drivers/tty/goldfish.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2007 Google, Inc.
  * Copyright (C) 2012 Intel, Inc.
  * Copyright (C) 2017 Imagination Technologies Ltd.
  */

 #include <linux/console.h>
 #include <linux/interrupt.h>
 #include <linux/platform_device.h>
 #include <linux/tty.h>
 #include <linux/tty_flip.h>
 #include <linux/slab.h>
 #include <linux/io.h>
 #include <linux/module.h>
 #include <linux/mod_devicetable.h>
 #include <linux/goldfish.h>
 #include <linux/mm.h>
 #include <linux/dma-mapping.h>
 #include <linux/serial_core.h>

 /* Goldfish tty register's offsets */
 #define	GOLDFISH_TTY_REG_BYTES_READY	0x04
 #define	GOLDFISH_TTY_REG_CMD		0x08
 #define	GOLDFISH_TTY_REG_DATA_PTR	0x10
 #define	GOLDFISH_TTY_REG_DATA_LEN	0x14
 #define	GOLDFISH_TTY_REG_DATA_PTR_HIGH	0x18
 #define	GOLDFISH_TTY_REG_VERSION	0x20

 /* Goldfish tty commands */
 #define	GOLDFISH_TTY_CMD_INT_DISABLE	0
 #define	GOLDFISH_TTY_CMD_INT_ENABLE	1
 #define	GOLDFISH_TTY_CMD_WRITE_BUFFER	2
 #define	GOLDFISH_TTY_CMD_READ_BUFFER	3

 struct goldfish_tty {
 	struct tty_port port;
 	spinlock_t lock;
 	void __iomem *base;
 	u32 irq;
 	int opencount;
 	struct console console;
 	u32 version;
 	struct device *dev;
 };

 static DEFINE_MUTEX(goldfish_tty_lock);
 static struct tty_driver *goldfish_tty_driver;
 static u32 goldfish_tty_line_count = 8;
 static u32 goldfish_tty_current_line_count;
 static struct goldfish_tty *goldfish_ttys;

 static void do_rw_io(struct goldfish_tty *qtty,
 		     unsigned long address,
 		     unsigned int count,
 		     int is_write)
 {
 	unsigned long irq_flags;
 	void __iomem *base = qtty->base;

 	spin_lock_irqsave(&qtty->lock, irq_flags);
 	gf_write_ptr((void *)address, base + GOLDFISH_TTY_REG_DATA_PTR,
 		     base + GOLDFISH_TTY_REG_DATA_PTR_HIGH);
 	gf_iowrite32(count, base + GOLDFISH_TTY_REG_DATA_LEN);

 	if (is_write)
 		gf_iowrite32(GOLDFISH_TTY_CMD_WRITE_BUFFER,
 		       base + GOLDFISH_TTY_REG_CMD);
 	else
 		gf_iowrite32(GOLDFISH_TTY_CMD_READ_BUFFER,
 		       base + GOLDFISH_TTY_REG_CMD);

 	spin_unlock_irqrestore(&qtty->lock, irq_flags);
 }

 static void goldfish_tty_rw(struct goldfish_tty *qtty,
 			    unsigned long addr,
 			    unsigned int count,
 			    int is_write)
 {
 	dma_addr_t dma_handle;
 	enum dma_data_direction dma_dir;

 	dma_dir = (is_write ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
 	if (qtty->version > 0) {
 		/*
 		 * Goldfish TTY for Ranchu platform uses
 		 * physical addresses and DMA for read/write operations
 		 */
 		unsigned long addr_end = addr + count;

 		while (addr < addr_end) {
 			unsigned long pg_end = (addr & PAGE_MASK) + PAGE_SIZE;
 			unsigned long next =
 					pg_end < addr_end ? pg_end : addr_end;
 			unsigned long avail = next - addr;

 			/*
 			 * Map the buffer's virtual address to the DMA address
 			 * so the buffer can be accessed by the device.
 			 */
 			dma_handle = dma_map_single(qtty->dev, (void *)addr,
 						    avail, dma_dir);

 			if (dma_mapping_error(qtty->dev, dma_handle)) {
 				dev_err(qtty->dev, "tty: DMA mapping error.\n");
 				return;
 			}
 			do_rw_io(qtty, dma_handle, avail, is_write);

