drivers/tty/serial/8250/8250_dw.c - arm/linux-arm64-legacy - Git at Google

 /*
  * Synopsys DesignWare 8250 driver.
  *
  * Copyright 2011 Picochip, Jamie Iles.
  * Copyright 2013 Intel Corporation
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * The Synopsys DesignWare 8250 has an extra feature whereby it detects if the
  * LCR is written whilst busy.  If it is, then a busy detect interrupt is
  * raised, the LCR needs to be rewritten and the uart status register read.
  */
 #include <linux/device.h>
 #include <linux/io.h>
 #include <linux/module.h>
 #include <linux/serial_8250.h>
 #include <linux/serial_core.h>
 #include <linux/serial_reg.h>
 #include <linux/of.h>
 #include <linux/of_irq.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
 #include <linux/slab.h>
 #include <linux/acpi.h>
 #include <linux/clk.h>
 #include <linux/pm_runtime.h>

 #include <asm/byteorder.h>

 #include "8250.h"

 /* Offsets for the DesignWare specific registers */
 #define DW_UART_USR	0x1f /* UART Status Register */
 #define DW_UART_CPR	0xf4 /* Component Parameter Register */
 #define DW_UART_UCV	0xf8 /* UART Component Version */

 /* Component Parameter Register bits */
 #define DW_UART_CPR_ABP_DATA_WIDTH	(3 << 0)
 #define DW_UART_CPR_AFCE_MODE		(1 << 4)
 #define DW_UART_CPR_THRE_MODE		(1 << 5)
 #define DW_UART_CPR_SIR_MODE		(1 << 6)
 #define DW_UART_CPR_SIR_LP_MODE		(1 << 7)
 #define DW_UART_CPR_ADDITIONAL_FEATURES	(1 << 8)
 #define DW_UART_CPR_FIFO_ACCESS		(1 << 9)
 #define DW_UART_CPR_FIFO_STAT		(1 << 10)
 #define DW_UART_CPR_SHADOW		(1 << 11)
 #define DW_UART_CPR_ENCODED_PARMS	(1 << 12)
 #define DW_UART_CPR_DMA_EXTRA		(1 << 13)
 #define DW_UART_CPR_FIFO_MODE		(0xff << 16)
 /* Helper for fifo size calculation */
 #define DW_UART_CPR_FIFO_SIZE(a)	(((a >> 16) & 0xff) * 16)


 struct dw8250_data {
 	u8			usr_reg;
 	int			last_mcr;
 	int			line;
 	struct clk		*clk;
 	struct uart_8250_dma	dma;
 };

 static inline int dw8250_modify_msr(struct uart_port *p, int offset, int value)
 {
 	struct dw8250_data *d = p->private_data;

 	/* If reading MSR, report CTS asserted when auto-CTS/RTS enabled */
 	if (offset == UART_MSR && d->last_mcr & UART_MCR_AFE) {
 		value |= UART_MSR_CTS;
 		value &= ~UART_MSR_DCTS;
 	}

 	return value;
 }

 static void dw8250_force_idle(struct uart_port *p)
 {
 	serial8250_clear_and_reinit_fifos(container_of
 					  (p, struct uart_8250_port, port));
 	(void)p->serial_in(p, UART_RX);
 }

 static void dw8250_serial_out(struct uart_port *p, int offset, int value)
 {
 	struct dw8250_data *d = p->private_data;

 	if (offset == UART_MCR)
 		d->last_mcr = value;

 	writeb(value, p->membase + (offset << p->regshift));

 	/* Make sure LCR write wasn't ignored */
 	if (offset == UART_LCR) {
 		int tries = 1000;
 		while (tries--) {
 			unsigned int lcr = p->serial_in(p, UART_LCR);
 			if ((value & ~UART_LCR_SPAR) == (lcr & ~UART_LCR_SPAR))
 				return;
 			dw8250_force_idle(p);
 			writeb(value, p->membase + (UART_LCR << p->regshift));
 		}
 		dev_err(p->dev, "Couldn't set LCR to %d\n", value);
 	}
 }

 static unsigned int dw8250_serial_in(struct uart_port *p, int offset)
 {
 	unsigned int value = readb(p->membase + (offset << p->regshift));

 	return dw8250_modify_msr(p, offset, value);
 }

 /* Read Back (rb) version to ensure register access ording. */
 static void dw8250_serial_out_rb(struct uart_port *p, int offset, int value)
 {
 	dw8250_serial_out(p, offset, value);
 	dw8250_serial_in(p, UART_LCR);
 }

 static void dw8250_serial_out32(struct uart_port *p, int offset, int value)
 {
 	struct dw8250_data *d = p->private_data;

 	if (offset == UART_MCR)
 		d->last_mcr = value;

 	writel(value, p->membase + (offset << p->regshift));

