[v6,2/2] serial: 8250: Add new 8250-core based Broadcom STB driver

diff --git a/MAINTAINERS b/MAINTAINERS
index aa84121c5611..f2173c8fa4fa 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3558,6 +3558,14 @@  S:	Supported
 F:	Documentation/devicetree/bindings/i2c/brcm,brcmstb-i2c.yaml
 F:	drivers/i2c/busses/i2c-brcmstb.c
 
+BROADCOM BRCMSTB UART DRIVER
+M:	Al Cooper <alcooperx@gmail.com>
+L:	linux-serial@vger.kernel.org
+L:	bcm-kernel-feedback-list@broadcom.com
+S:	Maintained
+F:	Documentation/devicetree/bindings/serial/brcm,bcm7271-uart.yaml
+F:	drivers/tty/serial/8250/8250_bcm7271.c
+
 BROADCOM BRCMSTB USB EHCI DRIVER
 M:	Al Cooper <alcooperx@gmail.com>
 L:	linux-usb@vger.kernel.org
diff --git a/drivers/tty/serial/8250/8250_bcm7271.c b/drivers/tty/serial/8250/8250_bcm7271.c
new file mode 100644
index 000000000000..63883185fccd
--- /dev/null
+++ b/drivers/tty/serial/8250/8250_bcm7271.c
@@ -0,0 +1,1202 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2020, Broadcom */
+/*
+ * 8250-core based driver for Broadcom ns16550a UARTs
+ *
+ * This driver uses the standard 8250 driver core but adds additional
+ * optional features including the ability to use a baud rate clock
+ * mux for more accurate high speed baud rate selection and also
+ * an optional DMA engine.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/tty.h>
+#include <linux/errno.h>
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/dma-mapping.h>
+#include <linux/tty_flip.h>
+#include <linux/delay.h>
+#include <linux/clk.h>
+#include <linux/debugfs.h>
+
+#include "8250.h"
+
+/* Register definitions for UART DMA block. Version 1.1 or later. */
+#define UDMA_ARB_RX		0x00
+#define UDMA_ARB_TX		0x04
+#define		UDMA_ARB_REQ				0x00000001
+#define		UDMA_ARB_GRANT				0x00000002
+
+#define UDMA_RX_REVISION	0x00
+#define UDMA_RX_REVISION_REQUIRED			0x00000101
+#define UDMA_RX_CTRL		0x04
+#define		UDMA_RX_CTRL_BUF_CLOSE_MODE		0x00010000
+#define		UDMA_RX_CTRL_MASK_WR_DONE		0x00008000
+#define		UDMA_RX_CTRL_ENDIAN_OVERRIDE		0x00004000
+#define		UDMA_RX_CTRL_ENDIAN			0x00002000
+#define		UDMA_RX_CTRL_OE_IS_ERR			0x00001000
+#define		UDMA_RX_CTRL_PE_IS_ERR			0x00000800
+#define		UDMA_RX_CTRL_FE_IS_ERR			0x00000400
+#define		UDMA_RX_CTRL_NUM_BUF_USED_MASK		0x000003c0
+#define		UDMA_RX_CTRL_NUM_BUF_USED_SHIFT	6
+#define		UDMA_RX_CTRL_BUF_CLOSE_CLK_SEL_SYS	0x00000020
+#define		UDMA_RX_CTRL_BUF_CLOSE_ENA		0x00000010
+#define		UDMA_RX_CTRL_TIMEOUT_CLK_SEL_SYS	0x00000008
+#define		UDMA_RX_CTRL_TIMEOUT_ENA		0x00000004
+#define		UDMA_RX_CTRL_ABORT			0x00000002
+#define		UDMA_RX_CTRL_ENA			0x00000001
+#define UDMA_RX_STATUS		0x08
+#define		UDMA_RX_STATUS_ACTIVE_BUF_MASK		0x0000000f
+#define UDMA_RX_TRANSFER_LEN	0x0c
+#define UDMA_RX_TRANSFER_TOTAL	0x10
+#define UDMA_RX_BUFFER_SIZE	0x14
+#define UDMA_RX_SRC_ADDR	0x18
+#define UDMA_RX_TIMEOUT		0x1c
+#define UDMA_RX_BUFFER_CLOSE	0x20
+#define UDMA_RX_BLOCKOUT_COUNTER 0x24
+#define UDMA_RX_BUF0_PTR_LO	0x28
+#define UDMA_RX_BUF0_PTR_HI	0x2c
+#define UDMA_RX_BUF0_STATUS	0x30
+#define		UDMA_RX_BUFX_STATUS_OVERRUN_ERR		0x00000010
+#define		UDMA_RX_BUFX_STATUS_FRAME_ERR		0x00000008
+#define		UDMA_RX_BUFX_STATUS_PARITY_ERR		0x00000004
+#define		UDMA_RX_BUFX_STATUS_CLOSE_EXPIRED	0x00000002
+#define		UDMA_RX_BUFX_STATUS_DATA_RDY		0x00000001
+#define UDMA_RX_BUF0_DATA_LEN	0x34
+#define UDMA_RX_BUF1_PTR_LO	0x38
+#define UDMA_RX_BUF1_PTR_HI	0x3c
+#define UDMA_RX_BUF1_STATUS	0x40
+#define UDMA_RX_BUF1_DATA_LEN	0x44
+
+#define UDMA_TX_REVISION	0x00
+#define UDMA_TX_REVISION_REQUIRED			0x00000101
+#define UDMA_TX_CTRL		0x04
+#define		UDMA_TX_CTRL_ENDIAN_OVERRIDE		0x00000080
+#define		UDMA_TX_CTRL_ENDIAN			0x00000040
+#define		UDMA_TX_CTRL_NUM_BUF_USED_MASK		0x00000030
+#define		UDMA_TX_CTRL_NUM_BUF_USED_1		0x00000010
+#define		UDMA_TX_CTRL_ABORT			0x00000002
+#define		UDMA_TX_CTRL_ENA			0x00000001
+#define UDMA_TX_DST_ADDR	0x08
+#define UDMA_TX_BLOCKOUT_COUNTER 0x10
+#define UDMA_TX_TRANSFER_LEN	0x14
+#define UDMA_TX_TRANSFER_TOTAL	0x18