 			/*
 			 * Unmap the previously mapped region after
 			 * the completion of the read/write operation.
 			 */
 			dma_unmap_single(qtty->dev, dma_handle, avail, dma_dir);

 			addr += avail;
 		}
 	} else {
 		/*
 		 * Old style Goldfish TTY used on the Goldfish platform
 		 * uses virtual addresses.
 		 */
 		do_rw_io(qtty, addr, count, is_write);
 	}
 }

 static void goldfish_tty_do_write(int line, const char *buf,
 				  unsigned int count)
 {
 	struct goldfish_tty *qtty = &goldfish_ttys[line];
 	unsigned long address = (unsigned long)(void *)buf;

 	goldfish_tty_rw(qtty, address, count, 1);
 }

 static irqreturn_t goldfish_tty_interrupt(int irq, void *dev_id)
 {
 	struct goldfish_tty *qtty = dev_id;
 	void __iomem *base = qtty->base;
 	unsigned long address;
 	unsigned char *buf;
 	u32 count;

 	count = gf_ioread32(base + GOLDFISH_TTY_REG_BYTES_READY);
 	if (count == 0)
 		return IRQ_NONE;

 	count = tty_prepare_flip_string(&qtty->port, &buf, count);

 	address = (unsigned long)(void *)buf;
 	goldfish_tty_rw(qtty, address, count, 0);

 	tty_flip_buffer_push(&qtty->port);
 	return IRQ_HANDLED;
 }

 static int goldfish_tty_activate(struct tty_port *port, struct tty_struct *tty)
 {
 	struct goldfish_tty *qtty = container_of(port, struct goldfish_tty,
 									port);
 	gf_iowrite32(GOLDFISH_TTY_CMD_INT_ENABLE, qtty->base + GOLDFISH_TTY_REG_CMD);
 	return 0;
 }

 static void goldfish_tty_shutdown(struct tty_port *port)
 {
 	struct goldfish_tty *qtty = container_of(port, struct goldfish_tty,
 									port);
 	gf_iowrite32(GOLDFISH_TTY_CMD_INT_DISABLE, qtty->base + GOLDFISH_TTY_REG_CMD);
 }

 static int goldfish_tty_open(struct tty_struct *tty, struct file *filp)
 {
 	struct goldfish_tty *qtty = &goldfish_ttys[tty->index];
 	return tty_port_open(&qtty->port, tty, filp);
 }

 static void goldfish_tty_close(struct tty_struct *tty, struct file *filp)
 {
 	tty_port_close(tty->port, tty, filp);
 }

 static void goldfish_tty_hangup(struct tty_struct *tty)
 {
 	tty_port_hangup(tty->port);
 }

 static int goldfish_tty_write(struct tty_struct *tty, const unsigned char *buf,
 								int count)
 {
 	goldfish_tty_do_write(tty->index, buf, count);
 	return count;
 }

 static unsigned int goldfish_tty_write_room(struct tty_struct *tty)
 {
 	return 0x10000;
 }

 static unsigned int goldfish_tty_chars_in_buffer(struct tty_struct *tty)
 {
 	struct goldfish_tty *qtty = &goldfish_ttys[tty->index];
 	void __iomem *base = qtty->base;
 	return gf_ioread32(base + GOLDFISH_TTY_REG_BYTES_READY);
 }

 static void goldfish_tty_console_write(struct console *co, const char *b,
 								unsigned count)
 {
 	goldfish_tty_do_write(co->index, b, count);
 }

 static struct tty_driver *goldfish_tty_console_device(struct console *c,
 								int *index)
 {
 	*index = c->index;
 	return goldfish_tty_driver;
 }

 static int goldfish_tty_console_setup(struct console *co, char *options)
 {
 	if ((unsigned)co->index >= goldfish_tty_line_count)
 		return -ENODEV;
 	if (!goldfish_ttys[co->index].base)
 		return -ENODEV;
 	return 0;
 }

 static const struct tty_port_operations goldfish_port_ops = {
 	.activate = goldfish_tty_activate,
 	.shutdown = goldfish_tty_shutdown
 };

