Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1297 insertions, 0 deletions

diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sprd_serial.c
new file mode 100644
index 000000000..9c7f71993
--- /dev/null
+++ b/drivers/tty/serial/sprd_serial.c
@@ -0,0 +1,1297 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2012-2015 Spreadtrum Communications Inc.
+ */
+
+#include <linux/clk.h>
+#include <linux/console.h>
+#include <linux/delay.h>
+#include <linux/dmaengine.h>
+#include <linux/dma-mapping.h>
+#include <linux/dma/sprd-dma.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/serial_core.h>
+#include <linux/serial.h>
+#include <linux/slab.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+
+/* device name */
+#define UART_NR_MAX		8
+#define SPRD_TTY_NAME		"ttyS"
+#define SPRD_FIFO_SIZE		128
+#define SPRD_DEF_RATE		26000000
+#define SPRD_BAUD_IO_LIMIT	3000000
+#define SPRD_TIMEOUT		256000
+
+/* the offset of serial registers and BITs for them */
+/* data registers */
+#define SPRD_TXD		0x0000
+#define SPRD_RXD		0x0004
+
+/* line status register and its BITs  */
+#define SPRD_LSR		0x0008
+#define SPRD_LSR_OE		BIT(4)
+#define SPRD_LSR_FE		BIT(3)
+#define SPRD_LSR_PE		BIT(2)
+#define SPRD_LSR_BI		BIT(7)
+#define SPRD_LSR_TX_OVER	BIT(15)
+
+/* data number in TX and RX fifo */
+#define SPRD_STS1		0x000C
+#define SPRD_RX_FIFO_CNT_MASK	GENMASK(7, 0)
+#define SPRD_TX_FIFO_CNT_MASK	GENMASK(15, 8)
+
+/* interrupt enable register and its BITs */
+#define SPRD_IEN		0x0010
+#define SPRD_IEN_RX_FULL	BIT(0)
+#define SPRD_IEN_TX_EMPTY	BIT(1)
+#define SPRD_IEN_BREAK_DETECT	BIT(7)
+#define SPRD_IEN_TIMEOUT	BIT(13)
+
+/* interrupt clear register */
+#define SPRD_ICLR		0x0014
+#define SPRD_ICLR_TIMEOUT	BIT(13)
+
+/* line control register */
+#define SPRD_LCR		0x0018
+#define SPRD_LCR_STOP_1BIT	0x10
+#define SPRD_LCR_STOP_2BIT	0x30
+#define SPRD_LCR_DATA_LEN	(BIT(2) | BIT(3))
+#define SPRD_LCR_DATA_LEN5	0x0
+#define SPRD_LCR_DATA_LEN6	0x4
+#define SPRD_LCR_DATA_LEN7	0x8
+#define SPRD_LCR_DATA_LEN8	0xc
+#define SPRD_LCR_PARITY		(BIT(0) | BIT(1))
+#define SPRD_LCR_PARITY_EN	0x2
+#define SPRD_LCR_EVEN_PAR	0x0
+#define SPRD_LCR_ODD_PAR	0x1
+
+/* control register 1 */
+#define SPRD_CTL1		0x001C
+#define SPRD_DMA_EN		BIT(15)
+#define SPRD_LOOPBACK_EN	BIT(14)
+#define RX_HW_FLOW_CTL_THLD	BIT(6)
+#define RX_HW_FLOW_CTL_EN	BIT(7)
+#define TX_HW_FLOW_CTL_EN	BIT(8)
+#define RX_TOUT_THLD_DEF	0x3E00
+#define RX_HFC_THLD_DEF		0x40
+
+/* fifo threshold register */
+#define SPRD_CTL2		0x0020
+#define THLD_TX_EMPTY		0x40
+#define THLD_TX_EMPTY_SHIFT	8
+#define THLD_RX_FULL		0x40
+#define THLD_RX_FULL_MASK	GENMASK(6, 0)
+
+/* config baud rate register */
+#define SPRD_CLKD0		0x0024
+#define SPRD_CLKD0_MASK		GENMASK(15, 0)
+#define SPRD_CLKD1		0x0028
+#define SPRD_CLKD1_MASK		GENMASK(20, 16)
+#define SPRD_CLKD1_SHIFT	16
+
+/* interrupt mask status register */
+#define SPRD_IMSR		0x002C
+#define SPRD_IMSR_RX_FIFO_FULL	BIT(0)
+#define SPRD_IMSR_TX_FIFO_EMPTY	BIT(1)
+#define SPRD_IMSR_BREAK_DETECT	BIT(7)
+#define SPRD_IMSR_TIMEOUT	BIT(13)
+#define SPRD_DEFAULT_SOURCE_CLK	26000000
+
+#define SPRD_RX_DMA_STEP	1
+#define SPRD_RX_FIFO_FULL	1
+#define SPRD_TX_FIFO_FULL	0x20
+#define SPRD_UART_RX_SIZE	(UART_XMIT_SIZE / 4)
+
+struct sprd_uart_dma {
+	struct dma_chan *chn;
+	unsigned char *virt;
+	dma_addr_t phys_addr;
+	dma_cookie_t cookie;
+	u32 trans_len;
+	bool enable;
+};
+
+struct sprd_uart_port {
+	struct uart_port port;
+	char name[16];
+	struct clk *clk;
+	struct sprd_uart_dma tx_dma;
+	struct sprd_uart_dma rx_dma;
+	dma_addr_t pos;
+	unsigned char *rx_buf_tail;
+};
+
+static struct sprd_uart_port *sprd_port[UART_NR_MAX];
+static int sprd_ports_num;
+
+static int sprd_start_dma_rx(struct uart_port *port);
+static int sprd_tx_dma_config(struct uart_port *port);
+
+static inline unsigned int serial_in(struct uart_port *port,
+				     unsigned int offset)
+{
+	return readl_relaxed(port->membase + offset);
+}
+
+static inline void serial_out(struct uart_port *port, unsigned int offset,
+			      int value)
+{
+	writel_relaxed(value, port->membase + offset);
+}
+
+static unsigned int sprd_tx_empty(struct uart_port *port)
