drivers/tty/serial/atmel_serial.c

// SPDX-License-Identifier: GPL-2.0+
/*
 *  Driver for Atmel AT91 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.
 */
#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/of_gpio.h>
#include <linux/dma-mapping.h>
#include <linux/dmaengine.h>
#include <linux/atmel_pdc.h>
#include <linux/uaccess.h>
#include <linux/platform_data/atmel.h>
#include <linux/timer.h>
#include <linux/gpio.h>
#include <linux/gpio/consumer.h>
#include <linux/err.h>
#include <linux/irq.h>
#include <linux/suspend.h>
#include <linux/mm.h>

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

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

/* The minium number of data FIFOs should be able to contain */
#define ATMEL_MIN_FIFO_SIZE	8
/*
 * These two offsets are substracted from the RX FIFO size to define the RTS
 * high and low thresholds
 */
#define ATMEL_RTS_HIGH_OFFSET	16
#define ATMEL_RTS_LOW_OFFSET	20

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

#include <linux/serial_core.h>

#include "serial_mctrl_gpio.h"
#include "atmel_serial.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

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;
};

/*
 * Be careful, the real size of the ring buffer is
 * sizeof(atmel_uart_char) * ATMEL_SERIAL_RINGSIZE. It means that ring buffer
 * can contain up to 1024 characters in PIO mode and up to 4096 characters in
 * DMA mode.
 */
#define ATMEL_SERIAL_RINGSIZE 1024

/*
 * at91: 6 USARTs and one DBGU port (SAM9260)
 * samx7: 3 USARTs and 5 UARTs
 */
#define ATMEL_MAX_UART		8

/*
 * 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 */

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

	bool			use_dma_tx;     /* enable DMA transmitter */
	bool			use_pdc_tx;	/* enable PDC transmitter */
	struct atmel_dma_buffer	pdc_tx;		/* PDC transmitter */

	spinlock_t			lock_tx;	/* port lock */
	spinlock_t			lock_rx;	/* port lock */
	struct dma_chan			*chan_tx;
	struct dma_chan			*chan_rx;
	struct dma_async_tx_descriptor	*desc_tx;
	struct dma_async_tx_descriptor	*desc_rx;
	dma_cookie_t			cookie_tx;
	dma_cookie_t			cookie_rx;
	struct scatterlist		sg_tx;
	struct scatterlist		sg_rx;
	struct tasklet_struct	tasklet_rx;
	struct tasklet_struct	tasklet_tx;
	atomic_t		tasklet_shutdown;
	unsigned int		irq_status_prev;
	unsigned int		tx_len;

	struct circ_buf		rx_ring;

	struct mctrl_gpios	*gpios;
	unsigned int		tx_done_mask;
	u32			fifo_size;
	u32			rts_high;
	u32			rts_low;
	bool			ms_irq_enabled;
	u32			rtor;	/* address of receiver timeout register if it exists */
	bool			has_frac_baudrate;
	bool			has_hw_timer;
	struct timer_list	uart_timer;

	bool			tx_stopped;
	bool			suspended;
	unsigned int		pending;
	unsigned int		pending_status;
	spinlock_t		lock_suspended;

#ifdef CONFIG_PM
	struct {
		u32		cr;
		u32		mr;
		u32		imr;
		u32		brgr;
		u32		rtor;
		u32		ttgr;
		u32		fmr;
		u32		fimr;
	} cache;
#endif

	int (*prepare_rx)(struct uart_port *port);
	int (*prepare_tx)(struct uart_port *port);
	void (*schedule_rx)(struct uart_port *port);
	void (*schedule_tx)(struct uart_port *port);
	void (*release_rx)(struct uart_port *port);
	void (*release_tx)(struct uart_port *port);
};

static struct atmel_uart_port atmel_ports[ATMEL_MAX_UART];
static DECLARE_BITMAP(atmel_ports_in_use, ATMEL_MAX_UART);

#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 */ }
};
#endif

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

static inline u32 atmel_uart_readl(struct uart_port *port, u32 reg)
{
	return __raw_readl(port->membase + reg);
}

static inline void atmel_uart_writel(struct uart_port *port, u32 reg, u32 value)
{
	__raw_writel(value, port->membase + reg);
}

static inline u8 atmel_uart_read_char(struct uart_port *port)
{
	return __raw_readb(port->membase + ATMEL_US_RHR);
}

static inline void atmel_uart_write_char(struct uart_port *port, u8 value)
{
	__raw_writeb(value, port->membase + ATMEL_US_THR);
}

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

	return atmel_port->use_pdc_rx;
}

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

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

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

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;
}

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_fifo(struct uart_port *port)
{
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

	return atmel_port->fifo_size;
}

static void atmel_tasklet_schedule(struct atmel_uart_port *atmel_port,
				   struct tasklet_struct *t)
{
	if (!atomic_read(&atmel_port->tasklet_shutdown))
		tasklet_schedule(t);
}

static unsigned int atmel_get_lines_status(struct uart_port *port)
{
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
	unsigned int status, ret = 0;

	status = atmel_uart_readl(port, ATMEL_US_CSR);

	mctrl_gpio_get(atmel_port->gpios, &ret);

	if (!IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(atmel_port->gpios,
						UART_GPIO_CTS))) {
		if (ret & TIOCM_CTS)
			status &= ~ATMEL_US_CTS;
		else
			status |= ATMEL_US_CTS;
	}

	if (!IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(atmel_port->gpios,
						UART_GPIO_DSR))) {
		if (ret & TIOCM_DSR)
			status &= ~ATMEL_US_DSR;
		else
			status |= ATMEL_US_DSR;
	}

	if (!IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(atmel_port->gpios,
						UART_GPIO_RI))) {
		if (ret & TIOCM_RI)
			status &= ~ATMEL_US_RI;
		else
			status |= ATMEL_US_RI;
	}

	if (!IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(atmel_port->gpios,
						UART_GPIO_DCD))) {
		if (ret & TIOCM_CD)
			status &= ~ATMEL_US_DCD;
		else
			status |= ATMEL_US_DCD;
	}

	return status;
}

/* Enable or disable the rs485 support */
static int 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;

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

	mode = atmel_uart_readl(port, ATMEL_US_MR);

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

	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;
		atmel_uart_writel(port, ATMEL_US_TTGR,
				  rs485conf->delay_rts_after_send);
		mode |= ATMEL_US_USMODE_RS485;
	} else {
		dev_dbg(port->dev, "Setting UART to RS232\n");
		if (atmel_use_pdc_tx(port))
			atmel_port->tx_done_mask = ATMEL_US_ENDTX |
				ATMEL_US_TXBUFE;
		else
			atmel_port->tx_done_mask = ATMEL_US_TXRDY;
	}
	atmel_uart_writel(port, ATMEL_US_MR, mode);

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

	return 0;
}

/*
 * Return TIOCSER_TEMT when transmitter FIFO and Shift register is empty.
 */
static u_int atmel_tx_empty(struct uart_port *port)
{
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

	if (atmel_port->tx_stopped)
		return TIOCSER_TEMT;
	return (atmel_uart_readl(port, ATMEL_US_CSR) & 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 = atmel_uart_readl(port, ATMEL_US_MR);
	unsigned int rts_paused, rts_ready;
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

	/* override mode to RS485 if needed, otherwise keep the current mode */
	if (port->rs485.flags & SER_RS485_ENABLED) {
		atmel_uart_writel(port, ATMEL_US_TTGR,
				  port->rs485.delay_rts_after_send);
		mode &= ~ATMEL_US_USMODE;
		mode |= ATMEL_US_USMODE_RS485;
	}

