linux-arkmicro/linux/drivers/tty/serial/msm_serial.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Driver for msm7k serial device and console
 *
 * Copyright (C) 2007 Google, Inc.
 * Author: Robert Love <rlove@google.com>
 * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
 */

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

#include <linux/kernel.h>
#include <linux/atomic.h>
#include <linux/dma-mapping.h>
#include <linux/dmaengine.h>
#include <linux/module.h>
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/serial_core.h>
#include <linux/slab.h>
#include <linux/clk.h>
#include <linux/platform_device.h>
#include <linux/delay.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/wait.h>

#define UART_MR1			0x0000

#define UART_MR1_AUTO_RFR_LEVEL0	0x3F
#define UART_MR1_AUTO_RFR_LEVEL1	0x3FF00
#define UART_DM_MR1_AUTO_RFR_LEVEL1	0xFFFFFF00
#define UART_MR1_RX_RDY_CTL		BIT(7)
#define UART_MR1_CTS_CTL		BIT(6)

#define UART_MR2			0x0004
#define UART_MR2_ERROR_MODE		BIT(6)
#define UART_MR2_BITS_PER_CHAR		0x30
#define UART_MR2_BITS_PER_CHAR_5	(0x0 << 4)
#define UART_MR2_BITS_PER_CHAR_6	(0x1 << 4)
#define UART_MR2_BITS_PER_CHAR_7	(0x2 << 4)
#define UART_MR2_BITS_PER_CHAR_8	(0x3 << 4)
#define UART_MR2_STOP_BIT_LEN_ONE	(0x1 << 2)
#define UART_MR2_STOP_BIT_LEN_TWO	(0x3 << 2)
#define UART_MR2_PARITY_MODE_NONE	0x0
#define UART_MR2_PARITY_MODE_ODD	0x1
#define UART_MR2_PARITY_MODE_EVEN	0x2
#define UART_MR2_PARITY_MODE_SPACE	0x3
#define UART_MR2_PARITY_MODE		0x3

#define UART_CSR			0x0008

#define UART_TF				0x000C
#define UARTDM_TF			0x0070

#define UART_CR				0x0010
#define UART_CR_CMD_NULL		(0 << 4)
#define UART_CR_CMD_RESET_RX		(1 << 4)
#define UART_CR_CMD_RESET_TX		(2 << 4)
#define UART_CR_CMD_RESET_ERR		(3 << 4)
#define UART_CR_CMD_RESET_BREAK_INT	(4 << 4)
#define UART_CR_CMD_START_BREAK		(5 << 4)
#define UART_CR_CMD_STOP_BREAK		(6 << 4)
#define UART_CR_CMD_RESET_CTS		(7 << 4)
#define UART_CR_CMD_RESET_STALE_INT	(8 << 4)
#define UART_CR_CMD_PACKET_MODE		(9 << 4)
#define UART_CR_CMD_MODE_RESET		(12 << 4)
#define UART_CR_CMD_SET_RFR		(13 << 4)
#define UART_CR_CMD_RESET_RFR		(14 << 4)
#define UART_CR_CMD_PROTECTION_EN	(16 << 4)
#define UART_CR_CMD_STALE_EVENT_DISABLE	(6 << 8)
#define UART_CR_CMD_STALE_EVENT_ENABLE	(80 << 4)
#define UART_CR_CMD_FORCE_STALE		(4 << 8)
#define UART_CR_CMD_RESET_TX_READY	(3 << 8)
#define UART_CR_TX_DISABLE		BIT(3)
#define UART_CR_TX_ENABLE		BIT(2)
#define UART_CR_RX_DISABLE		BIT(1)
#define UART_CR_RX_ENABLE		BIT(0)
#define UART_CR_CMD_RESET_RXBREAK_START	((1 << 11) | (2 << 4))

#define UART_IMR			0x0014
#define UART_IMR_TXLEV			BIT(0)
#define UART_IMR_RXSTALE		BIT(3)
#define UART_IMR_RXLEV			BIT(4)
#define UART_IMR_DELTA_CTS		BIT(5)
#define UART_IMR_CURRENT_CTS		BIT(6)
#define UART_IMR_RXBREAK_START		BIT(10)

#define UART_IPR_RXSTALE_LAST		0x20
#define UART_IPR_STALE_LSB		0x1F
#define UART_IPR_STALE_TIMEOUT_MSB	0x3FF80
#define UART_DM_IPR_STALE_TIMEOUT_MSB	0xFFFFFF80

#define UART_IPR			0x0018
#define UART_TFWR			0x001C
#define UART_RFWR			0x0020
#define UART_HCR			0x0024

#define UART_MREG			0x0028
#define UART_NREG			0x002C
#define UART_DREG			0x0030
#define UART_MNDREG			0x0034
#define UART_IRDA			0x0038
#define UART_MISR_MODE			0x0040
#define UART_MISR_RESET			0x0044
#define UART_MISR_EXPORT		0x0048
#define UART_MISR_VAL			0x004C
#define UART_TEST_CTRL			0x0050

#define UART_SR				0x0008
#define UART_SR_HUNT_CHAR		BIT(7)
#define UART_SR_RX_BREAK		BIT(6)
#define UART_SR_PAR_FRAME_ERR		BIT(5)
#define UART_SR_OVERRUN			BIT(4)
#define UART_SR_TX_EMPTY		BIT(3)
#define UART_SR_TX_READY		BIT(2)
#define UART_SR_RX_FULL			BIT(1)
#define UART_SR_RX_READY		BIT(0)

#define UART_RF				0x000C
#define UARTDM_RF			0x0070
#define UART_MISR			0x0010
#define UART_ISR			0x0014
#define UART_ISR_TX_READY		BIT(7)

#define UARTDM_RXFS			0x50
#define UARTDM_RXFS_BUF_SHIFT		0x7
#define UARTDM_RXFS_BUF_MASK		0x7

#define UARTDM_DMEN			0x3C
#define UARTDM_DMEN_RX_SC_ENABLE	BIT(5)
#define UARTDM_DMEN_TX_SC_ENABLE	BIT(4)

#define UARTDM_DMEN_TX_BAM_ENABLE	BIT(2)	/* UARTDM_1P4 */
#define UARTDM_DMEN_TX_DM_ENABLE	BIT(0)	/* < UARTDM_1P4 */

#define UARTDM_DMEN_RX_BAM_ENABLE	BIT(3)	/* UARTDM_1P4 */
#define UARTDM_DMEN_RX_DM_ENABLE	BIT(1)	/* < UARTDM_1P4 */

#define UARTDM_DMRX			0x34
#define UARTDM_NCF_TX			0x40
#define UARTDM_RX_TOTAL_SNAP		0x38

#define UARTDM_BURST_SIZE		16   /* in bytes */
#define UARTDM_TX_AIGN(x)		((x) & ~0x3) /* valid for > 1p3 */
#define UARTDM_TX_MAX			256   /* in bytes, valid for <= 1p3 */
#define UARTDM_RX_SIZE			(UART_XMIT_SIZE / 4)

enum {
	UARTDM_1P1 = 1,
	UARTDM_1P2,
	UARTDM_1P3,
	UARTDM_1P4,
};

struct msm_dma {
	struct dma_chan		*chan;
	enum dma_data_direction dir;
	dma_addr_t		phys;
	unsigned char		*virt;
	dma_cookie_t		cookie;
	u32			enable_bit;
	unsigned int		count;
	struct dma_async_tx_descriptor	*desc;
};

struct msm_port {
	struct uart_port	uart;
	char			name[16];
	struct clk		*clk;
	struct clk		*pclk;
	unsigned int		imr;
	int			is_uartdm;
	unsigned int		old_snap_state;
	bool			break_detected;
	struct msm_dma		tx_dma;
	struct msm_dma		rx_dma;
};