 static const struct tty_operations goldfish_tty_ops = {
 	.open = goldfish_tty_open,
 	.close = goldfish_tty_close,
 	.hangup = goldfish_tty_hangup,
 	.write = goldfish_tty_write,
 	.write_room = goldfish_tty_write_room,
 	.chars_in_buffer = goldfish_tty_chars_in_buffer,
 };

 static int goldfish_tty_create_driver(void)
 {
 	int ret;
 	struct tty_driver *tty;

 	goldfish_ttys = kcalloc(goldfish_tty_line_count,
 				sizeof(*goldfish_ttys),
 				GFP_KERNEL);
 	if (goldfish_ttys == NULL) {
 		ret = -ENOMEM;
 		goto err_alloc_goldfish_ttys_failed;
 	}
 	tty = tty_alloc_driver(goldfish_tty_line_count,
 			TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
 			TTY_DRIVER_DYNAMIC_DEV);
 	if (IS_ERR(tty)) {
 		ret = PTR_ERR(tty);
 		goto err_tty_alloc_driver_failed;
 	}
 	tty->driver_name = "goldfish";
 	tty->name = "ttyGF";
 	tty->type = TTY_DRIVER_TYPE_SERIAL;
 	tty->subtype = SERIAL_TYPE_NORMAL;
 	tty->init_termios = tty_std_termios;
 	tty_set_operations(tty, &goldfish_tty_ops);
 	ret = tty_register_driver(tty);
 	if (ret)
 		goto err_tty_register_driver_failed;

 	goldfish_tty_driver = tty;
 	return 0;

 err_tty_register_driver_failed:
 	tty_driver_kref_put(tty);
 err_tty_alloc_driver_failed:
 	kfree(goldfish_ttys);
 	goldfish_ttys = NULL;
 err_alloc_goldfish_ttys_failed:
 	return ret;
 }

 static void goldfish_tty_delete_driver(void)
 {
 	tty_unregister_driver(goldfish_tty_driver);
 	tty_driver_kref_put(goldfish_tty_driver);
 	goldfish_tty_driver = NULL;
 	kfree(goldfish_ttys);
 	goldfish_ttys = NULL;
 }

 static int goldfish_tty_probe(struct platform_device *pdev)
 {
 	struct goldfish_tty *qtty;
 	int ret = -ENODEV;
 	struct resource *r;
 	struct device *ttydev;
 	void __iomem *base;
 	int irq;
 	unsigned int line;

 	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	if (!r) {
 		pr_err("goldfish_tty: No MEM resource available!\n");
 		return -ENOMEM;
 	}

 	base = ioremap(r->start, 0x1000);
 	if (!base) {
 		pr_err("goldfish_tty: Unable to ioremap base!\n");
 		return -ENOMEM;
 	}

 	irq = platform_get_irq(pdev, 0);
 	if (irq < 0) {
 		ret = irq;
 		goto err_unmap;
 	}

 	mutex_lock(&goldfish_tty_lock);

 	if (pdev->id == PLATFORM_DEVID_NONE)
 		line = goldfish_tty_current_line_count;
 	else
 		line = pdev->id;

 	if (line >= goldfish_tty_line_count) {
 		pr_err("goldfish_tty: Reached maximum tty number of %d.\n",
 		       goldfish_tty_current_line_count);
 		ret = -ENOMEM;
 		goto err_unlock;
 	}

 	if (goldfish_tty_current_line_count == 0) {
 		ret = goldfish_tty_create_driver();
 		if (ret)
 			goto err_unlock;
 	}
 	goldfish_tty_current_line_count++;

 	qtty = &goldfish_ttys[line];
 	spin_lock_init(&qtty->lock);
 	tty_port_init(&qtty->port);
 	qtty->port.ops = &goldfish_port_ops;
 	qtty->base = base;
 	qtty->irq = irq;
 	qtty->dev = &pdev->dev;

 	/*
 	 * Goldfish TTY device used by the Goldfish emulator
 	 * should identify itself with 0, forcing the driver
 	 * to use virtual addresses. Goldfish TTY device
 	 * on Ranchu emulator (qemu2) returns 1 here and
 	 * driver will use physical addresses.
 	 */
 	qtty->version = gf_ioread32(base + GOLDFISH_TTY_REG_VERSION);