	/* set the RTS line state according to the mode */
	if ((mode & ATMEL_US_USMODE) == ATMEL_US_USMODE_HWHS) {
		/* force RTS line to high level */
		rts_paused = ATMEL_US_RTSEN;

		/* give the control of the RTS line back to the hardware */
		rts_ready = ATMEL_US_RTSDIS;
	} else {
		/* force RTS line to high level */
		rts_paused = ATMEL_US_RTSDIS;

		/* force RTS line to low level */
		rts_ready = ATMEL_US_RTSEN;
	}

	if (mctrl & TIOCM_RTS)
		control |= rts_ready;
	else
		control |= rts_paused;

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

	atmel_uart_writel(port, ATMEL_US_CR, control);

	mctrl_gpio_set(atmel_port->gpios, mctrl);

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

	atmel_uart_writel(port, ATMEL_US_MR, mode);
}

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

	status = atmel_uart_readl(port, ATMEL_US_CSR);

	/*
	 * 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 mctrl_gpio_get(atmel_port->gpios, &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_pdc_tx(port)) {
		/* disable PDC transmit */
		atmel_uart_writel(port, ATMEL_PDC_PTCR, ATMEL_PDC_TXTDIS);
	}

	/*
	 * Disable the transmitter.
	 * This is mandatory when DMA is used, otherwise the DMA buffer
	 * is fully transmitted.
	 */
	atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXDIS);
	atmel_port->tx_stopped = true;

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

	if ((port->rs485.flags & SER_RS485_ENABLED) &&
	    !(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_pdc_tx(port) && (atmel_uart_readl(port, ATMEL_PDC_PTSR)
				       & ATMEL_PDC_TXTEN))
		/* The transmitter is already running.  Yes, we
		   really need this.*/
		return;

	if (atmel_use_pdc_tx(port) || atmel_use_dma_tx(port))
		if ((port->rs485.flags & SER_RS485_ENABLED) &&
		    !(port->rs485.flags & SER_RS485_RX_DURING_TX))
			atmel_stop_rx(port);

	if (atmel_use_pdc_tx(port))
		/* re-enable PDC transmit */
		atmel_uart_writel(port, ATMEL_PDC_PTCR, ATMEL_PDC_TXTEN);

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

	/* re-enable the transmitter */
	atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN);
	atmel_port->tx_stopped = false;
}

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

	atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_RXEN);

	if (atmel_use_pdc_rx(port)) {
		/* enable PDC controller */
		atmel_uart_writel(port, ATMEL_US_IER,
				  ATMEL_US_ENDRX | ATMEL_US_TIMEOUT |
				  port->read_status_mask);
		atmel_uart_writel(port, ATMEL_PDC_PTCR, ATMEL_PDC_RXTEN);
	} else {
		atmel_uart_writel(port, ATMEL_US_IER, ATMEL_US_RXRDY);
	}
}

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

	if (atmel_use_pdc_rx(port)) {
		/* disable PDC receive */
		atmel_uart_writel(port, ATMEL_PDC_PTCR, ATMEL_PDC_RXTDIS);
		atmel_uart_writel(port, ATMEL_US_IDR,
				  ATMEL_US_ENDRX | ATMEL_US_TIMEOUT |
				  port->read_status_mask);
	} else {
		atmel_uart_writel(port, ATMEL_US_IDR, ATMEL_US_RXRDY);
	}
}

/*
 * Enable modem status interrupts
 */
static void atmel_enable_ms(struct uart_port *port)
{
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
	uint32_t ier = 0;

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

	atmel_port->ms_irq_enabled = true;

	if (!mctrl_gpio_to_gpiod(atmel_port->gpios, UART_GPIO_CTS))
		ier |= ATMEL_US_CTSIC;

	if (!mctrl_gpio_to_gpiod(atmel_port->gpios, UART_GPIO_DSR))
		ier |= ATMEL_US_DSRIC;

	if (!mctrl_gpio_to_gpiod(atmel_port->gpios, UART_GPIO_RI))
		ier |= ATMEL_US_RIIC;

	if (!mctrl_gpio_to_gpiod(atmel_port->gpios, UART_GPIO_DCD))
		ier |= ATMEL_US_DCDIC;

	atmel_uart_writel(port, ATMEL_US_IER, ier);

	mctrl_gpio_enable_ms(atmel_port->gpios);
}

/*
 * Disable modem status interrupts
 */
static void atmel_disable_ms(struct uart_port *port)
{
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
	uint32_t idr = 0;

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

	atmel_port->ms_irq_enabled = false;

	mctrl_gpio_disable_ms(atmel_port->gpios);

	if (!mctrl_gpio_to_gpiod(atmel_port->gpios, UART_GPIO_CTS))
		idr |= ATMEL_US_CTSIC;

	if (!mctrl_gpio_to_gpiod(atmel_port->gpios, UART_GPIO_DSR))
		idr |= ATMEL_US_DSRIC;

	if (!mctrl_gpio_to_gpiod(atmel_port->gpios, UART_GPIO_RI))
		idr |= ATMEL_US_RIIC;

	if (!mctrl_gpio_to_gpiod(atmel_port->gpios, UART_GPIO_DCD))
		idr |= ATMEL_US_DCDIC;

	atmel_uart_writel(port, ATMEL_US_IDR, idr);
}

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

/*
 * 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 */
	atmel_uart_writel(port, ATMEL_US_CR, 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 = atmel_uart_readl(port, ATMEL_US_CSR);
	while (status & ATMEL_US_RXRDY) {
		ch = atmel_uart_read_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 */
			atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_RSTSTA);

			if (status & ATMEL_US_RXBRK
			    && !atmel_port->break_active) {
				atmel_port->break_active = 1;
				atmel_uart_writel(port, ATMEL_US_IER,
						  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.
				 */
				atmel_uart_writel(port, ATMEL_US_IDR,
						  ATMEL_US_RXBRK);
				status &= ~ATMEL_US_RXBRK;
				atmel_port->break_active = 0;
			}
		}

		atmel_buffer_rx_char(port, status, ch);
		status = atmel_uart_readl(port, ATMEL_US_CSR);
	}

	atmel_tasklet_schedule(atmel_port, &atmel_port->tasklet_rx);
}

/*
 * 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 &&
	    (atmel_uart_readl(port, ATMEL_US_CSR) & atmel_port->tx_done_mask)) {
		atmel_uart_write_char(port, port->x_char);
		port->icount.tx++;
		port->x_char = 0;
	}
	if (uart_circ_empty(xmit) || uart_tx_stopped(port))
		return;

	while (atmel_uart_readl(port, ATMEL_US_CSR) &
	       atmel_port->tx_done_mask) {
		atmel_uart_write_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 */
		atmel_uart_writel(port, ATMEL_US_IER,
				  atmel_port->tx_done_mask);
}

static void atmel_complete_tx_dma(void *arg)
{
	struct atmel_uart_port *atmel_port = arg;
	struct uart_port *port = &atmel_port->uart;
	struct circ_buf *xmit = &port->state->xmit;
	struct dma_chan *chan = atmel_port->chan_tx;
	unsigned long flags;

	spin_lock_irqsave(&port->lock, flags);

	if (chan)
		dmaengine_terminate_all(chan);
	xmit->tail += atmel_port->tx_len;
	xmit->tail &= UART_XMIT_SIZE - 1;

	port->icount.tx += atmel_port->tx_len;

	spin_lock_irq(&atmel_port->lock_tx);
	async_tx_ack(atmel_port->desc_tx);
	atmel_port->cookie_tx = -EINVAL;
	atmel_port->desc_tx = NULL;
	spin_unlock_irq(&atmel_port->lock_tx);

