1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * RNG driver for Exynos TRNGs
4  *
5  * Author: Łukasz Stelmach <l.stelmach@samsung.com>
6  *
7  * Copyright 2017 (c) Samsung Electronics Software, Inc.
8  *
9  * Based on the Exynos PRNG driver drivers/crypto/exynos-rng by
10  * Krzysztof Kozłowski <krzk@kernel.org>
11  */
12 
13 #include <linux/clk.h>
14 #include <linux/crypto.h>
15 #include <linux/delay.h>
16 #include <linux/err.h>
17 #include <linux/hw_random.h>
18 #include <linux/io.h>
19 #include <linux/iopoll.h>
20 #include <linux/kernel.h>
21 #include <linux/module.h>
22 #include <linux/mod_devicetable.h>
23 #include <linux/platform_device.h>
24 #include <linux/pm_runtime.h>
25 
26 #define EXYNOS_TRNG_CLKDIV         (0x0)
27 
28 #define EXYNOS_TRNG_CTRL           (0x20)
29 #define EXYNOS_TRNG_CTRL_RNGEN     BIT(31)
30 
31 #define EXYNOS_TRNG_POST_CTRL      (0x30)
32 #define EXYNOS_TRNG_ONLINE_CTRL    (0x40)
33 #define EXYNOS_TRNG_ONLINE_STAT    (0x44)
34 #define EXYNOS_TRNG_ONLINE_MAXCHI2 (0x48)
35 #define EXYNOS_TRNG_FIFO_CTRL      (0x50)
36 #define EXYNOS_TRNG_FIFO_0         (0x80)
37 #define EXYNOS_TRNG_FIFO_1         (0x84)
38 #define EXYNOS_TRNG_FIFO_2         (0x88)
39 #define EXYNOS_TRNG_FIFO_3         (0x8c)
40 #define EXYNOS_TRNG_FIFO_4         (0x90)
41 #define EXYNOS_TRNG_FIFO_5         (0x94)
42 #define EXYNOS_TRNG_FIFO_6         (0x98)
43 #define EXYNOS_TRNG_FIFO_7         (0x9c)
44 #define EXYNOS_TRNG_FIFO_LEN       (8)
45 #define EXYNOS_TRNG_CLOCK_RATE     (500000)
46 
47 
48 struct exynos_trng_dev {
49 	struct device    *dev;
50 	void __iomem     *mem;
51 	struct clk       *clk;
52 	struct hwrng rng;
53 };
54 
55 static int exynos_trng_do_read(struct hwrng *rng, void *data, size_t max,
56 			       bool wait)
57 {
58 	struct exynos_trng_dev *trng;
59 	int val;
60 
61 	max = min_t(size_t, max, (EXYNOS_TRNG_FIFO_LEN * 4));
62 
63 	trng = (struct exynos_trng_dev *)rng->priv;
64 
65 	writel_relaxed(max * 8, trng->mem + EXYNOS_TRNG_FIFO_CTRL);
66 	val = readl_poll_timeout(trng->mem + EXYNOS_TRNG_FIFO_CTRL, val,
67 				 val == 0, 200, 1000000);
68 	if (val < 0)
69 		return val;
70 
71 	memcpy_fromio(data, trng->mem + EXYNOS_TRNG_FIFO_0, max);
72 
73 	return max;
74 }
75 
76 static int exynos_trng_init(struct hwrng *rng)
77 {
78 	struct exynos_trng_dev *trng = (struct exynos_trng_dev *)rng->priv;
79 	unsigned long sss_rate;
80 	u32 val;
81 
82 	sss_rate = clk_get_rate(trng->clk);
83 
84 	/*
85 	 * For most TRNG circuits the clock frequency of under 500 kHz
86 	 * is safe.
87 	 */
88 	val = sss_rate / (EXYNOS_TRNG_CLOCK_RATE * 2);
89 	if (val > 0x7fff) {
90 		dev_err(trng->dev, "clock divider too large: %d", val);
91 		return -ERANGE;
92 	}
93 	val = val << 1;
94 	writel_relaxed(val, trng->mem + EXYNOS_TRNG_CLKDIV);
95 
96 	/* Enable the generator. */
97 	val = EXYNOS_TRNG_CTRL_RNGEN;
98 	writel_relaxed(val, trng->mem + EXYNOS_TRNG_CTRL);
99 
100 	/*
101 	 * Disable post-processing. /dev/hwrng is supposed to deliver
102 	 * unprocessed data.
