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_rng_configure(struct exynos_rng *exynos_rng)
 57{
 58	int i;
 59	int ret = 0;
 60
 61	for (i = 0 ; i < 5 ; i++)
 62		exynos_rng_writel(exynos_rng, jiffies,
 63				EXYNOS_PRNG_SEED_OFFSET + 4*i);
 64
 65	if (!(exynos_rng_readl(exynos_rng, EXYNOS_PRNG_STATUS_OFFSET)
 66						 & SEED_SETTING_DONE))
 67		ret = -EIO;
 68
 69	return ret;
 70}
 71
 72static int exynos_init(struct hwrng *rng)
 73{
 74	struct exynos_rng *exynos_rng = container_of(rng,
 75						struct exynos_rng, rng);
 76	int ret = 0;
 77
 78	pm_runtime_get_sync(exynos_rng->dev);
 79	ret = exynos_rng_configure(exynos_rng);
 80	pm_runtime_put_noidle(exynos_rng->dev);
 81
 82	return ret;
 83}
 84
 85static int exynos_read(struct hwrng *rng, void *buf,
 86					size_t max, bool wait)
 87{
 88	struct exynos_rng *exynos_rng = container_of(rng,
 89						struct exynos_rng, rng);
 90	u32 *data = buf;
 91	int retry = 100;
 92
 93	pm_runtime_get_sync(exynos_rng->dev);
 94
 95	exynos_rng_writel(exynos_rng, PRNG_START, 0);
 96
 97	while (!(exynos_rng_readl(exynos_rng,
 98			EXYNOS_PRNG_STATUS_OFFSET) & PRNG_DONE) && --retry)
 99		cpu_relax();
100	if (!retry)
101		return -ETIMEDOUT;
102
103	exynos_rng_writel(exynos_rng, PRNG_DONE, EXYNOS_PRNG_STATUS_OFFSET);
104
105	*data = exynos_rng_readl(exynos_rng, EXYNOS_PRNG_OUT1_OFFSET);
106
107	pm_runtime_mark_last_busy(exynos_rng->dev);
108	pm_runtime_put_sync_autosuspend(exynos_rng->dev);
109
110	return 4;
111}
112
113static int exynos_rng_probe(struct platform_device *pdev)
114{
115	struct exynos_rng *exynos_rng;
116	struct resource *res;
117
118	exynos_rng = devm_kzalloc(&pdev->dev, sizeof(struct exynos_rng),
119					GFP_KERNEL);
120	if (!exynos_rng)
121		return -ENOMEM;
122
123	exynos_rng->dev = &pdev->dev;
124	exynos_rng->rng.name = "exynos";
125	exynos_rng->rng.init =	exynos_init;
126	exynos_rng->rng.read = exynos_read;
127	exynos_rng->clk = devm_clk_get(&pdev->dev, "secss");
128	if (IS_ERR(exynos_rng->clk)) {
129		dev_err(&pdev->dev, "Couldn't get clock.\n");
130		return -ENOENT;
131	}
132
133	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
134	exynos_rng->mem = devm_ioremap_resource(&pdev->dev, res);
135	if (IS_ERR(exynos_rng->mem))
136		return PTR_ERR(exynos_rng->mem);
137
138	platform_set_drvdata(pdev, exynos_rng);
139
140	pm_runtime_set_autosuspend_delay(&pdev->dev, EXYNOS_AUTOSUSPEND_DELAY);
141	pm_runtime_use_autosuspend(&pdev->dev);
142	pm_runtime_enable(&pdev->dev);
143
144	return devm_hwrng_register(&pdev->dev, &exynos_rng->rng);
145}
146
147static int __maybe_unused 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 __maybe_unused 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
165static int __maybe_unused exynos_rng_suspend(struct device *dev)
166{
167	return pm_runtime_force_suspend(dev);
168}
169
170static int __maybe_unused exynos_rng_resume(struct device *dev)
171{
172	struct platform_device *pdev = to_platform_device(dev);
173	struct exynos_rng *exynos_rng = platform_get_drvdata(pdev);
174	int ret;
175
176	ret = pm_runtime_force_resume(dev);
177	if (ret)
178		return ret;
179
180	return exynos_rng_configure(exynos_rng);
181}
182
183static const struct dev_pm_ops exynos_rng_pm_ops = {
184	SET_SYSTEM_SLEEP_PM_OPS(exynos_rng_suspend, exynos_rng_resume)
185	SET_RUNTIME_PM_OPS(exynos_rng_runtime_suspend,
186			   exynos_rng_runtime_resume, NULL)
187};
188
189static const struct of_device_id exynos_rng_dt_match[] = {
190	{
191		.compatible = "samsung,exynos4-rng",
192	},
193	{ },
194};
195MODULE_DEVICE_TABLE(of, exynos_rng_dt_match);
196
197static struct platform_driver exynos_rng_driver = {
198	.driver		= {
199		.name	= "exynos-rng",
200		.pm	= &exynos_rng_pm_ops,
201		.of_match_table = exynos_rng_dt_match,
202	},
203	.probe		= exynos_rng_probe,
204};
205
206module_platform_driver(exynos_rng_driver);
207
208MODULE_DESCRIPTION("EXYNOS 4 H/W Random Number Generator driver");
209MODULE_AUTHOR("Jonghwa Lee <jonghwa3.lee@samsung.com>");
210MODULE_LICENSE("GPL");