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

	/*
	 * xmit is a circular buffer so, if we have just send data from
	 * xmit->tail to the end of xmit->buf, now we have to transmit the
	 * remaining data from the beginning of xmit->buf to xmit->head.
	 */
	if (!uart_circ_empty(xmit))
		atmel_tasklet_schedule(atmel_port, &atmel_port->tasklet_tx);
	else if ((port->rs485.flags & SER_RS485_ENABLED) &&
		 !(port->rs485.flags & SER_RS485_RX_DURING_TX)) {
		/* DMA done, stop TX, start RX for RS485 */
		atmel_start_rx(port);
	}

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

static void atmel_release_tx_dma(struct uart_port *port)
{
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
	struct dma_chan *chan = atmel_port->chan_tx;

	if (chan) {
		dmaengine_terminate_all(chan);
		dma_release_channel(chan);
		dma_unmap_sg(port->dev, &atmel_port->sg_tx, 1,
				DMA_TO_DEVICE);
	}

	atmel_port->desc_tx = NULL;
	atmel_port->chan_tx = NULL;
	atmel_port->cookie_tx = -EINVAL;
}

/*
 * Called from tasklet with TXRDY interrupt is 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 dma_chan *chan = atmel_port->chan_tx;
	struct dma_async_tx_descriptor *desc;
	struct scatterlist sgl[2], *sg, *sg_tx = &atmel_port->sg_tx;
	unsigned int tx_len, part1_len, part2_len, sg_len;
	dma_addr_t phys_addr;

	/* Make sure we have an idle channel */
	if (atmel_port->desc_tx != NULL)
		return;

	if (!uart_circ_empty(xmit) && !uart_tx_stopped(port)) {
		/*
		 * DMA is idle now.
		 * Port xmit buffer is already mapped,
		 * and it is one page... Just adjust
		 * offsets and lengths. Since it is a circular buffer,
		 * we have to transmit till the end, and then the rest.
		 * Take the port lock to get a
		 * consistent xmit buffer state.
		 */
		tx_len = CIRC_CNT_TO_END(xmit->head,
					 xmit->tail,
					 UART_XMIT_SIZE);

		if (atmel_port->fifo_size) {
			/* multi data mode */
			part1_len = (tx_len & ~0x3); /* DWORD access */
			part2_len = (tx_len & 0x3); /* BYTE access */
		} else {
			/* single data (legacy) mode */
			part1_len = 0;
			part2_len = tx_len; /* BYTE access only */
		}

		sg_init_table(sgl, 2);
		sg_len = 0;
		phys_addr = sg_dma_address(sg_tx) + xmit->tail;
		if (part1_len) {
			sg = &sgl[sg_len++];
			sg_dma_address(sg) = phys_addr;
			sg_dma_len(sg) = part1_len;

			phys_addr += part1_len;
		}

		if (part2_len) {
			sg = &sgl[sg_len++];
			sg_dma_address(sg) = phys_addr;
			sg_dma_len(sg) = part2_len;
		}

		/*
		 * save tx_len so atmel_complete_tx_dma() will increase
		 * xmit->tail correctly
		 */
		atmel_port->tx_len = tx_len;

		desc = dmaengine_prep_slave_sg(chan,
					       sgl,
					       sg_len,
					       DMA_MEM_TO_DEV,
					       DMA_PREP_INTERRUPT |
					       DMA_CTRL_ACK);
		if (!desc) {
			dev_err(port->dev, "Failed to send via dma!\n");
			return;
		}

		dma_sync_sg_for_device(port->dev, sg_tx, 1, DMA_TO_DEVICE);

		atmel_port->desc_tx = desc;
		desc->callback = atmel_complete_tx_dma;
		desc->callback_param = atmel_port;
		atmel_port->cookie_tx = dmaengine_submit(desc);
	}

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

static int atmel_prepare_tx_dma(struct uart_port *port)
{
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
	dma_cap_mask_t		mask;
	struct dma_slave_config config;
	int ret, nent;

	dma_cap_zero(mask);
	dma_cap_set(DMA_SLAVE, mask);

	atmel_port->chan_tx = dma_request_slave_channel(port->dev, "tx");
	if (atmel_port->chan_tx == NULL)
		goto chan_err;
	dev_info(port->dev, "using %s for tx DMA transfers\n",
		dma_chan_name(atmel_port->chan_tx));

	spin_lock_init(&atmel_port->lock_tx);
	sg_init_table(&atmel_port->sg_tx, 1);
	/* UART circular tx buffer is an aligned page. */
	BUG_ON(!PAGE_ALIGNED(port->state->xmit.buf));
	sg_set_page(&atmel_port->sg_tx,
			virt_to_page(port->state->xmit.buf),
			UART_XMIT_SIZE,
			offset_in_page(port->state->xmit.buf));
	nent = dma_map_sg(port->dev,
				&atmel_port->sg_tx,
				1,
				DMA_TO_DEVICE);

	if (!nent) {
		dev_dbg(port->dev, "need to release resource of dma\n");
		goto chan_err;
	} else {
		dev_dbg(port->dev, "%s: mapped %d@%p to %pad\n", __func__,
			sg_dma_len(&atmel_port->sg_tx),
			port->state->xmit.buf,
			&sg_dma_address(&atmel_port->sg_tx));
	}

	/* Configure the slave DMA */
	memset(&config, 0, sizeof(config));
	config.direction = DMA_MEM_TO_DEV;
	config.dst_addr_width = (atmel_port->fifo_size) ?
				DMA_SLAVE_BUSWIDTH_4_BYTES :
				DMA_SLAVE_BUSWIDTH_1_BYTE;
	config.dst_addr = port->mapbase + ATMEL_US_THR;
	config.dst_maxburst = 1;

	ret = dmaengine_slave_config(atmel_port->chan_tx,
				     &config);
	if (ret) {
		dev_err(port->dev, "DMA tx slave configuration failed\n");
		goto chan_err;
	}

	return 0;

chan_err:
	dev_err(port->dev, "TX channel not available, switch to pio\n");
	atmel_port->use_dma_tx = 0;
	if (atmel_port->chan_tx)
		atmel_release_tx_dma(port);
	return -EINVAL;
}

static void atmel_complete_rx_dma(void *arg)
{
	struct uart_port *port = arg;
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

	atmel_tasklet_schedule(atmel_port, &atmel_port->tasklet_rx);
}

static void atmel_release_rx_dma(struct uart_port *port)
{
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
	struct dma_chan *chan = atmel_port->chan_rx;

	if (chan) {
		dmaengine_terminate_all(chan);
		dma_release_channel(chan);
		dma_unmap_sg(port->dev, &atmel_port->sg_rx, 1,
				DMA_FROM_DEVICE);
	}

	atmel_port->desc_rx = NULL;
	atmel_port->chan_rx = NULL;
	atmel_port->cookie_rx = -EINVAL;
}

static void atmel_rx_from_dma(struct uart_port *port)
{
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
	struct tty_port *tport = &port->state->port;
	struct circ_buf *ring = &atmel_port->rx_ring;
	struct dma_chan *chan = atmel_port->chan_rx;
	struct dma_tx_state state;
	enum dma_status dmastat;
	size_t count;


	/* Reset the UART timeout early so that we don't miss one */
	atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_STTTO);
	dmastat = dmaengine_tx_status(chan,
				atmel_port->cookie_rx,
				&state);
	/* Restart a new tasklet if DMA status is error */
	if (dmastat == DMA_ERROR) {
		dev_dbg(port->dev, "Get residue error, restart tasklet\n");
		atmel_uart_writel(port, ATMEL_US_IER, ATMEL_US_TIMEOUT);
		atmel_tasklet_schedule(atmel_port, &atmel_port->tasklet_rx);
		return;
	}

