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/iopoll.h>
17#include <linux/hw_random.h>
18#include <linux/of.h>
19#include <linux/platform_device.h>
20#include <linux/pm_runtime.h>
21
22#define TRNG_CR		0x00
23#define TRNG_MR		0x04
24#define TRNG_ISR	0x1c
25#define TRNG_ISR_DATRDY	BIT(0)
26#define TRNG_ODATA	0x50
27
28#define TRNG_KEY	0x524e4700 /* RNG */
29
30#define TRNG_HALFR	BIT(0) /* generate RN every 168 cycles */
31
32struct atmel_trng_data {
33	bool has_half_rate;
34};
35
36struct atmel_trng {
37	struct clk *clk;
38	void __iomem *base;
39	struct hwrng rng;
40	bool has_half_rate;
41};
42
43static bool atmel_trng_wait_ready(struct atmel_trng *trng, bool wait)
44{
45	int ready;
46
47	ready = readl(trng->base + TRNG_ISR) & TRNG_ISR_DATRDY;
48	if (!ready && wait)
49		readl_poll_timeout(trng->base + TRNG_ISR, ready,
50				   ready & TRNG_ISR_DATRDY, 1000, 20000);
51
52	return !!ready;
53}
54
55static int atmel_trng_read(struct hwrng *rng, void *buf, size_t max,
56			   bool wait)
57{
58	struct atmel_trng *trng = container_of(rng, struct atmel_trng, rng);
59	u32 *data = buf;
60	int ret;
61
62	ret = pm_runtime_get_sync((struct device *)trng->rng.priv);
63	if (ret < 0) {
64		pm_runtime_put_sync((struct device *)trng->rng.priv);
65		return ret;
66	}
67
68	ret = atmel_trng_wait_ready(trng, wait);
69	if (!ret)
70		goto out;
71
72	*data = readl(trng->base + TRNG_ODATA);
73	/*
74	 * ensure data ready is only set again AFTER the next data word is ready
75	 * in case it got set between checking ISR and reading ODATA, so we
76	 * don't risk re-reading the same word
77	 */
78	readl(trng->base + TRNG_ISR);
79	ret = 4;
80
81out:
82	pm_runtime_mark_last_busy((struct device *)trng->rng.priv);
83	pm_runtime_put_sync_autosuspend((struct device *)trng->rng.priv);
84	return ret;
85}
86
87static int atmel_trng_init(struct atmel_trng *trng)
88{
89	unsigned long rate;
90	int ret;
91
92	ret = clk_prepare_enable(trng->clk);
93	if (ret)
94		return ret;
95
96	if (trng->has_half_rate) {
97		rate = clk_get_rate(trng->clk);
98
99		/* if peripheral clk is above 100MHz, set HALFR */
100		if (rate > 100000000)
101			writel(TRNG_HALFR, trng->base + TRNG_MR);
102	}
103
104	writel(TRNG_KEY | 1, trng->base + TRNG_CR);
105
106	return 0;
107}
108
109static void atmel_trng_cleanup(struct atmel_trng *trng)
110{
111	writel(TRNG_KEY, trng->base + TRNG_CR);
112	clk_disable_unprepare(trng->clk);
113}
114
115static int atmel_trng_probe(struct platform_device *pdev)
116{
117	struct atmel_trng *trng;
118	const struct atmel_trng_data *data;
119	int ret;
120
121	trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
122	if (!trng)
123		return -ENOMEM;
124
125	trng->base = devm_platform_ioremap_resource(pdev, 0);
126	if (IS_ERR(trng->base))
127		return PTR_ERR(trng->base);
128
129	trng->clk = devm_clk_get(&pdev->dev, NULL);
130	if (IS_ERR(trng->clk))
131		return PTR_ERR(trng->clk);
132	data = of_device_get_match_data(&pdev->dev);
133	if (!data)
134		return -ENODEV;
135
136	trng->has_half_rate = data->has_half_rate;
137	trng->rng.name = pdev->name;
138	trng->rng.read = atmel_trng_read;
139	trng->rng.priv = (unsigned long)&pdev->dev;
140	platform_set_drvdata(pdev, trng);
141
142#ifndef CONFIG_PM
143	ret = atmel_trng_init(trng);
144	if (ret)
145		return ret;
146#endif
147
148	pm_runtime_set_autosuspend_delay(&pdev->dev, 100);
149	pm_runtime_use_autosuspend(&pdev->dev);
150	pm_runtime_enable(&pdev->dev);
151
152	ret = devm_hwrng_register(&pdev->dev, &trng->rng);
153	if (ret) {
154		pm_runtime_disable(&pdev->dev);
155		pm_runtime_set_suspended(&pdev->dev);
156#ifndef CONFIG_PM
157		atmel_trng_cleanup(trng);
158#endif
159	}
160
161	return ret;
162}
163
164static void atmel_trng_remove(struct platform_device *pdev)
165{
166	struct atmel_trng *trng = platform_get_drvdata(pdev);
167
168	atmel_trng_cleanup(trng);
169	pm_runtime_disable(&pdev->dev);
170	pm_runtime_set_suspended(&pdev->dev);
171}
172
173static int __maybe_unused atmel_trng_runtime_suspend(struct device *dev)
174{
175	struct atmel_trng *trng = dev_get_drvdata(dev);
176
177	atmel_trng_cleanup(trng);
178
179	return 0;
180}
181
182static int __maybe_unused atmel_trng_runtime_resume(struct device *dev)
183{
184	struct atmel_trng *trng = dev_get_drvdata(dev);
185
186	return atmel_trng_init(trng);
187}
188
189static const struct dev_pm_ops __maybe_unused atmel_trng_pm_ops = {
190	SET_RUNTIME_PM_OPS(atmel_trng_runtime_suspend,
191			   atmel_trng_runtime_resume, NULL)
192	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
193				pm_runtime_force_resume)
194};
195
196static const struct atmel_trng_data at91sam9g45_config = {
197	.has_half_rate = false,
198};
199
200static const struct atmel_trng_data sam9x60_config = {
201	.has_half_rate = true,
202};
203
204static const struct of_device_id atmel_trng_dt_ids[] = {
205	{
206		.compatible = "atmel,at91sam9g45-trng",
207		.data = &at91sam9g45_config,
208	}, {
209		.compatible = "microchip,sam9x60-trng",
210		.data = &sam9x60_config,
211	}, {
212		/* sentinel */
213	}
214};
215MODULE_DEVICE_TABLE(of, atmel_trng_dt_ids);
216
217static struct platform_driver atmel_trng_driver = {
218	.probe		= atmel_trng_probe,
219	.remove_new	= atmel_trng_remove,
220	.driver		= {
221		.name	= "atmel-trng",
222		.pm	= pm_ptr(&atmel_trng_pm_ops),
223		.of_match_table = atmel_trng_dt_ids,
224	},
225};
226
227module_platform_driver(atmel_trng_driver);
228
229MODULE_LICENSE("GPL");
230MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>");
231MODULE_DESCRIPTION("Atmel true random number generator driver");
232