+{
+	if (serial_in(port, SPRD_STS1) & SPRD_TX_FIFO_CNT_MASK)
+		return 0;
+	else
+		return TIOCSER_TEMT;
+}
+
+static unsigned int sprd_get_mctrl(struct uart_port *port)
+{
+	return TIOCM_DSR | TIOCM_CTS;
+}
+
+static void sprd_set_mctrl(struct uart_port *port, unsigned int mctrl)
+{
+	u32 val = serial_in(port, SPRD_CTL1);
+
+	if (mctrl & TIOCM_LOOP)
+		val |= SPRD_LOOPBACK_EN;
+	else
+		val &= ~SPRD_LOOPBACK_EN;
+
+	serial_out(port, SPRD_CTL1, val);
+}
+
+static void sprd_stop_rx(struct uart_port *port)
+{
+	struct sprd_uart_port *sp =
+		container_of(port, struct sprd_uart_port, port);
+	unsigned int ien, iclr;
+
+	if (sp->rx_dma.enable)
+		dmaengine_terminate_all(sp->rx_dma.chn);
+
+	iclr = serial_in(port, SPRD_ICLR);
+	ien = serial_in(port, SPRD_IEN);
+
+	ien &= ~(SPRD_IEN_RX_FULL | SPRD_IEN_BREAK_DETECT);
+	iclr |= SPRD_IEN_RX_FULL | SPRD_IEN_BREAK_DETECT;
+
+	serial_out(port, SPRD_IEN, ien);
+	serial_out(port, SPRD_ICLR, iclr);
+}
+
+static void sprd_uart_dma_enable(struct uart_port *port, bool enable)
+{
+	u32 val = serial_in(port, SPRD_CTL1);
+
+	if (enable)
+		val |= SPRD_DMA_EN;
+	else
+		val &= ~SPRD_DMA_EN;
+
+	serial_out(port, SPRD_CTL1, val);
+}
+
+static void sprd_stop_tx_dma(struct uart_port *port)
+{
+	struct sprd_uart_port *sp =
+		container_of(port, struct sprd_uart_port, port);
+	struct circ_buf *xmit = &port->state->xmit;
+	struct dma_tx_state state;
+	u32 trans_len;
+
+	dmaengine_pause(sp->tx_dma.chn);
+
+	dmaengine_tx_status(sp->tx_dma.chn, sp->tx_dma.cookie, &state);
+	if (state.residue) {
+		trans_len = state.residue - sp->tx_dma.phys_addr;
+		xmit->tail = (xmit->tail + trans_len) & (UART_XMIT_SIZE - 1);
+		port->icount.tx += trans_len;
+		dma_unmap_single(port->dev, sp->tx_dma.phys_addr,
+				 sp->tx_dma.trans_len, DMA_TO_DEVICE);
+	}
+
+	dmaengine_terminate_all(sp->tx_dma.chn);
+	sp->tx_dma.trans_len = 0;
+}
+
+static int sprd_tx_buf_remap(struct uart_port *port)
+{
+	struct sprd_uart_port *sp =
+		container_of(port, struct sprd_uart_port, port);
+	struct circ_buf *xmit = &port->state->xmit;
+
+	sp->tx_dma.trans_len =
+		CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
+
+	sp->tx_dma.phys_addr = dma_map_single(port->dev,
+					      (void *)&(xmit->buf[xmit->tail]),
+					      sp->tx_dma.trans_len,
+					      DMA_TO_DEVICE);
+	return dma_mapping_error(port->dev, sp->tx_dma.phys_addr);
+}
+
+static void sprd_complete_tx_dma(void *data)
+{
+	struct uart_port *port = (struct uart_port *)data;
+	struct sprd_uart_port *sp =
+		container_of(port, struct sprd_uart_port, port);
+	struct circ_buf *xmit = &port->state->xmit;
+	unsigned long flags;
+
+	spin_lock_irqsave(&port->lock, flags);
+	dma_unmap_single(port->dev, sp->tx_dma.phys_addr,
+			 sp->tx_dma.trans_len, DMA_TO_DEVICE);
+
+	xmit->tail = (xmit->tail + sp->tx_dma.trans_len) & (UART_XMIT_SIZE - 1);
+	port->icount.tx += sp->tx_dma.trans_len;
+
+	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+		uart_write_wakeup(port);
+
+	if (uart_circ_empty(xmit) || sprd_tx_buf_remap(port) ||
+	    sprd_tx_dma_config(port))
+		sp->tx_dma.trans_len = 0;
+
+	spin_unlock_irqrestore(&port->lock, flags);
+}
+
+static int sprd_uart_dma_submit(struct uart_port *port,
+				struct sprd_uart_dma *ud, u32 trans_len,
+				enum dma_transfer_direction direction,
+				dma_async_tx_callback callback)
+{
+	struct dma_async_tx_descriptor *dma_des;
+	unsigned long flags;
+
+	flags = SPRD_DMA_FLAGS(SPRD_DMA_CHN_MODE_NONE,
+			       SPRD_DMA_NO_TRG,
+			       SPRD_DMA_FRAG_REQ,
+			       SPRD_DMA_TRANS_INT);
+
+	dma_des = dmaengine_prep_slave_single(ud->chn, ud->phys_addr, trans_len,
+					      direction, flags);
+	if (!dma_des)
+		return -ENODEV;
+
+	dma_des->callback = callback;
+	dma_des->callback_param = port;
+
+	ud->cookie = dmaengine_submit(dma_des);
+	if (dma_submit_error(ud->cookie))
+		return dma_submit_error(ud->cookie);
+
+	dma_async_issue_pending(ud->chn);
+
+	return 0;
+}
+
+static int sprd_tx_dma_config(struct uart_port *port)
+{
+	struct sprd_uart_port *sp =
+		container_of(port, struct sprd_uart_port, port);
+	u32 burst = sp->tx_dma.trans_len > SPRD_TX_FIFO_FULL ?