#define UART_TO_MSM(uart_port)	container_of(uart_port, struct msm_port, uart)

static
void msm_write(struct uart_port *port, unsigned int val, unsigned int off)
{
	writel_relaxed(val, port->membase + off);
}

static
unsigned int msm_read(struct uart_port *port, unsigned int off)
{
	return readl_relaxed(port->membase + off);
}

/*
 * Setup the MND registers to use the TCXO clock.
 */
static void msm_serial_set_mnd_regs_tcxo(struct uart_port *port)
{
	msm_write(port, 0x06, UART_MREG);
	msm_write(port, 0xF1, UART_NREG);
	msm_write(port, 0x0F, UART_DREG);
	msm_write(port, 0x1A, UART_MNDREG);
	port->uartclk = 1843200;
}

/*
 * Setup the MND registers to use the TCXO clock divided by 4.
 */
static void msm_serial_set_mnd_regs_tcxoby4(struct uart_port *port)
{
	msm_write(port, 0x18, UART_MREG);
	msm_write(port, 0xF6, UART_NREG);
	msm_write(port, 0x0F, UART_DREG);
	msm_write(port, 0x0A, UART_MNDREG);
	port->uartclk = 1843200;
}

static void msm_serial_set_mnd_regs(struct uart_port *port)
{
	struct msm_port *msm_port = UART_TO_MSM(port);

	/*
	 * These registers don't exist so we change the clk input rate
	 * on uartdm hardware instead
	 */
	if (msm_port->is_uartdm)
		return;

	if (port->uartclk == 19200000)
		msm_serial_set_mnd_regs_tcxo(port);
	else if (port->uartclk == 4800000)
		msm_serial_set_mnd_regs_tcxoby4(port);
}

static void msm_handle_tx(struct uart_port *port);
static void msm_start_rx_dma(struct msm_port *msm_port);

static void msm_stop_dma(struct uart_port *port, struct msm_dma *dma)
{
	struct device *dev = port->dev;
	unsigned int mapped;
	u32 val;

	mapped = dma->count;
	dma->count = 0;

	dmaengine_terminate_all(dma->chan);

	/*
	 * DMA Stall happens if enqueue and flush command happens concurrently.
	 * For example before changing the baud rate/protocol configuration and
	 * sending flush command to ADM, disable the channel of UARTDM.
	 * Note: should not reset the receiver here immediately as it is not
	 * suggested to do disable/reset or reset/disable at the same time.
	 */
	val = msm_read(port, UARTDM_DMEN);
	val &= ~dma->enable_bit;
	msm_write(port, val, UARTDM_DMEN);

	if (mapped)
		dma_unmap_single(dev, dma->phys, mapped, dma->dir);
}

static void msm_release_dma(struct msm_port *msm_port)
{
	struct msm_dma *dma;

	dma = &msm_port->tx_dma;
	if (dma->chan) {
		msm_stop_dma(&msm_port->uart, dma);
		dma_release_channel(dma->chan);
	}

	memset(dma, 0, sizeof(*dma));

	dma = &msm_port->rx_dma;
	if (dma->chan) {
		msm_stop_dma(&msm_port->uart, dma);
		dma_release_channel(dma->chan);
		kfree(dma->virt);
	}

	memset(dma, 0, sizeof(*dma));
}

static void msm_request_tx_dma(struct msm_port *msm_port, resource_size_t base)
{
	struct device *dev = msm_port->uart.dev;
	struct dma_slave_config conf;
	struct msm_dma *dma;
	u32 crci = 0;
	int ret;

	dma = &msm_port->tx_dma;

	/* allocate DMA resources, if available */
	dma->chan = dma_request_slave_channel_reason(dev, "tx");
	if (IS_ERR(dma->chan))
		goto no_tx;

	of_property_read_u32(dev->of_node, "qcom,tx-crci", &crci);

	memset(&conf, 0, sizeof(conf));
	conf.direction = DMA_MEM_TO_DEV;
	conf.device_fc = true;
	conf.dst_addr = base + UARTDM_TF;
	conf.dst_maxburst = UARTDM_BURST_SIZE;
	conf.slave_id = crci;

	ret = dmaengine_slave_config(dma->chan, &conf);
	if (ret)
		goto rel_tx;

	dma->dir = DMA_TO_DEVICE;

	if (msm_port->is_uartdm < UARTDM_1P4)
		dma->enable_bit = UARTDM_DMEN_TX_DM_ENABLE;
	else
		dma->enable_bit = UARTDM_DMEN_TX_BAM_ENABLE;

	return;

rel_tx:
	dma_release_channel(dma->chan);
no_tx:
	memset(dma, 0, sizeof(*dma));
}

static void msm_request_rx_dma(struct msm_port *msm_port, resource_size_t base)
{
	struct device *dev = msm_port->uart.dev;
	struct dma_slave_config conf;
	struct msm_dma *dma;
	u32 crci = 0;
	int ret;

	dma = &msm_port->rx_dma;

	/* allocate DMA resources, if available */
	dma->chan = dma_request_slave_channel_reason(dev, "rx");
	if (IS_ERR(dma->chan))
		goto no_rx;

	of_property_read_u32(dev->of_node, "qcom,rx-crci", &crci);

	dma->virt = kzalloc(UARTDM_RX_SIZE, GFP_KERNEL);
	if (!dma->virt)
		goto rel_rx;

	memset(&conf, 0, sizeof(conf));
	conf.direction = DMA_DEV_TO_MEM;
	conf.device_fc = true;
	conf.src_addr = base + UARTDM_RF;
	conf.src_maxburst = UARTDM_BURST_SIZE;
	conf.slave_id = crci;

	ret = dmaengine_slave_config(dma->chan, &conf);
	if (ret)
		goto err;

	dma->dir = DMA_FROM_DEVICE;

	if (msm_port->is_uartdm < UARTDM_1P4)
		dma->enable_bit = UARTDM_DMEN_RX_DM_ENABLE;
	else
		dma->enable_bit = UARTDM_DMEN_RX_BAM_ENABLE;

	return;
err:
	kfree(dma->virt);
rel_rx:
	dma_release_channel(dma->chan);
no_rx:
	memset(dma, 0, sizeof(*dma));
}

static inline void msm_wait_for_xmitr(struct uart_port *port)
{
	unsigned int timeout = 500000;

	while (!(msm_read(port, UART_SR) & UART_SR_TX_EMPTY)) {
		if (msm_read(port, UART_ISR) & UART_ISR_TX_READY)
			break;
		udelay(1);
		if (!timeout--)
			break;
	}
	msm_write(port, UART_CR_CMD_RESET_TX_READY, UART_CR);
}

static void msm_stop_tx(struct uart_port *port)
{
	struct msm_port *msm_port = UART_TO_MSM(port);

	msm_port->imr &= ~UART_IMR_TXLEV;
	msm_write(port, msm_port->imr, UART_IMR);
}

static void msm_start_tx(struct uart_port *port)
{
	struct msm_port *msm_port = UART_TO_MSM(port);
	struct msm_dma *dma = &msm_port->tx_dma;