	/* CPU claims ownership of RX DMA buffer */
	dma_sync_sg_for_cpu(port->dev,
			    &atmel_port->sg_rx,
			    1,
			    DMA_FROM_DEVICE);

	/*
	 * ring->head points to the end of data already written by the DMA.
	 * ring->tail points to the beginning of data to be read by the
	 * framework.
	 * The current transfer size should not be larger than the dma buffer
	 * length.
	 */
	ring->head = sg_dma_len(&atmel_port->sg_rx) - state.residue;
	BUG_ON(ring->head > sg_dma_len(&atmel_port->sg_rx));
	/*
	 * At this point ring->head may point to the first byte right after the
	 * last byte of the dma buffer:
	 * 0 <= ring->head <= sg_dma_len(&atmel_port->sg_rx)
	 *
	 * However ring->tail must always points inside the dma buffer:
	 * 0 <= ring->tail <= sg_dma_len(&atmel_port->sg_rx) - 1
	 *
	 * Since we use a ring buffer, we have to handle the case
	 * where head is lower than tail. In such a case, we first read from
	 * tail to the end of the buffer then reset tail.
	 */
	if (ring->head < ring->tail) {
		count = sg_dma_len(&atmel_port->sg_rx) - ring->tail;

		tty_insert_flip_string(tport, ring->buf + ring->tail, count);
		ring->tail = 0;
		port->icount.rx += count;
	}

	/* Finally we read data from tail to head */
	if (ring->tail < ring->head) {
		count = ring->head - ring->tail;

		tty_insert_flip_string(tport, ring->buf + ring->tail, count);
		/* Wrap ring->head if needed */
		if (ring->head >= sg_dma_len(&atmel_port->sg_rx))
			ring->head = 0;
		ring->tail = ring->head;
		port->icount.rx += count;
	}

	/* USART retreives ownership of RX DMA buffer */
	dma_sync_sg_for_device(port->dev,
			       &atmel_port->sg_rx,
			       1,
			       DMA_FROM_DEVICE);

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

	atmel_uart_writel(port, ATMEL_US_IER, ATMEL_US_TIMEOUT);
}

static int atmel_prepare_rx_dma(struct uart_port *port)
{
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
	struct dma_async_tx_descriptor *desc;
	dma_cap_mask_t		mask;
	struct dma_slave_config config;
	struct circ_buf		*ring;
	int ret, nent;

	ring = &atmel_port->rx_ring;

	dma_cap_zero(mask);
	dma_cap_set(DMA_CYCLIC, mask);

	atmel_port->chan_rx = dma_request_slave_channel(port->dev, "rx");
	if (atmel_port->chan_rx == NULL)
		goto chan_err;
	dev_info(port->dev, "using %s for rx DMA transfers\n",
		dma_chan_name(atmel_port->chan_rx));

	spin_lock_init(&atmel_port->lock_rx);
	sg_init_table(&atmel_port->sg_rx, 1);
	/* UART circular rx buffer is an aligned page. */
	BUG_ON(!PAGE_ALIGNED(ring->buf));
	sg_set_page(&atmel_port->sg_rx,
		    virt_to_page(ring->buf),
		    sizeof(struct atmel_uart_char) * ATMEL_SERIAL_RINGSIZE,
		    offset_in_page(ring->buf));
	nent = dma_map_sg(port->dev,
			  &atmel_port->sg_rx,
			  1,
			  DMA_FROM_DEVICE);

	if (!nent) {
		dev_dbg(port->dev, "need to release resource of dma\n");
		goto chan_err;
	} else {
		dev_dbg(port->dev, "%s: mapped %d@%p to %pad\n", __func__,
			sg_dma_len(&atmel_port->sg_rx),
			ring->buf,
			&sg_dma_address(&atmel_port->sg_rx));
	}

	/* Configure the slave DMA */
	memset(&config, 0, sizeof(config));
	config.direction = DMA_DEV_TO_MEM;
	config.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
	config.src_addr = port->mapbase + ATMEL_US_RHR;
	config.src_maxburst = 1;

	ret = dmaengine_slave_config(atmel_port->chan_rx,
				     &config);
	if (ret) {
		dev_err(port->dev, "DMA rx slave configuration failed\n");
		goto chan_err;
	}
	/*
	 * Prepare a cyclic dma transfer, assign 2 descriptors,
	 * each one is half ring buffer size
	 */
	desc = dmaengine_prep_dma_cyclic(atmel_port->chan_rx,
					 sg_dma_address(&atmel_port->sg_rx),
					 sg_dma_len(&atmel_port->sg_rx),
					 sg_dma_len(&atmel_port->sg_rx)/2,
					 DMA_DEV_TO_MEM,
					 DMA_PREP_INTERRUPT);
	desc->callback = atmel_complete_rx_dma;
	desc->callback_param = port;
	atmel_port->desc_rx = desc;
	atmel_port->cookie_rx = dmaengine_submit(desc);

	return 0;

chan_err:
	dev_err(port->dev, "RX channel not available, switch to pio\n");
	atmel_port->use_dma_rx = 0;
	if (atmel_port->chan_rx)
		atmel_release_rx_dma(port);
	return -EINVAL;
}

static void atmel_uart_timer_callback(struct timer_list *t)
{
	struct atmel_uart_port *atmel_port = from_timer(atmel_port, t,
							uart_timer);
	struct uart_port *port = &atmel_port->uart;

	if (!atomic_read(&atmel_port->tasklet_shutdown)) {
		tasklet_schedule(&atmel_port->tasklet_rx);
		mod_timer(&atmel_port->uart_timer,
			  jiffies + uart_poll_timeout(port));
	}
}

/*
 * 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_pdc_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)) {
			atmel_uart_writel(port, ATMEL_US_IDR,
					  (ATMEL_US_ENDRX | ATMEL_US_TIMEOUT));
			atmel_tasklet_schedule(atmel_port,
					       &atmel_port->tasklet_rx);
		}

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

	if (atmel_use_dma_rx(port)) {
		if (pending & ATMEL_US_TIMEOUT) {
			atmel_uart_writel(port, ATMEL_US_IDR,
					  ATMEL_US_TIMEOUT);
			atmel_tasklet_schedule(atmel_port,
					       &atmel_port->tasklet_rx);
		}
	}

	/* 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.
		 */
		atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_RSTSTA);
		atmel_uart_writel(port, ATMEL_US_IDR, 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 */
		atmel_uart_writel(port, ATMEL_US_IDR,
				  atmel_port->tx_done_mask);
		atmel_tasklet_schedule(atmel_port, &atmel_port->tasklet_tx);
	}
}

/*
 * 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);
	unsigned int status_change;

	if (pending & (ATMEL_US_RIIC | ATMEL_US_DSRIC | ATMEL_US_DCDIC
				| ATMEL_US_CTSIC)) {
		status_change = status ^ atmel_port->irq_status_prev;
		atmel_port->irq_status_prev = status;

		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);
		}
	}
}

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

	spin_lock(&atmel_port->lock_suspended);

	do {
		status = atmel_get_lines_status(port);
		mask = atmel_uart_readl(port, ATMEL_US_IMR);
		pending = status & mask;
		if (!pending)
			break;

		if (atmel_port->suspended) {
			atmel_port->pending |= pending;
			atmel_port->pending_status = status;
			atmel_uart_writel(port, ATMEL_US_IDR, mask);
			pm_system_wakeup();
			break;
		}