+		SPRD_TX_FIFO_FULL : sp->tx_dma.trans_len;
+	int ret;
+	struct dma_slave_config cfg = {
+		.dst_addr = port->mapbase + SPRD_TXD,
+		.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
+		.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
+		.src_maxburst = burst,
+	};
+
+	ret = dmaengine_slave_config(sp->tx_dma.chn, &cfg);
+	if (ret < 0)
+		return ret;
+
+	return sprd_uart_dma_submit(port, &sp->tx_dma, sp->tx_dma.trans_len,
+				    DMA_MEM_TO_DEV, sprd_complete_tx_dma);
+}
+
+static void sprd_start_tx_dma(struct uart_port *port)
+{
+	struct sprd_uart_port *sp =
+		container_of(port, struct sprd_uart_port, port);
+	struct circ_buf *xmit = &port->state->xmit;
+
+	if (port->x_char) {
+		serial_out(port, SPRD_TXD, port->x_char);
+		port->icount.tx++;
+		port->x_char = 0;
+		return;
+	}
+
+	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
+		sprd_stop_tx_dma(port);
+		return;
+	}
+
+	if (sp->tx_dma.trans_len)
+		return;
+
+	if (sprd_tx_buf_remap(port) || sprd_tx_dma_config(port))
+		sp->tx_dma.trans_len = 0;
+}
+
+static void sprd_rx_full_thld(struct uart_port *port, u32 thld)
+{
+	u32 val = serial_in(port, SPRD_CTL2);
+
+	val &= ~THLD_RX_FULL_MASK;
+	val |= thld & THLD_RX_FULL_MASK;
+	serial_out(port, SPRD_CTL2, val);
+}
+
+static int sprd_rx_alloc_buf(struct sprd_uart_port *sp)
+{
+	sp->rx_dma.virt = dma_alloc_coherent(sp->port.dev, SPRD_UART_RX_SIZE,
+					     &sp->rx_dma.phys_addr, GFP_KERNEL);
+	if (!sp->rx_dma.virt)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static void sprd_rx_free_buf(struct sprd_uart_port *sp)
+{
+	if (sp->rx_dma.virt)
+		dma_free_coherent(sp->port.dev, SPRD_UART_RX_SIZE,
+				  sp->rx_dma.virt, sp->rx_dma.phys_addr);
+	sp->rx_dma.virt = NULL;
+}
+
+static int sprd_rx_dma_config(struct uart_port *port, u32 burst)
+{
+	struct sprd_uart_port *sp =
+		container_of(port, struct sprd_uart_port, port);
+	struct dma_slave_config cfg = {
+		.src_addr = port->mapbase + SPRD_RXD,
+		.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
+		.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
+		.src_maxburst = burst,
+	};
+
+	return dmaengine_slave_config(sp->rx_dma.chn, &cfg);
+}
+
+static void sprd_uart_dma_rx(struct uart_port *port)
+{
+	struct sprd_uart_port *sp =
+		container_of(port, struct sprd_uart_port, port);
+	struct tty_port *tty = &port->state->port;
+
+	port->icount.rx += sp->rx_dma.trans_len;
+	tty_insert_flip_string(tty, sp->rx_buf_tail, sp->rx_dma.trans_len);
+	tty_flip_buffer_push(tty);
+}
+
+static void sprd_uart_dma_irq(struct uart_port *port)
+{
+	struct sprd_uart_port *sp =
+		container_of(port, struct sprd_uart_port, port);
+	struct dma_tx_state state;
+	enum dma_status status;
+
+	status = dmaengine_tx_status(sp->rx_dma.chn,
+				     sp->rx_dma.cookie, &state);
+	if (status == DMA_ERROR)
+		sprd_stop_rx(port);
+
+	if (!state.residue && sp->pos == sp->rx_dma.phys_addr)
+		return;
+
+	if (!state.residue) {
+		sp->rx_dma.trans_len = SPRD_UART_RX_SIZE +
+			sp->rx_dma.phys_addr - sp->pos;
+		sp->pos = sp->rx_dma.phys_addr;
+	} else {
+		sp->rx_dma.trans_len = state.residue - sp->pos;
+		sp->pos = state.residue;
+	}
+
+	sprd_uart_dma_rx(port);
+	sp->rx_buf_tail += sp->rx_dma.trans_len;
+}
+
+static void sprd_complete_rx_dma(void *data)
+{
+	struct uart_port *port = (struct uart_port *)data;
+	struct sprd_uart_port *sp =
+		container_of(port, struct sprd_uart_port, port);
+	struct dma_tx_state state;
+	enum dma_status status;
+	unsigned long flags;
+
+	spin_lock_irqsave(&port->lock, flags);
+
+	status = dmaengine_tx_status(sp->rx_dma.chn,
+				     sp->rx_dma.cookie, &state);
+	if (status != DMA_COMPLETE) {
+		sprd_stop_rx(port);
+		spin_unlock_irqrestore(&port->lock, flags);
+		return;
+	}
+
+	if (sp->pos != sp->rx_dma.phys_addr) {
+		sp->rx_dma.trans_len =  SPRD_UART_RX_SIZE +
+			sp->rx_dma.phys_addr - sp->pos;
+		sprd_uart_dma_rx(port);
+		sp->rx_buf_tail += sp->rx_dma.trans_len;
+	}
+
+	if (sprd_start_dma_rx(port))
+		sprd_stop_rx(port);
+
+	spin_unlock_irqrestore(&port->lock, flags);
+}
+