	/* Already started in DMA mode */
	if (dma->count)
		return;

	msm_port->imr |= UART_IMR_TXLEV;
	msm_write(port, msm_port->imr, UART_IMR);
}

static void msm_reset_dm_count(struct uart_port *port, int count)
{
	msm_wait_for_xmitr(port);
	msm_write(port, count, UARTDM_NCF_TX);
	msm_read(port, UARTDM_NCF_TX);
}

static void msm_complete_tx_dma(void *args)
{
	struct msm_port *msm_port = args;
	struct uart_port *port = &msm_port->uart;
	struct circ_buf *xmit = &port->state->xmit;
	struct msm_dma *dma = &msm_port->tx_dma;
	struct dma_tx_state state;
	enum dma_status status;
	unsigned long flags;
	unsigned int count;
	u32 val;

	spin_lock_irqsave(&port->lock, flags);

	/* Already stopped */
	if (!dma->count)
		goto done;

	status = dmaengine_tx_status(dma->chan, dma->cookie, &state);

	dma_unmap_single(port->dev, dma->phys, dma->count, dma->dir);

	val = msm_read(port, UARTDM_DMEN);
	val &= ~dma->enable_bit;
	msm_write(port, val, UARTDM_DMEN);

	if (msm_port->is_uartdm > UARTDM_1P3) {
		msm_write(port, UART_CR_CMD_RESET_TX, UART_CR);
		msm_write(port, UART_CR_TX_ENABLE, UART_CR);
	}

	count = dma->count - state.residue;
	port->icount.tx += count;
	dma->count = 0;

	xmit->tail += count;
	xmit->tail &= UART_XMIT_SIZE - 1;

	/* Restore "Tx FIFO below watermark" interrupt */
	msm_port->imr |= UART_IMR_TXLEV;
	msm_write(port, msm_port->imr, UART_IMR);

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

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

static int msm_handle_tx_dma(struct msm_port *msm_port, unsigned int count)
{
	struct circ_buf *xmit = &msm_port->uart.state->xmit;
	struct uart_port *port = &msm_port->uart;
	struct msm_dma *dma = &msm_port->tx_dma;
	void *cpu_addr;
	int ret;
	u32 val;

	cpu_addr = &xmit->buf[xmit->tail];

	dma->phys = dma_map_single(port->dev, cpu_addr, count, dma->dir);
	ret = dma_mapping_error(port->dev, dma->phys);
	if (ret)
		return ret;

	dma->desc = dmaengine_prep_slave_single(dma->chan, dma->phys,
						count, DMA_MEM_TO_DEV,
						DMA_PREP_INTERRUPT |
						DMA_PREP_FENCE);
	if (!dma->desc) {
		ret = -EIO;
		goto unmap;
	}

	dma->desc->callback = msm_complete_tx_dma;
	dma->desc->callback_param = msm_port;

	dma->cookie = dmaengine_submit(dma->desc);
	ret = dma_submit_error(dma->cookie);
	if (ret)
		goto unmap;

	/*
	 * Using DMA complete for Tx FIFO reload, no need for
	 * "Tx FIFO below watermark" one, disable it
	 */
	msm_port->imr &= ~UART_IMR_TXLEV;
	msm_write(port, msm_port->imr, UART_IMR);

	dma->count = count;

	val = msm_read(port, UARTDM_DMEN);
	val |= dma->enable_bit;

	if (msm_port->is_uartdm < UARTDM_1P4)
		msm_write(port, val, UARTDM_DMEN);

	msm_reset_dm_count(port, count);

	if (msm_port->is_uartdm > UARTDM_1P3)
		msm_write(port, val, UARTDM_DMEN);

	dma_async_issue_pending(dma->chan);
	return 0;
unmap:
	dma_unmap_single(port->dev, dma->phys, count, dma->dir);
	return ret;
}

static void msm_complete_rx_dma(void *args)
{
	struct msm_port *msm_port = args;
	struct uart_port *port = &msm_port->uart;
	struct tty_port *tport = &port->state->port;
	struct msm_dma *dma = &msm_port->rx_dma;
	int count = 0, i, sysrq;
	unsigned long flags;
	u32 val;

	spin_lock_irqsave(&port->lock, flags);

	/* Already stopped */
	if (!dma->count)
		goto done;

	val = msm_read(port, UARTDM_DMEN);
	val &= ~dma->enable_bit;
	msm_write(port, val, UARTDM_DMEN);

	if (msm_read(port, UART_SR) & UART_SR_OVERRUN) {
		port->icount.overrun++;
		tty_insert_flip_char(tport, 0, TTY_OVERRUN);
		msm_write(port, UART_CR_CMD_RESET_ERR, UART_CR);
	}

	count = msm_read(port, UARTDM_RX_TOTAL_SNAP);

	port->icount.rx += count;

	dma->count = 0;

	dma_unmap_single(port->dev, dma->phys, UARTDM_RX_SIZE, dma->dir);

	for (i = 0; i < count; i++) {
		char flag = TTY_NORMAL;

		if (msm_port->break_detected && dma->virt[i] == 0) {
			port->icount.brk++;
			flag = TTY_BREAK;
			msm_port->break_detected = false;
			if (uart_handle_break(port))
				continue;
		}

		if (!(port->read_status_mask & UART_SR_RX_BREAK))
			flag = TTY_NORMAL;

		spin_unlock_irqrestore(&port->lock, flags);
		sysrq = uart_handle_sysrq_char(port, dma->virt[i]);
		spin_lock_irqsave(&port->lock, flags);
		if (!sysrq)
			tty_insert_flip_char(tport, dma->virt[i], flag);
	}

	msm_start_rx_dma(msm_port);
done:
	spin_unlock_irqrestore(&port->lock, flags);

	if (count)
		tty_flip_buffer_push(tport);
}

static void msm_start_rx_dma(struct msm_port *msm_port)
{
	struct msm_dma *dma = &msm_port->rx_dma;
	struct uart_port *uart = &msm_port->uart;
	u32 val;
	int ret;

	if (!dma->chan)
		return;

	dma->phys = dma_map_single(uart->dev, dma->virt,
				   UARTDM_RX_SIZE, dma->dir);
	ret = dma_mapping_error(uart->dev, dma->phys);
	if (ret)
		return;

	dma->desc = dmaengine_prep_slave_single(dma->chan, dma->phys,
						UARTDM_RX_SIZE, DMA_DEV_TO_MEM,
						DMA_PREP_INTERRUPT);
	if (!dma->desc)
		goto unmap;

	dma->desc->callback = msm_complete_rx_dma;
	dma->desc->callback_param = msm_port;

	dma->cookie = dmaengine_submit(dma->desc);
	ret = dma_submit_error(dma->cookie);
	if (ret)
		goto unmap;
	/*
	 * Using DMA for FIFO off-load, no need for "Rx FIFO over
	 * watermark" or "stale" interrupts, disable them
	 */
	msm_port->imr &= ~(UART_IMR_RXLEV | UART_IMR_RXSTALE);

