | ATMEL_US_TIMEOUT)) {
            UART_PUT_IDR(port, (ATMEL_US_ENDRX
                        | ATMEL_US_TIMEOUT));
            tasklet_schedule(&atmel_port->tasklet);
        }

        if (pending & (ATMEL_US_RXBRK | ATMEL_US_OVRE |
                ATMEL_US_FRAME | ATMEL_US_PARE))
            atmel_pdc_rxerr(port, pending);
    }

    /* Interrupt receive */
    if (pending & ATMEL_US_RXRDY)
        atmel_rx_chars(port);
    else if (pending & ATMEL_US_RXBRK) {
        /*
         * End of break detected. If it came along with a
         * character, atmel_rx_chars will handle it.
         */
        UART_PUT_CR(port, ATMEL_US_RSTSTA);
        UART_PUT_IDR(port, ATMEL_US_RXBRK);
        atmel_port->break_active = 0;
    }
}

/*
 * transmit interrupt handler. (Transmit is IRQF_NODELAY safe)
 */
static void
atmel_handle_transmit(struct uart_port *port, unsigned int pending)
{
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

    if (pending & atmel_port->tx_done_mask) {
        /* Either PDC or interrupt transmission */
        UART_PUT_IDR(port, atmel_port->tx_done_mask);
        tasklet_schedule(&atmel_port->tasklet);
    }
}

/*
 * status flags interrupt handler.
 */
static void
atmel_handle_status(struct uart_port *port, unsigned int pending,
            unsigned int status)
{
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

    if (pending & (ATMEL_US_RIIC | ATMEL_US_DSRIC | ATMEL_US_DCDIC
                | ATMEL_US_CTSIC)) {
        atmel_port->irq_status = status;
        tasklet_schedule(&atmel_port->tasklet);
    }
}

/*
 * Interrupt handler
 */
static irqreturn_t atmel_interrupt(int irq, void *dev_id)
{
    struct uart_port *port = dev_id;
    unsigned int status, pending, pass_counter = 0;

    do {
        status = UART_GET_CSR(port);
        pending = status & UART_GET_IMR(port);
        if (!pending)
            break;

        atmel_handle_receive(port, pending);
        atmel_handle_status(port, pending, status);
        atmel_handle_transmit(port, pending);
    } while (pass_counter++ < ATMEL_ISR_PASS_LIMIT);

    return pass_counter ? IRQ_HANDLED : IRQ_NONE;
}

/*
 * Called from tasklet with ENDTX and TXBUFE interrupts disabled.
 */
static void atmel_tx_dma(struct uart_port *port)
{
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
    struct circ_buf *xmit = &port->state->xmit;
    struct atmel_dma_buffer *pdc = &atmel_port->pdc_tx;
    int count;

    /* nothing left to transmit? */
    if (UART_GET_TCR(port))
        return;

    xmit->tail += pdc->ofs;
    xmit->tail &= UART_XMIT_SIZE - 1;

    port->icount.tx += pdc->ofs;
    pdc->ofs = 0;

    /* more to transmit - setup next transfer */

    /* disable PDC transmit */
    UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS);

    if (!uart_circ_empty(xmit) && !uart_tx_stopped(port)) {
        dma_sync_single_for_device(port->dev,
                       pdc->dma_addr,
                       pdc->dma_size,
                       DMA_TO_DEVICE);

        count = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
        pdc->ofs = count;

        UART_PUT_TPR(port, pdc->dma_addr + xmit->tail);
        UART_PUT_TCR(port, count);
        /* re-enable PDC transmit */
        UART_PUT_PTCR(port, ATMEL_PDC_TXTEN);
        /* Enable interrupts */
        UART_PUT_IER(port, atmel_port->tx_done_mask);
    } else {
        if ((atmel_port->rs485.flags & SER_RS485_ENABLED) &&
            !(atmel_port->rs485.flags & SER_RS485_RX_DURING_TX)) {
            /* DMA done, stop TX, start RX for RS485 */
            atmel_start_rx(port);
        }
    }

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

static void atmel_rx_from_ring(struct uart_port *port)
{
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
    struct circ_buf *ring = &atmel_port->rx_ring;
    unsigned int flg;
    unsigned int status;

    while (ring->head != ring->tail) {
        struct atmel_uart_char c;

        /* Make sure c is loaded after head. */
        smp_rmb();

        c = ((struct atmel_uart_char *)ring->buf)[ring->tail];

        ring->tail = (ring->tail + 1) & (ATMEL_SERIAL_RINGSIZE - 1);

        port->icount.rx++;
        status = c.status;
        flg = TTY_NORMAL;

