drivers/tty/serial/8250/8250_mtk.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * Mediatek 8250 driver.
  *
  * Copyright (c) 2014 MundoReader S.L.
  * Author: Matthias Brugger <matthias.bgg@gmail.com>
  */
 #include <linux/clk.h>
 #include <linux/io.h>
 #include <linux/module.h>
 #include <linux/of_irq.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
 #include <linux/serial_8250.h>
 #include <linux/serial_reg.h>
 #include <linux/console.h>
 #include <linux/dma-mapping.h>
 #include <linux/tty.h>
 #include <linux/tty_flip.h>

 #include "8250.h"

 #define UART_MTK_HIGHS		0x09	/* Highspeed register */
 #define UART_MTK_SAMPLE_COUNT	0x0a	/* Sample count register */
 #define UART_MTK_SAMPLE_POINT	0x0b	/* Sample point register */
 #define MTK_UART_RATE_FIX	0x0d	/* UART Rate Fix Register */

 #define MTK_UART_DMA_EN		0x13	/* DMA Enable register */
 #define MTK_UART_DMA_EN_TX	0x2
 #define MTK_UART_DMA_EN_RX	0x5

 #define MTK_UART_TX_SIZE	UART_XMIT_SIZE
 #define MTK_UART_RX_SIZE	0x8000
 #define MTK_UART_TX_TRIGGER	1
 #define MTK_UART_RX_TRIGGER	MTK_UART_RX_SIZE

 #ifdef CONFIG_SERIAL_8250_DMA
 enum dma_rx_status {
 	DMA_RX_START = 0,
 	DMA_RX_RUNNING = 1,
 	DMA_RX_SHUTDOWN = 2,
 };
 #endif

 struct mtk8250_data {
 	int			line;
 	unsigned int		rx_pos;
 	struct clk		*uart_clk;
 	struct clk		*bus_clk;
 	struct uart_8250_dma	*dma;
 #ifdef CONFIG_SERIAL_8250_DMA
 	enum dma_rx_status	rx_status;
 #endif
 };

 #ifdef CONFIG_SERIAL_8250_DMA
 static void mtk8250_rx_dma(struct uart_8250_port *up);

 static void mtk8250_dma_rx_complete(void *param)
 {
 	struct uart_8250_port *up = param;
 	struct uart_8250_dma *dma = up->dma;
 	struct mtk8250_data *data = up->port.private_data;
 	struct tty_port *tty_port = &up->port.state->port;
 	struct dma_tx_state state;
 	unsigned char *ptr;
 	int copied;

 	dma_sync_single_for_cpu(dma->rxchan->device->dev, dma->rx_addr,
 				dma->rx_size, DMA_FROM_DEVICE);

 	dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);

 	if (data->rx_status == DMA_RX_SHUTDOWN)
 		return;

 	if ((data->rx_pos + state.residue) <= dma->rx_size) {
 		ptr = (unsigned char *)(data->rx_pos + dma->rx_buf);
 		copied = tty_insert_flip_string(tty_port, ptr, state.residue);
 	} else {
 		ptr = (unsigned char *)(data->rx_pos + dma->rx_buf);
 		copied = tty_insert_flip_string(tty_port, ptr,
 						dma->rx_size - data->rx_pos);
 		ptr = (unsigned char *)(dma->rx_buf);
 		copied += tty_insert_flip_string(tty_port, ptr,
 				data->rx_pos + state.residue - dma->rx_size);
 	}
 	up->port.icount.rx += copied;

 	tty_flip_buffer_push(tty_port);

 	mtk8250_rx_dma(up);
 }

 static void mtk8250_rx_dma(struct uart_8250_port *up)
 {
 	struct uart_8250_dma *dma = up->dma;
 	struct mtk8250_data *data = up->port.private_data;
 	struct dma_async_tx_descriptor	*desc;
 	struct dma_tx_state	 state;

 	desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr,
 					   dma->rx_size, DMA_DEV_TO_MEM,
 					   DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
 	if (!desc) {
 		pr_err("failed to prepare rx slave single\n");
 		return;
 	}

 	desc->callback = mtk8250_dma_rx_complete;
 	desc->callback_param = up;

 	dma->rx_cookie = dmaengine_submit(desc);

 	dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
 	data->rx_pos = state.residue;

