serial: tegra: add serial driver

NVIDIA's Tegra has multiple UART controller which supports:
- APB DMA based controller fifo read/write.
- End Of Data interrupt in incoming data to know whether end
  of frame achieve or not.
- HW controlled RTS and CTS flow control to reduce SW overhead.

Add serial driver to use all above feature.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Acked-by: Alan Cox <alan@linux.intel.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

4 files changed, 1435 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/serial/nvidia,tegra20-hsuart.txt b/Documentation/devicetree/bindings/serial/nvidia,tegra20-hsuart.txt
new file mode 100644
index 0000000..392a449
--- /dev/null
+++ b/Documentation/devicetree/bindings/serial/nvidia,tegra20-hsuart.txt
@@ -0,0 +1,24 @@
+NVIDIA Tegra20/Tegra30 high speed (DMA based) UART controller driver.
+
+Required properties:
+- compatible : should be "nvidia,tegra30-hsuart", "nvidia,tegra20-hsuart".
+- reg: Should contain UART controller registers location and length.
+- interrupts: Should contain UART controller interrupts.
+- nvidia,dma-request-selector : The Tegra DMA controller's phandle and
+  request selector for this UART controller.
+
+Optional properties:
+- nvidia,enable-modem-interrupt: Enable modem interrupts. Should be enable
+		only if all 8 lines of UART controller are pinmuxed.
+
+Example:
+
+serial@70006000 {
+	compatible = "nvidia,tegra30-hsuart", "nvidia,tegra20-hsuart";
+	reg = <0x70006000 0x40>;
+	reg-shift = <2>;
+	interrupts = <0 36 0x04>;
+	nvidia,dma-request-selector = <&apbdma 8>;
+	nvidia,enable-modem-interrupt;
+	status = "disabled";
+};
diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 59c23d0..aff3cd3 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -269,6 +269,17 @@ config SERIAL_SIRFSOC_CONSOLE
           your boot loader about how to pass options to the kernel at
           boot time.)
 
+config SERIAL_TEGRA
+	tristate "NVIDIA Tegra20/30 SoC serial controller"
+	depends on ARCH_TEGRA && TEGRA20_APB_DMA
+	select SERIAL_CORE
+	help
+	  Support for the on-chip UARTs on the NVIDIA Tegra series SOCs
+	  providing /dev/ttyHS0, 1, 2, 3 and 4 (note, some machines may not
+	  provide all of these ports, depending on how the serial port
+	  are enabled). This driver uses the APB DMA to achieve higher baudrate
+	  and better performance.
+
 config SERIAL_MAX3100
 	tristate "MAX3100 support"
 	depends on SPI
diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
index df1b998..82e4306 100644
--- a/drivers/tty/serial/Makefile
+++ b/drivers/tty/serial/Makefile
@@ -80,6 +80,7 @@ obj-$(CONFIG_SERIAL_MXS_AUART) += mxs-auart.o
 obj-$(CONFIG_SERIAL_LANTIQ)	+= lantiq.o
 obj-$(CONFIG_SERIAL_XILINX_PS_UART) += xilinx_uartps.o
 obj-$(CONFIG_SERIAL_SIRFSOC) += sirfsoc_uart.o
+obj-$(CONFIG_SERIAL_TEGRA) += serial-tegra.o
 obj-$(CONFIG_SERIAL_AR933X)   += ar933x_uart.o
 obj-$(CONFIG_SERIAL_EFM32_UART) += efm32-uart.o
 obj-$(CONFIG_SERIAL_ARC)	+= arc_uart.o
diff --git a/drivers/tty/serial/serial-tegra.c b/drivers/tty/serial/serial-tegra.c
new file mode 100644
index 0000000..cc4072f
--- /dev/null
+++ b/drivers/tty/serial/serial-tegra.c
@@ -0,0 +1,1399 @@
+/*
+ * serial_tegra.c
+ *
+ * High-speed serial driver for NVIDIA Tegra SoCs
+ *
+ * Copyright (c) 2012-2013, NVIDIA CORPORATION.  All rights reserved.
+ *
+ * Author: Laxman Dewangan <ldewangan@nvidia.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/clk.h>
+#include <linux/debugfs.h>
+#include <linux/delay.h>
+#include <linux/dmaengine.h>
+#include <linux/dma-mapping.h>
+#include <linux/dmapool.h>
+#include <linux/io.h>
+#include <linux/irq.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/pagemap.h>
+#include <linux/platform_device.h>
+#include <linux/serial.h>
+#include <linux/serial_8250.h>
+#include <linux/serial_core.h>
+#include <linux/serial_reg.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/termios.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+
+#include <mach/clk.h>
+
+#define TEGRA_UART_TYPE				"TEGRA_UART"
+#define TX_EMPTY_STATUS				(UART_LSR_TEMT | UART_LSR_THRE)
+#define BYTES_TO_ALIGN(x)			((unsigned long)(x) & 0x3)
+
+#define TEGRA_UART_RX_DMA_BUFFER_SIZE		4096
+#define TEGRA_UART_LSR_TXFIFO_FULL		0x100
+#define TEGRA_UART_IER_EORD			0x20
+#define TEGRA_UART_MCR_RTS_EN			0x40
+#define TEGRA_UART_MCR_CTS_EN			0x20
+#define TEGRA_UART_LSR_ANY			(UART_LSR_OE | UART_LSR_BI | \
+						UART_LSR_PE | UART_LSR_FE)
+#define TEGRA_UART_IRDA_CSR			0x08
+#define TEGRA_UART_SIR_ENABLED			0x80
+
+#define TEGRA_UART_TX_PIO			1
+#define TEGRA_UART_TX_DMA			2
+#define TEGRA_UART_MIN_DMA			16
+#define TEGRA_UART_FIFO_SIZE			32
+
+/*
+ * Tx fifo trigger level setting in tegra uart is in
+ * reverse way then conventional uart.
+ */
+#define TEGRA_UART_TX_TRIG_16B			0x00
+#define TEGRA_UART_TX_TRIG_8B			0x10
+#define TEGRA_UART_TX_TRIG_4B			0x20
+#define TEGRA_UART_TX_TRIG_1B			0x30
+
+#define TEGRA_UART_MAXIMUM			5
+
+/* Default UART setting when started: 115200 no parity, stop, 8 data bits */
+#define TEGRA_UART_DEFAULT_BAUD			115200
+#define TEGRA_UART_DEFAULT_LSR			UART_LCR_WLEN8
+
+/* Tx transfer mode */
+#define TEGRA_TX_PIO				1
+#define TEGRA_TX_DMA				2
+
+/**
+ * tegra_uart_chip_data: SOC specific data.
+ *
+ * @tx_fifo_full_status: Status flag available for checking tx fifo full.
+ * @allow_txfifo_reset_fifo_mode: allow_tx fifo reset with fifo mode or not.
+ *			Tegra30 does not allow this.
+ * @support_clk_src_div: Clock source support the clock divider.