        /*
         * note that the error handling code is
         * out of the main execution path
         */
        if (unlikely(status & (ATMEL_US_PARE | ATMEL_US_FRAME
                       | ATMEL_US_OVRE | ATMEL_US_RXBRK))) {
            if (status & ATMEL_US_RXBRK) {
                /* ignore side-effect */
                status &= ~(ATMEL_US_PARE | ATMEL_US_FRAME);

                port->icount.brk++;
                if (uart_handle_break(port))
                    continue;
            }
            if (status & ATMEL_US_PARE)
                port->icount.parity++;
            if (status & ATMEL_US_FRAME)
                port->icount.frame++;
            if (status & ATMEL_US_OVRE)
                port->icount.overrun++;

            status &= port->read_status_mask;

            if (status & ATMEL_US_RXBRK)
                flg = TTY_BREAK;
            else if (status & ATMEL_US_PARE)
                flg = TTY_PARITY;
            else if (status & ATMEL_US_FRAME)
                flg = TTY_FRAME;
        }


        if (uart_handle_sysrq_char(port, c.ch))
            continue;

        uart_insert_char(port, status, ATMEL_US_OVRE, c.ch, flg);
    }

    /*
     * Drop the lock here since it might end up calling
     * uart_start(), which takes the lock.
     */
    spin_unlock(&port->lock);
    tty_flip_buffer_push(port->state->port.tty);
    spin_lock(&port->lock);
}

static void atmel_rx_from_dma(struct uart_port *port)
{
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
    struct tty_struct *tty = port->state->port.tty;
    struct atmel_dma_buffer *pdc;
    int rx_idx = atmel_port->pdc_rx_idx;
    unsigned int head;
    unsigned int tail;
    unsigned int count;

    do {
        /* Reset the UART timeout early so that we don't miss one */
        UART_PUT_CR(port, ATMEL_US_STTTO);

        pdc = &atmel_port->pdc_rx[rx_idx];
        head = UART_GET_RPR(port) - pdc->dma_addr;
        tail = pdc->ofs;

        /* If the PDC has switched buffers, RPR won't contain
         * any address within the current buffer. Since head
         * is unsigned, we just need a one-way comparison to
         * find out.
         *
         * In this case, we just need to consume the entire
         * buffer and resubmit it for DMA. This will clear the
         * ENDRX bit as well, so that we can safely re-enable
         * all interrupts below.
         */
        head = min(head, pdc->dma_size);

        if (likely(head != tail)) {
            dma_sync_single_for_cpu(port->dev, pdc->dma_addr,
                    pdc->dma_size, DMA_FROM_DEVICE);

            /*
             * head will only wrap around when we recycle
             * the DMA buffer, and when that happens, we
             * explicitly set tail to 0. So head will
             * always be greater than tail.
             */
            count = head - tail;

            tty_insert_flip_string(tty, pdc->buf + pdc->ofs, count);

            dma_sync_single_for_device(port->dev, pdc->dma_addr,
                    pdc->dma_size, DMA_FROM_DEVICE);

            port->icount.rx += count;
            pdc->ofs = head;
        }

        /*
         * If the current buffer is full, we need to check if
         * the next one contains any additional data.
         */
        if (head >= pdc->dma_size) {
            pdc->ofs = 0;
            UART_PUT_RNPR(port, pdc->dma_addr);
            UART_PUT_RNCR(port, pdc->dma_size);

            rx_idx = !rx_idx;
            atmel_port->pdc_rx_idx = rx_idx;
        }
    } while (head >= pdc->dma_size);

    /*
     * Drop the lock here since it might end up calling
     * uart_start(), which takes the lock.
     */
    spin_unlock(&port->lock);
    tty_flip_buffer_push(tty);
    spin_lock(&port->lock);

    UART_PUT_IER(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT);
}

/*
 * tasklet handling tty stuff outside the interrupt handler.
 */
static void atmel_tasklet_func(unsigned long data)
{
    struct uart_port *port = (struct uart_port *)data;
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
    unsigned int status;
    unsigned int status_change;

    /* The interrupt handler does not take the lock */
    spin_lock(&port->lock);

    if (atmel_use_dma_tx(port))
        atmel_tx_dma(port);
    else
        atmel_tx_chars(port);

    status = atmel_port->irq_status;
    status_change = status ^ atmel_port->irq_status_prev;

    if (status_change & (ATMEL_US_RI | ATMEL_US_DSR
                | ATMEL_US_DCD | ATMEL_US_CTS)) {
        /* TODO: All reads to CSR will clear these interrupts! */
        if (status_change & ATMEL_US_RI)
            port->icount.rng++;
        if (status_change & ATMEL_US_DSR)
            port->icount.dsr++;
        if (status_change & ATMEL_US_DCD)
            uart_handle_dcd_change(port, !(status & ATMEL_US_DCD));
        if (status_change & ATMEL_US_CTS)
            uart_handle_cts_change(port, !(status & ATMEL_US_CTS));

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

        atmel_port->irq_status_prev = status;
    }

    if (atmel_use_dma_rx(port))
        atmel_rx_from_dma(port);
    else
        atmel_rx_from_ring(port);

    spin_unlock(&port->lock);
}

/*
 * Perform initialization and enable port for reception
 */
static int atmel_startup(struct uart_port *port)
{
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
    struct tty_struct *tty = port->state->port.tty;
    int retval;

    /*
     * Ensure that no interrupts are enabled otherwise when
     * request_irq() is called we could get stuck trying to
     * handle an unexpected interrupt
     */
    UART_PUT_IDR(port, -1);