 	/* Make sure LCR write wasn't ignored */
 	if (offset == UART_LCR) {
 		int tries = 1000;
 		while (tries--) {
 			unsigned int lcr = p->serial_in(p, UART_LCR);
 			if ((value & ~UART_LCR_SPAR) == (lcr & ~UART_LCR_SPAR))
 				return;
 			dw8250_force_idle(p);
 			writel(value, p->membase + (UART_LCR << p->regshift));
 		}
 		dev_err(p->dev, "Couldn't set LCR to %d\n", value);
 	}
 }

 static unsigned int dw8250_serial_in32(struct uart_port *p, int offset)
 {
 	unsigned int value = readl(p->membase + (offset << p->regshift));

 	return dw8250_modify_msr(p, offset, value);
 }

 static int dw8250_handle_irq(struct uart_port *p)
 {
 	struct dw8250_data *d = p->private_data;
 	unsigned int iir = p->serial_in(p, UART_IIR);

 	if (serial8250_handle_irq(p, iir)) {
 		return 1;
 	} else if ((iir & UART_IIR_BUSY) == UART_IIR_BUSY) {
 		/* Clear the USR */
 		(void)p->serial_in(p, d->usr_reg);

 		return 1;
 	}

 	return 0;
 }

 static void
 dw8250_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);
 }

 static bool dw8250_dma_filter(struct dma_chan *chan, void *param)
 {
 	struct dw8250_data *data = param;

 	return chan->chan_id == data->dma.tx_chan_id ||
 	       chan->chan_id == data->dma.rx_chan_id;
 }

 static void dw8250_setup_port(struct uart_8250_port *up)
 {
 	struct uart_port	*p = &up->port;
 	u32			reg = readl(p->membase + DW_UART_UCV);

 	/*
 	 * If the Component Version Register returns zero, we know that
 	 * ADDITIONAL_FEATURES are not enabled. No need to go any further.
 	 */
 	if (!reg)
 		return;

 	dev_dbg_ratelimited(p->dev, "Designware UART version %c.%c%c\n",
 		(reg >> 24) & 0xff, (reg >> 16) & 0xff, (reg >> 8) & 0xff);

 	reg = readl(p->membase + DW_UART_CPR);
 	if (!reg)
 		return;

 	/* Select the type based on fifo */
 	if (reg & DW_UART_CPR_FIFO_MODE) {
 		p->type = PORT_16550A;
 		p->flags |= UPF_FIXED_TYPE;
 		p->fifosize = DW_UART_CPR_FIFO_SIZE(reg);
 		up->tx_loadsz = p->fifosize;
 		up->capabilities = UART_CAP_FIFO;
 	}

 	if (reg & DW_UART_CPR_AFCE_MODE)
 		up->capabilities |= UART_CAP_AFE;
 }

 static int dw8250_probe_of(struct uart_port *p,
 			   struct dw8250_data *data)
 {
 	struct device_node	*np = p->dev->of_node;
 	u32			val;
 	bool has_ucv = true;

 	if (of_device_is_compatible(np, "cavium,octeon-3860-uart")) {
 #ifdef __BIG_ENDIAN
 		/*
 		 * Low order bits of these 64-bit registers, when
 		 * accessed as a byte, are 7 bytes further down in the
 		 * address space in big endian mode.
 		 */
 		p->membase += 7;
 #endif
 		p->serial_out = dw8250_serial_out_rb;
 		p->flags = ASYNC_SKIP_TEST | UPF_SHARE_IRQ | UPF_FIXED_TYPE;
 		p->type = PORT_OCTEON;
 		data->usr_reg = 0x27;
 		has_ucv = false;
 	} else if (!of_property_read_u32(np, "reg-io-width", &val)) {
 		switch (val) {
 		case 1:
 			break;
 		case 4:
 			p->iotype = UPIO_MEM32;
 			p->serial_in = dw8250_serial_in32;
 			p->serial_out = dw8250_serial_out32;
 			break;
 		default:
 			dev_err(p->dev, "unsupported reg-io-width (%u)\n", val);
 			return -EINVAL;
 		}
 	}
 	if (has_ucv)
 		dw8250_setup_port(container_of(p, struct uart_8250_port, port));