+#define UDMA_TX_STATUS		0x20
+#define UDMA_TX_BUF0_PTR_LO	0x24
+#define UDMA_TX_BUF0_PTR_HI	0x28
+#define UDMA_TX_BUF0_STATUS	0x2c
+#define		UDMA_TX_BUFX_LAST			0x00000002
+#define		UDMA_TX_BUFX_EMPTY			0x00000001
+#define UDMA_TX_BUF0_DATA_LEN	0x30
+#define UDMA_TX_BUF0_DATA_SENT	0x34
+#define UDMA_TX_BUF1_PTR_LO	0x38
+
+#define UDMA_INTR_STATUS	0x00
+#define		UDMA_INTR_ARB_TX_GRANT			0x00040000
+#define		UDMA_INTR_ARB_RX_GRANT			0x00020000
+#define		UDMA_INTR_TX_ALL_EMPTY			0x00010000
+#define		UDMA_INTR_TX_EMPTY_BUF1			0x00008000
+#define		UDMA_INTR_TX_EMPTY_BUF0			0x00004000
+#define		UDMA_INTR_TX_ABORT			0x00002000
+#define		UDMA_INTR_TX_DONE			0x00001000
+#define		UDMA_INTR_RX_ERROR			0x00000800
+#define		UDMA_INTR_RX_TIMEOUT			0x00000400
+#define		UDMA_INTR_RX_READY_BUF7			0x00000200
+#define		UDMA_INTR_RX_READY_BUF6			0x00000100
+#define		UDMA_INTR_RX_READY_BUF5			0x00000080
+#define		UDMA_INTR_RX_READY_BUF4			0x00000040
+#define		UDMA_INTR_RX_READY_BUF3			0x00000020
+#define		UDMA_INTR_RX_READY_BUF2			0x00000010
+#define		UDMA_INTR_RX_READY_BUF1			0x00000008
+#define		UDMA_INTR_RX_READY_BUF0			0x00000004
+#define		UDMA_INTR_RX_READY_MASK			0x000003fc
+#define		UDMA_INTR_RX_READY_SHIFT		2
+#define		UDMA_INTR_RX_ABORT			0x00000002
+#define		UDMA_INTR_RX_DONE			0x00000001
+#define UDMA_INTR_SET		0x04
+#define UDMA_INTR_CLEAR		0x08
+#define UDMA_INTR_MASK_STATUS	0x0c
+#define UDMA_INTR_MASK_SET	0x10
+#define UDMA_INTR_MASK_CLEAR	0x14
+
+
+#define UDMA_RX_INTERRUPTS ( \
+	UDMA_INTR_RX_ERROR | \
+	UDMA_INTR_RX_TIMEOUT | \
+	UDMA_INTR_RX_READY_BUF0 | \
+	UDMA_INTR_RX_READY_BUF1 | \
+	UDMA_INTR_RX_READY_BUF2 | \
+	UDMA_INTR_RX_READY_BUF3 | \
+	UDMA_INTR_RX_READY_BUF4 | \
+	UDMA_INTR_RX_READY_BUF5 | \
+	UDMA_INTR_RX_READY_BUF6 | \
+	UDMA_INTR_RX_READY_BUF7 | \
+	UDMA_INTR_RX_ABORT | \
+	UDMA_INTR_RX_DONE)
+
+#define UDMA_RX_ERR_INTERRUPTS ( \
+	UDMA_INTR_RX_ERROR | \
+	UDMA_INTR_RX_TIMEOUT | \
+	UDMA_INTR_RX_ABORT | \
+	UDMA_INTR_RX_DONE)
+
+#define UDMA_TX_INTERRUPTS ( \
+	UDMA_INTR_TX_ABORT | \
+	UDMA_INTR_TX_DONE)
+
+#define UDMA_IS_RX_INTERRUPT(status) ((status) & UDMA_RX_INTERRUPTS)
+#define UDMA_IS_TX_INTERRUPT(status) ((status) & UDMA_TX_INTERRUPTS)
+
+
+/* Current devices have 8 sets of RX buffer registers */
+#define UDMA_RX_BUFS_COUNT	8
+#define UDMA_RX_BUFS_REG_OFFSET (UDMA_RX_BUF1_PTR_LO - UDMA_RX_BUF0_PTR_LO)
+#define UDMA_RX_BUFx_PTR_LO(x)	(UDMA_RX_BUF0_PTR_LO + \
+				 ((x) * UDMA_RX_BUFS_REG_OFFSET))
+#define UDMA_RX_BUFx_PTR_HI(x)	(UDMA_RX_BUF0_PTR_HI + \
+				 ((x) * UDMA_RX_BUFS_REG_OFFSET))
+#define UDMA_RX_BUFx_STATUS(x)	(UDMA_RX_BUF0_STATUS + \
+				 ((x) * UDMA_RX_BUFS_REG_OFFSET))
+#define UDMA_RX_BUFx_DATA_LEN(x) (UDMA_RX_BUF0_DATA_LEN + \
+				  ((x) * UDMA_RX_BUFS_REG_OFFSET))
+
+/* Current devices have 2 sets of TX buffer registers */
+#define UDMA_TX_BUFS_COUNT	2
+#define UDMA_TX_BUFS_REG_OFFSET (UDMA_TX_BUF1_PTR_LO - UDMA_TX_BUF0_PTR_LO)
+#define UDMA_TX_BUFx_PTR_LO(x)	(UDMA_TX_BUF0_PTR_LO + \
+				 ((x) * UDMA_TX_BUFS_REG_OFFSET))
+#define UDMA_TX_BUFx_PTR_HI(x)	(UDMA_TX_BUF0_PTR_HI + \
+				 ((x) * UDMA_TX_BUFS_REG_OFFSET))
+#define UDMA_TX_BUFx_STATUS(x)	(UDMA_TX_BUF0_STATUS + \
+				 ((x) * UDMA_TX_BUFS_REG_OFFSET))
+#define UDMA_TX_BUFx_DATA_LEN(x) (UDMA_TX_BUF0_DATA_LEN + \
+				  ((x) * UDMA_TX_BUFS_REG_OFFSET))
+#define UDMA_TX_BUFx_DATA_SENT(x) (UDMA_TX_BUF0_DATA_SENT + \
+				   ((x) * UDMA_TX_BUFS_REG_OFFSET))
+#define REGS_8250 0
+#define REGS_DMA_RX 1
+#define REGS_DMA_TX 2
+#define REGS_DMA_ISR 3
+#define REGS_DMA_ARB 4
+#define REGS_MAX 5
+
+#define TX_BUF_SIZE 4096
+#define RX_BUF_SIZE 4096
+#define RX_BUFS_COUNT 2
+#define KHZ    1000
+#define MHZ(x) ((x) * KHZ * KHZ)
+
+static const u32 brcmstb_rate_table[] = {
+	MHZ(81),
+	MHZ(108),
+	MHZ(64),		/* Actually 64285715 for some chips */
+	MHZ(48),
+};
+
+static const u32 brcmstb_rate_table_7278[] = {
+	MHZ(81),
+	MHZ(108),
+	0,
+	MHZ(48),
+};
+
+struct brcmuart_priv {
+	int		line;