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

	spin_unlock(&atmel_port->lock_suspended);

	return pass_counter ? IRQ_HANDLED : IRQ_NONE;
}

static void atmel_release_tx_pdc(struct uart_port *port)
{
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
	struct atmel_dma_buffer *pdc = &atmel_port->pdc_tx;

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

/*
 * Called from tasklet with ENDTX and TXBUFE interrupts disabled.
 */
static void atmel_tx_pdc(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 (atmel_uart_readl(port, ATMEL_PDC_TCR))
		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 */
	atmel_uart_writel(port, ATMEL_PDC_PTCR, 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;

		atmel_uart_writel(port, ATMEL_PDC_TPR,
				  pdc->dma_addr + xmit->tail);
		atmel_uart_writel(port, ATMEL_PDC_TCR, count);
		/* re-enable PDC transmit */
		atmel_uart_writel(port, ATMEL_PDC_PTCR, ATMEL_PDC_TXTEN);
		/* Enable interrupts */
		atmel_uart_writel(port, ATMEL_US_IER,
				  atmel_port->tx_done_mask);
	} else {
		if ((port->rs485.flags & SER_RS485_ENABLED) &&
		    !(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 int atmel_prepare_tx_pdc(struct uart_port *port)
{
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(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;

	return 0;
}

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);
	spin_lock(&port->lock);
}

static void atmel_release_rx_pdc(struct uart_port *port)
{
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(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);
	}
}

static void atmel_rx_from_pdc(struct uart_port *port)
{
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
	struct tty_port *tport = &port->state->port;
	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 */
		atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_STTTO);

		pdc = &atmel_port->pdc_rx[rx_idx];
		head = atmel_uart_readl(port, ATMEL_PDC_RPR) - 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(tport, 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;
			atmel_uart_writel(port, ATMEL_PDC_RNPR, pdc->dma_addr);
			atmel_uart_writel(port, ATMEL_PDC_RNCR, 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(tport);
	spin_lock(&port->lock);

	atmel_uart_writel(port, ATMEL_US_IER,
			  ATMEL_US_ENDRX | ATMEL_US_TIMEOUT);
}

static int atmel_prepare_rx_pdc(struct uart_port *port)
{
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(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);
			}
			atmel_port->use_pdc_rx = 0;
			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;

	atmel_uart_writel(port, ATMEL_PDC_RPR, atmel_port->pdc_rx[0].dma_addr);
	atmel_uart_writel(port, ATMEL_PDC_RCR, PDC_BUFFER_SIZE);

	atmel_uart_writel(port, ATMEL_PDC_RNPR,
			  atmel_port->pdc_rx[1].dma_addr);
	atmel_uart_writel(port, ATMEL_PDC_RNCR, PDC_BUFFER_SIZE);

	return 0;
}

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

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

static void atmel_tasklet_tx_func(unsigned long data)
{
	struct uart_port *port = (struct uart_port *)data;
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

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

static void atmel_init_property(struct atmel_uart_port *atmel_port,
				struct platform_device *pdev)
{
	struct device_node *np = pdev->dev.of_node;

	/* DMA/PDC usage specification */
	if (of_property_read_bool(np, "atmel,use-dma-rx")) {
		if (of_property_read_bool(np, "dmas")) {
			atmel_port->use_dma_rx  = true;
			atmel_port->use_pdc_rx  = false;
		} else {
			atmel_port->use_dma_rx  = false;
			atmel_port->use_pdc_rx  = true;
		}
	} else {
		atmel_port->use_dma_rx  = false;
		atmel_port->use_pdc_rx  = false;
	}

	if (of_property_read_bool(np, "atmel,use-dma-tx")) {
		if (of_property_read_bool(np, "dmas")) {
			atmel_port->use_dma_tx  = true;
			atmel_port->use_pdc_tx  = false;
		} else {
			atmel_port->use_dma_tx  = false;
			atmel_port->use_pdc_tx  = true;
		}
	} else {
		atmel_port->use_dma_tx  = false;
		atmel_port->use_pdc_tx  = false;
	}
}

static void atmel_set_ops(struct uart_port *port)
{
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

	if (atmel_use_dma_rx(port)) {
		atmel_port->prepare_rx = &atmel_prepare_rx_dma;
		atmel_port->schedule_rx = &atmel_rx_from_dma;
		atmel_port->release_rx = &atmel_release_rx_dma;
	} else if (atmel_use_pdc_rx(port)) {
		atmel_port->prepare_rx = &atmel_prepare_rx_pdc;
		atmel_port->schedule_rx = &atmel_rx_from_pdc;
		atmel_port->release_rx = &atmel_release_rx_pdc;
	} else {
		atmel_port->prepare_rx = NULL;
		atmel_port->schedule_rx = &atmel_rx_from_ring;
		atmel_port->release_rx = NULL;
	}

	if (atmel_use_dma_tx(port)) {
		atmel_port->prepare_tx = &atmel_prepare_tx_dma;
		atmel_port->schedule_tx = &atmel_tx_dma;
		atmel_port->release_tx = &atmel_release_tx_dma;
	} else if (atmel_use_pdc_tx(port)) {
		atmel_port->prepare_tx = &atmel_prepare_tx_pdc;
		atmel_port->schedule_tx = &atmel_tx_pdc;
		atmel_port->release_tx = &atmel_release_tx_pdc;
	} else {
		atmel_port->prepare_tx = NULL;
		atmel_port->schedule_tx = &atmel_tx_chars;
		atmel_port->release_tx = NULL;
	}
}

/*
 * Get ip name usart or uart
 */
static void atmel_get_ip_name(struct uart_port *port)
{
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
	int name = atmel_uart_readl(port, ATMEL_US_NAME);
	u32 version;
	u32 usart, dbgu_uart, new_uart;
	/* ASCII decoding for IP version */
	usart = 0x55534152;	/* USAR(T) */
	dbgu_uart = 0x44424755;	/* DBGU */
	new_uart = 0x55415254;	/* UART */

	/*
	 * Only USART devices from at91sam9260 SOC implement fractional
	 * baudrate. It is available for all asynchronous modes, with the
	 * following restriction: the sampling clock's duty cycle is not
	 * constant.
	 */
	atmel_port->has_frac_baudrate = false;
	atmel_port->has_hw_timer = false;

	if (name == new_uart) {
		dev_dbg(port->dev, "Uart with hw timer");
		atmel_port->has_hw_timer = true;
		atmel_port->rtor = ATMEL_UA_RTOR;
	} else if (name == usart) {
		dev_dbg(port->dev, "Usart\n");
		atmel_port->has_frac_baudrate = true;
		atmel_port->has_hw_timer = true;
		atmel_port->rtor = ATMEL_US_RTOR;
	} else if (name == dbgu_uart) {
		dev_dbg(port->dev, "Dbgu or uart without hw timer\n");
	} else {
		/* fallback for older SoCs: use version field */
		version = atmel_uart_readl(port, ATMEL_US_VERSION);
		switch (version) {
		case 0x302:
		case 0x10213:
		case 0x10302:
			dev_dbg(port->dev, "This version is usart\n");
			atmel_port->has_frac_baudrate = true;
			atmel_port->has_hw_timer = true;
			atmel_port->rtor = ATMEL_US_RTOR;
			break;
		case 0x203:
		case 0x10202:
			dev_dbg(port->dev, "This version is uart\n");
			break;
		default:
			dev_err(port->dev, "Not supported ip name nor version, set to uart\n");
		}
	}
}

/*
 * Perform initialization and enable port for reception
 */
static int atmel_startup(struct uart_port *port)
{
	struct platform_device *pdev = to_platform_device(port->dev);
	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
	 */
	atmel_uart_writel(port, ATMEL_US_IDR, -1);
	atmel_port->ms_irq_enabled = false;