	/*
	 * Well, when DMA is ADM3 engine(implied by <= UARTDM v1.3),
	 * we need RXSTALE to flush input DMA fifo to memory
	 */
	if (msm_port->is_uartdm < UARTDM_1P4)
		msm_port->imr |= UART_IMR_RXSTALE;

	msm_write(uart, msm_port->imr, UART_IMR);

	dma->count = UARTDM_RX_SIZE;

	dma_async_issue_pending(dma->chan);

	msm_write(uart, UART_CR_CMD_RESET_STALE_INT, UART_CR);
	msm_write(uart, UART_CR_CMD_STALE_EVENT_ENABLE, UART_CR);

	val = msm_read(uart, UARTDM_DMEN);
	val |= dma->enable_bit;

	if (msm_port->is_uartdm < UARTDM_1P4)
		msm_write(uart, val, UARTDM_DMEN);

	msm_write(uart, UARTDM_RX_SIZE, UARTDM_DMRX);

	if (msm_port->is_uartdm > UARTDM_1P3)
		msm_write(uart, val, UARTDM_DMEN);

	return;
unmap:
	dma_unmap_single(uart->dev, dma->phys, UARTDM_RX_SIZE, dma->dir);
}

static void msm_stop_rx(struct uart_port *port)
{
	struct msm_port *msm_port = UART_TO_MSM(port);
	struct msm_dma *dma = &msm_port->rx_dma;

	msm_port->imr &= ~(UART_IMR_RXLEV | UART_IMR_RXSTALE);
	msm_write(port, msm_port->imr, UART_IMR);

	if (dma->chan)
		msm_stop_dma(port, dma);
}

static void msm_enable_ms(struct uart_port *port)
{
	struct msm_port *msm_port = UART_TO_MSM(port);

	msm_port->imr |= UART_IMR_DELTA_CTS;
	msm_write(port, msm_port->imr, UART_IMR);
}

static void msm_handle_rx_dm(struct uart_port *port, unsigned int misr)
{
	struct tty_port *tport = &port->state->port;
	unsigned int sr;
	int count = 0;
	struct msm_port *msm_port = UART_TO_MSM(port);

	if ((msm_read(port, UART_SR) & UART_SR_OVERRUN)) {
		port->icount.overrun++;
		tty_insert_flip_char(tport, 0, TTY_OVERRUN);
		msm_write(port, UART_CR_CMD_RESET_ERR, UART_CR);
	}

	if (misr & UART_IMR_RXSTALE) {
		count = msm_read(port, UARTDM_RX_TOTAL_SNAP) -
			msm_port->old_snap_state;
		msm_port->old_snap_state = 0;
	} else {
		count = 4 * (msm_read(port, UART_RFWR));
		msm_port->old_snap_state += count;
	}

	/* TODO: Precise error reporting */

	port->icount.rx += count;

	while (count > 0) {
		unsigned char buf[4];
		int sysrq, r_count, i;

		sr = msm_read(port, UART_SR);
		if ((sr & UART_SR_RX_READY) == 0) {
			msm_port->old_snap_state -= count;
			break;
		}

		ioread32_rep(port->membase + UARTDM_RF, buf, 1);
		r_count = min_t(int, count, sizeof(buf));

		for (i = 0; i < r_count; i++) {
			char flag = TTY_NORMAL;

			if (msm_port->break_detected && buf[i] == 0) {
				port->icount.brk++;
				flag = TTY_BREAK;
				msm_port->break_detected = false;
				if (uart_handle_break(port))
					continue;
			}

			if (!(port->read_status_mask & UART_SR_RX_BREAK))
				flag = TTY_NORMAL;

			spin_unlock(&port->lock);
			sysrq = uart_handle_sysrq_char(port, buf[i]);
			spin_lock(&port->lock);
			if (!sysrq)
				tty_insert_flip_char(tport, buf[i], flag);
		}
		count -= r_count;
	}

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

	if (misr & (UART_IMR_RXSTALE))
		msm_write(port, UART_CR_CMD_RESET_STALE_INT, UART_CR);
	msm_write(port, 0xFFFFFF, UARTDM_DMRX);
	msm_write(port, UART_CR_CMD_STALE_EVENT_ENABLE, UART_CR);

	/* Try to use DMA */
	msm_start_rx_dma(msm_port);
}

static void msm_handle_rx(struct uart_port *port)
{
	struct tty_port *tport = &port->state->port;
	unsigned int sr;

	/*
	 * Handle overrun. My understanding of the hardware is that overrun
	 * is not tied to the RX buffer, so we handle the case out of band.
	 */
	if ((msm_read(port, UART_SR) & UART_SR_OVERRUN)) {
		port->icount.overrun++;
		tty_insert_flip_char(tport, 0, TTY_OVERRUN);
		msm_write(port, UART_CR_CMD_RESET_ERR, UART_CR);
	}

	/* and now the main RX loop */
	while ((sr = msm_read(port, UART_SR)) & UART_SR_RX_READY) {
		unsigned int c;
		char flag = TTY_NORMAL;
		int sysrq;

		c = msm_read(port, UART_RF);

		if (sr & UART_SR_RX_BREAK) {
			port->icount.brk++;
			if (uart_handle_break(port))
				continue;
		} else if (sr & UART_SR_PAR_FRAME_ERR) {
			port->icount.frame++;
		} else {
			port->icount.rx++;
		}

		/* Mask conditions we're ignorning. */
		sr &= port->read_status_mask;

		if (sr & UART_SR_RX_BREAK)
			flag = TTY_BREAK;
		else if (sr & UART_SR_PAR_FRAME_ERR)
			flag = TTY_FRAME;

		spin_unlock(&port->lock);
		sysrq = uart_handle_sysrq_char(port, c);
		spin_lock(&port->lock);
		if (!sysrq)
			tty_insert_flip_char(tport, c, flag);
	}

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

static void msm_handle_tx_pio(struct uart_port *port, unsigned int tx_count)
{
	struct circ_buf *xmit = &port->state->xmit;
	struct msm_port *msm_port = UART_TO_MSM(port);
	unsigned int num_chars;
	unsigned int tf_pointer = 0;
	void __iomem *tf;

	if (msm_port->is_uartdm)
		tf = port->membase + UARTDM_TF;
	else
		tf = port->membase + UART_TF;

	if (tx_count && msm_port->is_uartdm)
		msm_reset_dm_count(port, tx_count);

	while (tf_pointer < tx_count) {
		int i;
		char buf[4] = { 0 };

		if (!(msm_read(port, UART_SR) & UART_SR_TX_READY))
			break;

		if (msm_port->is_uartdm)
			num_chars = min(tx_count - tf_pointer,
					(unsigned int)sizeof(buf));
		else
			num_chars = 1;

		for (i = 0; i < num_chars; i++) {
			buf[i] = xmit->buf[xmit->tail + i];
			port->icount.tx++;
		}

		iowrite32_rep(tf, buf, 1);
		xmit->tail = (xmit->tail + num_chars) & (UART_XMIT_SIZE - 1);
		tf_pointer += num_chars;
	}

	/* disable tx interrupts if nothing more to send */
	if (uart_circ_empty(xmit))
		msm_stop_tx(port);

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

static void msm_handle_tx(struct uart_port *port)
{
	struct msm_port *msm_port = UART_TO_MSM(port);
	struct circ_buf *xmit = &msm_port->uart.state->xmit;
	struct msm_dma *dma = &msm_port->tx_dma;
	unsigned int pio_count, dma_count, dma_min;
	char buf[4] = { 0 };
	void __iomem *tf;
	int err = 0;

	if (port->x_char) {
		if (msm_port->is_uartdm)
			tf = port->membase + UARTDM_TF;
		else
			tf = port->membase + UART_TF;

		buf[0] = port->x_char;

		if (msm_port->is_uartdm)
			msm_reset_dm_count(port, 1);

		iowrite32_rep(tf, buf, 1);
		port->icount.tx++;
		port->x_char = 0;
		return;
	}

	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
		msm_stop_tx(port);
		return;
	}

	pio_count = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
	dma_count = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);

	dma_min = 1;	/* Always DMA */
	if (msm_port->is_uartdm > UARTDM_1P3) {
		dma_count = UARTDM_TX_AIGN(dma_count);
		dma_min = UARTDM_BURST_SIZE;
	} else {
		if (dma_count > UARTDM_TX_MAX)
			dma_count = UARTDM_TX_MAX;
	}