+	struct clk	*baud_mux_clk;
+	unsigned long	default_mux_rate;
+	u32		real_rates[ARRAY_SIZE(brcmstb_rate_table)];
+	const u32	*rate_table;
+	ktime_t		char_wait;
+	struct uart_port *up;
+	struct hrtimer	hrt;
+	bool		shutdown;
+	bool		dma_enabled;
+	struct uart_8250_dma dma;
+	void __iomem	*regs[REGS_MAX];
+	dma_addr_t	rx_addr;
+	void		*rx_bufs;
+	size_t		rx_size;
+	int		rx_next_buf;
+	dma_addr_t	tx_addr;
+	void		*tx_buf;
+	size_t		tx_size;
+	bool		tx_running;
+	bool		rx_running;
+	struct dentry	*debugfs_dir;
+
+	/* stats exposed through debugfs */
+	u64		dma_rx_partial_buf;
+	u64		dma_rx_full_buf;
+	u32		rx_bad_timeout_late_char;
+	u32		rx_bad_timeout_no_char;
+	u32		rx_missing_close_timeout;
+	u32		rx_err;
+	u32		rx_timeout;
+	u32		rx_abort;
+};
+
+struct dentry *brcmuart_debugfs_root;
+
+/*
+ * Register access routines
+ */
+static u32 udma_readl(struct brcmuart_priv *priv,
+		int reg_type, int offset)
+{
+	return readl(priv->regs[reg_type] + offset);
+}
+
+static void udma_writel(struct brcmuart_priv *priv,
+			int reg_type, int offset, u32 value)
+{
+	writel(value, priv->regs[reg_type] + offset);
+}
+
+static void udma_set(struct brcmuart_priv *priv,
+		int reg_type, int offset, u32 bits)
+{
+	void __iomem *reg = priv->regs[reg_type] + offset;
+	u32 value;
+
+	value = readl(reg);
+	value |= bits;
+	writel(value, reg);
+}
+
+static void udma_unset(struct brcmuart_priv *priv,
+		int reg_type, int offset, u32 bits)
+{
+	void __iomem *reg = priv->regs[reg_type] + offset;
+	u32 value;
+
+	value = readl(reg);
+	value &= ~bits;
+	writel(value, reg);
+}
+
+/*
+ * The UART DMA engine hardware can be used by multiple UARTS, but
+ * only one at a time. Sharing is not currently supported so
+ * the first UART to request the DMA engine will get it and any
+ * subsequent requests by other UARTS will fail.
+ */
+static int brcmuart_arbitration(struct brcmuart_priv *priv, bool acquire)
+{
+	u32 rx_grant;
+	u32 tx_grant;
+	int waits;
+	int ret = 0;
+
+	if (acquire) {
+		udma_set(priv, REGS_DMA_ARB, UDMA_ARB_RX, UDMA_ARB_REQ);
+		udma_set(priv, REGS_DMA_ARB, UDMA_ARB_TX, UDMA_ARB_REQ);
+
+		waits = 1;
+		while (1) {
+			rx_grant = udma_readl(priv, REGS_DMA_ARB, UDMA_ARB_RX);
+			tx_grant = udma_readl(priv, REGS_DMA_ARB, UDMA_ARB_TX);
+			if (rx_grant & tx_grant & UDMA_ARB_GRANT)
+				return 0;
+			if (waits-- == 0)
+				break;
+			msleep(1);
+		}
+		ret = 1;
+	}
+
+	udma_unset(priv, REGS_DMA_ARB, UDMA_ARB_RX, UDMA_ARB_REQ);
+	udma_unset(priv, REGS_DMA_ARB, UDMA_ARB_TX, UDMA_ARB_REQ);
+	return ret;
+}
+
+static void brcmuart_init_dma_hardware(struct brcmuart_priv *priv)
+{
+	u32 daddr;
+	u32 value;
+	int x;
+
+	/* Start with all interrupts disabled */
+	udma_writel(priv, REGS_DMA_ISR, UDMA_INTR_MASK_SET, 0xffffffff);
+
+	udma_writel(priv, REGS_DMA_RX, UDMA_RX_BUFFER_SIZE, RX_BUF_SIZE);
+
+	/*
+	 * Setup buffer close to happen when 32 character times have
+	 * elapsed since the last character was received.
+	 */
+	udma_writel(priv, REGS_DMA_RX, UDMA_RX_BUFFER_CLOSE, 16*10*32);
+	value = (RX_BUFS_COUNT << UDMA_RX_CTRL_NUM_BUF_USED_SHIFT)
+		| UDMA_RX_CTRL_BUF_CLOSE_MODE
+		| UDMA_RX_CTRL_BUF_CLOSE_ENA;
+	udma_writel(priv, REGS_DMA_RX, UDMA_RX_CTRL, value);
+
+	udma_writel(priv, REGS_DMA_RX, UDMA_RX_BLOCKOUT_COUNTER, 0);
+	daddr = priv->rx_addr;
+	for (x = 0; x < RX_BUFS_COUNT; x++) {
+
+		/* Set RX transfer length to 0 for unknown */
+		udma_writel(priv, REGS_DMA_RX, UDMA_RX_TRANSFER_LEN, 0);
+
+		udma_writel(priv, REGS_DMA_RX, UDMA_RX_BUFx_PTR_LO(x),
+			    lower_32_bits(daddr));
+		udma_writel(priv, REGS_DMA_RX, UDMA_RX_BUFx_PTR_HI(x),
+			    upper_32_bits(daddr));
+		daddr += RX_BUF_SIZE;
+	}
+
+	daddr = priv->tx_addr;
+	udma_writel(priv, REGS_DMA_TX, UDMA_TX_BUFx_PTR_LO(0),
+		    lower_32_bits(daddr));
+	udma_writel(priv, REGS_DMA_TX, UDMA_TX_BUFx_PTR_HI(0),
+		    upper_32_bits(daddr));
+	udma_writel(priv, REGS_DMA_TX, UDMA_TX_CTRL,
+		    UDMA_TX_CTRL_NUM_BUF_USED_1);
+
+	/* clear all interrupts then enable them */
