/*
 * Xilinx gpio driver
 *
 * Copyright 2008 Xilinx, Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/init.h>
#include <linux/errno.h>
#include <linux/of_device.h>
#include <linux/of_platform.h>
#include <linux/of_gpio.h>
#include <linux/io.h>
#include <linux/gpio.h>
#include <linux/slab.h>

/* Register Offset Definitions */
#define XGPIO_DATA_OFFSET   (0x0)	/* Data register  */
#define XGPIO_TRI_OFFSET    (0x4)	/* I/O direction register  */

struct xgpio_instance {
	struct of_mm_gpio_chip mmchip;
	u32 gpio_state;		/* GPIO state shadow register */
	u32 gpio_dir;		/* GPIO direction shadow register */
	spinlock_t gpio_lock;	/* Lock used for synchronization */
};

/**
 * xgpio_get - Read the specified signal of the GPIO device.
 * @gc:     Pointer to gpio_chip device structure.
 * @gpio:   GPIO signal number.
 *
 * This function reads the specified signal of the GPIO device. It returns 0 if
 * the signal clear, 1 if signal is set or negative value on error.
 */
static int xgpio_get(struct gpio_chip *gc, unsigned int gpio)
{
	struct of_mm_gpio_chip *mm_gc = to_of_mm_gpio_chip(gc);

	return (in_be32(mm_gc->regs + XGPIO_DATA_OFFSET) >> gpio) & 1;
}

/**
 * xgpio_set - Write the specified signal of the GPIO device.
 * @gc:     Pointer to gpio_chip device structure.
 * @gpio:   GPIO signal number.
 * @val:    Value to be written to specified signal.
 *
 * This function writes the specified value in to the specified signal of the
 * GPIO device.
 */
static void xgpio_set(struct gpio_chip *gc, unsigned int gpio, int val)
{
	unsigned long flags;
	struct of_mm_gpio_chip *mm_gc = to_of_mm_gpio_chip(gc);
	struct xgpio_instance *chip =
	    container_of(mm_gc, struct xgpio_instance, mmchip);

	spin_lock_irqsave(&chip->gpio_lock, flags);

	/* Write to GPIO signal and set its direction to output */
	if (val)
		chip->gpio_state |= 1 << gpio;
	else
		chip->gpio_state &= ~(1 << gpio);
	out_be32(mm_gc->regs + XGPIO_DATA_OFFSET, chip->gpio_state);

	spin_unlock_irqrestore(&chip->gpio_lock, flags);
}

/**
 * xgpio_dir_in - Set the direction of the specified GPIO signal as input.
 * @gc:     Pointer to gpio_chip device structure.
 * @gpio:   GPIO signal number.
 *
 * This function sets the direction of specified GPIO signal as input.
 * It returns 0 if direction of GPIO signals is set as input otherwise it
 * returns negative error value.
 */
static int xgpio_dir_in(struct gpio_chip *gc, unsigned int gpio)
{
	unsigned long flags;
	struct of_mm_gpio_chip *mm_gc = to_of_mm_gpio_chip(gc);
	struct xgpio_instance *chip =
	    container_of(mm_gc, struct xgpio_instance, mmchip);

	spin_lock_irqsave(&chip->gpio_lock, flags);

	/* Set the GPIO bit in shadow register and set direction as input */
	chip->gpio_dir |= (1 << gpio);
	out_be32(mm_gc->regs + XGPIO_TRI_OFFSET, chip->gpio_dir);

	spin_unlock_irqrestore(&chip->gpio_lock, flags);

	return 0;
}

/**
 * xgpio_dir_out - Set the direction of the specified GPIO signal as output.
 * @gc:     Pointer to gpio_chip device structure.
 * @gpio:   GPIO signal number.
 * @val:    Value to be written to specified signal.
 *
 * This function sets the direction of specified GPIO signal as output. If all
 * GPIO signals of GPIO chip is configured as input then it returns
 * error otherwise it returns 0.
 */
static int xgpio_dir_out(struct gpio_chip *gc, unsigned int gpio, int val)
{
	unsigned long flags;
	struct of_mm_gpio_chip *mm_gc = to_of_mm_gpio_chip(gc);
	struct xgpio_instance *chip =
	    container_of(mm_gc, struct xgpio_instance, mmchip);

	spin_lock_irqsave(&chip->gpio_lock, flags);