 	dma_sync_single_for_device(dma->rxchan->device->dev, dma->rx_addr,
 				   dma->rx_size, DMA_FROM_DEVICE);

 	dma_async_issue_pending(dma->rxchan);
 }

 static void mtk8250_dma_enable(struct uart_8250_port *up)
 {
 	struct uart_8250_dma *dma = up->dma;
 	struct mtk8250_data *data = up->port.private_data;
 	int lcr = serial_in(up, UART_LCR);

 	if (data->rx_status != DMA_RX_START)
 		return;

 	dma->rxconf.direction		= DMA_DEV_TO_MEM;
 	dma->rxconf.src_addr_width	= dma->rx_size / 1024;
 	dma->rxconf.src_addr		= dma->rx_addr;

 	dma->txconf.direction		= DMA_MEM_TO_DEV;
 	dma->txconf.dst_addr_width	= MTK_UART_TX_SIZE / 1024;
 	dma->txconf.dst_addr		= dma->tx_addr;

 	serial_out(up, UART_FCR, UART_FCR_ENABLE_FIFO | UART_FCR_CLEAR_RCVR |
 		UART_FCR_CLEAR_XMIT);
 	serial_out(up, MTK_UART_DMA_EN,
 		   MTK_UART_DMA_EN_RX | MTK_UART_DMA_EN_TX);

 	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
 	serial_out(up, UART_EFR, UART_EFR_ECB);
 	serial_out(up, UART_LCR, lcr);

 	if (dmaengine_slave_config(dma->rxchan, &dma->rxconf) != 0)
 		pr_err("failed to configure rx dma channel\n");
 	if (dmaengine_slave_config(dma->txchan, &dma->txconf) != 0)
 		pr_err("failed to configure tx dma channel\n");

 	data->rx_status = DMA_RX_RUNNING;
 	data->rx_pos = 0;
 	mtk8250_rx_dma(up);
 }
 #endif

 static int mtk8250_startup(struct uart_port *port)
 {
 #ifdef CONFIG_SERIAL_8250_DMA
 	struct uart_8250_port *up = up_to_u8250p(port);
 	struct mtk8250_data *data = port->private_data;

 	/* disable DMA for console */
 	if (uart_console(port))
 		up->dma = NULL;

 	if (up->dma) {
 		data->rx_status = DMA_RX_START;
 		uart_circ_clear(&port->state->xmit);
 	}
 #endif
 	memset(&port->icount, 0, sizeof(port->icount));

 	return serial8250_do_startup(port);
 }

 static void mtk8250_shutdown(struct uart_port *port)
 {
 #ifdef CONFIG_SERIAL_8250_DMA
 	struct uart_8250_port *up = up_to_u8250p(port);
 	struct mtk8250_data *data = port->private_data;

 	if (up->dma)
 		data->rx_status = DMA_RX_SHUTDOWN;
 #endif

 	return serial8250_do_shutdown(port);
 }

 static void
 mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
 			struct ktermios *old)
 {
 	struct uart_8250_port *up = up_to_u8250p(port);
 	unsigned long flags;
 	unsigned int baud, quot;

 #ifdef CONFIG_SERIAL_8250_DMA
 	if (up->dma) {
 		if (uart_console(port)) {
 			devm_kfree(up->port.dev, up->dma);
 			up->dma = NULL;
 		} else {
 			mtk8250_dma_enable(up);
 		}
 	}
 #endif

 	serial8250_do_set_termios(port, termios, old);

 	/*
 	 * Mediatek UARTs use an extra highspeed register (UART_MTK_HIGHS)
 	 *
 	 * We need to recalcualte the quot register, as the claculation depends
 	 * on the vaule in the highspeed register.
 	 *
 	 * Some baudrates are not supported by the chip, so we use the next
 	 * lower rate supported and update termios c_flag.
 	 *
 	 * If highspeed register is set to 3, we need to specify sample count
 	 * and sample point to increase accuracy. If not, we reset the
 	 * registers to their default values.
 	 */
 	baud = uart_get_baud_rate(port, termios, old,
 				  port->uartclk / 16 / UART_DIV_MAX,
 				  port->uartclk);

 	if (baud <= 115200) {
 		serial_port_out(port, UART_MTK_HIGHS, 0x0);
 		quot = uart_get_divisor(port, baud);
 	} else if (baud <= 576000) {
 		serial_port_out(port, UART_MTK_HIGHS, 0x2);