    /*
     * Allocate the IRQ
     */
    retval = request_irq(port->irq, atmel_interrupt, IRQF_SHARED,
            tty ? tty->name : "atmel_serial", port);
    if (retval) {
        printk("atmel_serial: atmel_startup - Can't get irq\n");
        return retval;
    }

    /*
     * Initialize DMA (if necessary)
     */
    if (atmel_use_dma_rx(port)) {
        int i;

        for (i = 0; i < 2; i++) {
            struct atmel_dma_buffer *pdc = &atmel_port->pdc_rx[i];

            pdc->buf = kmalloc(PDC_BUFFER_SIZE, GFP_KERNEL);
            if (pdc->buf == NULL) {
                if (i != 0) {
                    dma_unmap_single(port->dev,
                        atmel_port->pdc_rx[0].dma_addr,
                        PDC_BUFFER_SIZE,
                        DMA_FROM_DEVICE);
                    kfree(atmel_port->pdc_rx[0].buf);
                }
                free_irq(port->irq, port);
                return -ENOMEM;
            }
            pdc->dma_addr = dma_map_single(port->dev,
                               pdc->buf,
                               PDC_BUFFER_SIZE,
                               DMA_FROM_DEVICE);
            pdc->dma_size = PDC_BUFFER_SIZE;
            pdc->ofs = 0;
        }

        atmel_port->pdc_rx_idx = 0;

        UART_PUT_RPR(port, atmel_port->pdc_rx[0].dma_addr);
        UART_PUT_RCR(port, PDC_BUFFER_SIZE);

        UART_PUT_RNPR(port, atmel_port->pdc_rx[1].dma_addr);
        UART_PUT_RNCR(port, PDC_BUFFER_SIZE);
    }
    if (atmel_use_dma_tx(port)) {
        struct atmel_dma_buffer *pdc = &atmel_port->pdc_tx;
        struct circ_buf *xmit = &port->state->xmit;

        pdc->buf = xmit->buf;
        pdc->dma_addr = dma_map_single(port->dev,
                           pdc->buf,
                           UART_XMIT_SIZE,
                           DMA_TO_DEVICE);
        pdc->dma_size = UART_XMIT_SIZE;
        pdc->ofs = 0;
    }

    /*
     * If there is a specific "open" function (to register
     * control line interrupts)
     */
    if (atmel_open_hook) {
        retval = atmel_open_hook(port);
        if (retval) {
            free_irq(port->irq, port);
            return retval;
        }
    }

    /* Save current CSR for comparison in atmel_tasklet_func() */
    atmel_port->irq_status_prev = UART_GET_CSR(port);
    atmel_port->irq_status = atmel_port->irq_status_prev;

    /*
     * Finally, enable the serial port
     */
    UART_PUT_CR(port, ATMEL_US_RSTSTA | ATMEL_US_RSTRX);
    /* enable xmit & rcvr */
    UART_PUT_CR(port, ATMEL_US_TXEN | ATMEL_US_RXEN);

    if (atmel_use_dma_rx(port)) {
        /* set UART timeout */
        UART_PUT_RTOR(port, PDC_RX_TIMEOUT);
        UART_PUT_CR(port, ATMEL_US_STTTO);

        UART_PUT_IER(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT);
        /* enable PDC controller */
        UART_PUT_PTCR(port, ATMEL_PDC_RXTEN);
    } else {
        /* enable receive only */
        UART_PUT_IER(port, ATMEL_US_RXRDY);
    }

    return 0;
}

/*
 * Disable the port
 */
static void atmel_shutdown(struct uart_port *port)
{
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
    /*
     * Ensure everything is stopped.
     */
    atmel_stop_rx(port);
    atmel_stop_tx(port);

    /*
     * Shut-down the DMA.
     */
    if (atmel_use_dma_rx(port)) {
        int i;

        for (i = 0; i < 2; i++) {
            struct atmel_dma_buffer *pdc = &atmel_port->pdc_rx[i];

            dma_unmap_single(port->dev,
                     pdc->dma_addr,
                     pdc->dma_size,
                     DMA_FROM_DEVICE);
            kfree(pdc->buf);
        }
    }
    if (atmel_use_dma_tx(port)) {
        struct atmel_dma_buffer *pdc = &atmel_port->pdc_tx;

        dma_unmap_single(port->dev,
                 pdc->dma_addr,
                 pdc->dma_size,
                 DMA_TO_DEVICE);
    }

    /*
     * Disable all interrupts, port and break condition.
     */
    UART_PUT_CR(port, ATMEL_US_RSTSTA);
    UART_PUT_IDR(port, -1);

    /*
     * Free the interrupt
     */
    free_irq(port->irq, port);

    /*
     * If there is a specific "close" function (to unregister
     * control line interrupts)
     */
    if (atmel_close_hook)
        atmel_close_hook(port);
}

/*
 * Flush any TX data submitted for DMA. Called when the TX circular
 * buffer is reset.
 */
static void atmel_flush_buffer(struct uart_port *port)
{
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

    if (atmel_use_dma_tx(port)) {
        UART_PUT_TCR(port, 0);
        atmel_port->pdc_tx.ofs = 0;
    }
}

