atmel_serial.c

	tty_flip_buffer_push(tport);
	spin_lock(&port->lock);

	UART_PUT_IER(port, 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,
		    (int)ring->buf & ~PAGE_MASK);
	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 %x\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;

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

	tasklet_schedule(&atmel_port->tasklet);
	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)) {
			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);
	}

	if (atmel_use_dma_rx(port)) {
		if (pending & ATMEL_US_TIMEOUT) {
			UART_PUT_IDR(port, ATMEL_US_TIMEOUT);
			tasklet_schedule(&atmel_port->tasklet);
		}
	}

	/* 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;
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
	unsigned int status, pending, pass_counter = 0;
	bool gpio_handled = false;

	do {
		status = atmel_get_lines_status(port);
		pending = status & UART_GET_IMR(port);
		if (!gpio_handled) {
			/*
			 * Dealing with GPIO interrupt
			 */
			if (irq == atmel_port->gpio_irq[UART_GPIO_CTS])
				pending |= ATMEL_US_CTSIC;

			if (irq == atmel_port->gpio_irq[UART_GPIO_DSR])
				pending |= ATMEL_US_DSRIC;

			if (irq == atmel_port->gpio_irq[UART_GPIO_RI])
				pending |= ATMEL_US_RIIC;

			if (irq == atmel_port->gpio_irq[UART_GPIO_DCD])
				pending |= ATMEL_US_DCDIC;

			gpio_handled = true;
		}
		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;
}

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 (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 ((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 */
		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(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;
			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(tport);
	spin_lock(&port->lock);

	UART_PUT_IER(port, 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;

	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);

	return 0;
}

/*
 * 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);

	atmel_port->schedule_tx(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;
	}

	atmel_port->schedule_rx(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;
	struct atmel_uart_data *pdata = dev_get_platdata(&pdev->dev);

	if (np) {
		/* DMA/PDC usage specification */
		if (of_get_property(np, "atmel,use-dma-rx", NULL)) {
			if (of_get_property(np, "dmas", NULL)) {
				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_get_property(np, "atmel,use-dma-tx", NULL)) {
			if (of_get_property(np, "dmas", NULL)) {
				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;
		}

	} else {
		atmel_port->use_pdc_rx  = pdata->use_dma_rx;
		atmel_port->use_pdc_tx  = pdata->use_dma_tx;
		atmel_port->use_dma_rx  = false;
		atmel_port->use_dma_tx  = false;
	}

}

static void atmel_init_rs485(struct uart_port *port,
				struct platform_device *pdev)
{
	struct device_node *np = pdev->dev.of_node;
	struct atmel_uart_data *pdata = dev_get_platdata(&pdev->dev);

	if (np) {
		u32 rs485_delay[2];
		/* rs485 properties */
		if (of_property_read_u32_array(np, "rs485-rts-delay",
					rs485_delay, 2) == 0) {
			struct serial_rs485 *rs485conf = &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;
		}
	} else {
		port->rs485       = pdata->rs485;
	}

}

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 = UART_GET_IP_NAME(port);
	u32 version;
	int usart, uart;
	/* usart and uart ascii */
	usart = 0x55534152;
	uart = 0x44424755;

	atmel_port->is_usart = false;

	if (name == usart) {
		dev_dbg(port->dev, "This is usart\n");
		atmel_port->is_usart = true;
	} else if (name == uart) {
		dev_dbg(port->dev, "This is uart\n");
		atmel_port->is_usart = false;
	} else {
		/* fallback for older SoCs: use version field */
		version = UART_GET_IP_VERSION(port);
		switch (version) {
		case 0x302:
		case 0x10213:
			dev_dbg(port->dev, "This version is usart\n");
			atmel_port->is_usart = true;
			break;
		case 0x203:
		case 0x10202:
			dev_dbg(port->dev, "This version is uart\n");
			atmel_port->is_usart = false;
			break;
		default:
			dev_err(port->dev, "Not supported ip name nor version, set to uart\n");
		}
	}
}

static void atmel_free_gpio_irq(struct uart_port *port)
{
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
	enum mctrl_gpio_idx i;

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

static int atmel_request_gpio_irq(struct uart_port *port)
{
	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
	int *irq = atmel_port->gpio_irq;
	enum mctrl_gpio_idx i;
	int err = 0;

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

		irq_set_status_flags(irq[i], IRQ_NOAUTOEN);
		err = request_irq(irq[i], atmel_interrupt, IRQ_TYPE_EDGE_BOTH,
				  "atmel_serial", port);
		if (err)
			dev_err(port->dev, "atmel_startup - Can't get %d irq\n",
				irq[i]);
	}

	/*
	 * If something went wrong, rollback.
	 */
	while (err && (--i >= 0))
		if (irq[i] >= 0)
			free_irq(irq[i], port);

	return err;
}

/*
 * 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
	 */
	UART_PUT_IDR(port, -1);
	atmel_port->ms_irq_enabled = false;

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

	/*
	 * Get the GPIO lines IRQ
	 */
	retval = atmel_request_gpio_irq(port);
	if (retval)
		goto free_irq;

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

	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);
	}

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

	setup_timer(&atmel_port->uart_timer,
			atmel_uart_timer_callback,
			(unsigned long)port);

	if (atmel_use_pdc_rx(port)) {
		/* set UART timeout */
		if (!atmel_port->is_usart) {
			mod_timer(&atmel_port->uart_timer,
					jiffies + uart_poll_timeout(port));
		/* set USART timeout */
		} else {
			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 if (atmel_use_dma_rx(port)) {
		/* set UART timeout */
		if (!atmel_port->is_usart) {
			mod_timer(&atmel_port->uart_timer,
					jiffies + uart_poll_timeout(port));
		/* set USART timeout */
		} else {
			UART_PUT_RTOR(port, PDC_RX_TIMEOUT);
			UART_PUT_CR(port, ATMEL_US_STTTO);

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

	return 0;

free_irq:
	free_irq(port->irq, port);

	return retval;
}

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

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

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

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

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

	UART_PUT_CR(port, ATMEL_US_RSTSTA);
	UART_PUT_IDR(port, -1);


	/*
	 * 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_free_gpio_irq(port);

	atmel_port->ms_irq_enabled = false;

	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 */
		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_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)
{
	unsigned long flags;
	unsigned int old_mode, mode, imr, quot, baud;

	/* save the current mode register */
	mode = old_mode = UART_GET_MR(port);

	/* 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);
	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;

	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))