/*
 * AppliedMicro X-Gene SoC GPIO Driver
 *
 * Copyright (c) 2014, Applied Micro Circuits Corporation
 * Author: Feng Kan <fkan@apm.com>.
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/spinlock.h>
#include <linux/platform_device.h>
#include <linux/gpio/driver.h>
#include <linux/types.h>
#include <linux/bitops.h>

#define GPIO_SET_DR_OFFSET	0x0C
#define GPIO_DATA_OFFSET	0x14
#define GPIO_BANK_STRIDE	0x0C

#define XGENE_GPIOS_PER_BANK	16
#define XGENE_MAX_GPIO_BANKS	3
#define XGENE_MAX_GPIOS		(XGENE_GPIOS_PER_BANK * XGENE_MAX_GPIO_BANKS)

#define GPIO_BIT_OFFSET(x)	(x % XGENE_GPIOS_PER_BANK)
#define GPIO_BANK_OFFSET(x)	((x / XGENE_GPIOS_PER_BANK) * GPIO_BANK_STRIDE)

struct xgene_gpio {
	struct gpio_chip	chip;
	void __iomem		*base;
	spinlock_t		lock;
	u32			set_dr_val[XGENE_MAX_GPIO_BANKS];
};

static inline struct xgene_gpio *to_xgene_gpio(struct gpio_chip *chip)
{
	return container_of(chip, struct xgene_gpio, chip);
}

static int xgene_gpio_get(struct gpio_chip *gc, unsigned int offset)
{
	struct xgene_gpio *chip = to_xgene_gpio(gc);
	unsigned long bank_offset;
	u32 bit_offset;

	bank_offset = GPIO_DATA_OFFSET + GPIO_BANK_OFFSET(offset);
	bit_offset = GPIO_BIT_OFFSET(offset);
	return !!(ioread32(chip->base + bank_offset) & BIT(bit_offset));
}

static void __xgene_gpio_set(struct gpio_chip *gc, unsigned int offset, int val)
{
	struct xgene_gpio *chip = to_xgene_gpio(gc);
	unsigned long bank_offset;
	u32 setval, bit_offset;

	bank_offset = GPIO_SET_DR_OFFSET + GPIO_BANK_OFFSET(offset);
	bit_offset = GPIO_BIT_OFFSET(offset) + XGENE_GPIOS_PER_BANK;

	setval = ioread32(chip->base + bank_offset);
	if (val)
		setval |= BIT(bit_offset);
	else
		setval &= ~BIT(bit_offset);
	iowrite32(setval, chip->base + bank_offset);
}

static void xgene_gpio_set(struct gpio_chip *gc, unsigned int offset, int val)
{
	struct xgene_gpio *chip = to_xgene_gpio(gc);
	unsigned long flags;

	spin_lock_irqsave(&chip->lock, flags);
	__xgene_gpio_set(gc, offset, val);
	spin_unlock_irqrestore(&chip->lock, flags);
}

static int xgene_gpio_dir_in(struct gpio_chip *gc, unsigned int offset)
{
	struct xgene_gpio *chip = to_xgene_gpio(gc);
	unsigned long flags, bank_offset;
	u32 dirval, bit_offset;

	bank_offset = GPIO_SET_DR_OFFSET + GPIO_BANK_OFFSET(offset);
	bit_offset = GPIO_BIT_OFFSET(offset);

	spin_lock_irqsave(&chip->lock, flags);

	dirval = ioread32(chip->base + bank_offset);
	dirval |= BIT(bit_offset);
	iowrite32(dirval, chip->base + bank_offset);

	spin_unlock_irqrestore(&chip->lock, flags);

	return 0;
}

static int xgene_gpio_dir_out(struct gpio_chip *gc,
					unsigned int offset, int val)
{
	struct xgene_gpio *chip = to_xgene_gpio(gc);
	unsigned long flags, bank_offset;
	u32 dirval, bit_offset;

	bank_offset = GPIO_SET_DR_OFFSET + GPIO_BANK_OFFSET(offset);
	bit_offset = GPIO_BIT_OFFSET(offset);