 		/* Set to next lower baudrate supported */
 		if ((baud == 500000) || (baud == 576000))
 			baud = 460800;
 		quot = DIV_ROUND_UP(port->uartclk, 4 * baud);
 	} else {
 		serial_port_out(port, UART_MTK_HIGHS, 0x3);
 		quot = DIV_ROUND_UP(port->uartclk, 256 * baud);
 	}

 	/*
 	 * Ok, we're now changing the port state.  Do it with
 	 * interrupts disabled.
 	 */
 	spin_lock_irqsave(&port->lock, flags);

 	/* set DLAB we have cval saved in up->lcr from the call to the core */
 	serial_port_out(port, UART_LCR, up->lcr | UART_LCR_DLAB);
 	serial_dl_write(up, quot);

 	/* reset DLAB */
 	serial_port_out(port, UART_LCR, up->lcr);

 	if (baud > 460800) {
 		unsigned int tmp;

 		tmp = DIV_ROUND_CLOSEST(port->uartclk, quot * baud);
 		serial_port_out(port, UART_MTK_SAMPLE_COUNT, tmp - 1);
 		serial_port_out(port, UART_MTK_SAMPLE_POINT,
 					(tmp - 2) >> 1);
 	} else {
 		serial_port_out(port, UART_MTK_SAMPLE_COUNT, 0x00);
 		serial_port_out(port, UART_MTK_SAMPLE_POINT, 0xff);
 	}

 	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 int __maybe_unused mtk8250_runtime_suspend(struct device *dev)
 {
 	struct mtk8250_data *data = dev_get_drvdata(dev);

 	clk_disable_unprepare(data->uart_clk);
 	clk_disable_unprepare(data->bus_clk);

 	return 0;
 }

 static int __maybe_unused mtk8250_runtime_resume(struct device *dev)
 {
 	struct mtk8250_data *data = dev_get_drvdata(dev);
 	int err;

 	err = clk_prepare_enable(data->uart_clk);
 	if (err) {
 		dev_warn(dev, "Can't enable clock\n");
 		return err;
 	}

 	err = clk_prepare_enable(data->bus_clk);
 	if (err) {
 		dev_warn(dev, "Can't enable bus clock\n");
 		return err;
 	}

 	return 0;
 }

 static void
 mtk8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old)
 {
 	if (!state)
 		pm_runtime_get_sync(port->dev);

 	serial8250_do_pm(port, state, old);

 	if (state)
 		pm_runtime_put_sync_suspend(port->dev);
 }

 #ifdef CONFIG_SERIAL_8250_DMA
 static bool mtk8250_dma_filter(struct dma_chan *chan, void *param)
 {
 	return false;
 }
 #endif

 static int mtk8250_probe_of(struct platform_device *pdev, struct uart_port *p,
 			   struct mtk8250_data *data)
 {
 #ifdef CONFIG_SERIAL_8250_DMA
 	int dmacnt;
 #endif

 	data->uart_clk = devm_clk_get(&pdev->dev, "baud");
 	if (IS_ERR(data->uart_clk)) {
 		/*
 		 * For compatibility with older device trees try unnamed
 		 * clk when no baud clk can be found.
 		 */
 		data->uart_clk = devm_clk_get(&pdev->dev, NULL);
 		if (IS_ERR(data->uart_clk)) {
 			dev_warn(&pdev->dev, "Can't get uart clock\n");
 			return PTR_ERR(data->uart_clk);
 		}

 		return 0;
 	}

 	data->bus_clk = devm_clk_get(&pdev->dev, "bus");
 	if (IS_ERR(data->bus_clk))
 		return PTR_ERR(data->bus_clk);

 	data->dma = NULL;
 #ifdef CONFIG_SERIAL_8250_DMA
 	dmacnt = of_property_count_strings(pdev->dev.of_node, "dma-names");
 	if (dmacnt == 2) {
 		data->dma = devm_kzalloc(&pdev->dev, sizeof(*data->dma),
 					 GFP_KERNEL);
 		if (!data->dma)
 			return -ENOMEM;

 		data->dma->fn = mtk8250_dma_filter;
 		data->dma->rx_size = MTK_UART_RX_SIZE;
 		data->dma->rxconf.src_maxburst = MTK_UART_RX_TRIGGER;
 		data->dma->txconf.dst_maxburst = MTK_UART_TX_TRIGGER;
 	}
 #endif

 	return 0;
 }

 static int mtk8250_probe(struct platform_device *pdev)
 {
 	struct uart_8250_port uart = {};
 	struct resource *regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	struct resource *irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
 	struct mtk8250_data *data;
 	int err;

 	if (!regs || !irq) {
 		dev_err(&pdev->dev, "no registers/irq defined\n");
 		return -EINVAL;
 	}

 	uart.port.membase = devm_ioremap(&pdev->dev, regs->start,
 					 resource_size(regs));
 	if (!uart.port.membase)
 		return -ENOMEM;