+ */
+struct tegra_uart_chip_data {
+	bool	tx_fifo_full_status;
+	bool	allow_txfifo_reset_fifo_mode;
+	bool	support_clk_src_div;
+};
+
+struct tegra_uart_port {
+	struct uart_port			uport;
+	const struct tegra_uart_chip_data	*cdata;
+
+	struct clk				*uart_clk;
+	unsigned int				current_baud;
+
+	/* Register shadow */
+	unsigned long				fcr_shadow;
+	unsigned long				mcr_shadow;
+	unsigned long				lcr_shadow;
+	unsigned long				ier_shadow;
+	bool					rts_active;
+
+	int					tx_in_progress;
+	unsigned int				tx_bytes;
+
+	bool					enable_modem_interrupt;
+
+	bool					rx_timeout;
+	int					rx_in_progress;
+	int					symb_bit;
+	int					dma_req_sel;
+
+	struct dma_chan				*rx_dma_chan;
+	struct dma_chan				*tx_dma_chan;
+	dma_addr_t				rx_dma_buf_phys;
+	dma_addr_t				tx_dma_buf_phys;
+	unsigned char				*rx_dma_buf_virt;
+	unsigned char				*tx_dma_buf_virt;
+	struct dma_async_tx_descriptor		*tx_dma_desc;
+	struct dma_async_tx_descriptor		*rx_dma_desc;
+	dma_cookie_t				tx_cookie;
+	dma_cookie_t				rx_cookie;
+	int					tx_bytes_requested;
+	int					rx_bytes_requested;
+};
+
+static void tegra_uart_start_next_tx(struct tegra_uart_port *tup);
+static int tegra_uart_start_rx_dma(struct tegra_uart_port *tup);
+
+static inline unsigned long tegra_uart_read(struct tegra_uart_port *tup,
+		unsigned long reg)
+{
+	return readl(tup->uport.membase + (reg << tup->uport.regshift));
+}
+
+static inline void tegra_uart_write(struct tegra_uart_port *tup, unsigned val,
+	unsigned long reg)
+{
+	writel(val, tup->uport.membase + (reg << tup->uport.regshift));
+}
+
+static inline struct tegra_uart_port *to_tegra_uport(struct uart_port *u)
+{
+	return container_of(u, struct tegra_uart_port, uport);
+}
+
+static unsigned int tegra_uart_get_mctrl(struct uart_port *u)
+{
+	struct tegra_uart_port *tup = to_tegra_uport(u);
+
+	/*
+	 * RI - Ring detector is active
+	 * CD/DCD/CAR - Carrier detect is always active. For some reason
+	 *	linux has different names for carrier detect.
+	 * DSR - Data Set ready is active as the hardware doesn't support it.
+	 *	Don't know if the linux support this yet?
+	 * CTS - Clear to send. Always set to active, as the hardware handles
+	 *	CTS automatically.
+	 */
+	if (tup->enable_modem_interrupt)
+		return TIOCM_RI | TIOCM_CD | TIOCM_DSR | TIOCM_CTS;
+	return TIOCM_CTS;
+}
+
+static void set_rts(struct tegra_uart_port *tup, bool active)
+{
+	unsigned long mcr;
+
+	mcr = tup->mcr_shadow;
+	if (active)
+		mcr |= TEGRA_UART_MCR_RTS_EN;
+	else
+		mcr &= ~TEGRA_UART_MCR_RTS_EN;
+	if (mcr != tup->mcr_shadow) {
+		tegra_uart_write(tup, mcr, UART_MCR);
+		tup->mcr_shadow = mcr;
+	}
+	return;
+}
+
+static void set_dtr(struct tegra_uart_port *tup, bool active)
+{
+	unsigned long mcr;
+
+	mcr = tup->mcr_shadow;
+	if (active)
+		mcr |= UART_MCR_DTR;
+	else
+		mcr &= ~UART_MCR_DTR;
+	if (mcr != tup->mcr_shadow) {
+		tegra_uart_write(tup, mcr, UART_MCR);
+		tup->mcr_shadow = mcr;
+	}
+	return;
+}
+
+static void tegra_uart_set_mctrl(struct uart_port *u, unsigned int mctrl)
+{
+	struct tegra_uart_port *tup = to_tegra_uport(u);
+	unsigned long mcr;
+	int dtr_enable;
+
+	mcr = tup->mcr_shadow;
+	tup->rts_active = !!(mctrl & TIOCM_RTS);
+	set_rts(tup, tup->rts_active);
+
+	dtr_enable = !!(mctrl & TIOCM_DTR);
+	set_dtr(tup, dtr_enable);
+	return;
+}
+
+static void tegra_uart_break_ctl(struct uart_port *u, int break_ctl)
+{
+	struct tegra_uart_port *tup = to_tegra_uport(u);
+	unsigned long lcr;
+
+	lcr = tup->lcr_shadow;
+	if (break_ctl)
+		lcr |= UART_LCR_SBC;
+	else
+		lcr &= ~UART_LCR_SBC;
+	tegra_uart_write(tup, lcr, UART_LCR);
+	tup->lcr_shadow = lcr;
+}
+
+/* Wait for a symbol-time. */
+static void tegra_uart_wait_sym_time(struct tegra_uart_port *tup,
+		unsigned int syms)
+{
+	if (tup->current_baud)
+		udelay(DIV_ROUND_UP(syms * tup->symb_bit * 1000000,
+			tup->current_baud));
+}
+
+static void tegra_uart_fifo_reset(struct tegra_uart_port *tup, u8 fcr_bits)
+{
+	unsigned long fcr = tup->fcr_shadow;
+
+	if (tup->cdata->allow_txfifo_reset_fifo_mode) {
+		fcr |= fcr_bits & (UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT);
+		tegra_uart_write(tup, fcr, UART_FCR);
+	} else {
+		fcr &= ~UART_FCR_ENABLE_FIFO;
+		tegra_uart_write(tup, fcr, UART_FCR);
+		udelay(60);
+		fcr |= fcr_bits & (UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT);
+		tegra_uart_write(tup, fcr, UART_FCR);
+		fcr |= UART_FCR_ENABLE_FIFO;
+		tegra_uart_write(tup, fcr, UART_FCR);
+	}
+
+	/* Dummy read to ensure the write is posted */
+	tegra_uart_read(tup, UART_SCR);
+
+	/* Wait for the flush to propagate. */
+	tegra_uart_wait_sym_time(tup, 1);
+}
+
+static int tegra_set_baudrate(struct tegra_uart_port *tup, unsigned int baud)
+{
+	unsigned long rate;
+	unsigned int divisor;
+	unsigned long lcr;
+	int ret;
+
+	if (tup->current_baud == baud)
+		return 0;
+
+	if (tup->cdata->support_clk_src_div) {
+		rate = baud * 16;
+		ret = clk_set_rate(tup->uart_clk, rate);
+		if (ret < 0) {
+			dev_err(tup->uport.dev,
+				"clk_set_rate() failed for rate %lu\n", rate);
+			return ret;
+		}
+		divisor = 1;
+	} else {
+		rate = clk_get_rate(tup->uart_clk);
