path: root/drivers/tty/serial/8250/8250_bcm7271.c

// 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;
};

static 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 (!priv->regs[x])
			return -ENOMEM;
		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");