	if (pio_count > port->fifosize)
		pio_count = port->fifosize;

	if (!dma->chan || dma_count < dma_min)
		msm_handle_tx_pio(port, pio_count);
	else
		err = msm_handle_tx_dma(msm_port, dma_count);

	if (err)	/* fall back to PIO mode */
		msm_handle_tx_pio(port, pio_count);
}

static void msm_handle_delta_cts(struct uart_port *port)
{
	msm_write(port, UART_CR_CMD_RESET_CTS, UART_CR);
	port->icount.cts++;
	wake_up_interruptible(&port->state->port.delta_msr_wait);
}

static irqreturn_t msm_uart_irq(int irq, void *dev_id)
{
	struct uart_port *port = dev_id;
	struct msm_port *msm_port = UART_TO_MSM(port);
	struct msm_dma *dma = &msm_port->rx_dma;
	unsigned long flags;
	unsigned int misr;
	u32 val;

	spin_lock_irqsave(&port->lock, flags);
	misr = msm_read(port, UART_MISR);
	msm_write(port, 0, UART_IMR); /* disable interrupt */

	if (misr & UART_IMR_RXBREAK_START) {
		msm_port->break_detected = true;
		msm_write(port, UART_CR_CMD_RESET_RXBREAK_START, UART_CR);
	}

	if (misr & (UART_IMR_RXLEV | UART_IMR_RXSTALE)) {
		if (dma->count) {
			val = UART_CR_CMD_STALE_EVENT_DISABLE;
			msm_write(port, val, UART_CR);
			val = UART_CR_CMD_RESET_STALE_INT;
			msm_write(port, val, UART_CR);
			/*
			 * Flush DMA input fifo to memory, this will also
			 * trigger DMA RX completion
			 */
			dmaengine_terminate_all(dma->chan);
		} else if (msm_port->is_uartdm) {
			msm_handle_rx_dm(port, misr);
		} else {
			msm_handle_rx(port);
		}
	}
	if (misr & UART_IMR_TXLEV)
		msm_handle_tx(port);
	if (misr & UART_IMR_DELTA_CTS)
		msm_handle_delta_cts(port);

	msm_write(port, msm_port->imr, UART_IMR); /* restore interrupt */
	spin_unlock_irqrestore(&port->lock, flags);

	return IRQ_HANDLED;
}

static unsigned int msm_tx_empty(struct uart_port *port)
{
	return (msm_read(port, UART_SR) & UART_SR_TX_EMPTY) ? TIOCSER_TEMT : 0;
}

static unsigned int msm_get_mctrl(struct uart_port *port)
{
	return TIOCM_CAR | TIOCM_CTS | TIOCM_DSR | TIOCM_RTS;
}

static void msm_reset(struct uart_port *port)
{
	struct msm_port *msm_port = UART_TO_MSM(port);
	unsigned int mr;

	/* reset everything */
	msm_write(port, UART_CR_CMD_RESET_RX, UART_CR);
	msm_write(port, UART_CR_CMD_RESET_TX, UART_CR);
	msm_write(port, UART_CR_CMD_RESET_ERR, UART_CR);
	msm_write(port, UART_CR_CMD_RESET_BREAK_INT, UART_CR);
	msm_write(port, UART_CR_CMD_RESET_CTS, UART_CR);
	msm_write(port, UART_CR_CMD_RESET_RFR, UART_CR);
	mr = msm_read(port, UART_MR1);
	mr &= ~UART_MR1_RX_RDY_CTL;
	msm_write(port, mr, UART_MR1);

	/* Disable DM modes */
	if (msm_port->is_uartdm)
		msm_write(port, 0, UARTDM_DMEN);
}

static void msm_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
	unsigned int mr;

	mr = msm_read(port, UART_MR1);

	if (!(mctrl & TIOCM_RTS)) {
		mr &= ~UART_MR1_RX_RDY_CTL;
		msm_write(port, mr, UART_MR1);
		msm_write(port, UART_CR_CMD_RESET_RFR, UART_CR);
	} else {
		mr |= UART_MR1_RX_RDY_CTL;
		msm_write(port, mr, UART_MR1);
	}
}

static void msm_break_ctl(struct uart_port *port, int break_ctl)
{
	if (break_ctl)
		msm_write(port, UART_CR_CMD_START_BREAK, UART_CR);
	else
		msm_write(port, UART_CR_CMD_STOP_BREAK, UART_CR);
}

struct msm_baud_map {
	u16	divisor;
	u8	code;
	u8	rxstale;
};

static const struct msm_baud_map *
msm_find_best_baud(struct uart_port *port, unsigned int baud,
		   unsigned long *rate)
{
	struct msm_port *msm_port = UART_TO_MSM(port);
	unsigned int divisor, result;
	unsigned long target, old, best_rate = 0, diff, best_diff = ULONG_MAX;
	const struct msm_baud_map *entry, *end, *best;
	static const struct msm_baud_map table[] = {
		{    1, 0xff, 31 },
		{    2, 0xee, 16 },
		{    3, 0xdd,  8 },
		{    4, 0xcc,  6 },
		{    6, 0xbb,  6 },
		{    8, 0xaa,  6 },
		{   12, 0x99,  6 },
		{   16, 0x88,  1 },
		{   24, 0x77,  1 },
		{   32, 0x66,  1 },
		{   48, 0x55,  1 },
		{   96, 0x44,  1 },
		{  192, 0x33,  1 },
		{  384, 0x22,  1 },
		{  768, 0x11,  1 },
		{ 1536, 0x00,  1 },
	};

	best = table; /* Default to smallest divider */
	target = clk_round_rate(msm_port->clk, 16 * baud);
	divisor = DIV_ROUND_CLOSEST(target, 16 * baud);

	end = table + ARRAY_SIZE(table);
	entry = table;
	while (entry < end) {
		if (entry->divisor <= divisor) {
			result = target / entry->divisor / 16;
			diff = abs(result - baud);

			/* Keep track of best entry */
			if (diff < best_diff) {
				best_diff = diff;
				best = entry;
				best_rate = target;
			}

			if (result == baud)
				break;
		} else if (entry->divisor > divisor) {
			old = target;
			target = clk_round_rate(msm_port->clk, old + 1);
			/*
			 * The rate didn't get any faster so we can't do
			 * better at dividing it down
			 */
			if (target == old)
				break;

			/* Start the divisor search over at this new rate */
			entry = table;
			divisor = DIV_ROUND_CLOSEST(target, 16 * baud);
			continue;
		}
		entry++;
	}

	*rate = best_rate;
	return best;
}

static int msm_set_baud_rate(struct uart_port *port, unsigned int baud,
			     unsigned long *saved_flags)
{
	unsigned int rxstale, watermark, mask;
	struct msm_port *msm_port = UART_TO_MSM(port);
	const struct msm_baud_map *entry;
	unsigned long flags, rate;

	flags = *saved_flags;
	spin_unlock_irqrestore(&port->lock, flags);

	entry = msm_find_best_baud(port, baud, &rate);
	clk_set_rate(msm_port->clk, rate);
	baud = rate / 16 / entry->divisor;

	spin_lock_irqsave(&port->lock, flags);
	*saved_flags = flags;
	port->uartclk = rate;

	msm_write(port, entry->code, UART_CSR);

