1/*
  2 * Copyright (c) 2011 Peter Korsgaard <jacmet@sunsite.dk>
  3 *
  4 * This file is licensed under  the terms of the GNU General Public
  5 * License version 2. This program is licensed "as is" without any
  6 * warranty of any kind, whether express or implied.
  7 */
  8
  9#include <linux/kernel.h>
 10#include <linux/module.h>
 11#include <linux/mod_devicetable.h>
 12#include <linux/slab.h>
 13#include <linux/err.h>
 14#include <linux/clk.h>
 15#include <linux/io.h>
 16#include <linux/hw_random.h>
 17#include <linux/platform_device.h>
 18
 19#define TRNG_CR		0x00
 20#define TRNG_ISR	0x1c
 21#define TRNG_ODATA	0x50
 22
 23#define TRNG_KEY	0x524e4700 /* RNG */
 24
 25struct atmel_trng {
 26	struct clk *clk;
 27	void __iomem *base;
 28	struct hwrng rng;
 29};
 30
 31static int atmel_trng_read(struct hwrng *rng, void *buf, size_t max,
 32			   bool wait)
 33{
 34	struct atmel_trng *trng = container_of(rng, struct atmel_trng, rng);
 35	u32 *data = buf;
 36
 37	/* data ready? */
 38	if (readl(trng->base + TRNG_ISR) & 1) {
 39		*data = readl(trng->base + TRNG_ODATA);
 40		/*
 41		  ensure data ready is only set again AFTER the next data
 42		  word is ready in case it got set between checking ISR
 43		  and reading ODATA, so we don't risk re-reading the
 44		  same word
 45		*/
 46		readl(trng->base + TRNG_ISR);
 47		return 4;
 48	} else
 49		return 0;
 50}
 51
 52static void atmel_trng_enable(struct atmel_trng *trng)
 53{
 54	writel(TRNG_KEY | 1, trng->base + TRNG_CR);
 55}
 56
 57static void atmel_trng_disable(struct atmel_trng *trng)
 58{
 59	writel(TRNG_KEY, trng->base + TRNG_CR);
 60}
 61
 62static int atmel_trng_probe(struct platform_device *pdev)
 63{
 64	struct atmel_trng *trng;
 65	struct resource *res;
 66	int ret;
 67
 68	trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
 69	if (!trng)
 70		return -ENOMEM;
 71
 72	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 73	trng->base = devm_ioremap_resource(&pdev->dev, res);
 74	if (IS_ERR(trng->base))
 75		return PTR_ERR(trng->base);
 76
 77	trng->clk = devm_clk_get(&pdev->dev, NULL);
 78	if (IS_ERR(trng->clk))
 79		return PTR_ERR(trng->clk);
 80
 81	ret = clk_prepare_enable(trng->clk);
 82	if (ret)
 83		return ret;
 84
 85	atmel_trng_enable(trng);
 86	trng->rng.name = pdev->name;
 87	trng->rng.read = atmel_trng_read;
 88
 89	ret = devm_hwrng_register(&pdev->dev, &trng->rng);
 90	if (ret)
 91		goto err_register;
 92
 93	platform_set_drvdata(pdev, trng);
 94
 95	return 0;
 96
 97err_register:
 98	clk_disable_unprepare(trng->clk);
 99	return ret;
100}
101
102static int atmel_trng_remove(struct platform_device *pdev)
103{
104	struct atmel_trng *trng = platform_get_drvdata(pdev);
105
106
107	atmel_trng_disable(trng);
108	clk_disable_unprepare(trng->clk);
109
110	return 0;
111}
112
113#ifdef CONFIG_PM
114static int atmel_trng_suspend(struct device *dev)
115{
116	struct atmel_trng *trng = dev_get_drvdata(dev);
117
118	atmel_trng_disable(trng);
119	clk_disable_unprepare(trng->clk);
120
121	return 0;
122}
123
124static int atmel_trng_resume(struct device *dev)
125{
126	struct atmel_trng *trng = dev_get_drvdata(dev);
127	int ret;
128
129	ret = clk_prepare_enable(trng->clk);
130	if (ret)
131		return ret;
132
133	atmel_trng_enable(trng);
134
135	return 0;
136}
137
138static const struct dev_pm_ops atmel_trng_pm_ops = {
139	.suspend	= atmel_trng_suspend,
140	.resume		= atmel_trng_resume,
141};
142#endif /* CONFIG_PM */
143
144static const struct of_device_id atmel_trng_dt_ids[] = {
145	{ .compatible = "atmel,at91sam9g45-trng" },
146	{ /* sentinel */ }
147};
148MODULE_DEVICE_TABLE(of, atmel_trng_dt_ids);
149
150static struct platform_driver atmel_trng_driver = {
151	.probe		= atmel_trng_probe,
152	.remove		= atmel_trng_remove,
153	.driver		= {
154		.name	= "atmel-trng",
155#ifdef CONFIG_PM
156		.pm	= &atmel_trng_pm_ops,
157#endif /* CONFIG_PM */
158		.of_match_table = atmel_trng_dt_ids,
159	},
160};
161
162module_platform_driver(atmel_trng_driver);
163
164MODULE_LICENSE("GPL");
165MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>");
166MODULE_DESCRIPTION("Atmel true random number generator driver");