 	if (!of_property_read_u32(np, "reg-shift", &val))
 		p->regshift = val;

 	/* clock got configured through clk api, all done */
 	if (p->uartclk)
 		return 0;

 	/* try to find out clock frequency from DT as fallback */
 	if (of_property_read_u32(np, "clock-frequency", &val)) {
 		dev_err(p->dev, "clk or clock-frequency not defined\n");
 		return -EINVAL;
 	}
 	p->uartclk = val;

 	return 0;
 }

 static int dw8250_probe_acpi(struct uart_8250_port *up,
 			     struct dw8250_data *data)
 {
 	const struct acpi_device_id *id;
 	struct uart_port *p = &up->port;

 	dw8250_setup_port(up);

 	id = acpi_match_device(p->dev->driver->acpi_match_table, p->dev);
 	if (!id)
 		return -ENODEV;

 	p->iotype = UPIO_MEM32;
 	p->serial_in = dw8250_serial_in32;
 	p->serial_out = dw8250_serial_out32;
 	p->regshift = 2;

 	if (!p->uartclk)
 		p->uartclk = (unsigned int)id->driver_data;

 	up->dma = &data->dma;

 	up->dma->rxconf.src_maxburst = p->fifosize / 4;
 	up->dma->txconf.dst_maxburst = p->fifosize / 4;

 	return 0;
 }

 static int dw8250_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 dw8250_data *data;
 	int err;

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

 	spin_lock_init(&uart.port.lock);
 	uart.port.mapbase = regs->start;
 	uart.port.irq = irq->start;
 	uart.port.handle_irq = dw8250_handle_irq;
 	uart.port.pm = dw8250_do_pm;
 	uart.port.type = PORT_8250;
 	uart.port.flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF | UPF_FIXED_PORT;
 	uart.port.dev = &pdev->dev;

 	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;

 	data->usr_reg = DW_UART_USR;
 	data->clk = devm_clk_get(&pdev->dev, NULL);
 	if (!IS_ERR(data->clk)) {
 		clk_prepare_enable(data->clk);
 		uart.port.uartclk = clk_get_rate(data->clk);
 	}

 	data->dma.rx_chan_id = -1;
 	data->dma.tx_chan_id = -1;
 	data->dma.rx_param = data;
 	data->dma.tx_param = data;
 	data->dma.fn = dw8250_dma_filter;

 	uart.port.iotype = UPIO_MEM;
 	uart.port.serial_in = dw8250_serial_in;
 	uart.port.serial_out = dw8250_serial_out;
 	uart.port.private_data = data;

 	if (pdev->dev.of_node) {
 		err = dw8250_probe_of(&uart.port, data);
 		if (err)
 			return err;
 	} else if (ACPI_HANDLE(&pdev->dev)) {
 		err = dw8250_probe_acpi(&uart, data);
 		if (err)
 			return err;
 	} else {
 		return -ENODEV;
 	}

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

 	platform_set_drvdata(pdev, data);

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

 	return 0;
 }

 static int dw8250_remove(struct platform_device *pdev)
 {
 	struct dw8250_data *data = platform_get_drvdata(pdev);

 	pm_runtime_get_sync(&pdev->dev);

 	serial8250_unregister_port(data->line);

 	if (!IS_ERR(data->clk))
 		clk_disable_unprepare(data->clk);