+	udma_writel(priv, REGS_DMA_ISR, UDMA_INTR_CLEAR, 0xffffffff);
+	udma_writel(priv, REGS_DMA_ISR, UDMA_INTR_MASK_CLEAR,
+		UDMA_RX_INTERRUPTS | UDMA_TX_INTERRUPTS);
+
+}
+
+static void start_rx_dma(struct uart_8250_port *p)
+{
+	struct brcmuart_priv *priv = p->port.private_data;
+	int x;
+
+	udma_unset(priv, REGS_DMA_RX, UDMA_RX_CTRL, UDMA_RX_CTRL_ENA);
+
+	/* Clear the RX ready bit for all buffers */
+	for (x = 0; x < RX_BUFS_COUNT; x++)
+		udma_unset(priv, REGS_DMA_RX, UDMA_RX_BUFx_STATUS(x),
+			UDMA_RX_BUFX_STATUS_DATA_RDY);
+
+	/* always start with buffer 0 */
+	udma_unset(priv, REGS_DMA_RX, UDMA_RX_STATUS,
+		   UDMA_RX_STATUS_ACTIVE_BUF_MASK);
+	priv->rx_next_buf = 0;
+
+	udma_set(priv, REGS_DMA_RX, UDMA_RX_CTRL, UDMA_RX_CTRL_ENA);
+	priv->rx_running = true;
+}
+
+static void stop_rx_dma(struct uart_8250_port *p)
+{
+	struct brcmuart_priv *priv = p->port.private_data;
+
+	/* If RX is running, set the RX ABORT */
+	if (priv->rx_running)
+		udma_set(priv, REGS_DMA_RX, UDMA_RX_CTRL, UDMA_RX_CTRL_ABORT);
+}
+
+static int stop_tx_dma(struct uart_8250_port *p)
+{
+	struct brcmuart_priv *priv = p->port.private_data;
+	u32 value;
+
+	/* If TX is running, set the TX ABORT */
+	value = udma_readl(priv, REGS_DMA_TX, UDMA_TX_CTRL);
+	if (value & UDMA_TX_CTRL_ENA)
+		udma_set(priv, REGS_DMA_TX, UDMA_TX_CTRL, UDMA_TX_CTRL_ABORT);
+	priv->tx_running = false;
+	return 0;
+}
+
+/*
+ * NOTE: printk's in this routine will hang the system if this is
+ * the console tty
+ */
+static int brcmuart_tx_dma(struct uart_8250_port *p)
+{
+	struct brcmuart_priv *priv = p->port.private_data;
+	struct circ_buf *xmit = &p->port.state->xmit;
+	u32 tx_size;
+
+	if (uart_tx_stopped(&p->port) || priv->tx_running ||
+		uart_circ_empty(xmit)) {
+		return 0;
+	}
+	tx_size = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
+
+	priv->dma.tx_err = 0;
+	memcpy(priv->tx_buf, &xmit->buf[xmit->tail], tx_size);
+	xmit->tail += tx_size;
+	xmit->tail &= UART_XMIT_SIZE - 1;
+	p->port.icount.tx += tx_size;
+
+	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+		uart_write_wakeup(&p->port);
+
+	udma_writel(priv, REGS_DMA_TX, UDMA_TX_TRANSFER_LEN, tx_size);
+	udma_writel(priv, REGS_DMA_TX, UDMA_TX_BUF0_DATA_LEN, tx_size);
+	udma_unset(priv, REGS_DMA_TX, UDMA_TX_BUF0_STATUS, UDMA_TX_BUFX_EMPTY);
+	udma_set(priv, REGS_DMA_TX, UDMA_TX_CTRL, UDMA_TX_CTRL_ENA);
+	priv->tx_running = true;
+
+	return 0;
+}
+
+static void brcmuart_rx_buf_done_isr(struct uart_port *up, int index)
+{
+	struct brcmuart_priv *priv = up->private_data;
+	struct tty_port *tty_port = &up->state->port;
+	u32 status;
+	u32 length;
+	u32 copied;
+
+	/* Make sure we're still in sync with the hardware */
+	status = udma_readl(priv, REGS_DMA_RX, UDMA_RX_BUFx_STATUS(index));
+	length = udma_readl(priv, REGS_DMA_RX, UDMA_RX_BUFx_DATA_LEN(index));
+
+	if ((status & UDMA_RX_BUFX_STATUS_DATA_RDY) == 0) {
+		dev_err(up->dev, "RX done interrupt but DATA_RDY not found\n");
+		return;
+	}
+	if (status & (UDMA_RX_BUFX_STATUS_OVERRUN_ERR |
+		      UDMA_RX_BUFX_STATUS_FRAME_ERR |
+		      UDMA_RX_BUFX_STATUS_PARITY_ERR)) {
+		if (status & UDMA_RX_BUFX_STATUS_OVERRUN_ERR) {
+			up->icount.overrun++;
+			dev_warn(up->dev, "RX OVERRUN Error\n");
+		}
+		if (status & UDMA_RX_BUFX_STATUS_FRAME_ERR) {
+			up->icount.frame++;
+			dev_warn(up->dev, "RX FRAMING Error\n");
+		}
+		if (status & UDMA_RX_BUFX_STATUS_PARITY_ERR) {
+			up->icount.parity++;
+			dev_warn(up->dev, "RX PARITY Error\n");
+		}
+	}
+	copied = (u32)tty_insert_flip_string(
+		tty_port,
+		priv->rx_bufs + (index * RX_BUF_SIZE),
+		length);
+	if (copied != length) {
+		dev_warn(up->dev, "Flip buffer overrun of %d bytes\n",
+			 length - copied);
+		up->icount.overrun += length - copied;
+	}
+	up->icount.rx += length;
+	if (status & UDMA_RX_BUFX_STATUS_CLOSE_EXPIRED)
+		priv->dma_rx_partial_buf++;
+	else if (length != RX_BUF_SIZE)
+		/*
+		 * This is a bug in the controller that doesn't cause
+		 * any problems but will be fixed in the future.