 	/*
 	 * Goldfish TTY device on Ranchu emulator (qemu2)
 	 * will use DMA for read/write IO operations.
 	 */
 	if (qtty->version > 0) {
 		/*
 		 * Initialize dma_mask to 32-bits.
 		 */
 		if (!pdev->dev.dma_mask)
 			pdev->dev.dma_mask = &pdev->dev.coherent_dma_mask;
 		ret = dma_set_mask(&pdev->dev, DMA_BIT_MASK(32));
 		if (ret) {
 			dev_err(&pdev->dev, "No suitable DMA available.\n");
 			goto err_dec_line_count;
 		}
 	}

 	gf_iowrite32(GOLDFISH_TTY_CMD_INT_DISABLE, base + GOLDFISH_TTY_REG_CMD);

 	ret = request_irq(irq, goldfish_tty_interrupt, IRQF_SHARED,
 			  "goldfish_tty", qtty);
 	if (ret) {
 		pr_err("goldfish_tty: No IRQ available!\n");
 		goto err_dec_line_count;
 	}

 	ttydev = tty_port_register_device(&qtty->port, goldfish_tty_driver,
 					  line, &pdev->dev);
 	if (IS_ERR(ttydev)) {
 		ret = PTR_ERR(ttydev);
 		goto err_tty_register_device_failed;
 	}

 	strcpy(qtty->console.name, "ttyGF");
 	qtty->console.write = goldfish_tty_console_write;
 	qtty->console.device = goldfish_tty_console_device;
 	qtty->console.setup = goldfish_tty_console_setup;
 	qtty->console.flags = CON_PRINTBUFFER;
 	qtty->console.index = line;
 	register_console(&qtty->console);
 	platform_set_drvdata(pdev, qtty);

 	mutex_unlock(&goldfish_tty_lock);
 	return 0;

 err_tty_register_device_failed:
 	free_irq(irq, qtty);
 err_dec_line_count:
 	tty_port_destroy(&qtty->port);
 	goldfish_tty_current_line_count--;
 	if (goldfish_tty_current_line_count == 0)
 		goldfish_tty_delete_driver();
 err_unlock:
 	mutex_unlock(&goldfish_tty_lock);
 err_unmap:
 	iounmap(base);
 	return ret;
 }

 static int goldfish_tty_remove(struct platform_device *pdev)
 {
 	struct goldfish_tty *qtty = platform_get_drvdata(pdev);

 	mutex_lock(&goldfish_tty_lock);

 	unregister_console(&qtty->console);
 	tty_unregister_device(goldfish_tty_driver, qtty->console.index);
 	iounmap(qtty->base);
 	qtty->base = NULL;
 	free_irq(qtty->irq, qtty);
 	tty_port_destroy(&qtty->port);
 	goldfish_tty_current_line_count--;
 	if (goldfish_tty_current_line_count == 0)
 		goldfish_tty_delete_driver();
 	mutex_unlock(&goldfish_tty_lock);
 	return 0;
 }

 #ifdef CONFIG_GOLDFISH_TTY_EARLY_CONSOLE
 static void gf_early_console_putchar(struct uart_port *port, unsigned char ch)
 {
 	gf_iowrite32(ch, port->membase);
 }

 static void gf_early_write(struct console *con, const char *s, unsigned int n)
 {
 	struct earlycon_device *dev = con->data;

 	uart_console_write(&dev->port, s, n, gf_early_console_putchar);
 }

 static int __init gf_earlycon_setup(struct earlycon_device *device,
 				    const char *opt)
 {
 	if (!device->port.membase)
 		return -ENODEV;

 	device->con->write = gf_early_write;
 	return 0;
 }

 OF_EARLYCON_DECLARE(early_gf_tty, "google,goldfish-tty", gf_earlycon_setup);
 #endif

 static const struct of_device_id goldfish_tty_of_match[] = {
 	{ .compatible = "google,goldfish-tty", },
 	{},
 };

