tty: add a DesignWare 8250 driver

* Synopsys DesignWare ABP UART

Required properties:

- compatible : "snps,dw-apb-uart"

- reg : offset and length of the register set for the device.

- interrupts : should contain uart interrupt.

- clock-frequency : the input clock frequency for the UART.

Optional properties:

- reg-shift : quantity to shift the register offsets by.  If this property is

  not present then the register offsets are not shifted.

- reg-io-width : the size (in bytes) of the IO accesses that should be

  performed on the device.  If this property is not present then single byte

  accesses are used.

Example:

	uart@80230000 {

		compatible = "snps,dw-apb-uart";

		reg = <0x80230000 0x100>;

		clock-frequency = <3686400>;

		interrupts = <10>;

		reg-shift = <2>;

		reg-io-width = <4>;

	};

/*

 * Synopsys DesignWare 8250 driver.

 *

 * Copyright 2011 Picochip, Jamie Iles.

 *

 * 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/init.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>

struct dw8250_data {

	int	last_lcr;

	int	line;

};

static void dw8250_serial_out(struct uart_port *p, int offset, int value)

{

	struct dw8250_data *d = p->private_data;

	if (offset == UART_LCR)

		d->last_lcr = value;

	offset <<= p->regshift;

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

}

static unsigned int dw8250_serial_in(struct uart_port *p, int offset)

{

	offset <<= p->regshift;

	return readb(p->membase + offset);

}

static void dw8250_serial_out32(struct uart_port *p, int offset, int value)

{

	struct dw8250_data *d = p->private_data;

	if (offset == UART_LCR)

		d->last_lcr = value;

	offset <<= p->regshift;

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

}

static unsigned int dw8250_serial_in32(struct uart_port *p, int offset)

{

	offset <<= p->regshift;

	return readl(p->membase + offset);

}

/* Offset for the DesignWare's UART Status Register. */

#define UART_USR	0x1f

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 and write the LCR again. */

		(void)p->serial_in(p, UART_USR);

		p->serial_out(p, d->last_lcr, UART_LCR);

		return 1;

	}

	return 0;

}

static int __devinit dw8250_probe(struct platform_device *pdev)

{

	struct uart_port port = {};

	struct resource *regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);

	struct resource *irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);

	struct device_node *np = pdev->dev.of_node;

	u32 val;

	struct dw8250_data *data;

	if (!regs || !irq) {

		dev_err(&pdev->dev, "no registers/irq defined\n");

		return -EINVAL;

	}

	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);

	if (!data)

		return -ENOMEM;

	port.private_data = data;

	spin_lock_init(&port.lock);

	port.mapbase = regs->start;

	port.irq = irq->start;

	port.handle_irq = dw8250_handle_irq;

	port.type = PORT_8250;

	port.flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF | UPF_IOREMAP |

		UPF_FIXED_PORT | UPF_FIXED_TYPE;

	port.dev = &pdev->dev;

	port.iotype = UPIO_MEM;

	port.serial_in = dw8250_serial_in;

	port.serial_out = dw8250_serial_out;

	if (!of_property_read_u32(np, "reg-io-width", &val)) {

		switch (val) {

		case 1:

			break;

		case 4:

			port.iotype = UPIO_MEM32;

			port.serial_in = dw8250_serial_in32;

			port.serial_out = dw8250_serial_out32;

			break;

		default:

			dev_err(&pdev->dev, "unsupported reg-io-width (%u)\n",

				val);

			return -EINVAL;

		}

	}

	if (!of_property_read_u32(np, "reg-shift", &val))

		port.regshift = val;

	if (of_property_read_u32(np, "clock-frequency", &val)) {

		dev_err(&pdev->dev, "no clock-frequency property set\n");

		return -EINVAL;

	}

	port.uartclk = val;

	data->line = serial8250_register_port(&port);

	if (data->line < 0)

		return data->line;

	platform_set_drvdata(pdev, data);

	return 0;

}

static int __devexit dw8250_remove(struct platform_device *pdev)

{

	struct dw8250_data *data = platform_get_drvdata(pdev);

	serial8250_unregister_port(data->line);

	return 0;

}

static const struct of_device_id dw8250_match[] = {

	{ .compatible = "snps,dw-apb-uart" },

	{ /* Sentinel */ }

};

MODULE_DEVICE_TABLE(of, dw8250_match);

static struct platform_driver dw8250_platform_driver = {

	.driver = {

		.name		= "dw-apb-uart",

		.owner		= THIS_MODULE,

		.of_match_table	= dw8250_match,

	},

	.probe			= dw8250_probe,

	.remove			= __devexit_p(dw8250_remove),

};

static int __init dw8250_init(void)

{

	return platform_driver_register(&dw8250_platform_driver);

}

module_init(dw8250_init);

static void __exit dw8250_exit(void)

{

	platform_driver_unregister(&dw8250_platform_driver);

}

module_exit(dw8250_exit);

MODULE_AUTHOR("Jamie Iles");

MODULE_LICENSE("GPL");

MODULE_DESCRIPTION("Synopsys DesignWare 8250 serial port driver");

	  port hardware found on MIPS RM9122 and similar processors.

	  If unsure, say N.

config SERIAL_8250_DW

	tristate "Support for Synopsys DesignWare 8250 quirks"

	depends on SERIAL_8250 && OF

	help

	  Selecting this option will enable handling of the extra features

	  present in the Synopsys DesignWare APB UART.

comment "Non-8250 serial port support"

config SERIAL_AMBA_PL010

obj-$(CONFIG_SERIAL_8250_EXAR_ST16C554) += 8250_exar_st16c554.o

obj-$(CONFIG_SERIAL_8250_HUB6) += 8250_hub6.o

obj-$(CONFIG_SERIAL_8250_MCA) += 8250_mca.o

obj-$(CONFIG_SERIAL_8250_DW) += 8250_dw.o

obj-$(CONFIG_SERIAL_AMBA_PL010) += amba-pl010.o

obj-$(CONFIG_SERIAL_AMBA_PL011) += amba-pl011.o

obj-$(CONFIG_SERIAL_CLPS711X) += clps711x.o