+static int sprd_start_dma_rx(struct uart_port *port)
+{
+	struct sprd_uart_port *sp =
+		container_of(port, struct sprd_uart_port, port);
+	int ret;
+
+	if (!sp->rx_dma.enable)
+		return 0;
+
+	sp->pos = sp->rx_dma.phys_addr;
+	sp->rx_buf_tail = sp->rx_dma.virt;
+	sprd_rx_full_thld(port, SPRD_RX_FIFO_FULL);
+	ret = sprd_rx_dma_config(port, SPRD_RX_DMA_STEP);
+	if (ret)
+		return ret;
+
+	return sprd_uart_dma_submit(port, &sp->rx_dma, SPRD_UART_RX_SIZE,
+				    DMA_DEV_TO_MEM, sprd_complete_rx_dma);
+}
+
+static void sprd_release_dma(struct uart_port *port)
+{
+	struct sprd_uart_port *sp =
+		container_of(port, struct sprd_uart_port, port);
+
+	sprd_uart_dma_enable(port, false);
+
+	if (sp->rx_dma.enable)
+		dma_release_channel(sp->rx_dma.chn);
+
+	if (sp->tx_dma.enable)
+		dma_release_channel(sp->tx_dma.chn);
+
+	sp->tx_dma.enable = false;
+	sp->rx_dma.enable = false;
+}
+
+static void sprd_request_dma(struct uart_port *port)
+{
+	struct sprd_uart_port *sp =
+		container_of(port, struct sprd_uart_port, port);
+
+	sp->tx_dma.enable = true;
+	sp->rx_dma.enable = true;
+
+	sp->tx_dma.chn = dma_request_chan(port->dev, "tx");
+	if (IS_ERR(sp->tx_dma.chn)) {
+		dev_err(port->dev, "request TX DMA channel failed, ret = %ld\n",
+			PTR_ERR(sp->tx_dma.chn));
+		sp->tx_dma.enable = false;
+	}
+
+	sp->rx_dma.chn = dma_request_chan(port->dev, "rx");
+	if (IS_ERR(sp->rx_dma.chn)) {
+		dev_err(port->dev, "request RX DMA channel failed, ret = %ld\n",
+			PTR_ERR(sp->rx_dma.chn));
+		sp->rx_dma.enable = false;
+	}
+}
+
+static void sprd_stop_tx(struct uart_port *port)
+{
+	struct sprd_uart_port *sp = container_of(port, struct sprd_uart_port,
+						 port);
+	unsigned int ien, iclr;
+
+	if (sp->tx_dma.enable) {
+		sprd_stop_tx_dma(port);
+		return;
+	}
+
+	iclr = serial_in(port, SPRD_ICLR);
+	ien = serial_in(port, SPRD_IEN);
+
+	iclr |= SPRD_IEN_TX_EMPTY;
+	ien &= ~SPRD_IEN_TX_EMPTY;
+
+	serial_out(port, SPRD_IEN, ien);
+	serial_out(port, SPRD_ICLR, iclr);
+}
+
+static void sprd_start_tx(struct uart_port *port)
+{
+	struct sprd_uart_port *sp = container_of(port, struct sprd_uart_port,
+						 port);
+	unsigned int ien;
+
+	if (sp->tx_dma.enable) {
+		sprd_start_tx_dma(port);
+		return;
+	}
+
+	ien = serial_in(port, SPRD_IEN);
+	if (!(ien & SPRD_IEN_TX_EMPTY)) {
+		ien |= SPRD_IEN_TX_EMPTY;
+		serial_out(port, SPRD_IEN, ien);
+	}
+}
+
+/* The Sprd serial does not support this function. */
+static void sprd_break_ctl(struct uart_port *port, int break_state)
+{
+	/* nothing to do */
+}
+
+static int handle_lsr_errors(struct uart_port *port,
+			     unsigned int *flag,
+			     unsigned int *lsr)
+{
+	int ret = 0;
+
+	/* statistics */
+	if (*lsr & SPRD_LSR_BI) {
+		*lsr &= ~(SPRD_LSR_FE | SPRD_LSR_PE);
+		port->icount.brk++;
+		ret = uart_handle_break(port);
+		if (ret)
+			return ret;
+	} else if (*lsr & SPRD_LSR_PE)
+		port->icount.parity++;
+	else if (*lsr & SPRD_LSR_FE)
+		port->icount.frame++;
+	if (*lsr & SPRD_LSR_OE)
+		port->icount.overrun++;
+
+	/* mask off conditions which should be ignored */
+	*lsr &= port->read_status_mask;
+	if (*lsr & SPRD_LSR_BI)
+		*flag = TTY_BREAK;
+	else if (*lsr & SPRD_LSR_PE)
+		*flag = TTY_PARITY;
+	else if (*lsr & SPRD_LSR_FE)
+		*flag = TTY_FRAME;
+
+	return ret;
+}
+
+static inline void sprd_rx(struct uart_port *port)
+{
+	struct sprd_uart_port *sp = container_of(port, struct sprd_uart_port,
+						 port);
+	struct tty_port *tty = &port->state->port;
+	unsigned int ch, flag, lsr, max_count = SPRD_TIMEOUT;
+
+	if (sp->rx_dma.enable) {
+		sprd_uart_dma_irq(port);
+		return;
+	}
+
+	while ((serial_in(port, SPRD_STS1) & SPRD_RX_FIFO_CNT_MASK) &&
+	       max_count--) {
+		lsr = serial_in(port, SPRD_LSR);
+		ch = serial_in(port, SPRD_RXD);
+		flag = TTY_NORMAL;
+		port->icount.rx++;
+
+		if (lsr & (SPRD_LSR_BI | SPRD_LSR_PE |
+			   SPRD_LSR_FE | SPRD_LSR_OE))
+			if (handle_lsr_errors(port, &flag, &lsr))
+				continue;
+		if (uart_handle_sysrq_char(port, ch))
+			continue;
+
+		uart_insert_char(port, lsr, SPRD_LSR_OE, ch, flag);
+	}
+
+	tty_flip_buffer_push(tty);