	/* RX stale watermark */
	rxstale = entry->rxstale;
	watermark = UART_IPR_STALE_LSB & rxstale;
	if (msm_port->is_uartdm) {
		mask = UART_DM_IPR_STALE_TIMEOUT_MSB;
	} else {
		watermark |= UART_IPR_RXSTALE_LAST;
		mask = UART_IPR_STALE_TIMEOUT_MSB;
	}

	watermark |= mask & (rxstale << 2);

	msm_write(port, watermark, UART_IPR);

	/* set RX watermark */
	watermark = (port->fifosize * 3) / 4;
	msm_write(port, watermark, UART_RFWR);

	/* set TX watermark */
	msm_write(port, 10, UART_TFWR);

	msm_write(port, UART_CR_CMD_PROTECTION_EN, UART_CR);
	msm_reset(port);

	/* Enable RX and TX */
	msm_write(port, UART_CR_TX_ENABLE | UART_CR_RX_ENABLE, UART_CR);

	/* turn on RX and CTS interrupts */
	msm_port->imr = UART_IMR_RXLEV | UART_IMR_RXSTALE |
			UART_IMR_CURRENT_CTS | UART_IMR_RXBREAK_START;

	msm_write(port, msm_port->imr, UART_IMR);

	if (msm_port->is_uartdm) {
		msm_write(port, UART_CR_CMD_RESET_STALE_INT, UART_CR);
		msm_write(port, 0xFFFFFF, UARTDM_DMRX);
		msm_write(port, UART_CR_CMD_STALE_EVENT_ENABLE, UART_CR);
	}

	return baud;
}

static void msm_init_clock(struct uart_port *port)
{
	struct msm_port *msm_port = UART_TO_MSM(port);

	clk_prepare_enable(msm_port->clk);
	clk_prepare_enable(msm_port->pclk);
	msm_serial_set_mnd_regs(port);
}

static int msm_startup(struct uart_port *port)
{
	struct msm_port *msm_port = UART_TO_MSM(port);
	unsigned int data, rfr_level, mask;
	int ret;

	snprintf(msm_port->name, sizeof(msm_port->name),
		 "msm_serial%d", port->line);

	msm_init_clock(port);

	if (likely(port->fifosize > 12))
		rfr_level = port->fifosize - 12;
	else
		rfr_level = port->fifosize;

	/* set automatic RFR level */
	data = msm_read(port, UART_MR1);

	if (msm_port->is_uartdm)
		mask = UART_DM_MR1_AUTO_RFR_LEVEL1;
	else
		mask = UART_MR1_AUTO_RFR_LEVEL1;

	data &= ~mask;
	data &= ~UART_MR1_AUTO_RFR_LEVEL0;
	data |= mask & (rfr_level << 2);
	data |= UART_MR1_AUTO_RFR_LEVEL0 & rfr_level;
	msm_write(port, data, UART_MR1);

	if (msm_port->is_uartdm) {
		msm_request_tx_dma(msm_port, msm_port->uart.mapbase);
		msm_request_rx_dma(msm_port, msm_port->uart.mapbase);
	}

	ret = request_irq(port->irq, msm_uart_irq, IRQF_TRIGGER_HIGH,
			  msm_port->name, port);
	if (unlikely(ret))
		goto err_irq;

	return 0;

err_irq:
	if (msm_port->is_uartdm)
		msm_release_dma(msm_port);

	clk_disable_unprepare(msm_port->pclk);
	clk_disable_unprepare(msm_port->clk);

	return ret;
}

static void msm_shutdown(struct uart_port *port)
{
	struct msm_port *msm_port = UART_TO_MSM(port);

	msm_port->imr = 0;
	msm_write(port, 0, UART_IMR); /* disable interrupts */

	if (msm_port->is_uartdm)
		msm_release_dma(msm_port);

	clk_disable_unprepare(msm_port->clk);

	free_irq(port->irq, port);
}

static void msm_set_termios(struct uart_port *port, struct ktermios *termios,
			    struct ktermios *old)
{
	struct msm_port *msm_port = UART_TO_MSM(port);
	struct msm_dma *dma = &msm_port->rx_dma;
	unsigned long flags;
	unsigned int baud, mr;

	spin_lock_irqsave(&port->lock, flags);

	if (dma->chan) /* Terminate if any */
		msm_stop_dma(port, dma);

	/* calculate and set baud rate */
	baud = uart_get_baud_rate(port, termios, old, 300, 4000000);
	baud = msm_set_baud_rate(port, baud, &flags);
	if (tty_termios_baud_rate(termios))
		tty_termios_encode_baud_rate(termios, baud, baud);

	/* calculate parity */
	mr = msm_read(port, UART_MR2);
	mr &= ~UART_MR2_PARITY_MODE;
	if (termios->c_cflag & PARENB) {
		if (termios->c_cflag & PARODD)
			mr |= UART_MR2_PARITY_MODE_ODD;
		else if (termios->c_cflag & CMSPAR)
			mr |= UART_MR2_PARITY_MODE_SPACE;
		else
			mr |= UART_MR2_PARITY_MODE_EVEN;
	}

	/* calculate bits per char */
	mr &= ~UART_MR2_BITS_PER_CHAR;
	switch (termios->c_cflag & CSIZE) {
	case CS5:
		mr |= UART_MR2_BITS_PER_CHAR_5;
		break;
	case CS6:
		mr |= UART_MR2_BITS_PER_CHAR_6;
		break;
	case CS7:
		mr |= UART_MR2_BITS_PER_CHAR_7;
		break;
	case CS8:
	default:
		mr |= UART_MR2_BITS_PER_CHAR_8;
		break;
	}

	/* calculate stop bits */
	mr &= ~(UART_MR2_STOP_BIT_LEN_ONE | UART_MR2_STOP_BIT_LEN_TWO);
	if (termios->c_cflag & CSTOPB)
		mr |= UART_MR2_STOP_BIT_LEN_TWO;
	else
		mr |= UART_MR2_STOP_BIT_LEN_ONE;

	/* set parity, bits per char, and stop bit */
	msm_write(port, mr, UART_MR2);

	/* calculate and set hardware flow control */
	mr = msm_read(port, UART_MR1);
	mr &= ~(UART_MR1_CTS_CTL | UART_MR1_RX_RDY_CTL);
	if (termios->c_cflag & CRTSCTS) {
		mr |= UART_MR1_CTS_CTL;
		mr |= UART_MR1_RX_RDY_CTL;
	}
	msm_write(port, mr, UART_MR1);

	/* Configure status bits to ignore based on termio flags. */
	port->read_status_mask = 0;
	if (termios->c_iflag & INPCK)
		port->read_status_mask |= UART_SR_PAR_FRAME_ERR;
	if (termios->c_iflag & (IGNBRK | BRKINT | PARMRK))
		port->read_status_mask |= UART_SR_RX_BREAK;

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

	/* Try to use DMA */
	msm_start_rx_dma(msm_port);

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

static const char *msm_type(struct uart_port *port)
{
	return "MSM";
}

static void msm_release_port(struct uart_port *port)
{
	struct platform_device *pdev = to_platform_device(port->dev);
	struct resource *uart_resource;
	resource_size_t size;

	uart_resource = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (unlikely(!uart_resource))
		return;
	size = resource_size(uart_resource);

	release_mem_region(port->mapbase, size);
	iounmap(port->membase);
	port->membase = NULL;
}

static int msm_request_port(struct uart_port *port)
{
	struct platform_device *pdev = to_platform_device(port->dev);
	struct resource *uart_resource;
	resource_size_t size;
	int ret;

	uart_resource = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (unlikely(!uart_resource))
		return -ENXIO;

	size = resource_size(uart_resource);