 MODULE_DEVICE_TABLE(of, goldfish_tty_of_match);

 static struct platform_driver goldfish_tty_platform_driver = {
 	.probe = goldfish_tty_probe,
 	.remove = goldfish_tty_remove,
 	.driver = {
 		.name = "goldfish_tty",
 		.of_match_table = goldfish_tty_of_match,
 	}
 };

 module_platform_driver(goldfish_tty_platform_driver);

 MODULE_LICENSE("GPL v2");
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Copyright (C) 2007 Google, Inc.
	* Copyright (C) 2012 Intel, Inc.
	* Copyright (C) 2017 Imagination Technologies Ltd.
	*/

	#include <linux/console.h>
	#include <linux/interrupt.h>
	#include <linux/platform_device.h>
	#include <linux/tty.h>
	#include <linux/tty_flip.h>
	#include <linux/slab.h>
	#include <linux/io.h>
	#include <linux/module.h>
	#include <linux/mod_devicetable.h>
	#include <linux/goldfish.h>
	#include <linux/mm.h>
	#include <linux/dma-mapping.h>
	#include <linux/serial_core.h>

	/* Goldfish tty register's offsets */
	#define GOLDFISH_TTY_REG_BYTES_READY 0x04
	#define GOLDFISH_TTY_REG_CMD 0x08
	#define GOLDFISH_TTY_REG_DATA_PTR 0x10
	#define GOLDFISH_TTY_REG_DATA_LEN 0x14
	#define GOLDFISH_TTY_REG_DATA_PTR_HIGH 0x18
	#define GOLDFISH_TTY_REG_VERSION 0x20

	/* Goldfish tty commands */
	#define GOLDFISH_TTY_CMD_INT_DISABLE 0
	#define GOLDFISH_TTY_CMD_INT_ENABLE 1
	#define GOLDFISH_TTY_CMD_WRITE_BUFFER 2
	#define GOLDFISH_TTY_CMD_READ_BUFFER 3

	struct goldfish_tty {
	struct tty_port port;
	spinlock_t lock;
	void __iomem *base;
	u32 irq;
	int opencount;
	struct console console;
	u32 version;
	struct device *dev;
	};

	static DEFINE_MUTEX(goldfish_tty_lock);
	static struct tty_driver *goldfish_tty_driver;
	static u32 goldfish_tty_line_count = 8;
	static u32 goldfish_tty_current_line_count;
	static struct goldfish_tty *goldfish_ttys;

	static void do_rw_io(struct goldfish_tty *qtty,
	unsigned long address,
	unsigned int count,
	int is_write)
	{
	unsigned long irq_flags;
	void __iomem *base = qtty->base;

	spin_lock_irqsave(&qtty->lock, irq_flags);
	gf_write_ptr((void *)address, base + GOLDFISH_TTY_REG_DATA_PTR,
	base + GOLDFISH_TTY_REG_DATA_PTR_HIGH);
	gf_iowrite32(count, base + GOLDFISH_TTY_REG_DATA_LEN);

	if (is_write)
	gf_iowrite32(GOLDFISH_TTY_CMD_WRITE_BUFFER,
	base + GOLDFISH_TTY_REG_CMD);
	else
	gf_iowrite32(GOLDFISH_TTY_CMD_READ_BUFFER,
	base + GOLDFISH_TTY_REG_CMD);

	spin_unlock_irqrestore(&qtty->lock, irq_flags);
	}

	static void goldfish_tty_rw(struct goldfish_tty *qtty,
	unsigned long addr,
	unsigned int count,
	int is_write)
	{
	dma_addr_t dma_handle;
	enum dma_data_direction dma_dir;

	dma_dir = (is_write ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
	if (qtty->version > 0) {
	/*
	* Goldfish TTY for Ranchu platform uses
	* physical addresses and DMA for read/write operations
	*/
	unsigned long addr_end = addr + count;

	while (addr < addr_end) {
	unsigned long pg_end = (addr & PAGE_MASK) + PAGE_SIZE;
	unsigned long next =
	pg_end < addr_end ? pg_end : addr_end;
	unsigned long avail = next - addr;