+		divisor = DIV_ROUND_CLOSEST(rate, baud * 16);
+	}
+
+	lcr = tup->lcr_shadow;
+	lcr |= UART_LCR_DLAB;
+	tegra_uart_write(tup, lcr, UART_LCR);
+
+	tegra_uart_write(tup, divisor & 0xFF, UART_TX);
+	tegra_uart_write(tup, ((divisor >> 8) & 0xFF), UART_IER);
+
+	lcr &= ~UART_LCR_DLAB;
+	tegra_uart_write(tup, lcr, UART_LCR);
+
+	/* Dummy read to ensure the write is posted */
+	tegra_uart_read(tup, UART_SCR);
+
+	tup->current_baud = baud;
+
+	/* wait two character intervals at new rate */
+	tegra_uart_wait_sym_time(tup, 2);
+	return 0;
+}
+
+static char tegra_uart_decode_rx_error(struct tegra_uart_port *tup,
+			unsigned long lsr)
+{
+	char flag = TTY_NORMAL;
+
+	if (unlikely(lsr & TEGRA_UART_LSR_ANY)) {
+		if (lsr & UART_LSR_OE) {
+			/* Overrrun error */
+			flag |= TTY_OVERRUN;
+			tup->uport.icount.overrun++;
+			dev_err(tup->uport.dev, "Got overrun errors\n");
+		} else if (lsr & UART_LSR_PE) {
+			/* Parity error */
+			flag |= TTY_PARITY;
+			tup->uport.icount.parity++;
+			dev_err(tup->uport.dev, "Got Parity errors\n");
+		} else if (lsr & UART_LSR_FE) {
+			flag |= TTY_FRAME;
+			tup->uport.icount.frame++;
+			dev_err(tup->uport.dev, "Got frame errors\n");
+		} else if (lsr & UART_LSR_BI) {
+			dev_err(tup->uport.dev, "Got Break\n");
+			tup->uport.icount.brk++;
+			/* If FIFO read error without any data, reset Rx FIFO */
+			if (!(lsr & UART_LSR_DR) && (lsr & UART_LSR_FIFOE))
+				tegra_uart_fifo_reset(tup, UART_FCR_CLEAR_RCVR);
+		}
+	}
+	return flag;
+}
+
+static int tegra_uart_request_port(struct uart_port *u)
+{
+	return 0;
+}
+
+static void tegra_uart_release_port(struct uart_port *u)
+{
+	/* Nothing to do here */
+}
+
+static void tegra_uart_fill_tx_fifo(struct tegra_uart_port *tup, int max_bytes)
+{
+	struct circ_buf *xmit = &tup->uport.state->xmit;
+	int i;
+
+	for (i = 0; i < max_bytes; i++) {
+		BUG_ON(uart_circ_empty(xmit));
+		if (tup->cdata->tx_fifo_full_status) {
+			unsigned long lsr = tegra_uart_read(tup, UART_LSR);
+			if ((lsr & TEGRA_UART_LSR_TXFIFO_FULL))
+				break;
+		}
+		tegra_uart_write(tup, xmit->buf[xmit->tail], UART_TX);
+		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
+		tup->uport.icount.tx++;
+	}
+}
+
+static void tegra_uart_start_pio_tx(struct tegra_uart_port *tup,
+		unsigned int bytes)
+{
+	if (bytes > TEGRA_UART_MIN_DMA)
+		bytes = TEGRA_UART_MIN_DMA;
+
+	tup->tx_in_progress = TEGRA_UART_TX_PIO;
+	tup->tx_bytes = bytes;
+	tup->ier_shadow |= UART_IER_THRI;
+	tegra_uart_write(tup, tup->ier_shadow, UART_IER);
+}
+
+static void tegra_uart_tx_dma_complete(void *args)
+{
+	struct tegra_uart_port *tup = args;
+	struct circ_buf *xmit = &tup->uport.state->xmit;
+	struct dma_tx_state state;
+	unsigned long flags;
+	int count;
+
+	dmaengine_tx_status(tup->tx_dma_chan, tup->rx_cookie, &state);
+	count = tup->tx_bytes_requested - state.residue;
+	async_tx_ack(tup->tx_dma_desc);
+	spin_lock_irqsave(&tup->uport.lock, flags);
+	xmit->tail = (xmit->tail + count) & (UART_XMIT_SIZE - 1);
+	tup->tx_in_progress = 0;
+	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+		uart_write_wakeup(&tup->uport);
+	tegra_uart_start_next_tx(tup);
+	spin_unlock_irqrestore(&tup->uport.lock, flags);
+}
+
+static int tegra_uart_start_tx_dma(struct tegra_uart_port *tup,
+		unsigned long count)
+{
+	struct circ_buf *xmit = &tup->uport.state->xmit;
+	dma_addr_t tx_phys_addr;
+
+	dma_sync_single_for_device(tup->uport.dev, tup->tx_dma_buf_phys,
+				UART_XMIT_SIZE, DMA_TO_DEVICE);
+
+	tup->tx_bytes = count & ~(0xF);
+	tx_phys_addr = tup->tx_dma_buf_phys + xmit->tail;
+	tup->tx_dma_desc = dmaengine_prep_slave_single(tup->tx_dma_chan,
+				tx_phys_addr, tup->tx_bytes, DMA_MEM_TO_DEV,
+				DMA_PREP_INTERRUPT);
+	if (!tup->tx_dma_desc) {
+		dev_err(tup->uport.dev, "Not able to get desc for Tx\n");
+		return -EIO;
+	}
+
+	tup->tx_dma_desc->callback = tegra_uart_tx_dma_complete;
+	tup->tx_dma_desc->callback_param = tup;
+	tup->tx_in_progress = TEGRA_UART_TX_DMA;
+	tup->tx_bytes_requested = tup->tx_bytes;
+	tup->tx_cookie = dmaengine_submit(tup->tx_dma_desc);
+	dma_async_issue_pending(tup->tx_dma_chan);
+	return 0;
+}
+
+static void tegra_uart_start_next_tx(struct tegra_uart_port *tup)
+{
+	unsigned long tail;
+	unsigned long count;
+	struct circ_buf *xmit = &tup->uport.state->xmit;
+
+	tail = (unsigned long)&xmit->buf[xmit->tail];
+	count = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
+	if (!count)
+		return;
+
+	if (count < TEGRA_UART_MIN_DMA)
+		tegra_uart_start_pio_tx(tup, count);
+	else if (BYTES_TO_ALIGN(tail) > 0)
+		tegra_uart_start_pio_tx(tup, BYTES_TO_ALIGN(tail));
+	else
+		tegra_uart_start_tx_dma(tup, count);
+}
+
+/* Called by serial core driver with u->lock taken. */
+static void tegra_uart_start_tx(struct uart_port *u)
+{
+	struct tegra_uart_port *tup = to_tegra_uport(u);
+	struct circ_buf *xmit = &u->state->xmit;
+
+	if (!uart_circ_empty(xmit) && !tup->tx_in_progress)
+		tegra_uart_start_next_tx(tup);
+}
+
+static unsigned int tegra_uart_tx_empty(struct uart_port *u)
+{
+	struct tegra_uart_port *tup = to_tegra_uport(u);
+	unsigned int ret = 0;
+	unsigned long flags;
