1 /*
2 * PIC32 RNG driver
3 *
4 * Joshua Henderson <joshua.henderson@microchip.com>
5 * Copyright (C) 2016 Microchip Technology Inc. All rights reserved.
6 *
7 * This program is free software; you can distribute it and/or modify it
8 * under the terms of the GNU General Public License (Version 2) as
9 * published by the Free Software Foundation.
10 *
11 * This program is distributed in the hope it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * for more details.
15 */
16
17 #include <linux/clk.h>
18 #include <linux/clkdev.h>
19 #include <linux/err.h>
20 #include <linux/hw_random.h>
21 #include <linux/io.h>
22 #include <linux/kernel.h>
23 #include <linux/module.h>
24 #include <linux/of.h>
25 #include <linux/of_device.h>
26 #include <linux/platform_device.h>
27 #include <linux/slab.h>
28
29 #define RNGCON 0x04
30 #define TRNGEN BIT(8)
31 #define PRNGEN BIT(9)
32 #define PRNGCONT BIT(10)
33 #define TRNGMOD BIT(11)
34 #define SEEDLOAD BIT(12)
35 #define RNGPOLY1 0x08
36 #define RNGPOLY2 0x0C
37 #define RNGNUMGEN1 0x10
38 #define RNGNUMGEN2 0x14
39 #define RNGSEED1 0x18
40 #define RNGSEED2 0x1C
41 #define RNGRCNT 0x20
42 #define RCNT_MASK 0x7F
43
44 struct pic32_rng {
45 void __iomem *base;
46 struct hwrng rng;
47 struct clk *clk;
48 };
49
50 /*
51 * The TRNG can generate up to 24Mbps. This is a timeout that should be safe
52 * enough given the instructions in the loop and that the TRNG may not always
53 * be at maximum rate.
54 */
55 #define RNG_TIMEOUT 500
56
pic32_rng_read(struct hwrng * rng,void * buf,size_t max,bool wait)57 static int pic32_rng_read(struct hwrng *rng, void *buf, size_t max,
58 bool wait)
59 {
60 struct pic32_rng *priv = container_of(rng, struct pic32_rng, rng);
61 u64 *data = buf;
62 u32 t;
63 unsigned int timeout = RNG_TIMEOUT;
64
65 if (max < 8)
66 return 0;
67
68 do {
69 t = readl(priv->base + RNGRCNT) & RCNT_MASK;
70 if (t == 64) {
71 /* TRNG value comes through the seed registers */
72 *data = ((u64)readl(priv->base + RNGSEED2) << 32) +
73 readl(priv->base + RNGSEED1);
74 return 8;
75 }
76 } while (wait && --timeout);
77
78 return -EIO;
79 }
80
pic32_rng_probe(struct platform_device * pdev)81 static int pic32_rng_probe(struct platform_device *pdev)
82 {
83 struct pic32_rng *priv;
84 struct resource *res;
85 u32 v;
86 int ret;
87
88 priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
89 if (!priv)
90 return -ENOMEM;
91
92 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
93 priv->base = devm_ioremap_resource(&pdev->dev, res);
94 if (IS_ERR(priv->base))
95 return PTR_ERR(priv->base);
96
97 priv->clk = devm_clk_get(&pdev->dev, NULL);
98 if (IS_ERR(priv->clk))
99 return PTR_ERR(priv->clk);
100
101 ret = clk_prepare_enable(priv->clk);
102 if (ret)
103 return ret;
104
105 /* enable TRNG in enhanced mode */
106 v = TRNGEN | TRNGMOD;
107 writel(v, priv->base + RNGCON);
108
109 priv->rng.name = pdev->name;
110 priv->rng.read = pic32_rng_read;
111
112 ret = hwrng_register(&priv->rng);
113 if (ret)
114 goto err_register;
115
116 platform_set_drvdata(pdev, priv);
117
118 return 0;
119
120 err_register:
121 clk_disable_unprepare(priv->clk);
122 return ret;
123 }
124
pic32_rng_remove(struct platform_device * pdev)125 static int pic32_rng_remove(struct platform_device *pdev)
126 {
127 struct pic32_rng *rng = platform_get_drvdata(pdev);
128
129 hwrng_unregister(&rng->rng);
130 writel(0, rng->base + RNGCON);
131 clk_disable_unprepare(rng->clk);
132 return 0;
133 }
134
135 static const struct of_device_id pic32_rng_of_match[] = {
136 { .compatible = "microchip,pic32mzda-rng", },
137 { /* sentinel */ }
138 };
139 MODULE_DEVICE_TABLE(of, pic32_rng_of_match);
140
141 static struct platform_driver pic32_rng_driver = {
142 .probe = pic32_rng_probe,
143 .remove = pic32_rng_remove,
144 .driver = {
145 .name = "pic32-rng",
146 .of_match_table = of_match_ptr(pic32_rng_of_match),
147 },
148 };
149
150 module_platform_driver(pic32_rng_driver);
151
152 MODULE_LICENSE("GPL");
153 MODULE_AUTHOR("Joshua Henderson <joshua.henderson@microchip.com>");
154 MODULE_DESCRIPTION("Microchip PIC32 RNG Driver");
155