/*
 * Power / Clock management.
 */
static void atmel_serial_pm(struct uart_port *port, unsigned int state,
                unsigned int oldstate)
{
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

    switch (state) {
    case 0:
        /*
         * Enable the peripheral clock for this serial port.
         * This is called on uart_open() or a resume event.
         */
        clk_enable(atmel_port->clk);

        /* re-enable interrupts if we disabled some on suspend */
        UART_PUT_IER(port, atmel_port->backup_imr);
        break;
    case 3:
        /* Back up the interrupt mask and disable all interrupts */
        atmel_port->backup_imr = UART_GET_IMR(port);
        UART_PUT_IDR(port, -1);

        /*
         * Disable the peripheral clock for this serial port.
         * This is called on uart_close() or a suspend event.
         */
        clk_disable(atmel_port->clk);
        break;
    default:
        printk(KERN_ERR "atmel_serial: unknown pm %d\n", state);
    }
}

/*
 * Change the port parameters
 */
static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
                  struct ktermios *old)
{
    unsigned long flags;
    unsigned int mode, imr, quot, baud;
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

    /* Get current mode register */
    mode = UART_GET_MR(port) & ~(ATMEL_US_USCLKS | ATMEL_US_CHRL
                    | ATMEL_US_NBSTOP | ATMEL_US_PAR
                    | ATMEL_US_USMODE);

    baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk / 16);
    quot = uart_get_divisor(port, baud);

    if (quot > 65535) { /* BRGR is 16-bit, so switch to slower clock */
        quot /= 8;
        mode |= ATMEL_US_USCLKS_MCK_DIV8;
    }

    /* byte size */
    switch (termios->c_cflag & CSIZE) {
    case CS5:
        mode |= ATMEL_US_CHRL_5;
        break;
    case CS6:
        mode |= ATMEL_US_CHRL_6;
        break;
    case CS7:
        mode |= ATMEL_US_CHRL_7;
        break;
    default:
        mode |= ATMEL_US_CHRL_8;
        break;
    }

    /* stop bits */
    if (termios->c_cflag & CSTOPB)
        mode |= ATMEL_US_NBSTOP_2;

    /* parity */
    if (termios->c_cflag & PARENB) {
        /* Mark or Space parity */
        if (termios->c_cflag & CMSPAR) {
            if (termios->c_cflag & PARODD)
                mode |= ATMEL_US_PAR_MARK;
            else
                mode |= ATMEL_US_PAR_SPACE;
        } else if (termios->c_cflag & PARODD)
            mode |= ATMEL_US_PAR_ODD;
        else
            mode |= ATMEL_US_PAR_EVEN;
    } else
        mode |= ATMEL_US_PAR_NONE;

    /* hardware handshake (RTS/CTS) */
    if (termios->c_cflag & CRTSCTS)
        mode |= ATMEL_US_USMODE_HWHS;
    else
        mode |= ATMEL_US_USMODE_NORMAL;

    spin_lock_irqsave(&port->lock, flags);

    port->read_status_mask = ATMEL_US_OVRE;
    if (termios->c_iflag & INPCK)
        port->read_status_mask |= (ATMEL_US_FRAME | ATMEL_US_PARE);
    if (termios->c_iflag & (BRKINT | PARMRK))
        port->read_status_mask |= ATMEL_US_RXBRK;

    if (atmel_use_dma_rx(port))
        /* need to enable error interrupts */
        UART_PUT_IER(port, port->read_status_mask);

    /*
     * Characters to ignore
     */
    port->ignore_status_mask = 0;
    if (termios->c_iflag & IGNPAR)
        port->ignore_status_mask |= (ATMEL_US_FRAME | ATMEL_US_PARE);
    if (termios->c_iflag & IGNBRK) {
        port->ignore_status_mask |= ATMEL_US_RXBRK;
        /*
         * If we're ignoring parity and break indicators,
         * ignore overruns too (for real raw support).
         */
        if (termios->c_iflag & IGNPAR)
            port->ignore_status_mask |= ATMEL_US_OVRE;
    }
    /* TODO: Ignore all characters if CREAD is set.*/

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

    /*
     * save/disable interrupts. The tty layer will ensure that the
     * transmitter is empty if requested by the caller, so there's
     * no need to wait for it here.
     */
    imr = UART_GET_IMR(port);
    UART_PUT_IDR(port, -1);

    /* disable receiver and transmitter */
    UART_PUT_CR(port, ATMEL_US_TXDIS | ATMEL_US_RXDIS);

    /* Resetting serial mode to RS232 (0x0) */
    mode &= ~ATMEL_US_USMODE;

    if (atmel_port->rs485.flags & SER_RS485_ENABLED) {
        dev_dbg(port->dev, "Setting UART to RS485\n");
        if ((atmel_port->rs485.delay_rts_after_send) > 0)
            UART_PUT_TTGR(port,
                    atmel_port->rs485.delay_rts_after_send);
        mode |= ATMEL_US_USMODE_RS485;
    } else {
        dev_dbg(port->dev, "Setting UART to RS232\n");
    }

    /* set the parity, stop bits and data size */
    UART_PUT_MR(port, mode);