	/*
	* Map the buffer's virtual address to the DMA address
	* so the buffer can be accessed by the device.
	*/
	dma_handle = dma_map_single(qtty->dev, (void *)addr,
	avail, dma_dir);

	if (dma_mapping_error(qtty->dev, dma_handle)) {
	dev_err(qtty->dev, "tty: DMA mapping error.\n");
	return;
	}
	do_rw_io(qtty, dma_handle, avail, is_write);

	/*
	* Unmap the previously mapped region after
	* the completion of the read/write operation.
	*/
	dma_unmap_single(qtty->dev, dma_handle, avail, dma_dir);

	addr += avail;
	}
	} else {
	/*
	* Old style Goldfish TTY used on the Goldfish platform
	* uses virtual addresses.
	*/
	do_rw_io(qtty, addr, count, is_write);
	}
	}

	static void goldfish_tty_do_write(int line, const char *buf,
	unsigned int count)
	{
	struct goldfish_tty *qtty = &goldfish_ttys[line];
	unsigned long address = (unsigned long)(void *)buf;

	goldfish_tty_rw(qtty, address, count, 1);
	}

	static irqreturn_t goldfish_tty_interrupt(int irq, void *dev_id)
	{
	struct goldfish_tty *qtty = dev_id;
	void __iomem *base = qtty->base;
	unsigned long address;
	unsigned char *buf;
	u32 count;

	count = gf_ioread32(base + GOLDFISH_TTY_REG_BYTES_READY);
	if (count == 0)
	return IRQ_NONE;

	count = tty_prepare_flip_string(&qtty->port, &buf, count);

	address = (unsigned long)(void *)buf;
	goldfish_tty_rw(qtty, address, count, 0);

	tty_flip_buffer_push(&qtty->port);
	return IRQ_HANDLED;
	}

	static int goldfish_tty_activate(struct tty_port port, struct tty_struct tty)
	{
	struct goldfish_tty *qtty = container_of(port, struct goldfish_tty,
	port);
	gf_iowrite32(GOLDFISH_TTY_CMD_INT_ENABLE, qtty->base + GOLDFISH_TTY_REG_CMD);
	return 0;
	}

	static void goldfish_tty_shutdown(struct tty_port *port)
	{
	struct goldfish_tty *qtty = container_of(port, struct goldfish_tty,
	port);
	gf_iowrite32(GOLDFISH_TTY_CMD_INT_DISABLE, qtty->base + GOLDFISH_TTY_REG_CMD);
	}

	static int goldfish_tty_open(struct tty_struct tty, struct file filp)
	{
	struct goldfish_tty *qtty = &goldfish_ttys[tty->index];
	return tty_port_open(&qtty->port, tty, filp);
	}

	static void goldfish_tty_close(struct tty_struct tty, struct file filp)
	{
	tty_port_close(tty->port, tty, filp);
	}

	static void goldfish_tty_hangup(struct tty_struct *tty)
	{
	tty_port_hangup(tty->port);
	}

	static int goldfish_tty_write(struct tty_struct tty, const unsigned char buf,
	int count)
	{
	goldfish_tty_do_write(tty->index, buf, count);
	return count;
	}

	static unsigned int goldfish_tty_write_room(struct tty_struct *tty)
	{
	return 0x10000;
	}

	static unsigned int goldfish_tty_chars_in_buffer(struct tty_struct *tty)
	{
	struct goldfish_tty *qtty = &goldfish_ttys[tty->index];
	void __iomem *base = qtty->base;
	return gf_ioread32(base + GOLDFISH_TTY_REG_BYTES_READY);
	}

	static void goldfish_tty_console_write(struct console co, const char b,
	unsigned count)
	{
	goldfish_tty_do_write(co->index, b, count);
	}

	static struct tty_driver goldfish_tty_console_device(struct console c,
	int *index)
	{
	*index = c->index;
	return goldfish_tty_driver;
	}

	static int goldfish_tty_console_setup(struct console co, char options)
	{
	if ((unsigned)co->index >= goldfish_tty_line_count)
	return -ENODEV;
	if (!goldfish_ttys[co->index].base)
	return -ENODEV;
	return 0;
	}

	static const struct tty_port_operations goldfish_port_ops = {
	.activate = goldfish_tty_activate,
	.shutdown = goldfish_tty_shutdown
	};

