/*
 * 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/module.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 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 = be32_to_cpup(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 = be32_to_cpup(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 = be32_to_cpup(tree_info);

        spin_lock_init(&chip->gpio_lock);

        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;
        }
        return 0;
}

static struct of_device_id xgpio_of_match[] = {
        { .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");