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/of_device.h>
 18#include <linux/platform_device.h>
 19
 20#define TRNG_CR		0x00
 21#define TRNG_MR		0x04
 22#define TRNG_ISR	0x1c
 23#define TRNG_ODATA	0x50
 24
 25#define TRNG_KEY	0x524e4700 /* RNG */
 26
 27#define TRNG_HALFR	BIT(0) /* generate RN every 168 cycles */
 28
 29struct atmel_trng_data {
 30	bool has_half_rate;
 31};
 32
 33struct atmel_trng {
 34	struct clk *clk;
 35	void __iomem *base;
 36	struct hwrng rng;
 37};
 38
 39static int atmel_trng_read(struct hwrng *rng, void *buf, size_t max,
 40			   bool wait)
 41{
 42	struct atmel_trng *trng = container_of(rng, struct atmel_trng, rng);
 43	u32 *data = buf;
 44
 45	/* data ready? */
 46	if (readl(trng->base + TRNG_ISR) & 1) {
 47		*data = readl(trng->base + TRNG_ODATA);
 48		/*
 49		  ensure data ready is only set again AFTER the next data
 50		  word is ready in case it got set between checking ISR
 51		  and reading ODATA, so we don't risk re-reading the
 52		  same word
 53		*/
 54		readl(trng->base + TRNG_ISR);
 55		return 4;
 56	} else
 57		return 0;
 58}
 59
 60static void atmel_trng_enable(struct atmel_trng *trng)
 61{
 62	writel(TRNG_KEY | 1, trng->base + TRNG_CR);
 63}
 64
 65static void atmel_trng_disable(struct atmel_trng *trng)
 66{
 67	writel(TRNG_KEY, trng->base + TRNG_CR);
 68}
 69
 70static int atmel_trng_probe(struct platform_device *pdev)
 71{
 72	struct atmel_trng *trng;
 73	const struct atmel_trng_data *data;
 74	int ret;
 75
 76	trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
 77	if (!trng)
 78		return -ENOMEM;
 79
 80	trng->base = devm_platform_ioremap_resource(pdev, 0);
 81	if (IS_ERR(trng->base))
 82		return PTR_ERR(trng->base);
 83
 84	trng->clk = devm_clk_get(&pdev->dev, NULL);
 85	if (IS_ERR(trng->clk))
 86		return PTR_ERR(trng->clk);
 87	data = of_device_get_match_data(&pdev->dev);
 88	if (!data)
 89		return -ENODEV;
 90
 91	if (data->has_half_rate) {
 92		unsigned long rate = clk_get_rate(trng->clk);
 93
 94		/* if peripheral clk is above 100MHz, set HALFR */
 95		if (rate > 100000000)
 96			writel(TRNG_HALFR, trng->base + TRNG_MR);
 97	}
 98
 99	ret = clk_prepare_enable(trng->clk);
100	if (ret)
101		return ret;
102
103	atmel_trng_enable(trng);
104	trng->rng.name = pdev->name;
105	trng->rng.read = atmel_trng_read;
106
107	ret = devm_hwrng_register(&pdev->dev, &trng->rng);
108	if (ret)
109		goto err_register;
110
111	platform_set_drvdata(pdev, trng);
112
113	return 0;
114
115err_register:
116	clk_disable_unprepare(trng->clk);
117	return ret;
118}
119
120static int atmel_trng_remove(struct platform_device *pdev)
121{
122	struct atmel_trng *trng = platform_get_drvdata(pdev);
123
124
125	atmel_trng_disable(trng);
126	clk_disable_unprepare(trng->clk);
127
128	return 0;
129}
130
131#ifdef CONFIG_PM
132static int atmel_trng_suspend(struct device *dev)
133{
134	struct atmel_trng *trng = dev_get_drvdata(dev);
135
136	atmel_trng_disable(trng);
137	clk_disable_unprepare(trng->clk);
138
139	return 0;
140}
141
142static int atmel_trng_resume(struct device *dev)
143{
144	struct atmel_trng *trng = dev_get_drvdata(dev);
145	int ret;
146
147	ret = clk_prepare_enable(trng->clk);
148	if (ret)
149		return ret;
150
151	atmel_trng_enable(trng);
152
153	return 0;
154}
155
156static const struct dev_pm_ops atmel_trng_pm_ops = {
157	.suspend	= atmel_trng_suspend,
158	.resume		= atmel_trng_resume,
159};
160#endif /* CONFIG_PM */
161
162static const struct atmel_trng_data at91sam9g45_config = {
163	.has_half_rate = false,
164};
165
166static const struct atmel_trng_data sam9x60_config = {
167	.has_half_rate = true,
168};
169
170static const struct of_device_id atmel_trng_dt_ids[] = {
171	{
172		.compatible = "atmel,at91sam9g45-trng",
173		.data = &at91sam9g45_config,
174	}, {
175		.compatible = "microchip,sam9x60-trng",
176		.data = &sam9x60_config,
177	}, {
178		/* sentinel */
179	}
180};
181MODULE_DEVICE_TABLE(of, atmel_trng_dt_ids);
182
183static struct platform_driver atmel_trng_driver = {
184	.probe		= atmel_trng_probe,
185	.remove		= atmel_trng_remove,
186	.driver		= {
187		.name	= "atmel-trng",
188#ifdef CONFIG_PM
189		.pm	= &atmel_trng_pm_ops,
190#endif /* CONFIG_PM */
191		.of_match_table = atmel_trng_dt_ids,
192	},
193};
194
195module_platform_driver(atmel_trng_driver);
196
197MODULE_LICENSE("GPL");
198MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>");
199MODULE_DESCRIPTION("Atmel true random number generator driver");