 	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
 	if (!data)
 		return -ENOMEM;

 	if (pdev->dev.of_node) {
 		err = mtk8250_probe_of(pdev, &uart.port, data);
 		if (err)
 			return err;
 	} else
 		return -ENODEV;

 	spin_lock_init(&uart.port.lock);
 	uart.port.mapbase = regs->start;
 	uart.port.irq = irq->start;
 	uart.port.pm = mtk8250_do_pm;
 	uart.port.type = PORT_16550;
 	uart.port.flags = UPF_BOOT_AUTOCONF | UPF_FIXED_PORT;
 	uart.port.dev = &pdev->dev;
 	uart.port.iotype = UPIO_MEM32;
 	uart.port.regshift = 2;
 	uart.port.private_data = data;
 	uart.port.shutdown = mtk8250_shutdown;
 	uart.port.startup = mtk8250_startup;
 	uart.port.set_termios = mtk8250_set_termios;
 	uart.port.uartclk = clk_get_rate(data->uart_clk);
 #ifdef CONFIG_SERIAL_8250_DMA
 	if (data->dma)
 		uart.dma = data->dma;
 #endif

 	/* Disable Rate Fix function */
 	writel(0x0, uart.port.membase +
 			(MTK_UART_RATE_FIX << uart.port.regshift));

 	platform_set_drvdata(pdev, data);

 	err = mtk8250_runtime_resume(&pdev->dev);
 	if (err)
 		return err;

 	data->line = serial8250_register_8250_port(&uart);
 	if (data->line < 0)
 		return data->line;

 	pm_runtime_set_active(&pdev->dev);
 	pm_runtime_enable(&pdev->dev);

 	return 0;
 }

 static int mtk8250_remove(struct platform_device *pdev)
 {
 	struct mtk8250_data *data = platform_get_drvdata(pdev);

 	pm_runtime_get_sync(&pdev->dev);

 	serial8250_unregister_port(data->line);
 	mtk8250_runtime_suspend(&pdev->dev);

 	pm_runtime_disable(&pdev->dev);
 	pm_runtime_put_noidle(&pdev->dev);

 	return 0;
 }

 static int __maybe_unused mtk8250_suspend(struct device *dev)
 {
 	struct mtk8250_data *data = dev_get_drvdata(dev);

 	serial8250_suspend_port(data->line);

 	return 0;
 }

 static int __maybe_unused mtk8250_resume(struct device *dev)
 {
 	struct mtk8250_data *data = dev_get_drvdata(dev);

 	serial8250_resume_port(data->line);

 	return 0;
 }

 static const struct dev_pm_ops mtk8250_pm_ops = {
 	SET_SYSTEM_SLEEP_PM_OPS(mtk8250_suspend, mtk8250_resume)
 	SET_RUNTIME_PM_OPS(mtk8250_runtime_suspend, mtk8250_runtime_resume,
 				NULL)
 };

 static const struct of_device_id mtk8250_of_match[] = {
 	{ .compatible = "mediatek,mt6577-uart" },
 	{ /* Sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, mtk8250_of_match);

 static struct platform_driver mtk8250_platform_driver = {
 	.driver = {
 		.name		= "mt6577-uart",
 		.pm		= &mtk8250_pm_ops,
 		.of_match_table	= mtk8250_of_match,
 	},
 	.probe			= mtk8250_probe,
 	.remove			= mtk8250_remove,
 };
 module_platform_driver(mtk8250_platform_driver);

 #ifdef CONFIG_SERIAL_8250_CONSOLE
 static int __init early_mtk8250_setup(struct earlycon_device *device,
 					const char *options)
 {
 	if (!device->port.membase)
 		return -ENODEV;

 	device->port.iotype = UPIO_MEM32;

 	return early_serial8250_setup(device, NULL);
 }

 OF_EARLYCON_DECLARE(mtk8250, "mediatek,mt6577-uart", early_mtk8250_setup);
 #endif