+		 */
+		priv->rx_missing_close_timeout++;
+	else
+		priv->dma_rx_full_buf++;
+
+	tty_flip_buffer_push(tty_port);
+}
+
+static void brcmuart_rx_isr(struct uart_port *up, u32 rx_isr)
+{
+	struct brcmuart_priv *priv = up->private_data;
+	struct device *dev = up->dev;
+	u32 rx_done_isr;
+	u32 check_isr;
+
+	rx_done_isr = (rx_isr & UDMA_INTR_RX_READY_MASK);
+	while (rx_done_isr) {
+		check_isr = UDMA_INTR_RX_READY_BUF0 << priv->rx_next_buf;
+		if (check_isr & rx_done_isr) {
+			brcmuart_rx_buf_done_isr(up, priv->rx_next_buf);
+		} else {
+			dev_err(dev,
+				"RX buffer ready out of sequence, restarting RX DMA\n");
+			start_rx_dma(up_to_u8250p(up));
+			break;
+		}
+		if (rx_isr & UDMA_RX_ERR_INTERRUPTS) {
+			if (rx_isr & UDMA_INTR_RX_ERROR)
+				priv->rx_err++;
+			if (rx_isr & UDMA_INTR_RX_TIMEOUT) {
+				priv->rx_timeout++;
+				dev_err(dev, "RX TIMEOUT Error\n");
+			}
+			if (rx_isr & UDMA_INTR_RX_ABORT)
+				priv->rx_abort++;
+			priv->rx_running = false;
+		}
+		/* If not ABORT, re-enable RX buffer */
+		if (!(rx_isr & UDMA_INTR_RX_ABORT))
+			udma_unset(priv, REGS_DMA_RX,
+				   UDMA_RX_BUFx_STATUS(priv->rx_next_buf),
+				   UDMA_RX_BUFX_STATUS_DATA_RDY);
+		rx_done_isr &= ~check_isr;
+		priv->rx_next_buf++;
+		if (priv->rx_next_buf == RX_BUFS_COUNT)
+			priv->rx_next_buf = 0;
+	}
+}
+
+static void brcmuart_tx_isr(struct uart_port *up, u32 isr)
+{
+	struct brcmuart_priv *priv = up->private_data;
+	struct device *dev = up->dev;
+	struct uart_8250_port *port_8250 = up_to_u8250p(up);
+	struct circ_buf	*xmit = &port_8250->port.state->xmit;
+
+	if (isr & UDMA_INTR_TX_ABORT) {
+		if (priv->tx_running)
+			dev_err(dev, "Unexpected TX_ABORT interrupt\n");
+		return;
+	}
+	priv->tx_running = false;
+	if (!uart_circ_empty(xmit) && !uart_tx_stopped(up))
+		brcmuart_tx_dma(port_8250);
+}
+
+static irqreturn_t brcmuart_isr(int irq, void *dev_id)
+{
+	struct uart_port *up = dev_id;
+	struct device *dev = up->dev;
+	struct brcmuart_priv *priv = up->private_data;
+	unsigned long flags;
+	u32 interrupts;
+	u32 rval;
+	u32 tval;
+
+	interrupts = udma_readl(priv, REGS_DMA_ISR, UDMA_INTR_STATUS);
+	if (interrupts == 0)
+		return IRQ_NONE;
+
+	spin_lock_irqsave(&up->lock, flags);
+
+	/* Clear all interrupts */
+	udma_writel(priv, REGS_DMA_ISR, UDMA_INTR_CLEAR, interrupts);
+
+	rval = UDMA_IS_RX_INTERRUPT(interrupts);
+	if (rval)
+		brcmuart_rx_isr(up, rval);
+	tval = UDMA_IS_TX_INTERRUPT(interrupts);
+	if (tval)
+		brcmuart_tx_isr(up, tval);
+	if ((rval | tval) == 0)
+		dev_warn(dev, "Spurious interrupt: 0x%x\n", interrupts);
+
+	spin_unlock_irqrestore(&up->lock, flags);
+	return IRQ_HANDLED;
+}
+
+static int brcmuart_startup(struct uart_port *port)
+{
+	int res;
+	struct uart_8250_port *up = up_to_u8250p(port);
+	struct brcmuart_priv *priv = up->port.private_data;
+
+	priv->shutdown = false;
+
+	/*
+	 * prevent serial8250_do_startup() from allocating non-existent
+	 * DMA resources
+	 */
+	up->dma = NULL;
+
+	res = serial8250_do_startup(port);
+	if (!priv->dma_enabled)
+		return res;
+	/*
+	 * Disable the Receive Data Interrupt because the DMA engine
+	 * will handle this.
+	 */
+	up->ier &= ~UART_IER_RDI;
+	serial_port_out(port, UART_IER, up->ier);
+
+	priv->tx_running = false;
+	priv->dma.rx_dma = NULL;
+	priv->dma.tx_dma = brcmuart_tx_dma;
+	up->dma = &priv->dma;
+
+	brcmuart_init_dma_hardware(priv);
+	start_rx_dma(up);
+	return res;
+}
+
+static void brcmuart_shutdown(struct uart_port *port)
+{
+	struct uart_8250_port *up = up_to_u8250p(port);
+	struct brcmuart_priv *priv = up->port.private_data;
+	unsigned long flags;
+
+	spin_lock_irqsave(&port->lock, flags);
+	priv->shutdown = true;
+	if (priv->dma_enabled) {
+		stop_rx_dma(up);
+		stop_tx_dma(up);
+		/* disable all interrupts */
+		udma_writel(priv, REGS_DMA_ISR, UDMA_INTR_MASK_SET,
+			UDMA_RX_INTERRUPTS | UDMA_TX_INTERRUPTS);
+	}
+
+	/*
+	 * prevent serial8250_do_shutdown() from trying to free
+	 * DMA resources that we never alloc'd for this driver.
+	 */
+	up->dma = NULL;
+
+	spin_unlock_irqrestore(&port->lock, flags);
+	serial8250_do_shutdown(port);
+}
+
+/*
+ * Not all clocks run at the exact specified rate, so set each requested
+ * rate and then get the actual rate.
+ */
+static void init_real_clk_rates(struct device *dev, struct brcmuart_priv *priv)
+{
+	int x;
+	int rc;
+
+	priv->default_mux_rate = clk_get_rate(priv->baud_mux_clk);
+	for (x = 0; x < ARRAY_SIZE(priv->real_rates); x++) {
+		if (priv->rate_table[x] == 0) {
+			priv->real_rates[x] = 0;
+			continue;
+		}
+		rc = clk_set_rate(priv->baud_mux_clk, priv->rate_table[x]);
+		if (rc) {
+			dev_err(dev, "Error selecting BAUD MUX clock for %u\n",
+				priv->rate_table[x]);
+			priv->real_rates[x] = priv->rate_table[x];
+		} else {
+			priv->real_rates[x] = clk_get_rate(priv->baud_mux_clk);
+		}
+	}
+	clk_set_rate(priv->baud_mux_clk, priv->default_mux_rate);
+}
+
+static void set_clock_mux(struct uart_port *up, struct brcmuart_priv *priv,
+			u32 baud)
+{
+	u32 percent;
+	u32 best_percent = UINT_MAX;
+	u32 quot;
+	u32 best_quot = 1;
+	u32 rate;
+	int best_index = -1;
+	u64 hires_rate;
+	u64 hires_baud;
+	u64 hires_err;