+
+	spin_lock_irqsave(&u->lock, flags);
+	if (!tup->tx_in_progress) {
+		unsigned long lsr = tegra_uart_read(tup, UART_LSR);
+		if ((lsr & TX_EMPTY_STATUS) == TX_EMPTY_STATUS)
+			ret = TIOCSER_TEMT;
+	}
+	spin_unlock_irqrestore(&u->lock, flags);
+	return ret;
+}
+
+static void tegra_uart_stop_tx(struct uart_port *u)
+{
+	struct tegra_uart_port *tup = to_tegra_uport(u);
+	struct circ_buf *xmit = &tup->uport.state->xmit;
+	struct dma_tx_state state;
+	int count;
+
+	dmaengine_terminate_all(tup->tx_dma_chan);
+	dmaengine_tx_status(tup->tx_dma_chan, tup->tx_cookie, &state);
+	count = tup->tx_bytes_requested - state.residue;
+	async_tx_ack(tup->tx_dma_desc);
+	xmit->tail = (xmit->tail + count) & (UART_XMIT_SIZE - 1);
+	tup->tx_in_progress = 0;
+	return;
+}
+
+static void tegra_uart_handle_tx_pio(struct tegra_uart_port *tup)
+{
+	struct circ_buf *xmit = &tup->uport.state->xmit;
+
+	tegra_uart_fill_tx_fifo(tup, tup->tx_bytes);
+	tup->tx_in_progress = 0;
+	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+		uart_write_wakeup(&tup->uport);
+	tegra_uart_start_next_tx(tup);
+	return;
+}
+
+static void tegra_uart_handle_rx_pio(struct tegra_uart_port *tup,
+		struct tty_struct *tty)
+{
+	do {
+		char flag = TTY_NORMAL;
+		unsigned long lsr = 0;
+		unsigned char ch;
+
+		lsr = tegra_uart_read(tup, UART_LSR);
+		if (!(lsr & UART_LSR_DR))
+			break;
+
+		flag = tegra_uart_decode_rx_error(tup, lsr);
+		ch = (unsigned char) tegra_uart_read(tup, UART_RX);
+		tup->uport.icount.rx++;
+
+		if (!uart_handle_sysrq_char(&tup->uport, ch) && tty)
+			tty_insert_flip_char(tty, ch, flag);
+	} while (1);
+
+	return;
+}
+
+static void tegra_uart_copy_rx_to_tty(struct tegra_uart_port *tup,
+		struct tty_struct *tty, int count)
+{
+	int copied;
+
+	tup->uport.icount.rx += count;
+	if (!tty) {
+		dev_err(tup->uport.dev, "No tty port\n");
+		return;
+	}
+	dma_sync_single_for_cpu(tup->uport.dev, tup->rx_dma_buf_phys,
+				TEGRA_UART_RX_DMA_BUFFER_SIZE, DMA_FROM_DEVICE);
+	copied = tty_insert_flip_string(tty,
+			((unsigned char *)(tup->rx_dma_buf_virt)), count);
+	if (copied != count) {
+		WARN_ON(1);
+		dev_err(tup->uport.dev, "RxData copy to tty layer failed\n");
+	}
+	dma_sync_single_for_device(tup->uport.dev, tup->rx_dma_buf_phys,
+				TEGRA_UART_RX_DMA_BUFFER_SIZE, DMA_TO_DEVICE);
+}
+
+static void tegra_uart_rx_dma_complete(void *args)
+{
+	struct tegra_uart_port *tup = args;
+	struct uart_port *u = &tup->uport;
+	int count = tup->rx_bytes_requested;
+	struct tty_struct *tty = tty_port_tty_get(&tup->uport.state->port);
+	unsigned long flags;
+
+	async_tx_ack(tup->rx_dma_desc);
+	spin_lock_irqsave(&u->lock, flags);
+
+	/* Deactivate flow control to stop sender */
+	if (tup->rts_active)
+		set_rts(tup, false);
+
+	/* If we are here, DMA is stopped */
+	if (count)
+		tegra_uart_copy_rx_to_tty(tup, tty, count);
+
+	tegra_uart_handle_rx_pio(tup, tty);
+	if (tty) {
+		tty_flip_buffer_push(tty);
+		tty_kref_put(tty);
+	}
+	tegra_uart_start_rx_dma(tup);
+
+	/* Activate flow control to start transfer */
+	if (tup->rts_active)
+		set_rts(tup, true);
+
+	spin_unlock_irqrestore(&u->lock, flags);
+}
+
+static void tegra_uart_handle_rx_dma(struct tegra_uart_port *tup)
+{
+	struct dma_tx_state state;
+	struct tty_struct *tty = tty_port_tty_get(&tup->uport.state->port);
+	int count;
+
+	/* Deactivate flow control to stop sender */
+	if (tup->rts_active)
+		set_rts(tup, false);
+
+	dmaengine_terminate_all(tup->rx_dma_chan);
+	dmaengine_tx_status(tup->rx_dma_chan,  tup->rx_cookie, &state);
+	count = tup->rx_bytes_requested - state.residue;
+
+	/* If we are here, DMA is stopped */
+	if (count)
+		tegra_uart_copy_rx_to_tty(tup, tty, count);
+
+	tegra_uart_handle_rx_pio(tup, tty);
+	if (tty) {
+		tty_flip_buffer_push(tty);
+		tty_kref_put(tty);
+	}
+	tegra_uart_start_rx_dma(tup);
+
+	if (tup->rts_active)
+		set_rts(tup, true);
+}
+
+static int tegra_uart_start_rx_dma(struct tegra_uart_port *tup)
+{
+	unsigned int count = TEGRA_UART_RX_DMA_BUFFER_SIZE;
+
+	tup->rx_dma_desc = dmaengine_prep_slave_single(tup->rx_dma_chan,
+				tup->rx_dma_buf_phys, count, DMA_DEV_TO_MEM,
+				DMA_PREP_INTERRUPT);
+	if (!tup->rx_dma_desc) {
+		dev_err(tup->uport.dev, "Not able to get desc for Rx\n");
+		return -EIO;
+	}
+
+	tup->rx_dma_desc->callback = tegra_uart_rx_dma_complete;
+	tup->rx_dma_desc->callback_param = tup;
+	dma_sync_single_for_device(tup->uport.dev, tup->rx_dma_buf_phys,
+				count, DMA_TO_DEVICE);
+	tup->rx_bytes_requested = count;
+	tup->rx_cookie = dmaengine_submit(tup->rx_dma_desc);
+	dma_async_issue_pending(tup->rx_dma_chan);
+	return 0;
+}
+
+static void tegra_uart_handle_modem_signal_change(struct uart_port *u)
+{
+	struct tegra_uart_port *tup = to_tegra_uport(u);
+	unsigned long msr;
+
+	msr = tegra_uart_read(tup, UART_MSR);
+	if (!(msr & UART_MSR_ANY_DELTA))
+		return;
+
+	if (msr & UART_MSR_TERI)
+		tup->uport.icount.rng++;
+	if (msr & UART_MSR_DDSR)
+		tup->uport.icount.dsr++;
+	/* We may only get DDCD when HW init and reset */
+	if (msr & UART_MSR_DDCD)
+		uart_handle_dcd_change(&tup->uport, msr & UART_MSR_DCD);
+	/* Will start/stop_tx accordingly */