 MODULE_AUTHOR("Matthias Brugger");
 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("Mediatek 8250 serial port driver");
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* Mediatek 8250 driver.
	*
	* Copyright (c) 2014 MundoReader S.L.
	* Author: Matthias Brugger <matthias.bgg@gmail.com>
	*/
	#include <linux/clk.h>
	#include <linux/io.h>
	#include <linux/module.h>
	#include <linux/of_irq.h>
	#include <linux/of_platform.h>
	#include <linux/platform_device.h>
	#include <linux/pm_runtime.h>
	#include <linux/serial_8250.h>
	#include <linux/serial_reg.h>
	#include <linux/console.h>
	#include <linux/dma-mapping.h>
	#include <linux/tty.h>
	#include <linux/tty_flip.h>

	#include "8250.h"

	#define UART_MTK_HIGHS 0x09 /* Highspeed register */
	#define UART_MTK_SAMPLE_COUNT 0x0a /* Sample count register */
	#define UART_MTK_SAMPLE_POINT 0x0b /* Sample point register */
	#define MTK_UART_RATE_FIX 0x0d /* UART Rate Fix Register */

	#define MTK_UART_DMA_EN 0x13 /* DMA Enable register */
	#define MTK_UART_DMA_EN_TX 0x2
	#define MTK_UART_DMA_EN_RX 0x5

	#define MTK_UART_TX_SIZE UART_XMIT_SIZE
	#define MTK_UART_RX_SIZE 0x8000
	#define MTK_UART_TX_TRIGGER 1
	#define MTK_UART_RX_TRIGGER MTK_UART_RX_SIZE

	#ifdef CONFIG_SERIAL_8250_DMA
	enum dma_rx_status {
	DMA_RX_START = 0,
	DMA_RX_RUNNING = 1,
	DMA_RX_SHUTDOWN = 2,
	};
	#endif

	struct mtk8250_data {
	int line;
	unsigned int rx_pos;
	struct clk *uart_clk;
	struct clk *bus_clk;
	struct uart_8250_dma *dma;
	#ifdef CONFIG_SERIAL_8250_DMA
	enum dma_rx_status rx_status;
	#endif
	};

	#ifdef CONFIG_SERIAL_8250_DMA
	static void mtk8250_rx_dma(struct uart_8250_port *up);

	static void mtk8250_dma_rx_complete(void *param)
	{
	struct uart_8250_port *up = param;
	struct uart_8250_dma *dma = up->dma;
	struct mtk8250_data *data = up->port.private_data;
	struct tty_port *tty_port = &up->port.state->port;
	struct dma_tx_state state;
	unsigned char *ptr;
	int copied;

	dma_sync_single_for_cpu(dma->rxchan->device->dev, dma->rx_addr,
	dma->rx_size, DMA_FROM_DEVICE);

	dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);

	if (data->rx_status == DMA_RX_SHUTDOWN)
	return;

	if ((data->rx_pos + state.residue) <= dma->rx_size) {
	ptr = (unsigned char *)(data->rx_pos + dma->rx_buf);
	copied = tty_insert_flip_string(tty_port, ptr, state.residue);
	} else {
	ptr = (unsigned char *)(data->rx_pos + dma->rx_buf);
	copied = tty_insert_flip_string(tty_port, ptr,
	dma->rx_size - data->rx_pos);
	ptr = (unsigned char *)(dma->rx_buf);
	copied += tty_insert_flip_string(tty_port, ptr,
	data->rx_pos + state.residue - dma->rx_size);
	}
	up->port.icount.rx += copied;

	tty_flip_buffer_push(tty_port);

	mtk8250_rx_dma(up);
	}

	static void mtk8250_rx_dma(struct uart_8250_port *up)
	{
	struct uart_8250_dma *dma = up->dma;
	struct mtk8250_data *data = up->port.private_data;
	struct dma_async_tx_descriptor *desc;
	struct dma_tx_state state;

	desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr,
	dma->rx_size, DMA_DEV_TO_MEM,
	DMA_PREP_INTERRUPT \| DMA_CTRL_ACK);
	if (!desc) {
	pr_err("failed to prepare rx slave single\n");
	return;
	}