	static const struct tty_operations goldfish_tty_ops = {
	.open = goldfish_tty_open,
	.close = goldfish_tty_close,
	.hangup = goldfish_tty_hangup,
	.write = goldfish_tty_write,
	.write_room = goldfish_tty_write_room,
	.chars_in_buffer = goldfish_tty_chars_in_buffer,
	};

	static int goldfish_tty_create_driver(void)
	{
	int ret;
	struct tty_driver *tty;

	goldfish_ttys = kcalloc(goldfish_tty_line_count,
	sizeof(*goldfish_ttys),
	GFP_KERNEL);
	if (goldfish_ttys == NULL) {
	ret = -ENOMEM;
	goto err_alloc_goldfish_ttys_failed;
	}
	tty = tty_alloc_driver(goldfish_tty_line_count,
	TTY_DRIVER_RESET_TERMIOS \| TTY_DRIVER_REAL_RAW \|
	TTY_DRIVER_DYNAMIC_DEV);
	if (IS_ERR(tty)) {
	ret = PTR_ERR(tty);
	goto err_tty_alloc_driver_failed;
	}
	tty->driver_name = "goldfish";
	tty->name = "ttyGF";
	tty->type = TTY_DRIVER_TYPE_SERIAL;
	tty->subtype = SERIAL_TYPE_NORMAL;
	tty->init_termios = tty_std_termios;
	tty_set_operations(tty, &goldfish_tty_ops);
	ret = tty_register_driver(tty);
	if (ret)
	goto err_tty_register_driver_failed;

	goldfish_tty_driver = tty;
	return 0;

	err_tty_register_driver_failed:
	tty_driver_kref_put(tty);
	err_tty_alloc_driver_failed:
	kfree(goldfish_ttys);
	goldfish_ttys = NULL;
	err_alloc_goldfish_ttys_failed:
	return ret;
	}

	static void goldfish_tty_delete_driver(void)
	{
	tty_unregister_driver(goldfish_tty_driver);
	tty_driver_kref_put(goldfish_tty_driver);
	goldfish_tty_driver = NULL;
	kfree(goldfish_ttys);
	goldfish_ttys = NULL;
	}

	static int goldfish_tty_probe(struct platform_device *pdev)
	{
	struct goldfish_tty *qtty;
	int ret = -ENODEV;
	struct resource *r;
	struct device *ttydev;
	void __iomem *base;
	int irq;
	unsigned int line;

	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!r) {
	pr_err("goldfish_tty: No MEM resource available!\n");
	return -ENOMEM;
	}

	base = ioremap(r->start, 0x1000);
	if (!base) {
	pr_err("goldfish_tty: Unable to ioremap base!\n");
	return -ENOMEM;
	}

	irq = platform_get_irq(pdev, 0);
	if (irq < 0) {
	ret = irq;
	goto err_unmap;
	}

	mutex_lock(&goldfish_tty_lock);

	if (pdev->id == PLATFORM_DEVID_NONE)
	line = goldfish_tty_current_line_count;
	else
	line = pdev->id;

	if (line >= goldfish_tty_line_count) {
	pr_err("goldfish_tty: Reached maximum tty number of %d.\n",
	goldfish_tty_current_line_count);
	ret = -ENOMEM;
	goto err_unlock;
	}

	if (goldfish_tty_current_line_count == 0) {
	ret = goldfish_tty_create_driver();
	if (ret)
	goto err_unlock;
	}
	goldfish_tty_current_line_count++;

	qtty = &goldfish_ttys[line];
	spin_lock_init(&qtty->lock);
	tty_port_init(&qtty->port);
	qtty->port.ops = &goldfish_port_ops;
	qtty->base = base;
	qtty->irq = irq;
	qtty->dev = &pdev->dev;

	/*
	* Goldfish TTY device used by the Goldfish emulator
	* should identify itself with 0, forcing the driver
	* to use virtual addresses. Goldfish TTY device
	* on Ranchu emulator (qemu2) returns 1 here and
	* driver will use physical addresses.
	*/
	qtty->version = gf_ioread32(base + GOLDFISH_TTY_REG_VERSION);