    /* set the baud rate */
    UART_PUT_BRGR(port, quot);
    UART_PUT_CR(port, ATMEL_US_RSTSTA | ATMEL_US_RSTRX);
    UART_PUT_CR(port, ATMEL_US_TXEN | ATMEL_US_RXEN);

    /* restore interrupts */
    UART_PUT_IER(port, imr);

    /* CTS flow-control and modem-status interrupts */
    if (UART_ENABLE_MS(port, termios->c_cflag))
        port->ops->enable_ms(port);

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

static void atmel_set_ldisc(struct uart_port *port, int new)
{
    if (new == N_PPS) {
        port->flags |= UPF_HARDPPS_CD;
        atmel_enable_ms(port);
    } else {
        port->flags &= ~UPF_HARDPPS_CD;
    }
}

/*
 * Return string describing the specified port
 */
static const char *atmel_type(struct uart_port *port)
{
    return (port->type == PORT_ATMEL) ? "ATMEL_SERIAL" : NULL;
}

/*
 * Release the memory region(s) being used by 'port'.
 */
static void atmel_release_port(struct uart_port *port)
{
    struct platform_device *pdev = to_platform_device(port->dev);
    int size = pdev->resource[0].end - pdev->resource[0].start + 1;

    release_mem_region(port->mapbase, size);

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

/*
 * Request the memory region(s) being used by 'port'.
 */
static int atmel_request_port(struct uart_port *port)
{
    struct platform_device *pdev = to_platform_device(port->dev);
    int size = pdev->resource[0].end - pdev->resource[0].start + 1;

    if (!request_mem_region(port->mapbase, size, "atmel_serial"))
        return -EBUSY;

    if (port->flags & UPF_IOREMAP) {
        port->membase = ioremap(port->mapbase, size);
        if (port->membase == NULL) {
            release_mem_region(port->mapbase, size);
            return -ENOMEM;
        }
    }

    return 0;
}

/*
 * Configure/autoconfigure the port.
 */
static void atmel_config_port(struct uart_port *port, int flags)
{
    if (flags & UART_CONFIG_TYPE) {
        port->type = PORT_ATMEL;
        atmel_request_port(port);
    }
}

/*
 * Verify the new serial_struct (for TIOCSSERIAL).
 */
static int atmel_verify_port(struct uart_port *port, struct serial_struct *ser)
{
    int ret = 0;
    if (ser->type != PORT_UNKNOWN && ser->type != PORT_ATMEL)
        ret = -EINVAL;
    if (port->irq != ser->irq)
        ret = -EINVAL;
    if (ser->io_type != SERIAL_IO_MEM)
        ret = -EINVAL;
    if (port->uartclk / 16 != ser->baud_base)
        ret = -EINVAL;
    if ((void *)port->mapbase != ser->iomem_base)
        ret = -EINVAL;
    if (port->iobase != ser->port)
        ret = -EINVAL;
    if (ser->hub6 != 0)
        ret = -EINVAL;
    return ret;
}

#ifdef CONFIG_CONSOLE_POLL
static int atmel_poll_get_char(struct uart_port *port)
{
    while (!(UART_GET_CSR(port) & ATMEL_US_RXRDY))
        cpu_relax();

    return UART_GET_CHAR(port);
}

static void atmel_poll_put_char(struct uart_port *port, unsigned char ch)
{
    while (!(UART_GET_CSR(port) & ATMEL_US_TXRDY))
        cpu_relax();

    UART_PUT_CHAR(port, ch);
}
#endif

static int
atmel_ioctl(struct uart_port *port, unsigned int cmd, unsigned long arg)
{
    struct serial_rs485 rs485conf;

    switch (cmd) {
    case TIOCSRS485:
        if (copy_from_user(&rs485conf, (struct serial_rs485 *) arg,
                    sizeof(rs485conf)))
            return -EFAULT;

        atmel_config_rs485(port, &rs485conf);
        break;

    case TIOCGRS485:
        if (copy_to_user((struct serial_rs485 *) arg,
                    &(to_atmel_uart_port(port)->rs485),
                    sizeof(rs485conf)))
            return -EFAULT;
        break;

    default:
        return -ENOIOCTLCMD;
    }
    return 0;
}



static struct uart_ops atmel_pops = {
    .tx_empty   = atmel_tx_empty,
    .set_mctrl  = atmel_set_mctrl,
    .get_mctrl  = atmel_get_mctrl,
    .stop_tx    = atmel_stop_tx,
    .start_tx   = atmel_start_tx,
    .stop_rx    = atmel_stop_rx,
    .enable_ms  = atmel_enable_ms,
    .break_ctl  = atmel_break_ctl,
    .startup    = atmel_startup,
    .shutdown   = atmel_shutdown,
    .flush_buffer   = atmel_flush_buffer,
    .set_termios    = atmel_set_termios,
    .set_ldisc  = atmel_set_ldisc,
    .type       = atmel_type,
    .release_port   = atmel_release_port,
    .request_port   = atmel_request_port,
    .config_port    = atmel_config_port,
    .verify_port    = atmel_verify_port,
    .pm     = atmel_serial_pm,
    .ioctl      = atmel_ioctl,
#ifdef CONFIG_CONSOLE_POLL
    .poll_get_char  = atmel_poll_get_char,
    .poll_put_char  = atmel_poll_put_char,
#endif
};

static void __devinit atmel_of_init_port(struct atmel_uart_port *atmel_port,
                     struct device_node *np)
{
    u32 rs485_delay[2];