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

 	return 0;
 }

 #ifdef CONFIG_PM_SLEEP
 static int dw8250_suspend(struct device *dev)
 {
 	struct dw8250_data *data = dev_get_drvdata(dev);

 	serial8250_suspend_port(data->line);

 	return 0;
 }

 static int dw8250_resume(struct device *dev)
 {
 	struct dw8250_data *data = dev_get_drvdata(dev);

 	serial8250_resume_port(data->line);

 	return 0;
 }
 #endif /* CONFIG_PM_SLEEP */

 #ifdef CONFIG_PM_RUNTIME
 static int dw8250_runtime_suspend(struct device *dev)
 {
 	struct dw8250_data *data = dev_get_drvdata(dev);

 	if (!IS_ERR(data->clk))
 		clk_disable_unprepare(data->clk);

 	return 0;
 }

 static int dw8250_runtime_resume(struct device *dev)
 {
 	struct dw8250_data *data = dev_get_drvdata(dev);

 	if (!IS_ERR(data->clk))
 		clk_prepare_enable(data->clk);

 	return 0;
 }
 #endif

 static const struct dev_pm_ops dw8250_pm_ops = {
 	SET_SYSTEM_SLEEP_PM_OPS(dw8250_suspend, dw8250_resume)
 	SET_RUNTIME_PM_OPS(dw8250_runtime_suspend, dw8250_runtime_resume, NULL)
 };

 static const struct of_device_id dw8250_of_match[] = {
 	{ .compatible = "snps,dw-apb-uart" },
 	{ .compatible = "cavium,octeon-3860-uart" },
 	{ /* Sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, dw8250_of_match);

 static const struct acpi_device_id dw8250_acpi_match[] = {
 	{ "INT33C4", 0 },
 	{ "INT33C5", 0 },
 	{ "INT3434", 0 },
 	{ "INT3435", 0 },
 	{ "80860F0A", 0 },
 	{ },
 };
 MODULE_DEVICE_TABLE(acpi, dw8250_acpi_match);

 static struct platform_driver dw8250_platform_driver = {
 	.driver = {
 		.name		= "dw-apb-uart",
 		.owner		= THIS_MODULE,
 		.pm		= &dw8250_pm_ops,
 		.of_match_table	= dw8250_of_match,
 		.acpi_match_table = ACPI_PTR(dw8250_acpi_match),
 	},
 	.probe			= dw8250_probe,
 	.remove			= dw8250_remove,
 };

 module_platform_driver(dw8250_platform_driver);

 MODULE_AUTHOR("Jamie Iles");
 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("Synopsys DesignWare 8250 serial port driver");
	/*
	* Synopsys DesignWare 8250 driver.
	*
	* Copyright 2011 Picochip, Jamie Iles.
	* Copyright 2013 Intel Corporation
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* The Synopsys DesignWare 8250 has an extra feature whereby it detects if the
	* LCR is written whilst busy. If it is, then a busy detect interrupt is
	* raised, the LCR needs to be rewritten and the uart status register read.
	*/
	#include <linux/device.h>
	#include <linux/io.h>
	#include <linux/module.h>
	#include <linux/serial_8250.h>
	#include <linux/serial_core.h>
	#include <linux/serial_reg.h>
	#include <linux/of.h>
	#include <linux/of_irq.h>
	#include <linux/of_platform.h>
	#include <linux/platform_device.h>
	#include <linux/slab.h>
	#include <linux/acpi.h>
	#include <linux/clk.h>
	#include <linux/pm_runtime.h>

	#include <asm/byteorder.h>

	#include "8250.h"

	/* Offsets for the DesignWare specific registers */
	#define DW_UART_USR 0x1f /* UART Status Register */
	#define DW_UART_CPR 0xf4 /* Component Parameter Register */
	#define DW_UART_UCV 0xf8 /* UART Component Version */

	/* Component Parameter Register bits */
	#define DW_UART_CPR_ABP_DATA_WIDTH (3 << 0)
	#define DW_UART_CPR_AFCE_MODE (1 << 4)
	#define DW_UART_CPR_THRE_MODE (1 << 5)
	#define DW_UART_CPR_SIR_MODE (1 << 6)
	#define DW_UART_CPR_SIR_LP_MODE (1 << 7)
	#define DW_UART_CPR_ADDITIONAL_FEATURES (1 << 8)
	#define DW_UART_CPR_FIFO_ACCESS (1 << 9)
	#define DW_UART_CPR_FIFO_STAT (1 << 10)
	#define DW_UART_CPR_SHADOW (1 << 11)
	#define DW_UART_CPR_ENCODED_PARMS (1 << 12)
	#define DW_UART_CPR_DMA_EXTRA (1 << 13)
	#define DW_UART_CPR_FIFO_MODE (0xff << 16)
	/* Helper for fifo size calculation */
	#define DW_UART_CPR_FIFO_SIZE(a) (((a >> 16) & 0xff) * 16)