103 	 */
104 	writel_relaxed(0, trng->mem + EXYNOS_TRNG_POST_CTRL);
105 
106 	return 0;
107 }
108 
109 static int exynos_trng_probe(struct platform_device *pdev)
110 {
111 	struct exynos_trng_dev *trng;
112 	int ret = -ENOMEM;
113 
114 	trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
115 	if (!trng)
116 		return ret;
117 
118 	trng->rng.name = devm_kstrdup(&pdev->dev, dev_name(&pdev->dev),
119 				      GFP_KERNEL);
120 	if (!trng->rng.name)
121 		return ret;
122 
123 	trng->rng.init = exynos_trng_init;
124 	trng->rng.read = exynos_trng_do_read;
125 	trng->rng.priv = (unsigned long) trng;
126 
127 	platform_set_drvdata(pdev, trng);
128 	trng->dev = &pdev->dev;
129 
130 	trng->mem = devm_platform_ioremap_resource(pdev, 0);
131 	if (IS_ERR(trng->mem))
132 		return PTR_ERR(trng->mem);
133 
134 	pm_runtime_enable(&pdev->dev);
135 	ret = pm_runtime_resume_and_get(&pdev->dev);
136 	if (ret < 0) {
137 		dev_err(&pdev->dev, "Could not get runtime PM.\n");
138 		goto err_pm_get;
139 	}
140 
141 	trng->clk = devm_clk_get(&pdev->dev, "secss");
142 	if (IS_ERR(trng->clk)) {
143 		ret = PTR_ERR(trng->clk);
144 		dev_err(&pdev->dev, "Could not get clock.\n");
145 		goto err_clock;
146 	}
147 
148 	ret = clk_prepare_enable(trng->clk);
149 	if (ret) {
150 		dev_err(&pdev->dev, "Could not enable the clk.\n");
151 		goto err_clock;
152 	}
153 
154 	ret = devm_hwrng_register(&pdev->dev, &trng->rng);
155 	if (ret) {
156 		dev_err(&pdev->dev, "Could not register hwrng device.\n");
157 		goto err_register;
158 	}
159 
160 	dev_info(&pdev->dev, "Exynos True Random Number Generator.\n");
161 
162 	return 0;
163 
164 err_register:
165 	clk_disable_unprepare(trng->clk);
166 
167 err_clock:
168 	pm_runtime_put_noidle(&pdev->dev);
169 
170 err_pm_get:
171 	pm_runtime_disable(&pdev->dev);
172 
173 	return ret;
174 }
175 
176 static int exynos_trng_remove(struct platform_device *pdev)
177 {
178 	struct exynos_trng_dev *trng =  platform_get_drvdata(pdev);
179 
180 	clk_disable_unprepare(trng->clk);
181 
182 	pm_runtime_put_sync(&pdev->dev);
183 	pm_runtime_disable(&pdev->dev);
184 
185 	return 0;
186 }
187 
188 static int __maybe_unused exynos_trng_suspend(struct device *dev)
189 {
190 	pm_runtime_put_sync(dev);
191 
192 	return 0;
193 }
194 
195 static int __maybe_unused exynos_trng_resume(struct device *dev)
196 {
197 	int ret;
198 
199 	ret = pm_runtime_resume_and_get(dev);
200 	if (ret < 0) {
201 		dev_err(dev, "Could not get runtime PM.\n");
202 		return ret;
203 	}
204 
205 	return 0;
206 }
207 
208 static SIMPLE_DEV_PM_OPS(exynos_trng_pm_ops, exynos_trng_suspend,
209 			 exynos_trng_resume);
210 
211 static const struct of_device_id exynos_trng_dt_match[] = {
212 	{
213 		.compatible = "samsung,exynos5250-trng",
214 	},
215 	{ },
216 };
217 MODULE_DEVICE_TABLE(of, exynos_trng_dt_match);
218 
219 static struct platform_driver exynos_trng_driver = {
220 	.driver = {
221 		.name = "exynos-trng",
222 		.pm = &exynos_trng_pm_ops,
223 		.of_match_table = exynos_trng_dt_match,
224 	},
225 	.probe = exynos_trng_probe,
226 	.remove = exynos_trng_remove,
227 };
228 
229 module_platform_driver(exynos_trng_driver);
230 MODULE_AUTHOR("Łukasz Stelmach");
231 MODULE_DESCRIPTION("H/W TRNG driver for Exynos chips");
232 MODULE_LICENSE("GPL v2");
233