	desc->callback = mtk8250_dma_rx_complete;
	desc->callback_param = up;

	dma->rx_cookie = dmaengine_submit(desc);

	dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
	data->rx_pos = state.residue;

	dma_sync_single_for_device(dma->rxchan->device->dev, dma->rx_addr,
	dma->rx_size, DMA_FROM_DEVICE);

	dma_async_issue_pending(dma->rxchan);
	}

	static void mtk8250_dma_enable(struct uart_8250_port *up)
	{
	struct uart_8250_dma *dma = up->dma;
	struct mtk8250_data *data = up->port.private_data;
	int lcr = serial_in(up, UART_LCR);

	if (data->rx_status != DMA_RX_START)
	return;

	dma->rxconf.direction = DMA_DEV_TO_MEM;
	dma->rxconf.src_addr_width = dma->rx_size / 1024;
	dma->rxconf.src_addr = dma->rx_addr;

	dma->txconf.direction = DMA_MEM_TO_DEV;
	dma->txconf.dst_addr_width = MTK_UART_TX_SIZE / 1024;
	dma->txconf.dst_addr = dma->tx_addr;

	serial_out(up, UART_FCR, UART_FCR_ENABLE_FIFO \| UART_FCR_CLEAR_RCVR \|
	UART_FCR_CLEAR_XMIT);
	serial_out(up, MTK_UART_DMA_EN,
	MTK_UART_DMA_EN_RX \| MTK_UART_DMA_EN_TX);

	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
	serial_out(up, UART_EFR, UART_EFR_ECB);
	serial_out(up, UART_LCR, lcr);

	if (dmaengine_slave_config(dma->rxchan, &dma->rxconf) != 0)
	pr_err("failed to configure rx dma channel\n");
	if (dmaengine_slave_config(dma->txchan, &dma->txconf) != 0)
	pr_err("failed to configure tx dma channel\n");

	data->rx_status = DMA_RX_RUNNING;
	data->rx_pos = 0;
	mtk8250_rx_dma(up);
	}
	#endif

	static int mtk8250_startup(struct uart_port *port)
	{
	#ifdef CONFIG_SERIAL_8250_DMA
	struct uart_8250_port *up = up_to_u8250p(port);
	struct mtk8250_data *data = port->private_data;

	/* disable DMA for console */
	if (uart_console(port))
	up->dma = NULL;

	if (up->dma) {
	data->rx_status = DMA_RX_START;
	uart_circ_clear(&port->state->xmit);
	}
	#endif
	memset(&port->icount, 0, sizeof(port->icount));

	return serial8250_do_startup(port);
	}

	static void mtk8250_shutdown(struct uart_port *port)
	{
	#ifdef CONFIG_SERIAL_8250_DMA
	struct uart_8250_port *up = up_to_u8250p(port);
	struct mtk8250_data *data = port->private_data;

	if (up->dma)
	data->rx_status = DMA_RX_SHUTDOWN;
	#endif

	return serial8250_do_shutdown(port);
	}

	static void
	mtk8250_set_termios(struct uart_port port, struct ktermios termios,
	struct ktermios *old)
	{
	struct uart_8250_port *up = up_to_u8250p(port);
	unsigned long flags;
	unsigned int baud, quot;

	#ifdef CONFIG_SERIAL_8250_DMA
	if (up->dma) {
	if (uart_console(port)) {
	devm_kfree(up->port.dev, up->dma);
	up->dma = NULL;
	} else {
	mtk8250_dma_enable(up);
	}
	}
	#endif

	serial8250_do_set_termios(port, termios, old);

	/*
	* Mediatek UARTs use an extra highspeed register (UART_MTK_HIGHS)
	*
	* We need to recalcualte the quot register, as the claculation depends
	* on the vaule in the highspeed register.
	*
	* Some baudrates are not supported by the chip, so we use the next
	* lower rate supported and update termios c_flag.
	*
	* If highspeed register is set to 3, we need to specify sample count
	* and sample point to increase accuracy. If not, we reset the
	* registers to their default values.
	*/
	baud = uart_get_baud_rate(port, termios, old,
	port->uartclk / 16 / UART_DIV_MAX,
	port->uartclk);

	if (baud <= 115200) {
	serial_port_out(port, UART_MTK_HIGHS, 0x0);
	quot = uart_get_divisor(port, baud);
	} else if (baud <= 576000) {
	serial_port_out(port, UART_MTK_HIGHS, 0x2);