	struct dw8250_data {
	u8 usr_reg;
	int last_mcr;
	int line;
	struct clk *clk;
	struct uart_8250_dma dma;
	};

	static inline int dw8250_modify_msr(struct uart_port *p, int offset, int value)
	{
	struct dw8250_data *d = p->private_data;

	/* If reading MSR, report CTS asserted when auto-CTS/RTS enabled */
	if (offset == UART_MSR && d->last_mcr & UART_MCR_AFE) {
	value \|= UART_MSR_CTS;
	value &= ~UART_MSR_DCTS;
	}

	return value;
	}

	static void dw8250_force_idle(struct uart_port *p)
	{
	serial8250_clear_and_reinit_fifos(container_of
	(p, struct uart_8250_port, port));
	(void)p->serial_in(p, UART_RX);
	}

	static void dw8250_serial_out(struct uart_port *p, int offset, int value)
	{
	struct dw8250_data *d = p->private_data;

	if (offset == UART_MCR)
	d->last_mcr = value;

	writeb(value, p->membase + (offset << p->regshift));

	/* Make sure LCR write wasn't ignored */
	if (offset == UART_LCR) {
	int tries = 1000;
	while (tries--) {
	unsigned int lcr = p->serial_in(p, UART_LCR);
	if ((value & ~UART_LCR_SPAR) == (lcr & ~UART_LCR_SPAR))
	return;
	dw8250_force_idle(p);
	writeb(value, p->membase + (UART_LCR << p->regshift));
	}
	dev_err(p->dev, "Couldn't set LCR to %d\n", value);
	}
	}

	static unsigned int dw8250_serial_in(struct uart_port *p, int offset)
	{
	unsigned int value = readb(p->membase + (offset << p->regshift));

	return dw8250_modify_msr(p, offset, value);
	}

	/* Read Back (rb) version to ensure register access ording. */
	static void dw8250_serial_out_rb(struct uart_port *p, int offset, int value)
	{
	dw8250_serial_out(p, offset, value);
	dw8250_serial_in(p, UART_LCR);
	}

	static void dw8250_serial_out32(struct uart_port *p, int offset, int value)
	{
	struct dw8250_data *d = p->private_data;

	if (offset == UART_MCR)
	d->last_mcr = value;

	writel(value, p->membase + (offset << p->regshift));

	/* Make sure LCR write wasn't ignored */
	if (offset == UART_LCR) {
	int tries = 1000;
	while (tries--) {
	unsigned int lcr = p->serial_in(p, UART_LCR);
	if ((value & ~UART_LCR_SPAR) == (lcr & ~UART_LCR_SPAR))
	return;
	dw8250_force_idle(p);
	writel(value, p->membase + (UART_LCR << p->regshift));
	}
	dev_err(p->dev, "Couldn't set LCR to %d\n", value);
	}
	}

	static unsigned int dw8250_serial_in32(struct uart_port *p, int offset)
	{
	unsigned int value = readl(p->membase + (offset << p->regshift));

	return dw8250_modify_msr(p, offset, value);
	}

	static int dw8250_handle_irq(struct uart_port *p)
	{
	struct dw8250_data *d = p->private_data;
	unsigned int iir = p->serial_in(p, UART_IIR);

	if (serial8250_handle_irq(p, iir)) {
	return 1;
	} else if ((iir & UART_IIR_BUSY) == UART_IIR_BUSY) {
	/* Clear the USR */
	(void)p->serial_in(p, d->usr_reg);

	return 1;
	}

	return 0;
	}

	static void
	dw8250_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);
	}

	static bool dw8250_dma_filter(struct dma_chan chan, void param)
	{
	struct dw8250_data *data = param;

	return chan->chan_id == data->dma.tx_chan_id \|\|
	chan->chan_id == data->dma.rx_chan_id;
	}

	static void dw8250_setup_port(struct uart_8250_port *up)
	{
	struct uart_port *p = &up->port;
	u32 reg = readl(p->membase + DW_UART_UCV);

