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_device.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 
32 struct atmel_trng_data {
33 	bool has_half_rate;
34 };
35 
36 struct atmel_trng {
37 	struct clk *clk;
38 	void __iomem *base;
39 	struct hwrng rng;
40 	bool has_half_rate;
41 };
42 
43 static 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 
55 static 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 
81 out:
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 
87 static 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 
109 static 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 
115 static 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 
164 static int 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 	return 0;
173 }
174 
175 static int __maybe_unused atmel_trng_runtime_suspend(struct device *dev)
176 {
177 	struct atmel_trng *trng = dev_get_drvdata(dev);
178 
179 	atmel_trng_cleanup(trng);
180 
181 	return 0;
182 }
183 
184 static int __maybe_unused atmel_trng_runtime_resume(struct device *dev)
185 {
186 	struct atmel_trng *trng = dev_get_drvdata(dev);
187 
188 	return atmel_trng_init(trng);
189 }
190 
191 static const struct dev_pm_ops __maybe_unused atmel_trng_pm_ops = {
192 	SET_RUNTIME_PM_OPS(atmel_trng_runtime_suspend,
193 			   atmel_trng_runtime_resume, NULL)
194 	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
195 				pm_runtime_force_resume)
196 };
197 
198 static const struct atmel_trng_data at91sam9g45_config = {
199 	.has_half_rate = false,
200 };
201 
202 static const struct atmel_trng_data sam9x60_config = {
203 	.has_half_rate = true,
204 };
205 
206 static const struct of_device_id atmel_trng_dt_ids[] = {
207 	{
208 		.compatible = "atmel,at91sam9g45-trng",
209 		.data = &at91sam9g45_config,
210 	}, {
211 		.compatible = "microchip,sam9x60-trng",
212 		.data = &sam9x60_config,
213 	}, {
214 		/* sentinel */
215 	}
216 };
217 MODULE_DEVICE_TABLE(of, atmel_trng_dt_ids);
218 
219 static struct platform_driver atmel_trng_driver = {
220 	.probe		= atmel_trng_probe,
221 	.remove		= atmel_trng_remove,
222 	.driver		= {
223 		.name	= "atmel-trng",
224 		.pm	= pm_ptr(&atmel_trng_pm_ops),
225 		.of_match_table = atmel_trng_dt_ids,
226 	},
227 };
228 
229 module_platform_driver(atmel_trng_driver);
230 
231 MODULE_LICENSE("GPL");
232 MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>");
233 MODULE_DESCRIPTION("Atmel true random number generator driver");
234