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

	port->membase = ioremap(port->mapbase, size);
	if (!port->membase) {
		ret = -EBUSY;
		goto fail_release_port;
	}

	return 0;

fail_release_port:
	release_mem_region(port->mapbase, size);
	return ret;
}

static void msm_config_port(struct uart_port *port, int flags)
{
	int ret;

	if (flags & UART_CONFIG_TYPE) {
		port->type = PORT_MSM;
		ret = msm_request_port(port);
		if (ret)
			return;
	}
}

static int msm_verify_port(struct uart_port *port, struct serial_struct *ser)
{
	if (unlikely(ser->type != PORT_UNKNOWN && ser->type != PORT_MSM))
		return -EINVAL;
	if (unlikely(port->irq != ser->irq))
		return -EINVAL;
	return 0;
}

static void msm_power(struct uart_port *port, unsigned int state,
		      unsigned int oldstate)
{
	struct msm_port *msm_port = UART_TO_MSM(port);

	switch (state) {
	case 0:
		clk_prepare_enable(msm_port->clk);
		clk_prepare_enable(msm_port->pclk);
		break;
	case 3:
		clk_disable_unprepare(msm_port->clk);
		clk_disable_unprepare(msm_port->pclk);
		break;
	default:
		pr_err("msm_serial: Unknown PM state %d\n", state);
	}
}

#ifdef CONFIG_CONSOLE_POLL
static int msm_poll_get_char_single(struct uart_port *port)
{
	struct msm_port *msm_port = UART_TO_MSM(port);
	unsigned int rf_reg = msm_port->is_uartdm ? UARTDM_RF : UART_RF;

	if (!(msm_read(port, UART_SR) & UART_SR_RX_READY))
		return NO_POLL_CHAR;

	return msm_read(port, rf_reg) & 0xff;
}

static int msm_poll_get_char_dm(struct uart_port *port)
{
	int c;
	static u32 slop;
	static int count;
	unsigned char *sp = (unsigned char *)&slop;

	/* Check if a previous read had more than one char */
	if (count) {
		c = sp[sizeof(slop) - count];
		count--;
	/* Or if FIFO is empty */
	} else if (!(msm_read(port, UART_SR) & UART_SR_RX_READY)) {
		/*
		 * If RX packing buffer has less than a word, force stale to
		 * push contents into RX FIFO
		 */
		count = msm_read(port, UARTDM_RXFS);
		count = (count >> UARTDM_RXFS_BUF_SHIFT) & UARTDM_RXFS_BUF_MASK;
		if (count) {
			msm_write(port, UART_CR_CMD_FORCE_STALE, UART_CR);
			slop = msm_read(port, UARTDM_RF);
			c = sp[0];
			count--;
			msm_write(port, UART_CR_CMD_RESET_STALE_INT, UART_CR);
			msm_write(port, 0xFFFFFF, UARTDM_DMRX);
			msm_write(port, UART_CR_CMD_STALE_EVENT_ENABLE,
				  UART_CR);
		} else {
			c = NO_POLL_CHAR;
		}
	/* FIFO has a word */
	} else {
		slop = msm_read(port, UARTDM_RF);
		c = sp[0];
		count = sizeof(slop) - 1;
	}

	return c;
}

static int msm_poll_get_char(struct uart_port *port)
{
	u32 imr;
	int c;
	struct msm_port *msm_port = UART_TO_MSM(port);

	/* Disable all interrupts */
	imr = msm_read(port, UART_IMR);
	msm_write(port, 0, UART_IMR);

	if (msm_port->is_uartdm)
		c = msm_poll_get_char_dm(port);
	else
		c = msm_poll_get_char_single(port);

	/* Enable interrupts */
	msm_write(port, imr, UART_IMR);

	return c;
}

static void msm_poll_put_char(struct uart_port *port, unsigned char c)
{
	u32 imr;
	struct msm_port *msm_port = UART_TO_MSM(port);

	/* Disable all interrupts */
	imr = msm_read(port, UART_IMR);
	msm_write(port, 0, UART_IMR);

	if (msm_port->is_uartdm)
		msm_reset_dm_count(port, 1);

	/* Wait until FIFO is empty */
	while (!(msm_read(port, UART_SR) & UART_SR_TX_READY))
		cpu_relax();

	/* Write a character */
	msm_write(port, c, msm_port->is_uartdm ? UARTDM_TF : UART_TF);

	/* Wait until FIFO is empty */
	while (!(msm_read(port, UART_SR) & UART_SR_TX_READY))
		cpu_relax();

	/* Enable interrupts */
	msm_write(port, imr, UART_IMR);
}
#endif

static struct uart_ops msm_uart_pops = {
	.tx_empty = msm_tx_empty,
	.set_mctrl = msm_set_mctrl,
	.get_mctrl = msm_get_mctrl,
	.stop_tx = msm_stop_tx,
	.start_tx = msm_start_tx,
	.stop_rx = msm_stop_rx,
	.enable_ms = msm_enable_ms,
	.break_ctl = msm_break_ctl,
	.startup = msm_startup,
	.shutdown = msm_shutdown,
	.set_termios = msm_set_termios,
	.type = msm_type,
	.release_port = msm_release_port,
	.request_port = msm_request_port,
	.config_port = msm_config_port,
	.verify_port = msm_verify_port,
	.pm = msm_power,
#ifdef CONFIG_CONSOLE_POLL
	.poll_get_char	= msm_poll_get_char,
	.poll_put_char	= msm_poll_put_char,
#endif
};

static struct msm_port msm_uart_ports[] = {
	{
		.uart = {
			.iotype = UPIO_MEM,
			.ops = &msm_uart_pops,
			.flags = UPF_BOOT_AUTOCONF,
			.fifosize = 64,
			.line = 0,
		},
	},
	{
		.uart = {
			.iotype = UPIO_MEM,
			.ops = &msm_uart_pops,
			.flags = UPF_BOOT_AUTOCONF,
			.fifosize = 64,
			.line = 1,
		},
	},
	{
		.uart = {
			.iotype = UPIO_MEM,
			.ops = &msm_uart_pops,
			.flags = UPF_BOOT_AUTOCONF,
			.fifosize = 64,
			.line = 2,
		},
	},
};

#define UART_NR	ARRAY_SIZE(msm_uart_ports)

static inline struct uart_port *msm_get_port_from_line(unsigned int line)
{
	return &msm_uart_ports[line].uart;
}

#ifdef CONFIG_SERIAL_MSM_CONSOLE
static void __msm_console_write(struct uart_port *port, const char *s,
				unsigned int count, bool is_uartdm)
{
	int i;
	int num_newlines = 0;
	bool replaced = false;
	void __iomem *tf;
	int locked = 1;

	if (is_uartdm)
		tf = port->membase + UARTDM_TF;
	else
		tf = port->membase + UART_TF;

	/* Account for newlines that will get a carriage return added */
	for (i = 0; i < count; i++)
		if (s[i] == '\n')
			num_newlines++;
	count += num_newlines;

	if (port->sysrq)
		locked = 0;
	else if (oops_in_progress)
		locked = spin_trylock(&port->lock);
	else
		spin_lock(&port->lock);

	if (is_uartdm)
		msm_reset_dm_count(port, count);

	i = 0;
	while (i < count) {
		int j;
		unsigned int num_chars;
		char buf[4] = { 0 };

		if (is_uartdm)
			num_chars = min(count - i, (unsigned int)sizeof(buf));
		else
			num_chars = 1;

		for (j = 0; j < num_chars; j++) {
			char c = *s;

			if (c == '\n' && !replaced) {
				buf[j] = '\r';
				j++;
				replaced = true;
			}
			if (j < num_chars) {
				buf[j] = c;
				s++;
				replaced = false;
			}
		}

		while (!(msm_read(port, UART_SR) & UART_SR_TX_READY))
			cpu_relax();

		iowrite32_rep(tf, buf, 1);
		i += num_chars;
	}

	if (locked)
		spin_unlock(&port->lock);
}

static void msm_console_write(struct console *co, const char *s,
			      unsigned int count)
{
	struct uart_port *port;
	struct msm_port *msm_port;