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

	atomic_set(&atmel_port->tasklet_shutdown, 0);
	tasklet_init(&atmel_port->tasklet_rx, atmel_tasklet_rx_func,
			(unsigned long)port);
	tasklet_init(&atmel_port->tasklet_tx, atmel_tasklet_tx_func,
			(unsigned long)port);

	/*
	 * Initialize DMA (if necessary)
	 */
	atmel_init_property(atmel_port, pdev);
	atmel_set_ops(port);

	if (atmel_port->prepare_rx) {
		retval = atmel_port->prepare_rx(port);
		if (retval < 0)
			atmel_set_ops(port);
	}

	if (atmel_port->prepare_tx) {
		retval = atmel_port->prepare_tx(port);
		if (retval < 0)
			atmel_set_ops(port);
	}

	/*
	 * Enable FIFO when available
	 */
	if (atmel_port->fifo_size) {
		unsigned int txrdym = ATMEL_US_ONE_DATA;
		unsigned int rxrdym = ATMEL_US_ONE_DATA;
		unsigned int fmr;

		atmel_uart_writel(port, ATMEL_US_CR,
				  ATMEL_US_FIFOEN |
				  ATMEL_US_RXFCLR |
				  ATMEL_US_TXFLCLR);

		if (atmel_use_dma_tx(port))
			txrdym = ATMEL_US_FOUR_DATA;

		fmr = ATMEL_US_TXRDYM(txrdym) | ATMEL_US_RXRDYM(rxrdym);
		if (atmel_port->rts_high &&
		    atmel_port->rts_low)
			fmr |=	ATMEL_US_FRTSC |
				ATMEL_US_RXFTHRES(atmel_port->rts_high) |
				ATMEL_US_RXFTHRES2(atmel_port->rts_low);

		atmel_uart_writel(port, ATMEL_US_FMR, fmr);
	}

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

	/*
	 * Finally, enable the serial port
	 */
	atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_RSTSTA | ATMEL_US_RSTRX);
	/* enable xmit & rcvr */
	atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN | ATMEL_US_RXEN);
	atmel_port->tx_stopped = false;

	timer_setup(&atmel_port->uart_timer, atmel_uart_timer_callback, 0);

	if (atmel_use_pdc_rx(port)) {
		/* set UART timeout */
		if (!atmel_port->has_hw_timer) {
			mod_timer(&atmel_port->uart_timer,
					jiffies + uart_poll_timeout(port));
		/* set USART timeout */
		} else {
			atmel_uart_writel(port, atmel_port->rtor,
					  PDC_RX_TIMEOUT);
			atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_STTTO);

			atmel_uart_writel(port, ATMEL_US_IER,
					  ATMEL_US_ENDRX | ATMEL_US_TIMEOUT);
		}
		/* enable PDC controller */
		atmel_uart_writel(port, ATMEL_PDC_PTCR, ATMEL_PDC_RXTEN);
	} else if (atmel_use_dma_rx(port)) {
		/* set UART timeout */
		if (!atmel_port->has_hw_timer) {
			mod_timer(&atmel_port->uart_timer,
					jiffies + uart_poll_timeout(port));
		/* set USART timeout */
		} else {
			atmel_uart_writel(port, atmel_port->rtor,
					  PDC_RX_TIMEOUT);
			atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_STTTO);

			atmel_uart_writel(port, ATMEL_US_IER,
					  ATMEL_US_TIMEOUT);
		}
	} else {
		/* enable receive only */
		atmel_uart_writel(port, ATMEL_US_IER, ATMEL_US_RXRDY);
	}

	return 0;
}

/*
 * 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_pdc_tx(port)) {
		atmel_uart_writel(port, ATMEL_PDC_TCR, 0);
		atmel_port->pdc_tx.ofs = 0;
	}
	/*
	 * in uart_flush_buffer(), the xmit circular buffer has just
	 * been cleared, so we have to reset tx_len accordingly.
	 */
	atmel_port->tx_len = 0;
}

/*
 * Disable the port
 */
static void atmel_shutdown(struct uart_port *port)
{
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

	/* Disable modem control lines interrupts */
	atmel_disable_ms(port);

	/* Disable interrupts at device level */
	atmel_uart_writel(port, ATMEL_US_IDR, -1);

	/* Prevent spurious interrupts from scheduling the tasklet */
	atomic_inc(&atmel_port->tasklet_shutdown);

	/*
	 * Prevent any tasklets being scheduled during
	 * cleanup
	 */
	del_timer_sync(&atmel_port->uart_timer);

	/* Make sure that no interrupt is on the fly */
	synchronize_irq(port->irq);

	/*
	 * Clear out any scheduled tasklets before
	 * we destroy the buffers
	 */
	tasklet_kill(&atmel_port->tasklet_rx);
	tasklet_kill(&atmel_port->tasklet_tx);

	/*
	 * Ensure everything is stopped and
	 * disable port and break condition.
	 */
	atmel_stop_rx(port);
	atmel_stop_tx(port);

	atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_RSTSTA);

	/*
	 * Shut-down the DMA.
	 */
	if (atmel_port->release_rx)
		atmel_port->release_rx(port);
	if (atmel_port->release_tx)
		atmel_port->release_tx(port);

	/*
	 * Reset ring buffer pointers
	 */
	atmel_port->rx_ring.head = 0;
	atmel_port->rx_ring.tail = 0;

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

	atmel_flush_buffer(port);
}

/*
 * 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_prepare_enable(atmel_port->clk);

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

		/*
		 * Disable the peripheral clock for this serial port.
		 * This is called on uart_close() or a suspend event.
		 */
		clk_disable_unprepare(atmel_port->clk);
		break;
	default:
		dev_err(port->dev, "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)
{
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
	unsigned long flags;
	unsigned int old_mode, mode, imr, quot, baud, div, cd, fp = 0;

	/* save the current mode register */
	mode = old_mode = atmel_uart_readl(port, ATMEL_US_MR);

	/* reset the mode, clock divisor, parity, stop bits and data size */
	mode &= ~(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);

	/* 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;

	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 & (IGNBRK | BRKINT | PARMRK))
		port->read_status_mask |= ATMEL_US_RXBRK;

	if (atmel_use_pdc_rx(port))
		/* need to enable error interrupts */
		atmel_uart_writel(port, ATMEL_US_IER, 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 = atmel_uart_readl(port, ATMEL_US_IMR);
	atmel_uart_writel(port, ATMEL_US_IDR, -1);

	/* disable receiver and transmitter */
	atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXDIS | ATMEL_US_RXDIS);
	atmel_port->tx_stopped = true;

	/* mode */
	if (port->rs485.flags & SER_RS485_ENABLED) {
		atmel_uart_writel(port, ATMEL_US_TTGR,
				  port->rs485.delay_rts_after_send);
		mode |= ATMEL_US_USMODE_RS485;
	} else if (termios->c_cflag & CRTSCTS) {
		/* RS232 with hardware handshake (RTS/CTS) */
		if (atmel_use_fifo(port) &&
		    !mctrl_gpio_to_gpiod(atmel_port->gpios, UART_GPIO_CTS)) {
			/*
			 * with ATMEL_US_USMODE_HWHS set, the controller will
			 * be able to drive the RTS pin high/low when the RX
			 * FIFO is above RXFTHRES/below RXFTHRES2.
			 * It will also disable the transmitter when the CTS
			 * pin is high.
			 * This mode is not activated if CTS pin is a GPIO
			 * because in this case, the transmitter is always
			 * disabled (there must be an internal pull-up
			 * responsible for this behaviour).
			 * If the RTS pin is a GPIO, the controller won't be
			 * able to drive it according to the FIFO thresholds,
			 * but it will be handled by the driver.
			 */
			mode |= ATMEL_US_USMODE_HWHS;
		} else {
			/*
			 * For platforms without FIFO, the flow control is
			 * handled by the driver.
			 */
			mode |= ATMEL_US_USMODE_NORMAL;
		}
	} else {
		/* RS232 without hadware handshake */
		mode |= ATMEL_US_USMODE_NORMAL;
	}