	spin_lock_irqsave(&chip->lock, flags);

	dirval = ioread32(chip->base + bank_offset);
	dirval &= ~BIT(bit_offset);
	iowrite32(dirval, chip->base + bank_offset);
	__xgene_gpio_set(gc, offset, val);

	spin_unlock_irqrestore(&chip->lock, flags);

	return 0;
}

static __maybe_unused int xgene_gpio_suspend(struct device *dev)
{
	struct xgene_gpio *gpio = dev_get_drvdata(dev);
	unsigned long bank_offset;
	unsigned int bank;

	for (bank = 0; bank < XGENE_MAX_GPIO_BANKS; bank++) {
		bank_offset = GPIO_SET_DR_OFFSET + bank * GPIO_BANK_STRIDE;
		gpio->set_dr_val[bank] = ioread32(gpio->base + bank_offset);
	}
	return 0;
}

static __maybe_unused int xgene_gpio_resume(struct device *dev)
{
	struct xgene_gpio *gpio = dev_get_drvdata(dev);
	unsigned long bank_offset;
	unsigned int bank;

	for (bank = 0; bank < XGENE_MAX_GPIO_BANKS; bank++) {
		bank_offset = GPIO_SET_DR_OFFSET + bank * GPIO_BANK_STRIDE;
		iowrite32(gpio->set_dr_val[bank], gpio->base + bank_offset);
	}
	return 0;
}

static SIMPLE_DEV_PM_OPS(xgene_gpio_pm, xgene_gpio_suspend, xgene_gpio_resume);

static int xgene_gpio_probe(struct platform_device *pdev)
{
	struct resource *res;
	struct xgene_gpio *gpio;
	int err = 0;

	gpio = devm_kzalloc(&pdev->dev, sizeof(*gpio), GFP_KERNEL);
	if (!gpio) {
		err = -ENOMEM;
		goto err;
	}

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	gpio->base = devm_ioremap_nocache(&pdev->dev, res->start,
							resource_size(res));
	if (!gpio->base) {
		err = -ENOMEM;
		goto err;
	}

	gpio->chip.ngpio = XGENE_MAX_GPIOS;

	spin_lock_init(&gpio->lock);
	gpio->chip.dev = &pdev->dev;
	gpio->chip.direction_input = xgene_gpio_dir_in;
	gpio->chip.direction_output = xgene_gpio_dir_out;
	gpio->chip.get = xgene_gpio_get;
	gpio->chip.set = xgene_gpio_set;
	gpio->chip.label = dev_name(&pdev->dev);
	gpio->chip.base = -1;

	platform_set_drvdata(pdev, gpio);

	err = gpiochip_add(&gpio->chip);
	if (err) {
		dev_err(&pdev->dev,
			"failed to register gpiochip.\n");
		goto err;
	}

	dev_info(&pdev->dev, "X-Gene GPIO driver registered.\n");
	return 0;
err:
	dev_err(&pdev->dev, "X-Gene GPIO driver registration failed.\n");
	return err;
}

static int xgene_gpio_remove(struct platform_device *pdev)
{
	struct xgene_gpio *gpio = platform_get_drvdata(pdev);

	gpiochip_remove(&gpio->chip);
	return 0;
}

static const struct of_device_id xgene_gpio_of_match[] = {
	{ .compatible = "apm,xgene-gpio", },
	{},
};
MODULE_DEVICE_TABLE(of, xgene_gpio_of_match);

static struct platform_driver xgene_gpio_driver = {
	.driver = {
		.name = "xgene-gpio",
		.of_match_table = xgene_gpio_of_match,
		.pm     = &xgene_gpio_pm,
	},
	.probe = xgene_gpio_probe,
	.remove = xgene_gpio_remove,
};

module_platform_driver(xgene_gpio_driver);

MODULE_AUTHOR("Feng Kan <fkan@apm.com>");
MODULE_DESCRIPTION("APM X-Gene GPIO driver");
MODULE_LICENSE("GPL");