	/*
	* If the Component Version Register returns zero, we know that
	* ADDITIONAL_FEATURES are not enabled. No need to go any further.
	*/
	if (!reg)
	return;

	dev_dbg_ratelimited(p->dev, "Designware UART version %c.%c%c\n",
	(reg >> 24) & 0xff, (reg >> 16) & 0xff, (reg >> 8) & 0xff);

	reg = readl(p->membase + DW_UART_CPR);
	if (!reg)
	return;

	/* Select the type based on fifo */
	if (reg & DW_UART_CPR_FIFO_MODE) {
	p->type = PORT_16550A;
	p->flags \|= UPF_FIXED_TYPE;
	p->fifosize = DW_UART_CPR_FIFO_SIZE(reg);
	up->tx_loadsz = p->fifosize;
	up->capabilities = UART_CAP_FIFO;
	}

	if (reg & DW_UART_CPR_AFCE_MODE)
	up->capabilities \|= UART_CAP_AFE;
	}

	static int dw8250_probe_of(struct uart_port *p,
	struct dw8250_data *data)
	{
	struct device_node *np = p->dev->of_node;
	u32 val;
	bool has_ucv = true;

	if (of_device_is_compatible(np, "cavium,octeon-3860-uart")) {
	#ifdef __BIG_ENDIAN
	/*
	* Low order bits of these 64-bit registers, when
	* accessed as a byte, are 7 bytes further down in the
	* address space in big endian mode.
	*/
	p->membase += 7;
	#endif
	p->serial_out = dw8250_serial_out_rb;
	p->flags = ASYNC_SKIP_TEST \| UPF_SHARE_IRQ \| UPF_FIXED_TYPE;
	p->type = PORT_OCTEON;
	data->usr_reg = 0x27;
	has_ucv = false;
	} else if (!of_property_read_u32(np, "reg-io-width", &val)) {
	switch (val) {
	case 1:
	break;
	case 4:
	p->iotype = UPIO_MEM32;
	p->serial_in = dw8250_serial_in32;
	p->serial_out = dw8250_serial_out32;
	break;
	default:
	dev_err(p->dev, "unsupported reg-io-width (%u)\n", val);
	return -EINVAL;
	}
	}
	if (has_ucv)
	dw8250_setup_port(container_of(p, struct uart_8250_port, port));

	if (!of_property_read_u32(np, "reg-shift", &val))
	p->regshift = val;

	/* clock got configured through clk api, all done */
	if (p->uartclk)
	return 0;

	/* try to find out clock frequency from DT as fallback */
	if (of_property_read_u32(np, "clock-frequency", &val)) {
	dev_err(p->dev, "clk or clock-frequency not defined\n");
	return -EINVAL;
	}
	p->uartclk = val;

	return 0;
	}

	static int dw8250_probe_acpi(struct uart_8250_port *up,
	struct dw8250_data *data)
	{
	const struct acpi_device_id *id;
	struct uart_port *p = &up->port;

	dw8250_setup_port(up);

	id = acpi_match_device(p->dev->driver->acpi_match_table, p->dev);
	if (!id)
	return -ENODEV;

	p->iotype = UPIO_MEM32;
	p->serial_in = dw8250_serial_in32;
	p->serial_out = dw8250_serial_out32;
	p->regshift = 2;

	if (!p->uartclk)
	p->uartclk = (unsigned int)id->driver_data;

	up->dma = &data->dma;

	up->dma->rxconf.src_maxburst = p->fifosize / 4;
	up->dma->txconf.dst_maxburst = p->fifosize / 4;

	return 0;
	}

	static int dw8250_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 dw8250_data *data;
	int err;

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

	spin_lock_init(&uart.port.lock);
	uart.port.mapbase = regs->start;
	uart.port.irq = irq->start;
	uart.port.handle_irq = dw8250_handle_irq;
	uart.port.pm = dw8250_do_pm;
	uart.port.type = PORT_8250;
	uart.port.flags = UPF_SHARE_IRQ \| UPF_BOOT_AUTOCONF \| UPF_FIXED_PORT;
	uart.port.dev = &pdev->dev;