	/* set the mode, clock divisor, parity, stop bits and data size */
	atmel_uart_writel(port, ATMEL_US_MR, mode);

	/*
	 * when switching the mode, set the RTS line state according to the
	 * new mode, otherwise keep the former state
	 */
	if ((old_mode & ATMEL_US_USMODE) != (mode & ATMEL_US_USMODE)) {
		unsigned int rts_state;

		if ((mode & ATMEL_US_USMODE) == ATMEL_US_USMODE_HWHS) {
			/* let the hardware control the RTS line */
			rts_state = ATMEL_US_RTSDIS;
		} else {
			/* force RTS line to low level */
			rts_state = ATMEL_US_RTSEN;
		}

		atmel_uart_writel(port, ATMEL_US_CR, rts_state);
	}

	/*
	 * Set the baud rate:
	 * Fractional baudrate allows to setup output frequency more
	 * accurately. This feature is enabled only when using normal mode.
	 * baudrate = selected clock / (8 * (2 - OVER) * (CD + FP / 8))
	 * Currently, OVER is always set to 0 so we get
	 * baudrate = selected clock / (16 * (CD + FP / 8))
	 * then
	 * 8 CD + FP = selected clock / (2 * baudrate)
	 */
	if (atmel_port->has_frac_baudrate) {
		div = DIV_ROUND_CLOSEST(port->uartclk, baud * 2);
		cd = div >> 3;
		fp = div & ATMEL_US_FP_MASK;
	} else {
		cd = uart_get_divisor(port, baud);
	}

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

	atmel_uart_writel(port, ATMEL_US_BRGR, quot);
	atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_RSTSTA | ATMEL_US_RSTRX);
	atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN | ATMEL_US_RXEN);
	atmel_port->tx_stopped = false;

	/* restore interrupts */
	atmel_uart_writel(port, ATMEL_US_IER, imr);

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

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

static void atmel_set_ldisc(struct uart_port *port, struct ktermios *termios)
{
	if (termios->c_line == N_PPS) {
		port->flags |= UPF_HARDPPS_CD;
		spin_lock_irq(&port->lock);
		atmel_enable_ms(port);
		spin_unlock_irq(&port->lock);
	} else {
		port->flags &= ~UPF_HARDPPS_CD;
		if (!UART_ENABLE_MS(port, termios->c_cflag)) {
			spin_lock_irq(&port->lock);
			atmel_disable_ms(port);
			spin_unlock_irq(&port->lock);
		}
	}
}

/*
 * 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 (port->mapbase != (unsigned long)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 (!(atmel_uart_readl(port, ATMEL_US_CSR) & ATMEL_US_RXRDY))
		cpu_relax();

	return atmel_uart_read_char(port);
}

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

	atmel_uart_write_char(port, ch);
}
#endif

static const 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,
#ifdef CONFIG_CONSOLE_POLL
	.poll_get_char	= atmel_poll_get_char,
	.poll_put_char	= atmel_poll_put_char,
#endif
};

/*
 * Configure the port from the platform device resource info.
 */
static int atmel_init_port(struct atmel_uart_port *atmel_port,
				      struct platform_device *pdev)
{
	int ret;
	struct uart_port *port = &atmel_port->uart;

	atmel_init_property(atmel_port, pdev);
	atmel_set_ops(port);

	uart_get_rs485_mode(&pdev->dev, &port->rs485);

	port->iotype		= UPIO_MEM;
	port->flags		= UPF_BOOT_AUTOCONF | UPF_IOREMAP;
	port->ops		= &atmel_pops;
	port->fifosize		= 1;
	port->dev		= &pdev->dev;
	port->mapbase	= pdev->resource[0].start;
	port->irq	= pdev->resource[1].start;
	port->rs485_config	= atmel_config_rs485;
	port->membase	= NULL;

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

	/* for console, the clock could already be configured */
	if (!atmel_port->clk) {
		atmel_port->clk = clk_get(&pdev->dev, "usart");
		if (IS_ERR(atmel_port->clk)) {
			ret = PTR_ERR(atmel_port->clk);
			atmel_port->clk = NULL;
			return ret;
		}
		ret = clk_prepare_enable(atmel_port->clk);
		if (ret) {
			clk_put(atmel_port->clk);
			atmel_port->clk = NULL;
			return ret;
		}
		port->uartclk = clk_get_rate(atmel_port->clk);
		clk_disable_unprepare(atmel_port->clk);
		/* only enable clock when USART is in use */
	}

	/* Use TXEMPTY for interrupt when rs485 else TXRDY or ENDTX|TXBUFE */
	if (port->rs485.flags & SER_RS485_ENABLED)
		atmel_port->tx_done_mask = ATMEL_US_TXEMPTY;
	else if (atmel_use_pdc_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;
	}

	return 0;
}

#ifdef CONFIG_SERIAL_ATMEL_CONSOLE
static void atmel_console_putchar(struct uart_port *port, int ch)
{
	while (!(atmel_uart_readl(port, ATMEL_US_CSR) & ATMEL_US_TXRDY))
		cpu_relax();
	atmel_uart_write_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 = atmel_uart_readl(port, ATMEL_US_IMR);
	atmel_uart_writel(port, ATMEL_US_IDR,
			  ATMEL_US_RXRDY | atmel_port->tx_done_mask);

	/* Store PDC transmit status and disable it */
	pdc_tx = atmel_uart_readl(port, ATMEL_PDC_PTSR) & ATMEL_PDC_TXTEN;
	atmel_uart_writel(port, ATMEL_PDC_PTCR, ATMEL_PDC_TXTDIS);

	/* Make sure that tx path is actually able to send characters */
	atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN);
	atmel_port->tx_stopped = false;

	uart_console_write(port, s, count, atmel_console_putchar);

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

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

	/* set interrupts back the way they were */
	atmel_uart_writel(port, ATMEL_US_IER, 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 = atmel_uart_readl(port, ATMEL_US_BRGR) & ATMEL_US_CD;
	if (!quot)
		return;

	mr = atmel_uart_readl(port, ATMEL_US_MR) & ATMEL_US_CHRL;
	if (mr == ATMEL_US_CHRL_8)
		*bits = 8;
	else
		*bits = 7;

	mr = atmel_uart_readl(port, ATMEL_US_MR) & 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)
{
	int ret;
	struct uart_port *port = &atmel_ports[co->index].uart;
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
	int baud = 115200;
	int bits = 8;
	int parity = 'n';
	int flow = 'n';

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

	ret = clk_prepare_enable(atmel_ports[co->index].clk);
	if (ret)
		return ret;

	atmel_uart_writel(port, ATMEL_US_IDR, -1);
	atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_RSTSTA | ATMEL_US_RSTRX);
	atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN | ATMEL_US_RXEN);
	atmel_port->tx_stopped = false;

	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)