	/* Write state of GPIO signal */
	if (val)
		chip->gpio_state |= 1 << gpio;
	else
		chip->gpio_state &= ~(1 << gpio);
	out_be32(mm_gc->regs + XGPIO_DATA_OFFSET, chip->gpio_state);

	/* Clear the GPIO bit in shadow register and set direction as output */
	chip->gpio_dir &= (~(1 << gpio));
	out_be32(mm_gc->regs + XGPIO_TRI_OFFSET, chip->gpio_dir);

	spin_unlock_irqrestore(&chip->gpio_lock, flags);

	return 0;
}

/**
 * xgpio_save_regs - Set initial values of GPIO pins
 * @mm_gc: pointer to memory mapped GPIO chip structure
 */
static void xgpio_save_regs(struct of_mm_gpio_chip *mm_gc)
{
	struct xgpio_instance *chip =
	    container_of(mm_gc, struct xgpio_instance, mmchip);

	out_be32(mm_gc->regs + XGPIO_DATA_OFFSET, chip->gpio_state);
	out_be32(mm_gc->regs + XGPIO_TRI_OFFSET, chip->gpio_dir);
}

/**
 * xgpio_of_probe - Probe method for the GPIO device.
 * @np: pointer to device tree node
 *
 * This function probes the GPIO device in the device tree. It initializes the
 * driver data structure. It returns 0, if the driver is bound to the GPIO
 * device, or a negative value if there is an error.
 */
static int __devinit xgpio_of_probe(struct device_node *np)
{
	struct xgpio_instance *chip;
	int status = 0;
	const u32 *tree_info;

	chip = kzalloc(sizeof(*chip), GFP_KERNEL);
	if (!chip)
		return -ENOMEM;

	/* Update GPIO state shadow register with default value */
	tree_info = of_get_property(np, "xlnx,dout-default", NULL);
	if (tree_info)
		chip->gpio_state = *tree_info;

	/* Update GPIO direction shadow register with default value */
	chip->gpio_dir = 0xFFFFFFFF; /* By default, all pins are inputs */
	tree_info = of_get_property(np, "xlnx,tri-default", NULL);
	if (tree_info)
		chip->gpio_dir = *tree_info;

	/* Check device node and parent device node for device width */
	chip->mmchip.gc.ngpio = 32; /* By default assume full GPIO controller */
	tree_info = of_get_property(np, "xlnx,gpio-width", NULL);
	if (!tree_info)
		tree_info = of_get_property(np->parent,
					    "xlnx,gpio-width", NULL);
	if (tree_info)
		chip->mmchip.gc.ngpio = *tree_info;

	spin_lock_init(&chip->gpio_lock);

	chip->mmchip.gc.of_gpio_n_cells = 2;
	chip->mmchip.gc.direction_input = xgpio_dir_in;
	chip->mmchip.gc.direction_output = xgpio_dir_out;
	chip->mmchip.gc.get = xgpio_get;
	chip->mmchip.gc.set = xgpio_set;

	chip->mmchip.save_regs = xgpio_save_regs;

	/* Call the OF gpio helper to setup and register the GPIO device */
	status = of_mm_gpiochip_add(np, &chip->mmchip);
	if (status) {
		kfree(chip);
		pr_err("%s: error in probe function with status %d\n",
		       np->full_name, status);
		return status;
	}
	pr_info("XGpio: %s: registered\n", np->full_name);
	return 0;
}

static struct of_device_id xgpio_of_match[] __devinitdata = {
	{ .compatible = "xlnx,xps-gpio-1.00.a", },
	{ /* end of list */ },
};

static int __init xgpio_init(void)
{
	struct device_node *np;

	for_each_matching_node(np, xgpio_of_match)
		xgpio_of_probe(np);

	return 0;
}

/* Make sure we get initialized before anyone else tries to use us */
subsys_initcall(xgpio_init);
/* No exit call at the moment as we cannot unregister of GPIO chips */

MODULE_AUTHOR("Xilinx, Inc.");
MODULE_DESCRIPTION("Xilinx GPIO driver");
MODULE_LICENSE("GPL");