    /* DMA/PDC usage specification */
    if (of_get_property(np, "atmel,use-dma-rx", NULL))
        atmel_port->use_dma_rx  = 1;
    else
        atmel_port->use_dma_rx  = 0;
    if (of_get_property(np, "atmel,use-dma-tx", NULL))
        atmel_port->use_dma_tx  = 1;
    else
        atmel_port->use_dma_tx  = 0;

    /* rs485 properties */
    if (of_property_read_u32_array(np, "rs485-rts-delay",
                        rs485_delay, 2) == 0) {
        struct serial_rs485 *rs485conf = &atmel_port->rs485;

        rs485conf->delay_rts_before_send = rs485_delay[0];
        rs485conf->delay_rts_after_send = rs485_delay[1];
        rs485conf->flags = 0;

        if (of_get_property(np, "rs485-rx-during-tx", NULL))
            rs485conf->flags |= SER_RS485_RX_DURING_TX;

        if (of_get_property(np, "linux,rs485-enabled-at-boot-time", NULL))
            rs485conf->flags |= SER_RS485_ENABLED;
    }
}

/*
 * Configure the port from the platform device resource info.
 */
static void __devinit atmel_init_port(struct atmel_uart_port *atmel_port,
                      struct platform_device *pdev)
{
    struct uart_port *port = &atmel_port->uart;
    struct atmel_uart_data *pdata = pdev->dev.platform_data;

    if (pdev->dev.of_node) {
        atmel_of_init_port(atmel_port, pdev->dev.of_node);
    } else {
        atmel_port->use_dma_rx  = pdata->use_dma_rx;
        atmel_port->use_dma_tx  = pdata->use_dma_tx;
        atmel_port->rs485   = pdata->rs485;
    }

    port->iotype        = UPIO_MEM;
    port->flags     = UPF_BOOT_AUTOCONF;
    port->ops       = &atmel_pops;
    port->fifosize      = 1;
    port->dev       = &pdev->dev;
    port->mapbase   = pdev->resource[0].start;
    port->irq   = pdev->resource[1].start;

    tasklet_init(&atmel_port->tasklet, atmel_tasklet_func,
            (unsigned long)port);

    memset(&atmel_port->rx_ring, 0, sizeof(atmel_port->rx_ring));

    if (pdata && pdata->regs) {
        /* Already mapped by setup code */
        port->membase = pdata->regs;
    } else {
        port->flags |= UPF_IOREMAP;
        port->membase   = NULL;
    }

    /* for console, the clock could already be configured */
    if (!atmel_port->clk) {
        atmel_port->clk = clk_get(&pdev->dev, "usart");
        clk_enable(atmel_port->clk);
        port->uartclk = clk_get_rate(atmel_port->clk);
        clk_disable(atmel_port->clk);
        /* only enable clock when USART is in use */
    }

    /* Use TXEMPTY for interrupt when rs485 else TXRDY or ENDTX|TXBUFE */
    if (atmel_port->rs485.flags & SER_RS485_ENABLED)
        atmel_port->tx_done_mask = ATMEL_US_TXEMPTY;
    else if (atmel_use_dma_tx(port)) {
        port->fifosize = PDC_BUFFER_SIZE;
        atmel_port->tx_done_mask = ATMEL_US_ENDTX | ATMEL_US_TXBUFE;
    } else {
        atmel_port->tx_done_mask = ATMEL_US_TXRDY;
    }
}

/*
 * Register board-specific modem-control line handlers.
 */
void __init atmel_register_uart_fns(struct atmel_port_fns *fns)
{
    if (fns->enable_ms)
        atmel_pops.enable_ms = fns->enable_ms;
    if (fns->get_mctrl)
        atmel_pops.get_mctrl = fns->get_mctrl;
    if (fns->set_mctrl)
        atmel_pops.set_mctrl = fns->set_mctrl;
    atmel_open_hook     = fns->open;
    atmel_close_hook    = fns->close;
    atmel_pops.pm       = fns->pm;
    atmel_pops.set_wake = fns->set_wake;
}

struct platform_device *atmel_default_console_device;   /* the serial console device */

#ifdef CONFIG_SERIAL_ATMEL_CONSOLE
static void atmel_console_putchar(struct uart_port *port, int ch)
{
    while (!(UART_GET_CSR(port) & ATMEL_US_TXRDY))
        cpu_relax();
    UART_PUT_CHAR(port, ch);
}

/*
 * Interrupts are disabled on entering
 */
static void atmel_console_write(struct console *co, const char *s, u_int count)
{
    struct uart_port *port = &atmel_ports[co->index].uart;
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
    unsigned int status, imr;
    unsigned int pdc_tx;

    /*
     * First, save IMR and then disable interrupts
     */
    imr = UART_GET_IMR(port);
    UART_PUT_IDR(port, ATMEL_US_RXRDY | atmel_port->tx_done_mask);