	/* Set to next lower baudrate supported */
	if ((baud == 500000) \|\| (baud == 576000))
	baud = 460800;
	quot = DIV_ROUND_UP(port->uartclk, 4 * baud);
	} else {
	serial_port_out(port, UART_MTK_HIGHS, 0x3);
	quot = DIV_ROUND_UP(port->uartclk, 256 * baud);
	}

	/*
	* Ok, we're now changing the port state. Do it with
	* interrupts disabled.
	*/
	spin_lock_irqsave(&port->lock, flags);

	/* set DLAB we have cval saved in up->lcr from the call to the core */
	serial_port_out(port, UART_LCR, up->lcr \| UART_LCR_DLAB);
	serial_dl_write(up, quot);

	/* reset DLAB */
	serial_port_out(port, UART_LCR, up->lcr);

	if (baud > 460800) {
	unsigned int tmp;

	tmp = DIV_ROUND_CLOSEST(port->uartclk, quot * baud);
	serial_port_out(port, UART_MTK_SAMPLE_COUNT, tmp - 1);
	serial_port_out(port, UART_MTK_SAMPLE_POINT,
	(tmp - 2) >> 1);
	} else {
	serial_port_out(port, UART_MTK_SAMPLE_COUNT, 0x00);
	serial_port_out(port, UART_MTK_SAMPLE_POINT, 0xff);
	}

	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 int __maybe_unused mtk8250_runtime_suspend(struct device *dev)
	{
	struct mtk8250_data *data = dev_get_drvdata(dev);

	clk_disable_unprepare(data->uart_clk);
	clk_disable_unprepare(data->bus_clk);

	return 0;
	}

	static int __maybe_unused mtk8250_runtime_resume(struct device *dev)
	{
	struct mtk8250_data *data = dev_get_drvdata(dev);
	int err;

	err = clk_prepare_enable(data->uart_clk);
	if (err) {
	dev_warn(dev, "Can't enable clock\n");
	return err;
	}

	err = clk_prepare_enable(data->bus_clk);
	if (err) {
	dev_warn(dev, "Can't enable bus clock\n");
	return err;
	}

	return 0;
	}

	static void
	mtk8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old)
	{
	if (!state)
	pm_runtime_get_sync(port->dev);

	serial8250_do_pm(port, state, old);

	if (state)
	pm_runtime_put_sync_suspend(port->dev);
	}

	#ifdef CONFIG_SERIAL_8250_DMA
	static bool mtk8250_dma_filter(struct dma_chan chan, void param)
	{
	return false;
	}
	#endif

	static int mtk8250_probe_of(struct platform_device pdev, struct uart_port p,
	struct mtk8250_data *data)
	{
	#ifdef CONFIG_SERIAL_8250_DMA
	int dmacnt;
	#endif

	data->uart_clk = devm_clk_get(&pdev->dev, "baud");
	if (IS_ERR(data->uart_clk)) {
	/*
	* For compatibility with older device trees try unnamed
	* clk when no baud clk can be found.
	*/
	data->uart_clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(data->uart_clk)) {
	dev_warn(&pdev->dev, "Can't get uart clock\n");
	return PTR_ERR(data->uart_clk);
	}

	return 0;
	}

	data->bus_clk = devm_clk_get(&pdev->dev, "bus");
	if (IS_ERR(data->bus_clk))
	return PTR_ERR(data->bus_clk);

	data->dma = NULL;
	#ifdef CONFIG_SERIAL_8250_DMA
	dmacnt = of_property_count_strings(pdev->dev.of_node, "dma-names");
	if (dmacnt == 2) {
	data->dma = devm_kzalloc(&pdev->dev, sizeof(*data->dma),
	GFP_KERNEL);
	if (!data->dma)
	return -ENOMEM;

	data->dma->fn = mtk8250_dma_filter;
	data->dma->rx_size = MTK_UART_RX_SIZE;
	data->dma->rxconf.src_maxburst = MTK_UART_RX_TRIGGER;
	data->dma->txconf.dst_maxburst = MTK_UART_TX_TRIGGER;
	}
	#endif

	return 0;
	}

	static int mtk8250_probe(struct platform_device *pdev)
	{
	struct uart_8250_port uart = {};
	struct resource *regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	struct resource *irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
	struct mtk8250_data *data;
	int err;

	if (!regs \|\| !irq) {
	dev_err(&pdev->dev, "no registers/irq defined\n");
	return -EINVAL;
	}

	uart.port.membase = devm_ioremap(&pdev->dev, regs->start,
	resource_size(regs));
	if (!uart.port.membase)
	return -ENOMEM;

