/*
 * exynos-rng.c - Random Number Generator driver for the exynos
 *
 * Copyright (C) 2012 Samsung Electronics
 * Jonghwa Lee <jonghwa3.lee@smasung.com>
 *
 * 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;
 *
 * 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */

#include <linux/hw_random.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/io.h>
#include <linux/platform_device.h>
#include <linux/clk.h>
#include <linux/pm_runtime.h>
#include <linux/err.h>

#define EXYNOS_PRNG_STATUS_OFFSET	0x10
#define EXYNOS_PRNG_SEED_OFFSET		0x140
#define EXYNOS_PRNG_OUT1_OFFSET		0x160
#define SEED_SETTING_DONE		BIT(1)
#define PRNG_START			0x18
#define PRNG_DONE			BIT(5)
#define EXYNOS_AUTOSUSPEND_DELAY	100

struct exynos_rng {
	struct device *dev;
	struct hwrng rng;
	void __iomem *mem;
	struct clk *clk;
};

static u32 exynos_rng_readl(struct exynos_rng *rng, u32 offset)
{
	return	__raw_readl(rng->mem + offset);
}

static void exynos_rng_writel(struct exynos_rng *rng, u32 val, u32 offset)
{
	__raw_writel(val, rng->mem + offset);
}

static int exynos_init(struct hwrng *rng)
{
	struct exynos_rng *exynos_rng = container_of(rng,
						struct exynos_rng, rng);
	int i;
	int ret = 0;

	pm_runtime_get_sync(exynos_rng->dev);

	for (i = 0 ; i < 5 ; i++)
		exynos_rng_writel(exynos_rng, jiffies,
				EXYNOS_PRNG_SEED_OFFSET + 4*i);

	if (!(exynos_rng_readl(exynos_rng, EXYNOS_PRNG_STATUS_OFFSET)
						 & SEED_SETTING_DONE))
		ret = -EIO;

	pm_runtime_put_noidle(exynos_rng->dev);

	return ret;
}

static int exynos_read(struct hwrng *rng, void *buf,
					size_t max, bool wait)
{
	struct exynos_rng *exynos_rng = container_of(rng,
						struct exynos_rng, rng);
	u32 *data = buf;

	pm_runtime_get_sync(exynos_rng->dev);

	exynos_rng_writel(exynos_rng, PRNG_START, 0);

	while (!(exynos_rng_readl(exynos_rng,
			EXYNOS_PRNG_STATUS_OFFSET) & PRNG_DONE))
		cpu_relax();

	exynos_rng_writel(exynos_rng, PRNG_DONE, EXYNOS_PRNG_STATUS_OFFSET);

	*data = exynos_rng_readl(exynos_rng, EXYNOS_PRNG_OUT1_OFFSET);

	pm_runtime_mark_last_busy(exynos_rng->dev);
	pm_runtime_autosuspend(exynos_rng->dev);

	return 4;
}

static int exynos_rng_probe(struct platform_device *pdev)
{
	struct exynos_rng *exynos_rng;
	struct resource *res;

	exynos_rng = devm_kzalloc(&pdev->dev, sizeof(struct exynos_rng),
					GFP_KERNEL);
	if (!exynos_rng)
		return -ENOMEM;

	exynos_rng->dev = &pdev->dev;
	exynos_rng->rng.name = "exynos";
	exynos_rng->rng.init =	exynos_init;
	exynos_rng->rng.read = exynos_read;
	exynos_rng->clk = devm_clk_get(&pdev->dev, "secss");
	if (IS_ERR(exynos_rng->clk)) {
		dev_err(&pdev->dev, "Couldn't get clock.\n");
		return -ENOENT;
	}

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	exynos_rng->mem = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(exynos_rng->mem))
		return PTR_ERR(exynos_rng->mem);

	platform_set_drvdata(pdev, exynos_rng);

	pm_runtime_set_autosuspend_delay(&pdev->dev, EXYNOS_AUTOSUSPEND_DELAY);
	pm_runtime_use_autosuspend(&pdev->dev);
	pm_runtime_enable(&pdev->dev);

	return hwrng_register(&exynos_rng->rng);
}

static int exynos_rng_remove(struct platform_device *pdev)
{
	struct exynos_rng *exynos_rng = platform_get_drvdata(pdev);

	hwrng_unregister(&exynos_rng->rng);

	return 0;
}

#ifdef CONFIG_PM
static int exynos_rng_runtime_suspend(struct device *dev)
{
	struct platform_device *pdev = to_platform_device(dev);
	struct exynos_rng *exynos_rng = platform_get_drvdata(pdev);

	clk_disable_unprepare(exynos_rng->clk);

	return 0;
}

static int exynos_rng_runtime_resume(struct device *dev)
{
	struct platform_device *pdev = to_platform_device(dev);
	struct exynos_rng *exynos_rng = platform_get_drvdata(pdev);

	return clk_prepare_enable(exynos_rng->clk);
}
#endif

static UNIVERSAL_DEV_PM_OPS(exynos_rng_pm_ops, exynos_rng_runtime_suspend,
					exynos_rng_runtime_resume, NULL);

static struct platform_driver exynos_rng_driver = {
	.driver		= {
		.name	= "exynos-rng",
		.pm	= &exynos_rng_pm_ops,
	},
	.probe		= exynos_rng_probe,
	.remove		= exynos_rng_remove,
};

module_platform_driver(exynos_rng_driver);

MODULE_DESCRIPTION("EXYNOS 4 H/W Random Number Generator driver");
MODULE_AUTHOR("Jonghwa Lee <jonghwa3.lee@samsung.com>");
MODULE_LICENSE("GPL");