1/*
  2 * exynos-rng.c - Random Number Generator driver for the exynos
  3 *
  4 * Copyright (C) 2012 Samsung Electronics
  5 * Jonghwa Lee <jonghwa3.lee@smasung.com>
  6 *
  7 * This program is free software; you can redistribute it and/or modify
  8 * it under the terms of the GNU General Public License as published by
  9 * the Free Software Foundation;
 10 *
 11 * This program is distributed in the hope that it will be useful,
 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 14 * GNU General Public License for more details.
 15 *
 16 * You should have received a copy of the GNU General Public License
 17 * along with this program; if not, write to the Free Software
 18 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 19 *
 20 */
 21
 22#include <linux/hw_random.h>
 23#include <linux/kernel.h>
 24#include <linux/module.h>
 25#include <linux/io.h>
 26#include <linux/platform_device.h>
 27#include <linux/clk.h>
 28#include <linux/pm_runtime.h>
 29#include <linux/err.h>
 30
 31#define EXYNOS_PRNG_STATUS_OFFSET	0x10
 32#define EXYNOS_PRNG_SEED_OFFSET		0x140
 33#define EXYNOS_PRNG_OUT1_OFFSET		0x160
 34#define SEED_SETTING_DONE		BIT(1)
 35#define PRNG_START			0x18
 36#define PRNG_DONE			BIT(5)
 37#define EXYNOS_AUTOSUSPEND_DELAY	100
 38
 39struct exynos_rng {
 40	struct device *dev;
 41	struct hwrng rng;
 42	void __iomem *mem;
 43	struct clk *clk;
 44};
 45
 46static u32 exynos_rng_readl(struct exynos_rng *rng, u32 offset)
 47{
 48	return	__raw_readl(rng->mem + offset);
 49}
 50
 51static void exynos_rng_writel(struct exynos_rng *rng, u32 val, u32 offset)
 52{
 53	__raw_writel(val, rng->mem + offset);
 54}
 55
 56static int exynos_init(struct hwrng *rng)
 57{
 58	struct exynos_rng *exynos_rng = container_of(rng,
 59						struct exynos_rng, rng);
 60	int i;
 61	int ret = 0;
 62
 63	pm_runtime_get_sync(exynos_rng->dev);
 64
 65	for (i = 0 ; i < 5 ; i++)
 66		exynos_rng_writel(exynos_rng, jiffies,
 67				EXYNOS_PRNG_SEED_OFFSET + 4*i);
 68
 69	if (!(exynos_rng_readl(exynos_rng, EXYNOS_PRNG_STATUS_OFFSET)
 70						 & SEED_SETTING_DONE))
 71		ret = -EIO;
 72
 73	pm_runtime_put_noidle(exynos_rng->dev);
 74
 75	return ret;
 76}
 77
 78static int exynos_read(struct hwrng *rng, void *buf,
 79					size_t max, bool wait)
 80{
 81	struct exynos_rng *exynos_rng = container_of(rng,
 82						struct exynos_rng, rng);
 83	u32 *data = buf;
 84
 85	pm_runtime_get_sync(exynos_rng->dev);
 86
 87	exynos_rng_writel(exynos_rng, PRNG_START, 0);
 88
 89	while (!(exynos_rng_readl(exynos_rng,
 90			EXYNOS_PRNG_STATUS_OFFSET) & PRNG_DONE))
 91		cpu_relax();
 92
 93	exynos_rng_writel(exynos_rng, PRNG_DONE, EXYNOS_PRNG_STATUS_OFFSET);
 94
 95	*data = exynos_rng_readl(exynos_rng, EXYNOS_PRNG_OUT1_OFFSET);
 96
 97	pm_runtime_mark_last_busy(exynos_rng->dev);
 98	pm_runtime_autosuspend(exynos_rng->dev);
 99
100	return 4;
101}
102
103static int exynos_rng_probe(struct platform_device *pdev)
104{
105	struct exynos_rng *exynos_rng;
106	struct resource *res;
107
108	exynos_rng = devm_kzalloc(&pdev->dev, sizeof(struct exynos_rng),
109					GFP_KERNEL);
110	if (!exynos_rng)
111		return -ENOMEM;
112
113	exynos_rng->dev = &pdev->dev;
114	exynos_rng->rng.name = "exynos";
115	exynos_rng->rng.init =	exynos_init;
116	exynos_rng->rng.read = exynos_read;
117	exynos_rng->clk = devm_clk_get(&pdev->dev, "secss");
118	if (IS_ERR(exynos_rng->clk)) {
119		dev_err(&pdev->dev, "Couldn't get clock.\n");
120		return -ENOENT;
121	}
122
123	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
124	exynos_rng->mem = devm_ioremap_resource(&pdev->dev, res);
125	if (IS_ERR(exynos_rng->mem))
126		return PTR_ERR(exynos_rng->mem);
127
128	platform_set_drvdata(pdev, exynos_rng);
129
130	pm_runtime_set_autosuspend_delay(&pdev->dev, EXYNOS_AUTOSUSPEND_DELAY);
131	pm_runtime_use_autosuspend(&pdev->dev);
132	pm_runtime_enable(&pdev->dev);
133
134	return hwrng_register(&exynos_rng->rng);
135}
136
137static int exynos_rng_remove(struct platform_device *pdev)
138{
139	struct exynos_rng *exynos_rng = platform_get_drvdata(pdev);
140
141	hwrng_unregister(&exynos_rng->rng);
142
143	return 0;
144}
145
146#if defined(CONFIG_PM_SLEEP) || defined(CONFIG_PM_RUNTIME)
147static int exynos_rng_runtime_suspend(struct device *dev)
148{
149	struct platform_device *pdev = to_platform_device(dev);
150	struct exynos_rng *exynos_rng = platform_get_drvdata(pdev);
151
152	clk_disable_unprepare(exynos_rng->clk);
153
154	return 0;
155}
156
157static int exynos_rng_runtime_resume(struct device *dev)
158{
159	struct platform_device *pdev = to_platform_device(dev);
160	struct exynos_rng *exynos_rng = platform_get_drvdata(pdev);
161
162	return clk_prepare_enable(exynos_rng->clk);
163}
164#endif
165
166static UNIVERSAL_DEV_PM_OPS(exynos_rng_pm_ops, exynos_rng_runtime_suspend,
167					exynos_rng_runtime_resume, NULL);
168
169static struct platform_driver exynos_rng_driver = {
170	.driver		= {
171		.name	= "exynos-rng",
172		.owner	= THIS_MODULE,
173		.pm	= &exynos_rng_pm_ops,
174	},
175	.probe		= exynos_rng_probe,
176	.remove		= exynos_rng_remove,
177};
178
179module_platform_driver(exynos_rng_driver);
180
181MODULE_DESCRIPTION("EXYNOS 4 H/W Random Number Generator driver");
182MODULE_AUTHOR("Jonghwa Lee <jonghwa3.lee@samsung.com>");
183MODULE_LICENSE("GPL");