	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
	if (!data)
	return -ENOMEM;

	if (pdev->dev.of_node) {
	err = mtk8250_probe_of(pdev, &uart.port, data);
	if (err)
	return err;
	} else
	return -ENODEV;

	spin_lock_init(&uart.port.lock);
	uart.port.mapbase = regs->start;
	uart.port.irq = irq->start;
	uart.port.pm = mtk8250_do_pm;
	uart.port.type = PORT_16550;
	uart.port.flags = UPF_BOOT_AUTOCONF \| UPF_FIXED_PORT;
	uart.port.dev = &pdev->dev;
	uart.port.iotype = UPIO_MEM32;
	uart.port.regshift = 2;
	uart.port.private_data = data;
	uart.port.shutdown = mtk8250_shutdown;
	uart.port.startup = mtk8250_startup;
	uart.port.set_termios = mtk8250_set_termios;
	uart.port.uartclk = clk_get_rate(data->uart_clk);
	#ifdef CONFIG_SERIAL_8250_DMA
	if (data->dma)
	uart.dma = data->dma;
	#endif

	/* Disable Rate Fix function */
	writel(0x0, uart.port.membase +
	(MTK_UART_RATE_FIX << uart.port.regshift));

	platform_set_drvdata(pdev, data);

	err = mtk8250_runtime_resume(&pdev->dev);
	if (err)
	return err;

	data->line = serial8250_register_8250_port(&uart);
	if (data->line < 0)
	return data->line;

	pm_runtime_set_active(&pdev->dev);
	pm_runtime_enable(&pdev->dev);

	return 0;
	}

	static int mtk8250_remove(struct platform_device *pdev)
	{
	struct mtk8250_data *data = platform_get_drvdata(pdev);

	pm_runtime_get_sync(&pdev->dev);

	serial8250_unregister_port(data->line);
	mtk8250_runtime_suspend(&pdev->dev);

	pm_runtime_disable(&pdev->dev);
	pm_runtime_put_noidle(&pdev->dev);

	return 0;
	}

	static int __maybe_unused mtk8250_suspend(struct device *dev)
	{
	struct mtk8250_data *data = dev_get_drvdata(dev);

	serial8250_suspend_port(data->line);

	return 0;
	}

	static int __maybe_unused mtk8250_resume(struct device *dev)
	{
	struct mtk8250_data *data = dev_get_drvdata(dev);

	serial8250_resume_port(data->line);

	return 0;
	}

	static const struct dev_pm_ops mtk8250_pm_ops = {
	SET_SYSTEM_SLEEP_PM_OPS(mtk8250_suspend, mtk8250_resume)
	SET_RUNTIME_PM_OPS(mtk8250_runtime_suspend, mtk8250_runtime_resume,
	NULL)
	};

	static const struct of_device_id mtk8250_of_match[] = {
	{ .compatible = "mediatek,mt6577-uart" },
	{ /* Sentinel */ }
	};
	MODULE_DEVICE_TABLE(of, mtk8250_of_match);

	static struct platform_driver mtk8250_platform_driver = {
	.driver = {
	.name = "mt6577-uart",
	.pm = &mtk8250_pm_ops,
	.of_match_table = mtk8250_of_match,
	},
	.probe = mtk8250_probe,
	.remove = mtk8250_remove,
	};
	module_platform_driver(mtk8250_platform_driver);

	#ifdef CONFIG_SERIAL_8250_CONSOLE
	static int __init early_mtk8250_setup(struct earlycon_device *device,
	const char *options)
	{
	if (!device->port.membase)
	return -ENODEV;

	device->port.iotype = UPIO_MEM32;

	return early_serial8250_setup(device, NULL);
	}

	OF_EARLYCON_DECLARE(mtk8250, "mediatek,mt6577-uart", early_mtk8250_setup);
	#endif

	MODULE_AUTHOR("Matthias Brugger");
	MODULE_LICENSE("GPL");
	MODULE_DESCRIPTION("Mediatek 8250 serial port driver");