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 (!(atmel_uart_readl(port, ATMEL_US_CSR) &
			 ATMEL_US_TXEMPTY))
			cpu_relax();
	}

	if (atmel_is_console_port(port) && !console_suspend_enabled) {
		/* Cache register values as we won't get a full shutdown/startup
		 * cycle
		 */
		atmel_port->cache.mr = atmel_uart_readl(port, ATMEL_US_MR);
		atmel_port->cache.imr = atmel_uart_readl(port, ATMEL_US_IMR);
		atmel_port->cache.brgr = atmel_uart_readl(port, ATMEL_US_BRGR);
		atmel_port->cache.rtor = atmel_uart_readl(port,
							  atmel_port->rtor);
		atmel_port->cache.ttgr = atmel_uart_readl(port, ATMEL_US_TTGR);
		atmel_port->cache.fmr = atmel_uart_readl(port, ATMEL_US_FMR);
		atmel_port->cache.fimr = atmel_uart_readl(port, ATMEL_US_FIMR);
	}

	/* 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()) {
		unsigned long flags;

		spin_lock_irqsave(&atmel_port->lock_suspended, flags);
		atmel_port->suspended = true;
		spin_unlock_irqrestore(&atmel_port->lock_suspended, flags);
		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);
	unsigned long flags;

	if (atmel_is_console_port(port) && !console_suspend_enabled) {
		atmel_uart_writel(port, ATMEL_US_MR, atmel_port->cache.mr);
		atmel_uart_writel(port, ATMEL_US_IER, atmel_port->cache.imr);
		atmel_uart_writel(port, ATMEL_US_BRGR, atmel_port->cache.brgr);
		atmel_uart_writel(port, atmel_port->rtor,
				  atmel_port->cache.rtor);
		atmel_uart_writel(port, ATMEL_US_TTGR, atmel_port->cache.ttgr);

		if (atmel_port->fifo_size) {
			atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_FIFOEN |
					  ATMEL_US_RXFCLR | ATMEL_US_TXFLCLR);
			atmel_uart_writel(port, ATMEL_US_FMR,
					  atmel_port->cache.fmr);
			atmel_uart_writel(port, ATMEL_US_FIER,
					  atmel_port->cache.fimr);
		}
		atmel_start_rx(port);
	}

	spin_lock_irqsave(&atmel_port->lock_suspended, flags);
	if (atmel_port->pending) {
		atmel_handle_receive(port, atmel_port->pending);
		atmel_handle_status(port, atmel_port->pending,
				    atmel_port->pending_status);
		atmel_handle_transmit(port, atmel_port->pending);
		atmel_port->pending = 0;
	}
	atmel_port->suspended = false;
	spin_unlock_irqrestore(&atmel_port->lock_suspended, flags);

	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 void atmel_serial_probe_fifos(struct atmel_uart_port *atmel_port,
				     struct platform_device *pdev)
{
	atmel_port->fifo_size = 0;
	atmel_port->rts_low = 0;
	atmel_port->rts_high = 0;

	if (of_property_read_u32(pdev->dev.of_node,
				 "atmel,fifo-size",
				 &atmel_port->fifo_size))
		return;

	if (!atmel_port->fifo_size)
		return;

	if (atmel_port->fifo_size < ATMEL_MIN_FIFO_SIZE) {
		atmel_port->fifo_size = 0;
		dev_err(&pdev->dev, "Invalid FIFO size\n");
		return;
	}

	/*
	 * 0 <= rts_low <= rts_high <= fifo_size
	 * Once their CTS line asserted by the remote peer, some x86 UARTs tend
	 * to flush their internal TX FIFO, commonly up to 16 data, before
	 * actually stopping to send new data. So we try to set the RTS High
	 * Threshold to a reasonably high value respecting this 16 data
	 * empirical rule when possible.
	 */
	atmel_port->rts_high = max_t(int, atmel_port->fifo_size >> 1,
			       atmel_port->fifo_size - ATMEL_RTS_HIGH_OFFSET);
	atmel_port->rts_low  = max_t(int, atmel_port->fifo_size >> 2,
			       atmel_port->fifo_size - ATMEL_RTS_LOW_OFFSET);

	dev_info(&pdev->dev, "Using FIFO (%u data)\n",
		 atmel_port->fifo_size);
	dev_dbg(&pdev->dev, "RTS High Threshold : %2u data\n",
		atmel_port->rts_high);
	dev_dbg(&pdev->dev, "RTS Low Threshold  : %2u data\n",
		atmel_port->rts_low);
}

static int atmel_serial_probe(struct platform_device *pdev)
{
	struct atmel_uart_port *atmel_port;
	struct device_node *np = pdev->dev.of_node;
	void *data;
	int ret = -ENODEV;
	bool rs485_enabled;

	BUILD_BUG_ON(ATMEL_SERIAL_RINGSIZE & (ATMEL_SERIAL_RINGSIZE - 1));

	ret = of_alias_get_id(np, "serial");
	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, ATMEL_MAX_UART);

	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;
	}

	atmel_port = &atmel_ports[ret];
	atmel_port->backup_imr = 0;
	atmel_port->uart.line = ret;
	atmel_serial_probe_fifos(atmel_port, pdev);

	atomic_set(&atmel_port->tasklet_shutdown, 0);
	spin_lock_init(&atmel_port->lock_suspended);

	ret = atmel_init_port(atmel_port, pdev);
	if (ret)
		goto err_clear_bit;

	atmel_port->gpios = mctrl_gpio_init(&atmel_port->uart, 0);
	if (IS_ERR(atmel_port->gpios)) {
		ret = PTR_ERR(atmel_port->gpios);
		goto err_clear_bit;
	}

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

	rs485_enabled = atmel_port->uart.rs485.flags & SER_RS485_ENABLED;

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

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

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

	/*
	 * The peripheral clock has been disabled by atmel_init_port():
	 * enable it before accessing I/O registers
	 */
	clk_prepare_enable(atmel_port->clk);

	if (rs485_enabled) {
		atmel_uart_writel(&atmel_port->uart, ATMEL_US_MR,
				  ATMEL_US_USMODE_NORMAL);
		atmel_uart_writel(&atmel_port->uart, ATMEL_US_CR,
				  ATMEL_US_RTSEN);
	}

	/*
	 * Get port name of usart or uart
	 */
	atmel_get_ip_name(&atmel_port->uart);

	/*
	 * The peripheral clock can now safely be disabled till the port
	 * is used
	 */
	clk_disable_unprepare(atmel_port->clk);

	return 0;

err_add_port:
	kfree(atmel_port->rx_ring.buf);
	atmel_port->rx_ring.buf = NULL;
err_alloc_ring:
	if (!atmel_is_console_port(&atmel_port->uart)) {
		clk_put(atmel_port->clk);
		atmel_port->clk = NULL;
	}
err_clear_bit:
	clear_bit(atmel_port->uart.line, atmel_ports_in_use);
err:
	return ret;
}

/*
 * Even if the driver is not modular, it makes sense to be able to
 * unbind a device: there can be many bound devices, and there are
 * situations where dynamic binding and unbinding can be useful.
 *
 * For example, a connected device can require a specific firmware update
 * protocol that needs bitbanging on IO lines, but use the regular serial
 * port in the normal case.
 */
static int 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;

	tasklet_kill(&atmel_port->tasklet_rx);
	tasklet_kill(&atmel_port->tasklet_tx);

	device_init_wakeup(&pdev->dev, 0);

	ret = uart_remove_one_port(&atmel_uart, port);

	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);
	atmel_port->clk = NULL;

	return ret;
}

static struct platform_driver atmel_serial_driver = {
	.probe		= atmel_serial_probe,
	.remove		= atmel_serial_remove,
	.suspend	= atmel_serial_suspend,
	.resume		= atmel_serial_resume,
	.driver		= {
		.name			= "atmel_usart",
		.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;
}
device_initcall(atmel_serial_init);