+	int rc;
+	int i;
+	int real_baud;
+
+	/* If the Baud Mux Clock was not specified, just return */
+	if (priv->baud_mux_clk == NULL)
+		return;
+
+	/* Find the closest match for specified baud */
+	for (i = 0; i < ARRAY_SIZE(priv->real_rates); i++) {
+		if (priv->real_rates[i] == 0)
+			continue;
+		rate = priv->real_rates[i] / 16;
+		quot = DIV_ROUND_CLOSEST(rate, baud);
+		if (!quot)
+			continue;
+
+		/* increase resolution to get xx.xx percent */
+		hires_rate = (u64)rate * 10000;
+		hires_baud = (u64)baud * 10000;
+
+		hires_err = div_u64(hires_rate, (u64)quot);
+
+		/* get the delta */
+		if (hires_err > hires_baud)
+			hires_err = (hires_err - hires_baud);
+		else
+			hires_err = (hires_baud - hires_err);
+
+		percent = (unsigned long)DIV_ROUND_CLOSEST_ULL(hires_err, baud);
+		dev_dbg(up->dev,
+			"Baud rate: %u, MUX Clk: %u, Error: %u.%u%%\n",
+			baud, priv->real_rates[i], percent / 100,
+			percent % 100);
+		if (percent < best_percent) {
+			best_percent = percent;
+			best_index = i;
+			best_quot = quot;
+		}
+	}
+	if (best_index == -1) {
+		dev_err(up->dev, "Error, %d BAUD rate is too fast.\n", baud);
+		return;
+	}
+	rate = priv->real_rates[best_index];
+	rc = clk_set_rate(priv->baud_mux_clk, rate);
+	if (rc)
+		dev_err(up->dev, "Error selecting BAUD MUX clock\n");
+
+	/* Error over 3 percent will cause data errors */
+	if (best_percent > 300)
+		dev_err(up->dev, "Error, baud: %d has %u.%u%% error\n",
+			baud, percent / 100, percent % 100);
+
+	real_baud = rate / 16 / best_quot;
+	dev_dbg(up->dev, "Selecting BAUD MUX rate: %u\n", rate);
+	dev_dbg(up->dev, "Requested baud: %u, Actual baud: %u\n",
+		baud, real_baud);
+
+	/* calc nanoseconds for 1.5 characters time at the given baud rate */
+	i = NSEC_PER_SEC / real_baud / 10;
+	i += (i / 2);
+	priv->char_wait = ns_to_ktime(i);
+
+	up->uartclk = rate;
+}
+
+static void brcmstb_set_termios(struct uart_port *up,
+				struct ktermios *termios,
+				struct ktermios *old)
+{
+	struct uart_8250_port *p8250 = up_to_u8250p(up);
+	struct brcmuart_priv *priv = up->private_data;
+
+	if (priv->dma_enabled)
+		stop_rx_dma(p8250);
+	set_clock_mux(up, priv, tty_termios_baud_rate(termios));
+	serial8250_do_set_termios(up, termios, old);
+	if (p8250->mcr & UART_MCR_AFE)
+		p8250->port.status |= UPSTAT_AUTOCTS;
+	if (priv->dma_enabled)
+		start_rx_dma(p8250);
+}
+
+static int brcmuart_handle_irq(struct uart_port *p)
+{
+	unsigned int iir = serial_port_in(p, UART_IIR);
+	struct brcmuart_priv *priv = p->private_data;
+	struct uart_8250_port *up = up_to_u8250p(p);
+	unsigned int status;
+	unsigned long flags;
+	unsigned int ier;
+	unsigned int mcr;
+	int handled = 0;
+
+	/*
+	 * There's a bug in some 8250 cores where we get a timeout
+	 * interrupt but there is no data ready.
+	 */
+	if (((iir & UART_IIR_ID) == UART_IIR_RX_TIMEOUT) && !(priv->shutdown)) {
+		spin_lock_irqsave(&p->lock, flags);
+		status = serial_port_in(p, UART_LSR);
+		if ((status & UART_LSR_DR) == 0) {
+
+			ier = serial_port_in(p, UART_IER);
+			/*
+			 * if Receive Data Interrupt is enabled and
+			 * we're uing hardware flow control, deassert
+			 * RTS and wait for any chars in the pipline to
+			 * arrive and then check for DR again.
+			 */
+			if ((ier & UART_IER_RDI) && (up->mcr & UART_MCR_AFE)) {
+				ier &= ~(UART_IER_RLSI | UART_IER_RDI);
+				serial_port_out(p, UART_IER, ier);
+				mcr = serial_port_in(p, UART_MCR);
+				mcr &= ~UART_MCR_RTS;
+				serial_port_out(p, UART_MCR, mcr);
+				hrtimer_start(&priv->hrt, priv->char_wait,
+					      HRTIMER_MODE_REL);
+			} else {
+				serial_port_in(p, UART_RX);
+			}
+
+			handled = 1;
+		}
+		spin_unlock_irqrestore(&p->lock, flags);
+		if (handled)
+			return 1;
+	}
+	return serial8250_handle_irq(p, iir);
+}
+
+static enum hrtimer_restart brcmuart_hrtimer_func(struct hrtimer *t)
+{
+	struct brcmuart_priv *priv = container_of(t, struct brcmuart_priv, hrt);
+	struct uart_port *p = priv->up;
+	struct uart_8250_port *up = up_to_u8250p(p);
+	unsigned int status;
+	unsigned long flags;
+
+	if (priv->shutdown)
+		return HRTIMER_NORESTART;
+
+	spin_lock_irqsave(&p->lock, flags);
+	status = serial_port_in(p, UART_LSR);
+
+	/*
+	 * If a character did not arrive after the timeout, clear the false
+	 * receive timeout.
+	 */
+	if ((status & UART_LSR_DR) == 0) {
+		serial_port_in(p, UART_RX);
+		priv->rx_bad_timeout_no_char++;
+	} else {
+		priv->rx_bad_timeout_late_char++;
+	}
+
+	/* re-enable receive unless upper layer has disabled it */
+	if ((up->ier & (UART_IER_RLSI | UART_IER_RDI)) ==
+	    (UART_IER_RLSI | UART_IER_RDI)) {
+		status = serial_port_in(p, UART_IER);
+		status |= (UART_IER_RLSI | UART_IER_RDI);
+		serial_port_out(p, UART_IER, status);
+		status = serial_port_in(p, UART_MCR);
+		status |= UART_MCR_RTS;
+		serial_port_out(p, UART_MCR, status);
+	}
+	spin_unlock_irqrestore(&p->lock, flags);
+	return HRTIMER_NORESTART;
+}
+
+static const struct of_device_id brcmuart_dt_ids[] = {
+	{
+		.compatible = "brcm,bcm7278-uart",
+		.data = brcmstb_rate_table_7278,
+	},
+	{
+		.compatible = "brcm,bcm7271-uart",
+		.data = brcmstb_rate_table,
+	},
+	{},