	BUG_ON(co->index < 0 || co->index >= UART_NR);

	port = msm_get_port_from_line(co->index);
	msm_port = UART_TO_MSM(port);

	__msm_console_write(port, s, count, msm_port->is_uartdm);
}

static int __init msm_console_setup(struct console *co, char *options)
{
	struct uart_port *port;
	int baud = 115200;
	int bits = 8;
	int parity = 'n';
	int flow = 'n';

	if (unlikely(co->index >= UART_NR || co->index < 0))
		return -ENXIO;

	port = msm_get_port_from_line(co->index);

	if (unlikely(!port->membase))
		return -ENXIO;

	msm_init_clock(port);

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

	pr_info("msm_serial: console setup on port #%d\n", port->line);

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

static void
msm_serial_early_write(struct console *con, const char *s, unsigned n)
{
	struct earlycon_device *dev = con->data;

	__msm_console_write(&dev->port, s, n, false);
}

static int __init
msm_serial_early_console_setup(struct earlycon_device *device, const char *opt)
{
	if (!device->port.membase)
		return -ENODEV;

	device->con->write = msm_serial_early_write;
	return 0;
}
OF_EARLYCON_DECLARE(msm_serial, "qcom,msm-uart",
		    msm_serial_early_console_setup);

static void
msm_serial_early_write_dm(struct console *con, const char *s, unsigned n)
{
	struct earlycon_device *dev = con->data;

	__msm_console_write(&dev->port, s, n, true);
}

static int __init
msm_serial_early_console_setup_dm(struct earlycon_device *device,
				  const char *opt)
{
	if (!device->port.membase)
		return -ENODEV;

	device->con->write = msm_serial_early_write_dm;
	return 0;
}
OF_EARLYCON_DECLARE(msm_serial_dm, "qcom,msm-uartdm",
		    msm_serial_early_console_setup_dm);

static struct uart_driver msm_uart_driver;

static struct console msm_console = {
	.name = "ttyMSM",
	.write = msm_console_write,
	.device = uart_console_device,
	.setup = msm_console_setup,
	.flags = CON_PRINTBUFFER,
	.index = -1,
	.data = &msm_uart_driver,
};

#define MSM_CONSOLE	(&msm_console)

#else
#define MSM_CONSOLE	NULL
#endif

static struct uart_driver msm_uart_driver = {
	.owner = THIS_MODULE,
	.driver_name = "msm_serial",
	.dev_name = "ttyMSM",
	.nr = UART_NR,
	.cons = MSM_CONSOLE,
};

static atomic_t msm_uart_next_id = ATOMIC_INIT(0);

static const struct of_device_id msm_uartdm_table[] = {
	{ .compatible = "qcom,msm-uartdm-v1.1", .data = (void *)UARTDM_1P1 },
	{ .compatible = "qcom,msm-uartdm-v1.2", .data = (void *)UARTDM_1P2 },
	{ .compatible = "qcom,msm-uartdm-v1.3", .data = (void *)UARTDM_1P3 },
	{ .compatible = "qcom,msm-uartdm-v1.4", .data = (void *)UARTDM_1P4 },
	{ }
};

static int msm_serial_probe(struct platform_device *pdev)
{
	struct msm_port *msm_port;
	struct resource *resource;
	struct uart_port *port;
	const struct of_device_id *id;
	int irq, line;

	if (pdev->dev.of_node)
		line = of_alias_get_id(pdev->dev.of_node, "serial");
	else
		line = pdev->id;

	if (line < 0)
		line = atomic_inc_return(&msm_uart_next_id) - 1;

	if (unlikely(line < 0 || line >= UART_NR))
		return -ENXIO;

	dev_info(&pdev->dev, "msm_serial: detected port #%d\n", line);

	port = msm_get_port_from_line(line);
	port->dev = &pdev->dev;
	msm_port = UART_TO_MSM(port);

	id = of_match_device(msm_uartdm_table, &pdev->dev);
	if (id)
		msm_port->is_uartdm = (unsigned long)id->data;
	else
		msm_port->is_uartdm = 0;

	msm_port->clk = devm_clk_get(&pdev->dev, "core");
	if (IS_ERR(msm_port->clk))
		return PTR_ERR(msm_port->clk);

	if (msm_port->is_uartdm) {
		msm_port->pclk = devm_clk_get(&pdev->dev, "iface");
		if (IS_ERR(msm_port->pclk))
			return PTR_ERR(msm_port->pclk);
	}

	port->uartclk = clk_get_rate(msm_port->clk);
	dev_info(&pdev->dev, "uartclk = %d\n", port->uartclk);

	resource = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (unlikely(!resource))
		return -ENXIO;
	port->mapbase = resource->start;

	irq = platform_get_irq(pdev, 0);
	if (unlikely(irq < 0))
		return -ENXIO;
	port->irq = irq;

	platform_set_drvdata(pdev, port);

	return uart_add_one_port(&msm_uart_driver, port);
}

static int msm_serial_remove(struct platform_device *pdev)
{
	struct uart_port *port = platform_get_drvdata(pdev);

	uart_remove_one_port(&msm_uart_driver, port);

	return 0;
}

static const struct of_device_id msm_match_table[] = {
	{ .compatible = "qcom,msm-uart" },
	{ .compatible = "qcom,msm-uartdm" },
	{}
};
MODULE_DEVICE_TABLE(of, msm_match_table);

static int __maybe_unused msm_serial_suspend(struct device *dev)
{
	struct msm_port *port = dev_get_drvdata(dev);

	uart_suspend_port(&msm_uart_driver, &port->uart);

	return 0;
}

static int __maybe_unused msm_serial_resume(struct device *dev)
{
	struct msm_port *port = dev_get_drvdata(dev);

	uart_resume_port(&msm_uart_driver, &port->uart);

	return 0;
}

static const struct dev_pm_ops msm_serial_dev_pm_ops = {
	SET_SYSTEM_SLEEP_PM_OPS(msm_serial_suspend, msm_serial_resume)
};

static struct platform_driver msm_platform_driver = {
	.remove = msm_serial_remove,
	.probe = msm_serial_probe,
	.driver = {
		.name = "msm_serial",
		.pm = &msm_serial_dev_pm_ops,
		.of_match_table = msm_match_table,
	},
};

static int __init msm_serial_init(void)
{
	int ret;

	ret = uart_register_driver(&msm_uart_driver);
	if (unlikely(ret))
		return ret;

	ret = platform_driver_register(&msm_platform_driver);
	if (unlikely(ret))
		uart_unregister_driver(&msm_uart_driver);

	pr_info("msm_serial: driver initialized\n");

	return ret;
}

static void __exit msm_serial_exit(void)
{
	platform_driver_unregister(&msm_platform_driver);
	uart_unregister_driver(&msm_uart_driver);
}

module_init(msm_serial_init);
module_exit(msm_serial_exit);

MODULE_AUTHOR("Robert Love <rlove@google.com>");
MODULE_DESCRIPTION("Driver for msm7x serial device");
MODULE_LICENSE("GPL");