/*
 *  SYSCON GPIO driver
 *
 *  Copyright (C) 2014 Alexander Shiyan <shc_work@mail.ru>
 *
 * 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.
 */

#include <linux/err.h>
#include <linux/gpio.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/regmap.h>
#include <linux/mfd/syscon.h>

#define GPIO_SYSCON_FEAT_IN	BIT(0)
#define GPIO_SYSCON_FEAT_OUT	BIT(1)
#define GPIO_SYSCON_FEAT_DIR	BIT(2)

/* SYSCON driver is designed to use 32-bit wide registers */
#define SYSCON_REG_SIZE		(4)
#define SYSCON_REG_BITS		(SYSCON_REG_SIZE * 8)

/**
 * struct syscon_gpio_data - Configuration for the device.
 * compatible:		SYSCON driver compatible string.
 * flags:		Set of GPIO_SYSCON_FEAT_ flags:
 *			GPIO_SYSCON_FEAT_IN:	GPIOs supports input,
 *			GPIO_SYSCON_FEAT_OUT:	GPIOs supports output,
 *			GPIO_SYSCON_FEAT_DIR:	GPIOs supports switch direction.
 * bit_count:		Number of bits used as GPIOs.
 * dat_bit_offset:	Offset (in bits) to the first GPIO bit.
 * dir_bit_offset:	Optional offset (in bits) to the first bit to switch
 *			GPIO direction (Used with GPIO_SYSCON_FEAT_DIR flag).
 */

struct syscon_gpio_data {
	const char	*compatible;
	unsigned int	flags;
	unsigned int	bit_count;
	unsigned int	dat_bit_offset;
	unsigned int	dir_bit_offset;
};

struct syscon_gpio_priv {
	struct gpio_chip		chip;
	struct regmap			*syscon;
	const struct syscon_gpio_data	*data;
};

static inline struct syscon_gpio_priv *to_syscon_gpio(struct gpio_chip *chip)
{
	return container_of(chip, struct syscon_gpio_priv, chip);
}

static int syscon_gpio_get(struct gpio_chip *chip, unsigned offset)
{
	struct syscon_gpio_priv *priv = to_syscon_gpio(chip);
	unsigned int val, offs = priv->data->dat_bit_offset + offset;
	int ret;

	ret = regmap_read(priv->syscon,
			  (offs / SYSCON_REG_BITS) * SYSCON_REG_SIZE, &val);
	if (ret)
		return ret;

	return !!(val & BIT(offs % SYSCON_REG_BITS));
}

static void syscon_gpio_set(struct gpio_chip *chip, unsigned offset, int val)
{
	struct syscon_gpio_priv *priv = to_syscon_gpio(chip);
	unsigned int offs = priv->data->dat_bit_offset + offset;

	regmap_update_bits(priv->syscon,
			   (offs / SYSCON_REG_BITS) * SYSCON_REG_SIZE,
			   BIT(offs % SYSCON_REG_BITS),
			   val ? BIT(offs % SYSCON_REG_BITS) : 0);
}

static int syscon_gpio_dir_in(struct gpio_chip *chip, unsigned offset)
{
	struct syscon_gpio_priv *priv = to_syscon_gpio(chip);

	if (priv->data->flags & GPIO_SYSCON_FEAT_DIR) {
		unsigned int offs = priv->data->dir_bit_offset + offset;

		regmap_update_bits(priv->syscon,
				   (offs / SYSCON_REG_BITS) * SYSCON_REG_SIZE,
				   BIT(offs % SYSCON_REG_BITS), 0);
	}

	return 0;
}

static int syscon_gpio_dir_out(struct gpio_chip *chip, unsigned offset, int val)
{
	struct syscon_gpio_priv *priv = to_syscon_gpio(chip);

	if (priv->data->flags & GPIO_SYSCON_FEAT_DIR) {
		unsigned int offs = priv->data->dir_bit_offset + offset;

		regmap_update_bits(priv->syscon,
				   (offs / SYSCON_REG_BITS) * SYSCON_REG_SIZE,
				   BIT(offs % SYSCON_REG_BITS),
				   BIT(offs % SYSCON_REG_BITS));
	}

	syscon_gpio_set(chip, offset, val);

	return 0;
}

static const struct syscon_gpio_data clps711x_mctrl_gpio = {
	/* ARM CLPS711X SYSFLG1 Bits 8-10 */
	.compatible	= "cirrus,clps711x-syscon1",
	.flags		= GPIO_SYSCON_FEAT_IN,
	.bit_count	= 3,
	.dat_bit_offset	= 0x40 * 8 + 8,
};

static const struct of_device_id syscon_gpio_ids[] = {
	{
		.compatible	= "cirrus,clps711x-mctrl-gpio",
		.data		= &clps711x_mctrl_gpio,
	},
	{ }
};
MODULE_DEVICE_TABLE(of, syscon_gpio_ids);

static int syscon_gpio_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	const struct of_device_id *of_id = of_match_device(syscon_gpio_ids, dev);
	struct syscon_gpio_priv *priv;

	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
	if (!priv)
		return -ENOMEM;

	priv->data = of_id->data;

	priv->syscon =
		syscon_regmap_lookup_by_compatible(priv->data->compatible);
	if (IS_ERR(priv->syscon))
		return PTR_ERR(priv->syscon);

	priv->chip.dev = dev;
	priv->chip.owner = THIS_MODULE;
	priv->chip.label = dev_name(dev);
	priv->chip.base = -1;
	priv->chip.ngpio = priv->data->bit_count;
	priv->chip.get = syscon_gpio_get;
	if (priv->data->flags & GPIO_SYSCON_FEAT_IN)
		priv->chip.direction_input = syscon_gpio_dir_in;
	if (priv->data->flags & GPIO_SYSCON_FEAT_OUT) {
		priv->chip.set = syscon_gpio_set;
		priv->chip.direction_output = syscon_gpio_dir_out;
	}

	platform_set_drvdata(pdev, priv);

	return gpiochip_add(&priv->chip);
}

static int syscon_gpio_remove(struct platform_device *pdev)
{
	struct syscon_gpio_priv *priv = platform_get_drvdata(pdev);

	return gpiochip_remove(&priv->chip);
}

static struct platform_driver syscon_gpio_driver = {
	.driver	= {
		.name		= "gpio-syscon",
		.owner		= THIS_MODULE,
		.of_match_table	= syscon_gpio_ids,
	},
	.probe	= syscon_gpio_probe,
	.remove	= syscon_gpio_remove,
};
module_platform_driver(syscon_gpio_driver);

MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>");
MODULE_DESCRIPTION("SYSCON GPIO driver");
MODULE_LICENSE("GPL");