+	if (msr & UART_MSR_DCTS)
+		uart_handle_cts_change(&tup->uport, msr & UART_MSR_CTS);
+	return;
+}
+
+static irqreturn_t tegra_uart_isr(int irq, void *data)
+{
+	struct tegra_uart_port *tup = data;
+	struct uart_port *u = &tup->uport;
+	unsigned long iir;
+	unsigned long ier;
+	bool is_rx_int = false;
+	unsigned long flags;
+
+	spin_lock_irqsave(&u->lock, flags);
+	while (1) {
+		iir = tegra_uart_read(tup, UART_IIR);
+		if (iir & UART_IIR_NO_INT) {
+			if (is_rx_int) {
+				tegra_uart_handle_rx_dma(tup);
+				if (tup->rx_in_progress) {
+					ier = tup->ier_shadow;
+					ier |= (UART_IER_RLSI | UART_IER_RTOIE |
+						TEGRA_UART_IER_EORD);
+					tup->ier_shadow = ier;
+					tegra_uart_write(tup, ier, UART_IER);
+				}
+			}
+			spin_unlock_irqrestore(&u->lock, flags);
+			return IRQ_HANDLED;
+		}
+
+		switch ((iir >> 1) & 0x7) {
+		case 0: /* Modem signal change interrupt */
+			tegra_uart_handle_modem_signal_change(u);
+			break;
+
+		case 1: /* Transmit interrupt only triggered when using PIO */
+			tup->ier_shadow &= ~UART_IER_THRI;
+			tegra_uart_write(tup, tup->ier_shadow, UART_IER);
+			tegra_uart_handle_tx_pio(tup);
+			break;
+
+		case 4: /* End of data */
+		case 6: /* Rx timeout */
+		case 2: /* Receive */
+			if (!is_rx_int) {
+				is_rx_int = true;
+				/* Disable Rx interrupts */
+				ier = tup->ier_shadow;
+				ier |= UART_IER_RDI;
+				tegra_uart_write(tup, ier, UART_IER);
+				ier &= ~(UART_IER_RDI | UART_IER_RLSI |
+					UART_IER_RTOIE | TEGRA_UART_IER_EORD);
+				tup->ier_shadow = ier;
+				tegra_uart_write(tup, ier, UART_IER);
+			}
+			break;
+
+		case 3: /* Receive error */
+			tegra_uart_decode_rx_error(tup,
+					tegra_uart_read(tup, UART_LSR));
+			break;
+
+		case 5: /* break nothing to handle */
+		case 7: /* break nothing to handle */
+			break;
+		}
+	}
+}
+
+static void tegra_uart_stop_rx(struct uart_port *u)
+{
+	struct tegra_uart_port *tup = to_tegra_uport(u);
+	struct tty_struct *tty = tty_port_tty_get(&tup->uport.state->port);
+	struct dma_tx_state state;
+	unsigned long ier;
+	int count;
+
+	if (tup->rts_active)
+		set_rts(tup, false);
+
+	if (!tup->rx_in_progress)
+		return;
+
+	tegra_uart_wait_sym_time(tup, 1); /* wait a character interval */
+
+	ier = tup->ier_shadow;
+	ier &= ~(UART_IER_RDI | UART_IER_RLSI | UART_IER_RTOIE |
+					TEGRA_UART_IER_EORD);
+	tup->ier_shadow = ier;
+	tegra_uart_write(tup, ier, UART_IER);
+	tup->rx_in_progress = 0;
+	if (tup->rx_dma_chan) {
+		dmaengine_terminate_all(tup->rx_dma_chan);
+		dmaengine_tx_status(tup->rx_dma_chan, tup->rx_cookie, &state);
+		async_tx_ack(tup->rx_dma_desc);
+		count = tup->rx_bytes_requested - state.residue;
+		tegra_uart_copy_rx_to_tty(tup, tty, count);
+		tegra_uart_handle_rx_pio(tup, tty);
+	} else {
+		tegra_uart_handle_rx_pio(tup, tty);
+	}
+	if (tty) {
+		tty_flip_buffer_push(tty);
+		tty_kref_put(tty);
+	}
+	return;
+}
+
+static void tegra_uart_hw_deinit(struct tegra_uart_port *tup)
+{
+	unsigned long flags;
+	unsigned long char_time = DIV_ROUND_UP(10000000, tup->current_baud);
+	unsigned long fifo_empty_time = tup->uport.fifosize * char_time;
+	unsigned long wait_time;
+	unsigned long lsr;
+	unsigned long msr;
+	unsigned long mcr;
+
+	/* Disable interrupts */
+	tegra_uart_write(tup, 0, UART_IER);
+
+	lsr = tegra_uart_read(tup, UART_LSR);
+	if ((lsr & UART_LSR_TEMT) != UART_LSR_TEMT) {
+		msr = tegra_uart_read(tup, UART_MSR);
+		mcr = tegra_uart_read(tup, UART_MCR);
+		if ((mcr & TEGRA_UART_MCR_CTS_EN) && (msr & UART_MSR_CTS))
+			dev_err(tup->uport.dev,
+				"Tx Fifo not empty, CTS disabled, waiting\n");
+
+		/* Wait for Tx fifo to be empty */
+		while ((lsr & UART_LSR_TEMT) != UART_LSR_TEMT) {
+			wait_time = min(fifo_empty_time, 100lu);
+			udelay(wait_time);
+			fifo_empty_time -= wait_time;
+			if (!fifo_empty_time) {
+				msr = tegra_uart_read(tup, UART_MSR);
+				mcr = tegra_uart_read(tup, UART_MCR);
+				if ((mcr & TEGRA_UART_MCR_CTS_EN) &&
+					(msr & UART_MSR_CTS))
+					dev_err(tup->uport.dev,
+						"Slave not ready\n");
+				break;
+			}
+			lsr = tegra_uart_read(tup, UART_LSR);
+		}
+	}
+
+	spin_lock_irqsave(&tup->uport.lock, flags);
+	/* Reset the Rx and Tx FIFOs */
+	tegra_uart_fifo_reset(tup, UART_FCR_CLEAR_XMIT | UART_FCR_CLEAR_RCVR);
+	tup->current_baud = 0;
+	spin_unlock_irqrestore(&tup->uport.lock, flags);
+
+	clk_disable_unprepare(tup->uart_clk);
+}
+
+static int tegra_uart_hw_init(struct tegra_uart_port *tup)
+{
+	int ret;
+
+	tup->fcr_shadow = 0;
+	tup->mcr_shadow = 0;
+	tup->lcr_shadow = 0;
+	tup->ier_shadow = 0;
+	tup->current_baud = 0;
+
+	clk_prepare_enable(tup->uart_clk);
+
+	/* Reset the UART controller to clear all previous status.*/
+	tegra_periph_reset_assert(tup->uart_clk);
+	udelay(10);
+	tegra_periph_reset_deassert(tup->uart_clk);
+
+	tup->rx_in_progress = 0;
+	tup->tx_in_progress = 0;
+
+	/*
+	 * Set the trigger level
+	 *
+	 * For PIO mode:
+	 *
+	 * For receive, this will interrupt the CPU after that many number of
+	 * bytes are received, for the remaining bytes the receive timeout
+	 * interrupt is received. Rx high watermark is set to 4.