	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;

	data->usr_reg = DW_UART_USR;
	data->clk = devm_clk_get(&pdev->dev, NULL);
	if (!IS_ERR(data->clk)) {
	clk_prepare_enable(data->clk);
	uart.port.uartclk = clk_get_rate(data->clk);
	}

	data->dma.rx_chan_id = -1;
	data->dma.tx_chan_id = -1;
	data->dma.rx_param = data;
	data->dma.tx_param = data;
	data->dma.fn = dw8250_dma_filter;

	uart.port.iotype = UPIO_MEM;
	uart.port.serial_in = dw8250_serial_in;
	uart.port.serial_out = dw8250_serial_out;
	uart.port.private_data = data;

	if (pdev->dev.of_node) {
	err = dw8250_probe_of(&uart.port, data);
	if (err)
	return err;
	} else if (ACPI_HANDLE(&pdev->dev)) {
	err = dw8250_probe_acpi(&uart, data);
	if (err)
	return err;
	} else {
	return -ENODEV;
	}

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

	platform_set_drvdata(pdev, data);

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

	return 0;
	}

	static int dw8250_remove(struct platform_device *pdev)
	{
	struct dw8250_data *data = platform_get_drvdata(pdev);

	pm_runtime_get_sync(&pdev->dev);

	serial8250_unregister_port(data->line);

	if (!IS_ERR(data->clk))
	clk_disable_unprepare(data->clk);

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

	return 0;
	}

	#ifdef CONFIG_PM_SLEEP
	static int dw8250_suspend(struct device *dev)
	{
	struct dw8250_data *data = dev_get_drvdata(dev);

	serial8250_suspend_port(data->line);

	return 0;
	}

	static int dw8250_resume(struct device *dev)
	{
	struct dw8250_data *data = dev_get_drvdata(dev);

	serial8250_resume_port(data->line);

	return 0;
	}
	#endif /* CONFIG_PM_SLEEP */

	#ifdef CONFIG_PM_RUNTIME
	static int dw8250_runtime_suspend(struct device *dev)
	{
	struct dw8250_data *data = dev_get_drvdata(dev);

	if (!IS_ERR(data->clk))
	clk_disable_unprepare(data->clk);

	return 0;
	}

	static int dw8250_runtime_resume(struct device *dev)
	{
	struct dw8250_data *data = dev_get_drvdata(dev);

	if (!IS_ERR(data->clk))
	clk_prepare_enable(data->clk);

	return 0;
	}
	#endif

	static const struct dev_pm_ops dw8250_pm_ops = {
	SET_SYSTEM_SLEEP_PM_OPS(dw8250_suspend, dw8250_resume)
	SET_RUNTIME_PM_OPS(dw8250_runtime_suspend, dw8250_runtime_resume, NULL)
	};

	static const struct of_device_id dw8250_of_match[] = {
	{ .compatible = "snps,dw-apb-uart" },
	{ .compatible = "cavium,octeon-3860-uart" },
	{ /* Sentinel */ }
	};
	MODULE_DEVICE_TABLE(of, dw8250_of_match);

	static const struct acpi_device_id dw8250_acpi_match[] = {
	{ "INT33C4", 0 },
	{ "INT33C5", 0 },
	{ "INT3434", 0 },
	{ "INT3435", 0 },
	{ "80860F0A", 0 },
	{ },
	};
	MODULE_DEVICE_TABLE(acpi, dw8250_acpi_match);

	static struct platform_driver dw8250_platform_driver = {
	.driver = {
	.name = "dw-apb-uart",
	.owner = THIS_MODULE,
	.pm = &dw8250_pm_ops,
	.of_match_table = dw8250_of_match,
	.acpi_match_table = ACPI_PTR(dw8250_acpi_match),
	},
	.probe = dw8250_probe,
	.remove = dw8250_remove,
	};

	module_platform_driver(dw8250_platform_driver);

	MODULE_AUTHOR("Jamie Iles");
	MODULE_LICENSE("GPL");
	MODULE_DESCRIPTION("Synopsys DesignWare 8250 serial port driver");