    /* Store PDC transmit status and disable it */
    pdc_tx = UART_GET_PTSR(port) & ATMEL_PDC_TXTEN;
    UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS);

    uart_console_write(port, s, count, atmel_console_putchar);

    /*
     * Finally, wait for transmitter to become empty
     * and restore IMR
     */
    do {
        status = UART_GET_CSR(port);
    } while (!(status & ATMEL_US_TXRDY));

    /* Restore PDC transmit status */
    if (pdc_tx)
        UART_PUT_PTCR(port, ATMEL_PDC_TXTEN);

    /* set interrupts back the way they were */
    UART_PUT_IER(port, imr);
}

/*
 * If the port was already initialised (eg, by a boot loader),
 * try to determine the current setup.
 */
static void __init atmel_console_get_options(struct uart_port *port, int *baud,
                         int *parity, int *bits)
{
    unsigned int mr, quot;

    /*
     * If the baud rate generator isn't running, the port wasn't
     * initialized by the boot loader.
     */
    quot = UART_GET_BRGR(port) & ATMEL_US_CD;
    if (!quot)
        return;

    mr = UART_GET_MR(port) & ATMEL_US_CHRL;
    if (mr == ATMEL_US_CHRL_8)
        *bits = 8;
    else
        *bits = 7;

    mr = UART_GET_MR(port) & ATMEL_US_PAR;
    if (mr == ATMEL_US_PAR_EVEN)
        *parity = 'e';
    else if (mr == ATMEL_US_PAR_ODD)
        *parity = 'o';

    /*
     * The serial core only rounds down when matching this to a
     * supported baud rate. Make sure we don't end up slightly
     * lower than one of those, as it would make us fall through
     * to a much lower baud rate than we really want.
     */
    *baud = port->uartclk / (16 * (quot - 1));
}

static int __init atmel_console_setup(struct console *co, char *options)
{
    struct uart_port *port = &atmel_ports[co->index].uart;
    int baud = 115200;
    int bits = 8;
    int parity = 'n';
    int flow = 'n';

    if (port->membase == NULL) {
        /* Port not initialized yet - delay setup */
        return -ENODEV;
    }

    clk_enable(atmel_ports[co->index].clk);

    UART_PUT_IDR(port, -1);
    UART_PUT_CR(port, ATMEL_US_RSTSTA | ATMEL_US_RSTRX);
    UART_PUT_CR(port, ATMEL_US_TXEN | ATMEL_US_RXEN);

    if (options)
        uart_parse_options(options, &baud, &parity, &bits, &flow);
    else
        atmel_console_get_options(port, &baud, &parity, &bits);

    return uart_set_options(port, co, baud, parity, bits, flow);
}

static struct uart_driver atmel_uart;

static struct console atmel_console = {
    .name       = ATMEL_DEVICENAME,
    .write      = atmel_console_write,
    .device     = uart_console_device,
    .setup      = atmel_console_setup,
    .flags      = CON_PRINTBUFFER,
    .index      = -1,
    .data       = &atmel_uart,
};

#define ATMEL_CONSOLE_DEVICE    (&atmel_console)

/*
 * Early console initialization (before VM subsystem initialized).
 */
static int __init atmel_console_init(void)
{
    if (atmel_default_console_device) {
        struct atmel_uart_data *pdata =
            atmel_default_console_device->dev.platform_data;
        int id = pdata->num;
        struct atmel_uart_port *port = &atmel_ports[id];

        port->backup_imr = 0;
        port->uart.line = id;

        add_preferred_console(ATMEL_DEVICENAME, id, NULL);
        atmel_init_port(port, atmel_default_console_device);
        register_console(&atmel_console);
    }

    return 0;
}

console_initcall(atmel_console_init);

/*
 * Late console initialization.
 */
static int __init atmel_late_console_init(void)
{
    if (atmel_default_console_device
        && !(atmel_console.flags & CON_ENABLED))
        register_console(&atmel_console);

    return 0;
}

core_initcall(atmel_late_console_init);

static inline bool atmel_is_console_port(struct uart_port *port)
{
    return port->cons && port->cons->index == port->line;
}

#else
#define ATMEL_CONSOLE_DEVICE    NULL

static inline bool atmel_is_console_port(struct uart_port *port)
{
    return false;
}
#endif

static struct uart_driver atmel_uart = {
    .owner      = THIS_MODULE,
    .driver_name    = "atmel_serial",
    .dev_name   = ATMEL_DEVICENAME,
    .major      = SERIAL_ATMEL_MAJOR,
    .minor      = MINOR_START,
    .nr     = ATMEL_MAX_UART,
    .cons       = ATMEL_CONSOLE_DEVICE,
};

#ifdef CONFIG_PM
static bool atmel_serial_clk_will_stop(void)
{
#ifdef CONFIG_ARCH_AT91
    return at91_suspend_entering_slow_clock();
#else
    return false;
#endif
}

static int atmel_serial_suspend(struct platform_device *pdev,
                pm_message_t state)
{
    struct uart_port *port = platform_get_drvdata(pdev);
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

    if (atmel_is_console_port(port) && console_suspend_enabled) {
        /* Drain the TX shifter */
        while (!(UART_GET_CSR(port) & ATMEL_US_TXEMPTY))
            cpu_relax();
    }