+	 *
+	 * For transmit, if the trasnmit interrupt is enabled, this will
+	 * interrupt the CPU when the number of entries in the FIFO reaches the
+	 * low watermark. Tx low watermark is set to 16 bytes.
+	 *
+	 * For DMA mode:
+	 *
+	 * Set the Tx trigger to 16. This should match the DMA burst size that
+	 * programmed in the DMA registers.
+	 */
+	tup->fcr_shadow = UART_FCR_ENABLE_FIFO;
+	tup->fcr_shadow |= UART_FCR_R_TRIG_01;
+	tup->fcr_shadow |= TEGRA_UART_TX_TRIG_16B;
+	tegra_uart_write(tup, tup->fcr_shadow, UART_FCR);
+
+	/*
+	 * Initialize the UART with default configuration
+	 * (115200, N, 8, 1) so that the receive DMA buffer may be
+	 * enqueued
+	 */
+	tup->lcr_shadow = TEGRA_UART_DEFAULT_LSR;
+	tegra_set_baudrate(tup, TEGRA_UART_DEFAULT_BAUD);
+	tup->fcr_shadow |= UART_FCR_DMA_SELECT;
+	tegra_uart_write(tup, tup->fcr_shadow, UART_FCR);
+
+	ret = tegra_uart_start_rx_dma(tup);
+	if (ret < 0) {
+		dev_err(tup->uport.dev, "Not able to start Rx DMA\n");
+		return ret;
+	}
+	tup->rx_in_progress = 1;
+
+	/*
+	 * Enable IE_RXS for the receive status interrupts like line errros.
+	 * Enable IE_RX_TIMEOUT to get the bytes which cannot be DMA'd.
+	 *
+	 * If using DMA mode, enable EORD instead of receive interrupt which
+	 * will interrupt after the UART is done with the receive instead of
+	 * the interrupt when the FIFO "threshold" is reached.
+	 *
+	 * EORD is different interrupt than RX_TIMEOUT - RX_TIMEOUT occurs when
+	 * the DATA is sitting in the FIFO and couldn't be transferred to the
+	 * DMA as the DMA size alignment(4 bytes) is not met. EORD will be
+	 * triggered when there is a pause of the incomming data stream for 4
+	 * characters long.
+	 *
+	 * For pauses in the data which is not aligned to 4 bytes, we get
+	 * both the EORD as well as RX_TIMEOUT - SW sees RX_TIMEOUT first
+	 * then the EORD.
+	 */
+	tup->ier_shadow = UART_IER_RLSI | UART_IER_RTOIE | TEGRA_UART_IER_EORD;
+	tegra_uart_write(tup, tup->ier_shadow, UART_IER);
+	return 0;
+}
+
+static int tegra_uart_dma_channel_allocate(struct tegra_uart_port *tup,
+			bool dma_to_memory)
+{
+	struct dma_chan *dma_chan;
+	unsigned char *dma_buf;
+	dma_addr_t dma_phys;
+	int ret;
+	struct dma_slave_config dma_sconfig;
+	dma_cap_mask_t mask;
+
+	dma_cap_zero(mask);
+	dma_cap_set(DMA_SLAVE, mask);
+	dma_chan = dma_request_channel(mask, NULL, NULL);
+	if (!dma_chan) {
+		dev_err(tup->uport.dev,
+			"Dma channel is not available, will try later\n");
+		return -EPROBE_DEFER;
+	}
+
+	if (dma_to_memory) {
+		dma_buf = dma_alloc_coherent(tup->uport.dev,
+				TEGRA_UART_RX_DMA_BUFFER_SIZE,
+				 &dma_phys, GFP_KERNEL);
+		if (!dma_buf) {
+			dev_err(tup->uport.dev,
+				"Not able to allocate the dma buffer\n");
+			dma_release_channel(dma_chan);
+			return -ENOMEM;
+		}
+	} else {
+		dma_phys = dma_map_single(tup->uport.dev,
+			tup->uport.state->xmit.buf, UART_XMIT_SIZE,
+			DMA_TO_DEVICE);
+		dma_buf = tup->uport.state->xmit.buf;
+	}
+
+	dma_sconfig.slave_id = tup->dma_req_sel;
+	if (dma_to_memory) {
+		dma_sconfig.src_addr = tup->uport.mapbase;
+		dma_sconfig.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+		dma_sconfig.src_maxburst = 4;
+	} else {
+		dma_sconfig.dst_addr = tup->uport.mapbase;
+		dma_sconfig.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+		dma_sconfig.dst_maxburst = 16;
+	}
+
+	ret = dmaengine_slave_config(dma_chan, &dma_sconfig);
+	if (ret < 0) {
+		dev_err(tup->uport.dev,
+			"Dma slave config failed, err = %d\n", ret);
+		goto scrub;
+	}
+
+	if (dma_to_memory) {
+		tup->rx_dma_chan = dma_chan;
+		tup->rx_dma_buf_virt = dma_buf;
+		tup->rx_dma_buf_phys = dma_phys;
+	} else {
+		tup->tx_dma_chan = dma_chan;
+		tup->tx_dma_buf_virt = dma_buf;
+		tup->tx_dma_buf_phys = dma_phys;
+	}
+	return 0;
+
+scrub:
+	dma_release_channel(dma_chan);
+	return ret;
+}
+
+static void tegra_uart_dma_channel_free(struct tegra_uart_port *tup,
+		bool dma_to_memory)
+{
+	struct dma_chan *dma_chan;
+
+	if (dma_to_memory) {
+		dma_free_coherent(tup->uport.dev, TEGRA_UART_RX_DMA_BUFFER_SIZE,
+				tup->rx_dma_buf_virt, tup->rx_dma_buf_phys);
+		dma_chan = tup->rx_dma_chan;
+		tup->rx_dma_chan = NULL;
+		tup->rx_dma_buf_phys = 0;
+		tup->rx_dma_buf_virt = NULL;
+	} else {
+		dma_unmap_single(tup->uport.dev, tup->tx_dma_buf_phys,
+			UART_XMIT_SIZE, DMA_TO_DEVICE);
+		dma_chan = tup->tx_dma_chan;
+		tup->tx_dma_chan = NULL;
+		tup->tx_dma_buf_phys = 0;
+		tup->tx_dma_buf_virt = NULL;
+	}
+	dma_release_channel(dma_chan);
+}
+
+static int tegra_uart_startup(struct uart_port *u)
+{