+}
+
+static inline void sprd_tx(struct uart_port *port)
+{
+	struct circ_buf *xmit = &port->state->xmit;
+	int count;
+
+	if (port->x_char) {
+		serial_out(port, SPRD_TXD, port->x_char);
+		port->icount.tx++;
+		port->x_char = 0;
+		return;
+	}
+
+	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
+		sprd_stop_tx(port);
+		return;
+	}
+
+	count = THLD_TX_EMPTY;
+	do {
+		serial_out(port, SPRD_TXD, xmit->buf[xmit->tail]);
+		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
+		port->icount.tx++;
+		if (uart_circ_empty(xmit))
+			break;
+	} while (--count > 0);
+
+	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+		uart_write_wakeup(port);
+
+	if (uart_circ_empty(xmit))
+		sprd_stop_tx(port);
+}
+
+/* this handles the interrupt from one port */
+static irqreturn_t sprd_handle_irq(int irq, void *dev_id)
+{
+	struct uart_port *port = dev_id;
+	unsigned int ims;
+
+	spin_lock(&port->lock);
+
+	ims = serial_in(port, SPRD_IMSR);
+
+	if (!ims) {
+		spin_unlock(&port->lock);
+		return IRQ_NONE;
+	}
+
+	if (ims & SPRD_IMSR_TIMEOUT)
+		serial_out(port, SPRD_ICLR, SPRD_ICLR_TIMEOUT);
+
+	if (ims & SPRD_IMSR_BREAK_DETECT)
+		serial_out(port, SPRD_ICLR, SPRD_IMSR_BREAK_DETECT);
+
+	if (ims & (SPRD_IMSR_RX_FIFO_FULL | SPRD_IMSR_BREAK_DETECT |
+		   SPRD_IMSR_TIMEOUT))
+		sprd_rx(port);
+
+	if (ims & SPRD_IMSR_TX_FIFO_EMPTY)
+		sprd_tx(port);
+
+	spin_unlock(&port->lock);
+
+	return IRQ_HANDLED;
+}
+
+static void sprd_uart_dma_startup(struct uart_port *port,
+				  struct sprd_uart_port *sp)
+{
+	int ret;
+
+	sprd_request_dma(port);
+	if (!(sp->rx_dma.enable || sp->tx_dma.enable))
+		return;
+
+	ret = sprd_start_dma_rx(port);
+	if (ret) {
+		sp->rx_dma.enable = false;
+		dma_release_channel(sp->rx_dma.chn);
+		dev_warn(port->dev, "fail to start RX dma mode\n");
+	}
+
+	sprd_uart_dma_enable(port, true);
+}
+
+static int sprd_startup(struct uart_port *port)
+{
+	int ret = 0;
+	unsigned int ien, fc;
+	unsigned int timeout;
+	struct sprd_uart_port *sp;
+	unsigned long flags;
+
+	serial_out(port, SPRD_CTL2,
+		   THLD_TX_EMPTY << THLD_TX_EMPTY_SHIFT | THLD_RX_FULL);
+
+	/* clear rx fifo */
+	timeout = SPRD_TIMEOUT;
+	while (timeout-- && serial_in(port, SPRD_STS1) & SPRD_RX_FIFO_CNT_MASK)
+		serial_in(port, SPRD_RXD);
+
+	/* clear tx fifo */
+	timeout = SPRD_TIMEOUT;
+	while (timeout-- && serial_in(port, SPRD_STS1) & SPRD_TX_FIFO_CNT_MASK)
+		cpu_relax();
+
+	/* clear interrupt */
+	serial_out(port, SPRD_IEN, 0);
+	serial_out(port, SPRD_ICLR, ~0);
+
+	/* allocate irq */
+	sp = container_of(port, struct sprd_uart_port, port);
+	snprintf(sp->name, sizeof(sp->name), "sprd_serial%d", port->line);
+
+	sprd_uart_dma_startup(port, sp);
+
+	ret = devm_request_irq(port->dev, port->irq, sprd_handle_irq,
+			       IRQF_SHARED, sp->name, port);
+	if (ret) {
+		dev_err(port->dev, "fail to request serial irq %d, ret=%d\n",
+			port->irq, ret);
+		return ret;
+	}
+	fc = serial_in(port, SPRD_CTL1);
+	fc |= RX_TOUT_THLD_DEF | RX_HFC_THLD_DEF;
+	serial_out(port, SPRD_CTL1, fc);
+
+	/* enable interrupt */
+	spin_lock_irqsave(&port->lock, flags);
+	ien = serial_in(port, SPRD_IEN);
+	ien |= SPRD_IEN_BREAK_DETECT | SPRD_IEN_TIMEOUT;
+	if (!sp->rx_dma.enable)
+		ien |= SPRD_IEN_RX_FULL;
+	serial_out(port, SPRD_IEN, ien);
+	spin_unlock_irqrestore(&port->lock, flags);
+
+	return 0;
+}
+
+static void sprd_shutdown(struct uart_port *port)
+{
+	sprd_release_dma(port);
+	serial_out(port, SPRD_IEN, 0);
+	serial_out(port, SPRD_ICLR, ~0);
+	devm_free_irq(port->dev, port->irq, port);
+}
+
+static void sprd_set_termios(struct uart_port *port, struct ktermios *termios,
+		             const struct ktermios *old)
+{
+	unsigned int baud, quot;
+	unsigned int lcr = 0, fc;
+	unsigned long flags;
+
+	/* ask the core to calculate the divisor for us */
+	baud = uart_get_baud_rate(port, termios, old, 0, SPRD_BAUD_IO_LIMIT);
+
+	quot = port->uartclk / baud;
+
+	/* set data length */
+	switch (termios->c_cflag & CSIZE) {
+	case CS5:
+		lcr |= SPRD_LCR_DATA_LEN5;
+		break;
+	case CS6:
+		lcr |= SPRD_LCR_DATA_LEN6;
+		break;
+	case CS7:
+		lcr |= SPRD_LCR_DATA_LEN7;
+		break;
+	case CS8:
+	default:
+		lcr |= SPRD_LCR_DATA_LEN8;
+		break;
+	}
+
+	/* calculate stop bits */
+	lcr &= ~(SPRD_LCR_STOP_1BIT | SPRD_LCR_STOP_2BIT);
+	if (termios->c_cflag & CSTOPB)
+		lcr |= SPRD_LCR_STOP_2BIT;
+	else
+		lcr |= SPRD_LCR_STOP_1BIT;
+
+	/* calculate parity */
+	lcr &= ~SPRD_LCR_PARITY;
+	termios->c_cflag &= ~CMSPAR;	/* no support mark/space */
+	if (termios->c_cflag & PARENB) {
+		lcr |= SPRD_LCR_PARITY_EN;
+		if (termios->c_cflag & PARODD)
+			lcr |= SPRD_LCR_ODD_PAR;
+		else
+			lcr |= SPRD_LCR_EVEN_PAR;
+	}
+
+	spin_lock_irqsave(&port->lock, flags);
+
+	/* update the per-port timeout */
+	uart_update_timeout(port, termios->c_cflag, baud);
+
+	port->read_status_mask = SPRD_LSR_OE;
+	if (termios->c_iflag & INPCK)
+		port->read_status_mask |= SPRD_LSR_FE | SPRD_LSR_PE;
+	if (termios->c_iflag & (IGNBRK | BRKINT | PARMRK))
+		port->read_status_mask |= SPRD_LSR_BI;
+
+	/* characters to ignore */
+	port->ignore_status_mask = 0;
+	if (termios->c_iflag & IGNPAR)
+		port->ignore_status_mask |= SPRD_LSR_PE | SPRD_LSR_FE;
+	if (termios->c_iflag & IGNBRK) {
+		port->ignore_status_mask |= SPRD_LSR_BI;
+		/*
+		 * If we're ignoring parity and break indicators,
+		 * ignore overruns too (for real raw support).
+		 */
+		if (termios->c_iflag & IGNPAR)
+			port->ignore_status_mask |= SPRD_LSR_OE;
+	}
+
+	/* flow control */
+	fc = serial_in(port, SPRD_CTL1);
+	fc &= ~(RX_HW_FLOW_CTL_THLD | RX_HW_FLOW_CTL_EN | TX_HW_FLOW_CTL_EN);
+	if (termios->c_cflag & CRTSCTS) {
+		fc |= RX_HW_FLOW_CTL_THLD;
+		fc |= RX_HW_FLOW_CTL_EN;
+		fc |= TX_HW_FLOW_CTL_EN;
+	}
+
+	/* clock divider bit0~bit15 */
+	serial_out(port, SPRD_CLKD0, quot & SPRD_CLKD0_MASK);
+
+	/* clock divider bit16~bit20 */
+	serial_out(port, SPRD_CLKD1,
+		   (quot & SPRD_CLKD1_MASK) >> SPRD_CLKD1_SHIFT);
+	serial_out(port, SPRD_LCR, lcr);
+	fc |= RX_TOUT_THLD_DEF | RX_HFC_THLD_DEF;
+	serial_out(port, SPRD_CTL1, fc);
+
+	spin_unlock_irqrestore(&port->lock, flags);
+
+	/* Don't rewrite B0 */
+	if (tty_termios_baud_rate(termios))
+		tty_termios_encode_baud_rate(termios, baud, baud);
+}
+
+static const char *sprd_type(struct uart_port *port)
+{
+	return "SPX";
+}
+
+static void sprd_release_port(struct uart_port *port)
+{
+	/* nothing to do */
+}
+
+static int sprd_request_port(struct uart_port *port)
+{
+	return 0;
+}
+
+static void sprd_config_port(struct uart_port *port, int flags)
+{
+	if (flags & UART_CONFIG_TYPE)
+		port->type = PORT_SPRD;
+}
+
+static int sprd_verify_port(struct uart_port *port, struct serial_struct *ser)
+{
+	if (ser->type != PORT_SPRD)
+		return -EINVAL;
+	if (port->irq != ser->irq)
+		return -EINVAL;
+	if (port->iotype != ser->io_type)
+		return -EINVAL;
+	return 0;
+}
+
+static void sprd_pm(struct uart_port *port, unsigned int state,
+		unsigned int oldstate)
+{
+	struct sprd_uart_port *sup =
+		container_of(port, struct sprd_uart_port, port);
+
+	switch (state) {
+	case UART_PM_STATE_ON:
+		clk_prepare_enable(sup->clk);
+		break;
+	case UART_PM_STATE_OFF:
+		clk_disable_unprepare(sup->clk);
+		break;
+	}
+}
+
+#ifdef CONFIG_CONSOLE_POLL
+static int sprd_poll_init(struct uart_port *port)
+{
+	if (port->state->pm_state != UART_PM_STATE_ON) {
+		sprd_pm(port, UART_PM_STATE_ON, 0);
+		port->state->pm_state = UART_PM_STATE_ON;
+	}
+
+	return 0;
+}
+
+static int sprd_poll_get_char(struct uart_port *port)
+{
+	while (!(serial_in(port, SPRD_STS1) & SPRD_RX_FIFO_CNT_MASK))
+		cpu_relax();
+
+	return serial_in(port, SPRD_RXD);
+}
+
+static void sprd_poll_put_char(struct uart_port *port, unsigned char ch)
+{
+	while (serial_in(port, SPRD_STS1) & SPRD_TX_FIFO_CNT_MASK)
+		cpu_relax();
+
+	serial_out(port, SPRD_TXD, ch);
+}
+#endif
+
+static const struct uart_ops serial_sprd_ops = {
+	.tx_empty = sprd_tx_empty,
+	.get_mctrl = sprd_get_mctrl,
+	.set_mctrl = sprd_set_mctrl,
+	.stop_tx = sprd_stop_tx,
+	.start_tx = sprd_start_tx,
+	.stop_rx = sprd_stop_rx,
+	.break_ctl = sprd_break_ctl,
+	.startup = sprd_startup,