	/*
	* Goldfish TTY device on Ranchu emulator (qemu2)
	* will use DMA for read/write IO operations.
	*/
	if (qtty->version > 0) {
	/*
	* Initialize dma_mask to 32-bits.
	*/
	if (!pdev->dev.dma_mask)
	pdev->dev.dma_mask = &pdev->dev.coherent_dma_mask;
	ret = dma_set_mask(&pdev->dev, DMA_BIT_MASK(32));
	if (ret) {
	dev_err(&pdev->dev, "No suitable DMA available.\n");
	goto err_dec_line_count;
	}
	}

	gf_iowrite32(GOLDFISH_TTY_CMD_INT_DISABLE, base + GOLDFISH_TTY_REG_CMD);

	ret = request_irq(irq, goldfish_tty_interrupt, IRQF_SHARED,
	"goldfish_tty", qtty);
	if (ret) {
	pr_err("goldfish_tty: No IRQ available!\n");
	goto err_dec_line_count;
	}

	ttydev = tty_port_register_device(&qtty->port, goldfish_tty_driver,
	line, &pdev->dev);
	if (IS_ERR(ttydev)) {
	ret = PTR_ERR(ttydev);
	goto err_tty_register_device_failed;
	}

	strcpy(qtty->console.name, "ttyGF");
	qtty->console.write = goldfish_tty_console_write;
	qtty->console.device = goldfish_tty_console_device;
	qtty->console.setup = goldfish_tty_console_setup;
	qtty->console.flags = CON_PRINTBUFFER;
	qtty->console.index = line;
	register_console(&qtty->console);
	platform_set_drvdata(pdev, qtty);

	mutex_unlock(&goldfish_tty_lock);
	return 0;

	err_tty_register_device_failed:
	free_irq(irq, qtty);
	err_dec_line_count:
	tty_port_destroy(&qtty->port);
	goldfish_tty_current_line_count--;
	if (goldfish_tty_current_line_count == 0)
	goldfish_tty_delete_driver();
	err_unlock:
	mutex_unlock(&goldfish_tty_lock);
	err_unmap:
	iounmap(base);
	return ret;
	}

	static int goldfish_tty_remove(struct platform_device *pdev)
	{
	struct goldfish_tty *qtty = platform_get_drvdata(pdev);

	mutex_lock(&goldfish_tty_lock);

	unregister_console(&qtty->console);
	tty_unregister_device(goldfish_tty_driver, qtty->console.index);
	iounmap(qtty->base);
	qtty->base = NULL;
	free_irq(qtty->irq, qtty);
	tty_port_destroy(&qtty->port);
	goldfish_tty_current_line_count--;
	if (goldfish_tty_current_line_count == 0)
	goldfish_tty_delete_driver();
	mutex_unlock(&goldfish_tty_lock);
	return 0;
	}

	#ifdef CONFIG_GOLDFISH_TTY_EARLY_CONSOLE
	static void gf_early_console_putchar(struct uart_port *port, unsigned char ch)
	{
	gf_iowrite32(ch, port->membase);
	}

	static void gf_early_write(struct console con, const char s, unsigned int n)
	{
	struct earlycon_device *dev = con->data;

	uart_console_write(&dev->port, s, n, gf_early_console_putchar);
	}

	static int __init gf_earlycon_setup(struct earlycon_device *device,
	const char *opt)
	{
	if (!device->port.membase)
	return -ENODEV;

	device->con->write = gf_early_write;
	return 0;
	}

	OF_EARLYCON_DECLARE(early_gf_tty, "google,goldfish-tty", gf_earlycon_setup);
	#endif

	static const struct of_device_id goldfish_tty_of_match[] = {
	{ .compatible = "google,goldfish-tty", },
	{},
	};

	MODULE_DEVICE_TABLE(of, goldfish_tty_of_match);

	static struct platform_driver goldfish_tty_platform_driver = {
	.probe = goldfish_tty_probe,
	.remove = goldfish_tty_remove,
	.driver = {
	.name = "goldfish_tty",
	.of_match_table = goldfish_tty_of_match,
	}
	};

	module_platform_driver(goldfish_tty_platform_driver);

	MODULE_LICENSE("GPL v2");