+	struct tegra_uart_port *tup = to_tegra_uport(u);
+	int ret;
+
+	ret = tegra_uart_dma_channel_allocate(tup, false);
+	if (ret < 0) {
+		dev_err(u->dev, "Tx Dma allocation failed, err = %d\n", ret);
+		return ret;
+	}
+
+	ret = tegra_uart_dma_channel_allocate(tup, true);
+	if (ret < 0) {
+		dev_err(u->dev, "Rx Dma allocation failed, err = %d\n", ret);
+		goto fail_rx_dma;
+	}
+
+	ret = tegra_uart_hw_init(tup);
+	if (ret < 0) {
+		dev_err(u->dev, "Uart HW init failed, err = %d\n", ret);
+		goto fail_hw_init;
+	}
+
+	ret = request_irq(u->irq, tegra_uart_isr, IRQF_DISABLED,
+				dev_name(u->dev), tup);
+	if (ret < 0) {
+		dev_err(u->dev, "Failed to register ISR for IRQ %d\n", u->irq);
+		goto fail_hw_init;
+	}
+	return 0;
+
+fail_hw_init:
+	tegra_uart_dma_channel_free(tup, true);
+fail_rx_dma:
+	tegra_uart_dma_channel_free(tup, false);
+	return ret;
+}
+
+static void tegra_uart_shutdown(struct uart_port *u)
+{
+	struct tegra_uart_port *tup = to_tegra_uport(u);
+
+	tegra_uart_hw_deinit(tup);
+
+	tup->rx_in_progress = 0;
+	tup->tx_in_progress = 0;
+
+	tegra_uart_dma_channel_free(tup, true);
+	tegra_uart_dma_channel_free(tup, false);
+	free_irq(u->irq, tup);
+}
+
+static void tegra_uart_enable_ms(struct uart_port *u)
+{
+	struct tegra_uart_port *tup = to_tegra_uport(u);
+
+	if (tup->enable_modem_interrupt) {
+		tup->ier_shadow |= UART_IER_MSI;
+		tegra_uart_write(tup, tup->ier_shadow, UART_IER);
+	}
+}
+
+static void tegra_uart_set_termios(struct uart_port *u,
+		struct ktermios *termios, struct ktermios *oldtermios)
+{
+	struct tegra_uart_port *tup = to_tegra_uport(u);
+	unsigned int baud;
+	unsigned long flags;
+	unsigned int lcr;
+	int symb_bit = 1;
+	struct clk *parent_clk = clk_get_parent(tup->uart_clk);
+	unsigned long parent_clk_rate = clk_get_rate(parent_clk);
+	int max_divider = (tup->cdata->support_clk_src_div) ? 0x7FFF : 0xFFFF;
+
+	max_divider *= 16;
+	spin_lock_irqsave(&u->lock, flags);
+
+	/* Changing configuration, it is safe to stop any rx now */
+	if (tup->rts_active)
+		set_rts(tup, false);
+
+	/* Clear all interrupts as configuration is going to be change */
+	tegra_uart_write(tup, tup->ier_shadow | UART_IER_RDI, UART_IER);
+	tegra_uart_read(tup, UART_IER);
+	tegra_uart_write(tup, 0, UART_IER);
+	tegra_uart_read(tup, UART_IER);
+
+	/* Parity */
+	lcr = tup->lcr_shadow;
+	lcr &= ~UART_LCR_PARITY;
+
+	/* CMSPAR isn't supported by this driver */
+	termios->c_cflag &= ~CMSPAR;
+
+	if ((termios->c_cflag & PARENB) == PARENB) {
+		symb_bit++;
+		if (termios->c_cflag & PARODD) {
+			lcr |= UART_LCR_PARITY;
+			lcr &= ~UART_LCR_EPAR;
+			lcr &= ~UART_LCR_SPAR;
+		} else {
+			lcr |= UART_LCR_PARITY;
+			lcr |= UART_LCR_EPAR;
+			lcr &= ~UART_LCR_SPAR;
+		}
+	}
+
+	lcr &= ~UART_LCR_WLEN8;
+	switch (termios->c_cflag & CSIZE) {
+	case CS5:
+		lcr |= UART_LCR_WLEN5;
+		symb_bit += 5;
+		break;
+	case CS6:
+		lcr |= UART_LCR_WLEN6;
+		symb_bit += 6;
+		break;
+	case CS7:
+		lcr |= UART_LCR_WLEN7;
+		symb_bit += 7;
+		break;
+	default:
+		lcr |= UART_LCR_WLEN8;
+		symb_bit += 8;
+		break;
+	}
+
+	/* Stop bits */
+	if (termios->c_cflag & CSTOPB) {
+		lcr |= UART_LCR_STOP;
+		symb_bit += 2;
+	} else {
+		lcr &= ~UART_LCR_STOP;
+		symb_bit++;
+	}
+
+	tegra_uart_write(tup, lcr, UART_LCR);
+	tup->lcr_shadow = lcr;
+	tup->symb_bit = symb_bit;
+
+	/* Baud rate. */
+	baud = uart_get_baud_rate(u, termios, oldtermios,
+			parent_clk_rate/max_divider,
+			parent_clk_rate/16);
+	spin_unlock_irqrestore(&u->lock, flags);
+	tegra_set_baudrate(tup, baud);
+	if (tty_termios_baud_rate(termios))
+		tty_termios_encode_baud_rate(termios, baud, baud);
+	spin_lock_irqsave(&u->lock, flags);
+
+	/* Flow control */
+	if (termios->c_cflag & CRTSCTS)	{
+		tup->mcr_shadow |= TEGRA_UART_MCR_CTS_EN;
+		tup->mcr_shadow &= ~TEGRA_UART_MCR_RTS_EN;
+		tegra_uart_write(tup, tup->mcr_shadow, UART_MCR);
+		/* if top layer has asked to set rts active then do so here */
+		if (tup->rts_active)
+			set_rts(tup, true);
+	} else {
+		tup->mcr_shadow &= ~TEGRA_UART_MCR_CTS_EN;
+		tup->mcr_shadow &= ~TEGRA_UART_MCR_RTS_EN;
+		tegra_uart_write(tup, tup->mcr_shadow, UART_MCR);
+	}
+
+	/* update the port timeout based on new settings */
+	uart_update_timeout(u, termios->c_cflag, baud);
+
+	/* Make sure all write has completed */
+	tegra_uart_read(tup, UART_IER);
+
+	/* Reenable interrupt */
+	tegra_uart_write(tup, tup->ier_shadow, UART_IER);
+	tegra_uart_read(tup, UART_IER);
+
+	spin_unlock_irqrestore(&u->lock, flags);
+	return;
+}
+
+/*
+ * Flush any TX data submitted for DMA and PIO. Called when the
+ * TX circular buffer is reset.