+	.shutdown = sprd_shutdown,
+	.set_termios = sprd_set_termios,
+	.type = sprd_type,
+	.release_port = sprd_release_port,
+	.request_port = sprd_request_port,
+	.config_port = sprd_config_port,
+	.verify_port = sprd_verify_port,
+	.pm = sprd_pm,
+#ifdef CONFIG_CONSOLE_POLL
+	.poll_init	= sprd_poll_init,
+	.poll_get_char	= sprd_poll_get_char,
+	.poll_put_char	= sprd_poll_put_char,
+#endif
+};
+
+#ifdef CONFIG_SERIAL_SPRD_CONSOLE
+static void wait_for_xmitr(struct uart_port *port)
+{
+	unsigned int status, tmout = 10000;
+
+	/* wait up to 10ms for the character(s) to be sent */
+	do {
+		status = serial_in(port, SPRD_STS1);
+		if (--tmout == 0)
+			break;
+		udelay(1);
+	} while (status & SPRD_TX_FIFO_CNT_MASK);
+}
+
+static void sprd_console_putchar(struct uart_port *port, unsigned char ch)
+{
+	wait_for_xmitr(port);
+	serial_out(port, SPRD_TXD, ch);
+}
+
+static void sprd_console_write(struct console *co, const char *s,
+			       unsigned int count)
+{
+	struct uart_port *port = &sprd_port[co->index]->port;
+	int locked = 1;
+	unsigned long flags;
+
+	if (port->sysrq)
+		locked = 0;
+	else if (oops_in_progress)
+		locked = spin_trylock_irqsave(&port->lock, flags);
+	else
+		spin_lock_irqsave(&port->lock, flags);
+
+	uart_console_write(port, s, count, sprd_console_putchar);
+
+	/* wait for transmitter to become empty */
+	wait_for_xmitr(port);
+
+	if (locked)
+		spin_unlock_irqrestore(&port->lock, flags);
+}
+
+static int sprd_console_setup(struct console *co, char *options)
+{
+	struct sprd_uart_port *sprd_uart_port;
+	int baud = 115200;
+	int bits = 8;
+	int parity = 'n';
+	int flow = 'n';
+
+	if (co->index >= UART_NR_MAX || co->index < 0)
+		co->index = 0;
+
+	sprd_uart_port = sprd_port[co->index];
+	if (!sprd_uart_port || !sprd_uart_port->port.membase) {
+		pr_info("serial port %d not yet initialized\n", co->index);
+		return -ENODEV;
+	}
+
+	if (options)
+		uart_parse_options(options, &baud, &parity, &bits, &flow);
+
+	return uart_set_options(&sprd_uart_port->port, co, baud,
+				parity, bits, flow);
+}
+
+static struct uart_driver sprd_uart_driver;
+static struct console sprd_console = {
+	.name = SPRD_TTY_NAME,
+	.write = sprd_console_write,
+	.device = uart_console_device,
+	.setup = sprd_console_setup,
+	.flags = CON_PRINTBUFFER,
+	.index = -1,
+	.data = &sprd_uart_driver,
+};
+
+static int __init sprd_serial_console_init(void)
+{
+	register_console(&sprd_console);
+	return 0;
+}
+console_initcall(sprd_serial_console_init);
+
+#define SPRD_CONSOLE	(&sprd_console)
+
+/* Support for earlycon */
+static void sprd_putc(struct uart_port *port, unsigned char c)
+{
+	unsigned int timeout = SPRD_TIMEOUT;
+
+	while (timeout-- &&
+	       !(readl(port->membase + SPRD_LSR) & SPRD_LSR_TX_OVER))
+		cpu_relax();
+
+	writeb(c, port->membase + SPRD_TXD);
+}
+
+static void sprd_early_write(struct console *con, const char *s, unsigned int n)
+{
+	struct earlycon_device *dev = con->data;
+
+	uart_console_write(&dev->port, s, n, sprd_putc);
+}
+
+static int __init sprd_early_console_setup(struct earlycon_device *device,
+					   const char *opt)
+{
+	if (!device->port.membase)
+		return -ENODEV;
+
+	device->con->write = sprd_early_write;
+	return 0;
+}
+OF_EARLYCON_DECLARE(sprd_serial, "sprd,sc9836-uart",
+		    sprd_early_console_setup);
+
+#else /* !CONFIG_SERIAL_SPRD_CONSOLE */
+#define SPRD_CONSOLE		NULL
+#endif
+
+static struct uart_driver sprd_uart_driver = {
+	.owner = THIS_MODULE,
+	.driver_name = "sprd_serial",
+	.dev_name = SPRD_TTY_NAME,
+	.major = 0,
+	.minor = 0,
+	.nr = UART_NR_MAX,
+	.cons = SPRD_CONSOLE,
+};
+
+static int sprd_remove(struct platform_device *dev)
+{
+	struct sprd_uart_port *sup = platform_get_drvdata(dev);
+
+	if (sup) {
+		uart_remove_one_port(&sprd_uart_driver, &sup->port);
+		sprd_port[sup->port.line] = NULL;
+		sprd_rx_free_buf(sup);
+		sprd_ports_num--;
+	}
+
+	if (!sprd_ports_num)
+		uart_unregister_driver(&sprd_uart_driver);
+
+	return 0;
+}
+
+static bool sprd_uart_is_console(struct uart_port *uport)
+{
+	struct console *cons = sprd_uart_driver.cons;