+};
+
+MODULE_DEVICE_TABLE(of, brcmuart_dt_ids);
+
+static void brcmuart_free_bufs(struct device *dev, struct brcmuart_priv *priv)
+{
+	if (priv->rx_bufs)
+		dma_free_coherent(dev, priv->rx_size, priv->rx_bufs,
+				  priv->rx_addr);
+	if (priv->tx_buf)
+		dma_free_coherent(dev, priv->tx_size, priv->tx_buf,
+				  priv->tx_addr);
+}
+
+static void brcmuart_throttle(struct uart_port *port)
+{
+	struct brcmuart_priv *priv = port->private_data;
+
+	udma_writel(priv, REGS_DMA_ISR, UDMA_INTR_MASK_SET, UDMA_RX_INTERRUPTS);
+}
+
+static void brcmuart_unthrottle(struct uart_port *port)
+{
+	struct brcmuart_priv *priv = port->private_data;
+
+	udma_writel(priv, REGS_DMA_ISR, UDMA_INTR_MASK_CLEAR,
+		    UDMA_RX_INTERRUPTS);
+}
+
+static int debugfs_stats_show(struct seq_file *s, void *unused)
+{
+	struct brcmuart_priv *priv = s->private;
+
+	seq_printf(s, "rx_err:\t\t\t\t%u\n",
+		   priv->rx_err);
+	seq_printf(s, "rx_timeout:\t\t\t%u\n",
+		   priv->rx_timeout);
+	seq_printf(s, "rx_abort:\t\t\t%u\n",
+		   priv->rx_abort);
+	seq_printf(s, "rx_bad_timeout_late_char:\t%u\n",
+		   priv->rx_bad_timeout_late_char);
+	seq_printf(s, "rx_bad_timeout_no_char:\t\t%u\n",
+		   priv->rx_bad_timeout_no_char);
+	seq_printf(s, "rx_missing_close_timeout:\t%u\n",
+		   priv->rx_missing_close_timeout);
+	if (priv->dma_enabled) {
+		seq_printf(s, "dma_rx_partial_buf:\t\t%llu\n",
+			   priv->dma_rx_partial_buf);
+		seq_printf(s, "dma_rx_full_buf:\t\t%llu\n",
+			   priv->dma_rx_full_buf);
+	}
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(debugfs_stats);
+
+static void brcmuart_init_debugfs(struct brcmuart_priv *priv,
+				  const char *device)
+{
+	priv->debugfs_dir = debugfs_create_dir(device, brcmuart_debugfs_root);
+	debugfs_create_file("stats", 0444, priv->debugfs_dir, priv,
+			    &debugfs_stats_fops);
+}
+
+
+static int brcmuart_probe(struct platform_device *pdev)
+{
+	struct resource *regs;
+	struct device_node *np = pdev->dev.of_node;
+	const struct of_device_id *of_id = NULL;
+	struct uart_8250_port *new_port;
+	struct device *dev = &pdev->dev;
+	struct brcmuart_priv *priv;
+	struct clk *baud_mux_clk;
+	struct uart_8250_port up;
+	struct resource *irq;
+	void __iomem *membase = 0;
+	resource_size_t mapbase = 0;
+	u32 clk_rate = 0;
+	int ret;
+	int x;
+	int dma_irq;
+	static const char * const reg_names[REGS_MAX] = {
+		"uart", "dma_rx", "dma_tx", "dma_intr2", "dma_arb"
+	};
+
+	irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
+	if (!irq) {
+		dev_err(dev, "missing irq\n");
+		return -EINVAL;
+	}
+	priv = devm_kzalloc(dev, sizeof(struct brcmuart_priv),
+			GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	of_id = of_match_node(brcmuart_dt_ids, np);
+	if (!of_id || !of_id->data)
+		priv->rate_table = brcmstb_rate_table;
+	else
+		priv->rate_table = of_id->data;
+
+	for (x = 0; x < REGS_MAX; x++) {
+		regs = platform_get_resource_byname(pdev, IORESOURCE_MEM,
+						reg_names[x]);
+		if (!regs)
+			break;
+		priv->regs[x] =	devm_ioremap(dev, regs->start,
+					     resource_size(regs));
+		if (IS_ERR(priv->regs[x]))
+			return PTR_ERR(priv->regs[x]);
+		if (x == REGS_8250) {
+			mapbase = regs->start;
+			membase = priv->regs[x];
+		}
+	}
+
+	/* We should have just the uart base registers or all the registers */
+	if (x != 1 && x != REGS_MAX) {
+		dev_warn(dev, "%s registers not specified\n", reg_names[x]);
+		return -EINVAL;
+	}
+
+	/* if the DMA registers were specified, try to enable DMA */
+	if (x > REGS_DMA_RX) {
+		if (brcmuart_arbitration(priv, 1) == 0) {
+			u32 txrev = 0;
+			u32 rxrev = 0;
+
+			txrev = udma_readl(priv, REGS_DMA_RX, UDMA_RX_REVISION);
+			rxrev = udma_readl(priv, REGS_DMA_TX, UDMA_TX_REVISION);
+			if ((txrev >= UDMA_TX_REVISION_REQUIRED) &&
+				(rxrev >= UDMA_RX_REVISION_REQUIRED)) {
+
+				/* Enable the use of the DMA hardware */
+				priv->dma_enabled = true;
+			} else {
+				brcmuart_arbitration(priv, 0);
+				dev_err(dev,
+					"Unsupported DMA Hardware Revision\n");
+			}
+		} else {
+			dev_err(dev,
+				"Timeout arbitrating for UART DMA hardware\n");
+		}
+	}
+
+	of_property_read_u32(np, "clock-frequency", &clk_rate);
+
+	/* See if a Baud clock has been specified */
+	baud_mux_clk = of_clk_get_by_name(np, "sw_baud");
+	if (IS_ERR(baud_mux_clk)) {
+		if (PTR_ERR(baud_mux_clk) == -EPROBE_DEFER)
+			return -EPROBE_DEFER;
+		dev_dbg(dev, "BAUD MUX clock not specified\n");
+	} else {
+		dev_dbg(dev, "BAUD MUX clock found\n");
+		ret = clk_prepare_enable(baud_mux_clk);
+		if (ret)
+			return ret;
+		priv->baud_mux_clk = baud_mux_clk;
+		init_real_clk_rates(dev, priv);
+		clk_rate = priv->default_mux_rate;
+	}
+
+	if (clk_rate == 0) {
+		dev_err(dev, "clock-frequency or clk not defined\n");
+		return -EINVAL;
+	}
+
+	dev_dbg(dev, "DMA is %senabled\n", priv->dma_enabled ? "" : "not ");
+
+	memset(&up, 0, sizeof(up));
+	up.port.type = PORT_16550A;
+	up.port.uartclk = clk_rate;
+	up.port.dev = dev;
+	up.port.mapbase = mapbase;
+	up.port.membase = membase;
+	up.port.irq = irq->start;
+	up.port.handle_irq = brcmuart_handle_irq;
+	up.port.regshift = 2;
+	up.port.iotype = of_device_is_big_endian(np) ?