    /* we can not wake up if we're running on slow clock */
    atmel_port->may_wakeup = device_may_wakeup(&pdev->dev);
    if (atmel_serial_clk_will_stop())
        device_set_wakeup_enable(&pdev->dev, 0);

    uart_suspend_port(&atmel_uart, port);

    return 0;
}

static int atmel_serial_resume(struct platform_device *pdev)
{
    struct uart_port *port = platform_get_drvdata(pdev);
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

    uart_resume_port(&atmel_uart, port);
    device_set_wakeup_enable(&pdev->dev, atmel_port->may_wakeup);

    return 0;
}
#else
#define atmel_serial_suspend NULL
#define atmel_serial_resume NULL
#endif

static int __devinit atmel_serial_probe(struct platform_device *pdev)
{
    struct atmel_uart_port *port;
    struct device_node *np = pdev->dev.of_node;
    struct atmel_uart_data *pdata = pdev->dev.platform_data;
    void *data;
    int ret = -ENODEV;

    BUILD_BUG_ON(ATMEL_SERIAL_RINGSIZE & (ATMEL_SERIAL_RINGSIZE - 1));

    if (np)
        ret = of_alias_get_id(np, "serial");
    else
        if (pdata)
            ret = pdata->num;

    if (ret < 0)
        /* port id not found in platform data nor device-tree aliases:
         * auto-enumerate it */
        ret = find_first_zero_bit(&atmel_ports_in_use,
                sizeof(atmel_ports_in_use));

    if (ret > ATMEL_MAX_UART) {
        ret = -ENODEV;
        goto err;
    }

    if (test_and_set_bit(ret, &atmel_ports_in_use)) {
        /* port already in use */
        ret = -EBUSY;
        goto err;
    }

    port = &atmel_ports[ret];
    port->backup_imr = 0;
    port->uart.line = ret;

    atmel_init_port(port, pdev);

    if (!atmel_use_dma_rx(&port->uart)) {
        ret = -ENOMEM;
        data = kmalloc(sizeof(struct atmel_uart_char)
                * ATMEL_SERIAL_RINGSIZE, GFP_KERNEL);
        if (!data)
            goto err_alloc_ring;
        port->rx_ring.buf = data;
    }

    ret = uart_add_one_port(&atmel_uart, &port->uart);
    if (ret)
        goto err_add_port;

#ifdef CONFIG_SERIAL_ATMEL_CONSOLE
    if (atmel_is_console_port(&port->uart)
            && ATMEL_CONSOLE_DEVICE->flags & CON_ENABLED) {
        /*
         * The serial core enabled the clock for us, so undo
         * the clk_enable() in atmel_console_setup()
         */
        clk_disable(port->clk);
    }
#endif

    device_init_wakeup(&pdev->dev, 1);
    platform_set_drvdata(pdev, port);

    if (port->rs485.flags & SER_RS485_ENABLED) {
        UART_PUT_MR(&port->uart, ATMEL_US_USMODE_NORMAL);
        UART_PUT_CR(&port->uart, ATMEL_US_RTSEN);
    }

    return 0;

err_add_port:
    kfree(port->rx_ring.buf);
    port->rx_ring.buf = NULL;
err_alloc_ring:
    if (!atmel_is_console_port(&port->uart)) {
        clk_put(port->clk);
        port->clk = NULL;
    }
err:
    return ret;
}

static int __devexit atmel_serial_remove(struct platform_device *pdev)
{
    struct uart_port *port = platform_get_drvdata(pdev);
    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
    int ret = 0;

    device_init_wakeup(&pdev->dev, 0);
    platform_set_drvdata(pdev, NULL);

    ret = uart_remove_one_port(&atmel_uart, port);

    tasklet_kill(&atmel_port->tasklet);
    kfree(atmel_port->rx_ring.buf);

    /* "port" is allocated statically, so we shouldn't free it */

    clear_bit(port->line, &atmel_ports_in_use);

    clk_put(atmel_port->clk);

    return ret;
}

static struct platform_driver atmel_serial_driver = {
    .probe      = atmel_serial_probe,
    .remove     = __devexit_p(atmel_serial_remove),
    .suspend    = atmel_serial_suspend,
    .resume     = atmel_serial_resume,
    .driver     = {
        .name   = "atmel_usart",
        .owner  = THIS_MODULE,
        .of_match_table = of_match_ptr(atmel_serial_dt_ids),
    },
};

static int __init atmel_serial_init(void)
{
    int ret;

    ret = uart_register_driver(&atmel_uart);
    if (ret)
        return ret;

    ret = platform_driver_register(&atmel_serial_driver);
    if (ret)
        uart_unregister_driver(&atmel_uart);

    return ret;
}

static void __exit atmel_serial_exit(void)
{
    platform_driver_unregister(&atmel_serial_driver);
    uart_unregister_driver(&atmel_uart);
}

module_init(atmel_serial_init);
module_exit(atmel_serial_exit);

MODULE_AUTHOR("Rick Bronson");
MODULE_DESCRIPTION("Atmel AT91 / AT32 serial port driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:atmel_usart");