+
+	if ((cons && cons->index >= 0 && cons->index == uport->line) ||
+	    of_console_check(uport->dev->of_node, SPRD_TTY_NAME, uport->line))
+		return true;
+
+	return false;
+}
+
+static int sprd_clk_init(struct uart_port *uport)
+{
+	struct clk *clk_uart, *clk_parent;
+	struct sprd_uart_port *u = container_of(uport, struct sprd_uart_port, port);
+
+	clk_uart = devm_clk_get(uport->dev, "uart");
+	if (IS_ERR(clk_uart)) {
+		dev_warn(uport->dev, "uart%d can't get uart clock\n",
+			 uport->line);
+		clk_uart = NULL;
+	}
+
+	clk_parent = devm_clk_get(uport->dev, "source");
+	if (IS_ERR(clk_parent)) {
+		dev_warn(uport->dev, "uart%d can't get source clock\n",
+			 uport->line);
+		clk_parent = NULL;
+	}
+
+	if (!clk_uart || clk_set_parent(clk_uart, clk_parent))
+		uport->uartclk = SPRD_DEFAULT_SOURCE_CLK;
+	else
+		uport->uartclk = clk_get_rate(clk_uart);
+
+	u->clk = devm_clk_get(uport->dev, "enable");
+	if (IS_ERR(u->clk)) {
+		if (PTR_ERR(u->clk) == -EPROBE_DEFER)
+			return -EPROBE_DEFER;
+
+		dev_warn(uport->dev, "uart%d can't get enable clock\n",
+			uport->line);
+
+		/* To keep console alive even if the error occurred */
+		if (!sprd_uart_is_console(uport))
+			return PTR_ERR(u->clk);
+
+		u->clk = NULL;
+	}
+
+	return 0;
+}
+
+static int sprd_probe(struct platform_device *pdev)
+{
+	struct resource *res;
+	struct uart_port *up;
+	struct sprd_uart_port *sport;
+	int irq;
+	int index;
+	int ret;
+
+	index = of_alias_get_id(pdev->dev.of_node, "serial");
+	if (index < 0 || index >= UART_NR_MAX) {
+		dev_err(&pdev->dev, "got a wrong serial alias id %d\n", index);
+		return -EINVAL;
+	}
+
+	sport = devm_kzalloc(&pdev->dev, sizeof(*sport), GFP_KERNEL);
+	if (!sport)
+		return -ENOMEM;
+
+	up = &sport->port;
+	up->dev = &pdev->dev;
+	up->line = index;
+	up->type = PORT_SPRD;
+	up->iotype = UPIO_MEM;
+	up->uartclk = SPRD_DEF_RATE;
+	up->fifosize = SPRD_FIFO_SIZE;
+	up->ops = &serial_sprd_ops;
+	up->flags = UPF_BOOT_AUTOCONF;
+	up->has_sysrq = IS_ENABLED(CONFIG_SERIAL_SPRD_CONSOLE);
+
+	ret = sprd_clk_init(up);
+	if (ret)
+		return ret;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	up->membase = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(up->membase))
+		return PTR_ERR(up->membase);
+
+	up->mapbase = res->start;
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+	up->irq = irq;
+
+	/*
+	 * Allocate one dma buffer to prepare for receive transfer, in case
+	 * memory allocation failure at runtime.
+	 */
+	ret = sprd_rx_alloc_buf(sport);
+	if (ret)
+		return ret;
+
+	if (!sprd_ports_num) {
+		ret = uart_register_driver(&sprd_uart_driver);
+		if (ret < 0) {
+			pr_err("Failed to register SPRD-UART driver\n");
+			goto free_rx_buf;
+		}
+	}
+
+	sprd_ports_num++;
+	sprd_port[index] = sport;
+
+	ret = uart_add_one_port(&sprd_uart_driver, up);
+	if (ret)
+		goto clean_port;
+
+	platform_set_drvdata(pdev, up);
+
+	return 0;
+
+clean_port:
+	sprd_port[index] = NULL;
+	if (--sprd_ports_num == 0)
+		uart_unregister_driver(&sprd_uart_driver);
+free_rx_buf:
+	sprd_rx_free_buf(sport);
+	return ret;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int sprd_suspend(struct device *dev)
+{
+	struct sprd_uart_port *sup = dev_get_drvdata(dev);
+
+	uart_suspend_port(&sprd_uart_driver, &sup->port);
+
+	return 0;
+}
+
+static int sprd_resume(struct device *dev)
+{
+	struct sprd_uart_port *sup = dev_get_drvdata(dev);
+
+	uart_resume_port(&sprd_uart_driver, &sup->port);
+
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(sprd_pm_ops, sprd_suspend, sprd_resume);
+
+static const struct of_device_id serial_ids[] = {
+	{.compatible = "sprd,sc9836-uart",},
+	{}
+};
+MODULE_DEVICE_TABLE(of, serial_ids);
+
+static struct platform_driver sprd_platform_driver = {
+	.probe		= sprd_probe,
+	.remove		= sprd_remove,
+	.driver		= {
+		.name	= "sprd_serial",
+		.of_match_table = of_match_ptr(serial_ids),
+		.pm	= &sprd_pm_ops,
+	},
+};
+
+module_platform_driver(sprd_platform_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Spreadtrum SoC serial driver series");