+		UPIO_MEM32BE : UPIO_MEM32;
+	up.port.flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
+		| UPF_FIXED_PORT | UPF_FIXED_TYPE;
+	up.port.dev = dev;
+	up.port.private_data = priv;
+	up.capabilities = UART_CAP_FIFO | UART_CAP_AFE;
+	up.port.fifosize = 32;
+
+	/* Check for a fixed line number */
+	ret = of_alias_get_id(np, "serial");
+	if (ret >= 0)
+		up.port.line = ret;
+
+	/* setup HR timer */
+	hrtimer_init(&priv->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+	priv->hrt.function = brcmuart_hrtimer_func;
+
+	up.port.shutdown = brcmuart_shutdown;
+	up.port.startup = brcmuart_startup;
+	up.port.throttle = brcmuart_throttle;
+	up.port.unthrottle = brcmuart_unthrottle;
+	up.port.set_termios = brcmstb_set_termios;
+
+	if (priv->dma_enabled) {
+		priv->rx_size = RX_BUF_SIZE * RX_BUFS_COUNT;
+		priv->rx_bufs = dma_alloc_coherent(dev,
+						   priv->rx_size,
+						   &priv->rx_addr, GFP_KERNEL);
+		if (!priv->rx_bufs)
+			goto err;
+		priv->tx_size = UART_XMIT_SIZE;
+		priv->tx_buf = dma_alloc_coherent(dev,
+						  priv->tx_size,
+						  &priv->tx_addr, GFP_KERNEL);
+		if (!priv->tx_buf)
+			goto err;
+	}
+
+	ret = serial8250_register_8250_port(&up);
+	if (ret < 0) {
+		dev_err(dev, "unable to register 8250 port\n");
+		goto err;
+	}
+	priv->line = ret;
+	new_port = serial8250_get_port(ret);
+	priv->up = &new_port->port;
+	if (priv->dma_enabled) {
+		dma_irq = platform_get_irq_byname(pdev,  "dma");
+		if (dma_irq < 0) {
+			dev_err(dev, "no IRQ resource info\n");
+			goto err1;
+		}
+		ret = devm_request_irq(dev, dma_irq, brcmuart_isr,
+				IRQF_SHARED, "uart DMA irq", &new_port->port);
+		if (ret) {
+			dev_err(dev, "unable to register IRQ handler\n");
+			goto err1;
+		}
+	}
+	platform_set_drvdata(pdev, priv);
+	brcmuart_init_debugfs(priv, dev_name(&pdev->dev));
+	return 0;
+
+err1:
+	serial8250_unregister_port(priv->line);
+err:
+	brcmuart_free_bufs(dev, priv);
+	brcmuart_arbitration(priv, 0);
+	return -ENODEV;
+}
+
+static int brcmuart_remove(struct platform_device *pdev)
+{
+	struct brcmuart_priv *priv = platform_get_drvdata(pdev);
+
+	debugfs_remove_recursive(priv->debugfs_dir);
+	hrtimer_cancel(&priv->hrt);
+	serial8250_unregister_port(priv->line);
+	brcmuart_free_bufs(&pdev->dev, priv);
+	brcmuart_arbitration(priv, 0);
+	return 0;
+}
+
+static int __maybe_unused brcmuart_suspend(struct device *dev)
+{
+	struct brcmuart_priv *priv = dev_get_drvdata(dev);
+
+	serial8250_suspend_port(priv->line);
+	clk_disable_unprepare(priv->baud_mux_clk);
+
+	return 0;
+}
+
+static int __maybe_unused brcmuart_resume(struct device *dev)
+{
+	struct brcmuart_priv *priv = dev_get_drvdata(dev);
+	int ret;
+
+	ret = clk_prepare_enable(priv->baud_mux_clk);
+	if (ret)
+		dev_err(dev, "Error enabling BAUD MUX clock\n");
+
+	/*
+	 * The hardware goes back to it's default after suspend
+	 * so get the "clk" back in sync.
+	 */
+	ret = clk_set_rate(priv->baud_mux_clk, priv->default_mux_rate);
+	if (ret)
+		dev_err(dev, "Error restoring default BAUD MUX clock\n");
+	if (priv->dma_enabled) {
+		if (brcmuart_arbitration(priv, 1)) {
+			dev_err(dev, "Timeout arbitrating for DMA hardware on resume\n");
+			return(-EBUSY);
+		}
+		brcmuart_init_dma_hardware(priv);
+		start_rx_dma(serial8250_get_port(priv->line));
+	}
+	serial8250_resume_port(priv->line);
+	return 0;
+}
+
+static const struct dev_pm_ops brcmuart_dev_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(brcmuart_suspend, brcmuart_resume)
+};
+
+static struct platform_driver brcmuart_platform_driver = {
+	.driver = {
+		.name	= "bcm7271-uart",
+		.pm		= &brcmuart_dev_pm_ops,
+		.of_match_table = brcmuart_dt_ids,
+	},
+	.probe		= brcmuart_probe,
+	.remove		= brcmuart_remove,
+};
+
+static int __init brcmuart_init(void)
+{
+	brcmuart_debugfs_root = debugfs_create_dir(
+		brcmuart_platform_driver.driver.name, NULL);
+	return platform_driver_register(&brcmuart_platform_driver);
+}
+module_init(brcmuart_init);
+
+static void __exit brcmuart_deinit(void)
+{
+	platform_driver_unregister(&brcmuart_platform_driver);
+	debugfs_remove_recursive(brcmuart_debugfs_root);
+}
+module_exit(brcmuart_deinit);
+
+MODULE_AUTHOR("Al Cooper");
+MODULE_DESCRIPTION("Broadcom NS16550A compatible serial port driver");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index 603137da4736..d8891d03e8d1 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig
@@ -510,6 +510,16 @@  config SERIAL_8250_TEGRA
 	  Select this option if you have machine with an NVIDIA Tegra SoC and
 	  wish to enable 8250 serial driver for the Tegra serial interfaces.
 
+config SERIAL_8250_BCM7271
+	bool "Broadcom 8250 based serial port"
+	depends on SERIAL_8250 && (ARCH_BRCMSTB || COMPILE_TEST)
+	default ARCH_BRCMSTB
+	help
+	  If you have a Broadcom STB based board and want to use the
+	  enhanced features of the Broadcom 8250 based serial port,
+	  including DMA support and high accuracy BAUD rates, say
+	  Y to this option. If unsure, say N.
+
 config SERIAL_OF_PLATFORM
 	tristate "Devicetree based probing for 8250 ports"
 	depends on SERIAL_8250 && OF
diff --git a/drivers/tty/serial/8250/Makefile b/drivers/tty/serial/8250/Makefile
index a8bfb654d490..b9bcd73c8997 100644
--- a/drivers/tty/serial/8250/Makefile
+++ b/drivers/tty/serial/8250/Makefile
@@ -38,6 +38,7 @@  obj-$(CONFIG_SERIAL_8250_LPSS)		+= 8250_lpss.o
 obj-$(CONFIG_SERIAL_8250_MID)		+= 8250_mid.o
 obj-$(CONFIG_SERIAL_8250_PXA)		+= 8250_pxa.o
 obj-$(CONFIG_SERIAL_8250_TEGRA)		+= 8250_tegra.o
+obj-$(CONFIG_SERIAL_8250_BCM7271)	+= 8250_bcm7271.o
 obj-$(CONFIG_SERIAL_OF_PLATFORM)	+= 8250_of.o
 
 CFLAGS_8250_ingenic.o += -I$(srctree)/scripts/dtc/libfdt