+ */
+static void tegra_uart_flush_buffer(struct uart_port *u)
+{
+	struct tegra_uart_port *tup = to_tegra_uport(u);
+
+	tup->tx_bytes = 0;
+	if (tup->tx_dma_chan)
+		dmaengine_terminate_all(tup->tx_dma_chan);
+	return;
+}
+
+static const char *tegra_uart_type(struct uart_port *u)
+{
+	return TEGRA_UART_TYPE;
+}
+
+static struct uart_ops tegra_uart_ops = {
+	.tx_empty	= tegra_uart_tx_empty,
+	.set_mctrl	= tegra_uart_set_mctrl,
+	.get_mctrl	= tegra_uart_get_mctrl,
+	.stop_tx	= tegra_uart_stop_tx,
+	.start_tx	= tegra_uart_start_tx,
+	.stop_rx	= tegra_uart_stop_rx,
+	.flush_buffer	= tegra_uart_flush_buffer,
+	.enable_ms	= tegra_uart_enable_ms,
+	.break_ctl	= tegra_uart_break_ctl,
+	.startup	= tegra_uart_startup,
+	.shutdown	= tegra_uart_shutdown,
+	.set_termios	= tegra_uart_set_termios,
+	.type		= tegra_uart_type,
+	.request_port	= tegra_uart_request_port,
+	.release_port	= tegra_uart_release_port,
+};
+
+static struct uart_driver tegra_uart_driver = {
+	.owner		= THIS_MODULE,
+	.driver_name	= "tegra_hsuart",
+	.dev_name	= "ttyTHS",
+	.cons		= 0,
+	.nr		= TEGRA_UART_MAXIMUM,
+};
+
+static int tegra_uart_parse_dt(struct platform_device *pdev,
+	struct tegra_uart_port *tup)
+{
+	struct device_node *np = pdev->dev.of_node;
+	u32 of_dma[2];
+	int port;
+
+	if (of_property_read_u32_array(np, "nvidia,dma-request-selector",
+				of_dma, 2) >= 0) {
+		tup->dma_req_sel = of_dma[1];
+	} else {
+		dev_err(&pdev->dev, "missing dma requestor in device tree\n");
+		return -EINVAL;
+	}
+
+	port = of_alias_get_id(np, "serial");
+	if (port < 0) {
+		dev_err(&pdev->dev, "failed to get alias id, errno %d\n", port);
+		return port;
+	}
+	tup->uport.line = port;
+
+	tup->enable_modem_interrupt = of_property_read_bool(np,
+					"nvidia,enable-modem-interrupt");
+	return 0;
+}
+
+struct tegra_uart_chip_data tegra20_uart_chip_data = {
+	.tx_fifo_full_status		= false,
+	.allow_txfifo_reset_fifo_mode	= true,
+	.support_clk_src_div		= false,
+};
+
+struct tegra_uart_chip_data tegra30_uart_chip_data = {
+	.tx_fifo_full_status		= true,
+	.allow_txfifo_reset_fifo_mode	= false,
+	.support_clk_src_div		= true,
+};
+
+static struct of_device_id tegra_uart_of_match[] = {
+	{
+		.compatible	= "nvidia,tegra30-hsuart",
+		.data		= &tegra30_uart_chip_data,
+	}, {
+		.compatible	= "nvidia,tegra20-hsuart",
+		.data		= &tegra20_uart_chip_data,
+	}, {
+	},
+};
+MODULE_DEVICE_TABLE(of, tegra_uart_of_match);
+
+static int tegra_uart_probe(struct platform_device *pdev)
+{
+	struct tegra_uart_port *tup;
+	struct uart_port *u;
+	struct resource *resource;
+	int ret;
+	const struct tegra_uart_chip_data *cdata;
+	const struct of_device_id *match;
+
+	match = of_match_device(of_match_ptr(tegra_uart_of_match),
+				&pdev->dev);
+	if (!match) {
+		dev_err(&pdev->dev, "Error: No device match found\n");
+		return -ENODEV;
+	}
+	cdata = match->data;
+
+	tup = devm_kzalloc(&pdev->dev, sizeof(*tup), GFP_KERNEL);
+	if (!tup) {
+		dev_err(&pdev->dev, "Failed to allocate memory for tup\n");
+		return -ENOMEM;
+	}
+
+	ret = tegra_uart_parse_dt(pdev, tup);
+	if (ret < 0)
+		return ret;
+
+	u = &tup->uport;
+	u->dev = &pdev->dev;
+	u->ops = &tegra_uart_ops;
+	u->type = PORT_TEGRA;
+	u->fifosize = 32;
+	tup->cdata = cdata;
+
+	platform_set_drvdata(pdev, tup);
+	resource = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!resource) {
+		dev_err(&pdev->dev, "No IO memory resource\n");
+		return -ENODEV;
+	}
+
+	u->mapbase = resource->start;
+	u->membase = devm_request_and_ioremap(&pdev->dev, resource);
+	if (!u->membase) {
+		dev_err(&pdev->dev, "memregion/iomap address req failed\n");
+		return -EADDRNOTAVAIL;
+	}
+
+	tup->uart_clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(tup->uart_clk)) {
+		dev_err(&pdev->dev, "Couldn't get the clock\n");
+		return PTR_ERR(tup->uart_clk);
+	}
+
+	u->iotype = UPIO_MEM32;
+	u->irq = platform_get_irq(pdev, 0);
+	u->regshift = 2;
+	ret = uart_add_one_port(&tegra_uart_driver, u);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "Failed to add uart port, err %d\n", ret);
+		return ret;
+	}
+	return ret;
+}
+
+static int tegra_uart_remove(struct platform_device *pdev)
+{
+	struct tegra_uart_port *tup = platform_get_drvdata(pdev);
+	struct uart_port *u = &tup->uport;
+
+	uart_remove_one_port(&tegra_uart_driver, u);
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int tegra_uart_suspend(struct device *dev)
+{
+	struct tegra_uart_port *tup = dev_get_drvdata(dev);
+	struct uart_port *u = &tup->uport;
+
+	return uart_suspend_port(&tegra_uart_driver, u);
+}
+
+static int tegra_uart_resume(struct device *dev)
+{
+	struct tegra_uart_port *tup = dev_get_drvdata(dev);
+	struct uart_port *u = &tup->uport;
+
+	return uart_resume_port(&tegra_uart_driver, u);
+}
+#endif
+
+static const struct dev_pm_ops tegra_uart_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(tegra_uart_suspend, tegra_uart_resume)
+};
+
+static struct platform_driver tegra_uart_platform_driver = {
+	.probe		= tegra_uart_probe,
+	.remove		= tegra_uart_remove,
+	.driver		= {
+		.name	= "serial-tegra",
+		.of_match_table = of_match_ptr(tegra_uart_of_match),
+		.pm	= &tegra_uart_pm_ops,
+	},
+};
+
+static int __init tegra_uart_init(void)
+{
+	int ret;
+
+	ret = uart_register_driver(&tegra_uart_driver);
+	if (ret < 0) {
+		pr_err("Could not register %s driver\n",
+			tegra_uart_driver.driver_name);
+		return ret;
+	}
+
+	ret = platform_driver_register(&tegra_uart_platform_driver);
+	if (ret < 0) {
+		pr_err("Uart platfrom driver register failed, e = %d\n", ret);
+		uart_unregister_driver(&tegra_uart_driver);
+		return ret;
+	}
+	return 0;
+}
+
+static void __exit tegra_uart_exit(void)
+{
+	pr_info("Unloading tegra uart driver\n");
+	platform_driver_unregister(&tegra_uart_platform_driver);
+	uart_unregister_driver(&tegra_uart_driver);
+}
+
+module_init(tegra_uart_init);
+module_exit(tegra_uart_exit);
+
+MODULE_ALIAS("platform:serial-tegra");
+MODULE_DESCRIPTION("High speed UART driver for tegra chipset");
+MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
+MODULE_LICENSE("GPL v2");